Research Activities of Kamat Group at Notre Dame

Semiconductor and noble metal nanoclusters in the nanometer size regime display many interesting optical, electronic and chemical properties that are size-dependent. Such nanoscale materials have potential applications in developing biological nanosensors and optoelectronic nanodevices. A burst of research activity is seen in recent years in the area of synthesis and organic functionalization of different size and shape of metal nanoparticles. The size and shape dependent optical and electronic properties of semiconductor and metal nanoparticles make an interesting case for photochemists and photobiologists to exploit their role in light induced chemical reactions.
Binding a photoactive molecule (e.g., pyrene) to metal nanoparticle enhances the photochemical activity and renders the organic-inorganic hybrid nanoassemblies suitable for light-harvesting and optoelectronic applications. The nature of charge transfer interaction of fluorophore with gold surface dictates the pathways with which the excited state deactivates. Obtaining insight into energy and electron transfer processes is important to improve the charge separation efficiencies in metal-fluorophore nanoassemblies and photocatalytic activity of metal-semiconductor composites. lab

The ability to functionalize gold nanoparticles with photoactive molecules has opened new avenues to utilize these nanoassemblies in light energy conversion systems. By suitably modulating the fluorescence of the surface bound fluorophore these nanoassemblies can be tuned to design sensors, display devices and biological probes. Molecular architecture of inorganic and organic hybrid structure in future will play a crucial role in tailoring the requirements of next generation nanodevices.

Organized nanoassemblies of organic molecules and inorganic nanoparticles after all are the building blocks of nanodevices, whether they are designed to perform molecular level computing, sense the environment or improve the catalytic properties of a material. The key to creation of these superstructures is to understand the chemistry at a fundamental level.

To design heterogeneous assemblies consisting of carbon nanostructures (fullerenes, carbon nanotubes etc) , semiconductor nanostructures, metal particles and sensitizing dyes for harvesting light energy
To understand the properties of a surface bound molecule and obtain valuable information concerning the charge transfer interactions and understand the role of gold nanoparticles in storing and shuttling of electrons.
To improve photoinduced charge separation in donor-acceptor type dyads and triads by binding them to metal nanostructures and/or semiconductor composites
To employ donor-acceptor based supramolecular systems (for example, fullerenes and porphyrins) and molecular clusters for in organic photovoltaic cells.

Kamat, P. V., Photophysical, photochemical and photocatalytic aspects of metal nanoparticles. J. Phys. Chem. B, 2002, 106, 7729-7744 (Feature Article-with citations over 150)

Robel, I., Bunker, B. and Kamat, P. V., SWCNT-CdS nanocomposite as light harvesting assembly. Photoinduced charge transfer interactions. Adv. Mater., 2005, 5, in press.

Hasobe, T., Fukuzumi, S. and Kamat, P. V., Ordered Assembly of Protonated Porphyrin Driven by Single Wall Carbon Nanotubes. J- and H-Aggregates to Nanorods. J. Am. Chem. Soc, 2005, 127, 11884 - 11885.

Barazzouk, S., Kamat, P. V. and Hotchandani, S., Photoinduced Electron Transfer between Chlorophyll a and Gold Nanoparticles. J. Phys. Chem. B, 2005, 109, 716-723.

Hirakawa, T. and Kamat, P. V., Charge Separation and Catalytic Activity of Ag@TiO2 Core-Shell Composite Clusters under UV-Irradiation. J. Am. Chem. Soc., 2005, 127, 3928-3934.

Subramanian, V., Wolf, E. E. and Kamat, P. V., Catalysis with TiO2/Au Nanocomposites. Effect of Metal Particle Size on the Fermi Level Equilibration. J. Am. Chem. Soc., 2004, 126, 4943-4950.

George Thomas, K., Barazzouk, S., Ipe, B. I., Shibu Joseph, S. T. and Kamat, P. V., Unidirectional Plasmon Coupling through Longitudinal Self-assembly of Gold Nanorods. J. Phys. Chem. B, 2004, 108, 13066-13068.

Kamat, P. V., Thomas, K. G., Barazzouk, S., Girishkumar, G., Vinodgopal, K. and Meisel, D., Self-Assembled Linear Bundles of Single Wall Carbon Nanotubes and Their Alignment and Deposition as a Film in a DC-Field. J. Am. Chem. Soc., 2004, 126, 10757-10762.

George Thomas, K. and Kamat, P. V., Chromophore Functionalized Gold Nanoparticles. Acc. Chem. Res., 2003, 36, 888-898 (Review Article)

Hasobe, T., Imahori, H., Fukuzumi, S. and Kamat, P. V., Quaternary Self-Organization of Porphyrin and Fullerene Units by Clusterization with Gold Nanoparticles on SnO2 Electrodes for Organic Solar Cells. J. Am. Chem. Soc., 2003, 125, 14962-14963.

Kamat, P. V., Barazzouk, S. and Hotchandani, S., Electrochemical Modulation of Fluorophore Emission at a Nanostructured Gold Film. Angew. Chem. (Int. Ed.), 2002, 41, 2764-2767.

Nanoparticles and Advanced Materials