Transition metal doped Sb@SnO2 nanoparticles for photochemical and electrochemical oxidation of cysteine.
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ABSTRACT:
SUBMITTER: Kim Y
PROVIDER: S-EPMC6098097 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt-nickel-iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm(-2), small Tafel slope of 37.6 mV dec(-1), and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications.
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Project description:Highlights • The main properties of coordinated magnetic nanoparticles (MNPs) including magnetic moment and saturated magnetisation).• The doping of transition metal ions into ferrite to precisely modulate its magnetic properties.• the potential mechanisms and recent advances in transition metal ion-doped MNPs (TMNPs) for bioimaging: magnetic resonance imaging and magnetic particle imaging and tumour therapy: e.g., magneto-mechanical killing, magnetothermal therapy, and drug delivery.• the current challenges and future trends of TMNPs in the biomedical field based on the latest advances by researchers. Magnetic nanoparticles (MNPs) have been extensively researched and implemented in biomedicine for more than half a century due to their non-invasive nature, ease of temporal and spatial manipulation, and considerable biocompatibility. However, the complex magnetic behaviour of MNPs is influenced by several parameters (e.g., particle size, shape, composition, core-shell structure, etc.), among which the amount of transition metal doping plays an important factor. For this reason, the doping of ferrite with transition metals has been used as an effective strategy to precisely tailor MNPs to achieve satisfactory performance in biomedical applications. In this review, we first introduced the main properties of coordinated MNPs (including magnetic moment and saturated magnetisation) and provide a comprehensive overview of the mechanistic studies related to the doping of transition metal ions into ferrite to precisely modulate its magnetic properties. We also highlighted the potential mechanisms and recent advances in transition metal ion-doped MNPs (TMNPs) for bioimaging (magnetic resonance imaging and magnetic particle imaging) and tumour therapy (e.g., magneto-mechanical killing, magnetothermal therapy, and drug delivery). Finally, we summarised the current challenges and future trends of TMNPs in the biomedical field based on the latest advances by researchers. Graphical abstract Image, graphical abstractTransition metal doped magnetic nanoparticles (TMNPs) for biomedical applications
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Project description:Electrochemical oxidation of CH4 is known to be inefficient in aqueous electrolytes. The lower activity of methane oxidation reaction (MOR) is primarily attributed to the dominant oxygen evolution reaction (OER) and the higher barrier for CH4 activation on transition metal oxides (TMOs). However, a satisfactory explanation for the origins of such lower activity of MOR on TMOs, along with the enabling strategies to partially oxidize CH4 to CH3OH, have not been developed yet. We report here the activation of CH4 is governed by a previously unrecognized consequence of electrostatic (or Madelung) potential of metal atom in TMOs. The measured binding energies of CH4 on 12 different TMOs scale linearly with the Madelung potentials of the metal in the TMOs. The MOR active TMOs are the ones with higher CH4 binding energy and lower Madelung potential. Out of 12 TMOs studied here, only TiO2, IrO2, PbO2, and PtO2 are active for MOR, where the stable active site is the O on top of the metal in TMOs. The reaction pathway for MOR proceeds primarily through *CH x intermediates at lower potentials and through *CH3OH intermediates at higher potentials. The key MOR intermediate *CH3OH is identified on TiO2 under operando conditions at higher potential using transient open-circuit potential measurement. To minimize the overoxidation of *CH3OH, a bimetallic Cu2O3 on TiO2 catalysts is developed, in which Cu reduces the barrier for the reaction of *CH3 and *OH and facilitates the desorption of *CH3OH. The highest faradaic efficiency of 6% is obtained using Cu-Ti bimetallic TMO.
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Project description:We synthesize colloidal nanocrystals (NCs) of Rb3InCl6, composed of isolated metal halide octahedra ("0D"), and of Cs2NaInCl6 and Cs2KInCl6 double perovskites, where all octahedra share corners and are interconnected ("3D"), with the aim to elucidate and compare their optical features once doped with Sb3+ ions. Our optical and computational analyses evidence that the photoluminescence quantum yield (PLQY) of all these systems is consistently lower than that of the corresponding bulk materials due to the presence of deep surface traps from under-coordinated halide ions. Also, Sb-doped "0D" Rb3InCl6 NCs exhibit a higher PLQY than Sb-doped "3D" Cs2NaInCl6 and Cs2KInCl6 NCs, most likely because excitons responsible for the PL emission migrate to the surface faster in 3D NCs than in 0D NCs. We also observe that all these systems feature a large Stokes shift (varying from system to system), a feature that should be of interest for applications in photon management and scintillation technologies. Scintillation properties are evaluated via radioluminescence experiments, and re-absorption-free waveguiding performance in large-area plastic scintillators is assessed using Monte Carlo ray-tracing simulations.
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Project description:Catalytic activities of transition metal-doped IrO2 nanoparticles (TM-IrO2 NPs; TM?=?Cr, Mn, Fe, Co, or Ni) are compared for various oxidation reactions such as electrochemical oxygen evolution reaction (OER), gas-phase photo-oxidation of thiol function group, and CO oxidative conversion. Here, we discovered a series of TM-IrO2 catalysts have a common activity trend for these oxidation reactions, and their activities are closely related with modified electronic states of IrO2, strongly affected by the types of the transition metal across the periodic table. For all oxidation reactions, Cr- and Mn-IrO2 achieved the highest oxidation catalytic activity, and sequentially decreased activities were obtained with Fe, Co, and Ni doped IrO2. For instance, the highest OER activity was achieved by Cr or Mn doping exhibiting the smallest overpotential ??=?275~230?mV at 10?mA/cm2, while Ni-IrO2 showed rather larger overpotential (??=?347?mV) even compared with non-doped IrO2 (??=?314?mV). Scanning transmission X-ray microscopy and high-resolution photoemission spectra of TM-IrO2 indicated dopant metals modified the Ir-O interaction and thus increasing oxygen vacancy defects in IrO2. Strongly positive correlation was observed between the catalytic activities and vacancy states. The amount of defect related signals was observed the most for Cr- or Mn-IrO2, less so for Fe- or Co-IrO2, and unnoted for Ni-IrO2 compared with bare IrO2. Based on these catalytic activities and surface spectroscopic analysis results, vacancy defects induced by doping in TM-IrO2 NPs are proposed to contribute to enhance the oxidation activities.
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