Chemically Induced Sintering of Nanoparticles.

We have observed solid-state growth of pre-existing silver nanoparticles (AgNPs) upon exposure to trace (ppb) concentrations of reactive gases at room temperature. The consequent change in localized surface plasmon resonances alters the visible absorbance of dried, printed sensor spots made from inks of 10 nm-AgNPs and provides a novel mechanism for trace detection and dosimetry of reactive gases. Colorimetric sensor arrays based on these AgNP inks offer dosimetric identification of acidic and oxidizing gases and other reactive vapors with limits of detection below ppb levels for 1 h exposures. For an array of AgNP inks with various capping agents, a unique color response pattern is observed for each specific analyte. Excellent discrimination among 11 reactive gases was demonstrated using standard chemometric methods. The chemically induced sintering of NPs paves the way for novel solid-state sensors for the ultrasensitive detection of reactive gases and their application to the monitoring of trace airborne pollutants.