Facile synthesis of heterojunction CdS-TiO2 nanocomposites for energy storage supercapacitors, heavy metal detection, photochemical applications, and forensic science advancements: a comparative study with pure CdS and TiO2 nanoparticles

CdS, TiO2 nanomaterials (NMs), and heterojunction CdS-TiO2 nanocomposites (NCs) were successfully synthesized by a facile method for the first time. Different analytical tools were used for characterization, including XRD, BET, SEM, EDAX, TEM, FT-IR, UV-Vis-DRS and Elemental mapping. Additionally, electrochemical impedance spectroscopy was employed to study conductivity properties. For the first time, a comprehensive evaluation of the electrochemical, photochemical, and optical properties of the NMs and NCs was undertaken, encompassing a diverse array of applications. This pioneering assessment explored their capabilities in photoluminescence, forensic analysis, conductivity, energy storage solutions, simultaneous heavy metal detection, and advanced photocatalytic studies, along with comparative insights with pure CdS and TiO2 NMs. NCs exhibit superior electrochemical and photochemical properties, owing to their optimal paired band gap, low impedance, and high electrochemical activity, with an electron lifetime of 31.02 ms. Functional latent fingerprints (LFPs) were successfully developed using the prepared NMs and NCs, which are capable of emitting green light. CdS-TiO2 exhibits a specific capacitance of 9.92 F/g at a current density of 0.1 mA/g with stabilized GCD profiles, and 90% of its capacity remained even after the 1500 cycles. The highest power density and energy density were found to be 126.7 W/kg and 1.38 Wh/kg, respectively. The prepared NMs and NCs were thoroughly examined for the simultaneous sensing of heavy metals such as Cd and Pb using a simple CV technique, with CdS-TiO2 NCs showing limit of detections (LODs) of 4.35 and 3.47 mu M, respectively. The sensing kinetics and plausible sensing mechanisms were systematically investigated. Finally, prepared materials were examined for the dye elimination process by employing four important industrial dyes: Indigo carmine (IC), Methyl orange (MO), Rhodamine B (RB), and Evans blue (EB). CdS-TiO2 NCs exhibit superior photocatalytic activity for the degradation of EB and IC achieving 98% degradation efficiency and degradation kinetics of 3.03 x 10(-2) and 3.0 x 10(-2) min(-1), respectively. Enduring six cycles of degradation, CdS-TiO2 NCs retained their stability and catalytic activity.