Nanomaterials for photocatalytic environmental remediation: synthesis, mechanism, and performance

Nanomaterials have emerged as efficient photocatalysts owing to their large surface area, tunable bandgap, and superior charge separation properties. This review aims to provide a comprehensive analysis of metal oxides, doped nanostructures, nanocomposites, and heterojunction systems with a focus on their role in degrading organic pollutants and dyes. It highlights how synthesis approaches-classified into physical, chemical, and green methods-affect structural, morphological, and optical properties that directly govern photocatalytic performance. Key characterisation techniques such as XRD, SEM, TEM, UV-Vis DRS, and PL are discussed for evaluating crystallite size, bandgap, surface area, and charge carrier dynamics. The review further details photocatalytic degradation mechanisms, emphasising reactive species generation and electron–hole migration, along with the influence of operational parameters including catalyst dosage, pH, pollutant concentration, light source, and irradiation time. The novelty of this work lies in its comparative analysis of material performance, synthesis-property-activity correlations, and emphasis on sustainable synthesis and scalability. Overall, this study provides valuable insights to guide future research toward developing eco-friendly, practical, and highly effective nanomaterial-based photocatalysts for water treatment technologies.