Diffusion Controlled Features of Microwave Assisted ZnS/ZnO Nanocomposite with Reduced Band Gap

Abstract

ZnS and ZnO are both wide band gap semiconductors. Their nanocomposites have high potential for photocatalytic activity and useful for different applications. In the present investigation, an effort has been made to synthesize ZnS/ZnO nanocomposites by inducing microwave treatment before hydrothermal process to increase the reaction rate of ZnS/ZnO and to reduce the optical band gap of the material. X-ray diffraction data revealed the formation of ZnS as well as ZnO phases. W-H plot and Size-Strain plot revealed information of size and strain present in the material. UV-Vis spectroscopy analysis showed a reduced band gap of 3.14 eV and the refractive index of 2.36 for the material. Microstructural and morphological investigations as carried out by TEM and FESEM showed spherical shaped particles having average crystallite size of about 26 nm. Elemental compositional analysis of the material depicted the presence of zinc, oxygen and sulphur. The electrochemical studies include cyclic voltammetry (CV) and potentiostatic electrochemical impedance spectroscopy (PEIS). CV depicted the diffusion-controlled behaviour of the ZnS/ZnO and the reduction in specific capacitance with increasing scan rate. ZnS/ZnO showed diffusion controlled features indicating that the excitons control the current in the material and thus has a good prospect for solar cells.

Surfactant-mediated modulation of morphology and charge transfer dynamics in tungsten oxide nanoparticles

“…Figure 3(b) shows that the change in band gap energy is prominent in the samples C01 (2.5 eV) and P03 (2.2 eV), which shows significant deviation from the band gap of T01 sample (2.7 eV) due to the alteration of electronic properties in the vicinity of WO 3 nanoparticles by the adsorption of CTAB or PEG molecules and Refractive index of a material is also an important optical property to confirm its suitability for solar cell applications. No long-range propagation is possible because of the large number of carriers resulting in higher number of collisions, if the refractive index value is lower than 1 [32]. Lower is the reflectivity of the material, better the material will perform as a solar cell.…”

“…The electrochemical reactions are generally dominated by any of the two mechanism [32] namely capacitive behaviour or diffusion controlled charge storage of the thin film material. The exact nature can be visualized using relation 18.…”

“…where m here behaves as the slope of the equation, as shown in (figure 9(b)) If the value of slope is nearly 0.5, indicates the diffusion controlled behaviour, and if equal to 1, indicates the capacitive behaviour [32]. The slopes that obtained were 0.347, 0.215, 0.062, 0.219, 0.335 and 0.194 for T01, C01, C02, P01, P02 and P03 respectively, all indicating towards the diffusion controlled nature of the thin films of the deposited samples which was in accordance with the linearity of the current versus Scan rate (figure 9(a)).…”

Fabrication of tunable band gap carbon based zinc nanocomposites for enhanced capacitive behaviour

“…The synthesis route provides the breakage of carbon HOMO LUMO level and transitioning it to create energy levels with zinc creating larger band gap. The refractive index is an important property of a material which is calculated by using equation ( 7) [46].…”

“…As discussed above, the peak current increases with scan rate, it is confirmed by analysing the variation of scan rate versus peak current. The as-synthesized materials show a linear relationship between scan rate and peak current, it indicates that the peak current is increasing with increase in scan rate and thus showing The specific capacitance for the as synthesized materials has been calculated and studied by using equation (10) [46],…”