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  • 1. Abou-Hamad, E.
    et al.
    Babaa, M. -R
    Bouhrara, M.
    Kim, Y.
    Saih, Y.
    Dennler, S.
    Mauri, F.
    Basset, J. -M
    Goze-Bac, C.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Structural properties of carbon nanotubes derived from (13)C NMR2011Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 84, nr 16, s. 165417-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a detailed experimental and theoretical study on how structural properties of carbon nanotubes can be derived from 13C NMR investigations. Magic angle spinning solid state NMR experiments have been performed on single-and multiwalled carbon nanotubes with diameters in the range from 0.7 to 100 nm and with number of walls from 1 to 90. We provide models on how diameter and the number of nanotube walls influence NMR linewidth and line position. Both models are supported by theoretical calculations. Increasing the diameter D, from the smallest investigated nanotube, which in our study corresponds to the inner nanotube of a double-walled tube to the largest studied diameter, corresponding to large multiwalled nanotubes, leads to a 23.5 ppm diamagnetic shift of the isotropic NMR line position d. We show that the isotropic line follows the relation d = 18.3/D + 102.5 ppm, where D is the diameter of the tube and NMR line position d is relative to tetramethylsilane. The relation asymptotically tends to approach the line position expected in graphene. A characteristic broadening of the line shape is observed with the increasing number of walls. This feature can be rationalized by an isotropic shift distribution originating from different diamagnetic shielding of the encapsulated nanotubes together with a heterogeneity of the samples. Based on our results, NMR is shown to be a nondestructive spectroscopic method that can be used as a complementary method to, for example, transmission electron microscopy to obtain structural information for carbon nanotubes, especially bulk samples.

  • 2. Abou-Hamad, E.
    et al.
    Kim, Y.
    Bouhrara, M.
    Saih, Y.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Luzzi, D. E.
    Goze-Bac, C.
    NMR strategies to study the local magnetic properties of carbon nanotubes2012Ingår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 407, nr 4, s. 740-742Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The local magnetic properties of the one dimensional inner space of the nanotubes are investigated using C-13 nuclear magnetic resonance spectroscopy of encapsulated fullerene molecules inside single walled carbon nanotubes. Isotope engineering and magnetically purified nanotubes have been advantageously used on our study to discriminate between the different diamagnetic and paramagnetic shifts of the resonances. Ring currents originating from the pi electrons circulating on the nanotube, are found to actively screen the applied magnetic field by -36.9 ppm. Defects and holes in the nanotube walls cancel this screening locally. What is interesting, that at high magnetic fields, the modifications of the NMR resonances of the molecules from free to encapsulated can be exploited to determine some structural characteristics of the surrounding nanotubes, never observed experimentally. (C) 2011 Elsevier B.V. All rights reserved.

  • 3.
    Abou-Hamad, Edy
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Goze-Bac, Christophe
    Université Montpellier II, France.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schmid, Michael
    Physikalisches Institut, Universität Stuttgart, Germany.
    Aznar, Robert
    Université Montpellier II, France.
    Mehring, Michael
    Physikalisches Institut, Universität Stuttgart, Germany.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Electronic properties of Cs-intercalated single-walled carbon nanotubes derived from nuclear magnetic resonance2011Ingår i: New Journal of Physics, E-ISSN 1367-2630, Vol. 13, s. 053045 (1)-(9)Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the electronic properties of Cs-intercalated singlewalled carbon nanotubes (SWNTs). A detailed analysis of the 13C and133Cs nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The ‘metallization’ of CsxC materials where x =0–0.144 is evidenced from the increased local electronic density of states (DOS) n(EF)at the Fermi level of the SWNTs as determined from spin–lattice relaxation measurements. In particular, there are two distinct electronic phases called α and β and the transition between these occurs around x = 0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x <0.05 (α-phase), whereas it reaches a plateau in the range 0.05 < x < 0.143 at high intercalation levels (β-phase). The new β-phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp2)orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(EF), corresponding to different local electronic band structures of the SWNTs.

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  • 4.
    Abou-Hamad, Edy
    et al.
    Universite Montpellier II.
    Kim, Y
    University of Pennsylvania.
    Talyzin, Alexandr
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Goze-Bac, Christophe
    Universite Montpellier II.
    Luzzi, David
    University of Pennsylvania.
    Rubio, Angelo
    University of Basque Country.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Hydrogenation of C-60 in Peapods: Physical Chemistry in Nano Vessels2009Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 20, s. 8583-8587Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydrogenation of C-60 molecules inside SWNT was achieved by direct reaction with hydrogen gas at elevated pressure and temperature. Evidence for the C-60 hydrogenation in peapods is provided by isotopic engineering with specific enrichment of encapsulated species and high resolution C-13 and H-1 NMR spectroscopy with the observation of characteristic diamagnetic and paramagnetic shifts of the NMR lines and the appearance of sp(3) carbon resonances. We estimate that approximately 78% of the C-60 molecules inside SWNTs are hydrogenated to an average degree of 14 hydrogen atoms per C-60 molecule. As a consequence, the rotational dynamics of the encapsulated C60Hx molecules is clearly hindered. Our successful hydrogenation experiments open completely new roads to understand and control confined chemical reactions at the nano scale

  • 5.
    Abou-Hamad, Edy
    et al.
    Universite Montpellier 2, France.
    Kim, Y.
    University of Pennsylvania, Philadelphia.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boesch, D.
    University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory.
    Aloni, S.
    University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory.
    Zettl, Alex
    University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory.
    Rubio, Angelo
    Universidad del Pas Vasco UPV/EHU.
    Luzzi, David E.
    University of Pennsylvania, Philadelphia.
    Goze-Bac, Christophe
    CNRS Universit Montpellier 2.
    Molecular dynamics and phase transition in one-dimensional crystal of C60 encapsulated inside single wall carbon nanotubes2009Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 3, nr 12, s. 3878-3883Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One-dimensional crystals of 25% 13C-enriched C60 encapsulated inside highly magnetically purified SWNTs were investigated by following the temperature dependence of the 13C NMR line shapes and the relaxation rates from 300 K down to 5 K. High-resolution MAS techniques reveal that 32% of the encapsulated molecules, so-called the C60α, are blocked at room temperature and 68%, labeled C60β, are shown to reversly undergo molecular reorientational dynamics. Contrary to previous NMR studies, spin−lattice relaxation time reveals a phase transition at 100 K associated with the changes in the nature of the C60β dynamics. Above the transition, the C60β exhibits continuous rotational diffusion; below the transition, C60β executes uniaxial hindered rotations most likely along the nanotubes axis and freeze out below 25 K. The associated activation energies of these two dynamical regimes are measured to be 6 times lower than in fcc-C60, suggesting a quiet smooth orientational dependence of the interaction between C60β molecules and the inner surface of the nanotubes.

  • 6.
    Andersson, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    In situ, high pressure differential thermal analysis and ionic conductance of PMMA-based gels with and without TiO2 nano-particle filler2006Ingår i: Electrochimica Acta, Vol. 51, s. 4537-Artikel i tidskrift (Refereegranskat)
  • 7.
    Annamalai, Alagappan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Muehlbacher, Inge
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Double donor Sb5+doped hematite (Fe3+) photoanodes for surface-enhanced PEC water splitting2018Ingår i: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 256Artikel i tidskrift (Övrigt vetenskapligt)
  • 8.
    Annamalai, Alagappan
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boily, Jean-Francois
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Mühlbacher, Inge
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Influence of Sb5+ as a Double Donor on Hematite (Fe3+) Photoanodes for Surface-Enhanced Photoelectrochemical Water Oxidation2018Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 19, s. 16467-16473Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To exploit the full potential of hematite (α-Fe2O3) as an efficient photoanode for water oxidation, the redox processes occurring at the Fe2O3/electrolyte interface need to be studied in greater detail. Ex situ doping is an excellent technique to introduce dopants onto the photoanode surface and to modify the photoanode/electrolyte interface. In this context, we selected antimony (Sb5+) as the ex situ dopant because it is an effective electron donor and reduces recombination effects and concurrently utilize the possibility to tuning the surface charge and wettability. In the presence of Sb5+ states in Sb-doped Fe2O3 photoanodes, as confirmed by X-ray photoelectron spectroscopy, we observed a 10-fold increase in carrier concentration (1.1 × 1020 vs 1.3 × 1019 cm–3) and decreased photoanode/electrolyte charge transfer resistance (∼990 vs ∼3700 Ω). Furthermore, a broad range of surface characterization techniques such as Fourier-transform infrared spectroscopy, ζ-potential, and contact angle measurements reveal that changes in the surface hydroxyl groups following the ex situ doping also have an effect on the water splitting capability. Theoretical calculations suggest that Sb5+ can activate multiple Fe3+ ions simultaneously, in addition to increasing the surface charge and enhancing the electron/hole transport properties. To a greater extent, the Sb5+- surface-doped determines the interfacial properties of electrochemical charge transfer, leading to an efficient water oxidation mechanism.

  • 9. Artemenko, A.
    et al.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Štenclová, P.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Segervald, Jonas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, X.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kromka, A.
    Reference XPS spectra of amino acids2021Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this report we present XPS data for five amino acids (AAs) (tryptophan, methionine, glutamine, glutamic acid, and arginine) with different side chain groups measured in solid state (powder form). The theoretically and experimentally obtained chemical structure of AAs are compared. Here, we analyse and discuss C 1 s, N 1 s, O 1s and S 2p core level binding energies, FWHMs, atomic concentrations of the functional groups in AAs. The experimentally obtained and theoretically calculated ratio of atomic concentrations are compared. The zwitterionic nature of methionine and glutamine in solid state was determined from protonated amino groups in N 1s peak and deprotonated carboxylic groups in the C 1s spectrum. The obtained XPS results for AAs well correspond with previously reported data.

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  • 10.
    Auroux, Etienne
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Andreas
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Umeå, Sweden .
    Lundberg, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Umeå, Sweden .
    Solution -based fabrication of the top electrode in light -emitting electrochemical cells2020Ingår i: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 84, artikel-id 105812Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) has demonstrated capacity for cost- and material-efficient solution-based fabrication of the active material under ambient air. In this context, it is notable that corresponding reports on a scalable solution-based fabrication of the electrodes, particularly the top electrode, are rare. We address this issue through the demonstration of a transparent LEC, which is fabricated under ambient air by sequential spray deposition of a hydrophobic conjugated-polymer:ionic-liquid blend ink as the active material and a hydrophilic poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ink as the transparent top electrode. Such an optimized LEC delivers a luminance of 360 cd/m2 at a power efficacy of 1.6 lm/W, which is on par with the performance of a corresponding LEC device equipped with a vacuum-deposited and reflective metal top electrode. This implies that the entire LEC device indeed can be fabricated with solution-based processes and deliver a good performance, which is critical if the LEC technology is going to fulfil its low-cost potential.

  • 11.
    Auroux, Etienne
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Andreas
    LunaLEC AB, Umeå, Sweden.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Umeå, Sweden.
    Zäll, Erik
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lundberg, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Umeå, Sweden.
    Evidence and Effects of Ion Transfer at Active-Material/Electrode Interfaces in Solution-Fabricated Light-Emitting Electrochemical Cells2021Ingår i: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 7, nr 8, artikel-id 2100253Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) allows for energy- and cost-efficient printing and coating fabrication of its entire device structure, including both electrodes and the single-layer active material. This attractive fabrication opportunity is enabled by the electrochemical action of mobile ions in the active material. However, a related and up to now overlooked issue is that such solution-fabricated LECs commonly comprise electrode/active-material interfaces that are open for transfer of the mobile ions, and it is herein demonstrated that a majority of the mobile anions in a common spray-coated active material can transfer into a spray-coated poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) positive electrode during LEC operation. Since it is well established that the mobile ion concentration in the active material has a profound influence on the LEC performance, this significant ion transfer is an important factor that should be considered in the design of low-cost LEC devices that deliver high performance.

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  • 12.
    Barzegar, Hamid R.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ramstedt, Madeleine
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Tai, Cheuk W.
    Malolepszy, Artur
    Stobinski, Leszek
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Simple Dip-Coating Process for the Synthesis of Small Diameter Single-Walled Carbon Nanotubes-Effect of Catalyst Composition and Catalyst Particle Size on Chirality and Diameter2012Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 116, nr 22, s. 12232-12239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on a dip-coating method to prepare catalyst particles (mixture of iron and cobalt) with a controlled diameter distribution on silicon wafer substrates by changing the solution's concentration and withdrawal velocity. The size and distribution of the prepared catalyst particles were analyzed by atomic force microscopy. Carbon nanotubes were grown by chemical vapor deposition on the substrates with the prepared catalyst particles. By decreasing the catalyst particle size to below 10 nm, the growth of carbon nanotubes can be tuned from few-walled carbon nanotubes, with homogeneous diameter, to highly pure single-walled carbon nanotubes. Analysis of the Raman radial breathing modes, using three different Raman excitation wavelengths (488, 633, and 785 nm), showed a relatively broad diameter distribution (0.8-1.4 nm) of single-walled carbon nanotubes with different chiralities. However, by changing the composition of the catalyst particles while maintaining the growth parameters, the chiralities of single-walled carbon nanotubes were reduced to mainly four different types, (12, 1), (12, 0), (8, 5), and (7, 5), accounting for about 70% of all nanotubes.

  • 13.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA.
    Gracia Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    C60/Collapsed Carbon Nanotube Hybrids: A Variant of Peapods2015Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, nr 2, s. 829-834Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine a variant of so-called carbon nanotube peapods by packing C60 molecules inside the open edge ducts of collapsed carbon nanotubes. C60 insertion is accomplished through a facile single-step solution-based process. Theoretical modeling is used to evaluate favorable low-energy structural configurations. Overfilling of the collapsed tubes allows infiltration of C60 over the full cross-section of the tubes and consequent partial or complete reinflation, yielding few-wall, large diameter cylindrical nanotubes packed with crystalline C60 solid cores.

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  • 14.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitrogen Doping Mechanism in Small Diameter Single-Walled Carbon Nanotubes: Impact on Electronic Properties and Growth Selectivity2013Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 48, s. 25805-25816Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Nitrogen doping in carbon nanostructures has attracted interest for more than a decade, and recent implementation of such structures in energy conversion systems has boosted the interest even more. Despite numerous studies, the structural conformation and stability of nitrogen functionalities in small diameter single-walled carbon nanotubes (SWNTs), and the impact of these functionalities on the electronic and mechanical properties of the SWNTs, are incomplete. Here we report a detailed study on nitrogen doping in SWNTs with diameters in the range of 0.8?1.0 nm, with well-defined chirality. We show that the introduction of nitrogen in the carbon framework significantly alters the stability of certain tubes, opening for the possibility to selectively grow nitrogen-doped SWNTs with certain chirality and diameter. At low nitrogen concentration, pyridinic functionalities are readily incorporated and the tubular structure is well pertained. At higher concentrations, pyrrolic functionalities are formed, which leads to significant structural deformation of the nanotubes and hence a stop in growth of crystalline SWNTs. Raman spectroscopy is an important tool to understand guest atom doping and electronic charge transfer in SWNTs. By correlating the influence of defined nitrogen functionalities on the electronic properties of SWNTs with different chirality, we make precise interpretation of experimental Raman data. We show that the previous interpretation of the double-resonance G?-peak in many aspects is wrong and instead can be well-correlated to the type of nitrogen doping of SWNTs originating from the p- or n-doping nature of the nitrogen incorporation. Our results are supported by experimental and theoretical data.

  • 15.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, Xueen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation2014Ingår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, s. 34-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.

  • 16.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Physics, University of California, Berkeley, California 94720, United States ‡ Department of Physics, Umeå University, SE-901 87 Umeå, Sweden § Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States ∥ Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zettl, Alex
    Department of Physics, University of California, Berkeley, California 94720, United States.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Self-assembled PCBM nanosheets: a facile route to electronic layer-on-Layer heterostructures2018Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 2, s. 1442-1447Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the self-assembly of semicrystalline [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanosheets at the interface between a hydrophobic solvent and water, and utilize this opportunity for the realization of electronically active organic/organic molecular heterostructures. The self-assembled PCBM nanosheets can feature a lateral size of >1 cm2 and be transferred from the water surface to both hydrophobic and hydrophilic surfaces using facile transfer techniques. We employ a transferred single PCBM nanosheet as the active material in a field-effect transistor (FET) and verify semiconductor function by a measured electron mobility of 1.2 × 10–2 cm2 V–1 s–1 and an on–off ratio of ∼1 × 104. We further fabricate a planar organic/organic heterostructure with the p-type organic semiconductor poly(3-hexylthiophene-2,5-diyl) as the bottom layer and the n-type PCBM nanosheet as the top layer and demonstrate ambipolar FET operation with an electron mobility of 8.7 × 10–4 cm2 V–1 s–1 and a hole mobility of 3.1 × 10–4 cm2V–1 s–1.

  • 17.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices2013Ingår i: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, nr 8, s. 715-720Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A modified liquid-liquid interface precipitation synthesis of C-60 nanorods, effects and opportunities following an in situ photochemical transformation in the liquid state, and an electronic characterization using a field-effect transistor (FET) geometry are reported. The nanorods feature a high aspect ratio of approximate to 10(3) and a notably small average diameter of 172 nm. Interestingly, it is found that a decreased nanorod diameter appears to correlate with distinctly improved electronic properties, and an average electron mobility of 0.30 cm(2) V-1 s(-1), as measured in a FET geometry, is reported for as-grown nanorods, with the peak value being an impressive 1.0 cm(2) V-1 s(-1). A photoexposure using green laser light ( = 532 nm) is demonstrated to result in the formation of a polymer-C-60 shell encapsulating a monomer-C-60 bulk; such photo-transformed nanorods exhibit an electron mobility of 4.7 x 10(-3) cm(2) V-1 s(-1). It is notable that the utilized FET geometry only probes the polymer-C-60 nanorod surface shell, and that the monomer-C-60 bulk is anticipated to exhibit a higher mobility. Importantly, photoexposed nanorods can be conveniently processed as a stabile dispersion in common hydrophobic solvents, and this finding is attributed to the insoluble character of the polymer-C-60 shell.

  • 18.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Nitze, Florian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Malolepszy, Artur
    Stobinski, Leszek
    Tai, Cheuk-Wai
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Water assisted growth of C60 rods and tubes by liquid-liquid interfacial precipitation method2012Ingår i: Molecules, ISSN 1431-5157, E-ISSN 1420-3049, Vol. 17, nr 6, s. 6840-6853Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    C60 nanorods with hexagonal cross sections are grown using a static liquid-liquid interfacial precipitation method in a system of C60/m-dichlorobenzene solution and ethanol. Adding water to the ethanol phase leads instead to C60 tubes where both length and diameter of the C60 tubes can be controlled by the water content in the ethanol. Based on our observations we find that the diameter of the rods/tubes strongly depends on the nucleation step. We propose a liquid-liquid interface growth model of C60 rods and tubes based on the diffusion rate of the good C60 containing solvent into the poor solvent as well as on the size of the crystal seeds formed at the interface between the two solvents. The grown rods and tubes exhibit a hexagonal solvate crystal structure with m-dichlorobenzene solvent molecules incorporated into the crystal structure, independent of the water content. An annealing step at 200 °C at a pressure <1 kPa transforms the grown structures into a solvent-free face centered cubic structure. Both the hexagonal and the face centered cubic structures are very stable and neither morphology nor structure shows any signs of degradation after three months of storage.

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  • 19.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA; Lawrence Berkeley Natl Lab, Div Mat Sci, Berkeley, CA 94720 USA; Univ Calif Berkeley, Kavli Energy NanoSci Inst, Berkeley, CA 94720 USA; Lawrence Berkeley Natl Lab, Berkeley, CA 94720 USA.
    Yan, Aiming
    Coh, Sinisa
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Dunn, Gabriel
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Louie, Steven G.
    Cohen, Marvin L.
    Zettl, Alex
    Electrostatically Driven Nanoballoon Actuator2016Ingår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 16, nr 11, s. 6787-6791Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.

  • 20.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Physics, University of California, Berkeley, CA 94720, USA; Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
    Yan, Aiming
    Coh, Sinisa
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ojeda-Aristizabal, Claudia
    Dunn, Gabriel
    Cohen, Marvin L.
    Louie, Steven G.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zettl, Alex
    Spontaneous twisting of a collapsed carbon nanotube2017Ingår i: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 10, nr 6, s. 1942-1949Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We study the collapsing and subsequent spontaneous twisting of a carbon nanotube by in situ transmission electron microscopy (TEM). A custom-sized nanotube is first created in the microscope by selectively extracting shells from a parent multi-walled tube. The few-walled, large-diameter daughter nanotube is driven to collapse via mechanical stimulation, after which the ribbon-like collapsed tube spontaneously twists along its long axis. In situ diffraction experiments fully characterize the uncollapsed and collapsed tubes. The experimental observations and associated theoretical analysis indicate that the origin of the twisting is compressive strain.

  • 21.
    Bi, Zenghui
    et al.
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Wang, Yuwen
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Chen, Jianbing
    Research Academy of Non-metallic Mining Industry Development, Materials and Environmental Engineering College, Chizhou University, Chizhou, China.
    Zhang, Xianxi
    School of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng, China.
    Zhou, Shuxing
    Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China.
    Wang, Xinzhong
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Materials and Energy, Yunnan University, Kunming, China.
    Three dimensional star-like mesoporous nitrogen-doped carbon anchored with highly dispersed Fe and Ce dual-sites for efficient oxygen reduction reaction in Zn-air battery2022Ingår i: Colloid and Interface Science Communications, ISSN 2215-0382, Vol. 49, artikel-id 100634Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal‑nitrogen‑carbon materials (M-N-C) have attracted much attention due to their low cost, high abundance, and efficient catalytic performance. Nevertheless, Fe-N-C materials are considered the most promising oxygen reduction reaction (ORR) catalysts for replacing noble metals. Ce is chemically active and has many metal valence states, and empty orbitals that can participate in coordination. On this basis, Fe, Ce-codoped catalyst was constructed in this study. The synergistic effect of the dual metal centers was verified, and a Fe, Ce-codoped nitrogen-doped carbon (FeCeNC) with six equal branch angles was proposed. The half-wave potential for the ORR catalyzed by FeCeNC is 0.855 V. As a rechargeable Zn-air battery cathode catalyst, FeCeNC exhibits excellent electrochemical performances, with an open-circuit voltage of 1.427 V, a maximum power density of 169.2 mW cm−2 and a stable cycling time of 80 h, demonstrating an excellent cycle performance.

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  • 22.
    Bi, Zenghui
    et al.
    School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhang, Hua
    School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhao, Xue
    School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wang, Yuwen
    School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Tan, Fang
    School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Chen, Songqing
    School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, China.
    Feng, Ligang
    School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, China.
    Zhou, Yingtang
    National Engineering Research Center for Marine Aquaculture, Marine Science and Technology College, Zhejiang Ocean University, Zhoushan, China.
    Ma, Xin
    School of Energy and Chemical Engineering, Xinjiang Institute of Technology, Akesu, China.
    Su, Zhi
    School of Energy and Chemical Engineering, Xinjiang Institute of Technology, Akesu, China.
    Wang, Xinzhong
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. School of Materials and Energy, Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Highly dispersed La−O/N−C sites anchored in hierarchically porous nitrogen-doped carbon as bifunctional catalysts for high-performance rechargeable Zn−air batteries2023Ingår i: Energy Storage Materials, ISSN 2405-8289, E-ISSN 2405-8297, Vol. 54, s. 313-322Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Inexpensive, high-activity bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are imperative for the development of energy storage and conversion systems. A nitrogen-doped carbon material with a micro−meso−macroporous structure doped with La (LaPNC) containing La−O/N−C active sites is prepared using SiO2 particle templating of carbon and a metal node exchange strategy. The coordination environment of La sites stabilized by two oxygen and four nitrogen atoms (LaO2N4), is further verified by X-ray absorption spectroscopy. The ORR half-wave potential reaches 0.852 V, and the OER overpotential reaches 263 mV at 10 mA cm−2. The Zn−air battery, with LaPNC as the air cathode, has a maximum power density of 202 mW cm−2 and achieves stable charge−discharge for at least 100 h without a significant increase or decrease in the charge or discharge voltages, respectively. Density functional theory calculations suggest that LaO2N4 sites exhibit the lowest activation free energy and the most easily desorbed oxygen capacity. This study provides new insights into the design of efficient, durable bifunctional catalysts as alternatives to precious-metal-based catalysts.

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  • 23. Bouhrara, M.
    et al.
    Abou-Hamad, E.
    Alabedi, G.
    Al-Taie, I.
    Kim, Y.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Goze-Bac, C.
    Electromagnetic Properties of Inner Double Walled Carbon Nanotubes Investigated by Nuclear Magnetic Resonance2013Ingår i: Journal of Nanomaterials, ISSN 1687-4110, E-ISSN 1687-4129, Vol. 2013, s. 713475-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The nuclear magnetic resonance (NMR) analytical technique was used to investigate the double walled carbon nanotubes (DWNTs) electromagnetic properties of inner walls. The local magnetic and electronic properties of inner nanotubes in DWNTs were analyzed using 25% (13) C enriched C-60 by which the effect of dipolar coupling could be minimized. The diamagnetic shielding was determined due to the ring currents on outer nanotubes in DWNTs. The NMR chemical shift anisotropy (CSA) spectra and spin-lattice relaxation studies reveal the metallic properties of the inner nanotubes with a signature of the spin-gap opening below 70 K.

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    Electromagnetic Properties of Inner Double Walled Carbon Nanotubes Investigated by Nuclear Magnetic Resonance
  • 24. Bouhrara, M.
    et al.
    Saih, Y.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Goze-Bac, C.
    Abou-Hamad, E.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    High-resolution (13)C nuclear magnetic resonance evidence of phase transition of Rb,Cs-intercalated single-walled nanotubes2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, nr 5, s. 054306-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present 13 C high-resolution magic-angle-turning (MAT) and magic angle spinning nuclear magnetic resonance data of Cs and Rb intercalated single walled carbon nanotubes. We find two distinct phases at different intercalation levels. A simple charge transfer is applicable at low intercalation level. The new phase at high intercalation level is accompanied by a hybridization of alkali (s) orbitals with the carbon (sp2) orbitals of the single walled nanotubes, which indicate bundle surface sites is the most probable alkali site.

  • 25. Buga, Sergei G.
    et al.
    Blank, Vladimir D.
    Dubitsky, Gennadii A.
    Serebryanaya, Nadejda R.
    Fransson, Åke
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Tillämpad fysik och elektronik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Synthesis of superhard 3D-polymeric C60 fullerites from rhombohedral 2D-polymer by high-pressure-high-temperature treatment.2003Ingår i: High Pressure Research vol. 23, issue 3: Proceedings of the 40th European High Pressure Research Group Meeting on Advances in High Pressure Research (EHPRG'40), London: Taylor & Francis , 2003, s. 259-264Konferensbidrag (Refereegranskat)
    Abstract [en]

    Rhombohedral C60 polymer was subjected to high-pressure-high-temperature treatment at P =13 GPa, T =620-1620 K. After quenching, crystalline and disordered structures with densities in the range of 2.1-2.9 g cm-1 were obtained. The structures of the samples have been investigated by powder X-ray diffraction and Raman scattering. DSC analysis showed a transformation of the polymeric structure into monomeric on annealing in the range 400-640 K. The temperature dependence of the electrical resistance of samples with disordered structure was measured in the range 2.5-300K. For different samples, the conductivity was proportional to T1/2, T3/2, T4 and exp(-1/T1/4).

  • 26.
    Ding, Pengjia
    et al.
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Niu, Jianrui
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Chang, Fengqin
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    He, Zhuang
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Li, Zaixing
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Hu, Guangzhi
    College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China; Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    NiCo2O4 hollow microsphere–mediated ultrafast peroxymonosulfate activation for dye degradation2021Ingår i: Chinese Chemical Letters, ISSN 1001-8417, E-ISSN 1878-5964, Vol. 32, nr 8, s. 2495-2498Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Morphology and dispersity are key factors for activating peroxymonosulfate (PMS). In this study, we designed a recyclable open-type NiCo2O4 hollow microsphere via a simple hydrothermal method with the assistance of an NH3 vesicle. The physical structure and chemical properties were characterized using techniques such as scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), N2 adsorption and X-ray photoelectron spectroscopy (XPS). The test results confirm that the inner and outer surfaces of open-type NiCo2O4 hollow-sphere can be efficiently utilized because of the hole on the surface of the catalyst, which can minimize the diffusion resistance of the reactants and products. Under optimized conditions, the total organic carbon (TOC) removal efficiency of rhodamine B (RhB) can reach up to 80% in 40 min, which is almost 50% shorter than the reported values. The reactive radicals were identified and the proposed reaction mechanism was well described. Moreover, the disturbances of HCO3, NO3, Cl and H2PO4 were further investigated. As a result, HCO3 and NO3 suppressed the reaction while Cl and H2PO4 had a double effect on reaction.

  • 27.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Moons, Ellen
    Karlstad universitet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Facile fabrication of organic CMOS circuits: understanding and optimization of the processManuskript (Övrigt vetenskapligt)
  • 28.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    C60 Field-Effect Transistors: Effects of Polymerization on Electronic Properties and Device Performance.2007Ingår i: Extended abstracts – 9th European Conference on Molecular Electronics, 2007Konferensbidrag (Övrigt vetenskapligt)
  • 29.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    C60 Field-Effect Transistors: Effects of Polymerization on electronic Properties and Device Performance.2007Ingår i: Physical Review B, Vol. 75, nr 7, s. 075203-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have investigated thin-film field-effect transistors (TFTs) with C60 as the active material, and we report the effects of photo-induced polymerization of the C60 film. We find that the effects of a complete polymerization for a typical top-contact C60 TFT is as follows: the electron mobility (μn) at room temperature drops slightly from 0.074 to 0.068 cm2/Vs, the activation energy of μn decreases from 0.10 meV to 0.09 meV, and the threshold voltage for TFT operation decreases markedly by ~15 %. The latter observation suggests that the effective number of electron traps in the C60 film decreases following polymerization. Considering that the polymerization was achieved with a low-energy HeNe laser, it is conceivable that the polymerization approach could be of interest for applications, e.g., organic bulk-heterojunction solar cells, where a stabilized C60 morphology attained with benign means is desired

  • 30.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Photo-induced and resist-free imprint patterning of fullerene materials for use in functional electronics2009Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, nr 11, s. 4006-4011Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a novel and potentially generic method for the efficient patterning of films of organic semiconductors and demonstrate the merit of the method on the high-solubility fullerene [6,6]-phenyl C61- butyric acid methyl ester (PCBM). The patterning technique is notably straightforward as it requires no photoresist material and encompasses only two steps: (i) exposure of select film areas to visible laser light during which the PCBM mononer is photochemically converted into a dimeric state, and (ii) development via solvent washing after which the nonexposed portions of the PCBM film are selectively removed. Importantly, the method is highly benign in that it leaves the electronic properties of the remaining patterned material intact, which is directly evidenced by the fact that we fabricate fully functional arrays of micrometersized field-effect transistors with patterned PCBM as the active material.

  • 31.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Andersson, Mats
    Light-emitting Electrochemical Cells with mm-sized Electrode Gap: Controlling Light at Low Voltage and Identification of Degradation Mechanism.2008Ingår i: SPIE Photonics Europe, 2008Konferensbidrag (Övrigt vetenskapligt)
  • 32.
    Ekeroth, Sebastian
    et al.
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Ekspong, Joakim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Perivoliotis, Dimitrios K.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharma, Sachin
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Boyd, Robert
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Brenning, Nils
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden; Division of Space and Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, Stockholm, Sweden.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Helmersson, Ulf
    Department of Physics, Chemistry and Biology, Linköping University, Linköping, Sweden.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Magnetically Collected Platinum/Nickel Alloy Nanoparticles as Catalysts for Hydrogen Evolution2021Ingår i: ACS Applied Nano Materials, E-ISSN 2574-0970, Vol. 4, nr 12, s. 12957-12965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hydrogen evolution reaction (HER) is a key process in electrochemical water splitting. To lower the cost and environmental impact of this process, it is highly motivated to develop electrocatalysts with low or no content of noble metals. Here, we report on an ingenious synthesis of hybrid PtxNi1-x electrocatalysts in the form of a nanoparticle-nanonetwork structure with very low noble metal content. The structure possesses important features such as good electrical conductivity, high surface area, strong interlinking, and substrate adhesion, which render an excellent HER activity. Specifically, the best performing Pt0.05Ni0.95 sample demonstrates a Tafel slope of 30 mV dec-1 in 0.5 M H2SO4 and an overpotential of 20 mV at a current density of 10 mA cm-2 with high stability. The impressive catalytic performance is further rationalized in a theoretical study, which provides insight into the mechanism on how such small platinum content can allow for close-to-optimal adsorption energies for hydrogen.

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  • 33. Ekeroth, Sebastian
    et al.
    Münger, E. Peter
    Boyd, Robert
    Ekspong, Joakim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brenning, Nils
    Helmersson, Ulf
    Catalytic nanotruss structures realized by magnetic self-assembly in pulsed plasma2018Ingår i: Nano Letters, ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 5, s. 3132-3137Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 μm thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H2 gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm2.

  • 34.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hydrogen Evolution Reaction Activity of Heterogeneous Materials: A Theoretical Model2020Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, nr 38, s. 20911-20921Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we present a new comprehensive methodology to quantify the catalytic activity of heterogeneous materials for the hydrogen evolution reaction (HER) using ab initio simulations. The model is composed of two parts. First, the equilibrium hydrogen coverage is obtained by an iterative evaluation of the hydrogen adsorption free energies (ΔGH) using density functional theory calculations. Afterward, the ΔGH are used in a microkinetic model to provide detailed characterizations of the entire HER considering all three elementary steps, i.e., the discharge, atom + ion, and combination reactions, without any prior assumptions of rate-determining steps. The microkinetic model takes the equilibrium and potential-dependent characteristics into account, and thus both exchange current densities and Tafel slopes are evaluated. The model is tested on several systems, from polycrystalline metals to heterogeneous molybdenum disulfide (MoS2), and by comparing to experimental data, we verify that our model accurately predicts their experimental exchange current densities and Tafel slopes. Finally, we present an extended volcano plot that correlates the electrical current densities of each elementary reaction step to the coverage-dependent ΔGH.

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  • 35.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stenberg, Jonas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kwong, Wai Ling
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Wang, Jia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhang, Jinbao
    Johansson, Erik M.J.
    Messinger, Johannes
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Solar-driven water splitting at 13.8 % solar-to-hydrogen efficiency by an earth-abundant PV-electrolyzer2021Ingår i: ACS Sustainable Chemistry and Engineering, E-ISSN 2168-0485, Vol. 9, nr 42, s. 14070-14078Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the synthesis and characterization of an efficient and low cost solar-driven electrolyzer consisting of Earth-abundant materials. The trimetallic NiFeMo electrocatalyst takes the shape of nanometer-sized flakes anchored to a fully carbon-based current collector comprising a nitrogen-doped carbon nanotube network, which in turn is grown on a carbon fiber paper support. This catalyst electrode contains solely Earth-abundant materials, and the carbon fiber support renders it effective despite a low metal content. Notably, a bifunctional catalyst–electrode pair exhibits a low total overpotential of 450 mV to drive a full water-splitting reaction at a current density of 10 mA cm–2 and a measured hydrogen Faradaic efficiency of ∼100%. We combine the catalyst–electrode pair with solution-processed perovskite solar cells to form a lightweight solar-driven water-splitting device with a high peak solar-to-fuel conversion efficiency of 13.8%.

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  • 36.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Robin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rajukumar, Lakshmy Pulickal
    Terrones, Mauricio
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stable Sulfur‐Intercalated 1T′ MoS2 on Graphitic Nanoribbons as Hydrogen Evolution Electrocatalyst2018Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, nr 46, artikel-id 1802744Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The metastable 1T′ polymorph of molybdenum disulfide (MoS2) has shown excellent catalytic activity toward the hydrogen evolution reaction (HER) in water‐splitting applications. Its basal plane exhibits high catalytic activity comparable to the edges in 2H MoS2 and noble metal platinum. However, the production and application of this polymorph are limited by its lower energetic stability compared to the semiconducting 2H MoS2 phase. Here, the production of stable intercalated 1T′ MoS2 nanosheets attached on graphitic nanoribbons is reported. The intercalated 1T′ MoS2 exhibits a stoichiometric S:Mo ratio of 2.3 (±0.1):1 with an expanded interlayer distance of 10 Å caused by a sulfur‐rich intercalation agent and is stable at room temperature for several months even after drying. The composition, structure, and catalytic activity toward HER are investigated both experimentally and theoretically. It is concluded that the 1T′ MoS2 phase is stabilized by the intercalated agents, which further improves the basal planes′ catalytic activity toward HER.

  • 37.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Klechikov, Alexey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stabilizing Active Edge Sites in Semicrystalline Molybdenum Sulfide by Anchorage on Nitrogen-Doped Carbon Nanotubes for Hydrogen Evolution Reaction2016Ingår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 26, nr 37, s. 6766-6776Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finding an abundant and cost-effective electrocatalyst for the hydrogen evolu-tion reaction (HER) is crucial for a global production of hydrogen from water electrolysis. This work reports an exceptionally large surface area hybrid catalyst electrode comprising semicrystalline molybdenum sulfi de (MoS 2+ x) catalystattached on a substrate based on nitrogen-doped carbon nanotubes (N-CNTs), which are directly grown on carbon fiber paper (CP). It is shown here that nitrogen-doping of the carbon nanotubes improves the anchoring of MoS 2+ xcatalyst compared to undoped carbon nanotubes and concurrently stabilizes a semicrystalline structure of MoS 2+ x with a high exposure of active sites for HER. The well-connected constituents of the hybrid catalyst are shown to facilitate electron transport and as a result of the good attributes, the MoS 2+ x/N-CNT/CPelectrode exhibits an onset potential of −135 mV for HER in 0.5 M H2SO4, a Tafel slope of 36 mV dec −1, and high stability at a current density of −10 mA cm −2.

  • 38.
    Ekspong, Joakim
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stainless Steel as A Bi-Functional Electrocatalyst – A Top-Down Approach2019Ingår i: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, nr 13, artikel-id 2128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For a hydrogen economy to be viable, clean and economical hydrogen production methods are vital. Electrolysis of water is a promising hydrogen production technique with zero emissions, but suffer from relatively high production costs. In order to make electrolysis of water sustainable, abundant, and efficient materials has to replace expensive and scarce noble metals as electrocatalysts in the reaction cells. Herein, we study activated stainless steel as a bi-functional electrocatalyst for the full water splitting reaction by taking advantage of nickel and iron suppressed within the bulk. The final electrocatalyst consists of a stainless steel mesh with a modified surface of layered NiFe nanosheets. By using a top down approach, the nanosheets stay well anchored to the surface and maintain an excellent electrical connection to the bulk structure. At ambient temperature, the activated stainless steel electrodes produce 10 mA/cm(2) at a cell voltage of 1.78 V and display an onset for water splitting at 1.68 V in 1M KOH, which is close to benchmarking nanosized catalysts. Furthermore, we use a scalable activation method using no externally added electrocatalyst, which could be a practical and cheap alternative to traditionally catalyst-coated electrodes.

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  • 39.
    Eriksson, Axl
    et al.
    Chemical Physics, Department of Chemistry, Lund University, Kemicentrum Naturvetarevägen 16, Lund, Sweden; NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Kawde, Anurag
    Chemical Physics, Department of Chemistry, Lund University, Kemicentrum Naturvetarevägen 16, Lund, Sweden; Lund Institute of Advanced Neutron and X-ray Science, Lund University, Scheelevägen 19, Lund, Sweden; NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Hrachowina, Lukas
    NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden; Solid State Physics, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    McKibbin, Sarah R.
    NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden; Solid State Physics, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Shi, Qi
    Chemical Physics, Department of Chemistry, Lund University, Kemicentrum Naturvetarevägen 16, Lund, Sweden; NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Borgström, Magnus T.
    NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden; Solid State Physics, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Pullerits, Tönu
    Chemical Physics, Department of Chemistry, Lund University, Kemicentrum Naturvetarevägen 16, Lund, Sweden; NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Uhlig, Jens
    Chemical Physics, Department of Chemistry, Lund University, Kemicentrum Naturvetarevägen 16, Lund, Sweden; Lund Institute of Advanced Neutron and X-ray Science, Lund University, Scheelevägen 19, Lund, Sweden; NanoLund, Department of Physics, Lund University, Professorsgatan 1, Lund, Sweden.
    Synthesis of well-ordered functionalized silicon microwires using displacement talbot lithography for photocatalysis2024Ingår i: ACS Omega, E-ISSN 2470-1343, Vol. 9, nr 18, s. 20623-20628Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Metal-assisted chemical etching (MACE) is a cheap and scalable method that is commonly used to obtain silicon nano- or microwires but lacks spatial control. Herein, we present a synthesis method for producing vertical and highly periodic silicon microwires, using displacement Talbot lithography before wet etching with MACE. The functionalized periodic silicon microwires show 65% higher PEC performance and 2.3 mA/cm2 higher net photocurrent at 0 V compared to functionalized, randomly distributed microwires obtained by conventional MACE at the same potentials.

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  • 40. Gao, Sanshuang
    et al.
    Liu, Jing
    Luo, Jun
    Mamat, Xamxikamar
    Sambasivam, Sangaraju
    Li, Yongtao
    Hu, Xun
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Key Laboratory of Chemistry of Plant Resources in Arid Regions, State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi, China.
    Selective voltammetric determination of Cd(II) by using N,S-codoped porous carbon nanofibers2018Ingår i: Microchimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 185, artikel-id 282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Porous carbon nanofibers codoped with nitrogen and sulfur (NFs) were prepared by pyrolysis of trithiocyanuric acid, silica nanospheres and polyacrylonitrile (PAN) followed by electrospinning. The NFs were used to modify a glassy carbon electrode (GCE) which then displayed highly sensitive response to traces of Cd(II). Compared to a bare GCE and a Nafion modified GCE, the GCE modified with codoped NFs shows improved sensitivity for Cd(II) in differential pulse anodic sweep voltammetry. The stripping peak current (typically measured at 0.81 V vs. Ag/AgCl) increases linearly in the 2.0–500 μg·L−1 Cd(II) concentration range. This is attributed to the large surface area (109 m2·g−1), porous structure, and high fraction of heteroatoms (19 at.% of N and 0.75 at.% of S). The method was applied to the determination of Cd(II) in (spiked) tap water where it gave recoveries that ranged between 96% and 103%.

  • 41. Gao, Sanshuang
    et al.
    Xu, Chuyang
    Yalikun, Nuerbiya
    Mamat, Xamxikamar
    Li, Yongtao
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Xun
    Liu, Jing
    Luo, Jun
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Key Laboratory of Chemistry of Plant Resources in Arid Regions, State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Science, Urumqi 830011, People's Republic of China.
    Sensitive and Selective Differential Pulse Voltammetry Detection of Cd(II) and Pb(II) Using Nitrogen-Doped Porous Carbon Nanofiber Film Electrode2017Ingår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 13, s. H967-H974Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon matrix materials are regarded as one of the most important electrode materials for heavy metal detection. But even so, optimization procedures of carbon nanofibers (CNFs) for tracing Cd(II) and Pb(II) remains challenging. Here, zeolitic imidazolate framework (ZIF-8)/polyacrylonitrile (PAN)-derived nitrogen-doped porous carbon nanofibers (N-PCNFs) were investigated as a new electrode material for determining the concentration of Cd(II) and Pb(II). By optimizing electrochemical conditions such as deposition potential, deposition time, pH of buffer solution, and quantity of N-PCNFs loaded on a glassy carbon electrode (GCE), the linear response curves of Cd(II) and Pb(II) could be obtained. Due to the unique structural feature and N content, the N-PCNFs possess excellent detection limits of 0.8 mu g L-1 for Cd(II) and 0.3 mu g L-1 for Pb(II) (S/N = 3). To manifest the practical use of the sensor platform the concentration of Cd(II) and Pb(II) in normal tap and waste water were monitored. According to the ICP-MS results, the calculated recovery (97.0-107%) indicates that N-PCNFs have potential as a candidate material to monitor the concentration of Cd(II) and Pb(II) in practical samples.

  • 42.
    Gracia-Espino, Eduardo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Barzegar, Hamid Reza
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sharifi, Tiva
    Yan, Aiming
    Zettl, Alex
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fabrication of One-Dimensional Zigzag [6,6]-Phenyl-C-61-Butyric Acid Methyl Ester Nanoribbons from Two-Dimensional Nanosheets2015Ingår i: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 9, nr 10, s. 10516-10522Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One-dimensional (10) zigzag [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanoribbons are produced by folding two-dimensional ultrathin PCBM nanosheets in a simple solvent process. The unique 1D PCBM nanostructures exhibit uniform width of 3.8 +/- 0.3 nm, equivalent to four PCBM molecules, and lengths of 20-400 nm. These nanoribbons show well-defined crystalline structure, comprising PCBM molecules in a hexagonal arrangement without trapped solvent molecules. First-principle calculations and detailed experimental characterization provide an insight into the structure and formation mechanism of the 1D PCBM nanoribbons. Given their dimensions and physical properties, we foresee that these nanostructures should be ideal as acceptor material in organic solar cells.

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  • 43.
    Gracia-Espino, Eduardo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shchukarev, Andrey
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Understanding the Interface of Six-Shell Cuboctahedral and Icosahedral Palladium Clusters on Reduced Graphene Oxide: Experimental and Theoretical Study2014Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 18, s. 6626-6633Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Studies on noble-metal-decorated carbon nanostructures are reported almost on a daily basis, but detailed studies on the nanoscale interactions for well-defined systems are very rare. Here we report a study of reduced graphene oxide (rGOx) homogeneously decorated with palladium (Pd) nanoclusters with well-defined shape and size (2.3 +/- 0.3 nm). The rGOx was modified with benzyl mercaptan (BnSH) to improve the interaction with Pd clusters, and N,N-dimethylformamide was used as solvent and capping agent during the decoration process. The resulting Pd nanoparticles anchored to the rGOx-surface exhibit high crystallinity and are fully consistent with six-shell cuboctahedral and icosahedral clusters containing similar to 600 Pd atoms, where 45% of these are located at the surface. According to X-ray photoelectron spectroscopy analysis, the Pd clusters exhibit an oxidized surface forming a PdOx shell. Given the well-defined experimental system, as verified by electron microscopy data and theoretical simulations, we performed ab initio simulations using 10 functionalized graphenes (with vacancies or pyridine, amine, hydroxyl, carboxyl, or epoxy groups) to understand the adsorption process of BnSH, their further role in the Pd cluster formation, and the electronic properties of the graphene-nanoparticle hybrid system. Both the experimental and theoretical results suggest that Pd clusters interact with fiinctionalized graphene by a sulfur bridge while the remaining Pd surface is oxidized. Our study is of significant importance for all work related to anchoring of nanoparticles on nanocarbon-based supports, which are used in a variety of applications.

  • 44.
    Gracia-Espino, Eduardo
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, Xueen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Improved oxygen reduction performance of Pt–Ni nanoparticles by adhesion on nitrogen-doped graphene2014Ingår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, nr 5, s. 2804-2811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Graphene and its derivatives hold great potential as support for nanocatalyst in various energy applications, such as fuel cells, batteries, and capacitors. In this work, we used density functional theory to analyze substrate effect on the electrocatalytic activity of Pt–Ni bimetallic nanoparticles for oxygen reduction reaction (ORR). The dissociative mechanism is used to evaluate the ORR performance (energy barrier for O2 dissociation, free energy of intermediates, d-band center, overpotential, and electrochemical activity) for a Pt–Ni core–shell-like nanoparticle (PtNiCS) deposited on nondefective graphene (GS) or nitrogen-doped graphene (N-GS). The electronic and catalytic properties of PtNiCS on N-GS designate N-doped graphene as the best substrate to use for ORR, showing better interaction with the bimetallic cluster, improved charge transfer between constitutes, and a superior ORR performance when compared to PtNiCS on GS. The N-GS has a significant effect in reducing the energy barrier for O2 dissociation and decrease the energetic stability of HO* intermediates, resulting in enhanced ORR activity compared with the PtNiCS on GS. In addition, the strong interaction between PtNiCS cluster and N-GS substrate may lead to an improved long-term stability of the catalytic particle during ORR cycles.

  • 45. Han, Xin-Bao
    et al.
    Tang, Xing-Yan
    Lin, Yue
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Liu, San-Gui
    Liang, Hai-Wei
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Key Laboratory of Chemistry of Plant Resources in Arid Regions, State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China.
    Zhao, Xin-Jing
    Liao, Hong-Gang
    Tan, Yuan-Zhi
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Xie, Su-Yuan
    Zheng, Lan-Sun
    Ultrasmall Abundant Metal-Based Clusters as Oxygen-Evolving Catalysts2019Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 141, nr 1, s. 232-239Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxygen evolution reaction is a crucial step in water electrolysis to develop clean and renewable energy. Although noble metal-based catalysts have demonstrated high activity for the oxygen evolution reaction, their application is limited by their high cost and low availability. Here we report the use of a molecule-to-cluster strategy for preparing ultrasmall trimetallic clusters by using the polyoxometalate molecule as a precursor. Ultrafine (0.8 nm) transition-metal clusters with controllable chemical composition are obtained. The transition-metal clusters enable highly efficient oxygen evolution through water electrolysis in alkaline media, manifested by an overpotential of 192 mV at 10 mA cm–2, a low Tafel slope of 36 mV dec–1, and long-term stability for 30 h of electrolysis. We note, however, that besides the excellent performance as an oxygen evolution catalyst, our molecule-to-cluster strategy provides a means to achieve well-defined transition-metal clusters in the subnanometer regime, which potentially can have an impact on several other applications.

  • 46. Han, Xin-Bao
    et al.
    Wang, Dong-Xue
    Gracia-Espino, Eduardo
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Luo, Yu-Hui
    Tan, Yuan-Zhi
    Lu, Dong-Fei
    Li, Yang-Guang
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, En-Bo
    Zheng, Lan-Sun
    Fe-substituted cobalt-phosphate polyoxometalates as enhanced oxygen evolution catalysts in acidic media2020Ingår i: Cuihuà xuébào, ISSN 0253-9837, E-ISSN 1872-2067, Vol. 41, nr 5, s. 853-857Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    All-inorganic and earth-abundant bi-/trimetallic hydr(oxy)oxides are widely used as oxygen evolution electrocatalysts owing to their remarkable performance. However, their atomically precise structures remain undefined, complicating their optimization and limiting the understanding of their enhanced performance. Here, the underlying structure-property correlation is explored by using a well-defined cobalt-phosphate polyoxometalate cluster [{Co-4(OH)(3)(PO4)}(4)(SiW9O34)(4)](32-) (1), which may serve as a molecular model of multimetal hydr(oxy)oxides. The catalytic activity is enhanced upon replacing Co by Fe in 1, resulting in a reduced overpotential (385 mV) for oxygen evolution (by 66 mV) compared to that of the parent 1 at 10 mA cm(-2) in an acidic medium; this overpotential is comparable to that for the IrO2 catalyst. These abundant-metal-based polyoxometalates exhibit high stability, with no evidence of degradation even after 24 h of operation.

  • 47.
    Hao, Chenglin
    et al.
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Rao, Fengling
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhang, Yunqiu
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wang, Huaisheng
    School of Chemistry and Chemical Engineering, Liaocheng University, Shandong, Liaocheng, China.
    Chen, Jianbin
    Research Academy of Non-metallic Mining Industry Development, Materials and Environmental Engineering College, Chizhou University, Chizhou, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Low-temperature molten-salt synthesis of Co3O4 nanoparticles grown on MXene can rapidly remove ornidazole via peroxymonosulfate activation2023Ingår i: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 334, artikel-id 121811Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We further developed previous work on MXene materials prepared using molten salt methodology. We substituted single, with mixed salts, and reduced the melting point from >724 °C to <360 °C. Cobalt (Co) compounds were simultaneously etched and doped while the MXene material was created using various techniques in which Co compounds occur as Co3O4. The synthesized Co3O4/MXene compound was used as a peroxymonosulfate (PMS) activator that would generate free radicals to degrade antibiotic ornidazole (ONZ). Under optimal conditions, almost 100% of ONZ (30 mg/L) was degraded within 10 min. The Co3O4/MXene + PMS system efficiently degraded ONZ in natural water bodies, and had a broad pH adaptation range (4–11), and strong anion anti-interference. We investigated how the four active substances were generated using radical quenching and electron paramagnetic resonance (EPR) spectroscopy. We identified 12 ONZ intermediates by liquid chromatography-mass spectrometry and propose a plausible degradative mechanism.

  • 48.
    He, Yingnan
    et al.
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Chen, Jianbing
    Research Academy of Non-metallic Mining Industry Development, Materials and Environmental Engineering College, Chizhou University, Chizhou, China.
    Lv, Jiapei
    State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, China.
    Huang, Yimin
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhou, Shuxing
    Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China.
    Li, Wenyan
    Joint Institute for Environmental Research and Education, College of Resources and Environment, South China Agricultural University, Guangzhou, China.
    Li, Yongtao
    Joint Institute for Environmental Research and Education, College of Resources and Environment, South China Agricultural University, Guangzhou, China.
    Chang, Fengqin
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhang, Hucai
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Separable amino-functionalized biochar/alginate beads for efficient removal of Cr(VI) from original electroplating wastewater at room temperature2022Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 373, artikel-id 133790Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An alginate gel bead composite adsorbent with polyethyleneimine (PEI) as a surface modifier and Eichhornia crassipes (EC) biochar, known as EC-alg/PEI-3, was added internally to the adsorb Cr(VI) from an aqueous environment. The functionalized gel beads were characterized using SEM, XPS, FTIR, and other techniques. The maximum adsorption capacities of EC-alg/PEI-3 were 714.3 mg g−1 at 10 °C and 769.2 mg g−1 at 25 °C. In the treatment of highly concentrated electroplating wastewater, EC-alg/PEI-3 can be dosed at 1.4 g L−1 to reduce the concentration of Cr(VI) to below 0.05 ppm. EC-alg/PEI-3 maintained a competitive adsorption capacity after six cycles. This spherical adsorbent material is easy to prepare, has a very high adsorption capacity, is environmentally friendly, and can be easily recycled. The EC-alg/PEI-3 gel beads are promising for the treatment of industrial wastewater.

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  • 49.
    He, Yingnan
    et al.
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Jia, Xiuxiu
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Zhou, Shuxing
    Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China.
    Chen, Jianbing
    Research Academy of Non-metallic Mining Industry Development, Materials and Environmental Engineering College, Chizhou University, Chizhou, China.
    Zhang, Shusheng
    College of Chemistry, Zhengzhou University, Zhengzhou, China.
    Li, Xiaohua
    Rural Energy & Environment Agency, Ministry of Agriculture and Rural Affairs, Beijing, China.
    Huang, Yimin
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Separatable MoS2 loaded biochar/CaCO3/Alginate gel beads for selective and efficient removal of Pb(II) from aqueous solution2022Ingår i: Separation and Purification Technology, ISSN 1383-5866, E-ISSN 1873-3794, Vol. 303, artikel-id 122212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Centimeter-scale composite biochar-alginate gel beads (MoS2B/CaCO3/Alg) were designed for the adsorption of Pb(II) in water using MoS2 modified biochar as the filler, alginate as the matrix, and CaCO3 as the active additive component. The composite gel beads were characterized using scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and other techniques. MoS2B/CaCO3/Alg showed excellent adsorption capacity over a wide range of pH 4–7. The maximum adsorption capacities obtained using the Langmuir model were 769.2, 833.3, and 909.1 mg g−1 at 10, 25 and 40 °C, respectively. At a dosing rate of 0.4 g L−1, MoS2B/CaCO3/Alg was able to reduce the Pb(II) concentration to below 0.05 ppm in complex simulated lead battery wastewater. After 10 repeated cycles, MoS2B/CaCO3/Alg maintained a high removal rate of 98.4 %. This spherical adsorbent is simple to prepare and easy to recover, has an ultra-high adsorption capacity, and is mechanically stable and resistant to interference, thus it is expected to be suitable for application in industrial wastewater treatment.

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  • 50.
    He, Zhuang
    et al.
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China; School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Zhang, Yunqiu
    Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Lv, Jiapei
    State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, China.
    Zhou, Shuxing
    Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang, China.
    Niu, Jianrui
    School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Li, Zaixing
    School of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang, China.
    Wang, Xinzhong
    School of Electronic Communication Technology, Shenzhen Institute of Information Technology, Shenzhen, China.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming, China.
    Microwave-assisted synthesis of amorphous cobalt nanoparticle decorated N-doped biochar for highly efficient degradation of sulfamethazine via peroxymonosulfate activation2022Ingår i: Journal of Water Process Engineering, E-ISSN 2214-7144, Vol. 50, artikel-id 103226Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, a microwave-assisted and secondary roasting preparation process was used to synthesize nanocomposite materials. These materials were modified with amorphous cobalt nanoparticles (Co NPs) on the surface of biochar doped with different nitrogen sources (melamine (Me), 1,10-phenanthroline (Ph), and urea (Ur)). The nanocomposite (Co-N-C(Ur)) with urea as the nitrogen source promoted the generation of mesopores on the surface of carbon materials due to its evaporation during the preparation process thus enhancing the attachment sites of cobalt nanoparticles. The Co-N-C(Ur) had a more significant degradation effect on the primary carcinogen sulfamethazine (SMT) by activating peroxymonosulfate (PMS). The degradation rate of SMT pollutants was 96.6 % within 30 min. The optimal reaction conditions were as follows: catalyst dosage of 0.4 g L−1, PMS dosage of 0.812 mM, SMT concentration of 10 mg L−1, and pH of 5.67. Additionally, the Co-N-C(Ur) catalysts possess excellent specific surface area due to the evaporation effect of the calcination process of urea itself compared to other nitrogen source doping. Electrochemical tests revealed that the composites prepared with urea as the nitrogen source had higher PMS-induced current density and lowered material impedance values, which effectively promoted the catalytic performance of SMT degradation. Concurrently, the Co-N-C (Ur) + PMS reaction system exhibited excellent catalytic performance against other antibiotic organic pollutants. Subsequently, through the capture experiments and electron paramagnetic resonance technical analyses, it was determined that the singlet 1O2 played a leading role in the reaction system. Finally, a thorough liquid chromatography-mass spectrometry analysis suggested the possible SMT degradation pathways, thereby providing a new strategy for the subsequent heterogeneous catalysts to degrade persistent organic pollutants.

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