Colorimetric/Fluorescent Sensing of Metal Ions and Advanced Molecular Information Safety Based on Fish Scale-Derived Carbon–Gold Nanocomposites

It is valuable to develop simple and environmentally friendly methods for converting biowaste into functional nanomaterials with multiple applications. However, there are few reports on the facile preparation of multifunctional carbon–metal nanocomposites based on biowastes and their application from sensing to information technology. Herein, we used fish scale-derived carbon nanoparticles (FSCN) as reducing agents to directly and facilely prepare multifunctional carbon–gold nanocomposites (FSCN-AuNPs) in one step. Our prepared FSCN-AuNPs have multisignal response capabilities and can be used for colorimetric and fluorescence quantitative sensing of Pb2+ and Cu2+ with detection limits of 86.29 nM (for Pb2+) and 53.74 nM (for Cu2+), respectively. Additionally, FSCN-AuNPs can detect Pb2+ in milk and serum, as well as Cu2+ in water and serum. The multisignal selective responses of FSCN-AuNPs can be converted into binary strings by setting thresholds, which were further applied to encrypt and hide two types of information (like text and two-dimensional pattern information). Overall, this research not only promotes the preparation and comprehensive application of multifunctional carbon–metal nanocomposites but also accelerates the cross-integration of molecular science, such as the integration of molecular sensing and molecular information science.