Key Research Results

Salient Research Achievements

Dr. Ogale and coworkers have developed Fe-MOF based Li ion battery anode with excellent reversible capacity of 800 mAh g−1 at 250 mA g−1 and equally impressive rate performance (specific capacity of 500 mAh g−1 at a high rate of 3 A g−1). The LCO//Fe-MOF anode full cell exhibited a fast charge and discharge, affording a specific capacity of 38 mAh g−1 in 2 min of charging time and a very good rate performance (40 mAh g−1 at 7 A g−1), with a robust stability upto 1000 cycles. A flexible device was fabricated using a free-standing LCO cathode and a Fe-MOF anode MWCNT composite and employed as a heat generating skin patchable complement for the transdermal drug delivery application (ACS Appl. Energy Mater. 2019, 2, 6, 4450-4457).

Dr. Nag and co-workers have been exploring metal halide perovskite nanocrystals for optoelectronic applications like solar cell, light emitting diodes, and photodetectors. In this work, they design novel materials, study their photophysical properties, then if the desired properties are achieved, then look for preliminary device applications (Angew.Chem. Int. Ed. 2017, 56,14187–14191, J. Phys. Chem. Lett., 2017, 8, 4988–4994, Chem. Sci. 2017, 8, 4602, and ACS Energy Lett., 2017, 2, 2251).

Three major research directions are: (i) understanding and optimizing the surface of cesium lead halide perovskite nanocrystals for achieving efficient optolectronic process, (ii) developing novel Pb-free perovskite materials with suitable optolectronic properties, and (iii) lattice doping of metal halide nanocrystals, to tailor optical and electronic properties.

In another project, the Nag group is trying to develop composite non-noble metal earth abundant nanocrystals with 2-D conducting mat-like graphene for photocatalytic and electrocatalytic applications including counter electrodes in solar cell and H2 evolution.

Dr. Pillai and co-workers have introduced InP QDs to the family of cationic nanoparticles as a practical alternative to toxic metal ion based QDs for future light harvesting applications. An efficient electrostatically driven resonance energy transfer (E ~ 60%) was successfully demonstrated, under physiological conditions, between the cationic InP QD donor and anionic dye acceptor (Chem. Sci. 2017, 8, 3879-3884).

Dr. Musthafa and co-workers addressed the root of the parasitic chemistry encountered at the cathodic half-cell of state of the art direct alcohol fuel cells. Using an outer sphere electron acceptor that does not form a bond with the cathode during redox energy transformation, interfacial chemistry is effectively decoupled from parasitic chemistry, leading to an alcohol fuel cell driven by inexpensive carbon nanoparticles, with performance metrics ∼8 times higher than Pt-based DAFC-O2 fuel cells (J. Phys. Chem. Lett., 2017, 8, 3523–3529).

Dr. Vaidhyanathan, Dr.Ogale and co-workers have synthetically designed self-exfoliated triazole-triformyl phloroglucinol-based covalent organic nanosheets (IISERP-CON1) and them used as an anode material for Li ion battery. A very high initial discharge capacity of 2070 mAh/g followed by a stable reversible capacity of 720 mAh/g (after 100 charge discharge cycle) along with excellent rate capability at different current densities was realized establishing the promise of this new material for practical Li ion battery application (Adv. Energy Mater. 2017, 8,1702170).

Dr. Ogale group in collaboration with Kabir and coworkers have recently synthesized and studied F-Doped carbon nano-onion films as scaffold for highly efficient and stable Li metal anodes. The synthesis involved a novel laser direct-write process. A thin layer of carbon nano-onions could be directly laser written on a copper substrate to stabilize the Li metal anode and prevent the dendrite growth. The F-doped carbon nano-onion film (F-CNOF) scaffold enabled reversible electroplating for over 1500 hours (300 cycles) with a coulombic efficiency of ∼100% (Nanoscale 2018,10, 7630-7638).

Dr. Boomishankar and co-workers have demonstrated a simple self-assembly protocol to generate electro- and photocatalysts for H2 evolution reaction in the form of an [CoII6L18Cl6(H2O)6]Cl6 cage. This cage exhibits the pH dependence of potential as well as catalytic current indicating the possible involvement of proton-coupled electron transfer in the H2 evolution which has a turnover frequency of 16 h-1. Also, it acts as a photocatalyst for the evolution of H2 from water in the presence of Ru(bpy)32+ as a photosensitizer and ascorbic acid as a sacrificial electron donor. The rate of this reaction is found to be pseudo-first order with a turnover frequency of 20.50 h-1 (Inorg. Chem. 2017, 56, 13286-13292).

Dr. Ogale and co-workers have synthesized and examined the g-C3N4/ NiAl-LDH 2D/2D Hybrid Heterojunction for High-Performance Photocatalytic Reduction of CO2 into Renewable Fuels. The optimum g-C3N4/NiAl-LDH heterojunctions showed the highest CO production rate of 8.2 μmol h‒1g‒1, which is 5 times higher than that of pure g-C3N4 and 9 times higher than that for pure NiAl-LDH (ACS Applied Materials and Interfaces, 2018, 10, 3, 2667–2678).

Dr. Hazra and co-workers have investigated a structure-property relationship to design mechanochromic materials based on the precise tuning of solid-state packing by modulating donor substitution in isoindolinone based newly developed charge transfer (CT) luminogens. They showed that slight tuning of donor substitution in CT luminogens can effectively control the metastable states under mechanical grinding. Notably, all the designed luminogens exhibited gigantic emission shifts of ~ 100 -125 nm, along with the fluorescence switching ability over wide range of temperature. Such molecules find potential applications in rewritable devices, temperature sensors and in lighting up cells (Chemical Science, 2018, 9, 3592-3606).

Dr. Ballav and co-workers have developed a simple one-step, cost-effective, scalable, wet-chemical reduction of Graphene Oxide (GO) to rGO in aqueous medium for achieving self-assembled rGO having an optimum balance of physicochemical properties, required for improved performance in solid-state supercapacitor applications. Specifically, the researchers report the use of transition metal slats as reducing agents in producing high-quality rGO (Chem, 3, 846, 2017).

Dr. Prasenjit and co-workers have studied porous covalent framework based proton conducting material. In this work, they have shown ~ 130 fold enhancement in the proton conductivity after post-synthetic covalent modification of a chemically stable porous covalent framework (PCF-1). Owing to the high chemical stability of PCF-1, -SO3H groups (Brønsted acidic group) has been incorporated in the porous network which resulted into the high conductivity (in the order of 10-2 Scm-1). This proton conductivity value is one of the highest values in the domain porous organic materials after post-synthetic covalent modification (J. Mater. Chem. A 5, 13659-1366, 2017).

Dr. Surjeet and co-workers have developed new potential thermoelectric (TE) materials such as Ag2X (X = S, Se and Te); which exhibit enhanced thermoelectric performance when heated 100 oC above room-temperature. The researchers have used a simple mechanical milling method to obtain Ag2X nanoparticles in a phase pure form, which were further pelletized and sintered to study their thermoelectric properties. The measurements were performed using LSR and LFA instruments purchased under this proposal. Other class of TE materials synthesized under this proposal are the Half-Heuslers alloys of 111 stoichiometry, that include ZrNiSi, HfNiSi, ZrNi,Sb, ZrFeSi and Zr(Ni, Fe)Si. It was observed that doping merely 5% of Sn at the Si site in ZrNiSi resulted in marked improvement in the TE properties.

Dr. Shouvik and co-workers were able to probe and control various excitonic quasi-particles in quantum confined light emitting devices including the identification of different charged states of Trions, Bi-Excitons at low temperatures using simple Electro-optical technique like photocapacitance (J. Appl. Phys., 2018, 123, 044305).

Dr. Shouvik and co-workers also work in the field of energy storage devices. They have reported a single step hydrothermal synthesis of carbon nanodot decorated V2O5 nanobelts as hybrid conducting material for supercapacitor application (J. Solid State Chem. 2017, 253, 103-112). The hybrid material delivered an energy density of 60 W h kg−1 and a reasonably high power density of 4.1 kW kg−1 at 5 A g−1. A good cycling stability and capacitance retention of about 87% was observed even after 5000 cycles. They have also shown complimentary effects of annealing temperature on optimal tuning of functionalized carbon-V2O5 hybrid nanobelts for targeted dual applications in electrochromic and supercapacitor devices (RSC Adv., 2018, 8, 8596-8606).

Dr. Rapol and co-workers report the design, fabrication and characterization of a nano-scale array of plasmonic nanostructures, which would be helpful in fabricating near-ﬁeld optical traps for neutral atoms. The building block of the array is a silver nano-disk fabricated on the surface of a glass substrate. The researchers have calculated the electromagnetic ﬁeld-distribution using ﬁnite diﬀerence time domain (FDTD) methods above the nanodisk, and calculate the intensity, optical potential and the dipole force for 87Rb atoms. This work is aimed at the development of energy harvesting nanostructures. Optical ﬁeld near a nanodisk Simulated optical ﬁeld near a single silver nanodisk of diameter 150 nm and 35 nm height.

Dr. Nair and co-workers have synthesized two series of oxides – (i) delafossites and (ii) layered Ruddelson-Popper compounds, to investigate their structural, microstructural and high temperature thermoelectric properties. High Seebeck coefficient values (>400 μV/K) are obtained for the compounds (undoped CuAlO2 and CuAl0.98M0.02O2 (where M=Fe, Co, Ni, Pb, Ge)), throughout the measurement range which did not vary much beyond ~600 K. However, κ decreased on doping due to increased mass fluctuation scattering. Highest zT=0.008 at 926 K was reported for the parent CuAlO2. Layered Ruddelson-Popper compounds (Lan+2Nin+1O3n+1, n=0 and 1) were also synthesized and studied for high temperature thermoelectric properties for the first time. At 1073 K, a zT of 0.01 was obtained for La2NiO4. For other compounds, the values were ~0.002.

Dr. Musthafa, Dr. Ogale and co-workers have synthesized a pure phase Cu-rich ternary metal sulfide Cu3SnS4 (CTS) synthesized by a single step solution process, was reported as a Li-ion battery anode without the need of any composite forming material such as rGO or CNTs . The high Cu: Sn ratio provide excess Cu atoms as the buffer matrix for volume expansion of Sn, leading to high specific capacities of 1082 mAhg-1 at 0.2 Ag-1 and 440 mAhg-1 at 3 Ag-1 with superior stability upto 950 cycles. The full cell device of CTS NPs with LCO cathode delivered a high energy density (405 Wh/kg when charged at low current density of 0.1 mAg-1 and 285 Wh/Kg at 0.5 Ag-1) with long term stability of 500 cycles at a high current density proving the suitability of CTS NPs anode for commercial applications (ChemElectroChem, 2019, 6, 1371-1375).

Dr. Ogale and co-workers have reported a series of nature-inspired Z-scheme g-C3N4/FeWO4 composites for higher performance and selective CO2 reduction to CO as solar fuel under solar light. The novel direct Z-scheme coupling of the visible light-active FeWO4 nanoparticles with C3N4 nanosheets exhibited excellent performance for CO production with a rate of 6 μmol/g/h at an ambient temperature, almost 6 times higher compared to pristine C3N4 and 15 times higher than pristine FeWO4. The results clearly demonstrate that the staggered band structure between FeWO4 and C3N4 reflecting the nature-inspired Z-scheme system not only favor superior spatial separation of the electron-hole pair in g-C3N4/FeWO4, but also shows good reusability (ACS Appl. Mater. Interfaces, 2019, 11, 6174-6183).

Dr. Ogale and co-workers have demonstrated a simple physical mixture of silicon nanoparticles (SiNPs) and chemically exfoliated few layer black phosphorus (FLBP) as a Li-ion battery anode with very high capacity values of 3386 mA h g−1 and 2331 mA h g−1 at current densities of 0.1 A g−1 and 0.5 A g−1, respectively, with an impressive stability measured up to 250 cycles. This approach harnesses the uniquely flexible lithiation/delithiation stress absorbing character of FLBP that is far superior to different forms of functional carbons as additives or partner materials in Si–C composites (Sustainable Energy Fuels, 2019,3, 245-250).

Dr. Ogale and co-workers have also synthesized a new family of carbonyl functional group based iodoantimonate organic–inorganic hybrid structures via in situ formed cationic (oxonium) precursors. These solids exhibit interesting structural diversity driven by the change of the substituent on hydrogen-bonded oxonium salts of DMF, 2-pyrr., NMP, and DMA leading to different face/edge sharing configurations of SbI6 octahedra. Moreover, these hybrid solids exhibited a band gap of ∼2.2 eV falling in the visible domain of interest to optoelectronics. The electronic states spectra and work functions evaluated by DFT calculations revealed that the behaviour of photo-excited charges in the heterostructures could attract potential application interest (Chem. Commun., 2019,55, 7562-7565).

Dr. Boomishankar and co-workers have also developed small molecule based ferroelectric materials and studied their utility in mechanical energy harvesting applications. A new phosphonium salt of formula [Ph2P(NHiPr)2]PF6 were synthesized by their group which shows a ferroelectric remnant polarization of ~6 μC/cm2. Polymer composite of this compound with polydimethyl siloxane (PDMS) was prepared for various (5,10,15 and 20) weight percentage compositions and studied for mechanical energy harvesting applications. A highest open circuit voltage of ~8.5 V was obtained for the 10 weight percentage composite which is first of its kind for the utility of organic salts of polymer composites for mechanical generator activity (Angew. Chem. Int. Ed., 2018, 57, 9054-9058).

Dr. Boomishankar, Dr. Ogale and co-workers have developed new examples of organic-inorganic hybrid ferroelectric materials and utilized them for obtaining efficient mechanical energy harvesters. They have prepared two new discrete A2MX4 type halogenometallates of formula [BnNMe2R]CdBr4 (Bn = benzyl; 1: R = Me; 2: R = n-Pr) and found them to exhibit high ferroelectric polarization with the remnant polarization (Pr) values of 18.59 and 14.24 μCcm‒2, respectively. Flexible composite thin-films of these salts with polydimethylsiloxane (PDMS) were prepared and employed as mechanical energy harvesting devices at a frequency of 25 Hz and an applied force of 40 N. The maximum output voltages of 52.9 V and 63.8 V have been recorded for the PDMS-fabricated devices of 5 wt.% of 1 and 10 wt.% of 2, respectively. Also, the obtained power densities of 13.8 and 37.1 µWcm ̶ 2 for the respective 5 wt.% 1-PDMS and 10 wt.% 2-PDMS devices are much higher than all known devices made up of organic-inorganic hybrid materials embedded in PDMS. The energy harvested from these devices was further utilized to charge a capacitor through a full wave bridge rectifier (Chem. Mater., 2019, 31, 4545-4552).

Dr. Pillai and co-workers were successful in introducing InP QDs to the family of cationic nanoparticles as a practical alternative to toxic metal ion based QDs for future light harvesting applications. An efficient electrostatically driven Föster Resonance Energy Transfer (FRET) was successfully demonstrated, under physiological conditions (E ~ 60%), between the cationic InP QD donor and anionic dye acceptor. In a recent report, multicolor reusable photopatterns were created from a single QD-nanohybrid system as opposed to the common practice of using different colored QDs. FRET process in InP QD-dye film was regulated through the selective and controlled photodegradation of organic dye molecules. Consequently the FRET efficiency was regulated between completely ON and OFF states, through a moderately efficient state to generate three distinctly different colors . Similarly, the group have shown the decisive role of electrostatics, arising from ligands, in achieving an efficient light induced electron transfer in environmentally friendly Copper Indium Sulfide/Zinc Sulfide Quantum Dots (CIS/ZnS QDs) in water (Chem. Sci. 2017, 8, 3879-3884), (ACS Energy Lett. 2019, 4, 7, 1710–1716), and (J. Mater. Chem. A. 2018, 6, 22248 – 22255).

Dr. Pillai and co-workers have successfully demonstrated ligand directed catalysis and light harvesting using metal and semiconductor nanoparticles. In one example, they have shown the potency of Indium Phosphide/Zinc Sulfide Quantum Dots (InP/ZnS QDs) to photocatalyze two distinctly different reactions: metal-centered redox and carbon-carbon (C-C) coupling reactions (Chem. Mater. 2019, 31, 2258 - 2262). A good overlap of the action spectra with the ground state absorption of InP/ZnS QD confirmed the active participation of QDs in the photocatalyzed metal-center redox and C-C bond forming reactions. Similarly, the bad reputation of ligands in nanoparticle based visible-light photocatalysis was salvaged in a recent effort. The introduction of favorable interaction improved the NP accessibility to the reactants and the probability of hot electron transfer, thereby suppressing the ‘poisoning’ effect of the ‘insulating’ organic ligands (Chem. Mater. 2018, 30, 8415 - 8419).

Dr. Prasenjit and co-workers are working on (a) thermoelectric properties of layered materials and (b) CO2 reduction to methanol using first principles density functional theory based methods. In the area of thermoelectrics, they have studied electronic transport properties of PbI2 and found that the Seebeck coefficient is high i.e. 2.83 mVK-1 and 2.92 mVK-1 for bulk and monolayer of PbI2, respectively at room temperature. For bulk the highest ZT obtained is 0.33 at 600 K and 6.07 × 1020 cm-3 hole doping while for monolayer the highest ZT obtained is 0.17 at 600 K and 5.30 × 1013 cm-2 hole doping.

Dr. Praenjit and co-workers, with the help of density functional theory based calculations, have also studied the reaction mechanism for the electrocatalytic reduction of CO2 using polyaniline (PANI) and its composite with a single palladium atom (Pd/PANI) as a catalyst. Their results show that synergistic effects between PANI and Pd-atom makes the Pd/PANI composite a more efficient catalyst for capture and activation of CO2 than those of the individual systems (PANI and Pd atom). Moreover, it is found that both PANI and Pd/PANI show high selectivity for the formation of formic acid (HCOOH) over the methanol (CH3OH) production. The electroreduction of CO2 towards formic acid (HCOOH) follows two different pathways, depending on the catalyst: on PANI the formation of HCOOH occurs through the *COOH intermediate, whereas for the case of Pd/PANI, the same reaction proceeds through the formation of formate (*OCHO). While the formation of CH3OH from CO2 on PANI is not feasible, electroreduction of CO2 towards CH3OH on Pd/PANI occurs through the formation of CO (J. Mol. Modeling, 2018, 24, 248).