ZnO-CeO2 heterojunctions were successfully synthesized utilizing a simple combustion approach employing equimolar solutions of the precursor chemicals. The morphology, content, crystallinity, purity, crystal size and bandgap energy features of the synthesized heterojunctions were carefully investigated utilizing various analytical methods. FESEM investigation indicated a heterogeneous flake or sheet-like appearance, as well as a rough and granular surface for the heterojunctions. XRD study found that the average crystallite size for ZnO-CeO2 heterojunctions was 5.38 nm. The absorbance spectrum showed a peak absorption at 372 nm and a band gap energy value of 2.1 eV. The photocatalytic activity of the synthesized ZnO-CeO2 heterojunctions towards three model dyes, CR, RhB, and MB dyes, were investigated. 

The review article discusses the potential of nano/microstructured metal oxide semiconductors as photocatalysts for degrading microplastics. The recent modifications made to nano/microstructured metal oxides and photocatalytic pathways for converting microplastics into useful products, as well as developments in static metal oxides and dynamic micromachines for photodegradation are reviewed. The review concludes with future perspectives and challenges.

Non-enzymatic biosensors based on mixed transition metal oxides are deemed as the most promising devices due to their high sensitivity, selectivity, wide concentration range, low detection limits, and excellent recyclability. Spinel NiCo2O4 mixed oxides have drawn considerable attention recently due to their outstanding advantages including large specific surface area, high permeability, short electron, and ion diffusion pathways. Because of the rapid development of non-enzyme biosensors, the current state of methods for synthesis of pure and composite/hybrid NiCo2O4 materials and their subsequent electrochemical biosensing applications are systematically and comprehensively reviewed herein.