Temporally fluctuating SERS signals from molecularly-bridged silver nanoparticle dimers and small aggregates
Abstrakt
The preparation, TEM imaging and the measurement of temporally fluctuating (blinking) SERS signals of Ag nanoparticle dimers and small aggregates (trimers to hexamers) bridged by 4,4'-diamino-azobenzene molecules are reported. The dimers and small aggregates were assembled on 3-amino-propyltrimethoxysilane-modified, SiOx coated TEM grids using a three-step Ag nanoparticle-diaminoazobenzene-Ag nanoparticle linking procedure.
The time-evolution of the SERS signal from a selected single dimer and/or small aggregate followed at 10s time-intervals shows temporal fluctuations which manifest themselves as a complex pattern of changes in freguency and reletive intensity, indicating that the SERS signal originating from most of the aggregates probed arose from single linker molecules,or,at most,very few molecules such that the individual photodynamics of the molecules involved was not ensemble averaged. The blinking can potentially arise from one or more of several time-dependent processes including temporal fluctuation of the geometry of the dimer which could lead to changes in the surface plasmon resonance conditions and, consequently, in the SERS enhancement.