Showing papers by "Indian Association for the Cultivation of Science published in 2011"

Colloquium: Nonequilibrium dynamics of closed interacting quantum systems

Abstract: This Colloquium gives an overview of recent theoretical and experimental progress in the area of nonequilibrium dynamics of isolated quantum systems There is particularly a focus on quantum quenches: the temporal evolution following a sudden or slow change of the coupling constants of the system Hamiltonian Several aspects of the slow dynamics in driven systems are discussed and the universality of such dynamics in gapless systems with specific focus on dynamics near continuous quantum phase transitions is emphasized Recent progress on understanding thermalization in closed systems through the eigenstate thermalization hypothesis is also reviewed and relaxation in integrable systems is discussed Finally key experiments probing quantum dynamics in cold atom systems are overviewed and put into the context of our current theoretical understanding

Immobilization of bio-macromolecules on self-assembled monolayers: methods and sensor applications

Abstract: Attachment of biomolecules on gold, silicon or glass surfaces has direct implications for the development of novel biosensors in the context of nanoscale detection of pathogens and other metabolites related to issues of human health. In this critical review, we have highlighted the current developments in various techniques of immobilization of biomolecules, specifically biological macromolecules on surfaces through the modification of a functional self-assembled monolayer. The utility of such immobilized biomolecules in the area of biosensing in nanoscale has been surveyed. Merits and demerits of some of the methods with reference to sensitivity of detection and practical use have been discussed (221 references).

Exchange bias effect in alloys and compounds

Abstract: The phenomenology of exchange bias effects observed in structurally single-phase alloys and compounds but composed of a variety of coexisting magnetic phases such as ferromagnetic, antiferromagnetic, ferrimagnetic, spin-glass, cluster-glass and disordered magnetic states are reviewed. The investigations on exchange bias effects are discussed in diverse types of alloys and compounds where qualitative and quantitative aspects of magnetism are focused based on macroscopic experimental tools such as magnetization and magnetoresistance measurements. Here, we focus on improvement of fundamental issues of the exchange bias effects rather than on their technological importance.

Surface Defect-Related Luminescence Properties of SnO2 Nanorods and Nanoparticles

Abstract: We demonstrate the surface defect-related luminescence properties of SnO2 nanorods and nanoparticles using steady-state and time-resolved spectroscopy. Defect-related bands are identified by Raman and EPR spectroscopy. On the basis of the experimental results, we propose a schematic model for different relaxation processes in SnO2 nanocrystals upon photoexcitation. Analysis suggests that the visible emission of SnO2 nanocrystals is due to a transition of an electron from a level close to the conduction band edge to a deeply trapped hole in the bulk (V0••) of the SnO2 nanocrystals. Analysis suggests that the surface-related defects are more prominent in smaller nanocrystals than in nanorods. It is found that the PL emission and decay time strongly depend on the shape of the nanocrystals. This proposed model is further confirmed by time-resolved spectroscopy.

Supramolecular Self-Assembly of M-IDA Complexes Involving Lone-Pair···π Interactions: Crystal Structures, Hirshfeld Surface Analysis, and DFT Calculations [H2IDA = iminodiacetic acid, M = Cu(II), Ni(II)]

Abstract: Mononuclear copper(II) and nickel(II) complexes, [(C5H6N2)Cu(IDA)(H2O)] (1) and (C5H7N2)2[Ni(IDA)2(H2O)] (2) [H2IDA = iminodiacetic acid; C5H6N2 = 4-aminopyridine; C5H7N2 = protonated 2-aminopyridine], have been synthesized, and their crystal structures were solved using single crystal X-ray diffraction data. A detailed analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions, which are crucial in building different supramolecular architectures. Molecules are linked by a combination of N–H···O, O–H···O and C–H···O hydrogen bonds into two-dimensional framework, whose formation is readily analyzed in terms of substructures of lower dimensionality with zero finite zero-dimensional dimeric units as the building blocks within the structures. Moreover, the aromatic molecules that are engaged in lone pair···π interactions with the noncoordinated carbonyl moieties play a crucial role in stabilizing the self-assembly process observed for both complexes. Intricate...

Doping Cu in semiconductor nanocrystals: some old and some new physical insights.

Abstract: Cu-doped inorganic semiconductors with concomitant optical properties have garnered enormous research interest in the last two decades. However, uncertainties over the origin of Cu emission, its oxidation state, resemblance with trap state emission, position of Cu d-state, emission spectral width, and moreover understanding of the doping mechanism restricted the wide development of the synthetic methodology for high-quality Cu-doped nanocrystals. It has been shown recently that the emission from Cu-doped semiconductor nanocrystals can span over a wide spectral window and could be a potential color tunable dispersed nanocrystal emitter. Herein, we report the size and composition of variable Cu-doped ZnS/Zn1−xCdxS zinc-blende (ZB) surface alloyed nanocrystals with intense, stable, and tunable emission covering the blue to red end of the visible spectrum. Further, the Cu dopant emission is distinguished from trap state emission, and the composition variable spectral broadening has been justified on the accou...

Advances in Light-Emitting Doped Semiconductor Nanocrystals

Abstract: Insertion of just a few impurity atoms in a host semiconductor nanocrystal can drastically alter its phase, shape, and physical properties. Such doped nanomaterials now constitute an important class of optical materials that can provide efficient, stable, and tunable dopant emission in visible and NIR spectral windows. Selecting proper dopants and inserting them in appropriate hosts can generate many new series of such doped nanocrystals with several unique and attractive properties in order to meet current challenges in the versatile field of luminescent materials. However, the synthesis of such doped nanomaterials with a specific dopant in a predetermined host at a desired site leading to targeted optical properties requires fundamental understanding of both the doping process as well as the resulting photophysical properties. Summarizing up to date literature reports, in this Perspective we discuss important advances in synthesis methods and in-depth understanding of the optical properties, with an emp...

Use of π–π forces to steer the assembly of chromone derivatives into hydrogen bonded supramolecular layers: crystal structures and Hirshfeld surface analyses

Abstract: Two chromone derivatives C11H10O3 (1) and C11H10O2 (2) have been synthesized and characterized by X-ray structural studies with a detailed analysis of the Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures. The title compounds are associated through π–stacking interactions and the linear stacking of π–π forces can be thought as the influencing agent for the organization of the title compounds into hydrogen bonded supramolecular layers and are responsible as well for the strengthening of the molecular assembly. Investigation of the intermolecular interactions and crystal packing via Hirshfeld surface analysis reveals that more than two-thirds of the close contacts are associated with weak interactions. The fingerprint plots demonstrate that these weak interactions are important for both local and crystal packing. A comparison of the Hirshfeld surface in the compounds with similar substituted chromone derivatives in the Cambridge Structural Database (CSD) has been presented.

Inverse barocaloric effect in the giant magnetocaloric La-Fe-Si-Co compound.

Abstract: Application of hydrostatic pressure under adiabatic conditions causes a change in temperature in any substance. This effect is known as the barocaloric effect and the vast majority of materials heat up when adiabatically squeezed, and they cool down when pressure is released (conventional barocaloric effect). There are, however, materials exhibiting an inverse barocaloric effect: they cool when pressure is applied, and they warm when it is released. Materials exhibiting the inverse barocaloric effect are rather uncommon. Here we report an inverse barocaloric effect in the intermetallic compound La-Fe-Co-Si, which is one of the most promising candidates for magnetic refrigeration through its giant magnetocaloric effect. We have found that application of a pressure of only 1 kbar causes a temperature change of about 1.5 K. This value is larger than the magnetocaloric effect in this compound for magnetic fields that are available with permanent magnets. When materials change temperature as a result of the application of pressure or a change in the magnetization, they are said to display a barocaloric or magnetocaloric effect, respectively. This study reports a substantial barocaloric effect in the giant magnetocaloric material LaFe11.33Co0.47Si1.2.

On the Possibility of Tuning Molecular Edges To Direct Supramolecular Self-Assembly in Coumarin Derivatives through Cooperative Weak Forces: Crystallographic and Hirshfeld Surface Analyses

Abstract: Four organic compounds based on substituted coumarin derivatives (1–4) have been synthesized and characterized by X-ray structural studies with a detailed analysis of Hirshfeld surface and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular architectures. The X-ray study reveals that in the molecular packing C–H···O, π···π, and carbonyl (lone pair)···π interactions cooperatively take part. The recurring feature of the self-assembly in all the compounds is the appearance of the molecular ribbon through weak hydrogen bonding. These hydrogen bonded ribbons further stacked into molecular layers by π···π forces. The mode of cooperativity of the weak C–H···O and π···π forces is such that they operate in mutually perpendicular directions — hydrogen bonding in the plane of the molecule at their edges and π-stacking perpendicular to the molecular plane. Investigation of intermolecular interactions and crystal packing via Hirshfeld surface analyses reveals...

Amino acid based smart hydrogel: formation, characterization and fluorescence properties of silver nanoclusters within the hydrogel matrix

Abstract: N-Terminally Fmoc protected amino acid, Fmoc-Phe-OH (Fmoc-L-Phenylalanine-OH), forms an efficient, stable and transparent hydrogel with a minimum gelation concentration of 0.1% w/v. This hydrogel has been nicely utilized to prepare and stabilize fluorescent few-atom silver nanoclusters. Interestingly, in absence of any toxic reducing agents in a water medium, silver ions are complexed with the carboxylate group of the Fmoc-Phe-OH gelator, and they are reduced spontaneously in the presence of diffused sunlight at physiological pH (7.46) and room temperature to form silver nanoclusters. The three dimensional structure provided by the hydrogel helps to stabilize newly formed silver nanoclusters within the hydrogel matrix. These clusters have been examined using UV-Vis, photoluminescence spectroscopy, high resolution transmission electron microscopy (HR-TEM), X-ray powder diffraction (XRPD) and matrix-assisted laser-desorption ionization (MALDI) mass spectrometric analysis. MALDI mass spectrometric analysis shows the presence of just a few atoms within the silver cluster as Ag4. These silver nanoclusters exhibit interesting fluorescent properties including large Stokes shift (more than 110 nm), narrow emission band width (36 ± 1 nm) and a quantum yield of 3.76%. These silver nanoclusters are stable for up to 4 months of storage at 4 °C in the dark. The morphology of the hydrogel changes after the encapsulation of silver ions within the gel and this altered morphology is retained after the formation of silver nanoclusters within the gel. Interestingly, the rheological properties of the hydrogel alone are different from that of the silver nanocluster-containing hydrogel.

Insight into supramolecular self-assembly directed by weak interactions in acetophenone derivatives: crystal structures and Hirshfeld surface analyses

Abstract: The crystallographic study of four acetophenone derivatives (1–4) is reported in the context of crystal engineering with a detailed analysis of Hirshfeld surfaces and fingerprint plots facilitating a comparison of intermolecular interactions in building different supramolecular self-assemblies. The X-ray study reveals that molecules of 1–4 are linked by cooperative weak C–H⋯O, C–H⋯π and π⋯π stacking interactions which are responsible for the formation and strengthening of molecular assembly. The substituting benzyl units are used as a potential scaffold for designing supramolecular self-assemblyvia C–H⋯π forces. Investigation of Hirshfeld surface analysis reveals a much more detailed scrutiny in comparison to these weak forces experienced by each compound. A comparison of Hirshfeld surfaces in the title derivatives with similar substituted and unsubstituted structures retrieved from the Cambridge Structural Database (CSD) has been presented.

Short peptide based hydrogels: incorporation of graphene into the hydrogel

Abstract: Stable supramolecular hydrogels were obtained from Fmoc (N-fluorenyl-9-methoxycarbonyl) protected synthetic dipeptides, Fmoc-Xaa-Asp-OH (Xaa = Tyr, Phe). These hydrogels were characterized by various methods including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), fluorescence spectroscopy and rheology. Different microscopic studies showed the presence of an entangled uniform nanofibrillar network structure in the gel state. These gelator molecules containing aromatic moieties in the side chain (Tyr/Phe) and in the N-terminus (fluorenyl group) can be useful in interacting with graphene sheets using π–π stacking interactions. One of these peptide based hydrogels (Fmoc-Tyr-Asp-OH) was utilized for the successful incorporation of reduced graphene oxide (RGO) into the hydrogel to make a well-dispersed RGO containing stable hybrid hydrogel. This study demonstrates that RGO is stabilized within the peptide based hydrogel system without the help of any external stabilizing agent. The RGO containing hybrid hydrogel was characterized using transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman spectroscopy, and rheology. Morphological studies reveal the presence of a nano-hybrid system containing graphene (RGO) sheets and gel nanofibrils. The morphology of the peptide hydrogel does not change significantly even after the incorporation of RGO as it is evident from TEM and AFM studies. Rheological studies suggest the formation of a more rigid and ‘solid-like’ hybrid hydrogel after the incorporation of RGO into the native hydrogel.

Pyrene‐Containing Peptide‐Based Fluorescent Organogels: Inclusion of Graphene into the Organogel

Abstract: The N-terminally pyrene-conjugated oligopeptide, Py-Phe-Phe-Ala-OMe, (Py=pyrene 1-butyryl acyl) forms transparent, stable, supramolecular fluorescent organogels in various organic solvents. One of these organogels was thoroughly studied using various techniques including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), Fourier-transform infrared (FTIR) spectroscopy, photoluminescence (PL) spectroscopy, and rheology. Unfunctionalized and non-oxidized graphene was successfully incorporated into this fluorescent organogel in o-dichlorobenzene (ODCB) to form a stable hybrid organogel. Graphene is well dispersed into the gel medium by using non-covalent π-π stacking interactions with the pyrene-conjugated gelator peptide. In the presence of graphene, the minimum gelation concentration (mgc) of the hybrid organogel was lowered significantly. This suggests that there is a favorable interaction between the graphene and the gelator peptide within the hybrid organogel system. This hybrid organogel was characterized using TEM, AFM, FTIR, PL, and rheological studies. The TEM study of graphene-containing hybrid organogel revealed the presence of both graphene sheets and entangled gel nanofibers. The AFM study indicated the presence of 3 to 4 layers in exfoliated graphene in ODCB and the presence of both graphene nanosheets and the network of gel nanofibers in the hybrid gel system. The rheological investigation suggested that the flow of the hybrid organogel had become more resistant towards the applied angular frequency upon the incorporation of graphene into the organogel. The hybrid gel is about seven times more rigid than that of the native gel.

Active site environment of heme-bound amyloid β peptide associated with Alzheimer's disease.

Abstract: Recent reports show that there is a large increase in heme in the temporal brain of Alzheimer’s disease (AD) patients, as heme, biosynthesized in brain cells, binds to amyloid β (Aβ), forming heme−...

Microwave assisted rapid conversion of carbohydrates into 5-hydroxymethylfurfural catalyzed by mesoporous TiO2 nanoparticles

Abstract: Energy efficient and sustainable process for the production of 5-hydroxymethylfurfural (HMF) from carbohydrates is highly demanding. Here, direct conversion of carbohydrates into HMF has been investigated over self-assembled mesoporous TiO2 nanoparticles (NPs) catalyst. Monosachharides d -fructose and d -glucose, disaccharides sucrose, maltose, cellobiose were successfully converted into HMF with variable yields in both aqueous and organic mediums under microwave-assisted heating conditions. The effects of solvent polarity, microwave absorbing ability, catalyst loading, reaction time, and substrate variations on the HMF yields have been studied. Pyridine-IR and NH3-TPD analyses confirmed the presence of Lewis acidic sites, whereas N2 sorption analysis revealed high BET surface area for the self-assembled mesoporous TiO2 nanomaterials synthesized by using sodium salicylate as template. High surface area, Lewis acidity and uniform nanosphere-like particle morphology are responsible for high catalytic activity in the dehydration of carbohydrate substrates over this mesoporous TiO2 nanomaterial, whereas commercially available TiO2 is almost inactive for this dehydration reaction under similar conditions. The higher microwave energy absorbing ability (tan δ) of the DMSO and NMP resulted in higher HMF yield in organic solvents than water. Catalyst life-time analysis suggested that mesoporous TiO2 NPs catalysts can be recycled for four catalytic cycles without appreciable loss of its catalytic activity.

Multicomponent hydrogels from enantiomeric amino acid derivatives: helical nanofibers, handedness and self-sorting

Abstract: In this study, chiral helical nanofibers have been obtained from suitable, co-assembling, two oppositely charged amino acid based two component hydrogels. An equimolar mixture of an N-terminally protected amino acid Fmoc-(L/D)Glu (Fmoc: N-fluorenyl-9-methoxycarbonyl, Glu: glutamic acid) and (L/D)Lys (Lys: lysine) can co-assemble to form hydrogels. These hydrogels have been characterised using circular dichroism (CD), atomic force microscopy (AFM), transmission electron microscopy (TEM), X-ray powder diffraction, fluorescence spectroscopic and rheological studies. CD and AFM studies have been extensively used to examine the chiral/achiral nature of fibers obtained from different hydrogel systems. The equimolar mixture of two L-isomers, {Fmoc-(L)Glu + (L)Lys} in the assembled state, leads to the exclusive formation of left-handed helical nanofibers, whereas an equimolar mixture of two D-isomers, {Fmoc-(D)Glu + (D)Lys}, gives rise to right-handed helical nanofibers. The CD study of the gel obtained from the {Fmoc-(L)Glu + (L)Lys} system is exactly the mirror image of the CD signal obtained from the gel of the {Fmoc-(D)Glu + (D)Lys} system. These results suggest that the molecular chirality is being translated into the supramolecular helicity and the handedness of these fibers depends on the corresponding molecular chirality in the mixture of the two component system. Reversing the handedness of helical fibers is possible by using enantiomeric building blocks. Co-assembly of racemic and equimolar mixtures of all four components, i.e., [{Fmoc-(L)Glu + (L)Lys} + {Fmoc-(D)Glu + (D)Lys}] can also form hydrogels. Interestingly, in this racemic mixture self-sorting has been observed with the presence of almost equal amount of left- and right-handed helical nanofibers. The equimolar mixture of Fmoc-(L)Glu and L-ornithine/L-arginine also produces hydrogel with left-handed helical fibers. Moreover, the straight fiber has been observed from the two component hydrogel {Fmoc-(L)Glu + (L)Lys} system in the presence of Ca2+/Mg2+ ions. This indicates the straight nanofibers are obtained under suitable conditions and acid–base interaction is responsible for making the helical fibers at the nanoscale.

Zinc(II) and PPi selective fluorescence OFF-ON-OFF functionality of a chemosensor in physiological conditions.

Abstract: A fluorescent chemosensor based on a quinoline derivative, L2 (OFF state), selectively senses Zn2+ by effective chelate-enhanced fluorescence (ON state), which further shows selectivity toward PPi over competing anions like Pi, AMP, and ATP via fluorescence quenching (OFF state) in a 100% aqueous HEPES buffer (pH 7.4). A plausible mode for the selective binding of PPi to 1 has been demonstrated by quantum mechanical density functional theory calculations and high-resolution mass spectrometry analysis.

Interaction of Gold Nanoparticle with Human Serum Albumin (HSA) Protein Using Surface Energy Transfer

Abstract: Here, we study the human serum albumin (HSA) protein–Au nanoparticle interaction to identify the specific binding site of protein with nanoparticles by using the surface energy transfer (SET) method among tryptophan (Trp) of HSA, ANS-dye-labeled HSA protein, and Au nanoparticles. Here, ANS dye is used as a probe located at domain IIIA of HSA. In particular, absorbance, fluorescence quenching, decay time, circular dichroism, dynamic light scattering, and TEM measurements are performed to understand the physical properties of protein-conjugated Au nanoparticles. Using the SET method, the measured distances between the Trp residue of HSA and the binding site of HSA interacting with Au nanoparticles are 42.5, 41.9, and 48.1 A for 1.5, 2.0, and 2.9 nm HSA-conjugated Au nanoparticles, respectively. The measured distances between the binding site of ANS dye (located at domain IIIA) in HSA to the binding site of HSA interacting with Au nanoparticles are 51, 51.5, and 54.7 A for 1.5, 2.0, and 2.9 nm HSA-conjugated...

Heme-Cu bound aβ peptides: spectroscopic characterization, reactivity, and relevance to Alzheimer's disease.

Abstract: Recently, it has been shown that heme binds to Aβ peptides which may play a major role in Alzheimer's disease (AD). This study illustrates that Aβ peptides can bind both Cu and heme cofactors at the same time. Both cofactors have unique spectroscopic and electrochemical features which are unaffected in the presence of the other, implying that they are electronically, chemically, and electrochemically uncoupled. These data clearly indicate that Cu cannot bind to three histidine residues simultaneously in Cu-Aβ complexes as previously proposed, since one of the histidines is involved in binding heme. The heme-Aβ and the heme-Cu-Aβ peptide complexes function as peroxidases. Interestingly, the Cu-Aβ complex also exhibits peroxidase activity, which may have significant implications in AD. Both Cu(+)-Aβ and heme (Fe(2+))-Aβ complexes reduce O(2) to H(2)O(2) quantitatively. Only one of the two electrons that are required for the reduction of O(2) to H(2)O(2) is derived from the reduced metal site, while the Tyr(10) residue of the native Aβ peptide donates the second electron. This Tyr(10) residue, the source of electron for the generation of partially reduced oxygen species (PROS, e.g., H(2)O(2)) is absent in rodents, which do not get affected by AD. When both heme and Cu are bound to the Aβ peptides, which is likely to happen physiologically, the amount of toxic PROS generated is maximum, implying that heme-Cu-Aβ complexes could potentially be most toxic for AD.

Highly efficient mesoporous base catalyzed Knoevenagel condensation of different aromatic aldehydes with malononitrile and subsequent noncatalytic Diels–Alder reactions

Abstract: Knoevenagel condensation and [4 + 2] cycloaddition reactions are very important class of reactions in synthetic organic chemistry. We have prepared amino-functionalized mesoporous silica through co-condensation of 3-aminopropyltriethoxy-silane (APTES) along with tetraethylorthosilicate (TEOS) in presence of a cationic surfactant CTAB hydrothermally. Small angle powder XRD, HR TEM, FE SEM, N 2 sorption and FT IR spectroscopic tools are used to characterize the 2D-hexagonal mesostructure and to identify the presence of surface –NH 2 groups in amino-functionalized mesoporous silica material. Our experimental results reveal that amino-functionalized mesoporous silica is an efficient base catalyst for the Knoevenagel condensation of different aromatic aldehydes with malononitrile to α,β-unsaturated dicyanides under very mild reaction condition and in the presence of ethanol solvent. The isolated α,β-unsaturated dicyanides obtained through the condensation reaction further react very efficiently with cyclopentadiene to form a series of Diels–Alder cycloaddition products in excellent yields in the absence of any catalyst.

Synthesis, Characterization, and Biofuel Application of Mesoporous Zirconium Oxophosphates

Abstract: Mesoporous zirconium oxophosphates have been synthesized through the evaporation-induced self-assembly (EISA) method in the presence of an amphiphilic block copolymer, pluronic F127 as template under strongly acidic conditions. The mesophases of the materials were analyzed by using small-angle powder X-ray diffractions and transmission electron microscopic (TEM) image analysis. N2 adsorption−desorption studies showed high surface area (260−312 m2 g−1) and narrow pore size distribution (4.5−5.5 nm) for the materials. NH3-TPD and pyridine-IR analyses suggested the presence of strong Lewis and Bronsted acid sites. These mesoporous materials showed excellent catalytic activity in biodiesel reaction for the effective conversion of the long chain fatty acids to their respective methyl esters. The maximum biodiesel yield was about 91% under optimal reaction conditions. High catalytic activity could be attributed to the large surface area and the presence of large number of acidic sites located at the surface of ...

Core–shell TiO2@ZnO nanorods for efficient ultraviolet photodetection

Abstract: Core–shell TiO2@ZnO nanorods (NRs) have been fabricated by a simple two step method: growth of ZnO NRs' array by an aqueous chemical technique and then coating of the NRs with a solution of titanium isopropoxide [Ti(OC3H7)4] followed by a heating step to form the shell. The core–shell nanocomposites are composed of single-crystalline ZnO NRs, coated with a thin TiO2 shell layer obtained by varying the number of coatings (one, three and five times). The ultraviolet (UV) emission intensity of the nanocomposite is largely quenched due to an efficient electron–hole separation reducing the band-to-band recombinations. The UV photoconductivity of the core–shell structure with three times TiO2 coating has been largely enhanced due to photoelectron transfer between the core and the shell. The UV photosensitivity of the nanocomposite becomes four times larger while the photocurrent decay during steady UV illumination has been decreased almost by 7 times compared to the as-grown ZnO NRs indicating high efficiency of these core–shell structures as UV sensors.

New mesoporous perovskite ZnTiO3 and its excellent catalytic activity in liquid phase organic transformations

Abstract: A new mesoporous perovskite ZnTiO3 material has been synthesized by the evaporation-induced self-assembly (EISA) method using non-ionic surfactant Pluronic P123 as template. After calcination of the dried gel of equimolar concentrations of Zn(II) and Ti(IV) at 673 K, a new perovskite mesophase of ZnTiO3 (MZT-11) formed, having highly crystalline cubic ZnTiO3 pore wall. Interestingly, in the absence of P123 but otherwise identical synthesis conditions showed no cubic structure and a mixed phase consisting of ZnO and TiO2 phases (ZT-11). The BET surface area of the mesoporous perovskite materials (MZT-11) was 136 m2 g−1 and the average dimension of the pores was ca. 5.1 nm. The material was thoroughly characterized by different analytical methods including small and wide angle powder XRD, FE SEM, TEM, FT IR, UV–visible, photoluminescence (PL) and X-ray fluorescence (XRF) analysis. This new mesoporous perovskite material showed excellent catalytic activity in the Friedel-Crafts (FC) benzylation of aromatics and in the Fischer esterification of different long chain carboxylic acids in the presence of methanol under solvent-free conditions.

Aggregation Behavior of SDS/CTAB Catanionic Surfactant Mixture in Aqueous Solution and at the Air/Water Interface

Abstract: Herein, we report the aggregation behavior of catanionic mixtures of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) in solution and at the air/water interface obtained by the Langmuir–Blodgett (LB) technique. We employed Fourier transform infrared spectroscopy, in situ phase-contrast inverted microscopy, scanning electron microscopy, and atomic force microscopy to characterize the systems in solution, at the air/water interface, and in LB films. We found spherical vesicles at the SDS/CTAB ratio of 35/65 in aqueous solution and an ordered aggregated morphology called surface micelles at SDS/CTAB ratios of 35/65 to 65/35 at the air/water interface. Other mixtures (SDS/CTAB = 90/10, 10/90) were found to contain mostly disordered aggregated microstructures. An in situ time-dependent study of surface micelle formation at the air/water interface showed micelle ripening through the fusion of smaller micelles. These micelles were successfully ...

Applications of nanomaterials in the different fields of photosciences

Abstract: Current developments in nanostructured materials and nanotechnology will have profound impact in many areas such as energy technologies and biomedical applications. These include solar cells, energy storage, environmental control, tissue engineering, bioprobe, biomarking, cancer diagnosis, cancer therapy, and drug delivery. Our recent work covers a wide range of nanomaterials research for a variety of applications including to produce organic-inorganic nanocomposites which will be used in for constructing light emitting diodes, photovoltaic cells, future organic solar cells etc, biomedicine and photocatalytic. In this article the chief scientific and technical aspects of nanotechnology are introduced and some of its potential applications have been discussed.