Fluorescence Spectrophotometer to Investigate Nanostructures at Interfaces

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Somasundaran, PonisserilColumbia University" Fluorescence Spectrophotometer to Investigate Nanostructures at Interfaces."This project is for the procurement of a Fluorescence Spectrometer, for the Langmuir Center for Colloid and Interfaces of Columbia University, New York, for the research of an interdisciplinary research team, investigating novel nanostructures and their dynamic behavior at various interfaces. The principal investigators who will use this instrument include Prof. Chasin (Biology Dept.), Prof. Gryte (Dept. of Chem. Eng.), Prof. Somasundaran (Earth and Env. Eng.) and Prof. Turro (Chemistry Dept.). Adsorption of nanoscale surfactants and polymers is used for the modification of the surface properties of solids and finds application in many industrial processes such as flocculation/dispersion, deposition, coatings, enhanced oil recovery and flotation. Efficient use of adsorption in these cases depends not only on the amount adsorbed but also on the nano structure of the adsorbed layer in terms of the conformation and orientation of the adsorbed species. Currently there is very little information on conformational aspects of the adsorbed species, mainly due to lack of reliable in-situ techniques. Their earlier work focused on understanding the physico-chemical mechanisms of adsorption of surfactants, polymers and proteins by studying adsorption density, zeta potential, wettability and calorimetric effects. Such investigations have helped in generating a mechanistic picture of the structure of the adsorbed layers. More recently, Turro, Somasundaran and Gryte have collaborated in using fluorescence spectroscopy along with electron spin resonance spectroscopy (ESR) to probe adsorbed surfactant and polymer layers on particles, liposomes, implants etc. These studies have demonstrated the potential of fluorescence spectroscopy to investigate the nano-structure of adsorbed layers. With this new fluorescence instrumentation available, there is an unprecedented opportunity to investigate the conformational aspects of species at interfaces on a sub molecular level (nanoscale). Broader Technical Impact: This instrument will be used to develop a full understanding of the interactions of surfactants and polymers / proteins, particularly the nano-structures of adsorbed layers and colloidal aggregates and the effects of different parameters on the structure. Knowledge about the conformation of the dissolved and adsorbed species and their dynamic behavior will prove useful for developing smart materials responsive to the presence of contaminants, bioagents and perturbations in parameters such as pH, temperature and ionic strength. The instrument will be used ton a multitude of projects, most of which are aimed at improving our understanding of molecularly assembled systems and are important to basic science and advance in technologies. Because the instrument is being shared among several researchers and will be used on several independent projects in different disciplines, it is likely that the spectrophotometer will be used by a large number of students and postdoctoral fellows. The instruments will also offer training opportunities for undergraduates.