Emerging contaminants in aquatic ecosystems demand advanced remediation strategies, with semiconductor photocatalysis standing out as a transformative technology. This review examines material design innovations, focusing on sol-gel, hydrothermal, and ultrasonic synthesis methods that enable precise control over structural properties critical for photocatalytic efficiency. Doping with metals/non-metals and heterostructure engineering are highlighted for adjusting bandgap energy to enhance visible-light absorption. Advanced characterization techniques, including XRD and electron microscopy, reveal correlations between material architecture and performance. Applications encompass solar-driven degradation of pharmaceuticals, antimicrobial surface coatings, and hybrid systems combining photocatalysis with membrane filtration or ozonation. Scalability challenges are addressed through immobilized catalysts and reactor design innovations. Interdisciplinary approaches integrating AI optimization and agro-industrial waste valorization underscore sustainable synthesis pathways. Functionalized materials demonstrate dual utility in environmental and biomedical contexts, while solar hydrogen production aligns with clean energy objectives. Persistent barriers include energy efficiency optimization and long-term catalyst stability. Future research emphasizes adaptive material architectures, circular economy integration, and synergistic coupling with conventional treatment processes. By bridging lab-scale advances with industrial scalability, photocatalysis emerges as a versatile solution for water purification and sustainable resource management, offering a roadmap for addressing complex environmental challenges.

Limited access to analytical instrumentation motivates the development of affordable alternatives. This study describes the construction and evaluation of two ESP32-based optical prototypes: an RGB colorimeter using a TCS34725 sensor and an ultraviolet radiometer using an AS7331 sensor. The RGB device combined a darkened chamber with a mirror-assisted optical path and was evaluated using colored papers and solutions of potassium permanganate, methylene blue, rhodamine B, zinc phthalocyanine, and free-base tetraphenylporphyrin. Paper measurements distinguished colors but differed from nominal RGB codes due to factors as print configuration and paper type. Comparisons with a benchtop spectrophotometer revealed analyte- and channel-dependent linear ranges, with R² values of 0.950-0.999 for selected RGB fits. In a test using an unfocused UV flashlight, the recorded signal decreased with increasing source-sensor distance, exhibiting behavior close to that predicted by the inverse-square law. Solar monitoring yielded temporal profiles qualitatively similar to commercial records obtained at a different location and date. Dedicated applications supported data acquisition, visualization, and storage. Artificial intelligence assisted development under human supervision. The results indicate potential for accessible instrumentation, experimental teaching, and connected monitoring, while emphasizing application-specific calibration and the limitations of the evaluated configurations.