jpclcd_v009i004.jpg

Organization of plasmonic nanostructures: KGT group has realized the significance of 

assembling plasmonic nanostructures for the development of various plasmonically- powered systems, which gained international attention. The experimental verification of interplasmon coupling in Au nanorods by adopting electrostatic/supramolecular/covalent approaches was first demonstrated by his group. For e.g., KGT group has effectively utilized this approach for the selective detection of micromolar concentrations of cysteine/glutathione in the presence of various other α-amino acids. His research contributions in the area of gold nanorods have gained international attention among chemists and biologists. Experimental verification of enhanced potential at the edges of anisotropic nanomaterials such as Au nanorods was demonstrated by KGT group. The potential applications of chromophore functionalized metal nanoparticles in the design of sensors for metal cations, light-induced controlled release systems for aminoacids such as DOPA and nanophoshors were also demonstrated. 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 L-DOPA.

 

Significant publications 

01. Surface Plasmon Coupling in End-to-End Linked Gold Nanorod Dimers and Trimers. 

        Kumar, J.; Wei, X.; Barrow, S.; Funston, A. M.; Thomas, K. G.; Mulvaney, P., 

        Phys. Chem. Chem. Phys. 2013, 15, 4258-4264.

02. Plasmon Coupling in Dimers of Au Nanorods. 

       Pramod, P.; Thomas, K. G., 

       Adv. Mater. 2008, 20, 4300-4305.

 03. Preferential End Functionalization of Au Nanorods through Electrostatic Interactions. 

       Pramod, P.; Joseph, S. T. S.; Thomas, K. G., 

       J. Am. Chem. Soc. 2007, 129, 6712-6713.

04. Functionalized Gold Nanoparticles as Phosphorescent Nanomaterials and Sensors. 

      Ipe, B. I.; Yoosaf, K.; Thomas, K. G.; 

      J. Am. Chem. Soc. 2006, 128, 1907-1913.

05. Gold Nanorods to Nanochains:  Mechanistic Investigations on Their Longitudinal 

      Assembly Using α,ω-Alkanedithiols, and Interplasmon

      Coupling. Shibu Joseph, S. T.; Ipe, B. I.; Pramod, P.; Thomas, K. G., 

      J. Phys. Chem. B 2006, 110, 150-157.

06. Selective Detection of Cysteine and Glutathione Using Gold Nanorods. 

      Sudeep, P. K.; Joseph, S. T. S.; Thomas, K. G., 

      J. Am. Chem. Soc. 2005, 127, 6516-6517.

07. Investigations on Nanoparticle−chromophore and Interchromophore Interactions in

      Pyrene-Capped Gold Nanoparticles. 

      Ipe, B. I.; Thomas, K. G.,

      J. Phys. Chem. B 2004, 108, 13265-13272.

08. Uniaxial Plasmon Coupling through Longitudinal Self-assembly of Gold Nanorods. 

      Thomas, K. G.; Barazzouk, S.; Ipe, B. I.; Joseph, S. T. S.; Kamat, P. V.,

      J. Phys. Chem. B 2004, 108, 13066-13068.

09. Light-induced Modulation of Self-assembly on Spiropyran-capped Gold Nanoparticles: 

      A Potential System for the Controlled Release of 

      Amino Acid Derivatives.

      Ipe, B. I.; Mahima, S.; Thomas, K. G., 

      J. Am. Chem. Soc. 2003, 125, 7174-7175.

10. Photoinduced Charge Separation in a Fluorophore-gold Nanoassembly. 

       Ipe, B. I.; Thomas, K. G.; Barazzouk, S.; Hotchandani, S.; Kamat, P. V., 

       J. Phys. Chem. B 2002, 106, 18-21.

11. Surface Binding Properties of Tetraoctylammonium Bromide-capped Gold Nanoparticles.                   

      Thomas, K. G.; Zajicek, J.; Kamat, P. V., 

      Langmuir 2002, 18, 3722-3727.

12. Fullerene-functionalized Gold Nanoparticles. A Self-assembled Photoactive

      Antenna-metal Nanocore Assembly. 

      Sudeep, P. K.; Ipe, B. I.; Thomas, K. G.; George, M. V.; Barazzouk, S.; Hotchandani, S.; Kamat, P. V.,       

      Nano Lett. 2002, 2, 29-35.

 

13. Making Gold Nanoparticles Glow:  Enhanced Emission from a Surface-bound Fluoroprobe.             

       Thomas, K. G.; Kamat, P. V., 

       J. Am. Chem. Soc. 2000, 122, 2655-2656.

Reviews and books

14. Surface Plasmon Resonance in Nanostructured Materials 

        Thomas, K. G.

        Chapter in Nanomaterials Chemistry, Eds. C.N.R. Rao, A. Muller, A. K. Cheetham 2007; pp. 185-216,              Wiley-VCH.

 

15. Interfacial Properties of Hybrid Nanomaterials. 

        Ipe, B. I.; Yoosaf, K.; Thomas, K. G., 

        Pramana 2005, 65, 909-915.

16. Chromophore Functionalized Gold Nanoparticles. 

        Thomas, K. G.; Kamat, P. V., 

        Acc. Chem. Res. 2003, 36, 888-898.

 

17. Photochemistry of Chromophore-functionalized Gold Nanoparticles. 

       Thomas, K. G.; Ipe Binil, I.; Sudeep, P. K., 

       Pure Appl. Chem., 2002, 74, 1731-1738.

Plasmonically-active assemblies for SERS:  Following the assembling strategy, KGT group has developed methodologies for enhancing the intensity of electric field (hot spots) at the junctions of plasmonically-active assemblies by varying the distance between the plasmonic nanoparticles. KGT group has developed SERS substrates (i) by coating Ag@SiO2 nanoparticles on the inner walls of the glass capillaries resulting in very high enhancement factor and (ii) for sieving and sensing applications. The fundamental knowledge acquired on plasmon hybridization and hot-spot generation was further translated to a real device by undertaking a project on the “Design of a Surface-Enhanced Spectroscopy based Device for the Rapid Detection of Organophosphate Pesticides and Pyrethroid Insecticides in Fruits and Vegetables,” addressing a severe problem faced by many developing and underdeveloped countries. Jointly with experts from other branches of science, a customized tabletop Raman spectroscopic device was built, which is interfaced with a plasmonic platform and data processing software for the rapid detection of pesticide/insecticide residues from vegetable/fruit extracts. The device is now identified by the funding agency as one of the 14 top-performing products having translational potential (https://youtu.be/vl7xySLKOnQ).

Significant publications 

  1. Mesoporous Silica Capped Silver Nanoparticles for Sieving and SERS Sensing. 

       Fathima, H.; Paul, L.; Thirunavukkuarasu, S.; Thomas, K. G., 

       ACS Applied Nano Materials, 2020, 3, 6376–6384.

 

  1. Cost-effective Plasmonic Platforms: Glass Capillaries Decorated with Ag@SiO2 Nanoparticles on Inner Walls as SERS Substrates.

       Shanthil, M.; Fathima, H.; Thomas, K. G., 

       ACS Appl. Mater. Interfaces 2017, 9, 19470-19477.

 

  1. Au Nanorod Quartets and Raman Signal Enhancement: Towards the Design of Plasmonic Platforms. 

       Kumar, J.; Thomas, R.; Swathi, R.; Thomas, K. G., 

       Nanoscale 2014, 6, 10454-10459.

 

  1. Ag@SiO2 Core–shell Nanostructures: Distance-dependent Plasmon Coupling and SERS Investigation. 

       Shanthil, M.; Thomas, R.; Swathi, R. S.; Thomas, K. G., 

       J. Phys. Chem. Lett. 2012, 3, 1459-1464.

 

  1. Surface-Enhanced Raman Spectroscopy: Investigations at the Nanorod Edges and Dimer Junctions. 

       Kumar, J.; Thomas, K. G., 

       J. Phys. Chem. Lett.  2011, 2, 610-615.

 

Perspective

 

Present and Future of Surface Enhanced Raman Scattering. 

Langer, J.; Jimenez de Aberasturi, D.; Aizpurua, J.; Alvarez-Puebla, R. A.; Auguié, B.; Baumberg, J. J.; Bazan, G. C.; Bell, S. E. J.; Boisen, A.; Brolo, A. G.; Choo, J.; Cialla-May, D.; Deckert, V.; Fabris, L.; Faulds, K.; García de Abajo, F. J.; Goodacre, R.; Graham, D.; Haes, A. J.; Haynes, C. L.; Huck, C.; Itoh, T.; Käll, M.; Kneipp, J.; Kotov, N. A.; Kuang, H.; Le Ru, E. C.; Lee, H. K.; Li, J.-F.; Ling, X. Y.; Maier, S. A.; Mayerhöfer, T.; Moskovits, M.; Murakoshi, K.; Nam, J.-M.; Nie, S.; Ozaki, Y.; Pastoriza-Santos, I.; Perez-Juste, J.; Popp, J.; Pucci, A.; Reich, S.; Ren, B.; Schatz, G. C.; Shegai, T.; Schlücker, S.; Tay, L.-L.; Thomas, K. G.; Tian, Z.-Q.; Van Duyne, R. P.; Vo-Dinh, T.; Wang, Y.; Willets, K. A.; Xu, C.; Xu, H.; Xu, Y.; Yamamoto, Y. S.; Zhao, B.; Liz-Marzán, L. M. 

ACS Nano 2020, 14, 28-117.

toc.png

Plasmon-exciton coupling: Herein, we investigate the interactions between plasmons on metal particles/nanorods and excitons on dyes or their assemblies as ensemble and in single particle level by combining dark-field microscopy and high resolution scanning electron microscopy. The role of various optical parameters dictating the plasmon-exciton interactions and formation of hybrid states were investigated in collaboration with theoretical groups and established guidelines for the design of plexcitonic systems, by choosing plasmonic and excitonic systems with high oscillator strength and narrow spectral width.