Proc Natl Acad Sci U S A
December 2016
InO(OH) nanoparticles have been shown to function as an effective gas-phase photocatalyst for the reduction of CO to CO via the reverse water-gas shift reaction. Their photocatalytic activity is strongly correlated to the number of oxygen vacancy and hydroxide defects present in the system. To better understand how such defects interact with photogenerated electrons and holes in these materials, we have studied the relaxation dynamics of InO(OH) nanoparticles with varying concentration of defects using two different excitation energies corresponding to above-band-gap (318-nm) and near-band-gap (405-nm) excitations.
View Article and Find Full Text PDFThe reverse water gas shift (RWGS) reaction driven by NbO nanorod-supported Pd nanocrystals without external heating using visible and near infrared (NIR) light is demonstrated. By measuring the dependence of the RWGS reaction rates on the intensity and spectral power distribution of filtered light incident onto the nanostructured Pd@NbO catalyst, it is determined that the RWGS reaction is activated photothermally. That is the RWGS reaction is initiated by heat generated from thermalization of charge carriers in the Pd nanocrystals that are excited by interband and intraband absorption of visible and NIR light.
View Article and Find Full Text PDFIn this report, the synthesis of a novel class of cationic quaternary ammonium-surface-functionalized silicon nanocrystals (ncSi) using a novel and highly versatile terminal alkyl halide-surface-functionalized ncSi synthon is described. The distinctive features of these cationic ncSi include colloidal stability, pH-independent positive surface charge, and size-tunable photoluminescence (PL) in the biologically relevant near-infrared-to-red spectral region. These cationic ncSi are characterized via a combination of high-resolution scanning transmission electron microscopy with energy-dispersive X-ray analysis, Fourier transform infrared, X-ray photoelectron, and photoluminescence spectroscopies, and zeta potential measurements.
View Article and Find Full Text PDFThe development of strategies for increasing the lifetime of photoexcited charge carriers in nanostructured metal oxide semiconductors is important for enhancing their photocatalytic activity. Intensive efforts have been made in tailoring the properties of the nanostructured photocatalysts through different ways, mainly including band-structure engineering, doping, catalyst-support interaction, and loading cocatalysts. In liquid-phase photocatalytic dye degradation and water splitting, it was recently found that nanocrystal superstructure based semiconductors exhibited improved spatial separation of photoexcited charge carriers and enhanced photocatalytic performance.
View Article and Find Full Text PDFThermal treatment of ultrathin films of hematite (α-Fe2 O3 ) under an atmosphere of 5 % H2 in Ar is presented as a means of activating α-Fe2 O3 towards the photoelectrochemical splitting of water. Spin-coated films annealed in air exhibited no photoactivity, whereas films treated in hydrogen exhibited a photocurrent response. X-ray photoelectron spectroscopy and UV/Vis absorption spectroscopy results showed that the H2 -treated films contain oxygen vacancies, which suggests improved charge transport.
View Article and Find Full Text PDFNanotower- and nanowall-like indium oxide structures were grown directly on fluorine-doped tin oxide (FTO)/In2O3 seeded substrates and pristine FTO substrates, respectively, by a straightforward solvothermal method. The tower-like nanostructures are proposed to form via a self-assembly process on the In2O3 seeds. The wall-like nanostructures are proposed to form via epitaxial growth from the exposed edges of SnO2 crystals of the FTO substrate.
View Article and Find Full Text PDFis a very important research challenge, with implications for both climate change and energy security. Herein, the key attributes of hydroxides and oxygen vacancies are experimentally identified in non-stoichiometric indium oxide nanoparticles, InO(OH), that function in concert to reduce CO to CO under simulated solar irradiation.
View Article and Find Full Text PDFHere we describe for the first time the synthesis of colloidally stable, brightly luminescent perfluorodecyl-capped silicon nanocrystals and compare the properties of solutions and films made from them with those of their perhydrodecyl-capped relatives. The perfluorodecyl capping group compared to the perhydrodecyl capping group yields superior hydrophobicity and much greater resistance to air oxidation, the enhanced electron-withdrawing character induces blue shifts in the wavelength of photoluminescence, and the lower-frequency carbon-fluorine stretching modes disfavor non-radiative relaxation pathways and boost the absolute photoluminescence quantum yield. Together these attributes bode well for advanced materials and biomedical applications founded upon perfluorodecyl-protected silicon nanocrystals.
View Article and Find Full Text PDFIn recent years, a lot of attention has been devoted to monolayer materials, in particular to transition-metal dichalcogenides (TMDCs). While their growth on a substrate and their exfoliation are well developed, the colloidal synthesis of monolayers in solution remains challenging. This paper describes the development of synthetic protocols for producing colloidal WS2 monolayers, presenting not only the usual semiconducting prismatic 2H-WS2 structure but also the less common distorted octahedral 1T-WS2 structure, which exhibits metallic behavior.
View Article and Find Full Text PDFNanorods of triniobium hydroxide heptaoxide, Nb3 O7 (OH), were synthesized by means of a hydrothermal method. Subsequently, Pt and CuO nanoparticles were introduced on the surface of Nb3 O7 (OH) nanorods by a microwave-assisted solvothermal nucleation and growth technique. The resulting Pt- and CuO-decorated Nb3 O7 (OH) nanorods demonstrated uniform particle dispersion and were fully characterized by X-ray diffraction, electron microscopy, and spectroscopic analysis.
View Article and Find Full Text PDFDetermination of the concentration of ascorbic acid in a solution has attracted intense recent interest. Here we demonstrate the feasibility of electro-oxidation of ascorbic acid on spherical cobalt core-shell nanoparticles (10-50 nm dia.) prepared by electrochemical deposition on a H-terminated Si(100) substrate.
View Article and Find Full Text PDFUsing single-crystal adsorption calorimetry (SCAC) and density functional theory (DFT), the interaction of carbon monoxide on fcc Co{110} is reported for the first time. The results indicate that adsorption is consistent with molecular chemisorption at all coverages. The initial heat of adsorption of 140 kJ mol(-1) is found in the range of heat values calorimetrically measured on other ferromagnetic metal surfaces, such as nickel and iron.
View Article and Find Full Text PDFThe coverage dependent heats of adsorption and sticking probabilities for oxygen on fcc Co{110} have been measured at 300 K using single crystal adsorption calorimetry (SCAC). Initial adsorption is consistent with dissociative chemisorption at low coverage followed by oxide formation above 0.6 ML coverage.
View Article and Find Full Text PDFThe a- and b-type rotational transitions of the weakly bound complexes formed by molecular hydrogen and OCS, para-H2-OCS, ortho-H2-OCS, HD-OCS, para-D2-OCS, and ortho-D2-OCS, have been measured by Fourier transform microwave spectroscopy. All five species have ground rotational states with total rotational angular momentum J=0, regardless of whether the hydrogen rotational angular momentum is j=0 as in para-H2, ortho-D2, and HD or j=1 as in ortho-H2 and para-D2. This indicates quenching of the hydrogen angular momentum for the ortho-H2 and para-D2 species by the anisotropy of the intermolecular potential.
View Article and Find Full Text PDFThe effect of a co-eluting halogenated phenol, spiked at 1% of the main analyte level, has been examined for a series of halogenated phenols using LC-MS techniques. Similarly, the effect of co-eluting anilines has been investigated. The purpose of the work presented here was to evaluate the degree of signal suppression for structurally similar halogenated phenols and for similar anilines utilizing atmospheric pressure chemical ionization (APCI) in the negative mode and electrospray (ESI) in positive mode, respectively.
View Article and Find Full Text PDF