Chemistry

Our research focuses on fundamental science and engineering questions motivated by the creation of materials on the nanometer scale (1 nm=10-9 m). Our research themes include the synthesis, characterization, and applications of nanoparticles (typically 1-100 nm in size). We are developing chemical methods for synthesizing well defined nanoparticles, including atomically precise nanoclusters, shape- and size-controlled nanocrystals, hybrid nano-architectures, and inorganic/polymer nanocomposites. In-depth characterizations of the physical and chemical properties of nanoparticles and self-assembled nanomaterials are carried out with microscopy and spectroscopy techniques, such as electron microscopy, atomic force microscopy, X-ray crystallography, steady-state and ultrafast spectroscopies, etc. We also develop applications of nanoparticles in areas of catalysis, optics, chemo- and bio-sensing, and photovoltaics, etc.

Raúl Hernández Sánchez's research group is interested in combining supramolecular, inorganic, and materials chemistry to synthesize functional systems that bridge the gap between nanoscale materials and molecular chemistry. Their research is focused on developing new synthetic methodologies to access well-defined nanometer-sized clusters where they can investigate surface structure-function relationships relevant in catalytic and magnetic materials. Other efforts in the Hernández Sánchez (HS) group are aimed at designing and synthesizing structural analogues of carbon nanotubes where exquisite control of the resulting framework allows for properties manipulation.

Students in the HS group will engage in synthetic chemistry and develop familiarity with a range of spectroscopic, electrochemical, crystallographic and magnetic techniques. While rooted in synthetic chemistry, research in the HS group will interface with materials, organic, theory, and physical chemistry.

Saxena Group is focused on developing Fourier Transform electron spin resonance and its application to otherwise inaccessible problems in biophysics. The coupling of electron spin angular momentum to its environment—as revealed by the ESR spectrum—provides rich information about the electronic, structural and dynamical properties of the molecule. Saxena group creates the methods that measure the precise distance between two units in a protein, in order to determine their folding patterns and conformational dynamics. These ESR Spectroscopic Rulers— based on multiple quantum coherences and double resonance experiments—are unique in that they resolve distances in the 1-16 nm length scale even on bulk amorphous materials. Much of this work is based on the use of first-principles theory to develop new experimental protocols and to analyze experimental results.

His group continues to develop applications of these spectroscopic rulers that range from capturing the essence of structural changes - such as misfolding - in proteins, to measuring the atomic-level details of ion-permeation in a ligand gated ion-channel. The main projects of his group include:

• Pulsed ESR methods to measure distance constraints in systems containing paramagnetic metals
• Measurement of structural and dynamical determinants of the protein-DNA interactions and functional dynamics in pentameric ligand gated ion-channels.
• Application of the spectroscopic ruler to measure and predict global structures of nanostructured materials.
• Role of metals in aggregation of Amyloid-β peptide.

In the Laaser Lab, we are interested in developing a physical understanding of how changes at the molecular level translate to the macroscopic properties of responsive polymeric materials. For example, how does a change in charge spacing affect the interactions between charged polymers, and at what point do the polymers stop behaving like isolated chains in solution and start behaving like part of a bulk material? How do orientational changes in single polymer chains propagate through a material to achieve macroscopic ordering? And how do polymeric networks transduce force, to achieve things like mechanochemical responses?

We explore these questions by a number of optical and spectroscopic methods, such as light scattering and Raman and infrared spectroscopy, along with classical materials characterization methods like rheology and electron microscopy. Together, these methods allow us to develop new understanding of the structure and dynamic properties of responsive polymeric materials, and offer students the opportunity to gain broad experience in both physical chemistry and polymer science.