Showing papers by "National Chemical Laboratory published in 2009"

Enhanced conversion efficiency in dye-sensitized solar cells based on hydrothermally synthesized TiO2-MWCNT nanocomposites.

Abstract: A 50% enhancement in the conversion efficiency (4.9−7.37%) is realized in dye-sensitized solar cells using hydrothermally synthesized TiO2−multiwalled carbon nanotube (MWCNT) nanocomposites as compared to hydrothermally synthesized TiO2 without MWCNT and Degussa P25. Several characterizations have been employed to reveal the nature of the modification imparted to the MWCNTs under hydrothermal processing conditions and the resulting TiO2−MWCNT conjugation through −COOH groups. Efficient charge transfer in the nanocomposite and efficient electron transport by MWCNT (significantly higher incident-photon-to-current conversion efficiency) are suggested to be the possible reasons for the enhancement.

Acetalization of glycerol using mesoporous MoO3/SiO2 solid acid catalyst

Abstract: Acetalization of glycerol with various aldehydes has been carried out using mesoporous MoO3/SiO2 as a solid acid catalyst A series of MoO3/SiO2 catalysts with varying MoO3 loadings (1–20 mol%) were prepared by sol–gel technique using ethyl silicate-40 and ammonium heptamolybdate as silica and molybdenum source respectively The sol–gel derived samples were calcined at 500 °C and characterized using various physicochemical characterization techniques The XRD of the calcined samples showed the formation of amorphous phase up to 10 mol% MoO3 loading and at higher loading of crystalline α-MoO3 on amorphous silica support TEM analyses of the materials showed the uniform distribution of MoO3 nanoparticles on amorphous silica support Raman spectroscopy showed the formation of silicomolybdic acid at low Mo loading and a mixture of α-MoO3 and polymolybdate species at high Mo loadings Moreover the Raman spectra of intermediate loading samples also suggest the presence of β-MoO3 Acetalization of glycerol with benzaldehyde was carried out using series of MoO3/SiO2 catalysts with varying MoO3 loadings (1–20 mol%) Among the series, MoO3/SiO2 with 20 mol% MoO3 loadings was found to be the most active catalyst in acetalization under mild conditions Maximum conversion of benzaldehyde (72%) was obtained in 8 h at 100 °C with 60% selectivity for the six-membered acetal using 20% MoO3/SiO2 Interestingly with substituted benzaldehydes under same reaction conditions the conversion of aldehydes decreased with increase in selectivity for six-membered acetals These results indicate the potential of this catalyst for the acetalization of glycerol for an environmentally benign process

Estimation of Free Fatty Acid Content in Oils, Fats, and Biodiesel by 1H NMR Spectroscopy

Abstract: A novel 1H NMR method for the quantification of free fatty acid (FFA) content in vegetable oils, animal fats, and biodiesel is reported. Nonedible oils and animal fats, which are increasingly being explored as cheaper, renewable feed stocks for biodiesel production by transesterification with methanol, contain a significant amount of FFA along with other acidic impurities. The 1H NMR spectroscopic method is found to be more accurate than the conventional titrimetric analysis for the estimation of FFA content especially in those cases where acidic entities other than the FFA are also present in the feedstock. The titrimetric methods provide a gross acid value which corresponds to that of FFA and other acidic impurities. Our NMR method provides the FFA content exclusively. In the case of refined edible oils (wherein the other acidic impurities are negligible), the results obtained from the 1H NMR method are comparable with those from the titrimetic analysis.

Challenges associated with metal chelation therapy in Alzheimer's disease.

Abstract: A close association between brain metal dishomeostasis and the onset and/or progression of Alzheimer's disease (AD) has been clearly established in a number of studies, although the underlying biochemical mechanisms remain obscure. This observation renders chelation therapy an attractive pharmacological option for the treatment of this disease. However, a number of requirements must be fulfilled in order to adapt chelation therapy to AD so that the term "metal targeted strategies" seems now more appropriate. Indeed, brain metal redistribution rather than brain metal scavenging and removal is the major goal of this type of intervention. The most recent developments in metal targeted strategies for AD will be discussed using, as useful examples, clioquinol, curcumin, and epigallocatechin, and the future perspectives will also be outlined.

Combustion Synthesis of Triangular and Multifunctional ZnO1−xNx (x ≤ 0.15) Materials

Abstract: The preparation and characterization of multifunctional ZnO1−xNx (x ≤ 0.15) via a simple solution combustion method is reported. ZnO1−xNx exhibits visible light absorption, thermal stability, nanometer-/micrometer-sized triangular particles, and catalytic properties. X-ray diffraction studies of ZnO1−xNx demonstrate that the lattice oxygen in ZnO is replaced by nitrogen without any major change in the wurtzite structure; however, charge compensation occurs, because of interstitial Zn atoms, as well as oxygen vacancies. Microscopic studies reveal the dominance of nanometer- and micrometer-sized triangles of ZnO1−xNx. UV−visible and Raman spectra indicate a midgap state, derived from N 2p states, and direct Zn−N interaction, respectively. Secondary ion mass spectrometry studies show the presence of N and ZnN species in the bulk and support the direct Zn−N interaction. Electron paramagnetic resonance (EPR) studies indicate the presence of a small amount of defects. Photocatalytic decomposition of rhodamine B...

H2S gas sensitive indium-doped ZnO thin films: Preparation and characterization

Abstract: High quality indium-doped ZnO (IZO) thin films (∼100 nm) have been deposited onto the glass substrates by using a conventional spray pyrolysis technique. Precursors such as zinc acetate, indium chloride with Brij-35 (polyoxyethylene lauryl ether) as a non-ionic surfactant were used. The morphology, crystal structure, elemental analysis and the gas response properties were investigated by using SEM, TEM, XRD, AFM and XPS techniques. The films show hexagonal wurtzite structure which reveal variations in (1 0 0), (0 0 2) and (1 0 1) intensities with indium doping. The crystallite size calculated by Scherrer formula was in the range of 30–50 nm. The SEM and AFM analysis show 50–70 nm sized grains, while the TEM confirms formation of grains by ∼10 nm sized particles. Their response towards various gases was measured at different operating temperatures and different levels of In-dopants. The 3 at% In-doped ZnO showed response as high as 13,000 for 1000 ppm H 2 S at 250 °C. It exhibited fast response (∼2 s) and recovery time (∼4 min). The gas response strongly depends on the morphology and indium concentration. The high gas response of IZO is explained on the basis of thickness dependent trap state density.

Oxidative kinetic resolution of alcohols using chiral Mn–salen complex immobilized onto ionic liquid modified silica

Abstract: The supported ionic liquid strategy has been applied for the immobilization of chiral Mn(III) salen complex onto ionic liquid modified silica. Chiral Mn(III) salen complex was immobilized over silica through a thin film of covalently anchored imidazolium ionic liquid. These catalysts were characterized by N2 sorption, XRD, FTIR, DRUV–vis, and elemental analysis. The results showed that the chiral Mn(III) salen complex could be successfully immobilized onto the modified mesoporous materials and that the long-range mesoporous ordering of parent supports was maintained after the immobilization. The immobilized catalyst provided good enantioselectivity and activity in the heterogeneous catalysis of the oxidative kinetic resolution of secondary alcohol and can be recovered and recycled for four times without obvious loss of enantioselectivity and activity. Oxidative kinetic resolutions of meso-diols, hydroxyl ester and primary alcohol were also studied using this catalyst system.

A direct method for the preparation of glycolipid–metal nanoparticle conjugates: sophorolipids as reducing and capping agents for the synthesis of water re-dispersible silver nanoparticles and their antibacterial activity

Abstract: The production of a new class of glycolipid–metal nanoparticle conjugates, namely, sophorolipid reduced/capped silver nanoparticles is demonstrated for the first time, by unveiling the reducing and capping abilities of sophorolipid derived from oleic acid. It is also demonstrated that the sophorolipid capped Ag nanoparticles are highly potent antibacterial agents, against both Gram-positive and Gram-negative bacteria. The utilization of sophorolipid brings out several advantages, such as eliminating the necessity for exogenous reducing agent and imparting better stability to the silver nanoparticles as compared to their oleic acid capped analogues. These sophorolipid capped silver nanoparticles can be obtained as a stable powder that can be re-dispersed in water as desired.

Diagnosis and management of the limb girdle muscular dystrophies.

Abstract: Making the diagnosis of a particular type of limb girdle muscular dystrophy (LGMD) can appear challenging. In fact, various clues from the way the patient presents, and the results of simple investigations such as creatine kinase levels, can be extremely helpful in sorting out the various disease entities within this group of patients. The results of more specialised testing of the muscle biopsy and DNA sequencing offer the prospect of a clear answer in around 75% of cases. As more is understood about the clinical features of the different types of LGMD, targeted management is increasingly possible, especially focusing on those patients at high risk of cardiac and respiratory complications.

Establishment and validation of a standard protocol for the detection of minimal residual disease in B lineage childhood acute lymphoblastic leukemia by flow cytometry in a multi-center setting;

Abstract: Minimal residual disease detection, used for clinical management of children with acute lymphoblastic leukemia, can be performed by molecular analysis of antigen-receptor gene rearrangements or by flow cytometric analysis of aberrant immunophenotypes. For flow minimal residual disease to be incorporated into larger national and international trials, a quality assured, standardized method is needed which can be performed in a multi-center setting. We report a four color, flow cytometric protocol established and validated by the UK acute lymphoblastic leukemia Flow minimal residual disease group. Quality assurance testing gave high inter-laboratory agreement with no values differing from a median consensus value by more than one point on a logarithmic scale. Prospective screening of B-ALL patients (n=206) showed the method was applicable to 88.3% of patients. The minimal residual disease in bone marrow aspirates was quantified and compared to molecular data. The combined risk category concordance (minimal residual disease levels above or below 0.01%) was 86% (n=134). Thus, this standardized protocol is highly reproducible between laboratories, sensitive, applicable, and shows good concordance with molecular-based analysis.

Immobilization of phosphotungstic acid (PTA) on imidazole functionalized silica: evidence for the nature of PTA binding by solid state NMR and reaction studies

Abstract: Phosphotungstic acid (PTA) immobilized onto imidazole functionalized fumed silica and was used as an efficient catalyst for epoxidation of a variety of olefins using aqueous H2O2 as an oxidant. Negligible leaching of PTA under the reaction conditions employed indicates a strong interaction between PTA and imidazole. The immobilized catalysts could be separated and reused after the catalytic cycle. Evidence for the heterogenization of PTA on the imidazole functionalized fumed silica has been inferred from different spectroscopic techniques like IR, UV−vis, and NMR. Importantly, the nature of binding of PTA on the support has been studied in detail by solid state NMR spectroscopy using 15N labeled imidazole support. It is clear from the NMR studies that the effective heterogenization of PTA is mainly due to imidazolium ion formation on the support by the acidic protons of PTA and the resultant ion pair.

Sustainable green catalysis by supported metal nanoparticles.

Abstract: The recent progress of sustainable green catalysis by supported metal nanoparticles is described. The template synthesis of metal nanoparticles in ordered porous materials is studied for the rational design of heterogeneous catalysts capable of high activity and selectivity. The application of these materials in green catalytic processes results in a unique activity and selectivity arising from the concerted effect of metal nanoparticles and supports. The high catalytic performances of Pt nanoparticles in mesoporous silica is reported. Supported metal catalysts have also been applied to biomass conversion by heterogeneous catalysis. Additionally, the degradation of cellulose by supported metal catalysts, in which bifunctional catalysis of acid and metal plays the key role for the hydrolysis and reduction of cellulose, is also reported.