Insights for Realizing Ultrasensitive Colorimetric Detection of Glucose Based on Carbon/Silver Core/Shell Nanodots

On-site and instant glucose sensing is essential for objectively monitoring the change of glucose content that has decisive effects on the normal regulation of carbon metabolism. Colorimetric synergy based on indicators for real-time sensing seemed to be the potential route, but so far it has remained quite challenge to shift down the detection limit in a stable manner. Also, the lack of a direct identification of the underlying detection mechanism especially on the exhibited color change limited their practical use. In this study, the strategy is to employ the carbon nanodots with silver shells functioning as the highly sensitive indicators that enabled realization of the colorimetric sensing of glucose which is caused by oxidation of the surface silver shell observed by the naked eye. These were based on the robust core/shell architectures that allowed an ultralow limit of detection of 87.3 nM for glucose detection through the formation of Ag₂O that led to the obvious particle aggregations, and the results were found to be superior than other reported colorimetric-based glucose sensors by the glucose-oxidase-mediated strategy. Moreover, the reliability tests verified their long-term stability and high resistance for the alteration of environmental pH from 3 to 10 on glucose detection. These features associated with the sound crystalline quality of core/shell nanostructures that could be attributed to the compensation of lattice defects existed in the original carbon nanodots by the Ag-O-C bonding while Ag shells were formed.