Chemical Sensing on a Single SERS Particle.

We report a new chemical sensing platform on a single surface-enhanced Raman scattering (SERS) particle. A cabbage-like Au microparticle (CLMP) with high SERS enhancement was applied as an ultrasensitive SERS substrate. A new Raman reporter bis[4,4'-[dithiodiphenyl azo-phenol] (DTDPAP) was synthesized to display multiple fingerprints and high reactivity toward sodium dithionite. The reaction of DTDPAP with sodium dithionite was in situ monitored by SERS on a single CLMP. The DTDPAP fingerprint change is dependent on the sodium dithionite concentration, providing a simple and sensitive method for sodium dithionite profiling.