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Current Research

Novel Biodetection Methods

The object of this project is to find a method to enhance the sensitivity of biological assays. We label the molecule of interest - for example, a nucleic acid or protein - with a polymer nanoparticle which contains a huge number of signal producing units that can be detected via fluorescence spectroscopy (a technique that involves using a beam of light, usually ultraviolet light, that excites the electrons in molecules of certain compounds and causes them to emit light of a lower energy, typically visible light).  The work involves the synthesis of polymers that contain luminescent ruthenium and iridium to ultimately form nanospheres and investigates the conditions - solubility, stability, etc - that have to be met if the nanospheres are to act as the biological labels.

 

Laser Flash Photolysis and Organo-metallic Bonds

Laser flash photolysis (LFP) is a common method to probe photochemical reactions. If the molecules of a sample of interest can absorb the energy from a short pulse of laser light at a particular frequency they will be activated into excited states. The activation will result in fluorescence and/or the dissipation of heat. The phenomenon is best observed by spectroscopic techniques. This work investigates how LFP can help us understand better the strength and reactivity of metal-aromatic bonds in a variety of organo-metallic complexes formed from an organo-metallic precursor and an appropriate aromatic hydrocarbon (arene).

 

Lipophilic Metathesis Catalyst

Metathesis is an organic reaction, catalyzed by metals such as nickel, tungsten, ruthenium and molybdenum, which redistributes fragments of an organic molecule to make a desired alternative. The procedure is now an essential polymer chemistry tool.  Current work emphasizes the synthesis of a catalyst most suitable for a particular process, for example the production of polyethylene.  The project investigates a new generation of metathesis catalysts, related to hydrocarbon based systems that promote the carbon ring opening and ring closing of parent cyclic organic molecules.

 

Nobel Gas Tracers

The project explores and develops techniques to detect isotopes of the noble gases (for example, argon, krypton, xenon) using laser beam spectroscopy, and hence explores the capability of the gases to act as tracers to probe the structure of gas and oil deposits.  The project will further investigate procedures to inject and extract the tracers from a given oil/gas reservoir.

 

DNA-Mimetic Polymers

The term molecular recognition refers to the specific interaction between two or more molecules through noncovalent bonding such as hydrogen bonding, metal coordination, hydrophobic forces and van der Waals forces.  Molecular recognition is the significant characteristic of DNA with its defined sequence of reactive sites. Constructing a synthetic DNA-like (DNA-mimetic) molecule has been a goal for many years since the ability to have a molecule that can template a sequence of controlled sites would be a most powerful tool in synthetic and polymer chemistry. Conventional synthesis of DNA-mimetic molecules, however, faces many challenges because it is a laborious procedure and the products are unstable. We work, however, on a novel method to copy the information contained in DNA onto fully synthetic polymers, using a combination of molecular recognition, self-assembly and synthetic polymer chemistry. Hence we construct an entirely novel class of "DNA-mimetic" polymers which show the specificity and monodispersity of the parent DNA molecule, yet possess the desirable properties of synthetic polymers, such as stability, ready synthesis, facile functionalization and improved processibility. Specifically, this method involves the assembly of monomeric units on their complementary positions on a DNA or peptide nucleic acid backbone, followed by locking the monomeric units into a new synthetic polymer. Many applications are anticipated. Unlike conventional polymers, these molecules present the opportunity to precisely position materials into monodisperse, well-defined and programmable structures. Thus, challenges in the creation of devices for solar energy conversion, light-emitting diodes, data storage or patterning of electronic components can be addressed. And there are biological applications: the synthesis of stable, inexpensive and cell permeable gene regulating drugs and DNA delivery agents are examples. On a fundamental level, this work is the first study of the DNA-templated access to fully synthetic polymers, and is expected to significantly expand the field of synthetic polymer chemistry. Thus, the research is predicted to have far-reaching fundamental and practical impact.

 

Olefins and Nickel Dithiolenes

There is an enormous industrial demand to provide an industrial technology that will reduce significantly the cost of production of olefin feed stokes, the most important of which is ethylene. Typically, olefins are produced from petrochemical sources which are contaminated and thus require purification. Experiments have indicated that the reaction of olefins with nickel dithiolenes (a nickel sulfur organic molecule complex) is a purification route with several significant benefits, such as resistance to acetylene poisoning as well as simple electrochemical control, making it a potentially critical new technology. In particular, an efficient electrochemical route for the purification of olefins based on their reactions with nickel dithiolene has been proposed in the literature, specifically that a mixture of olefins and impurities could be separated through selective olefin binding by the nickel dithiolene 1CF3. It was shown experimentally that the olefins are bound by the nickel structure, while various common impurities (H2O, CO, acetylene, etc.) are not. The newly formed complexes could then be separated from the impurity-bearing mixture, and the olefin subsequently released through electrochemical means, providing purified olefins. However, further research into this reaction is required before it can be converted into an industrial technology. This is our project. There are two primary goals. First, to elucidate the mechanism of this technologically important reaction through quantum mechanical wave function and density functional theory methods. Second, to provide a critical evaluation of new density functionals' efficacy in modeling a difficult problem, and develop further techniques for studying these types of systems.

 

Organotrifluoroborates

Developing new synthetic methods is central to advancing synthetic organic chemistry, which in turn enables chemists to make a wide range of organic molecules relevant to, for example, medicine, biochemistry, catalysis, materials science, and polymer science. This project aims to create an entirely new approach to synthesize compounds with elusive carbon-carbon bonds. The approach is based on some features of organotrifluoroborate chemistry that were recently discovered by Professor Gary Molander’s group at the University of Pennsylvania.   In collaboration with Professor Molander, the research project seeks to explore the best methods to prepare certain organotrifluoroborate compounds and, subsequently, investigate how those compounds relate to carbon-carbon bond forming reactions. If, indeed, a synthesis with organotrifluoroborates can be shown to be both high yielding and broad in scope, this novel approach will have a significant impact on the scope of modern organic synthetic chemistry.

 

Phase Transfer Activation of Catalysts

This project develops and applies a new protocol for catalyst activation, termed "phase transfer activation." The protocol is applicabale to the numerous catalyst precursors from which a group or ligand must first dissociate before the catalytic cycle can be entered. Initial studies target olefin metathesis catalysts which are used to: (1) optimize propene vs. ethylene/butene ratios from refineries; (2) manufacture polymers from cyclic olefins; and (3) prepare many pharmaceutical intermediates. Efforts will then be directed at new nickel ethylene polymerization catalysts.

 

Metal Oxides and Metal Oxide Interfaces

Currently almost all electronics are silicon based, although the search for materials which have novel properties and/or are more efficient is ongoing. For example, systems of complex oxides - particularly the heterointerfaces between different oxides - have been suggested as successors to silicon.  Indeed we know that complex oxide interfaces have a number of unique properties which have been measured experimentally, but the theoretical underpinning of their behavior is still under discussion; hence this project.  In our work we consider the compound lanthanum aluminate (LaAlO3), which can form a conductor when grown on the surface of strontium titanate (SrTiO3), as a possible building block for a metal oxide generation of electronics. We will elucidate the behavior and properties of this system via computational modeling. We will, in particular, carry out calculations employing periodic boundary conditions with screened hybrid density functional theory. Other techniques, such as adaptive numerical thresholds and techniques for efficiently modeling defect structures are to be developed as part of the project.

 

Quantum Entanglement, Communications

Quantum entanglement is a characteristic of a quantum mechanical state (for example the distribution of electrons around the nucleus) of a system of two or more objects in which the quantum states of the constituting objects are linked together so that one object can no longer be adequately described without full mention of its counterpart - even though the individual objects may be spatially separated.  This project aims to understand better how quantum entanglement impacts quantum cryptography communications (a branch of quantum information science).  Quantum cryptography uses quantum mechanics to guarantee secure interactions in that it allows two communicating users to detect the presence of any third party.  This feature arises from a fundamental aspect of quantum mechanics, namely that the very process of measuring a quantum system disturbs the system.  Thus any third party trying to eavesdrop on the key must in some way measure it and will introduce detectable anomalies.

 

Nonlinear Photonics and Telecommunications

The project is concerned with the relationship of nonlinear photonics (the emission, amplification, transmission, manipulation and detection of light) in optical telecommunication technology involving, especially, the behavior of laser light in crystal media. Topics include studies of wave guides and light beam control systems and the effect of optical instabilities on transmission. Particular emphasis is given to the study of the space-time behavior of laser beams in various crystalline media and configurations.

 

Applications of Quantum Interferometry

This project explores an advance novel techniques for precision measurement and sensing using the notion of quantum interferometry and coherence. Such techniques have found important applications in both fundamental and applied sciences. On the one hand, for example, the quantum eraser sheds new light on the foundations of quantum mechanics. On the other hand, techniques based on quantum interference lie at the foundations of quantum microscopy, quantum state measurement and quantum lithography. In this project, we extend many of these techniques and analyze practical systems and devices. In particular, we investigate the applications of quantum interferometry and coherence in precision imaging devices based on quantum lithography, sensing of weak signals such as gravitational waves, design of time-delay devices for information storage and optical devices for sub-wavelength patterns over large areas on photosensitive substrates. This project addresses certain fundamental issues, the first of which  relates to the precision with which one can resolve two objects such as two atoms. This problem lies at the heart of microscopy (or more precisely nanoscopy) with applications in quantum computing and informatics. Conventional methods provide a resolution limit of #/2 where # is the wavelength of light used to probe objects. We have proposed a scheme where this resolution can be improved up to #/500. In this project we shall consider experimentally viable schemes that should make our scheme realizable. A resolution of the order of #/500 should have a substantial impact in the field of nano technology. This is also most relevant to the question of how precise patterns can be drawn using lithography which, again, is at present limited to a resolution of #/2.

 

Nanomagnetism nanomaterials modeling

The growing interest in the field of spin-based nanoelectronics, of great importance to the field of communications, has generated a demand for nanojunctions made up of multifunctional materials that combine ferro and ferrimagnetism with additional desirable properties. Most of nanojunction materials in actual use present limitations due to a variety of problems including growth difficulties and low Curie temperatures. But an area where a novel and promising approach is being increasingly addressed concerns the class of spin filters based on ferro and ferrimagnetic insulating nanojunctions. Our scientific proposal intends to establish sound theoretical models in this domain to support experimental and industrial research. Our research program will focus specifically on investigating the spin wave and spin field transport, between contacts in a given system, via nanojunctions that combine ferro and ferrimagnetism with insulating behavior.

 

Correlations in fullerene layers

Layers of fullerene molecules adsorbed on metal surfaces have attracted much attention due to interesting physical properties such as structural and magnetic phase transitions, and also for the potential use of these materials for device applications. Recent experimental work shows macroscopic lattice distortions [Science 310, 468 (2005)], which it is suggested are a manifestation of cooperative JT effects (CJTE) coupling electronic motion and intermolecular vibrations. To understand these distortions, we must model interacting JT centres on a 2-dimensional (2D) lattice. The CJTE in 3D is usually considered within the mean field approximation (MFA). However, this neglects important correlations between the different distortions in icosahedral symmetry. We therefore propose an alternative procedure for 2D lattices in analogy with the methods used successfully for 2D magnetic systems. A pseudo vector spin S will be introduced to describe equivalent JT distortions within an effective field theory approach. Our goals are to understand these mesoscopic layers adsorbed on metal surfaces with or without defects.