Apurav Guleria

Aqueous phase one-pot green synthesis of SnSe nanosheets in a protein matrix: negligible cytotoxicity and room temperature emission in the visible region

In recent times, SnSe has attracted considerable attention as an environmentally friendly alternative to cadmium- and lead-based photovoltaic materials. Herein, we report a rapid, facile, reproducible, and purely green method for the synthesis of SnSe nanosheets (NS) in an aqueous solution of bovine serum albumin (BSA). Interestingly, BSA itself acted as a reducing agent, stabilizing agent and shape directing template. Time dependent TEM imaging showed the self-assembly of the nanoparticles (NPs) into single crystalline NS. A probable mechanism has been proposed on the basis of the alteration of the intrinsic α-helix structure of BSA into β-pleated sheets at the pH (∼3.0) of the reaction mixture. This directs the self-assembly of small SnSe NPs into the NS like structure. It was further evident that the –NH and the –S–S– linkages in the protein are involved in the functionalization of the NPs. As grown SnSe nanomaterial was found to display room temperature photoluminescence (PL), which has been rarely reported. The PL spectra appeared to be the convolution of two bands at 425 and 470 nm, which were attributed to the band-gap and trap/surface state emission, respectively. Moreover, the reduction potential values obtained from the cyclic voltammetry indicate better thermodynamic feasibility for the reduction of SnSe, while the cytotoxicity studies revealed no toxic effects up to a concentration of 100 μM. This signifies the potential application of these nanomaterials in photovoltaics and biomedical contexts.

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

In recent times, tin selenides have attracted considerable attention as an environment friendly alternative to cadmium- and lead-based optoelectronic devices. Herein, we report a one pot rapid synthesis of SnSe nanoparticles in neat imidazolium based room temperature ionic liquid (RTIL) for the first time, via electron beam irradiation. The RTIL being the host matrix provides a stabilizing environment as well as an in situ source of reducing radicals for the reduction of precursors. Additionally, it also facilitates the self-assembling of nanoparticles into porous nanomorphologies. UV-Vis absorption spectra of the nanoparticles clearly showed an excitonic peak at ∼460 nm, which indicates a strong quantum confinement. Various characterization studies i.e. XRD, XPS, Raman and EDX have confirmed the formation of SnSe. The average size of the nanoparticles as determined from the TEM measurements was found to be ∼7 nm. The FESEM measurements revealed self-assembling of globular nanoparticles into a highly porous structure. Interestingly, the variation in the dose rate was found to modify the morphology as an equivalent dose of γ-irradiation led to the transformation of porous nanostructures into corn-flake like structures. The possible mechanism behind the obtained nanomorphologies has been proposed, and was rationalized in terms of the dose rate involved and the inherent structure of the RTIL. SnSe is a highly promising emerging material of research; the utilization, integration and exploitation of such newer synthetic strategies would enable the formation as well as convenient maneuverability of its complex nanomorphologies, which might add greater dimensions to its applications.