In situ dispersion of oil-based Ag nanocolloids by microdroplet coalescence and their applications in SERS detection

摘要

Monodispersity and size uniformity of the nanoparticles coated on film-like nanosensors are critical for detection efficiency. However, there is limited controllability in the dispersion of these nanoparticles during their preparation and surface modification processes. Herein, we have developed a method for the in situ dispersion of surface-modified Ag nanoparticles by controlling microdroplet coalescence, and fabricated surface-enhanced Raman scattering (SERS) films by spin-coating the nano-Ag suspensions. In the dispersion process, a two-plate type microchannel was employed to promote microdroplet coalescence. Under the experimentally optimized conditions, about 88% surface-modified Ag nanoparticles with an average size of 16-19 nm could be in situ dispersed. Upon the deposition of the resulting nanosuspensions on PDMS film surfaces, the films could be used to detect a target analyte, rhodamine 6G (R6G), at a detection limit of approximately 1.0 x 10(-8) mol L-1. The Ag-coated films were also confirmed to be stable and highly reusable.