SERS of organic analyte on the filter paper with TiO2 ALD coating and Ag nanoparticles

Surface Enhanced Raman Spectroscopy (SERS) is an important method for characterizing different materials and chemical analytes at low concentrations.The Raman signal plasmonic amplification is strongly dependent on the surface nanostructure.The filter paper could be used as the substrate for the chemical analysis of organic materials.We investigated the influence of different TiO2 thicknesses deposited on the ashless filter paper surface on the signal efficiency.TiO2 is hydrophilic and biocompatible.High-surface area TiO2 on the filter paper will help create 3D heterostructure to collect more analyte molecules.We used Sentech SI 500 thermal Atomic Layer Deposition (ALD) System with 10, 20, and 50 growth cycles and the TTIP precursor.Surface structure was investigated by Atomic Force Microscopy (AFM).The silver (Ag) colloid solution was dropped on the filter paper before standard R6G biomarker solutions were deposited.The Raman signal measured by In Via Renishaw spectrometer was compared for the different samples.TiO2 ALD-20 cycle gave the highest enhancement factor (~2.3 X 105) compared to other ALD-coated samples.Interestingly, the TiO2 ALD coating generally results in an enhancement factor more than 20 times higher than the reference sample (namely filter paper without the ALD coating).SERS mapping results suggest the uniformity and reliability of SERS measurements across a large area (40 x 40 um2).The finding paves a new direction for preparing simple, flexible, and biocompatible SERS substrates, which could be readily applied in detecting various biomolecular or organic analytes in our coming works.