Towards green visible range active photocatalytic Au/TiO2 nanocomposites through rutin-based synthesis and their application in the degradation of ciprofloxacin

Photocatalysis is a low-cost solution to efficiently remove resilient emergent pollutants from wastewater with complex chemical structures, such as pharmaceuticals. Titanium dioxide (TiO2) is the most studied photocatalyst and is usually functionalised with gold (Au) nanoparticles to prevent electron-hole pair recombination and extend visible radiation absorption. However, conventional synthesis techniques use toxic chemicals and present high energy consumption. The focus of this work is to present and optimize a green synthesis method using the flavonoid rutin - a natural compound found in various plants - as the reducing agent at room temperature to decrease the environmental impact and optimise the chemical, physical, and photocatalytic properties of Au/TiO2 nanoparticles with concentrations of Au of 0.025, 0.1, and 1 wt%. Through ciprofloxacin (CIP) degradation under UV and simulated solar radiation, enhanced photocatalytic efficiency is observed due to adding Au nanoparticles, proving that rutin is a suitable reducing agent for green nanoparticle synthesis.