Showing papers by "Indian Association for the Cultivation of Science published in 2009"
TL;DR: Nitric acid oxidation induces nitrogen and oxygen incorporation into soot particles, which afforded water solubility and a light-emitting property; the isolation of small particles from a mixture of different sized particles improved the fluorescence quantum yield.
Abstract: Fluorescent carbon nanoparticles (CNPs) 2−6 nm in size with a quantum yield of about ∼3% were synthesized via nitric acid oxidation of carbon soot, and this approach can be used for milligram-scale synthesis of these water-soluble particles. These CNPs are nanocrystalline with a predominantly graphitic structure and show green fluorescence under UV exposure. Nitric acid oxidation induces nitrogen and oxygen incorporation into soot particles, which afforded water solubility and a light-emitting property; the isolation of small particles from a mixture of different sized particles improved the fluorescence quantum yield. These CNPs show encouraging cell-imaging applications. They enter into cells without any further functionalization, and the fluorescence property of these particles can be used for fluorescence-based cell imaging applications.
1,014 citations
TL;DR: Four Hh pathway antagonists that are epistatic to the nucleocytoplasmic regulator Suppressor of Fused are reported, including two that can inhibit Hh target gene expression induced by overexpression of the Gli transcription factors and reveal that Gli processing, Gli activation, and primary cilia formation are pharmacologically targetable.
Abstract: Inappropriate activation of the Hedgehog (Hh) signaling pathway has been implicated in a diverse spectrum of cancers, and its pharmacological blockade has emerged as an anti-tumor strategy. While nearly all known Hh pathway antagonists target the transmembrane protein Smoothened (Smo), small molecules that suppress downstream effectors could more comprehensively remediate Hh pathway-dependent tumors. We report here four Hh pathway antagonists that are epistatic to the nucleocytoplasmic regulator Suppressor of Fused [Su(fu)], including two that can inhibit Hh target gene expression induced by overexpression of the Gli transcription factors. Each inhibitor has a unique mechanism of action, and their phenotypes reveal that Gli processing, Gli activation, and primary cilia formation are pharmacologically targetable. We further establish the ability of certain compounds to block the proliferation of cerebellar granule neuron precursors expressing an oncogenic form of Smo, and we demonstrate that Hh pathway inhibitors can have tissue-specific activities. These antagonists therefore constitute a valuable set of chemical tools for interrogating downstream Hh signaling mechanisms and for developing chemotherapies against Hh pathway-related cancers.
298 citations
TL;DR: NGBC shows high antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria as well as the yeasts Saccharomyces cerevisiae and Candida albicans and these unique characteristics have been successfully utilized to obtain potable water free from pathogens and pesticides in a single operation.
Abstract: A green chemical method to synthesize nanogold-bioconjugate and its eco-friendly promising role to purify contaminated waters has been described. Gold nanoparticles of 10 nm average diameter are produced on the surface of Rhizopus oryzae, a fungal strain, by in situ reduction of chloroauric acid (HAuCl4). The nanogold-bioconjugate (NGBC) showed strong adsorption capacity toward different organophosphorous pesticides. The EDXA study confirms adsorption of pesticides on the conjugate material surface. Morphological changes of the NGBC material after adsorption of organophosphorous pesticides were detected by atomic force micrographs. NGBC shows high antimicrobial activity against several Gram-negative and Gram-positive pathogenic bacteria as well as the yeasts Saccharomyces cerevisiae and Candida albicans. The treatment of microbial cells with NGBC caused rupture of cell membrane as revealed in scanning electron and fluorescence micrographs. These unique characteristics of NGBC have been successfully utiliz...
275 citations
TL;DR: In this article, a new class of hydrogelators based on synthetic self-assembling N-terminally Boc-protected tripeptides has been developed, which can be potentially utilized for the treatment of waste-water and the organic dyes (Rhodamine B, Reactive Blue 4 and Direct Red 80) that are widely used in textile industries.
Abstract: A new class of hydrogelators based on synthetic self-assembling N-terminally Boc-protected tripeptides has been developed. A series of five tripeptides have been synthesized to study their self-assembling behavior in aqueous medium. Three of them form thermoreversible translucent gels at basic pH (pH 11.5–13.5). These hydrogels were characterized by FT-IR spectroscopy, circular dichroism (CD), small angle X-ray diffraction analysis (SAXRD), field-emission scanning electron microscopic (FE-SEM), transmission electron microscopic (TEM) and atomic force microscopic (AFM) studies. These hydrogels can be potentially utilized for the treatment of waste-water and the organic dyes (Rhodamine B, Reactive Blue 4 and Direct Red 80) that are widely used in textile industries can be efficiently removed. Moreover, peptide gelators can be recovered very easily just by changing the pH of the medium.
232 citations
TL;DR: Kinetic results suggest the intra-particle diffusion of dyes as rate limiting step in the adsorption process of JSP, which is in conformity with Freundlich and Langmuir isotherms for rhodamine B whereas congo red adsorptive removal fits well to LangmuIR isotherm only.
198 citations
TL;DR: In this paper, a mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol.
Abstract: A highly ordered 2D-hexagonal mesoporous silica material is functionalized with 3-aminopropyltriethoxysilane. This organically modified mesoporous material is grafted with a dialdehyde fluorescent chromophore, 4-methyl-2,6-diformyl phenol. Powder X-ray diffraction, transmission electron microscopy, N2 sorption, Fourier transform infrared spectroscopy, and UV-visible absorption and emission have been employed to characterize the material. This material shows excellent selective Zn2+ sensing, which is due to the fluorophore moiety present at its surface. Fluorescence measurements reveal that the emission intensity of the Zn2+-bound mesoporous material increases significantly upon addition of various concentrations of Zn2+, while the introduction of other biologically relevant (Ca2+, Mg2+, Na+, and K+) and environmentally hazardous transition-metal ions results in either unchanged or weakened intensity. The enhancement of fluorescence is attributed to the strong covalent binding of Zn2+, evident from the large binding constant value (0.87 × 104M−1). Thus, this functionalized mesoporous material grafted with the fluorescent chromophore could monitor or recognize Zn2+ from a mixture of ions that contains Zn2+ even in trace amounts and can be considered as a selective fluorescent probe. We have examined the application of this mesoporous zinc(II) sensor to cultured living cells (A375 human melanoma and human cervical cancer cell, HeLa) by fluorescence microscopy.
191 citations
TL;DR: A novel set of amphiphilic dipeptide-based carboxylic acids capable of efficiently gelating organic solvents with pH responsiveness was reported, which was aptly utilized for the pH-dependent phase-selective gelation of either solvent in a biphasic mixture of oil and water.
Abstract: The search for efficient low-molecular-weight gelators (LMWGs) with possible structure−activity correlation is on the rise The present work reports a novel set of amphiphilic dipeptide-based carboxylic acids capable of efficiently gelating organic solvents More interestingly, their sodium salts showed enhanced efficiency in organogelation with the additional ability to gelate water Electrostatic interactions present in the aggregation of the sodium carboxylates of amphiphilic dipeptides seem to be important because some of the nongelator carboxylic acids turned out to be excellent gelators upon salt formation The combinations and sequence of the amino acids in the dipeptide moiety were systematically altered to understand the collective importance of the nonpolar aliphatic/aromatic substitution in amino acids in the self-assembling behavior of amphiphiles Almost a 20-fold enhancement in the gelation ability was observed on reversing the sequence of the amino acid residues, and in some cases, nongelat
167 citations
TL;DR: Two synthetic oligopeptide-based, thermoreversible, pH-sensitive hydrogels have been utilized for entrapment and slow release of an anticancer drug doxorubicin at physiological pH, promising their future application as a drug delivery vehicle.
Abstract: Here, we report two synthetic oligopeptide-based, thermoreversible, pH-sensitive hydrogels In gel phase, these self-assembling tetrapeptides form a long interconnected nanofibrilar network structure, as is evident from various microscopic techniques, including field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) FTIR, circular dichroism, and wide angle X-ray diffraction (WAXD) favor an antiparallel beta-sheet structure of these gelators in the gel state Finally, these hydrogels have been utilized for entrapment and slow release of an anticancer drug doxorubicin at physiological pH, promising their future application as a drug delivery vehicle
159 citations
TL;DR: In this article, the effect of different solvents on the crystal structures, morphologies, and sizes of Co doped 1D nanostructures was investigated using steady state photoluminescence (P...
Abstract: One dimensional (1D) anatase Co doped TiO2 nanostructures such as nanorods, nanowires, and nanotubes were synthesized by a simple solvothermal method using CoCl2·6H2O as the cobalt source. The effect of the different solvents on the crystal structures, morphologies, and sizes of the Co doped 1D nanostructures was investigated. The doping concentration of the samples primarily depends on the solvents. The X-ray photoelectron spectroscopy studies clearly showed that the Co was incorporated into the TiO2 lattice as Co2+ and oxygen vacancies were created due to the substitution of the Ti4+ ions by Co2+ ions. Optical absorption measurements showed additional absorption bands that are due to the ligand field transitions, 4T1g(4F) → 4T1g(4P) of Co2+ and also due to the transitions from different trap states related to the oxygen vacancies. The effects of the doping concentration on the defect structures and oxygen vacancies of the 1D nanostructures were mainly investigated using steady state photoluminescence (P...
152 citations
TL;DR: In this paper, the ground-state properties of the Ni-Mn-based shape-memory alloys have been studied by dc magnetization and ac susceptibility measurements, and a reentrant spin glass with both ferromagnetic and glassy phases coexisting together at low temperature at least in the field-cooled state.
Abstract: The ground-state properties of the ferromagnetic shape-memory alloy of nominal composition ${\text{Ni}}_{2}{\text{Mn}}_{1.36}{\text{Sn}}_{0.64}$ have been studied by dc magnetization and ac susceptibility measurements. Like few other Ni-Mn based alloys, this sample exhibits exchange bias phenomenon. The observed exchange pinning was found to originate right from the temperature where a steplike anomaly is present in the zero-field-cooled magnetization data. The ac susceptibility study indicates the onset of spin-glass freezing near this steplike anomaly with clear frequency shift. The sample can be identified as a reentrant spin glass with both ferromagnetic and glassy phases coexisting together at low temperature at least in the field-cooled state. The result provides us with a comprehensive view to identify the magnetic character of various Ni-Mn-based shape-memory alloys with competing magnetic interactions.
141 citations
TL;DR: It is revealed that a very high degree of short range order is preserved even in samples with highly reduced long range chemical order.
Abstract: The degree of B/B alternate cation order is known to heavily influence the magnetic properties of A2BB O6 double perovskites although the nature of such disorder has never been critically studied. Our detailed x-ray absorption fine structure studies in conjunction with synchrotron radiation x-ray diffraction experiments on polycrystalline Sr2FeMoO6 samples with various degrees of disorder reveal that a very high degree of short range order is preserved even in samples with highly reduced long range chemical order. Based on these experimental results and with the help of detailed structural simulations, we are able to model the nature of the disorder in this important class of materials and discuss the consequent implications on its physical properties.
TL;DR: In this paper, a reduction of Pd(II) with a Fischer carbene complex where polyethylene glycol (PEG) was used as stabilizer is presented.
TL;DR: The binding and selectivity of halides and oxyanions toward a recently reported pentafluorophenyl-substituted tripodal urea-based receptor L(1) are examined thoroughly in the solid state by single-crystal X-ray crystallography as well as in solution by multinuclear NMR techniques.
Abstract: The binding and selectivity of halides (spherical) and oxyanions (tetrahedral) toward a recently reported pentafluorophenyl-substituted tripodal urea-based receptor L(1) are examined thoroughly in the solid state by single-crystal X-ray crystallography as well as in solution by multinuclear NMR techniques. Crystallographic results show proof of a fluoride encapsulation in the cavity of L(1) in complex [L(1)(F)][Bu(4)N], . Fluoride encapsulation inside the C(3v) symmetric cleft is observed via six hydrogen bonds to all six urea protons of the receptor. In case of complex crystallographic results show encapsulation of sulfate ion inside a supramolecular cage formed upon 1 : 2 (guest-host) complex formation between sulfate and L(1). Sulfate encapsulation is observed via fourteen hydrogen bonding interactions from all six urea moieties of two L(1) units. Our effort to isolate single crystal of halides/oxyanions complexes of L(2) always yield single crystals of free L(2) though literature shows anion binding with this receptor in solution. Solution state binding studies of L(1) are carried out by (1)H-NMR titration to calculate binding constants, which show the following anion binding sequence H(2)PO(4)(-) > SO(4)(2-)> CH(3)COO(-) > F(-) > Cl(-) >> Br(-) whereas there is no binding with I(-), NO(3)(-) and ClO(4)(-) guests. Comparison of phosphate and sulfate binding in L(1) and L(2), show higher binding with the pentafluorophenyl substituted receptor, L(1). Further (19)F and (31)P-NMR experiments in solution are also carried out to probe the binding of F(-) and H(2)PO(4)(-) with L(1), respectively. Extensive (1)H-NMR experiments in solution and crystallization in the presence of multiple anions are also undertaken to evaluate the selectivity of H(2)PO(4)(-) over other anions.
TL;DR: In this paper, a surface functionalized method has been employed to synthesize TiO2@CdS core−shell nanorods using citric acid as a surface-functionalized agent.
Abstract: The well-known surface-functionalized method has been employed to synthesize TiO2@CdS core−shell nanorods using citric acid as a surface-functionalized agent. By varying the concentration of the citric acid, core−shell nanorods of core diameter 36 nm with different shell thickness (19−34 nm) were formed. The UV−visible absorption spectra of the core−shell nanorods show a red shift of the band edge of uncoated TiO2, and the broadening of the absorption spectra is also observed with shell growth. Steady-state photoluminescence (PL) spectra of the core−shell nanorods give a new emission in the visible region and also red shift with the increasing shell thickness. Decay kinetics indicate that the average lifetime ⟨τ⟩ of the core−shell nanorods is larger than that of the uncoated TiO2, and it varies from nanoseconds to picoseconds. The current−voltage (I−V) curves of the core−shell nanorods give a photocurrent density that is 212 times greater than the dark current density.
TL;DR: A novel concept of microRNA (miRNA)–mediated host–virus interactions in bronchoalveolar stem cells (BASCs) at the onset of infection is focused on by correlating the “BASC–microRNome” with their targets within BASCs and viral genome.
Abstract: Severe acute respiratory syndrome (SARS), caused by the coronavirus SARS-CoV, is an acute infectious disease with significant mortality. A typical clinical feature associated with SARS is pulmonary fibrosis and associated lung failure. In the aftermath of the SARS epidemic, although significant progress towards understanding the underlying molecular mechanism of the infection has been made, a large gap still remains in our knowledge regarding how SARS-CoV interacts with the host cell at the onset of infection. The rapidly changing viral genome adds another variable to this equation. We have focused on a novel concept of microRNA (miRNA)–mediated host–virus interactions in bronchoalveolar stem cells (BASCs) at the onset of infection by correlating the “BASC–microRNome” with their targets within BASCs and viral genome. This work encompasses miRNA array data analysis, target prediction, and miRNA–mRNA enrichment analysis and develops a complex interaction map among disease-related factors, miRNAs, and BASCs in SARS pathway, which will provide some clues for diagnostic markers to view an overall interplay leading to disease progression. Our observation reveals the BASCs (Sca-1+ CD34+ CD45- Pecam-), a subset of Oct-4+ ACE2+ epithelial colony cells at the broncho-alveolar duct junction, to be the prime target cells of SARS-CoV infection. Upregulated BASC miRNAs-17*, -574-5p, and -214 are co-opted by SARS-CoV to suppress its own replication and evade immune elimination until successful transmission takes place. Viral Nucleocapsid and Spike protein targets seem to co-opt downregulated miR-223 and miR-98 respectively within BASCs to control the various stages of BASC differentiation, activation of inflammatory chemokines, and downregulation of ACE2. All these effectively accounts for a successful viral transmission and replication within BASCs causing continued deterioration of lung tissues and apparent loss of capacity for lung repair. Overall, this investigation reveals another mode of exploitation of cellular miRNA machinery by virus to their own advantage.
TL;DR: In this report, steady state and time-resolved fluorescence along with circular dichroism (CD) spectroscopic, FTIR, and anisotropy investigations were made to reveal the nature of the interactions between human adult hemoglobin (Hb) and the isatins, 1-methylisatin (1-MI) and 1-phenylisatin(1-PI).
Abstract: In this report, steady state and time-resolved fluorescence along with circular dichroism (CD) spectroscopic, FTIR, and anisotropy investigations were made to reveal the nature of the interactions between human adult hemoglobin (Hb) and the isatins, 1-methylisatin (1-MI) and 1-phenylisatin (1-PI). From the analysis of the steady state and time-resolved fluorescence quenching of Hb in aqueous solution in the presence of an isatin, i.e., 1-MI, it seemed that the nature of the quenching was of static type and a mixture of both static and dynamic nature for 1-PI. The primary binding pattern between isatins and Hb has been interpreted as a combined effect of hydrophobic association and electrostatic interaction for 1-MI. For 1-PI, this was the combined effect of hydrophobic association and ionic interactions and salt bridges or/and proton transfer. The pretwisted structure of 1-PI facilitates ionic interactions with Hb. The binding constants, number of binding sites, and thermodynamic parameters had been compu...
TL;DR: In this paper, the authors reported the preparation of pure and Eu3+-doped SnO2 nanocrystals by microwave synthesis and calculated the calculated quantum efficiencies are 22.0, 31.0%, and 26.0% for 300, 400, and 800 °C heated samples, respectively.
Abstract: Here, we report the preparation of pure and Eu3+-doped SnO2 nanocrystals by microwave synthesis. The size dependence of the band gap energies of the quantum-confined SnO2 particles agrees very well with the confinement regime. The PL intensity, decay time, and quantum efficiency are found to be sensitive to the particle size. The calculated quantum efficiencies are 22.0%, 31.0%, and 26.0% for 300, 400, and 800 °C heated samples, respectively, because minimum nonradiative decay rate is observed at 400 °C heated sample. Analysis suggests that the crystallite size plays an important role in tuning the quantum efficiency, emission intensity, and decay time of Eu3+-doped SnO2 nanocrystals. Results show that the conductivity for doped sample is higher than that for pure SnO2 nanocrystals and pure SnO2 nanocrystals showed a typical rectifying behavior.
TL;DR: In this paper, a simple and efficient procedure for Suzuki coupling of aryl bromides/iodides with alkyl and boronic acids catalyzed by in situ generated palladium(0) nanoparticles in water without any ligand in open air to produce a variety of functionalized biaryls and alkyls has been developed.
TL;DR: An arene based tripodal amide receptor shows selective dimeric capsule formation templated by fluoride-water cluster, [F2(H2O)(6)]2-, and non-capsular aggregation for chloride, nitrate and acetate anions.
TL;DR: In this article, a simple and efficient procedure for the synthesis of 2-substituted benzimidazoles has been developed by a one-pot reaction of o-phenylenediamine with aromatic aldehydes in the presence of an ionic liquid, 1-methyl-3-pentylimidazolium tetrafluoroborate, [pmim]BF4 at room temperature in open air without any organic solvent.
TL;DR: The photoluminescence spectrum shows an enhanced ultraviolet emission and a reduced defect-related emission in the capped ZnO NWs compared to bare ZnL, as evidenced from the FESEM, HRTEM, and FTIR results.
Abstract: The effect of surface capping with poly(vinyl alcohol) (PVA) on the photocarrier relaxation of the aqueous chemically grown ZnO nanowires (NWs) has been investigated. The decay in the photocurrent during steady ultraviolet illumination due to the photocarrier relaxation has been reduced in the capped NWs, as evidenced from a decrease in the photocurrent only by 12% of its maximum value under steady illumination for 15 min and a decrease in the photocurrent by 49% of its maximum value during the same interval of time in the as-grown NWs. The surface modification is confirmed from the FESEM, HRTEM, and FTIR results. The photoluminescence spectrum shows an enhanced ultraviolet emission and a reduced defect-related emission in the capped ZnO NWs compared to bare ZnO.
TL;DR: In this paper, the synthesis of pure and rare-earth ions doped Ga2O3 nanoparticles for blue (Ga2O), green (Tb3+) and red (Eu3+) emission was reported.
TL;DR: In this article, a new (μ-chloro)-bridged complex [Cu(HL)Cl]2·H2O (1) with the Schiff base ligand H2L, [2-((E)-(2-hydroxyethylimino)methyl)-4-bromophenol], has been synthesized and characterized by elemental analysis, IR, UV-Vis and EPR spectroscopic studies.
TL;DR: This finding suggests that the optoelectronic properties of CdS nanoparticles can be tuned upon deposition on gel nanofibers without changing the size of the nanoparticles.
Abstract: The pH-induced self-assembly of three synthetic tripeptides in water medium is used to immobilize luminescent CdS nanoparticles. These peptides form a nanofibrillar network structure upon gelation in aqueous medium at basic pH values (pH 11.0-13.0), and the fabrication of CdS nanoparticles on the gel nanofiber confers the luminescent property to these gels. Atomic force microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy clearly reveal the presence of CdS nanoparticles in a well-defined array on the gel nanofibers. This is a convenient way to make organic nanofiber-inorganic nanoparticle hybrid nanocomposite systems. The size of the CdS nanoparticles remains almost same before and after deposition on the gel nanofiber. Photoluminescence (PL) measurement of the CdS nanoparticles upon deposition on the gel nanofibers shows a significant blue shift in the emission spectrum of the nanoparticles, and there is a considerable change in the PL gap energy of the CdS nanoparticles after immobilization on different gel nanofibrils. This finding suggests that the optoelectronic properties of CdS nanoparticles can be tuned upon deposition on gel nanofibers without changing the size of the nanoparticles.
TL;DR: In this article, the grafting of N,N-dimethylaminoethyl methacrylate (DMAEMA) directly from poly(vinylidene fluoride) (PVDF) backbone in solution phase by atom transfer radical polymerization (ATRP) was reported.
Abstract: Here we report the grafting of N,N-dimethylaminoethyl methacrylate (DMAEMA) directly from poly(vinylidene fluoride) (PVDF) backbone in solution phase by atom transfer radical polymerization (ATRP). The graft length is same for different times of polymerization but graft density increases with increasing polymerization time. Four graft copolymers are prepared and depending on the time of conversion they are designated as PD-6, PD-12, PD-18, and PD-24, the number indicates time (h) of polymerization. A maximum of 36% (w/w) conversion with respect to monomer is achieved in the PD-24 sample. Gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and polymerization kinetics study conclude the ATRP nature of the polymerization. The graft copolymer shows induced solubility in water and the effective particle diameter in aqueous medium decreases from PD-6 to PD-24 samples. The enthalpy of fusion values are same in graft copolymers with more than 50% reduction and the melting points reduce by 5−6 °...
TL;DR: A simple route for the synthesis of a novel mesoporous zinc oxide material having wurtzite like nanocrystalline pore walls by using Schiff-base amine as template is reported, which shows very high BET surface area and remarkably enhanced photoconductivity and photoluminescence at room temperature under visible light irradiation vis-à-vis bulk ZnO material.
TL;DR: In this article, a mixture of nanocrystalline CuO and Pd(OAc) was used for Suzuki coupling and cyanation reaction in polyethylene glycol (PEG-6000).
TL;DR: In this article, single phase nanocrystalline YFeO3 has been synthesized by a simple solution method and the average particle diameter is 42.2mm and the magnetization versus temperature over the temperature range 2-300k obeys Bloch equation with a Bloch constant value 9.98×10−6−K−3/2.
TL;DR: In order to enhance the ionic conductivity of polyethylene oxide (PEO) based alkaline polymer electrolytes, nanosized inorganic filler ZnS has been incorporated into PEO-KI matrix and corresponding nanocomposite polymer electrolyte is synthesized by the usual solution casting procedure.