Rhodamine 6G (Sigma Aldrich, Fluorescence bioreagent) dye was used as the Raman probe molecule for SERS measurements and all the measurements were done using the same sample and substrate as used for hydrogen evolution reaction and stearic acid degradation tests after clearing off all the organic matter. These substrates were prepared for SERS measurements by drop casting a mixture of known concentration of R6G, 10 -4 M (20 μL) on the Au@TiO2 core shell thin films. Reference neat R6G Raman substrate is prepared by dropcasting 50 μL of 1M pure R6G dye solution. All the samples were allowed to dry in a desiccator for one full day before measurement. The Raman spectra were recorded on a Horiba XploRA Plus Raman spectrometer equipped with a diode-pumped solid-state laser of 785 nm and a power of 25 mW.