AREAS OF INTEREST:

• Nanoparticle Coatings
• Nonlinear Optical Materials
• Nanoparticle Biosensors

RESEARCH:

Daniel's research interests fall into the category of materials chemistry. He is currently working on a few different projects:

I. Nanoparticle Coatings

The Halas group is interested in materials which exhibit interesting optical properties from tunable plasmon resonances to large nonlinear optical response.One system of current interest is the coating of gold nanoparticles with polydiacetylenes. Gold nanoparticles consist of a dielectric core with a thin gold coating. These particles are readily suspended in both organic and inorganic liquids. For this experimentation they have been suspended them in 1,2 dichloroethane. A small amount of diacetylene monomer is added to the solution and irradiate with sirring to prepare coated nanoparticles. This system presents a unique nonlinear-nonlinear composite material which could have very interesting nonlinear optical properties.

II. Nanoparticle Biosensors (with Lee Hirsch)

Daniel is also investigating the use of metal nanoshells in a variety of biosensing systems. These particles possess surface enhanced Raman scattering properties which can be used to monitor very small concentrations of analytes in a system. The goal is to develop a technique through which we can prepare nanoshells that have been functionallized to react with certain analytes to produce detectable Raman signals which can be related to the analyte concentration.

III. Synthesis and preparation of self-orienting polydiacetylene thin films (with M. S. Paley and D. O. Frazier at MSFC-NASA)

This project's goal is to prepare new polydiacetlyene systems which will self orient during photodeposition to yield highly aligned thin films. Photodeposition was developed in 1993 by M. S. Paley and allows for the formation of thin films through the irradiation of a monomer solution through a UV transparent substrate with UV light. After ~12 hours of irradiation, a thin polymer film (~1 µm) forms on the substrate. In addition to masking, it is possible to produce films in any pattern feasible using a UV-laser and a translation stage. Previous work has centered on the formation of amorphous thin films. These, however, do not take advantage of the large third order nonlinear optical properties inherent to a polydiacetylene. It is therefore of interest to form highly aligned thin films directly from solution without the need for external influence such as poling, stretching, or rubbing.

The approach to this work has been to modify the side groups of the diacetylene monomer to include liquid crystalline groups, azobenzene groups, and other moieties which should influence the orientation of the film as it is forming during the photodeposition process.

BACKGROUND:

Daniel graduated with a major in chemistry in May 1999. He has been conducting research in the broad area of materials chemistry for over six years. He has worked for Prof. Gregory L. Baker in the Department of Chemistry at Michigan State University, Drs. Mark S. Paley and Donald O. Frazier at NASA Marshall Space Flight Center, Prof. W. E. Billups in the Department of Chemistry at Rice University, and Prof. Naomi J. Halas in the Department of Electrical and Computer Engineering at Rice University.

CURRENT WHEREABOUTS:

He is now a member of the Whitesides group at Harvard University.