Secondary crystalline phases identification in Cu2ZnSnSe4 thin films: contributions from Raman scattering and photoluminescence

In this work, we present the Raman peak positions of the quaternary pure selenide compound Cu2ZnSnSe4 (CZTSe) and related secondary phases that were grown and studied under the same conditions. A vast discussion about the position of the X-ray diffraction (XRD) reflections of these compounds is presented. It is known that by using XRD only, CZTSe can be identified but nothing can be said about the presence of some secondary phases. Thin films of CZTSe, Cu2SnSe3, ZnSe, SnSe, SnSe2, MoSe2 and a-Se were grown, which allowed their investigation by Raman spectroscopy (RS). Here we present all the Raman spectra of these phases and discuss the similarities with the spectra of CZTSe. The effective analysis depth for the common back-scattering geometry commonly used in RS measurements, as well as the laser penetration depth for photoluminescence (PL) were estimated for different wavelength values. The observed asymmetric PL band on a CZTSe film is compatible with the presence of CZTSe single-phase and is discussed in the scope of the fluctuating potentials’ model. The estimated bandgap energy is close to the values obtained from absorption measurements. In general, the phase identification of CZTSe benefits from the contributions of RS and PL along with the XRD discussion.info:eu-repo/semantics/publishedVersio

CZTSxSe1−x nanocrystals: Composition dependent method of preparation, morphological characterization and cyclic voltammetry data analysis

In this article, synthesis procedures of preparation of copper zinc tin sulpho-selenide (CZTSxSe1−x) alloy nanocrystals and the data acquired for the material characterization are presented. This data article is related to the research article doi: http://dx.doi.org/10.1016/j.solmat.2016.06.030 (Jadhav et al., 2016) [1]. FTIR data have been presented which helped in confirmation of adsorption of oleylamine on CZTSxSe1−x. Transmission electron microscopy (TEM), Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) data have been presented which have been used to reveal the morphological details of the nanocrystals. The Energy dispersive X-ray analysis (EDAX) based elemental mapping data has been presented to confirm the elemental composition of nanocrystals. Procedure for the preparation of CZTSxSe1−x based working electrode for the CV measurements have been given. The summary table for the optical, electrochemical band gaps, valance and conduction band edges as a function of composition are listed for the ready reference. Keywords: Synthesis, Characterization, CZTSxSe1−x nanocrystals, Band edge parameter

Citrate-capped quantum dots of CdSe for the selective photometric detection of silver ions in aqueous solutions

A simple strategy for the synthesis of water soluble, luminescent, citrate-capped CdSe quantum dots (Q-CdSe) and their applications to selective detection of silver ions are described. The steady state photoluminescence (PL) spectra show single, narrow emission band at ca. 554 nm without any contribution from the trap states. The effect of various ions including physiologically important metal ions (viz. K+, Ca2+, Fe3+, Zn2+, Mg2+, Mn2+, Cu2+, Ag+, Pb2+ and Cd2+), on the PL intensity of citrate-capped Q-CdSe has been studied. Among these, selective luminescence quenching with Ag+ ion was found to be predominant. Under the optimum conditions, the response was linear between 1.7 and 18 μM. The quenching constant KSV was found to be ca. 3.4 × 105 M−1. The mechanism of photoluminescence quenching of Q-CdSe by metal ions (Ag+) is also discussed. Based on these studies, the potential use of Q-CdSe as a luminescent probe for the selective detection of silver ion has been proposed

Micelle assisted morphological evolution of silver nanoparticles

Silver nanocrystals are prepared in size and shape selective anionic micelles comprising the surfactant, sodium dodecyl sulfate (SDS). Rod-like micelles of variable lengths were obtained by the addition of a hydrophobic salt, anilinium nitrate that adsorbs on the surface of the micelles thereby modifying its morphology. In this report, we investigate the effect of key parameters of the micelles namely, size and shape of the micelles on the morphology of silver nanocrystals formed. The axial ratio of the rod-like micelles was estimated from dynamic light scattering (DLS) measurements and the resulting silver particles, synthesized in the micellar medium, were characterized by optical absorption, DLS and transmission electron microscopy (TEM).© Elsevie

In situ electrochemical transformation of Ni₃S₂ and Ni₃S₂-Ni from sheets to nanodisks: towards efficient electrocatalysis for Hydrogen Evolution Reaction (HER)

Transition metal sulphides have been viewed as alternatives to platinum based electrocatalysts for HER. Herein, we report the preparation of Ni3S2 in conjunction with Ni in a novel nanosheet morphology and verified its performance for HER. During cyclic polarization, exotic morphological transformation of Ni3S2-Ni from nanosheets to nanodisks has been noted. This change is accompanied with initial increase in over-potential that passed through maxima (∼ 100 mV above the starting potential) and decreased to ∼ 50 mV below the starting value. Enhanced electrocatalytic activity due to the morphological changes from sheets to nanodisks has been attributed to the formation of more number of exposed edge-planes known to promote HER. Kinetic analysis based on Tafel slope displayed by this composite is comparable to that of Pt based catalysts