Substrate-immobilized noble metal nanoplates: a review of their synthesis, assembly, and application

Noble metal nanoplates are a unique class of two-dimensional (2D) nanomaterials whose planar geometry serves as one of the most important nanoscale building blocks. Referred to by names such as nanoplates, nanodisks, nanoprisms, and nanotriangles, they offer a distinct and compelling set of physicochemical properties renowned for their plasmonic response and catalytic activity. When immobilized on substrates, these same structures are empowered with new capabilities triggered by synergistic interactions with their support and coupling phenomena activated when adjacent nanostructures are held in place with nanometer-scale spacings. In this review, we bring together an impressive literature dedicated to the synthesis, assembly, and application of substrate-immobilized noble metal nanoplates where we highlight the interplay between the nanostructures and their support as a means for deriving a distinct and diverse product. Methods for obtaining substrate-bound nanoplates rely on colloid-to-substrate transfers or syntheses occurring directly on the substrate-surface and span a wide range of techniques including chemisorption, solvent evaporation assembly, air–liquid interfacial assembly, substrate- and seed-mediated syntheses, electrochemical syntheses, vapor-phase depositions, DNA-assisted assembly, and capillary assembly. Collectively, these techniques realize nanoplate formations that are random, close-packed assemblies, periodic arrays, and three-dimensional superlattices. Nanoplate functionality is demonstrated in sensor applications with a broad range of analytes that include explosives, environmentally persistent pollutants, illicit drugs, and microRNA biomarkers for cancer and cardiovascular disease, with proof-of-concept demonstrations as active plasmonics, skin-mountable sensors, point-of-care diagnostics, and electrochemical reactors. Together, this work demonstrates substrate-immobilized nanoplates as a powerful platform for realizing photo- and chemically-active surfaces of technological relevance.