Surface‐enhanced hyper Raman scattering in silver colloidal solutions

We report surface‐enhanced hyper Raman scattering (SEHRS) from molecules in silver colloidal solutions using high repetition rate mode‐locked picosecond excitation at 1064 nm. SEHRS was is studied under non‐resonant and resonant conditions by choosing adenine and crystal violet as test molecules. Compared with its SERS spectrum, the SEHRS spectrum of adenine displays strong ‘new’ lines, which, in agreement with theory, in most cases also show up in the infrared absorption spectrum. We also explore the capability of SEHRS for trace detection and demonstrate detection and identification of crystal violet based on its SEHRS signals down to nanomolar concentrations.