Synthesis and surface-enhanced Raman scattering of indium nanotriangles and nanowires

Abstract

Herein, shape-tailored indium nanotriangles and nanowires were synthesized via a modified polyol reduction method. These nanoparticles exhibit local surface plasmon resonance in UV regions, near 345 nm for nanowires and 336 nm for nanotriangles. In this study, we report surface enhanced Raman scattering (SERS) and detection of tryptophan molecules using indium (In⁰) as the enhancing plasmonic nanostructure under non-resonant conditions. Under 632.8 nm excitation, Raman line at 1612 cm⁻¹ for the tryptophan molecules (10⁻⁷ M) deposited on the self-assembled indium nanoparticle substrates show intensity enhancement factor (EF) of ∼10⁴ and ∼10³ for the triangular and nanowire morphology, respectively. The experimental results are in good agreement with the finite-difference time domain (FDTD) simulations of electric field contours, exhibiting manifold enhancement of the electromagnetic field localized at the tips and corners of the indium nanostructures, generating hot spots. The synthesis and analysis of the shape-dependent SERS activity of the anisotropic indium nanoparticles can be utilized for the design of versatile SERS substrates as a promising alternate exogenous contrast agent for enhanced Raman scattering from biomolecules.