Recyclable SERS substrate: Optimised by reducing masking effect through colloidal lithography

Surface-enhanced Raman spectroscopy (SERS) has attracted much attention as it can deliver "fingerprint" type selectivity and detect organic compounds and other analytes down to single molecules. Conventional methods to produce reliable SERS sensors require high cost and control in the morphology and topology of the sensors. The lack of recyclability makes these high-cost sensors one-time use only. In this research, we have employed unconventional colloidal lithography techniques to develop a reliable and reproducible SERS sensor with self-cleaning capabilities. The sensor is developed via chemical vapour deposition of titania (TiO2) on 2D colloidal crystal monolayers to form Long-Range Ordered Crystals (LROCs) followed by controlled electroless deposition of silver nanoparticles. The fabricated surfaces are highly ordered and reproducible and the topology of the surface is uniform across the surface due to the seamless formation of TiO2/Ag LROCs. The developed sensors have shown self-cleaning properties from their TiO2 based layers and the formation of Schottky heterojunction between TiO2 sublayers and decorated Ag nanoparticles. Thus, the developed sensors show high sensitivity as well as recyclability enabling these sensors to perform multicycle measurements.