Solid State Chemistry Laboratory
Kanishka Biswas Group
Research
Research
Focus-Renewable Energy & Clean Environment
1. Solid State Chemistry of Metal Chalcogenides/Chalcohalides
We are interested in design, exploratory solid state synthesis, detailed characterization and structure-property relationship of various bulk metal chalcogenide and chalcohalides based inorganic materials. We pursue studies on growth kinetics, structural evolution (local/global), phase transitions and local structural disorder in bulk/nano metal chalcogenides by various techniques such as synchrotron X-ray diffraction and pair-distribution function (PDF).
2. Thermoelectric Materials
The ever-rising demand for energy is primarily addressed using earth’s renewable sources, out of which only a handful fraction of it is utilized and a much larger portion (greater than 70%) of it is wasted as form of heat. TE devices thus are centric for global sustainability as it utilizes the waste heat to generate electricity. Given heat’s ubiquitous nature, TE devices provide total-package solution to mitigate environmental crisis and energy needs. To put into perspective, NASA’s deep space probes, or seat climate-control system of certain cars often invariably uses thermoelectric devices to generate power at the expense of radiated heat. The governing parameter for determining its efficiency is the thermoelectric figure of merit, zT which is given by zT = (S2 σ/κ)T, where S is the Seebeck coefficient, σ is the electrical conductivity, and κ is the thermal conductivity.
We actively pursue research in design and development of high performance TE materials based mainly on bulk/nano metal chalcogenides via parallel approaches of enhancing S2σ and suppressing κ. We aim to enhance S2σ by carrier engineering via extrinsic chemical doping, and modification of electronic structure via formation of resonant levels, band convergence etc. On the other hand, κ can be suppressed extrinsically through formation of point defects, endotaxial nanostructures, intergrowth compounds etc.
We also explore materials which, by the virtue of their unique structural topology, exhibit intrinsic glass-like thermal conductivity and crystal like electrical conductivity. We strive to understand unique lattice dynamics and the ensuing ultralow thermal conductivity in systems having rattling sublattices. We also investigate at the bonding environment and atom dynamics within the crystal structure at an atomic level where the presence of ns2 lone pair of electrons causes strong lattice anharmonicity. We aspire to comprehend the underlying chemistry involved in materials with colossal thermopower change, n-p type structural phase transitions and other interesting phenomena.
Our group pursues thermoelectric studies on chalcogenides of lead, bismuth, tin germanium, noble metal-based chalcogenides, pnictides etc.
3. 2D layered materials
Our group is interested in the solution-phase synthesis of new narrow band gap metal chalcogenides in the form of  nanocrystals, nanorods and nanosheets. Extensive research is being carried out on novel heterostructured intergrowth 2D nanosheets and their application in thermoelectrics, field emission and IR detection. We also develop novel layered chalcogenides for ion-exchange and intercalation applications. We are involved in studying the phase-transitions (electronic and structural) in nanocrystalline metal chalcogenides.  We are also interested in synthesis of ultrathin nanocrystalline films of metal chalcogenides at organic-aqueous interfaces.
4. Topological insulators
Topological insulators (TIs) and topological crystalline insulators (TCIs) are new quantum phases with strong spin-orbit coupling leading to topologically protected metallic surface states within the bulk band gap.  Some of the known TIs and TCIs are based on chalcogenides of lead, bismuth and tin. Our group is interested in investigating the chemical aspects and local structure of these metal chalcogenide TIs ad TCIs. We pursue research to modify the electronic structure of TIs and TCIs by chemical doping route and thereby optimize their thermoelectric properties.
Weak topological insulators (WTIs) are new quantum state of matter which is topologically equivalent to a stack of 2D TI layers with even number of Dirac cones on the side surfaces. Hitherto, experimentally verified 3D WTIs are hosted by layered crystal structure with heavy constituent elements which enables WTIs to shine light on minimum lattice thermal conductivity and expected to be important candidates for thermoelectrics. Our group is interested in the investigation and optimization of thermoelectric properties of various weak topological insulators.
5. Halide Based Perovskites
Our group is interested in the fundamental research on halide based perovskites. Mostly, we synthesize these materials via mechanochemistry and simple solution based route. We extensively study the chemical and structural transformations of these perovskites. Along with that we are also interested to explore the photophysical properties of these materials.
6. Water Purification
Water contamination by toxic heavy metals such as Pb2+, Hg2+Â and Cd2+Â and radioactive fission product of nuclear waste is becoming an increasingly important issue in separation science and environmental remediation. Our group designs low cost, wide pH range stable, layered chalcogenides based adsorbents for efficient removal of dissolved contaminants from ppb level with high sorption capacity. We are also interested in designing filtration-unit prototypes for water purification.
1. Solid State Chemistry of Metal Chalcogenides/Chalcohalides We are interested in design, exploratory solid-state synthesis, detailed characterization and structure-property relationship of various bulk metal chalcogenide and chalcohalides based inorganic materials. We pursue studies on growth kinetics, structural evolution (local/global), phase transitions and local structural disorder in bulk/nano metal chalcogenides and chalcohalides by various techniques such as synchrotron X-ray diffraction and pair-distribution function (PDF) analysis.
2. Thermoelectric Materials
The global energy demand increasingly relies on renewable sources, but over 70% is wasted as heat. Thermoelectric (TE) devices help convert this waste heat into electricity. TE efficiency depends on the figure of merit, zT, which involves optimizing the Seebeck coefficient, electrical conductivity, and reducing thermal conductivity. Our research focuses on developing high-performance TE materials, particularly metal chalcogenides, through strategies like chemical doping, electronic structure modification, and thermal conductivity suppression via nanostructuring. We also study materials with unique lattice dynamics, especially those with rattling sublattices, strong lattice anharmonicity and glass-like thermal conductivity.3. 2D Layered Materials
Our group is interested in the solution-phase synthesis of new narrow band gap metal chalcogenides in the form of nanocrystals, nanorods and nanosheets. Extensive research is being carried out on novel heterostructured intergrowth 2D nanosheets and their application in thermoelectrics, field emission and IR detection. We also develop novel layered chalcogenides for ion-exchange and intercalation applications and study the phase-transitions in nanocrystalline metal chalcogenides.4. Topological Insulator
Topological insulators (TIs) and topological crystalline insulators (TCIs) are new quantum phases with strong spin-orbit coupling leading to topologically protected metallic surface states within the bulk band gap. Our group is interested in investigating the chemical aspects and local structure of these metal chalcogenide TIs ad TCIs. We pursue research to modify the electronic structure of TIs and TCIs by chemical doping route and thereby optimize their thermoelectric properties.5. Hybrid and All-Inorganic Halide Perovskites
Our group focuses on fundamental research involving novel hybrid and all-inorganic metal halide perovskite materials. We specialize in both nanoscale and single crystal synthesis using various methods. Additionally, we conduct in-depth studies of their crystal structure and explore their applications in optical and thermal transport properties.
6. Water Purification
Water contamination by toxic heavy metals such as Pb2+, Hg2+ and Cd2+ and radioactive fission product of nuclear waste is becoming an increasingly important issue in separation science and environmental remediation. Our group designs low cost, wide pH range stable, layered chalcogenides-based adsorbents for efficient removal of dissolved contaminants from ppb level with high sorption capacity. We are also interested in designing filtration-unit prototypes for water purification.
