SERS Activity of Photoreduced Silver Chloride Crystals

Metal nanoparticles are widely acclaimed as plasmonic substrates for surface -enhanced Raman spectroscopy (SERS) due to their unique particle plasmon resonances at visible and near infrared regions. Silver nanoparticles are typically employed in SERS when the targeted Raman signature zone of analytes lies at ultra-violet and/or blue to green spectral regimes. Even though silver has strong plasmonic properties, silver-based substrates are often affected by the atmospheric oxidation and show degradation in their SERS performance. One way to overcome this limitation is to use silver chloride crystals as oxidation resistant intermediate and photoreduce them to 'fresh' silver just before SERS analysis. In this work, we study the SERS activity of the photoreduced silver chloride crystals. We perform Raman analysis of three Raman active analytes, adenine, rhodamine 6G and riboflavin at both visible (514 nm) and near-infrared (785 nm) excitations. Our experimental outcomes show that such photoreduced silver chloride crystals can be exploited as SERS active substrates for both visible and near-infrared applications. Our numerical simulations reveal that these photoreduced silver chloride crystals are strong scatterers at multiple wavelengths and hence, could be very useful for plasmon-enhanced spectroscopic applications where multiple wavelengths are involved.