The Electronic Origin of the Visible-Light Absorption Properties of C-, N- and S-Doped TiO₂ Nanomaterials

The Electronic Origin of the Visible-Light Absorption Properties of C-, N- and S-Doped TiO2 Nanomaterial

First-Principles Study of 2.2 nm Silicon Nanocrystals Doped with Boron

First-principles study of boron (B)-doped silicon nanocrystals (Si NCs) at 0 K in the framework of density functional theory has been carried out. It is found that B prefers residing at the surface of Si NCs, similar to phosphorus (P). Different from P, B induces surface restructuring when B is one- or two-coordinated at the NC surface. B doping does not significantly change the bandgap of Si NCs, but in most cases B introduces deep energy levels in the bandgap of Si NCs. This explains the B-doping induced quenching of band-edge light emission usually observed in experiments. The negligible infrared absorption of B-doped Si NCs may result from the fact that only three-coordinated B is formed at the NC surface. The electronic transitions involving the energy levels induced by these three-coordinated B are not in the infrared range

Critical Role of Dopant Location for P-Doped Si Nanocrystals

The doping of phosphorus (P) provides an additional means to control the optical properties of silicon nanocrystals (Si NCs). The P-doping-induced changes in the optical properties of Si NCs, however, have not been consistently understood. On the basis of first-principles calculations, we explain the P-doping-induced infrared absorption of Si NCs and the effect of P-doping on the light emission from Si NCs. The explanations are enabled by the investigation of the locations of P in Si NCs, including a variety of locations at the surface of Si NCs. We show that the light emission from Si NCs critically depends on the location of P. Transitions involving P-doping-induced defect energy levels lead to the infrared absorption of Si NCs

Electrochemical Activity of Iron Phosphide Nanoparticles in Hydrogen Evolution Reaction

Iron phosphide (FeP) has been recently demonstrated as a very attractive electrocatalyst for the hydrogen evolution reaction (HER). However, the understanding of its properties is far from satisfactory. Herein, we report the HER performance of FeP nanoparticles is enhanced after a stability test due to reduced surface-charge-transfer resistance in the HER process. The synthetic temperature and reactant ratio are important for surface-charge-transfer resistance, the electrochemically active surface area, and HER activity. Hydrogenation apparently improves the HER performance of FeP nanoparticles by reducing the surface-charge-transfer resistance, overpotential, and Tafel slope. Enhanced HER performance is observed after a stability test for both bare and hydrogenated FeP nanoparticles in the HER due to reduced surface-charge-transfer resistance. Thus, this study may enrich our knowledge and understanding to advance HER catalysis for electrochemical hydrogen generation

Semiconductor Quantum Dots for Photodynamic Therapy

The applicability of semiconductor QDs in photodynamic therapy (PDT) was evaluated by studying the interaction between CdSe QDs with a known silicon phthalocyanine PDT photosensitizer, Pc4. The study revealed that the QDs could be used to sensitize the PDT agent through a fluorescence resonance energy transfer (FRET) mechanism, or interact directly with molecular oxygen via a triplet energy-transfer process (TET). Both mechanisms result in the generation of reactive singlet oxygen species that can be used for PDT cancer therapy

Three-Dimensional Crystalline/Amorphous Co/Co₃O₄ Core/Shell Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction

Earth-abundant, low-cost electrocatalysts with outstanding catalytic activity in the electrochemical hydrogen evolution reaction (HER) are critical in realizing the hydrogen economy to lift our future welfare and civilization. Here we report that excellent HER activity has been achieved with three-dimensional core/shell Co/Co₃O₄ nanosheets composed of a metallic cobalt core and an amorphous cobalt oxide shell. A benchmark HER current density of 10 mA cm^–2 has been achieved at an overpotential of ∼90 mV in 1 M KOH. The excellent activity is enabled with the unique metal/oxide core/shell structure, which allows high electrical conductivity in the core and high catalytic activity on the shell. This finding may open a door to the design and fabrication of earth-abundant, low-cost metal oxide electrocatalysts with satisfactory hydrogen evolution reaction activities

Isobaric (Vapor + Liquid) Equilibria for Methylcyclohexane with Para‑, Ortho‑, and Meta-Xylenes and Ethylbenzene at 101.33 kPa

A series of isobaric vapor–liquid equilibrium experiments were conducted on binary mixtures of methylcyclohexane with para-, ortho-, and meta-xylenes and ethylbenzene, at a pressure of 101.33 kPa, using an Othmer still equipment setup. The resulting composition of vapor and liquid phases was determined by gas chromatography, while the thermodynamic consistency of measured results was checked using the van Ness and Wisniak L–W methods. The measured equilibrium data were fitted with activity coefficient models of the nonrandom two-liquid, the Wilson, and the extended universal quasichemical, and the binary interaction parameters of these models were obtained. The vapor–liquid equilibrium diagrams were predicted by the fitted models, which matched well with experimental data

Effect of Vacuum System Base Pressure On Corrosion Resistance of Sputtered Al Thin Films

Effect of Vacuum System Base Pressure On Corrosion Resistance of Sputtered Al Thin Film