Search for: All records

The nanofabrication of periodic arrays of structurally complex oxide nanoshells is demonstrated. The so-formed structures are demonstrated as substrate-confined nanoreactors able to synthesize nanomaterials within their confines.

 

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. 

Colloidal growth modes reliant on the replication of the crystalline character of a preexisting seed through homoepitaxial or heteroepitaxial depositions have enriched both the architectural diversity and functionality of noble metal nanostructures. Equivalent syntheses, when practiced on seeds formed on a crystalline substrate, must reconcile with the fact that the substrate enters the syntheses as a chemically distinct bulk-scale component that has the potential to impose its own epitaxial influences. Herein, we provide an understanding of the formation of epitaxial interfaces within the context of a hybrid growth mode that sees substrate-based seeds fabricated at high temperatures in the vapor phase on single-crystal oxide substrates and then exposed to a low-temperature liquid-phase synthesis yielding highly faceted nanostructures with a single-crystal character. Using two representative syntheses in which gold nanoplates and silver–platinum core–shell structures are formed, it is shown that the hybrid system behaves unconventionally in terms of epitaxy in that the substrate imposes an epitaxial relationship on the seed but remains relatively inactive as the metal seed imposes an epitaxial relationship on the growing nanostructure. With epitaxy transduced from substrate to seed to nanostructure through what is, in essence, a relay system, all of the nanostructures formed in a given synthesis end up with the same crystallographic orientation relative to the underlying substrate. This work advances the use of substrate-induced epitaxy as a synthetic control in the fabrication of on-chip devices reliant on the collective response of identically aligned nanostructures.