Interfacial Forces and Novel Self-Assembled Surface Structures

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The research in this proposal explores some of the fundamental processes that take place at interfaces. By interface, we mean the junction between two different phases of matter: here, the liquid-solid interface. The events that take place at solid-liquid interfaces are fundamental to, and indeed often dominate, many chemical processes that are of both academic and practical interest. For example, industrial synthesis of both bulk and fine chemicals; detection of biological molecules in medical devices; and many environmental processes can all take place at a solid-liquid interface.One theme in this research is the detection and separation of chiral molecules. A chiral molecule is one which comes in two forms, which are literally mirror images of one another. The two forms have the same physical properties and so are difficult to detect. However, they react differently if they come into contact with another chiral molecule. Chiral molecules have more than academic interest: just about all biological systems are dominated by them. Consequently, many drug molecules are chiral. For example, the drug salbutamol, or ventolin(TM), used to treat asthma, comes in two chiral forms, referred to as the R- and S-enantiomer, and consists of a 50/50 mixture. The R-enantiomer is the active form, while the S-enantiomer is thought by some to produce many of the side effects associated with the drug. Such behaviour is associated with many pharmacological substances, and therefore developing means of detecting and separating chiral molecules is of great importance. Our research focuses on understanding the fundamental structure-property relationships that underlie the separation of the R and S versions of chiral molecules in a process known as chiral chromatography. Our second research theme involves a previously unrecognized means of modifying surfaces using a process of self-assembly: here, a disordered system of molecules spontaneously evolves into an ordered structure, in this case a single layer (monolayer) of molecules at a surface. Our target class of molecule is called an N-heterocyclic carbene, or NHC. This class of molecule has been known for some time, and is often found as a component of various catalysts. But we have found that it may also be used to form a self-assembled monolayer on Au and potentially other metals, and can profoundly change the properties of the metal – including potential applications in optics, microelectronics and detection technologies. Furthermore, we have found that the carbon-metal bound NHC-based monolayers are potentially far more stable than the current state-of-the-art technologies in this area, which are based on a sulfur-metal chemical bond. NHC-based self-assembled systems are currently a big unknown, but ones which have the potential to revolutionize a number of technologies. In this research, we are intending to focus on both the fundamental aspects of the NHC self-assembly process, and also how an NHC film can be used to replace the sulfur-based chemistry in a biomedical detection technology known as surface plasmon resonance.In summary, interfacial chemistry underlies processes as diverse as purifying mixtures of compounds, the detection of biomolecules, and the production of new photonic and electronic devices. We will address questions that will inform new approaches to these problems as we focus on both the development of new systems of self-assembly on surfaces and methodologies exploring the chemical interactions taking place at these surfaces. At any time, five PhD students and one undergraduate will be engaged in this research, preparing for careers in government or corporate laboratories, business or academia.