Aggregation of Individual Sensing Units for Signal Accumulation: Conversion of Liquid-Phase Colorimetric Assay into Enhanced Surface-Tethered Electrochemical Analysis

A novel concept is proposed for converting liquid-phase colorimetric assay into enhanced surface-tethered electrochemical analysis, which is based on the analyte-induced formation of a network architecture of metal nanoparticles (MNs). In a proof-of-concept trial, thymine-functionalized silver nanoparticle (Ag-T) is designed as the sensing unit for Hg²⁺ determination. Through a specific T-Hg²⁺-T coordination, the validation system based on functionalized sensing units not only can perform well in a colorimetric Hg²⁺ assay, but also can be developed into a more sensitive and stable electrochemical Hg²⁺ sensor. In electrochemical analysis, the simple principle of analyte-induced aggregation of MNs can be used as a dual signal amplification strategy for significantly improving the detection sensitivity. More importantly, those numerous and diverse colorimetric assays that rely on the target-induced aggregation of MNs can be augmented to satisfy the ambitious demands of sensitive analysis by converting them into electrochemical assays via this approach.