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1. Ultrafast Interfacial Charge Transfer Dynamics in Dye-Sensitized TiO2 nanoparticles The everlasting thrust for cost-effective alternative energy resources is one of the main interests of the group. The research efforts are focused on investigating the dynamics of interfacial charge transfer in donor-p-acceptor chromophore sensitized TiO2 nanoparticles. The idea is to probe the local electric fields in dye-sensitized TiO2 nanoparticles using ultrafast transient absorption spectroscopy and femtosecond fluorescence upconversion. The idea is to use these local electric fields to amplify the nonlinear optical properties of chromophores. (Collaborators- Synthesis of chromophores: Ekkehard Sinn (WMU), Giribabu, L.; Rao, V. J. (IICT, India), Theory- L.G.C. Rego (Brazil)) 2. Highly Efficient Two-photon Materials Hybrid Chromophore/Semiconductor and Chromophore/Metal Nanocomposites Two-photon optical materials with enhanced cross-sections are pursued in my research group especially in the context of their applications in multi-photon imaging and optical limiting. The idea is to apply the principles present in the field of dye-sensitized solar cells towards making better two-photon materials. Here, the focus is on the dye molecules functionalized semiconductor nanoparticles and dye functionalized metal clusters. Main idea of my research group is to use the local electric fields that are prevalent at the interfaces to enhance the TPA cross-sections of stationed chromophores. (Collaborator: Prof Ekk Sinn) 3. Ultrafast and Temperature-Dependent Optical
Properties of Quantum-sized Metal and Semiconductor Nanoclusters Time-resolved
luminescence of quantum-sized gold clusters and semiconductor nanomaterials are being investigated with femtosecond fluorescence
upconversion measurements. Also,
temperature-dependent optical properties of atomically precise metal clusters
are studied to understand the role of core to shell transitions and
exciton-phonon interactions. The studies provide unique aspects during the
evolution of molecule to metal and molecule to semiconductor energy levels.
Interesting fluorescence from quantum-sized gold clusters is
observed which showed larger hot excited state lifetimes. 4. Biophysics via Two-photon Absorption Cross-section and Ultrafast Fluorescence Spectroscopy Novel nonlinear optical and ultrafast spectroscopic
techniques are being employed to study protein
folding and unfolding, metal bonding to proteins. The idea is to probe the
local electric fields with optical spectroscopic techniques to monitor the
biophysical processes. In aiddtion, intrinsic
fluorescence of tyrosine is probed with femtosecond
fluorescence upconversion to understand the structural aspects of protein
folding in the Wilsons disease protein (Collaboration with Prof David
Huffman, WMU). Femtosecond fluorescence anisotropy
measurements are being utilized to understand the auto fluorescence
resonance energy transfer in fluorophore-labeled
proteins. 5. Turn-on Luminescent Sensors for Dissolved Oxygen and Metal Ions Surface states of ZnO nanoparticles are being modified to achieve materials that can work as tunr-on luminescent dissolved oxygen sensors. The applications of these sensors include aviation pressure sensors and oil spill leak. Also, nonlinear optical sensors with turn-off and turn-on two-photon excited fluorescence are being investigated. The main idea is to achieve stand-off detection with multi-photon sensing. Organic dye molecule based sensors are also being investigated in the lab for metal ions, energetic materials and chemical warfare agents. Mechanistic aspects of the sensing are probed with time-resolved spectroscopic techniques. Collaborators
Prof David Huffman Department of Chemistry, WMU Prof Ekkehard Sinn Department
of Chemistry, WMU Prof Sherine Obare Department of Chemistry, WMU
Prof Dongil Lee - Yonsei University S Korea Prof Ronchao Jin - Carnegiel Mellon University - Pittsburgh Dr Lingamallu Giribabu, Indian Institute of Chemical Technology, Hyderabad INDIA Dr V. Jayatirtha Rao, Indian Institute of Chemical Technology, Hyderabad INDIA Prof Valery Bliznyuk, WMU Prof Muralidhar Ghantasala Mechanical and Aeronautical Engg, WMU Prof Tianshu Liu - Mechanical
and Aeronautical Engg, WMU Prof Gellert Mezei Department of Chemistry, WMU Prof
Theodore Goodson III - University of Michigan, Ann Arbor
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