Research

Current research projects @ LSL

Surface enhance Raman studies (SERS) on biomolecules: There is a large interest in knowing the changes in biomolecules in their natural environment, such as, within a cell. Recent advancements have shown that gold and silver nanoparticles can be introduced into the cell without damaging and these attach to various parts of the cell. This enables us to look at the activities of these due to the enhancement in their Raman signals. The group is using SERS for two aspects 1) for diagnostics and 2) for interactions and structural information. We have been looking at protein and small molecular interactions using SERS in collaboration with Prof. Tapas K. Kundu in the field of Cancer Research. In this process we have been interested in producing different nano-structures of gold and silver in pure and core-shell architecture. We have been also interested in studying poly-peptides, nucleotides along with proteins. We have recently used SERS to study recombinant HIV virus RNA in collaboration with Prof. Udaykumar Ranga. We are in the process of developing a diagnostic kit for determining the CD3, CD4 and CD8 in human cells of HIV patients in order to develop an early detection strategy.

High pressure Brillouin scattering studies of Be doped ZnTe epitaxial films: The project is to study the elastic constant measurements of these films as a function of Be concentration and pressure. We are using the Brillouin scattering technique to elucidate the elastic constants on well characterized films, from Oliver Pages (French group).

High pressure studies of n-alkanes: N-heptane is a medium range linear chain alkane. The interest is to understand the high pressure behaviour of these in the solid phase. The recent theoretical studies negate the presence of a solid solid transition expected at around 4 GPa by S. Balasubramanian group (JNCASR). We are using the Raman spectroscopy to study the phase transition at these pressures and also look at high pressures.

Brillouin Scattering studies of nanowires and tubes: There is a long standing interest in the mechanical properties of the nano systems vis-a-vis their bulk materials. Due to their nature it is difficult to determine their elastic properties. We have successfully determined the acoustic velocities in the double walled nanotubes. We have also seen surfaced acoustic waves in double walled nanotubes.

Charge ordering in Manganites: Of late, there is a great interest in manganites due to their interesting magnetic properties. These compounds show a large change in resistivity associated with magnetic field. This phenomenon is also referred as Giant Magnetic Resistance (GMR) or Colossal Magnetic Resistance (CMR). In some of these compounds we also find a Charge ordering transition. Our interest was in finding a clue to this transition. In our Brillouin scattering experiments we found spin waves (magnons) and they mimic the magnetization behavior.

 

Laboratory equipments :

Laboratory has a Brillouin Spectrometer based on 3+3 pass Tandem Fabry Perot Interferometer of JRS Scientific Instruments, Switzerland to carry out Brillouin experiments.

The laboratory has custom built both macro and micro Raman spectrometers. It has been based on a Spex Triax 550 monochromator attached with Spectrum One CCD detector. The macro Raman setup has a home built collection optics using a Keiser’s Super Notch plus filter for the rotuine Raman experiments.

The micro Raman setup uses an epi-fluorescence microscope from Nikkon for collection and an edge filter from Omega optics for Rayleigh light rejection.

A compressed Helium cryostat (Cryodyne, USA) is used for low temperature experiments in the temperature range of 25 to 300 K.

The diamond anvil cell is used for high pressure studies of materials. Currently the laboratory is doing routine experiments up to 30 GPa. The laboratory has micro machining tools necessary to drill < 100 micrometer holes on hardened stainless steel gaskets.

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