Interfacial molecular regulation of TiO2 for enhanced and stable cocatalyst-free photocatalytic hydrogen production.

On the basis of the inherent property limitations of commercial P25-TiO2, many surface interface modification methods have attracted substantial attention for further improving the photocatalytic properties. However, current strategies for designing and modifying efficient photocatalysts (which exhibit complicated manufacturing processes and harsh conditions) are not efficient for production that is low cost, is nontoxic, and exhibits good stability; and therefore restrict practical applications. Herein, a facile and reliable method is reported for in situ amine-containing silane coupling agent functionalization of commercial P25-TiO2 by covalent surface modification for constructing a highly efficient photocatalyst. As a consequence, a high efficiency of H2 evolution was achieved for TiO2-SDA with 0.95 mmol h-1 g-1 (AQE ∼45.6 % at 365 nm) under solar light irradiation without a co-catalyst. The amination modification broadens the light absorption range of the photocatalyst, inhibits the binding of photogenerated carriers, and improves the photocatalytic efficiency; which was verified by photochemical properties and DFT theoretical calculations. This covalent modification method ensures the stability of the photocatalytic reaction. This work provides an approach for molecularly modified photocatalysts to improve photocatalytic performance by covalently modifying small molecules containing amine groups on the photocatalyst surface.

Indoor gas phase photoactivity of yttrium modified titanate films for fast acetaldehyde oxidation.

Photoactive materials hold structural and catalytic features that make them particularly suitable for environmental applications and in the present work, protonated H3Ti3O7-Y nanofiber-like materials were prepared via the microwave assisted hydrothermal technique. The as-prepared nanofibers exhibited high surface area with titanate structure. The nanofibers, before and after yttrium incorporation, were well-distributed and the fibrous morphology could be observed clearly; as the yttrium loading increased, ribbons and the anatase phase were formed. Practical films of these nanofibers confirmed their likely UV-photoactive properties with 200 ppm of acetaldehyde degradation within 25 min in the presence of 50% of humidity. Activity retention was achieved, keeping stability for 2 consecutive cycles at room temperature. Nowadays, the increase in home office work sets human health at risk, for the exposure to toxic volatile organic compounds and microorganisms such as viruses and bacteria is more frequent indoors. In this context, the synthesized photoactive yttrium-titanate films stand as upcoming practical UV-driven materials for cleaning pollution that concentrated urban activity and indoor environments.

Photocatalytic degradation of bisphenol A using titanium dioxide@nanodiamond composites under UV light illumination.

Different types of organic impurities such as dyes, acids, and alcohols are discharged into potable water sources. The removal of these hazardous organic pollutants from wastewater is an important task globally. However, the conventional methods used to remove organic impurities suffer from low efficiency and recycling problems. Photocatalysis is a promising advanced oxidation process for the degradation of organic compounds in aqueous solution. Titanium dioxide (TiO2) is commonly used as a photocatalyst. However, the wide bandgap of TiO2 means that it is activated by ultraviolet light, which restrains its ability to harvest solar energy. In this study, a simple water-based precipitation method was used to synthesize TiO2@nanodiamond composites. The ability of the composites to degrade bisphenol A as a model organic pollutant was investigated. It was found that 10 ppm of bisphenol A was completely degraded in 100 min by the TiO2@nanodiamond photocatalyst under ultraviolet illumination.

One-Pot Synthesis of Anatase, Rutile-Decorated Hydrogen Titanate Nanorods by Yttrium Doping for Solar H2 Production.

We have prepared yttrium (Y)-doped hydrogen titanate nanorods (HTN) by a microwave-assisted hydrothermal method. Y-doped HTN showed much improved photocatalytic activities for both H2 evolution and dye decomposition. H2 production from a methanol-water solution under UV-visible light for 7 h was enhanced by a factor of 5.5 with 1 wt % Y-doping. Doping with Y3+ ions reduced the band gap of HTN by ∼0.28 eV and induced new phases of anatase and rutile. High photocatalysis by Y-doping was attributed to enhanced light absorption (smaller band gap) and effective charge separation (heterojunction). To optimize H2 production, a series of experiments examining effects of doping concentrations and non-noble surface metal (e.g., Ni, Cu, Co) loading were carefully performed. Y-doping in this work is a new and promising approach for synthesizing highly active HTN by producing the HTN/rutile/anatase heterostructure within the one-pot method.

Control of Particle Size in Flame Spray Pyrolysis of Tb-doped Y2O3 for Bio-Imaging.

Recently, the use of oxide-based nanomaterials for bio-imaging has received great attention owing to their remarkable stabilities as compared to those of conventional organic dyes. Therefore, the development of scalable methods for highly luminescent oxide materials with fine control of size has become crucial. In this study, we suggested modified flame spray pyrolysis (FSP) as a scalable method to produce a green-light emitting phosphor-Tb-doped Y2O3-in the nanometer size range. In our FSP method, an alkali salt (NaNO3) was found to be highly effective as a size-controlling agent when it is simply mixed with other metal nitrate precursors. The FSP of the mixture solution resulted in oxide composites of Y2O3:Tb3+ and NaxO. However, the sodium by-product was easily removed by washing with water. This salt-assisted FSP produced nano-sized and well-dispersed Y2O3:Tb3+ nanoparticles; their crystallinity and luminescence were higher than those of the bulk product made without the addition of the alkali salt. The nanoparticle surface was further coated with silica for biocompatibility and functionalized with amino groups for the attachment of biological molecules.

Unexpected Roles of Interstitially Doped Lithium in Blue and Green Light Emitting Y2O3:Bi3+: A Combined Experimental and Computational Study.

To enhance the photoluminescence of lanthanide oxide, a clear understanding of its defect chemistry is necessary. In particular, when yttrium oxide, a widely used phosphor, undergoes doping, several of its atomic structures may be coupled with point defects that are difficult to understand through experimental results alone. Here, we report the strong enhancement of the photoluminescence (PL) of Y2O3:Bi3+ via codoping with Li+ ions and suggest a plausible mechanism for that enhancement using both experimental and computational studies. The codoping of Li+ ions into the Y2O3:Bi3+ phosphor was found to cause significant changes in its structural and optical properties. Interestingly, unlike previous reports on Li+ codoping with several other phosphors, we found that Li+ ions preferentially occupy interstitial sites of the Y2O3:Bi3+ phosphor. Computational insights based on density functional theory calculations also indicate that Li+ is energetically more stable in the interstitial sites than in the substitutional sites. In addition, interstitially doped Li+ was found to favor the vicinity of Bi3+ by an energy difference of 0.40 eV in comparison to isolated sites. The calculated DOS showed the formation of a shallow level directly above the unoccupied 6p orbital of Bi3+ as the result of interstitial Li+ doping, which may be responsible for the enhanced PL. Although the crystallinity of the host materials increased with the addition of Li salts, the degree of increase was minimal when the Li+ content was low (<1 mol %) where major PL enhancement was observed. Therefore, we reason that the enhanced PL mainly results from the shallow levels created by the interstitial Li+.