Spatially selective nanoplasmonic response in Ag embedded GLAD TiO2 nanocomposite thin films

The nanoplasmonic behaviour of Ag decorated TiO2 film structure was spatially varied across the sample surface by utilizing the tailored optical response of the underlying dielectric TiO2 thin film prepared using a novel collimated glancing angle deposition technique (collimated-GLAD). A blue shift in maximum attenuation coefficient region and minimum film transmittance region of the Ag/collimated-GLAD TiO2 nanocomposite coating with increase in height from the evaporation source was detected. The presence of minimum transmittance region was found to have occurred due to localized surface plasmon resonance (LSPR) phenomenon with additional contribution from thin film interference. The measured transmittance spectra showed spatial selectivity in LSPR wavelength of similar to 22 nm with increase in height from the evaporation source. The variation of surrounding medium's (i.e. the TiO2 layer) refractive index (with height from the evaporation source) of the Ag nanostructures was the key factor responsible for the spatially varying nanoplasmonic response of Ag/collimated-GLAD TiO2 film across the sample surface. The Surface enhanced Raman scattering (SERS) characterization of the Ag/collimated-GLAD TiO2 film revealed photocatalysis driven dimerization conversion of p-aminothiophenol (p-ATP) molecules to p,p'-dimercaptoazobisbenzene (DMAB) due to the localized surface plasmons of the film structure along with the substantial enhancement in the Raman peak intensities compared to the blank substrate.

Automated summary

The spatial variation of the nanoplasmonic behavior of Ag decorated TiO2 film structure was achieved by using a novel collimated glancing angle deposition technique (collimated-GLAD) to prepare a tailored optical response of the underlying dielectric TiO2 thin film. The blue shift in maximum attenuation coefficient region and minimum film transmittance region of the Ag/collimated-GLAD TiO2 nanocomposite coating with increase in height from the evaporation source was due to the localized surface plasmon resonance (LSPR) phenomenon and thin film interference. The measured transmittance spectra showed spatial selectivity in LSPR wavelength, and the variation of the refractive index of the surrounding TiO2 layer was the key factor responsible for the spatially varying nanoplasmonic response. The Ag/collimated-GLAD TiO2 film exhibited enhanced Raman scattering and photocatalysis driven dimerization conversion, resulting in the substantial enhancement of Raman peak intensities compared to the blank substrate.