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Excitons and plasmons: A tale of two elementary excitations and their interaction


Title : Excitons and plasmons: A tale of two elementary excitations and their interaction.
Speaker : Prof. K George Thomas, IISER Trivandrum
Date : 05/02/2020, 5:30 PM , C.V Raman Hall, Second Floor.


Recent developments in various light mediated processes in molecules and materials have led to several technological breakthroughs. The first part of the talk will focus on various light mediated processes, with a brief introduction to the principles of photochemistry and photophysics. Followed by this, I shall discuss the parallels between the elementary electronic excitations in organic chromophores, referred to as the excitons and elementary collective electronic excitations in metal nanostructures, referred to as the plasmons.1,2 Though emerging from different schools of research, the parallels they possess, both in their isolated and assembled forms, are indeed interesting. By employing the larger framework of the dipolar coupling model, a generalized picture on the excitonic/plasmonic coupling and the emergence of novel optical properties will be discussed.1-5 Our recent efforts in the design of plexcitonic systems, resulting from the strong coupling interactions between plasmons and excitons, will also be presented.6 Plasmonic excitation in metal nanoparticles generates an enhanced electric field on its surface which has resulted in the development of numerous spectroscopic techniques; for example, surface-enhanced Raman scattering (SERS).  We have investigated the effect of the electric field on SERS at the vicinity of plasmonic nanoparticles and at the hot spots.7-10 In addition, we have translated these concepts for the design of plasmonic platforms, which can identify molecules of importance in health, environment and safety.10 Taking these ideas further forward, we have developed a customized Raman spectroscopy device, interfaced with an in-house developed plasmonic platform based on various core-shell plasmonic nanostructures and data processing software for rapid detection of pesticide/insecticide residues from vegetables and fruits.11,12 These aspects will also be presented.

  1. R. Thomas, J. Kumar, J. George, M. Shanthil, G. N. Naidu, R. S. Swathi, K. George Thomas, J. Phys. Chem. Lett., 2018, 9, 919.
  2. https://www.youtube.com/watch?v=DGJDsXKZUaw&t=6s
  3. S. Kar, K. Swathi, C. Sissa, A. Painelli, K. George Thomas, J. Phys. Chem. Lett., 2018, 9, 4584.
  4. J. George and K. George Thomas, J. Am. Chem. Soc., 2010, 132, 2502.
  5. J. George, S. Kar, E. S. Anupriya, A. D. Das, C. Sissa, A. Painelli and K. George Thomas ACS Nano, 2019, 13, 4392.
  6. R. Thomas, A. Thomas, S. Pullanchery, L. Joseph, S. M. Somasundaran, R. S. Swathi, S. K. Gray, K George Thomas, ACS Nano, 2018, 12, 402.
  7. J. Kumar, K. George Thomas, J. Phys. Chem. Lett., 2011, 2, 610.
  8. M. Shanthil, R. Thomas, R. S. Swathi, K. George Thomas, J. Phys. Chem. Lett., 2012, 3, 1459.
  9. J. Kumar, R. Thomas, R. S. Swathi and K. George Thomas, Nanoscale, 2014, 9, 10454.
  10. M. Shanthil, H. Fathima and K. George Thomas, ACS Appl. Mater. Interfaces, 2017, 9, 19470.
  11. J. Langer et al. ACS Nano 2020, DOI: 10.1021/acsnano.9b04224 (an extensive review on “Present and Future of Surface-Enhanced Raman Scattering” (co-authored by KGT along with 57 senior researchers).
  12. https://www.youtube.com/watch?v=vl7xySLKOnQ&feature=youtu.be


About the speaker:

Prof. George Thomas has made significant contributions in several areas of photosciences and nanomaterials and his group is currently focusing on the studies related to light-matter interaction at the nanoscale. He received his PhD degree in Chemistry from the University of Kerala and afterwards worked as senior scientist in the Photosciences & Photonics Section of the CSIR-National Institute for Interdisciplinary Science & Technology from July 1994 to April 2010. In May 2010, he accepted an invitation from the newly established Indian Institute of Science Education and Research Thiruvananthapuram (IISER TVM) and joined as a Professor. He served as the founding Dean of IISER TVM during 2010-2015.


George Thomas is a recipient of several awards and distinctions: the Shanti Swarup Bhatnagar Prize in Chemical Sciences in 2006 and the J C Bose National Fellowship (2014-2024). More Recently he was awarded the MRSI-ICSC Superconductivity & Materials Science Annual Prize (2015) and C. N. R. Rao Prize Lecture in Advanced Materials (2020) by Material Research Society of India. He is an elected fellow of the Indian National Science Academy, New Delhi and Indian Academy of Sciences, Bangalore and serving as Honorary Professor of the Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore. He has published around 120 research articles, in journals of international repute, with an average citation of ~70. Working in his group, twenty students received doctoral degree; many of them are faculty members in major academic and scientific institutes, both in India and abroad. Professor George Thomas is currently serving as the president (2019-2020) of the Asian and Oceanian Photochemistry Association.

For more details on his publications, visit: