Six-channel colorimetric sensing of metal ions and advanced molecular information security based on fish scale-derived carbon–gold–silver nanocomposites

Abstract

Due to its high flexibility and expansibility, nanomaterials-based systems have been constructed and applied from sensing, and medicine to molecular information technology. However, the current challenges include tedious and harsh nanomaterials preparation, the need for a wider range of response channels, new information paradigms, higher information density and length. Herein, fish-scale derived carbon nanomaterials (FSCN) were used as reducing and stabilizing agents for direct, green, and facile synthesis of carbon-bimetallic nanocomposites and applications in six-channel colorimetric sensing of Hg2+, and multi-combination and multi-round information encoding and protection for long text. First, the reaction sequence of three precursors (FSCN, Au3+, Ag+) was optimized to prepare FSCN–Au–Ag nanocomposites with double plasmonic absorption peaks of Au/Ag nanoparticles (NPs). The addition of Hg2+ causes the aggregation of nanoparticles and the formation of Ag/Hg amalgam or Au/Hg amalgam, FSCN–Au–Ag NPs were capable of multi-channel sensing (color, absorbance, and peak shift) of Hg2+. Especially, the detection limit of Hg2+ was 8.9 nM based on absorption response in wide wavelength range (456–546 nm), which was at least 6 times more sensitive than that at single wavelength. Moreover, different long text information can be encrypted and hidden in six-channel selective responses of FSCN–Au–Ag NPs-based colorimetric sensing system. By setting the threshold, these selective responses can be abstracted as a series of binary strings and then divided into shorter strings. Utilizing multi-combination and multi-round information coding, these short binary strings can be decrypted and merged into various long text content. This research promotes preparation and multi-purpose application of carbon-bimetallic nanomaterials, which provides new way to improve the sensing sensitivity of nanosystems and also offers new direction for molecular digitization.