Surface-functionalized gold and silver nanoparticles for colorimetric and fluorescent sensing of metal ions and biomolecules

Surface-functionalized gold and silver nanoparticles, AuNPs and AgNPs for short, prepared via the modification of organic chelating motifs by covalent or non-covalent bonds, represent an ideal type of hybrid nanomaterials that attract widespread attention because of their outstanding advantages, including exceptional optical, electrical, and photothermal properties, and more importantly, specific surface plasmon resonance (SPR) property in well-dispersed solutions. In recent years, AuNPs and AgNPs modified with functional organic chelating receptors have been extensively studied as robust colorimetric and fluorescent sensors, showing broad application prospects in pollutant detection, trace analysis, and other related research fields. Therefore, this review article outlines various AuNPs and AgNPs equipped with thiol-based organic molecules, amino acids, biomolecules, and fluorophores for colorimetric and fluorescent sensing towards toxic metal ions and essential biomolecules. Certain other types of gold and silver nanomaterials are also covered, such as gold nanoclusters (AuNCs), silver nanoclusters (AgNCs), and silver quantum clusters (AgQCs).