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Showing papers by "Indian Association for the Cultivation of Science published in 2018"


Journal ArticleDOI
TL;DR: Bringing stability by proper surface functionalization without use of secondary additives would indeed help in wide spreading of their applications as CsPbI3 is one of the most demanding optical materials.
Abstract: High temperature colloidal synthesis for obtaining thermal, colloidal and phase-stable CsPbI3 nanocrystals with near-unity quantum yield is reported. While standard perovskite synthesis reactions were carried out at 160 °C (below 200 °C), increase of another ≈100 °C enabled the alkylammonium ions to passivate the surface firmly and prevented the nanocrystals from phase transformation. This did not require any inert atmosphere storage, use of heteroatoms, specially designed ligands, or the ice cooling protocol. Either at high temperature in reaction flask or in the crude mixture or purified dispersed solution; these nanocrystals were observed stable and retained the original emission. Different spectroscopic analyses were carried out and details of the surface binding of alkyl ammonium ligands in place of surface Cs in the crystal lattice were investigated. As CsPbI3 is one of the most demanding optical materials, bringing stability by proper surface functionalization without use of secondary additives would indeed help in wide spreading of their applications.

141 citations


Journal ArticleDOI
TL;DR: In this article, a wide window size tunable CsPbBr3 nanocrystals were reported without varying the reaction temperature or changing the ligands, and size tunability was achieved as a function of only the concentration of added alkylammonium bromide salt.
Abstract: For varying the size of perovskite nanocrystals, variation in the reaction temperature and tuning the ligand chain lengths are established as the key parameters for high-temperature solution-processed synthesis. These also require sharp cooling for obtaining desired dimensions and optical stability. In contrast, using preformed alkylammonium bromide salt as the precise dimension-controlling reagent, wide window size tunable CsPbBr3 nanocrystals were reported without varying the reaction temperature or changing the ligands. The size tunability even with ∼1 nm step growth regimes was achieved as a function of only the concentration of added alkylammonium bromide salt. Not only the cube shape but also the width varied in the sheet structures. Because these nanostructures lose their optical stability and crystal phase on prolonged annealing, stabilizing these in high-temperature synthesis for all-inorganic lead halide perovskites is important and remains challenging. In this aspect, this method proved to be m...

138 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of alternative elements in replacing lead vis-a-vis the materials' properties and characteristics of solar cells based on the metal-substituted hybrid halide perovskites was summarized.
Abstract: The revolutionary impact of hybrid halide perovskites in the field of solution-based photovoltaics has made them one of the most-promising technologies for next-generation solar cells. However, such a breakthrough has natural drawbacks, since all these perovskite materials yielding high efficiency contain lead as a primary element in their chemical composition. There is hence a substantial hurdle for their acceptance in industries and society alike. Substitution of lead in the perovskite structure by a suitable nontoxic metal has therefore become one of the significant pivotal challenges associated with these wonder materials of the present decade. We hereby review the progress in this emerging field of research to summarize the influence of alternative elements in replacing lead vis-a-vis the materials' properties and characteristics of solar cells based on the metal-substituted hybrid halide perovskites. Moreover, we have discussed the prospects of next-generation of lead-free perovskites, namely 2D layered perovskites, defect ordered and double perovskites with a focus on their properties, stability, and photovoltaic applications.

136 citations


Journal ArticleDOI
TL;DR: The latest developments of ternary I-III-VI nanocrystals from their large-scale synthesis to device applications are presented and the future prospects of these materials in lighting applications are proposed.
Abstract: Quantum dots with fabulous size-dependent and color-tunable emissions remained as one of the most exciting inventories in nanomaterials for the last 3 decades. Even though a large number of such dot nanocrystals were developed, CdSe still remained as unbeatable and highly trusted lighting nanocrystals. Beyond these, the ternary I–III–VI family of nanocrystals emerged as the most widely accepted greener materials with efficient emissions tunable in visible as well as NIR spectral windows. These bring the high possibility of their implementation as lighting materials acceptable to the community and also to the environment. Keeping these in mind, in this Perspective, the latest developments of ternary I–III–VI nanocrystals from their large-scale synthesis to device applications are presented. Incorporating ZnS, tuning the composition, mixing with other nanocrystals, and doping with Mn ions, light-emitting devices of single color as well as for generating white light emissions are also discussed. In addition,...

133 citations


Journal ArticleDOI
TL;DR: The origin of photoluminescence of carbon dots is a debatable issue which is depend on the chemical structures such as graphitic conjugated core, molecular fluorophores and the surface defect states found to be dependent on the method of preparation as discussed by the authors.
Abstract: Fluorescent carbon dots (C-dots) are new class of nanomaterials with widespread applications in optoelectronics, bio-imaging, catalysis, and sensing. The origin of photoluminescence of carbon dots is a debatable issue which is pretend to depend on the chemical structures such as graphitic conjugated core, molecular fluorophores and the surface defect states found to be dependent on the method of preparation. In this review, we have illustrated the important issues and challenges of the luminescent carbon dots and their potential applications. Graphitic conjugated core containing carbon dots is being synthesized usually from bulk materials like graphite, graphene and graphene oxide which exhibit size dependent photoluminescence behaviour due to quantum confinement. On the other hand, carbon dots synthesized from small molecules exhibit excitation dependent emission due to the presence of surface energy trap states which can be tuned by surface modification. Again, presence of both conjugated core and surface defect generates dual emission property. It is evident that various molecular fluorophores are produced inside carbon dots during low temperature synthesis. Hetero-atom doping is another strategy to tune the photoluminescence properties of carbon dots. Red emitting carbon dots are found to be suitable for bio-imaging applications after surface modification. Again, high quantum yield and solar light absorbing carbon dots are required for light harvesting and optoelectronic applications. Surface modified carbon dots are found to be appropriate for sensing applications. Analysis reveals that carbon dots based hybrid systems provide good applicability towards construction of solar cell devices because of their efficient charge separation.

119 citations


Journal ArticleDOI
TL;DR: It is concluded that encapsulation of CsPbI2Br to exclude water vapor should be sufficient to stabilize the cubic brown phase, making the material of interest for use in practical PV devices.
Abstract: In this manuscript, the inorganic perovskite CsPbI2Br is investigated as a photovoltaic material that offers higher stability than the organic–inorganic hybrid perovskite materials. It is demonstrated that CsPbI2Br does not irreversibly degrade to its component salts as in the case of methylammonium lead iodide but instead is induced (by water vapor) to transform from its metastable brown cubic (1.92 eV band gap) phase to a yellow phase having a higher band gap (2.85 eV). This is easily reversed by heating to 350 °C in a dry environment. Similarly, exposure of unencapsulated photovoltaic devices to water vapor causes current (JSC) loss as the absorber transforms to its more transparent (yellow) form, but this is also reversible by moderate heating, with over 100% recovery of the original device performance. NMR and thermal analysis show that the high band gap yellow phase does not contain detectable levels of water, implying that water induces the transformation but is not incorporated as a major componen...

111 citations


Journal ArticleDOI
TL;DR: In this article, the step growth process of perovskite CsPbBr3 nanocrystals is reported with a step-rise of the reaction temperature with correlating annealing time.
Abstract: While the classical mechanism for the growth of colloidal chalcogenide nanocrystals is largely understood, fundamental insights for the growth of perovskite nanocrystals still remain elusive. Using nanoclusters of ∼0.6 nm diameter as monomers and growing to more than 25 nm in a single reaction, herein, the step growth process of perovskite CsPbBr3 nanocrystals is reported. This is performed with a step-rise of the reaction temperature with correlating annealing time. The growth is so precise that ∼0.6 nm (nearly one unit cell) increments were successively monitored in parallel with the conversion of clusters to nanowires and then to thickness tunable platelets and finally to size-tunable cube-shaped nanostructures. The entire reaction was monitored optically and microscopically, and their step growths were correlated. From these observations, the possible growth mechanism for perovskite nanocrystals along with their shape transformations was proposed.

94 citations


Journal ArticleDOI
TL;DR: An overview of the recent progress as well as promising future of metal/metal oxide nanoparticles supported over porous nanomaterials as heterogeneous catalysts for a wide spectrum of these CO2 fixation reactions is presented.
Abstract: CO2 is a major greenhouse gas responsible for global warming and can act as an abundant and inexpensive C1 source for enhancing the chain length/functionalization of a wide range of reactive organic molecules. It is moderately reactive, nontoxic and renewable. Thus, CO2 fixation reactions are important to meet the global challenges, that is, to mitigate the concentration of CO2 in the atmosphere through its fruitful utilization, which is of great interest from economic and environmental perspectives. Various metallic nanoparticles as well as metal oxides can be supported over high surface area porous materials and the resulting nanomaterial can act as heterogeneous and reusable solid catalyst for CO2 fixation reactions for the synthesis of a large number of fuels, natural products agrochemicals, and pharmaceutical compounds. Here we present an overview of the recent progress as well as promising future of metal/metal oxide nanoparticles supported over porous nanomaterials as heterogeneous catalysts for a wide spectrum of these CO2 fixation reactions.

89 citations


Journal ArticleDOI
TL;DR: By in situ use of alkylammonium chloride salt in high-temperature reactions, the surface binding was improved, and significant emission as well as the phase could be retained with successive purifications.
Abstract: High-energy-emitting CsPbCl3 nanocrystals have shown significant loss and enhancement of their emission intensity (∼40–50 folds) during purification and surface treatments, respectively. This confirms that the surfaces of these nanocrystals are very sensitive. In this Letter, physical insights of the interface bindings on the surface of these blue-emitting CsPbCl3 nanocrystals with different passivating agents and their consequential impact on purification are investigated. Using various metal chlorides irrespective of the charge and size of the metal ions, metal acetates, and nonmetal chloride, the predominant influence of chloride ions in helping retrieve/intensify the blue emission is established. The purification processes are observed to be very delicate, and successive purifications with introduction of polar nonsolvents led to the transformation of an emitting cubic CsPbCl3 phase to nonemitting tetragonal CsPb2Cl5 phase nanocrystals irreversibly. The impact of various salt additions only temporaril...

85 citations


Journal ArticleDOI
TL;DR: In this paper, a covalent organic framework (COF), TFPB-TAPT COF, is used as an anode with high capacity in rechargeable sodium batteries.
Abstract: Covalent organic frameworks (COFs) promise several benefits as materials in terms of gas adsorption, for use in optoelectronic devices, etc. However, the energy storage ability of COFs has not been well studied, especially in sodium batteries. In this report, for the first time, a covalent organic framework (COF), TFPB-TAPT COF, is used as an anode with high capacity in sodium batteries. The TFPB-TAPT COF exhibits an initial reversible capacity of 246 mA h g−1 and a capacity of 125 mA h g−1 is retained after 500 cycles. The TFPB-TAPT COF further exhibits Na+ ion storage capability at different current rates. The Na+ ion storage viability of the TFPB-TAPT COF arises mainly because of its open ordered nanoporous framework, which provides reversible accommodation for ions. This work opens up a promising new approach for further utilization of COFs as electrode materials in rechargeable sodium batteries.

82 citations


Journal ArticleDOI
TL;DR: In this article, the authors show that under strong periodic driving quantum interference may suppress the heating and may lead to a nonthermal state, remembering properties of the initial state until infinite time.
Abstract: Interacting many-body quantum systems are believed to heat up unboundedly under a periodic drive as there is no local conservation law to prevent this from happening. Here, the authors show that this belief may not be generally true. Their results indicate that under strong periodic driving quantum interference may suppress the heating and may lead to a nonthermal state, remembering properties of the initial state until infinite time. This is accounted for by the emergence of an approximately conserved local quantity. The freezing is more pronounced for smaller drive frequencies, putting it beyond the scope of conventionally used high-frequency expansions.

Journal ArticleDOI
TL;DR: In this paper, it was shown that the scalar coupled Gauss-Bonnet term alone is capable of driving the inflationary stages of the Universe without incorporating slow roll approximation, while remaining compatible with the current observations.
Abstract: We have explicitly demonstrated that scalar coupled Gauss-Bonnet gravity in four dimensions can have nontrivial effects on the early inflationary stage of our Universe. In particular, we have shown that the scalar coupled Gauss-Bonnet term alone is capable of driving the inflationary stages of the Universe without incorporating slow roll approximation, while remaining compatible with the current observations. Subsequently, to avoid the instability of the tensor perturbation modes we have introduced a self-interacting potential for the inflaton field and have shown that, in this context as well, it is possible to have an inflationary scenario. Moreover, it turns out that presence of the Gauss-Bonnet term is incompatible with the slow roll approximation and hence one must work with the field equations in the most general context. Finally, we have shown that the scalar coupled Gauss-Bonnet term attains smaller and smaller values as the Universe exits from inflation. Thus, at the end of the inflation, the Universe makes a smooth transition to Einstein gravity.

Journal ArticleDOI
TL;DR: In this paper, a green synthesis of gold nanoclusters with tunable emission wavelength from 590 to 510 nm in aqueous medium by core etching and ligand exchange method is reported.
Abstract: Gold nanoclusters (Au NCs) are new class of fluorescent nanomaterials with widespread applications in energy, water and healthcare. Here, we report a green synthesis of Au NCs with tunable emission wavelength from 590 to 510 nm in aqueous medium by core etching and ligand exchange method. Investigation reveals that the number of Au atoms present in the core of nanoclusters controls the emission wavelength. The quantum yield (QY) of nanoclusters increases from 0.57 to 3.15% with changing core from Au12 to Au6. Time resolved spectroscopic study reveals that the emission with higher lifetime (>100 ns) originates from ligand to metal charge transfer (LMCT; S to gold core of NCs). It is demonstrated that the highly green emitting NCs (Au-510) are more sensitive than orange emitting NCs (Au-590) toward Pb2+. The detection limit of Pb2+ is found to be 10 nM which is much lower than allowed concentration of Pb2+ in drinking water. Thus, Au NCs based optical sensor is promising for the selective detection of Pb2+ ...

Journal ArticleDOI
TL;DR: A series of mononuclear iron porphyrin complexes are rationally designed to achieve efficient O-O bond activation and site-selective proton transfer to effect facile and selective electrochemical reduction of O2 to water with rate constants higher than all known heme/Cu complexes.
Abstract: Facile and selective 4e–/4H+ electrochemical reduction of O2 to H2O in aqueous medium has been a sought-after goal for several decades Elegant but synthetically demanding cytochrome c oxidase mimics have demonstrated selective 4e–/4H+ electrochemical O2 reduction to H2O is possible with rate constants as fast as 105 M–1 s–1 under heterogeneous conditions in aqueous media Over the past few years, in situ mechanistic investigations on iron porphyrin complexes adsorbed on electrodes have revealed that the rate and selectivity of this multielectron and multiproton process is governed by the reactivity of a ferric hydroperoxide intermediate The barrier of O—O bond cleavage determines the overall rate of O2 reduction and the site of protonation determines the selectivity In this report, a series of mononuclear iron porphyrin complexes are rationally designed to achieve efficient O—O bond activation and site-selective proton transfer to effect facile and selective electrochemical reduction of O2 to water In

Journal ArticleDOI
TL;DR: In this article, the steady state density matrix of a non-integrable system, averaged over the reset distribution, retains its off-diagonal elements for any finite time interval.
Abstract: We study nonequilibrium dynamics of integrable and nonintegrable closed quantum systems whose unitary evolution is interrupted with stochastic resets, characterized by a reset rate $r$, that project the system to its initial state. We show that the steady-state density matrix of a nonintegrable system, averaged over the reset distribution, retains its off-diagonal elements for any finite $r$. Consequently a generic observable $\stackrel{\ifmmode \hat{}\else \^{}\fi{}}{O}$, whose expectation value receives a contribution from these off-diagonal elements, never thermalizes under such dynamics for any finite $r$. We demonstrate this phenomenon by exact numerical studies of experimentally realizable models of ultracold bosonic atoms in a tilted optical lattice. For integrable Dirac-like fermionic models driven periodically between such resets, the reset-averaged steady state is found to be described by a family of generalized Gibbs ensembles characterized by $r$. We also study the spread of particle density of a noninteracting one-dimensional fermionic chain, starting from an initial state where all fermions occupy the left half of the sample, while the right half is empty. When driven by resetting dynamics, the density profile approaches at long times to a nonequilibrium stationary profile that we compute exactly. We suggest concrete experiments that can possibly test our theory.

Journal ArticleDOI
TL;DR: CPPhen was self-assembled at a dynamic air-water interface with a vortex motion to afford molecular nanosheets, which were then carbonized under inert gas flow and retained after carbonization, which has never been seen for low-molecular weight compounds.
Abstract: Two-dimensional (2D) carbon nanomaterials possessing promising physical and chemical properties find applications in high-performance energy storage devices and catalysts. However, large-scale fabrication of 2D carbon nanostructures is based on a few specific carbon templates or precursors and poses a formidable challenge. Now a new bottom-up method for carbon nanosheet fabrication using a newly designed anisotropic carbon nanoring molecule, CPPhen, is presented. CPPhen was self-assembled at a dynamic air-water interface with a vortex motion to afford molecular nanosheets, which were then carbonized under inert gas flow. Their nanosheet morphologies were retained after carbonization, which has never been seen for low-molecular weight compounds. Furthermore, adding pyridine as a nitrogen dopant in the self-assembly step successfully afforded nitrogen-doped carbon nanosheets containing mainly pyridinic nitrogen species.

Journal ArticleDOI
TL;DR: In this article, a new porous extended network π-conjugated TFP-NDA-COF via solvothermal Schiff base condensation of 1,3,5-triformylphloroglucinol (TFP) with 1,5,diaminonaphthalene (NDA).

Journal ArticleDOI
TL;DR: In this paper, a unique core-shell nanostructured oxygen evolution reaction (OER) catalyst composed of an electrochemically inactive crystalline iron oxide core and an active amorphous nickel phosphide shell is presented, and this catalyst results in superior OER activity.
Abstract: A unique core–shell nanostructured oxygen evolution reaction (OER) catalyst composed of an electrochemically inactive crystalline iron oxide core and an active amorphous nickel phosphide shell is presented, and this catalyst results in superior OER activity. Even activators enhancing the activity of the OER catalyst by promoting the redox reactions are reported, but here the exclusive position of iron in the nanostructures indeed boosted the efficiency due to ideal placement. Moreover, these nanostructures are also prepared in a sophisticated mechanistic approach in which selectively one metal is phosphidated and the other is not. Interestingly, in the absence of iron, nickel phosphide crystallized in a different shape, but in the presence of iron, this specifically formed amorphous NixP became more efficient for promoting the OER. Details of the formation of this active catalyst are studied; the electrochemical reactions are investigated, and the OER activity is compared with that of different leading me...

Journal ArticleDOI
TL;DR: The design and synthesis of a crescent-shaped thiazole peptide is delineated that preferentially stabilizes c-MYC quadruplex over other promoter G-quadruplexes and inhibits c- MYC oncogene expression and antiproliferative activities by inducing S phase cell cycle arrest and apoptosis.
Abstract: The structural differences among different G-quadruplexes provide an opportunity for site-specific targeting of a particular G-quadruplex structure. However, majority of G-quadruplex ligands described thus far show little selectivity among different G-quadruplexes. In this work, we delineate the design and synthesis of a crescent-shaped thiazole peptide that preferentially stabilizes c-MYC quadruplex over other promoter G-quadruplexes and inhibits c-MYC oncogene expression. Biophysical analysis such as Forster resonance energy transfer (FRET) melting and fluorescence spectroscopy show that the thiazole peptide TH3 can selectively interact with the c-MYC G-quadruplex over other investigated G-quadruplexes and duplex DNA. NMR spectroscopy reveals that peptide TH3 binds to the terminal G-quartets and capping regions present in the 5'- and 3'-ends of c-MYC G-quadruplex with a 2:1 stoichiometry; whereas structurally related distamycin A is reported to interact with quadruplex structures via groove binding and end stacking modes with 4:1 stoichiometry. Importantly, qRT-PCR, western blot and dual luciferase reporter assay show that TH3 downregulates c-MYC expression by stabilizing the c-MYC G-quadruplex in cancer cells. Moreover, TH3 localizes within the nucleus of cancer cells and exhibits antiproliferative activities by inducing S phase cell cycle arrest and apoptosis.

Journal ArticleDOI
TL;DR: In this paper, a flat-shaped pristine fcc ruthenium nanoparticles having a large fraction of atomically active {111} facets exposed on their flat surfaces have been developed that act as a highly selective and reusable heterogeneous catalyst for the production of various primary amines at exceedingly high reaction rates by the low temperature reductive amination of carbonyl compounds.
Abstract: The creation of metal catalysts with highly active surfaces is pivotal to meeting the strong economic demand of the chemical industry. Specific flat-shaped pristine fcc ruthenium nanoparticles having a large fraction of atomically active {111} facets exposed on their flat surfaces have been developed that act as a highly selective and reusable heterogeneous catalyst for the production of various primary amines at exceedingly high reaction rates by the low temperature reductive amination of carbonyl compounds. The high performance of the catalyst is attributed to the large fraction of metallic Ru serving as active sites with weak electron donating ability that prevail on the surface exposed {111} facets of flat-shaped fcc Ru nanoparticles. This catalyst exhibits a highest turnover frequency (TOF) of ca. 1850 h−1 for a model reductive amination of biomass derived furfural to furfurylamine and provides a reaction rate approximately six times higher than that of an efficient and selective support catalyst of Ru-deposited Nb2O5 (TOF: ca. 310 h−1).

Journal ArticleDOI
TL;DR: In this paper, the quantum dots are co-doped by nitrogen and sulphur to produce a large number of localized energy levels near conduction band near the conduction bands, and a remarkable enhancement in fluorescence quenching effect compared to their individual doped states either by nitrogen or sulphur is observed using only 90μM solution of 2,4,6-trinitro phenol (TNP) via charge transfer among these doped state.
Abstract: Study of sensing properties of nitroexplosives using luminescent carbon based quantum dots is an interesting area of research. Enhancement in sensing ability exploiting edge states and doped states in quantum dots is an elegant approach. In the present work, graphene quantum dots (GQD) are co-doped by nitrogen and sulphur to produce large number of localized energy levels near conduction band. Remarkable enhancement in fluorescence quenching effect compared to their individual doped states either by nitrogen or sulphur is observed using only 90 μM solution of 2,4,6-trinitro phenol (TNP) via charge transfer among these doped states to detect trinitrophenol selectively. The detection limit has been calculated to about 19.05 ppb. The origin of this ultra high fluorescence quenching and low detection limit is the presence of electron rich edge states due to ‘N’ and ‘S’ dopants as verified by Zeta potential results.

Journal ArticleDOI
TL;DR: In this article, the authors derived the evolution equation for gravitational perturbation in four-dimensional spacetime in the presence of a spatial extra dimension, which inherits nontrivial higher-dimensional effects.
Abstract: In this work, we have derived the evolution equation for gravitational perturbation in four-dimensional spacetime in the presence of a spatial extra dimension. The evolution equation is derived by perturbing the effective gravitational field equations on the four-dimensional spacetime, which inherits nontrivial higher-dimensional effects. Note that this is different from the perturbation of the five-dimensional gravitational field equations that exist in the literature and possess quantitatively new features. The gravitational perturbation has further been decomposed into a purely four-dimensional part and another piece that depends on extra dimensions. The four-dimensional gravitational perturbation now admits massive propagating degrees of freedom, owing to the existence of higher dimensions. We have also studied the influence of these massive propagating modes on the quasinormal mode frequencies, signaling the higher-dimensional nature of the spacetime, and have contrasted these massive modes with the massless modes in general relativity. Surprisingly, it turns out that the massive modes experience damping much smaller than that of the massless modes in general relativity and may even dominate over and above the general relativity contribution if one observes the ringdown phase of a black hole merger event at sufficiently late times. Furthermore, the whole analytical framework has been supplemented by the fully numerical Cauchy evolution problem, as well. In this context, we have shown that, except for minute details, the overall features of the gravitational perturbations are captured both in the Cauchy evolution as well as in the analysis of quasinormal modes. The implications on observations of black holes with LIGO and proposed space missions such as LISA are also discussed.

Journal ArticleDOI
01 Jan 2018-Small
TL;DR: A facile new synthetic method of forming WO3 from tungsten sulfide, WS2 is reported and the negative differential resistance (NDR) property of both WO2 and WO4 is reported for the first time and NDR is explained with density of state approach.
Abstract: Tungsten oxide (WO3 ) is an emerging 2D nanomaterial possessing unique physicochemical properties extending a wide spectrum of novel applications which are limited due to lack of efficient synthesis of high-quality WO3 . Here, a facile new synthetic method of forming WO3 from tungsten sulfide, WS2 is reported. Spectroscopic, microscopic, and X-ray studies indicate formation of flower like aggregated nanosized WO3 plates of highly crystalline cubic phase via intermediate orthorhombic tungstite, WO3. H2 O phase. The charge storage ability of WO3 is extremely high (508 F g-1 at current density of 1 A g-1 ) at negative potential range compared to tungstite (194 F g-1 at 1 A g-1 ). Moreover, high (97%) capacity retention after 1000 cycles and capacitive charge storage nature of WO3 electrode suggest its supremacy as a negative electrode of supercapacitors. The asymmetric supercapacitor, based on the WO3 as a negative electrode and mildly reduced graphene oxide as a positive electrode, manifests high energy density of 218.3 mWhm-2 at power density 1750 mWm-2 , and exceptionally high power density, 17 500 mW m-2 , with energy density of 121.5 mWh m-2 . Furthermore, the negative differential resistance (NDR) property of both WO3 and WO3 .H2 O are reported for the first time and NDR is explained with density of state approach.

Journal ArticleDOI
TL;DR: TPDA-1 as discussed by the authors was synthesized via solvothermal Schiff base condensation reaction between two organic monomers, i.e., 2,4,6-trihydroxyisophthalaldehyde and 1,3,5-tris(4-aminophenyl)triazine.
Abstract: The new porous polymer TPDA-1 has been synthesized via solvothermal Schiff base condensation reaction between two organic monomers, i.e., 2,4,6-trihydroxyisophthalaldehyde and 1,3,5-tris(4-aminophenyl)triazine. The TPDA-1 material showed a very high specific capacitance of 469.4 F g–1, at 2 mV s–1 scan rate, together with a high specific surface area of 545 m2 g–1. It also exhibited excellent cyclic stability with 95% retention of its initial specific capacitance after 1000 cycles at 5 A g–1, suggesting its potential as a high performance supercapacitor. Extended π-conjugation and ion conduction inside the micropores throughout the whole polymeric matrix and high BET surface area could be responsible for this high supercapacitor performance in energy storage device. TPDA-1 has been characterized thoroughly by various electrochemical techniques such as cyclic voltammetry, galvanic charge–discharge, and electrochemical impedance spectroscopy. Our experimental results suggested a high potential of this porou...

Journal ArticleDOI
TL;DR: In this paper, the authors present the current progress in co-doping studies with critically summarized results to gain an overview, especially regarding the electrical properties of transparent conducting oxide (TCO) thin film.

Journal ArticleDOI
22 Feb 2018
TL;DR: Some of the history and the recent developments of guanosine-based supramolecular hydrogels and their applications are highlighted.
Abstract: Hydrogels are attractive materials for designing sensors, catalysts, scaffolds for tissue engineering, stimuli responsive soft materials, and controlled-release drug delivery systems. In recent years, self-assembly of guanosine and its derivatives has received immense interests for devising programmable supramolecular biomaterials including hydrogels. This perspective highlights some of the history and the recent developments of guanosine-based supramolecular hydrogels and their applications. Future prospects and scope of the guanosine-based hydrogels have also been discussed.

Journal ArticleDOI
TL;DR: In this paper, a plasticized PMMA-LiClO4 based solid polymer nano-composite electrolytes were prepared for different concentrations of TiO2 nano-particles using standard solution cast technique.

Journal ArticleDOI
TL;DR: In this article, Nanocrystalline MgO has been synthesized by simple precipitation method followed by calcination at 450 °C, which indicated the presence of mesoscopic void space and excellent catalytic activity for the synthesis of organic cyclic carbonates by chemical fixation of CO2 on a wide range of epoxides.

Journal ArticleDOI
TL;DR: Interestingly, using a calculated amount of preformed alkylammonium halides as dual passivating agents, the nanocrystals of both CsPbCl3 and CspbBr3 could even be stabilized for hours of annealing at 250 °C and recorded ∼51% absolutely quantum yield.
Abstract: Annealing perovskite nanocrystals at high reaction temperature changes their crystal phase, shape, and optical properties. Carrying out reactions between 180 and 250 °C, the impact of thermal annealing for CsPbCl3 and CsPbBr3 nanocrystals in a reaction flask was investigated here. At higher temperature, a phase change was observed instantly, which could not be trapped even with ice-bath cooling. Interestingly, using a calculated amount of preformed alkylammonium halides as dual passivating agents, the nanocrystals of both CsPbCl3 and CsPbBr3 could even be stabilized for hours of annealing at 250 °C. CsPbCl3, which was reported to be a poor emissive nanocrystal in comparison to CsPbBr3, could sustain even more than 5 h of annealing at 250 °C and recorded ∼51% absolutely quantum yield. Details of the interface chemistry and the role of the used dual passivating agent for providing thermal stability are studied and reported in this Letter.

Journal ArticleDOI
TL;DR: In this article, the impact of dopant ions on tuning the doped platelet dimensions and retaining the monodispersity is reported, which is performed by designing appropriate compositions of layered perovskites, L2(Pb1-xMnx)Cl4, which on thermal treatment were transformed to Mn-doped CsPbCl3 platelets.
Abstract: Doped perovskite nanocrystals have recently emerged as a new class of energy materials for solar concentrators and solid-state lighting device applications. Among these, doping Mn(II) in high band gap CsPbCl3 perovskite host nanostructures has been extensively studied. However, going beyond their optical emissions, herein, the impact of dopant ions on tuning the doped platelet dimensions and retaining the monodispersity is reported. These were performed by designing appropriate compositions of layered perovskites, L2(Pb1–xMnx)Cl4, which on thermal treatment in the presence of Cs(I) ions transformed to Mn-doped CsPbCl3 platelets. Correlating the amount of Mn present in layered perovskites and retained in doped platelets, the role of Mn for the conversion of layered to doped perovskites was established. These doped platelets showed dominated Mn d–d emission and also Mn concentration-dependent emission tuning. Even though several reports of Mn-doped CsPbCl3 have been reported, these findings add new fundamen...