Multi-mode enhanced Raman scattering spectroscopy using aggregation-free hybrid metal/metal-oxide nanoparticles with intrinsic oxygen vacancies

Abstract

Surface-enhanced Raman scattering (SERS) spectroscopy, with strong and stable signals, was achieved in aqueous solution using colloidal hybrid nanoparticles, consisting of gold nanotriangles (Au NTs) with a nanoscale coating of tin dioxide (SnO₂). The observed strong SERS signals can be attributed to an electromagnetic enhancement from the anisotropic Au NTs, and chemical enhancement resulted from the photo-induced charge transfer from SnO₂ to Au NTs. The latter was enabled by the presence of persistent inter-band levels introduced by the intrinsic oxygen vacancies in SnO₂, as well as by the nanoscale mixing of the two components. Moreover, the intrinsic oxygen vacancies in highly defected SnO₂ nanostructures and the aggregation-free approach underpin the high stability of SERS signals. The multi-mode enhanced Raman signal could be further boosted by in situ UV-irradiation and, as a proof-of-concept application, detection of an explosive marker 2,4-dinitrotoluene (DNT) was demonstrated in aqueous solution, achieving a detection limit down to 6 nM (1 μg mL⁻¹) with a significant signal enhancement of 22 times over and above the SERS signals of bare Au NTs.