Photothermal heating property of gold nanoparticle loaded substrates and their SERS response

Abstract

Abstract This work describes the preparation of gold nanoparticles on flexible paper- and polymer-based substrates, and demonstrates their photothermally-induced heating property and surface-enhanced Raman spectroscopy (SERS) response. Uniform gold nanoparticles were synthesized under light irradiation and were systematically loaded onto these substrates; they were examined in regards to their heating properties under two different light sources. The temperature of the nanoparticle-loaded substrates steadily increased as a function of the gold nanoparticle loading and light intensity. In addition, these substrates were modified with 4-nitrobenzenethiol (4-NBT) and their SERS responses were monitored as a function of the 4-NBT concentration and light intensity. Furthermore, the SERS effects caused by the light-induced heating were examined, allowing for the proper use of the light source and intensity to minimize negative effects during the SERS measurements. Generally, a significant decrease in the SERS signals and an increase in the background noise were observed upon exposure to high intensities of light; these results were possibly due to the desorption, degradation, or disorder of 4-NBT and/or the annealing of gold nanoparticles on the substrate by the local heating and photo-induced damage. The mild photothermal heating by light sources in the presence of physically adsorbed 4-NBT on the substrates resulted in notable SERS enhancements, presumably caused by the conversion of 4-NBT from the precursor state to the chemisorbed state. As such, understanding light-induced heating on SERS measurements provides insight for designing practical and useful SERS detection systems, minimizing the negative effects and maximizing the positive effects.