In thin film heterojunctions the order of the layers is crucial to obtain a synergistic effect. The layout S-BiOI–BiOBr boosted the photocatalytic activity as light was completely used and the charges were favored to move to the surface and react.

ZnO nanostructures have attracted attention as transducer materials in optical biosensing platforms due to their wide bandgap, defect-mediated photoluminescence, high surface-to-volume ratio, and tunable morphology. This review examines how the dimensionality of ZnO nanostructures affects biosensor performance, particularly in terms of charge transport, signal transduction, and biomolecule immobilization. The synthesis approaches are discussed, highlighting how they influence crystallinity, defect density, and surface functionalization potential. The impact of immobilization strategies on sensor stability and sensitivity is also assessed. The role of ZnO in various optical detection schemes, including photoluminescence, surface plasmon resonance (SPR), localized (LSPR), fluorescence, and surface-enhanced Raman scattering (SERS), is reviewed, with emphasis on label-free and real-time detection. Representative case studies demonstrate the detection of clinically and environmentally relevant targets, such as glucose, dopamine, cancer biomarkers, and SARS-CoV-2 antigens, with limits of detection in the pico- to femtomolar range. Recent developments in ZnO-based hybrid systems and their integration into fiber-optic and microfluidic platforms are explored as scalable solutions for portable, multiplexed diagnostics. The review concludes by outlining current challenges related to reproducibility, long-term operational stability, and surface modification standardization. This work provides a framework for understanding structure–function relationships in ZnO-based biosensors and highlights future directions for their development in biomedical and environmental monitoring applications.

Temephos (Tem) pesticide is a permitted and widely used compound to control vector-borne diseases. Unfortunately, temephos easily undergoes fast photooxidation under ambient conditions, forming more toxic subproducts, which may cause DNA damage with its prolonged use. Semiconductor photocatalysis has proven to be an effective method to degrade toxic pollutants (including pesticides) in water, with zinc oxide (ZnO) being one of the most representative photocatalysts. In this work, the evolution of Tem and three of its principal subproducts (Tem-SO, Tem-dox-SO, and Tem-dox-SO₂) was monitored using high-performance liquid chromatography (HPLC) during a simulated-sunlight photocatalytic treatment using two different ZnO nanostructured morphologies, flower-like (FL) and nanowire (NW) films. ZnO films with NW morphology were three times faster than FL in degrading Tem. NW also degraded Tem subproducts efficiently, achieving a high mineralization percentage. Their large surface area, point defects, and the contribution of Au nanoparticles on the tip of the NWs that possibly produced a surface plasmon resonance effect, enhanced visible light absorption and charge separation. These characteristics all together led to a higher production of hydroxyl radicals responsible for the degradation and mineralization of Tem and Tem subproducts. The monitoring of Tem derivatives indicated that the degradation process occurs in three stages.