A highly sensitive SERS substrate based on a mesoporous Ag–TiO2 thin film for the detection of dye molecules

Abstract

We present a fast, accurate, and molecular specific detection technique of dyes at an ultra-trace level using surface-enhanced Raman spectroscopy (SERS). A highly sensitive Ag–TiO₂ thin film having a nanocage (NC) structure is explored for SERS applications. The facile fabrication method requires significantly less Ag on the TiO₂ nanostructure. The Raman enhancement mechanism of the fabricated film is investigated using two different excitation lasers of 514.5 nm and 785 nm considering both experimental and simulation studies. We obtained a significant enhancement for the 514.5 nm excitation laser as it is closest to the plasmonic resonance wavelength of the fabricated SERS film. We have demonstrated the detection of Rhodamine 6G (R6G) and N719 Ruthenium dyes at various concentrations up to picomolar and nanomolar levels, respectively, using the fabricated SERS substrates. The limits of detection (LOD) of R6G and N719 dyes were calculated to be 3.83 × 10⁻¹² M and 1.58 × 10⁻⁹ M, respectively. Thus, this systematic study emphasizes that the fabricated SERS substrate effectively detects different dyes at low concentrations, and further presents more opportunities for practical applications.