Functional Materials Based on Well-Defined Colloidal Nanoscale Blocks for Applications in Sensing, Photoelectrochemistry, and Environmental Remediation

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The proposed research is aimed at further advancement of the synthesis and characterization of tailorable (by size, shape, surface, and physical properties) nanoscale building blocks (NBBs) and specifically at the realization of functional applications of these NBBs. Targeted applications include sensing based on plasmonic resonance and surface-enhanced Raman scattering (SERS), photoelectrochemistry, photocatalysis, and environmental remediation.**During the last 6 years, the PI's laboratory established a proven track-record in synthetic control over size- and shape-controlled nanoscale building blocks (NBBs) with the emphasis on optimization of functional properties, such as tuneable surface plasmon resonance (SPR). The novelty and utilizable functionality of the developed NBBs originate from the achieved precise control in size, shape, and surface chemistry imparted by the bottom-up colloidal synthesis. Specifically, for SPR sensing, the PI's group synthesized silver pentagonal rods and platelets with the precise position of SPR resonance within a few nm through the size control in the NBB colloidal growth; while optimized size-selection of silver decahedra resulted in the remarkably sharp SPR peak width, crucial for the sensitivity of SPR sensing. For surface-enhanced Raman spectroscopy (SERS) applications, the size control of the silver nanoparticles, and especially the precise synthetic tailoring of the nanoscale cavities (5-50 nm) of the developed regular faceted morphologies, were crucial to demonstrate remarkable SERS enhancement by single silver nanoparticles. Consequently, the next phase of the proposed research is to expand the range of NBBs expanding on the range of their useful functional properties and to focus on realization of their applications (SPR, SERS) . **Three major directions of the proposed research are i) further development of plasmonic NBBs with stability and SPR properties tailored for specific applications; ii) synthesis of novel electron-rich oxide NBBs for photoelectrochemical applications; and iii) production of prototype sensing devices based on the developed NBBs. *i) For the stability of silver NBBs, the research team will first develop their coating with gold to take advantage of gold stability, while retaining advantageous plasmonic properties of silver. Secondly, the team will work on encapsulation of NBBs with silica and polymers for improved stability and tailorable plasmonic properties. *ii) For the conductive oxide NBBs, the team first started with ruthenium and iridium dioxides and subsequently changed the emphasis to cost-advantageous 3d metals, such as manganese and iron oxides. The team aims at realizing tunable advantageous properties in the vicinity of the metal-superatom transition (at ca. 20-200 atoms clusters). *iii) For the implementation of NBBs applications, the research will focus on prototype development of sensors based on SPR and SERS in collaboration with other research groups and industrial partners. Primary NBBs for SPR sensing include gold-plated and shell NBBs. *The PI's group is currently in the best position to accomplish these goals with the attained synthetic library of NBBs.**Tangible benefits of the proposed research are in capitalizing on the developed expertise and capabilities in the synthesis of NBBs and further applying this knowledge to create novel materials where precise size- and surface-control is absolutely critical for the realization of advanced functional properties and applications. The range of applications based on the developed NBB-based materials includes plasmonic and SERS sensing, photoelectrochemistry, anodes for water splitting, and environmental remediation based on oxidative catalysis. SPR sensing will be the primary immediate focus.