Synthesis and Functionalization of Stable and Bright Copper Nanoclusters by In Situ Generation of Silica Shells for Bioimaging and Biosensing

Copper nanoclusters have shown tremendous application perspective because of their outstanding luminescence properties, inherent biocompatibility, and easy accessibility; however, low emission brightness and poor resistance to ambient oxygen greatly limit their wide applications in long-term sensing and bioimaging. Herein, we develop an effective and general approach to enhancing the luminescence and stability of copper nanoclusters through in situ generation of a silica shell and further propose a versatile surface functionalization method to achieve functional copper nanoclusters via the formation of a second layer of a silica shell. The use of thiol-containing trialkoxysilane facilitates in situ generation of a silica shell on the surface of copper nanoclusters, and the existence of the first layer of a silica shell substantially improves the emission efficacy of copper nanoclusters. The introduction of a second layer of a silica shell not only greatly enhances the brightness and stability of copper nanoclusters but also provides versatile surface functional groups via hydrolysis and polymerization of trialkoxysilance derivatives with different functionals on the surface of a silica shell. Thiol-functionalized silica-coated copper nanoclusters as a demonstration are used to develop a novel detection strategy for hydrogen sulfide based on disulfide exchange reactions. The excellent analytical performance of the established method proves the feasibility and practicability of functional copper nanoclusters with a core-shell structure in long-term sensing and bioimaging applications.