A negative feedback loop based on proton-driven in situ formation of plasmonic molybdenum oxide nanosheets

We report a negative feedback loop based on proton-driven in situ formation of plasmonic MoO3−x nanosheets. When the concentration of Cu2+ is below a certain level, the reaction of Cu2+ and glutathione (GSH) produces Cu+ and few protons. However, when the concentration of Cu2+ is above a certain threshold, the reaction of GSH and Cu2+ will generate enough protons in the system to initiate the redox reaction of GSH and MoO3 nanosheets, which generates plasmonic MoO3−x nanosheets. This process in turn inhibits the reaction of GSH and Cu2+, which sequesters the excess Cu2+ from the system. The formation of MoO3−x nanosheets lowers the concentration of protons in solution and turns off the production of MoO3−x nanosheets. More importantly, the threshold concentration of Cu2+ can be easily regulated by changing the concentration of MoO3 nanosheets.