Integrating plasmonic and nanozyme responses of gold nanoparticles for enhancing photothermometric sensing

The plasmonic and nanozyme properties of gold nanoparticles (AuNPs) have an important role in the development of photothermometric sensors. However, when only one of these two properties is utilized to respond to the analyte, it results in inadequate signal amplification and limited sensitivity of the sensors. To circumvent this confinement, we herein integrate the dual-response property of AuNPs, i.e., the plasmonic and nanozyme, to develop a highly sensitive photothermometric sensor. In this work, Hg2+ ions were found could not only induce the glutathione-functionalized AuNPs (GSH-AuNPs) aggregation, but also enhance the peroxidase-like activity of aggregated GSH-AuNPs. Aggregated GSH-AuNPs exhibited a stronger photothermal effect than dispersed GSH-AuNPs, which could serve as an AuNPs plasmonic response-based signal channel. Meanwhile, the aggregated GSH-AuNPs could also more effectively catalyze the 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation in the presence of H2O2 to a bright blue product with stronger photothermal effect (TMBox), which could further serve as another AuNPs nanozyme response-based signal channel. By integrating the signal channels of the two responses, GSH-AuNPs with dual-response exhibit higher sensitivity (∼5-fold) and wider detection range (∼2-fold) than GSH-AuNPs using only the plasmonic response during Hg2+ ions photothermometric detection, demonstrating the potential for enhancing the sensing performance of AuNPs-based photothermometric sensors.