Characterization of Rhodamine 110 adsorbed on carbon-based electrospun nanofibers decorated with gold nanoparticles by Raman spectroscopy and SERS

abstract

© 2019 IOP Publishing Ltd.Surface Enhanced Raman Spectroscopy (SERS) is a powerful analytical technique to study the vibrational properties of target analytes at low concentrations. The implementation of SERS as a routine technique requires the use of novel substrates in which the plasmonic effects of metallic nanoparticles can be overexpressed. In this study, carbon-based electrospun nanofibers (CNFs) obtained from Polyacrylonitrile (PAN), by combining far-field electrospinning with a high-temperature carbonization technique, were used to prepare SERS-active substrates. The surface of the prepared CNFs was modified through an oxidative process; subsequently, amine groups were incorporated via covalent functionalization with 3-aminopropyl-trimethoxisilane (APTMS). Finally, the CNFs were decorated with previously prepared gold nanoparticles (AuNPs) of ~12 nm diameter. SERS-active substrates were tested, sensing the dye Rhodamine 110 at 10-4, 10-5 and 10-6 M using a 514 nm laser line. Scanning electron microscopy, Transmission electron microscopy, Raman spectroscopy and UV-vis spectrophotometry were employed to characterize the SERS-active substrates as well as the pristine CNFs and the AuNPs. Additionally, vibrational calculations of Rhodamine 110 were carried out by using ab initio DFT calculations, based on the B3LYP/6-311++G(d, p) method, to gain insight into its spectral properties. Assignment of normal modes was carried out using the simulated Raman spectrum. Furthermore, a comparison between the normal modes and the SERS measurements are presented. The proposed modification on CNFs is expected to allow for a more controlled nanoparticles distribution in order to improve sensitivity and high-speed monitoring at low concentrations.