IISER - TVM
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Indian Institute of Science Education and Research Thiruvananthapuram
GST ID : 32AAAJI0299R1ZS

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Faculties

Prof K.George Thomas

Professor

Email : a2d0QGlpc2VydHZtLmFjLmlu , Phone :  +91 (0)471 2778040

Web Link  : http://www.iisertvm.ac.in/~kgeorge

Research Areas

Dr. K. George Thomas has made significant contributions in several areas of photosciences and nanomaterials which include design and study of photoresponsive nanomaterials, 1-7 photosensitizers ,8 photoswitchable molecular systems 9 and fullerene based donor-acceptor systems. 10 Recently he has investigated the self-organization of molecules on surfaces and modulated their organization by introducing various functional groups. 11 He is one of the inventors of several technologically important near-infrared absorbing sensitizers, for which an international patent was granted. 12 These dyes are promising candidates for biological imaging and optical data storage applications.

Photoresponsive nanomaterials 1-7 : His recent efforts in the area of photoresponsive nanomaterials are focused on (i) understanding the interfacial properties of hybrid nanomaterials, 1,2 (ii) integrating nanorods and spheres into higher order assemblies, 3-5,7 and (iii) use of such functionalized nanomaterials as sensors, 5 light-induced controlled release systems 4 and nanophoshors 6 .

Various types of chromophores (for e.g., pyrene, fullerene, spiropyran, tris(2,2'-bipyridine) ruthenium(II)) were functionalized on the surface of gold nanoparticles and investigated the ground as well as excited state interactions between the metal surface and the chromophoric systems . 1 Based on these studies it is concluded that the metal nanoparticles possess unique ability of modulating the photophysics of surface bound fluorophore, in contrast to bulk metals. Such systems may have potential applications as photocatalysts and light harvesting devices.

More recently candidate's group has adopted a new paradigm for tuning the optical properties of gold nanorods by organizing them using electrostatic/supramolecular/covalent approaches. 3,5,7 The experimental verification of interplasmon coupling in Au nanorods was first demonstrated by his group by integrating nanorods as one-dimensional assemblies (nanochains). Further this strategy was utilized for the selective detection of micromolar concentrations of cysteine/glutathione in the presence of various other a -amino acids. 5 His efforts in the area of gold nanorods have gained international attention among chemists and biologists working in the area of nanoscience. Experimental verification of enhanced potential at the edges of anisotropic nanomaterials such as Au nanorods was first demonstrated by Candidate's group. Based on this, a novel methodology for the preferential end functionalization of Au nanorods with nanoparticles was reported by exploiting the electrostatic attractive interactions. 7 Dr. George Thomas and his group have demonstrated the potential applications of functionalized nanoparticles as nanodevices. 3-7 For example, they have demonstrated the potential applications of chromophore functionalized metal nanoparticles in the design of sensors for metal cations, 4a light-induced controlled release systems for aminoacids such as DOPA 4b and nanophoshors. 6 The light-regulated changes in the topographic properties of spiropyran-capped Au nanoparticles (i.e., interconversion between the zwitterionic and neutral forms) were exploited for the assembly and release of amino acids such as Ltryptophan, L-tyrosine, L-DOPA and a -methyl-L-DOPA.

Photoswitchable molecular systems 9 : Dr. George Thomas and his group have also designed bichromophoric systems, which can fold and unfold by varying the solvent polarity or by the application of external stimuli such as heat or light. Folding-unfolding processes in these molecular systems were studied, in detail, using steady-state absorption and time-resolved fluorescence spectroscopy and were found to be completely reversible.

Fullerene based donor-acceptor systems 10 : He has earlier demonstrated a novel approach for charge stabilization by taking advantage of the clustering behavior of fullerene derivatives 7 and by tuning the forward and back electron transfer processes. The rate constant for the charge recombination is two to three orders of magnitude lower than those of charge separation in these systems. They are promising material for designing artificial photosynthesis-based device applications.

Organization of molecules on surfaces 11 : Dr. George Thomas and his group have also investigated the selforganization of molecules such as substituted phenyleneethynylenes on two dimensional surfaces using Scanning Tunneling Microscopy (STM). The organization of these systems was modulated by varying the length of thealkoxy group and introducing various functional moieties.

REFERENCES
  1. (a) K. George Thomas and P. V. Kamat, Acc. Chem. Res. 36, 888-898 (2003). (b) K. George Thomas, B. I.Ipe and P. K. Sudeep, Pure & Appl. Chem., 74, 1731-1738 (2002). (c) K. George Thomas and P. V. Kamat,J. Am. Chem. Soc., 122, 2655-2656 (2000).
  2. (a) B. I. Ipe and K. George Thomas, J. Phy. Chem. B. 108 13265 (2004). (b) P. Pramod, P. K. Sudeep, K.George Thomas and P. V. Kamat, J. Phys. Chem. B. 110, 20737-20741 (2006). (c) .R. Vinayakan, T.Shanmugapriya, P. V. Nair, P.Ramamurthy and K. George Thomas, J. Phys. Chem. C. 111, 10146-10149 (2007).
  3. K. George Thomas, S. Barazzouk, B. I. Ipe, S. T. S. Joseph, P. V. Kamat, J. Phys. Chem. B 108, 13066(2004) (cover page of the issue). S. T. S. Joseph, B. I. Ipe, P. Pramod, K. George Thomas, J. Phys.Chem. B. 110, 150-157 (2006).
  4. (a) K. Yoosaf, B. I. Ipe, C. H. Suresh and K. George Thomas, J. Phys. Chem. C. 111, 12839-12847 (2007);(b) B. I. Ipe, S. Mahima and K. George Thomas, J. Am. Chem. Soc. 125, 7174-7175 (2003).
  5. P. K. Sudeep, S. T. S. Joseph, K. George Thomas, J. Am. Chem. Soc. 127, 6517-6518 (2005).6. B. I. Ipe, K. Yoosaf, K. George Thomas J. Am. Chem. Soc. 128, 1907-1913 (2006).
  6. P. Pramod, S. T. S. Joseph and K. George Thomas J. Am. Chem. Soc. 129, 6712-6513 (2007).
  7. P. V. James, P. K. Sudeep, C. H. Suresh and K. George Thomas, J. Phys. Chem. A. 110, 4329-4337(2006).
  8. S. Zeena and K. George Thomas, J. Am. Chem. Soc., 123, 7859-7865 (2001).
  9. (a) K. George Thomas, V. Biju, D. M. Guldi, P. V. Kamat and M. V. George, J. Phys. Chem. B. 103, 8864-8869 (1999). (b) K. George Thomas, V. Biju, D. M. Guldi, P. V. Kamat and M. V. George, ChemPhysChem, 4,1299-1307 (2003).
  10. K. Yoosaf, P.V. James, A. R. Ramesh, C. H. Suresh and K. George Thomas, J. Phys. Chem. C. 111, 14933-14936 (2007).
  11. Squaraine based dyes and process for preparation thereof, S. Das, K. George Thomas, V. Biju, U. Santhoshand V. Suresh, United States Patent No. 6,417,402 (2002); German Patent DE 10196853 (2005)