Optical properties of formation of gold nanoparticle aggregates deposited on quartz glass and application to SPR sensing

The sensing of surrounding medium is a research focus, which is highly dependent on the nanotechnology that exhibits typical features of technical difficulty and high price. In this work, a surrounding medium sensor based on gold nanoparticles (Au NPs) is fabricated. The formation of Au NP aggregates is deposited on quartz glass by alternately immerses the glass sheet in positive charged cationic polymer polyethyleneimine and negative charged citrate coated Au NPs. The formation of Au NP aggregates with different numbers of NPs is fabricated controlling numbers of deposition and deposition time. The formation of aggregates contains less NPs exhibit ability of refractive index sensing by monitoring the surface plasmon resonance (SPR) of Au NPs. The formation of Au NP aggregates can be used as a substitute of Au NPs array for the application of SPR sensing for the merits of easy fabrication and low cost.