Target-Induced Nanocatalyst Deactivation Facilitated by Core at Shell Nanostructures for Signal-Amplified Headspace-Colorimetric Assay of Dissolved Hydrogen Sulfide

Colorimetric assay platforms for dissolved hydrogen sulfide (H₂S) have been developed for more than 100 years, but most still suffer from relatively low sensitivity. One promising route out of this predicament relies on the design of efficient signal amplification methods. Herein, we rationally designed an unprecedented H₂S-induced deactivation of (gold core)(ultrathin platinum shell) nanocatalysts (Au at TPt-NCs) as a highly efficient signal amplification method for ultrasensitive headspace-colorimetric assay of dissolved H₂S. Upon target introduction, Au at TPt-NCs were deactivated to different degrees dependent on H₂S levels, and the degrees could be indicated by using a Au at TPt-NCs-triggered catalytic system as a signal amplifier, thus paving a way for H₂S sensing. The combination of experimental studies and density functional theory (DFT) studies revealed that the Au at TPt-NCs with only 2-monolayer equivalents of Pt (θ_Pt = 2) were superior for H₂S-induced nanocatalyst deactivation owing to their enhanced peroxidase-like catalytic activity and deactivation efficiency stemmed from the unique synergistic structural/electronic effects between Au nanocores and ultrathin Pt nanoshells. Importantly, our analytical results showed that the designed method was indeed highly sensitive for sensing H₂S with a wide linear range of 10-100 nM, a slope of 0.013 in the regression equation, and a low detection limit of 7.5 nM. Also the selectivity, reproducibility, and precision were excellent. Furthermore, the method was validated for the analysis of H₂S-spiked real samples, and the recovery in all cases was 91.6-106.7%. With the merits of high sensitivity and selectivity, simplification, low cost, and visual readout with the naked eye, the colorimetric method has the potential to be utilized as an effective detection kit for point-of-care testing.