Herein, we present scanning electron microscopy (SEM) correlated dark-field (DF) scattering studies of single gold nanorods (AuNRs). We demonstrate the effect of refractive index variation of the surrounding medium on the localized surface plasmon resonance (LSPR) linewidth in single AuNRs. The LSPR line width remains almost constant while increasing the dielectric constant of the medium, which is further verified by discrete dipole approximation (DDA) calculations. Furthermore, we demonstrate how thiol binding affects the LSPR linewidth of the longitudinal surface plasmon of single AuNRs. The thiol resulted in both a red shift and a strong damping with an increased LSPR linewidth. (C) 2017 Elsevier B.V. All rights reserved.