Mesoporous zinc-blende ZnS nanoparticles: synthesis, characterization and superior photocatalytic properties

Photocatalytic reforming of biomass for hydrogen production over ZnS nanoparticles modified carbon nitride nanosheets

Hydrogen generation from biomass reforming via solar energy utilisation has become a fascinating strategy toward future energy sustainability. In this study, ZnS nanoparticles with an average size around 10-15 nm were synthesised by a facile hydrothermal method, and then hybridised with g-C₃N₄ (MCN, DCN, and UCN) derived from melamine, dicyandiamide and urea, producing the heterojunctions denoted as ZMCN, ZDCN and ZUCN, respectively. Advanced characterisations were employed to investigate the physiochemical properties of the materials. ZMCN and ZDCN showed a slight red shift and better light absorbance ability. Their catalytic performances were evaluated by photocatalytic biomass reforming for hydrogen generation. The hydrogen generation rate on ZMCN, the best photocatalyst among MCN, DCN, UCN, ZDCN and ZUCN, was around 2.5 times higher than the pristine MCN. However, the photocatalytic efficiency of ZUCN experienced decrease of 36.6% compared to pure UCN. The mechanism of the photocatalytic reforming process was discussed. The photoluminescence spectra of ZMCN suggested that the introduction of ZnS for ZMCN would reduce the recombination of photoinduced carriers. It was also found that both microstructure and band structure would influence the photocatalytic reforming efficiency.

Synthesis, Characterisation, and Photocatalytic Behaviour of Mesoporous ZnS Nanoparticles Prepared Using By-Product Templating

High surface area mesoporous ZnS nanoparticles (MZN) were obtained with the aid of the by-product of the synthesising reaction. This by-product, namely NaNO3, can be considered as a soft template responsible for the formation of pores. Ethanol and water were chosen as the synthesis media. Ultrasonic waves were used as an accelerator for the synthesis of MZNs. Photocatalytic activities of the synthesised samples for the degradation of methylene blue (MB) were investigated under ultraviolet irradiation. Synthesised specimens were characterised using field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, diffuse reflectance spectroscopy, N2-physisorption, and FT-IR spectroscopy. Results indicated that the synthesis media has a pronounced effect on the surface properties of the final porous particles by several mechanisms. The specific surface area of the MZN samples synthesised in water and ethanol were determined to be 53 and 201 m2 g−1, respectively. The difference in the specific surface area was attributed to the weak solvation of S2− ions (Na2S·5H2O in ethanol) and also to the by-product of the synthesis reaction. The photocatalytic behaviour of the mesoporous ZnS nanoparticles synthesised in these two media were investigated and the results have been interpreted with the aid of effective surface area, pore volume, and bandgap energy of the specimens.

Porous nanostructures of SnSe: role of ionic liquid, tuning of nanomorphology and mechanistic studies

Porous SnSe nanoparticles have been synthesized in imidazolium based RTILviaelectron beam irradiation. RTIL provides a stabilizing environment as well as anin situsource of reducing radicals for the reduction of precursors.

Aqueous synthesis of internally doped Cu:ZnSe/ZnS core-shell nanocrystals with good stability

To prepare biologically available Zn-based NCs in aqueous solution, we herein reported the synthesis of aqueous Cu:ZnSe/ZnS NCs with internally doped aqueous Cu:ZnSe NCs as the core template. Due to the dual protection of Cu impurities by the ZnSe core and ZnS shells, the as-prepared Cu:ZnSe/ZnS NCs show excellent stability in the open air, which overcomes the intrinsic instability of traditional aqueous Cu:ZnSe NCs. The as-prepared Cu:ZnSe/ZnS NCs possess extremely good stability, good biocompatibility and lower cytotoxicity, and thus can be used as a promising candidate for fluorescent NC-based biological applications.

L-cysteine-assisted growth of core-satellite ZnS-Au nanoassemblies with high photocatalytic efficiency

Core-satellite ZnS-Au nanoassemblies, in which each of the ZnS nanospheres was surrounded by a few Au nanoparticles, have been successfully prepared with a facile L-cysteine-assisted hydrothermal approach. The density of Au nanoparticles encircling each ZnS nanosphere can be readily controlled through suitably modulating the concentration of Au added. Because of the difference in band structures between ZnS and Au, a pronounced photoinduced charge separation was observed for the as-synthesized ZnS-Au nanoassemblies. As compared to the relevant commercial products like Au-loaded P-25 TiO(2) and ZnS powders, ZnS-Au nanoassemblies exhibited superior photocatalytic performance, demonstrating their potential as an efficient photocatalyst in relevant redox reactions. Furthermore, the recycling test revealed that core-satellite nanoassemblies of ZnS-Au could be promisingly utilized in the long-term course of photocatalysis. The present study provides a new paradigm for designing the highly efficient semiconductor/metal hybrid photocatalysts that can effectively produce chemical energy from light.

Bio-conjugated luminescent quantum dots of doped ZnS: a cyto-friendly system for targeted cancer imaging

A heavy-metal-free luminescent quantum dot (QD) based on doped zinc sulfide (ZnS), conjugated with a cancer-targeting ligand, folic acid (FA), is presented as a promising bio-friendly system for targeted cancer imaging. Doped QDs were prepared by a simple aqueous method at room temperature. X-ray diffraction and transmission electron microscopy studies showed the formation of monodisperse QDs of average size approximately 4 nm with cubic (sphalerite) crystal structure. Doping of the QDs with metals (Al(3+)), transition metals (Cu(+), Mn(2+)) and halides (F(-)) resulted in multi-color emission with dopant-specific color tunability ranging from blue (480 nm) to red (622 nm). Luminescent centers in doped QDs could be excited using bio-friendly visible light >400 nm by directly populating the dopant centers, leading to bright emission. The cytotoxicity of bare and FA conjugated QDs was tested in vitro using normal lung fibroblast cell line (L929), folate-receptor-positive (FR+) nasopharyngeal epidermoid carcinoma cell line (KB), and FR-negative (FR-) lung cancer cell line (A549). Both bare and FA-conjugated ZnS QDs elicited no apparent toxicity even at high concentrations of approximately 100 microM and 48 h of incubation. In contrast, CdS QDs prepared under identical conditions showed relatively high toxicity even at low concentrations of approximately 0.1 microM and 24 h of incubation. Interaction of FA-QDs with different cell lines showed highly specific attachment of QDs in the FR+ cancer cell line, leaving others unaffected. The bright and stable luminescence of the QDs could be used to image both single cancer cells and colonies of cancer cells without affecting their metabolic activity and morphology. Thus, this study presents, for the first time, the use of non-toxic, Cd-, Te-, Se-, Pb- and Hg-free luminescent QDs for targeted cancer imaging.