Chemistry

We measure several fundamental electronic properties of molecules such as charge transfer and electronic delocalization using a technique known as Stark spectroscopy. Stark spectroscopy involves applying large electric fields to molecules in films or matrices and analyzing the effects of the field perturbation on the absorption or emission spectrum. We have recently focused on the properties of MEH-PPV and other molecules used to make to organic light emitting diodes (OLED's). Stark spectroscopy reveals the mechanism by which a large applied electric field, such as those present in OLEDs, produces undesirable emission quenching and suggests strategies for minimizing this loss of device efficiency through modifications of the polymer structure.

Emission properties of Single Molecules and Aggregates

Recent years has seen a huge growth in the use of organic conjugated oligomers and polymers in the design of light emitting diodes (OLEDs) and photovoltaic cells. When these molecules are placed in thin films to fabricate devices, they typically form aggregates. These confer several desirable properties for device function such as protection from oxidative damage and enhanced charge transport. However, they also typically shift the wavelength of emission to lower energies and often significantly reduce its intensity. Our group is using microscopy and spectroscopy to investigate the relationships between molecular structure and the brightness and photo-stability of molecules in the solid state, both in isolation (i.e. as single molecules) and as aggregates. We are also developing methods to image aggregation in films at high resolution and to follow the nucleation of aggregates in the solution phase. 

Our research program is driven by significant problems in organic, biochemistry, and physical chemistry. Our research in chemical theory and computation is fully integrated in strong collaboration with successful experimental chemists. We have a full range on interests, starting with the development of fundamental ideas on the theory of chemical bonding, and how this information can be used to understand the fundamentals of Lewis acidity and basicity, organic reaction catalysis, organometallic structures, and the bonding and reactions at surfaces. In the field of biochemistry, we investigate the energetics and mechanisms of phosphoryl transfer reactions, and design new antimicrobial agents to light the increasing risk of drug resistant bacterial fungal infections.

Research in the laboratory consists of the development and application of computational methods in collaboration with experimental research laboratories. Our research interests fall into the areas of computational biophysics and computational material sciences.

Some our current research projects involve, studying the transport mechanism of neurotransmitter sodium symporter proteins, where we are simulating in vivo conditions using molecular dynamics simulations to observe changes in conformation of proteins upon substrate transport. We are researching computer-aided drug design by applying free energy calculations to elucidate intermolecular interactions of various substrates and inhibitors with monoamine transporters. We are investigating conformational properties of polyglutamine peptide systems by applying molecular dynamics, using the metadynmics sampling algorithm, to explore the conformational free energy landscape of polyglutamine peptides in solvent. We are involved in the electronic structure calculations of extended solids, where we are applying computational methods to investigate and predict physicochemical properties of materials. We are also studying smart materials such as hydrogels of PNIPAM.

In the past, we have studied antifreeze proteins at ice/water interfaces and interaction of N-acetylglucosamine with chitnase. The folding of small peptides in salt solution, and structure, function, and dynamics of monoamine transporters have been studied as well.

Dr. Madura is also one of the primary authors to the Brownian dynamics program UHBD, which is used to calculate the diffusion-controlled rate-constants for biomolecular encounters.