Nanoparticle Chemical Sensors: A Study on Optical Humidity Sensor Design
The need for sensors capable of operating in harsh environments such as those containing flammable, corrosive or reactive vapors is a niche which thin-film optical devices, with their robustness and ease of maintenance may effectively fill. Two such systems were developed using spin-coating techniques and evaluated for applicability as humidity sensors. The first is based on aggregated silica nanoparticles. The second is a polyelectrolyte multilayer film impregnated with silver nanoparticles which exhibited strong surface plasmon response. Ellipsometric experiments performed using a sealed test cell with constant humidity maintained using saturated salt solutions showed that the former responded strongly to changing humidity. The latter possessed interesting hysteresis behavior as analyzed in a climate-controlled glovebox via reflectometry, but proved insufficiently responsive to changing humidity. The silica nanoparticle substrate was found to be a simple, tunable sensor platform which may be viable for the detection of a wide variety of vapor-phase chemical species.