2.3.1. UV–Visible Diffuse Reflectance Spectroscopy (UV–Vis DRS)

UV–Vis DRS measurements were used to infer the extent of Au₁₀₁NC agglomeration and to confirm that co-catalysts (rGO and Au₁₀₁NC) did not affect the bandgap of the photocatalyst (AlSrTiO₃). UV–Vis DRS measurements were obtained using a spectrophotometer (Cary 5000 UV–Vis–NIR) fitted with a Praying Mantis Diffuse Reflection accessory (Harrick, DRP-SAP). A PTFE disc was used as reflectance standard. For each measurement, the sample holder was filled with approximately 15 mg of the solid-state sample and the reflectance was measured from 200–800 nm.