Electrochemical and optical comparison of Cr³⁺, Co²⁺, Ag¹⁺, Hg¹⁺ and Pb⁴⁺ doped WO₃ as a thin layer working electrode for electrochemical sensing

Tungsten oxide (WO₃) is a well-known transition metal oxide that demonstrates stability and non-toxicity in its nanoparticle form. Because of its facile and cost-effective synthesis method, it is a promising candidate for several applications like electrochromic devices, photo catalysts and gas sensors. In the present work, WO₃ nanoparticles were synthesized through a one-step hydrothermal process. Subsequently, the pure WO₃ sample underwent doping with different materials, including Cr^+ 3, Co^+ 2, Ag^+ 1, Hg^+ 1 and Pb^+ 4. The crystallographic properties and phase transitions of the crystalline substances were demonstrated by the structural characterisation of all the as-synthesised materials using the X-ray diffraction technique. The optical properties were explored by UV-visible spectroscopy, revealing the energy band gap from 2.53 eV to 3.75 eV. Field Emission Scanning electron microscopy (FESEM) images depicted the morphological features of the material. The pure WO₃ exhibited a 2D nanosheet structure, while the doped materials displayed morphologies ranging from nanosheets or nanorods to polyhedral sheets. Microstructural analysis by TEM revealed particle size for all samples along with fringes and SAED pattern confirming the presence of respective planes. The electrochemical properties of the synthesized samples were investigated using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV) techniques. This research delves into exploring the electrochemical sensing potential of tungsten oxide doped with chromium, cobalt, silver, mercury, and lead as thin layer working electrodes, driven by the pressing need for advancements in sensing technologies. Through a comprehensive investigation of their electrochemical and optical characteristics, this study aims to discern their suitability for sensing applications, providing insights crucial for future sensor design and synthesis.