Regenerated and reformed gold and titanium dioxide quantum dots from waste for sustainable and efficient environmental monitoring

Driven by the urgent need for sustainable materials in advanced technologies, this study investigates the potential of regenerated and reformed waste materials containing Au and TiO₂ quantum dots (R-Au-TiO₂ QDs), derived from industrial waste, as a viable alternative to commercial TiO₂ (C-TiO₂) for photocatalytic applications. The R-Au-TiO₂ QDs demonstrate a high purity of 99.8 wt% and a particle size of less than 10 nm. The presence of Au (0.24 wt%) further enhances the photocatalytic performance of R-Au-TiO₂ QDs through localized surface plasmon resonance (LSPR), leading to superior degradation rates of methylene blue (MB) when deposited on flexible aluminum foil substrates under UV and solar light. R-Au-TiO₂ QDs achieve a degradation rate of 82.5% with a rate constant of 0.029 min^-1 under UV light, representing a 28% increase in degradation rate and a 70% increase in the rate constant compared to 64.5% and 0.017 min^-1, respectively, for C-TiO₂. Under the solar simulator, R-Au-TiO₂ QDs also outperform C-TiO₂, achieving a degradation rate of 68%, further highlighting their effectiveness. These results are attributed to smaller particle size, higher surface area, enhanced light absorption and improved charge separation in the R-Au-TiO₂ hybrid material. This study demonstrates that R-Au-TiO₂ QDs not only match, but often surpass, the performance of commercial TiO₂, offering a cost-effective and environmentally friendly solution for UV sensing, environmental monitoring, and water purification systems. These findings advocate for the strategic utilization of waste resources containing valuable elements to regenerate high-performance materials, thereby contributing to the development of a circular and sustainable economy.