Zhaopeng Xu

Monomer Protonation-Dependent Surface Polymerization to Achieve One-Step Grafting Cross-Linked Poly(4-Vinylpyridine) Onto Core–Shell Fe3O4@SiO2 Nanoparticles

Functional polymer-grafting silica nanoparticles hold great promise in diverse applications such as molecule recognition, drug delivery, and heterogeneous catalysis due to high density and uniform distribution of functional groups and their tunable spatial distance. However, conventional grafting methods from monomers mainly consist of one or more extra surface modification steps and a subsequent surface polymerization step. A monomer protonation-dependent surface polymerization strategy is proposed to achieve one-step uniform surface grafting of cross-linked poly(4-vinylpyridine) (P4VP) onto core-shell Fe3 O4 @SiO2 nanostructures. At an approximate pH, partially protonated 4VP sites in aqueous solution can be strongly adsorbed onto deprotonated silanol groups (SiO- ) onto Fe3 O4 @SiO2 nanospheres to ensure prior polymerization of these protonated 4VP sites exclusively onto Fe3 O4 @SiO2 nanoparticles and subsequent polymerization of other 4VP and divinylbenzene monomers harvested by these protonated 4VP monomers onto Fe3 O4 @SiO2 nanoparticles, thereby achieving direct grafting of cross-linked P4VP macromolecules onto Fe3 O4 @SiO2 nanoparticles.

Effect of doped substrates on the growth of GaAs nanowires via metal organic chemical vapor deposition

Vertical GaAs nanowires were grown on different doped substrates via Metal Organic Chemical Vapor Deposition by catalyst assisted vapor-liquid-solid mechanism. It is found that both n and p type doped substrates affect catalyst distribution during the formation of alloy catalysts. The catalyst density decreases with an increase in the doping concentration of the substrates. In the growth of GaAs nanowires, the growth rate, which is mostly determined by the atoms diffusion from the pyrolysis of precursors on the surface of nanowires and substrates, is proportional to the catalyst densities. Moreover, the structures of as-grown nanowires are all pure zinc blende without any defects. These results will be valuable for the applications of nanowire-based optical and electrical devices.

Enhanced optical response of crystalline silicon photovoltaic devices with integration of silver nanoparticles and ultrathin TiO2 dielectric layer

Silver nanoparticles (Ag NPs) and the titanium dioxide (TiO2) dielectric layer produced by magnetron sputtering and subsequent annealing treatment, were integrated at the front side of crystalline silicon (c-Si) solar cells. A photovoltaic device was realized based on the c-Si substrate and stacked Ag NPs/TiO2/n/p/Ag layer. The results show that the energy conversion efficiency (ECE) can be improved by 9.9% with the introduction of well-sized Ag NPs and an ultrathin TiO2 dielectric layer to the c-Si solar cells. The presence of the dielectric layer enables Ag NPs to fully exert the advantage of localized surface plasmon resonance (LSPR) and light scattering, and the recombination of the photogenerated carriers originating from Ag NPs is effectively avoided at the surface or in the vicinity of Ag NPs. Moreover, COMSOL Multiphysics simulations were performed to investigate the reflection and absorption of incident light in the c-Si. The simulation results match well with the experimental data.Silver nanoparticles (Ag NPs) and the titanium dioxide (TiO2) dielectric layer produced by magnetron sputtering and subsequent annealing treatment, were integrated at the front side of crystalline silicon (c-Si) solar cells. A photovoltaic device was realized based on the c-Si substrate and stacked Ag NPs/TiO2/n/p/Ag layer. The results show that the energy conversion efficiency (ECE) can be improved by 9.9% with the introduction of well-sized Ag NPs and an ultrathin TiO2 dielectric layer to the c-Si solar cells. The presence of the dielectric layer enables Ag NPs to fully exert the advantage of localized surface plasmon resonance (LSPR) and light scattering, and the recombination of the photogenerated carriers originating from Ag NPs is effectively avoided at the surface or in the vicinity of Ag NPs. Moreover, COMSOL Multiphysics simulations were performed to investigate the reflection and absorption of incident light in the c-Si. The simulation results match well with the experimental data.

The effect of V/III ratio on the morphology and structure of GaAs nanowires by MOCVD

In this paper, GaAs nanowires with different V/III ratios (70, 140, 280 and 560) were vertically grown from bottom to top on GaAs substrates by using metal organic chemical vapor deposition based on gold assisted vapor-liquid-solid mechanism. It is found that the growth rate of nanowires is inversely proportional to their V/III ratio. And the V/III ratio can also change nanowire growth type. For the nanowire with small V/III ratios (≤280), the reactants are most from those atoms merged in the catalyst. But, for the nanowire with V/III ratio 560, the contribution mainly comes from the diffusions of atoms pyrolyzed on the surface of the nanowire and the substrate. A shrunken neck under the catalyst is observed in TEM characterizations. These results will provide a theoretical basis for potential practical applications of nanowire-based devices.