The current article deals with the facile yet novel route to prepare zinc oxide (ZnO) nanoparticles with different weight percentages of chromium as a dopant. The impact of such dopant into the ZnO host lattice is explored in terms of the structural, vibrational, optical, and photocatalytic characteristics. The Bragg reflections in the X-ray diffraction displayed a phase pure wurtzite ZnO hexagonal system. The morphology reflects spherical-shaped ZnO particles in all the systems. The optical analysis ensured a good ultraviolet light absorption and a bandgap energy in the range of 3.30–3.24 eV. The principal Raman vibrations ensured the presence of the wurtzite ZnO crystal structure. The decolorization experiment of methyl green dye with pristine and various chromium-doped ZnO nanoparticles was conducted under the illumination of visible light. The obtained results showed that the incorporation of Cr in the framework significantly improved the photocatalytic performance of ZnO.

Optically transparent ultramicroelectrodes (OT-UMEs) comprising carbon nanotube (CNT) networks on quartz, are introduced and used to monitor quantitatively the interfacial concentration of tris(2,2′-bipyridine)ruthenium(II) during cyclic voltammetry. The OT-CNT-UMEs combine the attractive properties of small-scale electrodes, e.g., high diffusion rates and good signal-to-noise, with the ability to probe electrochemical processes optically, from the rear of the electrode. This enables optical measurements of the solution, close to the electrode surface, without significant interference from absorption or scattering processes.