IMX Seminar Series - Functional materials: Exploiting dynamic self-assembly at interfaces

We are interested in dynamic supramolecular systems at interfaces. Research within the Scherman group focuses on the design and development of well-defined molecular and supramolecular building blocks as well as controlled polymer architectures for integration into complex dynamic networks and assembly at hybrid inorganic-organic interfaces. The materials we develop are of great interest for applications in a wide range of areas including catalysis, sensing, smart diagnostics, biomaterials, drug-delivery systems as well as energy harvesting and conversion.
 
The dynamic supramolecular linkages that govern our material assembly processes are based on the host-guest chemistry of cucurbit[n]uril (CB[n]) macrocycles.[1] These robust ~1 nm³ host molecules form dynamic, yet stable, complexes with guest moieties in aqueous media exhibiting extremely high binding affinities. Through fundamental studies we gain understanding how to exploit these macrocycles to bring together a variety of chemical entities through host-guest complexation, including small molecules in solution and at material interfaces such as polymer-polymer, polymer-colloid or colloid-colloid. Moreover, our expertise also extends to the use of CB[n]s as a “molecular glue” to direct and control the self-assembly of metallic and semiconducting nanoparticles (NPs).
 
Unlike other laborious and time-consuming approaches such as surface modification with classical organic ligands, CB[n]s are able to rapidly (< 3 s) and uniformly assemble of NPs in solution, acting as robust molecular spacers for the controlled assembly. We have extensively explored this assembly strategy to construct uniform NP assemblies, which afford plasmonic “hot-spots” of highly controlled geometry, ideal for Surface Enhanced Raman Spectroscopy (SERS) applications.[2] Initially focused on sensing, we have shown utility in quantitative multiplexing for the detection of neurotransmitters in biological fluids such as urine.[3] In addition, we have explored the role of CB[n] within Nanoparticle on a Mirror (NPoM) geometry for controlled alignment of dye molecules within plasmonic nanocavities to facilitate the first room temperature observation of strongly coupled plasmons from single molecules.[4]
 
Expanding the utility of CB[n]-mediated NP assemblies, we sought to explore this motif for ultrafine molecular engineering of photo-active semiconducting NPs through dynamic supramolecular interactions.[5,6] We have demonstrated that these CB[n] spacers can adhere to the surface of semiconducting NPs. This enables efficient joining of two types of chemically-different nanoparticulate building blocks (i.e. metallic and semiconductor) with gaps < 1 nm (below electronic coupling lengths), giving rise to novel inorganic-organic hybrids with controlled optical and plasmonic properties. This CB[n]-mediated hybridisation paves the way for widespread use of the resultant hybrids for long-term, real-time tracking of interfacial charge-transfer processes, i.e. light-driven generation of radicals and catalysis with operando spectroscopies.

Bio: Oren Scherman graduated from Cornell University in Ithaca, New York, with a BA in Chemistry in 1999. He then moved to Pasadena, California, where he completed a PhD in 2004 in olefin metathesis and controlled polymerisation, under the supervision of Professor Robert H. Grubbs at the California Institute of Technology (Caltech). After finishing his PhD, Oren moved to the Netherlands to work on supramolecular polymers with Professors E.W. Meijer and Rint P. Sijbesma at the Eindhoven University of Technology. In 2006, he moved to the University of Cambridge to take up an academic appointment as a University Lecturer and Next Generation Fellow in the Melville Laboratory for Polymer Synthesis in the Department of Chemistry. In 2012, he was promoted to Reader in Supramolecular and Polymer Chemistry and in March 2013, he was appointed as the Director of the Melville Laboratory; Oren was promoted to Full Professor in 2015. During the 2013-2014 academic year, Oren was on sabbatical at Tsinghua University as the Xuetang Visiting Professor in Chemistry. His research focuses on dynamic supramolecular self-assembly at interfaces though the application of macrocyclic host-guest chemistry using cucurbit[n]urils in the development of novel supramolecular systems. The Scherman group exploits control over these molecular level interactions to design and fabricate soft materials with integrated function. Current research topics include microcapsules, drug-delivery systems, conservation and restoration of important historical artefacts and sensing and catalysis using self-assembled nanophotonic systems. Of specific interest is the design of functional soft materials including biocompatible hydrogels for drug delivery applications, tough supramolecular polymer networks and bioinspired supramolecular fibres.