Showing papers by "Indian Association for the Cultivation of Science published in 2014"
TL;DR: In this article, a review focusing on the out-of-the-box synthetic techniques capable of deriving hierarchical porous carbons (HPCs) with superior application profiles is presented.
Abstract: Hierarchically porous carbons (HPCs) with 1D to 3D network are attracting vast interest due to their potential technological application profile ranging from electrochemical capacitors, lithium ion batteries, solar cells, hydrogen storage systems, photonic material, fuel cells, sorbent for toxic gas separation and so on. Natural raw-materials such as biomass-biopolymer derived hierarchical nanostructured carbons are especially attractive for their uniform pore dimensions which can be adjustable over a wide range of length scales. Good electrical conductivity, high surface area, and excellent chemical stability are unique physicochemical properties which are responsible for micro/nanostructured porous carbon to be highly trusted candidate for emerging nanotechnologies. This review focuses on the ‘out-of-the-box’ synthetic techniques capable of deriving HPC with superior application profiles. The article presents the promising scope of accessing HPCs from (1) hard-templating, soft-templating, and non-templating routes, (2) biopolymers with a major focus on non-templating strategies. Subsequently, emerging strategies of hetero-atom doping in porous carbon nanostructures are discussed. The review will highlight the contribution of synergistic effect of macro–meso–micropores on a range of emerging applications such as CO2 capture, carbon photonic crystal sensors, Li–S batteries, and supercapacitor. Mechanism of ion transport and buffering, electrical double layer enhancement have been discussed in the context of pore structure and shapes. We will also show the differences of HPC and ordered mesoporous carbon (OMC) in terms of their synthesis strategies and choices of template for self-assembly. How the remarkable mechanical strength of the HPCs can be achieved by selecting self-assembling template, whereas collapse of mesostructure via decomposition of framework occurs due to poor thermal stability or high N-content of the carbon source will be discussed.
1,152 citations
TL;DR: It is shown that for generic nonintegrable interacting systems, local observables become independent of the initial state entirely.
Abstract: When a closed quantum system is driven periodically with period $T$, it approaches a periodic state synchronized with the drive in which any local observable measured stroboscopically approaches a steady value. For integrable systems, the resulting behavior is captured by a periodic version of a generalized Gibbs ensemble. By contrast, here we show that for generic nonintegrable interacting systems, local observables become independent of the initial state entirely. Essentially, this happens because Floquet eigenstates of the driven system at quasienergy ${\ensuremath{\omega}}_{\ensuremath{\alpha}}$ consist of a mixture of the exponentially many eigenstates of the undriven Hamiltonian, which are thus drawn from the entire extensive undriven spectrum. This is a form of equilibration which depends only on the Hilbert space of the undriven system and not on any details of its Hamiltonian.
428 citations
TL;DR: Various supramolecular designs that utilize organic donor-acceptor CT complexation to generate noncovalently co-assembled structures including fibrillar gels, micelles, vesicles, nanotubes, foldamers, conformationally restricted macromolecules, and liquid crystalline phases are collated.
Abstract: We have collated various supramolecular designs that utilize organic donor–acceptor CT complexation to generate noncovalently co-assembled structures including fibrillar gels, micelles, vesicles, nanotubes, foldamers, conformationally restricted macromolecules, and liquid crystalline phases. Possibly inspired by nature, chemists have extensively used hydrogen bonding as a tool for supramolecular assemblies of a diverse range of abiotic building blocks. As a structural motif, CT complexes can be compared to hydrogen-bonded complexes in its directional nature and complementarities. Additional advantages of CT interactions include wider solvent tolerance and easy spectroscopic probing. Nevertheless the major limitation is their low association constant. This article shows different strategies have evolved over the years to overcome this drawback by reinforcing the CT interactions with auxiliary noncovalent forces without hampering the alternate stacking mode. Emerging reports on promising CT complexes in organic electronics are intimately related to various supramolecular designs that one can postulate based on donor–acceptor CT interactions.
369 citations
TL;DR: The challenges and progress in the field of silicene research are summarized and theoretical calculations have predicted thatsilicene possesses graphene-like properties such as massless Dirac fermions that carry charge and the quantum spin Hall effect.
Abstract: The discovery of graphene and its remarkable and exotic properties have aroused interest in other elements and molecules that form 2D atomic layers, such as metal chalcogenides, transition metal oxides, boron nitride, silicon, and germanium. Silicene and germanene, the Si and Ge counterparts of graphene, have interesting fundamental physical properties with potential applications in technology. For example, researchers expect that silicene will be relatively easy to incorporate within existing silicon-based electronics.In this Account, we summarize the challenges and progress in the field of silicene research. Theoretical calculations have predicted that silicene possesses graphene-like properties such as massless Dirac fermions that carry charge and the quantum spin Hall effect. Researchers are actively exploring the physical and chemical properties of silicene and tailoring it for wide variety of applications.The symmetric buckling in each of the six-membered rings of silicene differentiates it from gra...
299 citations
TL;DR: In this paper, the effect of carbon nanomaterial doping on the photophysical behavior of carbon dots has been analyzed by using steady-state and time-resolved spectroscopy, and it has been shown that carbon dots with boron co-doped with nitrogen have a higher QY with an average decay time of 12.8 ns.
Abstract: Doping in carbon nanomaterial with various hetero atoms draws attention due to their tunable properties. Herein, we have synthesized nitrogen containing carbon dots [C-dots (N)], phosphorus co-doped nitrogen containing carbon dots [C-dots (N, P)], and boron co-doped nitrogen containing carbon dots [C-dots (N, B)]; and detailed elemental analysis has been unveiled by X-ray photoelectron spectroscopy (XPS) measurements. Our emphasis is given to understand the effect of doping on the photophysical behavior of carbon dots by using steady-state and time-resolved spectroscopy. Nitrogen containing carbon dots have quantum yield (QY) of 64.0% with an average decay time of 12.8 ns. Photophysical properties (radiative decay rate and average decay time) are found to be increased for phosphorus co-doping carbon dots due to extra electron incorporation for n-type doping (phosphorus dopant) to carbon dots which favors the radiative relaxation pathways. On the contrary, boron (p-type dopant) co-doping with nitrogen cont...
258 citations
TL;DR: The rationale for developing TDP inhibitors for combinations with topoisomerase inhibitors, as well as the relevance of TDP1 and TDP2 as determinants of response to anticancer agents, are discussed.
242 citations
TL;DR: This brief review focuses on the molecular mechanism of ceRNA as part of the complex post-transcriptional regulatory circuit in cell and the impact of ceRNAs in development and disease.
Abstract: Competing endogenous RNA, ceRNA, vie with messenger RNAs (mRNAs) for microRNAs (miRNAs) with shared miRNAs responses elements (MREs) and act as modulator of miRNA by influencing the available level of miRNA. It has recently been discovered that, apart from protein-coding ceRNAs, pseudogenes, long noncoding RNAs (lncRNAs), and circular RNAs act as miRNA “sponges” by sharing common MRE, inhibiting normal miRNA targeting activity on mRNA. These MRE sharing elements form the posttranscriptional ceRNA network to regulate mRNA expression. ceRNAs are widely implicated in many biological processes. Recent studies have identified ceRNAs associated with a number of diseases including cancer. This brief review focuses on the molecular mechanism of ceRNA as part of the complex post-transcriptional regulatory circuit in cell and the impact of ceRNAs in development and disease.
235 citations
TL;DR: It is found that photocatalytic efficiency by rGO-Ag under visible light is significantly higher compared to that of rGO or silver nanoparticles, and proposed that Ag nanoparticles offer visible-light-induced excitation of silver plasmons, and conductive rGO offers efficient charge separation and thus induces oxidative degradation of the organic pollutant.
Abstract: Sunlight-induced degradation of organic pollutants is an ideal approach for environmental pollution control and wastewater treatment. Although a variety of photocatalysts have been designed toward this goal, efficient degradation of colorless organic pollutants by visible light is a challenging issue. Here, we show that a reduced graphene oxide (rGO)-based composite with silver nanoparticle (rGO–Ag) can act as an efficient visible-light photocatalyst for the degradation of colorless organic pollutants. We have developed a simple, large-scale synthesis method for rGO–Ag and used it for the degradation of three well-known endocrine disruptors (phenol, bisphenol A, and atrazine) under UV and visible light. It is found that photocatalytic efficiency by rGO–Ag under visible light is significantly higher compared to that of rGO or silver nanoparticles. It is proposed that Ag nanoparticles offer visible-light-induced excitation of silver plasmons, and conductive rGO offers efficient charge separation and thus in...
182 citations
TL;DR: It is analytically show that, for a class of integrable systems, the relevant ensemble is constructed by maximizing an appropriately defined entropy subject to constraints, which is explicitly identified.
Abstract: The nature of the behavior of an isolated many-body quantum system periodically driven in time has been an open question since the beginning of quantum mechanics. After an initial transient period, such a system is known to synchronize with the driving; in contrast to the nondriven case, no fundamental principle has been proposed for constructing the resulting nonequilibrium state. Here, we analytically show that, for a class of integrable systems, the relevant ensemble is constructed by maximizing an appropriately defined entropy subject to constraints, which we explicitly identify. This result constitutes a generalization of the concepts of equilibrium statistical mechanics to a class of far-from-equilibrium systems, up to now mainly accessible using ad hoc methods.
181 citations
TL;DR: It is believed this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.
Abstract: Among different nitro compounds, trinitrophenol (TNP) is the most common constituent to prepare powerful explosives all over the world. A few works on the detection of nitro explosives have already been reported in the past few years; however, selectivity is still in its infant stage. As all the nitroexplosives are highly electron deficient in nature, it is very difficult to separate one from a mixture of different nitro compounds by the usual photoinduced electron transfer (PET) mechanism. In the present work, we have used a bright luminescent, 2,6-diamino pyridine functionalized graphene oxide (DAP-RGO) for selective detection of TNP in the presence of other nitro compounds. The major advantage of using this material over other reported materials is not only to achieve very high fluorescence quenching of ∼96% but also superior selectivity >80% in the detection of TNP in aqueous medium via both fluorescence resonance energy transfer and PET mechanisms. Density functional theory calculations also suggest the occurrence of an effective proton transfer mechanism from TNP to DAP-RGO, resulting in this tremendous fluorescence quenching compared to other nitro compounds. We believe this graphene based composite will emerge a new class of materials that could be potentially useful for selective detection, even for trace amounts of nitro explosives in water.
173 citations
TL;DR: A series of amphiphilic tyrosine based self-healable, multi-stimuli responsive metallo-hydrogels have been discovered that are highly selective to Ni(2+) ions.
TL;DR: In this article, the presence of a substantial amount of hydroxyl groups attached to the Zn lattice has been correlated to the dominant c-axis orientation of ZnO crystals which exhibited a distinct UV luminescence band that arises due to the typical exciton emission.
Abstract: Substantial c-axis orientation of the hexagonal ZnO crystals with wurtzite structure demonstrates only those two preferred peaks in the first-order spectra which are permitted by the Raman scattering selection rule viz., the Ehigh2 and A1 (LO) modes, that identify the improved structural quality of the undoped ZnO film grown by magnetron sputtering in Ar ambient at an RF power of P = 200 W. The presence of a substantial amount of hydroxyl groups attached to the Zn lattice has been correlated to the dominant c-axis orientation of the ZnO crystals which exhibited a distinct UV luminescence band that arises due to the typical exciton emission or near-band-edge emission. At higher applied powers, disorder-activated Raman scattering introduces a well resolved Bhigh1 mode and gradually growing second order Raman peaks, (Ehigh2 − Elow2) and (Bhigh1 − Blow1), which are caused by the breakdown of translational symmetry of the lattice by defects or impurities and lead to deviation from preferred c-axis orientation with I002/I103 < 1. Out diffusion of oxygen from the network creates increasing oxygen vacancy states and in addition, various other defects e.g., Zn interstitial , doubly ionized Zn vacancy and oxygen antisite (OZn) as the dynamic acceptor defects, act as the origins of different visible photoluminescence components classified in the UV-violet, violet, violet-blue, blue and green regions.
TL;DR: In this article, a stable fluorescent MOF, Zn2(NDC)2(bpy)]·Gx, was reported, whose fluorescence was quenched by trace amounts of nitro aromatics introduced from solution or in vapor phase.
Abstract: Nitro aromatics are the principal components of explosives used in acts of terrorism and within improvised explosive devices, among others. Although high sensitivity towards nitro aromatic explosives has been demonstrated, selective detection and discrimination are critical for practical applications. Fluorescence quenching of metal–organic frameworks (MOFs) is sufficiently sensitive to detect any nitro explosives, but discriminative detection with different numbers of –NO2 groups is rare. Here we report a stable fluorescent MOF, [Zn2(NDC)2(bpy)]·Gx, 1 (where NDC = 2,6-naphthalenedicarboxylic acid, bpy = 4,4′-bipyridine, and G = guest solvent molecules), whose fluorescence is quenched by trace amounts of nitro aromatics introduced from solution or in vapor phase. The steady-state and time-resolved experiments show that the quenching process is dynamic in nature and the interactions (dipole–dipole, π-stacking) between the MOF and nitro explosives play a crucial role in the discriminative detection of nitro aromatics with different numbers of –NO2 groups.
TL;DR: PARP1 is identified as a key component driving the repair of trapped Top1cc by TDP1, and is shown to play a critical role in this process.
Abstract: Poly(ADP-ribose) polymerases (PARP) attach poly(ADP-ribose) (PAR) chains to various proteins including themselves and chromatin. Topoisomerase I (Top1) regulates DNA supercoiling and is the target of camptothecin and indenoisoquinoline anticancer drugs, as it forms Top1 cleavage complexes (Top1cc) that are trapped by the drugs. Endogenous and carcinogenic DNA lesions can also trap Top1cc. Tyrosyl-DNA phosphodiesterase 1 (TDP1), a key repair enzyme for trapped Top1cc, hydrolyzes the phosphodiester bond between the DNA 3′-end and the Top1 tyrosyl moiety. Alternative repair pathways for Top1cc involve endonuclease cleavage. However, it is unknown what determines the choice between TDP1 and the endonuclease repair pathways. Here we show that PARP1 plays a critical role in this process. By generating TDP1 and PARP1 double-knockout lymphoma chicken DT40 cells, we demonstrate that TDP1 and PARP1 are epistatic for the repair of Top1cc. The N-terminal domain of TDP1 directly binds the C-terminal domain of PARP1, and TDP1 is PARylated by PARP1. PARylation stabilizes TDP1 together with SUMOylation of TDP1. TDP1 PARylation enhances its recruitment to DNA damage sites without interfering with TDP1 catalytic activity. TDP1–PARP1 complexes, in turn recruit X-ray repair cross-complementing protein 1 (XRCC1). This work identifies PARP1 as a key component driving the repair of trapped Top1cc by TDP1.
TL;DR: The catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core-shell structure, and the rate is dependent on the size of the core of the nanoparticles.
Abstract: Bimetallic core–shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core–shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core–shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV–vis study confirm the formation of core–shell nanoparticles. We have examined the catalytic activity of these core–shell nanostructures in the reaction between 4-nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core–shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core–shell nanoparticles, and the Au100/Ag bimet...
TL;DR: In this article, the likelihood of an lncRNA-mRNA pair for actually being ceRNA was estimated by using hypergeometric test using the ratio of the number of shared MREs between the pair with the total number of mREs of the individual candidate gene.
Abstract: Long noncoding RNA (lncRNA) influences post-transcriptional regulation by interfering with the microRNA (miRNA) pathways, acting as competing endogenous RNA (ceRNA). These lncRNAs have miRNA responsive elements (MRE) in them, and control endogenous miRNAs available for binding with their target mRNAs, thus reducing the repression of these mRNAs. lnCeDB provides a database of human lncRNAs (from GENCODE 19 version) that can potentially act as ceRNAs. The putative mRNA targets of human miRNAs and the targets mapped to AGO clipped regions are collected from TargetScan and StarBase respectively. The lncRNA targets of human miRNAs (up to GENCODE 11) are downloaded from miRCode database. miRNA targets on the rest of the GENCODE 19 lncRNAs are predicted by our algorithm for finding seed-matched target sites. These putative miRNA-lncRNA interactions are mapped to the Ago interacting regions within lncRNAs. To find out the likelihood of an lncRNA-mRNA pair for actually being ceRNA we take recourse to two methods. First, a ceRNA score is calculated from the ratio of the number of shared MREs between the pair with the total number of MREs of the individual candidate gene. Second, the P-value for each ceRNA pair is determined by hypergeometric test using the number of shared miRNAs between the ceRNA pair against the number of miRNAs interacting with the individual RNAs. Typically, in a pair of RNAs being targeted by common miRNA(s), there should be a correlation of expression so that the increase in level of one ceRNA results in the increased level of the other ceRNA. Near-equimolar concentration of the competing RNAs is associated with more profound ceRNA effect. In lnCeDB one can not only browse for lncRNA-mRNA pairs having common targeting miRNAs, but also compare the expression of the pair in 22 human tissues to estimate the chances of the pair for actually being ceRNAs. Availability: Downloadable freely from http://gyanxet-beta.com/lncedb/.
TL;DR: Interestingly, MTT assay of these gelator molecules shows almost 100% cell viability of this peptide gelator, indicating its noncytotoxicity.
Abstract: A new synthetic tripeptide-based hydrogel has been discovered at physiological pH and temperature. This hydrogel has been thoroughly characterized using different techniques including field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, small- and wide-angle X-ray diffraction analyses, FT-IR, circular dichroism, and rheometric analyses. Moreover, this gel exhibits thixotropy and injectability. This hydrogel has been used for entrapment and sustained release of an antibiotic vancomycin and vitamin B12 at physiological pH and temperature for about 2 days. Interestingly, MTT assay of these gelator molecules shows almost 100% cell viability of this peptide gelator, indicating its noncytotoxicity.
TL;DR: Curcumin-functionalized gold nanoparticles (Au-curcumin) of hydrodynamic diameter 10-25 nm are reported, which serve to inhibit amyloids fibrillation and disintegrate/dissolve amyloid fibrils, implying that nanoparticle-based artificial molecular chaperones may offer a promising therapeutic approach to combat neurodegenerative disease.
Abstract: Inhibition of amyloid fibrillation and clearance of amyloid fibrils/plaques are essential for the prevention and treatment of various neurodegenerative disorders involving protein aggregation. Herein, we report curcumin-functionalized gold nanoparticles (Au-curcumin) of hydrodynamic diameter 10-25 nm, which serve to inhibit amyloid fibrillation and disintegrate/dissolve amyloid fibrils. In nanoparticle form, curcumin is water-soluble and can efficiently interact with amyloid protein/peptide, offering enhanced performance in inhibiting amyloid fibrillation and dissolving amyloid fibrils. Our results imply that nanoparticle-based artificial molecular chaperones may offer a promising therapeutic approach to combat neurodegenerative disease.
TL;DR: The computer simulations indicate that gene density-dependent radial segregation of chromosomes arises as a robust consequence of differences in non-equilibrium activity across chromosomes, and it is shown that a variety of non-random positional distributions emerge through the interplay of such activity, nuclear shape and specific interactions of chromosomes with the nuclear envelope.
Abstract: Chromosomes within eukaryotic cell nuclei at interphase are not positioned at random, since gene-rich chromosomes are predominantly found towards the interior of the cell nucleus across a number of cell types. The physical mechanisms that could drive and maintain the spatial segregation of chromosomes based on gene density are unknown. Here, we identify a mechanism for such segregation, showing that the territorial organization of chromosomes, another central feature of nuclear organization, emerges naturally from our model. Our computer simulations indicate that gene density-dependent radial segregation of chromosomes arises as a robust consequence of differences in non-equilibrium activity across chromosomes. Arguing that such differences originate in the inhomogeneous distribution of ATP-dependent chromatin remodeling and transcription machinery on each chromosome, we show that a variety of non-random positional distributions emerge through the interplay of such activity, nuclear shape and specific interactions of chromosomes with the nuclear envelope. Results from our model are in reasonable agreement with experimental data and we make a number of predictions that can be tested in experiments.
TL;DR: Au-Bi2S3 heteronanostructure photocatalysts were designed in which the coupling of a metal plasmon and a semiconductor exciton aids the absorption of solar light, enhances charge separation, and results in improved catalytic activity.
Abstract: Au-Bi2S3 heteronanostructure photocatalysts were designed in which the coupling of a metal plasmon and a semiconductor exciton aids the absorption of solar light, enhances charge separation, and results in improved catalytic activity. Furthermore, these nanostructures show a unique pattern of structural combination, with Au nanoparticles positioned at the center of Bi2S3 nanorods. The chemistry of formation of these nanostructures, their epitaxy at the junction, and their photoconductance were studied, as well as their photoresponse properties.
TL;DR: Palladium nanoparticles (Pd NPs) have been grafted at the surfaces of a Co-containing metal-organic framework material MCoS-1, which has been characterized by HR TEM, XPS and EPR spectroscopic analyses as discussed by the authors.
Abstract: Palladium nanoparticles (Pd NPs) have been grafted at the surfaces of a Co-containing metal–organic framework material MCoS-1. The Pd NPs grafted material Pd(0)/MCoS-1 has been characterized by HR TEM, XPS and EPR spectroscopic analyses. Pd(0)/MCoS-1 showed excellent catalytic activities in Suzuki–Miyaura cross-coupling reaction for the synthesis of a diverse range of biaryl organics in water. Sonogashira cross-coupling between terminal alkynes and aryl halides has also been carried out over this Pd-nanocatalyst in water without the addition of any Cu co-catalyst. In both reactions the catalyst is easily recoverable and can be reused for several times without appreciable loss of catalytic activity. No evidence of the leaching of Pd from the catalyst during the course of reaction has been observed, suggesting true heterogeneity in our catalytic systems.
TL;DR: The gel material shows a highly selective visual response to a commonly used nitroexplosive, picric acid among a set of 19 congeners and the preferred selectivity has been mechanistically interpreted with density functional theory-based calculations.
Abstract: Thiourea (TU), a commercially available laboratory chemical, has been discovered to introduce metallogelation when reacted with copper(II) chloride in aqueous medium. The chemistry involves the reduction of Cu(II) to Cu(I) with concomitant oxidation of thiourea to dithiobisformamidinium dichloride. The gel formation is triggered through metal–ligand complexation, i.e., Cu(I)-TU coordination and extensive hydrogen bonding interactions involving thiourea, the disulfide product, water, and chloride ions. Entangled network morphology of the gel selectively develops in water, maybe for its superior hydrogen-bonding ability, as accounted from Kamlet–Taft solvent parameters. Complete and systematic chemical analyses demonstrate the importance of both Cu(I) and chloride ions as the key ingredients in the metal–organic coordination gel framework. The gel is highly fluorescent. Again, exclusive presence of Cu(I) metal centers in the gel structure makes the gel redox-responsive and therefore it shows reversible gel–...
TL;DR: In this paper, a triazine-functionalized porphyrin-based porous organic polymer, TPOP-1, was used for one-pot bottom-up synthesis involving extended aromatic electrophilic substitution on to a pyrrole.
Abstract: One-pot bottom-up synthesis involving extended aromatic electrophilic substitution on to a pyrrole has been employed for the design of a novel triazine-functionalized porphyrin-based porous organic polymer, TPOP-1. Hydrothermal treatment of 4,4′,4′′-(1,3,5-triazine-2,4,6-triyl)tris(oxy)tribenzaldehyde and pyrrole in glacial acetic acid in the presence of FeCl3 leads to the formation of TPOP-1, which is a highly porous and robust material, and which exhibits a high surface area and bimodal pore sizes ranging from large micropores to mesopores. The presence of porphyrin and triazine functionality within the network structure enables formation of electron-donating basic N-sites at the surface of the porous organic framework and thus favors the adsorption of Lewis acidic CO2 molecules and decoration of the material by palladium nanoparticles at its surface to form Pd-TPOP-1. TPOP-1 showed good CO2 storage capacity (6.2 mmol g−1 or 27.3 wt% at 3 bar/273 K), suggesting its potential application in environmental clean-up. Moreover, this post Pd-functionalized material forms fine colloidal suspensions in organic solvent and exhibits high catalytic activity for Sonogashira cross-coupling of aryl halides with aryl alkynes under mild reaction conditions.
TL;DR: A surprising effect of halide substituents on reduction potentials and catalytic activity of halogenated cobalt corroles has been deduced by experimental and computational methods as discussed by the authors.
TL;DR: Under comparable reaction conditions, LPSnP-1 gives 12 % more HMF yield than a small-pore mesoporous tin phosphate catalyst that has an identical framework composition, which confirms the beneficial role of large mesopores and nanoscale particle morphology in catalytic reactions that involve bulky natural carbohydrate molecules.
Abstract: A large-pore mesoporous tin phosphate (LPSnP-1) material has been synthesized hydrothermally by using Pluronic P123 as the structure-directing agent. The material is composed of aggregated nanoparticles of 10-15 nm in diameter and has a BET surface area of 216 m(2) g(-1) with an average pore diameter of 10.4 nm. This pore diameter is twice as large as that of mesoporous tin phosphate materials synthesized through the surfactant-templating pathways reported previously. LPSnP-1 shows excellent catalytic activity for the conversion of fructose, glucose, sucrose, cellobiose, and cellulose to 5-hydroxymethylfurfural (HMF) in a water/methyl isobutyl ketone biphasic solvent to give maximum yields of HMF of 77, 50, 51, 39, and 32 mol %, respectively, under microwave-assisted heating at 423 K. Under comparable reaction conditions, LPSnP-1 gives 12 % more HMF yield than a small-pore mesoporous tin phosphate catalyst that has an identical framework composition. This confirms the beneficial role of large mesopores and nanoscale particle morphology in catalytic reactions that involve bulky natural carbohydrate molecules.
TL;DR: A naphthalene diimide (NDI) building block containing hydrazide (H1) and hydroxy (H2) groups self-assembled into a reverse-vesicular structure in methylcyclohexane by orthogonal H-bonding and π-stacking by folding process due to the charge-transfer interaction between NDI and PY.
Abstract: A naphthalene diimide (NDI) building block containing hydrazide (H1) and hydroxy (H2) groups self-assembled into a reverse-vesicular structure in methylcyclohexane by orthogonal H-bonding and π-stacking. At an elevated temperature (LCST=43 °C), destruction of the assembled structure owing to selective dissociation of H2–H2 H bonding led to macroscopic precipitation. Further heating resulted in homogeneous redispersion of the sample at 70 °C (UCST) and the formation of a reverse-micellar structure. In the presence of a pyridine (H3)-functionalized pyrene (PY) donor, a supramolecular dyad (NDI–PY) was formed by H2–H3 H-bonding. Slow transformation into an alternate NDI–PY stack occurred by a folding process due to the charge-transfer interaction between NDI and PY. The mixed NDI–PY assembly exhibited a morphology transition from a reverse micelle (with a NDI–PY mixed-stack core) below the LCST to another reverse micelle (with a NDI core) above the UCST via a “denatured” intermediate.
TL;DR: The last twenty years have witnessed increasing research activity in the area of supramolecular chemistry of 1':'1 co-assembly of melamine (M) andcyanuric acid (CA), since the historic discovery of the M·CA aggregate in crystal form and its structural analysis by Wang and his coworkers.
Abstract: The last twenty years have witnessed increasing research activity in the area of supramolecular chemistry of 1 : 1 co-assembly of melamine (M)–cyanuric acid (CA), since the historic discovery of the M·CA aggregate in crystal form and its structural analysis by Wang and his coworkers in 1990. Its useful chemical structure and fascinating H-bonding interaction sites distinguish M and its analogous derivatives as scaffolding components in the field of supramolecular chemistry to develop desired nano-to-micro scaled architecture. To date, M-based supramolecular assemblies are known in diverse forms which include fascinating nano- to micromorphological structures, molecular guest boxes, small molecular gels, membrane, sensor and liquid crystal development, polymeric scaffolds etc. In this review, we have covered the development of M and its derivatives, encompassing both nano/micro-ordered structures and advanced functional materials.
TL;DR: In this article, the first attempt towards the synthesis of 4H-pyran-3-carboxylate was made using water as a reaction medium as well as a medium for synthesis of the catalyst.
TL;DR: In this article, a graphene based composite with silver nanoparticles has been synthesized via a simple chemical route and its catalytic activity has been tested for multi-component reactions and click reaction in a one-pot approach.
Abstract: A graphene based composite with silver nanoparticles has been synthesized via a simple chemical route and its catalytic activity has been tested for multi-component reactions and click reaction in a one-pot approach. This silver–graphene nanocomposite shows excellent catalytic activity at room temperature for three-component couplings between aldehydes, alkynes and amines (A3-coupling) and one-pot synthesis of 1,4-disubstituted 1,2,3-triazole via click reaction between in situ generated azides (derived from anilines or amines) and terminal acetylenes. This solid silver–graphene catalyst has been characterized by TEM, Raman, XRD and UV-Visible absorption spectra. The developed catalyst is air-stable, inexpensive, easy to prepare and can be facilely recovered and reused five times without significant decrease in activity and selectivity.
TL;DR: It is found that carbonization of vitamin B1 in the presence of phosphate salt at ∼90-130 °C for about 2 h produces highly fluorescent carbon nanoparticles of 1-6 nm size with a fluorescence quantum of up to 76%.
Abstract: A carbon-based fluorescent nanoparticle is considered to be a new generation nontoxic nanoprobe suitable for various bioimaging and sensing applications. However, the synthesis of such a high-quality nanoparticle is challenging, and its application potential is mostly unexplored. Here we report a vitamin B1 carbonization-based approach for blue and green fluorescent carbon nanoparticles of <10 nm size with a fluorescence quantum of up to 76%. We found that carbonization of vitamin B1 in the presence of phosphate salt at ∼90–130 °C for about 2 h produces highly fluorescent carbon nanoparticles of 1–6 nm size. The particle size and fluorescence property can be controlled by varying the reaction temperature and nature of phosphate salt. Elemental analysis shows the incorporation of a large percentage (up to 48 wt %) of other elements (such as nitrogen, oxygen, phophorus, and sulfur) in the carbon matrix. The chemical structure of vitamin B1 (thiamine) is unique in a sense that it consists of a large number o...