Prof. Chandrabhas Narayana is a highly accomplished Raman and Brillouin Spectroscopist with expertise in x-ray diffraction using synchrotron radiation and high-pressure research. His work with Raman spectroscopy work is truly inter-disciplinary, spanning Physics, Chemistry, and Biology, and he is a leader who has taken Raman spectroscopy to a wide variety of applications ranging from basic sciences, inter-disciplinary research to translational work and is very well recognized by the peers.

Prof. Chandrabhas Narayana has significantly contributed in the area of Condensed Matter Physics using Raman spectroscopy.  One of his latest exploits has been in the area of Topological Insulators (TI).  There has been a growing interest in TI. Prof. Chandrabhas Narayana’s group has used Raman spectroscopy to elucidate new materials which are TI at relatively low strains (pressures).  They have discovered several candidates for TI that show normal Insulator to Topological Insulator behaviour with a little amount of strain.  The significance of this contribution is that many techniques used for detecting TI fail when the samples are under high pressures inside a diamond anvil cell, but his group has demonstrated that Raman spectroscopic technique can be used to discover new Topological Insulators by introducing strain in otherwise insulating samples.  Recently, IOP publishers gave one of his early papers in this field the “Best Cited Author Award” during the year 2016-2018.

In Chemistry his group has been contributing significantly to the synthesis of gold and silver nanomaterials. Tailoring the surface plasmon resonance (SPR) property of silver and gold nanoparticles for applications in the area of the Surface-Enhanced Raman Spectroscopy (SERS) is a highly researched topic. His group was the first to come up with the idea of creating a gold/silver junction in nanoparticles to produce a universal substrate for the detection of trace amounts of analytes. This work is highly cited and has led to many gold-silver sandwich structures by several groups. As a follow up of this, the group has also produced a new sandwich structured nanoparticle with silver core, dielectric (SiO₂) layer on top decorated with gold nanoparticles on top, which gave another dimension to the research in this area.  This was the first demonstration of SERS from gold nanoparticles equalling that of silver nanoparticles. His group is now well-known in the world for their work on SERS.

Metal-Organic Frameworks (MOFs) have been highly researched materials due to their properties analogous to zeolites with the added advantage of tunability of pores as well as catalytical activity. His group has been synthesizing the MOFs and finding microscopic origins of the observed properties using Raman spectroscopy, which has led to a better understanding of the MOFs and their synthesis. His group’s work has guided many of the material chemists to take this route to understand the various exotic properties. Currently, Raman spectroscopy has become an important tool in any research in MOFs. Their structural predictions made with Raman spectroscopy and molecular dynamic simulations were verified crystallographically and have been acknowledged in the literature. Recently, his work carried out in collaboration with a German group lead by Dr K. Jayaram (currently a faculty at IIT Jammu) demonstrated the Graphene MOF composite as an exceptional Li-ion battery electrode applications (in Advanced Functional Materials 2019) where Raman spectroscopy has uncovered a deep understanding of the property. This work attracted the attention of peers and is recognized as the most downloaded paper by publishers.

Besides, Prof. Chandrabhas Narayana has been using Raman spectroscopy and SERS to problems in the area of Biology. There are three salient features of his work in this area. The first one is that his group along with colleagues in Biology have found Raman spectroscopy as an alternative technique to x-ray crystallography along with MD simulations to probe the structure/function properties of proteins, especially in the understanding of the drug-protein interactions leading to drug design and development. This was widely appreciated and covered on the phys.org website in 2014. The second innovation has been to use SERS for non-PCR based detection of pathogen nucleotides (it was demonstrated for the detection of RNA virus namely, HIV) and he has a patent for this in the US, Europe, and South Africa. This is a very important discovery and it is very useful for any DNA or RNA detection without PCR amplification, hence eliminating the cost and the errors in the detection. As a third dimension to the applications in biology, his recent work on using Raman spectroscopy for understanding the strength and elasticity of the lens capsule upon the addition of trypan blue during cataract surgery has been appreciated by cataract surgeons and eye doctors. The doctor involved in this work has received many awards for the understanding to avoid failures in cataract surgery.

Development of Techniques

During his independent career at JNCASR, he made his own Raman Spectrometer, having specifications comparable to the best one available commercially costing only 1/4^th and all of his papers were published using this custom-built Raman spectrometer. He holds US and Indian Patents for this. He developed a remote Raman spectrometer for Laboratory for Electro-optics Systems (LEOS), ISRO for finding defects in huge SiC mirrors (2 to 3 m diameters) for telescopes in the sky and this learning could help in possible Mars Mission in the future.  Recently, he miniaturized the Raman spectrometer, and jointly with the Indian Institute of Science Education and Research (IISER), Thiruvananthapuram in an IMPRINT project developed a pesticide detection tool using this spectrometer, which was selected as the top 4 IMPRINT projects by the ministry of human resource and development (MHRD).

He is a specialist in the multi megabar (Mbar) high-pressure physics and has achieved static pressures in the excess of 3.5 Mbars (3.5 million atmospheres), achieved so far by only around 10 research groups. To achieve such pressures routinely, he developed the techniques like focused ion beam drilling for 10 to 15 ?m holes in super hard materials like rhenium and loading samples in these tiny holes under scanning electron microscopy for diamond anvil cells. These pressures are generally required to study planetary materials or elemental systems. He has worked on the "metallization of hydrogen", a holy grail in the area of high-pressure physics showing that hydrogen remains a molecular solid even up to pressures of 3.42 Mbars well above the pressures of metallization predicted by theory. This was the first experiments on hydrogen above 3 Mbars in the world. Recent work by the geophysical laboratory of the Carnegie Institute of Washington confirmed this result and extended this limit to 3.6 Mbars. These results prompted experimental and theoretical groups to look at elemental metals like Na, Al, along with hydrogen to understand the theory of dense matter.  Recently, along with IMPMC (CNRS geophysics laboratory), Paris he showed FCC to HCP to BCC phase transitions in Aluminium at pressures over 3.8 Mbars gaining significant insight into the dense matter physics. 

His group is the only group in India actively pursuing Brillouin spectroscopy. Though Brillouin spectroscopy is used to study the acoustic properties of solids, his group used it creatively to elucidate various novel properties of solids, for example of manganites, known for colossal magnetoresistance (CMR). His group was the first to show ferromagnetic magnons present in the anti-ferromagnetic Nd_0.5Ca_0.5MnO₃ and suggesting the presence of droplets of ferromagnetic islands in the sea of anti-ferromagnetic environment. This was the first experimental evidence for the electronic phase segregation, which is fundamental to the CMR property and the origin of various exotic properties. It was a demonstration of Brillouin spectroscopy to be an excellent complementary tool for Neutron diffraction studies, with the advantage of working with tiny amounts of sample.   Recently, he has demonstrated the presence of the second sound in Double-Walled Carbon Nanotubes starting from room temperature. A quest for second sound in materials has recently led to the demonstration of  Graphite showing second sound much below room temperatures.