Au-TiO2 SPs were drop casted on a precleaned silicon wafer (3 cm × 6 cm) and calcined to 450 °C for 2 hours. This led to an approximate photocatalyst loading of 75 µg cm -2 . Photometric measurements were performed to determine the gold mass concentration per unit volume in the colloids by appropriate dilution to detection limits using the Spectroquant® gold test kit. The coated silicon wafer was kept in a petri dish surrounded by ice and 27 mL milli-Q water with 3 mL methanol (10%) was added to it. The pH of the reaction solution was adjusted using 10mM nitric acid. Suitable light was illuminated onto the sample to produce H2O2. For simulated sunlight AM1.5G filter was used (SciSun-300, Sciencetech) and the intensity amounted to 100 mW.cm -2 (i.e. 1 sun) at the top surface of the silicon wafer. LED light sources were used to illuminate using UV (385 nm) and green light (515 nm). The intensity of UV and green light was kept at 5 mWcm -2 and 25 mWcm -2 respectively. As a reference, hydrogen peroxide generation reaction on blank silicon wafer was performed to omit effects of direct photolysis and heat from light irradiation. Incident light intensity was measured by a calibrated spectroradiometer (Avantes Avaspec-3648-USB2). Hydrogen peroxide measurement was carried out using the KMnO4 titration method. 4.3 Characterization