Influence of morphology, crystal structures on the enhanced photoluminescence dynamics, zeta potential, and AC resistance of disc shaped cesium oxidex@cobalt oxide nanostructures

Abstract

In the present study, cesium oxide_x@cobalt oxide (Cs₂O_x@Co₃O₄) (x = 5, 10 and 12 wt%) nanostructures (NS) were successfully synthesized by chemical precipitation method and characterized by XRD (X-ray diffraction), SEM (scanning electron microscope), EDX (energy dispersive X-ray), XPS (X-ray photoelectron spectroscopy), BET (Brunauer-Emmett-Teller), Raman, and UV–visible analytical techniques. XRD studies revealed the formation of the mixed phase of orthorhombic/monoclinic crystal structure. Disc shaped morphology of the cesium oxide_x@cobalt oxide NS was noticed from SEM images. Redshift in optical absorbance and decrease in optical band gap (E_g) resulted in increase in Cs¹⁺ concentration. Room temperature photoluminescence (RTPL) studies of cesium oxide_x@cobalt oxide NS at various excitation wavelengths showed sharp and broad emission peaks located at 668.2 nm (red), 675.1 nm (red), 561.8 nm (yellow-green), 834.5 nm (near infrared region), 594 nm (yellow). Steady state photoluminescence (SSPL) studies revealed a sharp emission peak at ∼ 428.0 nm (violet) with large stoke’s shift (21.1 to 590.0 eV). The zeta potential studies showed a decrease in conductance from 62 to 57 μs with an increase in mobility of the charge carriers (0.4 to 1.08 μ/s V/cm) and an increase in zeta potential (31.90 to 82.92 mV). AC resistance studies at various temperatures showed inducting coupling phenomenon in cesium oxide_x@cobalt oxide NS with DC resistance of cesium oxide_{5 wt.%}@cobalt oxide was found to be 8.2 × 10^–4 Sm^–1. The relaxation frequency of cesium oxide_{12 wt.%}@cobalt oxide NS was found be 1.2 × 10⁵ Hz. The synthesized NS is a promising candidate for optoelectronics and photonic applications.