Hierarchical Nanoporous BiVO4 Photoanodes with High Charge Separation and Transport Efficiency for Water Oxidation.

To fabricate high efficiency photoanodes for water oxidation, it is highly required to engineer their nanoporous architecture and interface to improve the charge separation and transport efficiency. By focusing on this aspect, we developed hierarchical nanoporous BiVO4 (BV) from solution processed two-dimensional BiOI (BI) crystals. The orientation of the BI crystals was controlled by changing the solvent volume ratios of ethylene glycol (EG) to ethanol (ET), which resulted in different hierarchical and planar BV morphologies through a chemical treatment followed by thermal heating. The morphology with optimal particle dimension, connectivity, and porosity can offer a highly enhanced electrochemically active surface area (ECSA). The hierarchical BV owning a maximum ECSA showed the best photoelectrochemical (PEC) performance in terms of the highest photocurrent density and charge separation efficiency. However, to further improve the performance of the electrode, conformal and ultrathin SnO2 underlayers were deposited by a powerful atomic layer deposition technique at the interface to effectively block the defect density, which significantly improved the photocurrents as high as 3.25 mA/cm2 for sulfite oxidation and 2.55 mA/cm2 for water oxidation at 0.6 V versus the reversible hydrogen electrode (RHE). The electrode possessed record charge separation efficiency of 97.1% and charge transfer efficiency of 90.1% at 1.23 VRHE among to-date reported BiVO4-based photoanodes for water oxidation. Furthermore, a maximum applied bias photon-to-current efficiency (ABPE) of 1.61% was found at a potential as low as 0.6 VRHE, which is highly promising to make a tandem cell. These results indicate that the construction of the hierarchical nanoporous photoanode with an enhanced ECSA and its proper interface engineering can significantly improve the PEC performance.

Anti-biofilm activity and food packaging application of room temperature solution process based polyethylene glycol capped Ag-ZnO-graphene nanocomposite.

Present work reports on synthesis and anti-biofilm activity as well as food packaging application of Ag-ZnO-reduce graphene oxide (rGO)-polyethylene glycol (PEG) (AZGP) nanocomposites via adopting room temperature solution process by varying silver nitrate content (up to 0.1 M) with fixed content of graphene oxide and PEG used in the precursors. Presence of Ag and ZnO nanoparticles (NPs) distributed uniformly over rGO nanosheets has been confirmed by X-ray diffraction and transmission electron microscopic analyses whereas FTIR, Raman, UV-Visible and X-ray photoelectron spectral studies have been performed to confirm the existence of chemical interaction/complexation that happened between the available oxygen functionalities of rGO and PEG with the inorganic moieties (Ag-ZnO/Zn2+) of AZGP samples. A formation mechanism of AZGP nanocomposite is proposed based on the experimental results. Anti-biofilm activity has been studied on Staphylococcus aureus and Pseudomonas aeruginosa bacteria to confirm the efficiency of the nanocomposites for killing the bacterial cells. It is found that 0.05 M silver nitrate based AZGP nanocomposite at 31.25 µg/mL sample dosage shows about 95% inhibition activity towards the biofilm formation as well as eradication of preformed biofilm. Also, agar based AZGP film has been fabricated and characterized by X-ray diffraction study for the purpose of food packaging application. Textural analysis of agar based film shows an enhanced film tensile strength. The film also shows an excellent antimicrobial activity even after keeping it for a prolong period of about 90 days. This cost effective simple synthesis strategy can make an avenue for development of Ag incorporated other biocompatible metal oxide based rGO-PEG nanocomposites for potential food packaging application.

Hierarchically Structured Macro with Nested Mesoporous Zinc Indium Oxide Conducting Film.

Fabrication of homogeneously distributed (HD) macropores by breath figure process is an active research area. Adopting the process, for the first time, we report the fabrication of HD macro with nested meso (hierarchical) porous nanocrystalline zinc indium oxide conducting sol-gel thin film on glass by dip-coating at 45-50% room relative humidity (RH) from a solution in ethanol-2-butanol (1:1, w/w) medium with a 1:1, Zn:In ratio. In this process, solution composition and RH are found to play key roles on HD macropore generation. The film is highly promising toward visible-light-driven photoelectrochemical water splitting.

Sol-Gel-Based Titania-Silica Thin Film Overlay for Long Period Fiber Grating-Based Biosensors.

An evanescent wave optical fiber biosensor based on titania-silica-coated long period grating (LPG) is presented. The chemical overlay, which increases the refractive index (RI) sensitivity of the sensor, consists of a sol-gel-based titania-silica thin film, deposited along the sensing portion of the fiber by means of the dip-coating technique. Changing both the sol viscosity and the withdrawal speed during the dip-coating made it possible to adjust the thickness of the film overlay, which is a crucial parameter for the sensor performance. After the functionalization of the fiber surface using a methacrylic acid/methacrylate copolymer, an antibody/antigen (IgG/anti-IgG) assay was carried out to assess the performance of sol-gel based titania-silica-coated LPGs as biosensors. The analyte concentration was determined from the wavelength shift at the end of the binding process and from the initial binding rate. This is the first time that a sol-gel based titania-silica-coated LPG is proposed as an effective and feasible label-free biosensor. The specificity of the sensor was validated by performing the same model assay after spiking anti-IgG into human serum. With this structured LPG, detection limits of the order of tens of micrograms per liter (10(-11) M) are attained.

ZnSe colloidal nanoparticles synthesized by solvothermal method in the presence of ZrCl4.

The nanocrystalline ZnSe was synthesized from precursors of zinc acetate and Se powder in a high boiling trioctylphosphine (TOP), oleic acid, and ZrCl(4) by solvothermal method. The produced ZnSe nanoparticles showed gradual absorption edge shifting towards blue wavelength region as well as transformation of crystal phase from cubic to hexagonal with increasing ZrCl(4) concentrations in precursor solutions. The particle size calculated from XRD measurements for ZnSe nanoparticles was decreased with increasing ZrCl(4) concentrations for a reaction time of 240 min, from 6.5 nm to 5.1 nm whereas from TEM measurements it was 7.0 to 6.1 nm at 0.0 and 22.5 mol% of ZrCl(4), respectively. No trace of zirconium was found in solid ZnSe nanoparticles by SEM-EDS analysis but the atomic percentage of Se with respective to Zn was decreased with increasing ZrCl(4). The absorption edge blue shifting was explained on the basis of decreased particle size. The crystal phase transformation may be due to the combined effect of small internal energy difference between the two phases and the decrease of crystallite size.

Ligand-dependent particle size control of PbSe quantum dots.

Colloidal solutions of monodisperse PbSe quantum dots (QDs) were synthesized by a hot solution chemical method from a reaction mixture of lead oleate and TOPSe (TOP: tri-n-octylphosphine). The synthesis was carried out at a fixed temperature (170 degrees C) and time, while the particle sizes of the PbSe QDs were controlled by using two different kinds of organic ligands with varied chain length. It was seen that the tuning of PbSe QDs are possible by using the proper molar ratio of the co-ligands, such as acetic acid or hexanoic acid, at a fixed reaction temperature and time, verified by TEM and XRD as well as NIR absorption analysis. The effects of different organic acids were studied and the role of additional organic acids might be due to the extent of ligand exchange efficiency between the Pb oleate and acetic/hexanoic acid in the initial stage, which is caused by the steric hindrance effects of the acids.