Hydrogen sulphide (H 2 S) is a gaseous signalling agent that has important regulatory roles in many biological systems but remains difficult to measure in living biological specimens. Here we introduce a new method for highly sensitive sulphide mapping in live cells via singleparticle plasmonic spectral imaging that uses Au-Ag core-shell nanoparticles as probes. This strategy is based on Ag 2 S formation-induced spectral shifts of the nanoprobes, which is not only highly selective towards sulphide but also shows a linear logarithmic dependence on sulphide concentrations from 0.01 nM to 10 mM. A theoretical model was established that successfully explained the experimental observations, suggesting that the local sulphide concentration as well as its oscillations can be determined indirectly from kinetic measurements of the spectral shifts of the nanoprobes. We demonstrated for the first time the realtime mapping of local variations of sulphide levels in live cells with nM sensitivity.

We present a high-throughput strategy for sensitive detection of H2S by using individual spherical Au-Ag core-shell plasmonic nanoparticles (PNPs) as molecular probes. This method is based on quantification of color variation of the single PNPs resulting from formation of Ag2S on the particle surface. The spectral response range of the 51 nm PNP was specifically designed to match the most sensitive region of color cameras. A high density of immobilized PNPs and rapid color RGB (red/green/blue) analysis allow a large number of individual PNPs to be monitored simultaneously, leading to reliable quantification of color change of the PNPs. A linear logarithmic dependence on sulfide concentrations from 50 nM to 100 μM was demonstrated by using this colorimetric assay. By designing PNPs with various surface chemistries, similar strategies could be developed to detect other chemically or biologically important molecules.