Photocatalytic materials have emerged as pivotal in addressing global challenges such as environmental pollution, energy scarcity, and industrial sustainability. This review delves into the principles, mechanisms, and applications of photocatalytic systems, emphasizing their roles in photodegradation and renewable energy production. United Nations (UN) specified a guideline for sustainable development strategies. UN determined 17 goals of sustainable development and the services of photocatalytic materials underwent 4 of these goals to reflect the distinguishable interest and importance of different photocatalytic materials in many fields for various purposes. Advances in material design, nanotechnology, and system integration have significantly advanced this field, aligning it with sustainable development goals. Key materials like TiO ₂ , ZnO, g-C ₃ N ₄ , and quantum dots are highlighted for their unique properties and enhanced photocatalytic activity through modifications such as doping, heterostructure formation, and biopolymer-supported photocatalysts. Practical applications in wastewater treatment, hydrogen production, air purification, and carbon dioxide reduction are comprehensively analyzed, with case studies demonstrating the successful photodegradation of industrial pollutants. The review also explores the integration of photocatalysis with renewable energy sources, addressing challenges like charge carrier recombination and photocatalyst stability. Interdisciplinary approaches, including computational modeling and machine learning, are discussed for designing next-generation photocatalysts, aligning innovations with global sustainability initiatives.

The mineralization of five industrial sunlight-exposed wastewater samples was investigated, and the recycling process of ZnO quantum dots (ZQDs) for five reusable times was estimated under the approved Egyptian Environmental Law COD (Chemical Oxygen Demand), which has to be less than 1000 ppm. An improved sol-gel process at a low calcination temperature that ranged between 350 and 450 °C was employed to synthesize ZnO quantum dots (ZQDs). The purity, high crystallinity, and structure of the prepared catalysts were determined by TEM and XRD analysis. The energy bandgap, the crystal size values, and the surface area for Z1 and Z2 were determined based on the TEMs, DRSs, and EBTs, which were equal to 6.9 nm, 3.49 eV, and 160.95 m²/g for Z1 and 8.3 nm, 3.44 eV, and 122.15 m²/g for Z2. The investigation of the prepared samples was carried out by studying the photocatalytic activity and photoluminescence, and it was found that the degradation rate of reactive yellow dye as an industrial pollutant of the Z1 sample was significantly higher than other samples, by 20%. The data collection has shown that photocatalytic efficiency decreases with an increase in the crystallite size of ZQDs.

This article reports on the synthesis, characterization, and application of titanium dioxide quantum dots (TDS) for wastewater treatment. Three TDS samples were synthesized via a low-temperature precipitation method with calcination at 280°C (TDS1), 290°C (TDS2), and 300°C (TDS3). Characterization techniques such as X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed the high crystallinity, purity, and quantum confinement of the TDS with sizes of 3.1, 5.5, and 8.5 nm, respectively. The photocatalytic activity of TDS was evaluated by degrading Congo red dye under xenon lamp irradiation. TDS1, with the smallest size of 3.1 nm and the largest bandgap of 3.09 eV, showed the highest photodegradation rate of 22.49 × 10 ⁻³ S ⁻¹ . TDS1 also showed effective degradation of real industrial textile wastewater under sunlight over nine repeated cycles of use. The antibacterial activity of TDS against Bacillus subtilis and Candida albicans was demonstrated, with the highest inhibition by TDS1 attributed to its higher surface area. Overall, the study shows the high photocatalytic and antimicrobial potential of synthesized TDS, especially the smallest 3.1 nm TDS1 sample. The recycling results also showcase the reusability of TDS for wastewater treatment.