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 MoO_3-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 MoO_3-x nanosheets. This process in turn inhibits the reaction of GSH and Cu²⁺, which sequesters the excess Cu²⁺ from the system. The formation of MoO_3-x nanosheets lowers the concentration of protons in solution and turns off the production of MoO_3-x nanosheets. More importantly, the threshold concentration of Cu²⁺ can be easily regulated by changing the concentration of MoO₃ nanosheets.