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Showing papers by "Indian Association for the Cultivation of Science published in 2012"


Journal ArticleDOI
TL;DR: Highly porous N-doped activated carbon monoliths (ACMs) are fabricated by carbonization and physical activation of mesoporous polyacrylonitrile (PAN) monolithics in the presence of CO(2).

249 citations


Journal ArticleDOI
TL;DR: In this article, a core/shell nanorod arrays of ZnO/CdS with varying shell thickness and their shell thickness dependent photocatalytic properties have been investigated.
Abstract: Core/shell nanorod arrays of ZnO/CdS have been synthesized with varying shell thickness and their shell thickness dependent photocatalytic properties have been investigated. Core/shell nanorod arrays of core diameter of 100 nm with variable shell thickness (10–30 nm) are synthesized by varying the concentration of the citric acid. XRD analysis reveals that tensile strain is obtained for ZnO nanorods and the compressive strain is obtained for core/shell nanorods. The UV–visible absorption spectra of the core/shell nanorod arrays show a red shift of the band edge of uncoated ZnO with shell growth. Steady-state photoluminescence (PL) spectra of the core/shell nanorod arrays show red shift of emission band with the increase in shell thickness. Decay kinetics indicate that the average lifetime (⟨τ⟩) of the core/shell nanorod arrays is larger than that of the uncoated ZnO nanorods due to charge separation. I–V studies show a 16-fold enhancement in current using the ZnO/CdS core/shell nanorod arrays having CdS s...

240 citations


Journal ArticleDOI
TL;DR: Iron containing porous organic polymers have been synthesized by a facile one-pot bottom-up approach to porphyrin chemistry by an extended aromatic substitution reaction between pyrrole and aromatic dialdehydes in the presence of small amount of Fe(III).

232 citations


Journal ArticleDOI
TL;DR: The catalytic activity of the robust, safe and magnetically recoverable Fe(3)O(4)@mesoporous SBA-15 nanocatalyst was evaluated in the Biginelli reaction under mild conditions for the synthesis of a diverse range of 3,4-dihydropyrimidin-2(1H)-ones.
Abstract: A magnetic nanoparticle conjugated mesoporous nanocatalyst (Fe(3)O(4)@mesoporous SBA-15) with a high surface area has been synthesized by chemical conjugation of magnetite (Fe(3)O(4)) nanoparticles with functionalized mesoporous SBA-15. Functionalized mesoporous SBA-15 containing surface carboxyl and amino groups was synthesized via the thiol-ene click reaction of cysteine hydrochloride and vinyl functionalized SBA-15. The catalytic activity of the robust, safe and magnetically recoverable Fe(3)O(4)@mesoporous SBA-15 nanocatalyst was evaluated in the Biginelli reaction under mild conditions for the synthesis of a diverse range of 3,4-dihydropyrimidin-2(1H)-ones. The separation and reuse of the Fe(3)O(4)@mesoporous SBA-15 nanocatalyst were simple, effective and economical.

226 citations


Journal ArticleDOI
TL;DR: An aromatic amino acid (phenylglycine) based amphiphile with amide and ester groups and a long fatty acyl chain has been found to form organogels selectively in the fuel hydrocarbon solvents including hexane, heptane, cyclohexane, diesel, kerosene and pump-oil at room temperature.
Abstract: An aromatic amino acid (phenylglycine) based amphiphile with amide and ester groups and a long fatty acyl chain has been found to form organogels selectively in the fuel hydrocarbon solvents including hexane, heptane, cyclohexane, diesel, kerosene and pump-oil at room temperature. Organogels have been well characterized morphologically by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). Morphological studies of these xerogels have revealed the presence of fascinating right-handed twisted nanoribbons (in n-heptane and n-octane). Involvement of different non-covalent interactions among the gelator molecules within the gel matrix has been studied using FT-IR and XRD. The organogel in diesel is mechanically stable with high yield stress (177.8 Pa) and storage modulus (>104 Pa) values, as has been evidenced from the rheological studies. Interestingly, this gelator compound exhibits phase selective gelation properties and the phase selective gelation occurs efficiently and quickly (within 90 s), in oil–water mixtures and the gelator molecule can be recovered and reused several times easily, indicating its applicability in oil spill cleaning.

211 citations


Journal ArticleDOI
30 Jul 2012-Analyst
TL;DR: An efficient water soluble fluorescent Al(3+) receptor, 1-[[(2-furanylmethyl)imino]methyl]-2-naphthol (1-H) was synthesized and characterized by physico-chemical and spectroscopic tools along with single crystal X-ray crystallography to be suitable for detection of intracellular Al( 3+) by fluorescence microscopy.
Abstract: An efficient water soluble fluorescent Al3+ receptor, 1-[[(2-furanylmethyl)imino]methyl]-2-naphthol (1-H) was synthesized and characterized by physico-chemical and spectroscopic tools along with single crystal X-ray crystallography. High selectivity and affinity of 1-H towards Al3+ in HEPES buffer (DMSO/water: 1/100) of pH 7.4 at 25 °C showed it to be suitable for detection of intracellular Al3+ by fluorescence microscopy. Metal ions, viz. alkali (Na+, K+), alkaline earth (Mg2+, Ca2+), and transition-metal ions (Ni2+, Zn2+, Cd2+, Co2+, Cu2+, Fe3+, Cr3+/6+, Hg2+) and Pb2+, Ag+ did not interfere. The lowest detection limit for Al3+ was calculated to be 6.03 × 10−7 M in 100 mM HEPES buffer (DMSO/water: 1/100). Theoretical calculations have also been included in support of the configuration of the probe–aluminium complex.

198 citations


Journal ArticleDOI
TL;DR: In this paper, photoexcited GQDs and ZnO nanowires were used to demonstrate their potential as a solar harvesting material in photovoltaic cells exhibiting an open circuit voltage of 0.8 V.
Abstract: Graphene quantum dots (GQDs) synthesized by a direct chemical method have been used in combination with ZnO nanowires (NWs) to demonstrate their potential as a solar harvesting material in photovoltaic cells exhibiting an open circuit voltage of 0.8 V. The excited state interaction between the photoexcited GQDs and the ZnO NWs has been verified from the charge-transfer process by both emission spectroscopy and photovoltaic measurements. This work has implications for less expensive and efficient next generation solid-state solar cells.

195 citations


Journal ArticleDOI
TL;DR: This tutorial review aims at highlighting some of the developments of such structurally diverse and functionally intriguing CPs derived from N-donor ditopic ligands having a non-innocent backbone.
Abstract: The last two decades have witnessed the research activities in the area of coordination polymers (CPs), which are structurally diverse and functionally intriguing materials. In this endeavor, the most exploited ligand has been a structurally rigid N-donor compound having an innocent backbone (incapable of forming hydrogen bond) namely 4,4′-bipyridine. Much has been achieved by exploiting this wonder ligand in the area of CPs. However, the positional isomers such as 3,3′-bipyridine or 4,3′-bipyridine (which understandably induce diverse ligating topology as compared to their more symmetrical 4,4′ counterpart) were not exploited in much detail presumably because of the difficulty in their synthetic accessibility. To get access to such N-donor ditopic ligands having diverse ligating topology, much efforts have been focused in the last decade or so to design such positional isomers of 4,4′-bipyridine having a non-innocent backbone (capable of forming hydrogen bond). The principal focus of such studies is to decipher the effect of diverse ligating topology and the non-innocent backbone of the ligands on the overall supramolecular structures and functions of the resultant CPs. This tutorial review aims at highlighting some of the developments of such structurally diverse and functionally intriguing CPs derived from N-donor ditopic ligands having a non-innocent backbone.

189 citations


Journal ArticleDOI
TL;DR: In this article, the buckling distortions in the individual six membered rings of silicene have been investigated and it has been shown that the stabilization of puckering σ-backbone overwhelms the π-backbones destabilization.
Abstract: Silicene, the all Si analogue of graphene is structurally different due to the presence of buckling distortions in the individual six membered rings. The sufficiently strong coupling between the unoccupied molecular orbitals (UMOs) with occupied molecular orbitals (OMOs) leads to pseudo-Jahn–Teller distortion (PJT) and the characteristic buckling in silicenes. σ–π separation analyses reveal that the σ-backbone gets stabilized, whereas the π-backbone is destabilized due to buckling. However, the stabilization of puckering σ-backbone overwhelms the π-backbone destabilization. This is exactly opposite to that of graphene. The cations like Li+ can suppress the PJT distortions resulting in a planar structure. This leads to opening of band gap (∼1.62 eV). Si substituted benzenes binds more strongly with Li+ than benzene. The mutual competition/synergy between the orbital interactions of the ring with the cation and the π-charge density across the surface of molecule governs the stability of these complexes.

185 citations


Journal ArticleDOI
TL;DR: In this article, the momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte Carlo techniques.
Abstract: The momentum diffusion coefficient for heavy quarks is studied in a deconfined gluon plasma in the static approximation by investigating a correlation function of the color electric field using Monte Carlo techniques. The diffusion coefficient is extracted from the long-distance behavior of such a correlator. For temperatures ${T}_{c}lT\ensuremath{\lesssim}2{T}_{c}$, our nonperturbative estimate of the diffusion coefficient is found to be very different from the leading-order perturbation theory and is in the right ballpark to explain the heavy quark flow seen by the PHENIX Collaboration at the RHIC experiment.

174 citations


Journal ArticleDOI
TL;DR: This tutorial review focuses on some recent aspects in the development of synthetic receptors for selective sulfate anion recognition and separation, with a special emphasis to receptor for selective recognition of sulfate in organic and aqueous media.
Abstract: This tutorial review focuses on some recent aspects in the development of synthetic receptors for selective sulfate anion recognition and separation, with a special emphasis to: (i) receptors for selective recognition of sulfate in organic and aqueous media and (ii) receptors for separation of sulfate from water via liquid–liquid extraction and crystallization.

Journal ArticleDOI
TL;DR: In this study, stable supramolecular hydrogels have been obtained from the assembly of graphene oxide (GO) in presence of polyamines including tris(aminoethyl)amine, spermine, and spermidine and the presence of a network structure of cross-linked nanosheets suggests the supramolescular assembly of GO in the presenceof polyamines using the acid-base type electrostatic interaction.
Abstract: In this study, stable supramolecular hydrogels have been obtained from the assembly of graphene oxide (GO) in presence of polyamines including tris(aminoethyl)amine, spermine, and spermidine [biologically active molecule]. One of these hydrogels has been well characterized by various techniques including field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD) study, and Raman spectroscopy. TEM and AFM studies of one of these hydrogels have revealed the presence of a network structure of cross-linked nanosheets. This suggests the supramolecular assembly of GO in the presence of polyamines using the acid-base type electrostatic interaction. In presence of a mild reducing agent (vitamin C), one of these GO hydrogels has been transformed into a reduced graphene oxide (RGO)-based hydrogel by a simple in situ reduction of GO sheets within the hydrogel matrix. Moreover, noble metal nanoparticle containing RGO based hybrid hydrogels have been obtained using in situ and simultaneous co-reduction of GO and noble metal precursors within the GO gel matrix. The elegance of this method is in situ, "green chemical" and simultaneous reduction of GO and metal salts within the hydrogel matrix to form RGO-based hybrid gel and concomitant stabilization of metal nanoparticles (MNPs) within the gel system. The nascently formed MNPs are homogeneously and uniformly distributed on the surface of the RGO nanosheets within the hybrid gel. Interestingly, this MNP containing RGO-based hybrid hydrogel matrix acts as a potential catalyst for the reduction of aromatic nitro to amino group. The catalyst (hybrid gel matrix) can be separated easily after the reaction and reused several times.

Journal ArticleDOI
TL;DR: This review highlights the general features of nanoparticles as catalysts with particular reference to copper and the recent developments in the copper(0) nanoparticle-catalyzed C( Daryl)-C(aryl/alkynyl), C(aryl)-N, C-aryl)-O, C (aryl)-S, and C- Daryl)-Se bond formations and related reactions.
Abstract: The carbon-carbon and carbon-heteroatom bond formations constitute the backbone of organic synthesis and have been widely used in the synthesis of natural products and useful compounds. Because of growing environmental concern, more attention has been focussed on the development of greener methods. Copper is environment-friendly and comparatively inexpensive. Although the use of copper salts in catalysis has been known since the last century, this area of research has been less explored compared to other metals, such as palladium, magnesium, and zinc. This review highlights the general features of nanoparticles as catalysts with particular reference to copper and the recent developments in the copper(0) nanoparticle-catalyzed C(aryl)-C(aryl/alkynyl), C(aryl)-N, C(aryl)-O, C(aryl)-S, and C(aryl)-Se bond formations and related reactions. The mechanisms of the reactions have been outlined and discussed with respect to the active catalytic species and possible intermediates. The scope, limitations, and green aspects of the reactions have also been highlighted. The convenient methods of preparation of copper nanoparticles and their characterization are described.

Journal ArticleDOI
18 Jun 2012-Analyst
TL;DR: A newly designed probe, 6-thiophen-2-yl-5,6-dihydrobenzo[4,5]imidazo-[1,2-c] quinazoline (HL(1)), behaves as a highly selective ratiometric fluorescent sensor for Fe(2+) at pH 4.0-5.0 and Fe(3+) in vitro by developing a good image of the biological organelles.
Abstract: A newly designed probe, 6-thiophen-2-yl-5,6-dihydrobenzo[4,5]imidazo-[1,2-c] quinazoline (HL1) behaves as a highly selective ratiometric fluorescent sensor for Fe2+ at pH 4.0–5.0 and Fe3+ at pH 6.5–8.0 in acetonitrile–HEPES buffer (1/4) (v/v) medium. A decrease in fluorescence at 412 nm and increase in fluorescence at 472 nm with an isoemissive point at 436 nm with the addition of Fe2+ salt solution is due to the formation of mononuclear Fe2+ complex [FeII(HL)(ClO4)2(CH3CN)2] (1) in acetonitrile–HEPES buffer (100 mM, 1/4, v/v) at pH 4.5 and a decrease in fluorescence at 412 nm and increase in fluorescence at 482 nm with an isoemissive point at 445 nm during titration by Fe3+ salt due to the formation of binary Fe3+ complex, [FeIII(L)2(ClO4)(H2O)] (2) with co-solvent at biological pH 7.4 have been established. Binding constants (Ka) in the solution state were calculated to be 3.88 × 105 M−1 for Fe2+ and 0.21 × 103 M−1/2 for Fe3+ and ratiometric detection limits for Fe2+ and Fe3+ were found to be 2.0 μM and 3.5 μM, respectively. The probe is a “naked eye” chemosensor for two states of iron. Theoretical calculations were studied to establish the configurations of probe–iron complexes. The sensor is efficient for detecting Fe3+in vitro by developing a good image of the biological organelles.

Journal ArticleDOI
TL;DR: A combination of experimental and computational approaches shows that incomplete centrosome separation at NEB decreases the accuracy of chromosome segregation and thus represents a severe threat to genome stability.
Abstract: Spindle assembly, establishment of kinetochore attachment, and sister chromatid separation must occur during mitosis in a highly coordinated fashion to ensure accurate chromosome segregation. In most vertebrate cells, the nuclear envelope must break down to allow interaction between microtubules of the mitotic spindle and the kinetochores. It was previously shown that nuclear envelope breakdown (NEB) is not coordinated with centrosome separation and that centrosome separation can be either complete at the time of NEB or can be completed after NEB. In this study, we investigated whether the timing of centrosome separation affects subsequent mitotic events such as establishment of kinetochore attachment or chromosome segregation. We used a combination of experimental and computational approaches to investigate kinetochore attachment and chromosome segregation in cells with complete versus incomplete spindle pole separation at NEB. We found that cells with incomplete spindle pole separation exhibit higher rates of kinetochore misattachments and chromosome missegregation than cells that complete centrosome separation before NEB. Moreover, our mathematical model showed that two spindle poles in close proximity do not “search” the entire cellular space, leading to formation of large numbers of syntelic attachments, which can be an intermediate stage in the formation of merotelic kinetochores.

Journal ArticleDOI
TL;DR: In this article, the modulus data have been fitted using non-exponential Kohlrausch-Williams-Watts (KWW) function φ(t), and the value of the nonexponential parameter (β) is fairly low and nearly constant for different salt concentrations.

Journal ArticleDOI
TL;DR: The race to develop newer materials with superior properties/applications in diversified fields is gathering momentum in modern day science as mentioned in this paper and an exciting avenue of research deals with the development of hybrid materials resulting from the combination of gels with nanoparticles of different origins.
Abstract: The race to develop newer materials with superior properties/applications in diversified fields is gathering momentum in modern day science. In this context, an exciting avenue of research deals with the development of hybrid materials resulting from the combination of gels with nanoparticles of different origins. These varying kinds of nanoparticles (inorganic nanoparticles, Au/Ag based nanoparticles and carbonaceous nanostructures like carbon nanotube and graphene) are being used in conjunction with diverse self-assemblies to develop gel-nanocomposites with the scope of generating advanced applications. The present review will track the noteworthy progress of gel-nanocomposites and also will highlight the recent advances in their synthesis, improved properties/features and applications for developing mechanically robust materials to antimicrobial hydrogels.

Journal ArticleDOI
TL;DR: In this article, the stability and physical properties of single-layer BN sheet chemically functionalized by various groups, viz. H, F, OH, CH, CHO, CN, NH, etc., were investigated.
Abstract: From first principles calculations, we investigate the stability and physical properties of single-layer $h$-BN sheet chemically functionalized by various groups, viz. H, F, OH, CH${}_{3}$, CHO, CN, NH${}_{2}$, etc. We find that full functionalization of $h$-BN sheet with these groups leads to decrease in its electronic band gap, albeit to different magnitudes varying from 0.3 eV to 3.1 eV, depending upon the dopant group. Functionalization by a CHO group in particular leads to a sharp decrease in the electronic band gap of the pristine BN sheet to \ensuremath{\sim}0.3 eV, which is congenial for its usage in transistor-based devices. For the optimized structure of the sheet, the calculated phonon frequencies corresponding to all the vibrational modes turn out to be real (positive), thereby suggesting their inherent stability. The chemisorption energies of these groups with the B and N atoms of the sheet are found to lie in the range of 1.5--6 eV. The optical absorption and conductivity of these functionalized sheets under polarized light are found to be much higher than that of the native BN sheet.

Journal ArticleDOI
TL;DR: Highly selective reduction of nitroarenes has been achieved using iron metal nanoparticles in water at room temperature with a wide spectrum of reducible functionalities remained inert under the reaction conditions.

Journal ArticleDOI
TL;DR: Efficient synthesis strategy, exceptionally high surface area and high adsorption efficiency of these mesoporous γ-Al(2)O(3) materials for the dissolved arsenic from the contaminated aqueous solutions could find potential utility in the purification of polluted water.

Journal ArticleDOI
TL;DR: The Pd-containing PMO material (Pd-LHMS-3) showed excellent catalytic activity in fluoride-free Hiyama cross-coupling reactions in water at alkaline pH conditions.

Journal ArticleDOI
TL;DR: The average lifetime of GO at pH 4 increases in the GO-PVA1 hybrid, indicating the formation of a more stable excited state but the increase in lifetime value after addition of Au(3+) salt solution to the hybrid solution indicates dynamic quenching.
Abstract: We have developed a new highly fluorescent graphene oxide (GO)/poly(vinyl alcohol) (PVA) hybrid (GO-PVA) in an acidic medium (pH 4). Fourier transform infrared (FTIR) spectra indicate the formation of hydrogen bonds between the hydroxy group of PVA and the hydroxy groups of GO. The hybrid is highly fluorescent, because of passivation by hydrogen bonding, as evident from Raman spectra. The quantum yields of GO-PVA hybrids are higher than that of GO. The fluorescent microscopic images of the hybrids exhibit a fibrillar morphology, and all of them emit highly intense green light. Field-emission scanning electron microscopy (FESEM) micrographs also show a fibrillar morphology, which is produced due to the supramolecular organization of GO-PVA complex. The highly fluorescent GO-PVA1 hybrid has been used as a fascinating tool for selective sensing of Au3+ ions in aqueous media with a detectable limit of ∼275 ppb. The sensitivity of the Au3+ ion (300 μM) in the presence of 600 μM concentrations of each ion (Cu2+...

Journal ArticleDOI
TL;DR: The critical parameters governing the design of luminescent lanthanide based core-shell nanostructures are identified to improve the luminescence efficiency by the elimination of deleterious cross-relaxation.
Abstract: This feature article highlights the new development and current status of rare-earth (RE) based core–shell nanocrystals, which is one of the new classes of hybrid nanostructures. Attractive properties of rare-earth based nanomaterials include extremely narrow emission bands, long lifetimes, large Stoke’s shifts, photostability and absence of blinking that can be exploited for biophotonic and photonic applications. Core–shell nanostructures have been attracting a great deal of interest to improve the luminescence efficiency by the elimination of deleterious cross-relaxation. The main focus of this feature article is to address the impacts of core–shell structures on the properties of lanthanide based nanocrystals including crystal phase, lattice strain, downconversion emission, upconversion emission and energy transfer. We describe general synthetic methodologies to design core–shell nanostructure materials. An interesting finding reported is that the local environment of an ion in the core–shell structure significantly affects the modifications of radiative and nonradiative relaxation mechanisms. Finally, a tentative outlook on future developments of this research field is given. Here, we attempt to identify the critical parameters governing the design of luminescent lanthanide based core–shell nanostructures.

Journal ArticleDOI
TL;DR: A fluorescence based cholesterol detection method has been developed using competitive host-guest interaction between graphene bound β-cyclodextrin (β-CD) with rhodamine 6G (R6G) and cholesterol.

Journal ArticleDOI
TL;DR: The synthesis of a new highly nitrogen rich porous covalent imine network (CIN-1) material employing simple Schiff base chemistry and further grafting its surface with palladium is reported, which acts as a truly heterogeneous catalyst towards Suzuki C-C coupling reaction between aryl halides with aryalboronic acids.
Abstract: In an effort to expand the realm of possibilities of nitrogen-rich porous materials that could be used in catalysis, herein we report the synthesis of a new highly nitrogen rich (ca. 45%) porous covalent imine network (CIN-1) material employing simple Schiff base chemistry and further grafting its surface with palladium. Pd-loaded CIN-1 support acts as a truly heterogeneous catalyst towards Suzuki C–C coupling reaction between aryl halides with arylboronic acids. High surface area and excellent accessibility of the catalytic sites make it very efficient for heterogeneous catalysis. The stability of the catalyst due to intimate contact between nitrogen-rich organic support and metal allows several reuses with only a minor loss in catalytic activity.

Journal ArticleDOI
TL;DR: Water-soluble fluorescent gold clusters (AuCs) have been successfully synthesized by a wet-chemical approach at room temperature using a dipeptide l-cysteinyl-l-cysteine to develop the new fluorescent sensor for the selective and ultra-sensitive detection of As(III) ions in the presence of other bivalent and trivalent metal ions in aqueous solution.
Abstract: Water-soluble fluorescent gold clusters (AuCs) have been successfully synthesized by a wet-chemical approach at room temperature using a dipeptide L-cysteinyl-L-cysteine. We have followed the core-etching mechanism for the synthesis of the gold clusters. Clusters show the excitation maximum at 300 nm and the emission maximum at 410 nm. These gold clusters show interesting fluorescent properties including large Stoke's shift (110 nm), with a quantum yield of 41.3%, and photochemical stability. Transmission electron microscopic analysis shows that most of these particles are <1.5 nm. These clusters have been applied successfully to develop the new fluorescent sensor for the selective and ultra-sensitive detection of AsIII ions in the presence of other bivalent and trivalent metal ions in aqueous solution with a lower detection limit of 53.7 nM and this is far below the permissible limit (133 nM) of arsenic in drinking water permitted by WHO and USEPA. These gold clusters also show semiconducting behavior.

Journal ArticleDOI
TL;DR: Hydrogen-bonding-mediated, spontaneous J-aggregation of NDI-1 and unprecedented aggregation-induced white-light emission are revealed and ascertains that hydrogen- bonding among the free carboxylic acid functionalities is indeed responsible for the observed self-assembly.
Abstract: Supramolecular assembly of various functional p systems has been investigated extensively in recent decades with the aim to achieve precise control over the mode of their spatial organization, which governs the photophysical properties of the resulting self-assembled material. Such self-assembled materials with hierarchical structure and defined photophysical properties are considered as promising candidates for applications ranging from biology to materials science. Hydrogen-bonding interactions have played a pivotal role in generating various supramolecular nanostructures from suitably designed small molecular building blocks. While many structurally complex hydrogen-bonding motifs have been utilized to fulfill this objective, surprisingly not much is known regarding the utility of simple selfcomplementary hydrogen-bonding functionalities, such as carboxylic acid, in the context of chromophore assembly. Considering structural simplicity and versatile hydrogenbonding motifs of carboxylic acid group as described in the literature related to crystal engineering, we envisaged it would be worth exploring its utility as a structure-directing functionality in self-assembly of organic functional p-systems. In the recent past, we have been engaged in understanding effect of structural variations on hydrogen-bonding mediated self-assembly of 1,4,5,8-naphthalenetetracarboxdiACHTUNGTRENNUNGimide (NDI) derivatives due to the prospect of using this particular chromophore as an n-type semiconductor. NDI derivatives have also been extensively utilized as building blocks for various elegant supramolecular materials, such as synthetic ion channels, organogels, hydrogels, nanotubes, catenanes, rotaxanes, foldamers, supramolecular photosystems, nanoparticles, and other amphiphilic nanostructures. As a part of our continuing interest in self-assembly of NDI chromophore, we synthesized NDI-1 (Figure 1), which contains a carboxylic acid group that is capable of forming a self-complementary hydrogen-bonding network and a dodecyl chain to provide enhanced solubility in relatively nonpolar solvents. Herein we revealed hydrogen-bonding-mediated, spontaneous J-aggregation of NDI-1 and unprecedented aggregation-induced white-light emission. Self-assembly of NDI-1 was primarily investigated by solvent-dependent UV/Vis studies (Figure 1). In CHCl3, a good solvent for solvating extended p systems, NDI-1 shows wellresolved sharp absorption bands in the range of 300–400 nm due to a p–p* transition along the long axis of the chromophore in the monomeric state. Going from CHCl3 to a less polar solvent, methylcyclohexane (MCH), the absorption bands exhibited drastic reduction in intensity with concomitant redshift of 14 nm, which can be considered as strong evidence for J-type p stacking among the NDI-chromophores. 14,21] Note that for the control molecule NDI-2 (Figure 1), in which the carboxylic acid group was replaced by its methyl ester, no such solvent-dependent changes in the absorption spectra were observed (Figure 1), except for a slight blueshift due to a trivial solvatochromic effect. This ascertains that hydrogen-bonding among the free carboxylic acid functionalities is indeed responsible for the observed self-assembly. Existence of hydrogen bonding was further [a] M. R. Molla, Dr. S. Ghosh Polymer Science Unit Indian Association for the Cultivation of Science 2A & 2B Raja S. C. Mullick Rd. Kolkata, 700032 (India) Fax: (+91) 33-2473-2805 E-mail : psusg2@iacs.res.in Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201103600. Figure 1. Top: Structure of various NDI chromophores. Bottom: Solventdependent (dashed line-CHCl3, solid line-MCH) UV/Vis absorption spectra of NDI-1 (black line) and NDI-2 (gray line); concentration =0.1 mm, T= 25 8C, path length =1 cm. Inset: Variable-temperature UV/Vis absorption spectra of NDI-1 (concentration=0.1 mm) in MCH/CHCl3 (95:5).

Journal ArticleDOI
TL;DR: Fluorescence and electron microscopic images reveal NSBC binds on the bacterial cell wall, which cause irreversible membrane damage eventually leading to cell death, and Proteomic analysis demonstrates down regulation of protein expression, inhibition of cytosolic and membrane proteins and leakage of cellular content following binding of NSBC withacterial cell wall.

Journal ArticleDOI
TL;DR: This paper describes the spontaneous vesicular assembly of a naphthalene-diimide (NDI)-based non-ionic bolaamphiphile in aqueous medium by using the synergistic effects of π-stacking and hydrogen bonding to protect these moieties from the bulk water so that the distinct role of hydrogen bonding in the self-assembly of hydrazide-functionalized NDI building blocks could be realized.
Abstract: This paper describes the spontaneous vesicular assembly of a naphthalene-diimide (NDI)-based non-ionic bolaamphiphile in aqueous medium by using the synergistic effects of π-stacking and hydrogen bonding. Site isolation of the hydrogen-bonding functionality (hydrazide), a strategy that has been adopted so elegantly in nature, has been executed in this system to protect these moieties from the bulk water so that the distinct role of hydrogen bonding in the self-assembly of hydrazide-functionalized NDI building blocks could be realized, even in aqueous solution. Furthermore, the electron-deficient NDI-based bolaamphiphile could engage in donor-acceptor (D-A) charge-transfer (CT) interactions with a water-insoluble electron-rich pyrene donor by virtue of intercalation of the latter chromophore in between two NDI building blocks. Remarkably, even when pyrene was located between two NDI blocks, intermolecular hydrogen-bonding networks between the NDI-linked hydrazide groups could be retained. However, time-dependent AFM studies revealed that the radius of curvature of the alternately stacked D-A assembly increased significantly, thereby leading to intervesicular fusion, which eventually resulted in rupturing of the membrane to form 1D fibers. Such 2D-to-1D morphological transition produced CT-mediated hydrogels at relatively higher concentrations. Instead of pyrene, when a water-soluble carboxylate-functionalized pyrene derivative was used as the intercalator, non-covalent tunable in-situ surface-functionalization could be achieved, as evidenced by the zeta-potential measurements.

Journal ArticleDOI
TL;DR: It may be proposed that the radical pathway is probably responsible for conversion of 3, 5-DTBC to 3,5-DTBQ promoted by complexes of redox-innocent Zn(II) ion.
Abstract: Four dinuclear and three mononuclear ZnII complexes of phenol-based compartmental ligands (HL1–HL7) have been synthesized with the aim to investigate the viability of a radical pathway in catecholase activity. The complexes have been characterized by routine physicochemical studies as well as X-ray single-crystal structure analysis: [Zn2(H2L1)(OH)(H2O)(NO3)](NO3)3 (1), [Zn2L2Cl3] (2), [Zn2L3Cl3] (3), [Zn2(L4)2(CH3COO)2] (4), [Zn(HL5)Cl2] (5), [Zn(HL6)Cl2] (6), and [Zn(HL7)Cl2] (7) [L1–L3 and L5–L7 = 2,6-bis(R-iminomethyl)-4-methylphenolato, where R= N-ethylpiperazine for L1, R = 2-(N-ethyl)pyridine for L2, R = N-ethylpyrrolidine for L3, R = N-methylbenzene for L5, R = 2-(N-methyl)thiophene for L6, R = 2-(N-ethyl)thiophene for L7, and L4 = 2-formyl-4-methyl-6-N-methylbenzene-iminomethyl-phenolato]. Catecholase-like activity of the complexes has been investigated in methanol medium by UV–vis spectrophotometric study using 3,5-di-tert-butylcatechol as model substrate. All complexes are highly active in catal...