Somasundaran This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119).

Research in nanotechnology has to date concentrated mainly on the equilibrium properties and behavior of nano-systems, with the dynamics of the system rarely studied. This study is based on the conviction that elucidation of the basic mechanisms of dynamics will help in developing materials of the future which will have an inherent smartness built into them. For example, adsorbed polyacrylic acid structures will undergo coiled to stretched/dangling conformational changes upon changing the pH. This can produce a marked response in the dispersed state of suspensions. This project will focus on the dynamic behavior of novel nano-structures and their active groups as a function of electrical, chemical, magnetic, thermal and optical fields.

Some of the topics to be evaluated are 1) how the conformation of polymers changes and how rapidly they do so under changing pH, thermal, electrical, optical, magnetic and acoustic fields, 2) how the response of the active groups can be manipulated to develop novel structures, 3) how the properties of the nano-composites change as a function of their structure if a sinusoidal field is applied during the preparatory stage, and 4) what happens if variations and perturbations in the field take place after the preparation.

The general methodology involved is to add a probe to a target molecule, which would respond to external perturbation vectors. This response would induce conformational changes in the adsorbed target molecule which will be followed in real time. For changes in pH we have carboxylic acid groups as probes, for magnetic field we will use aqueous ferro-fluids (hematite nanoparticles stabilized by surface active agents) and for optical perturbation we will use "azo" groups. These will be adsorbed on surfaces of silica (for AFM), gold (for SPR), and alumina (for ESR and fluorescence) functionalised for the binding of the modified macromolecules.

The first stage of the research project involves synthesis of macromolecules incorporated with these probes. In the second stage, the dynamics will be studied using AFM, ESR, SPR and fluorescence spectroscopic techniques, while the molecules are being perturbed. It is the final goal to use the information gathered in the second stage to build novel nanomaterials with controllable properties.

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Columbia University
New York
United States
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