LSPR Sensor Combining Sharp Resonance and Differential Optical Measurements

A new optical sensor based on the localized surface plasmon resonance (LSPR) in 2D arrays of silver nanoparticles (AgNPs) combined with a differential optical measurement method is developed. LSPR substrates comprised of self-assembled, 2D arrays of AgNPs exhibit coherent plasmon coupling manifested as a sharp peak in the blue spectral region. A bottom-up approach was used to fabricate reproducible and cost-effective substrates with a figure of merit (FOM) of ~24. The LSPR shift was determined by measuring the difference between light extinction at two wavelengths selected on each side of the sharp peak. The sharpness of the coherent plasmon resonance together with the differential measurement method enabled a record sensing resolution in bulk for a LSPR sensor of ~4.8E-6 RIU.