Synthesis,growth of single crystals and their characterization: l-Alaninium maleate (LAM)

In recent days amino acid single crystals are gaining importance due to good optical behavior. The title compound consists of l-alanine; an amino acid and maleic acid; an aromatic organic compound. It has been successfully synthesized and the single crystal has been grown by slow evaporation solution growth. The grown single crystal has been characterized by powder X-ray diffraction (PXRD) analysis and FTIR measurements. The crystalline perfection was examined by high-resolution X-ray diffraction (HRXRD) technique and found that the specimen quality is quite good. Optical behavior has been assessed by UV–Vis analysis and found that there is no absorption in the entire visible region. The relative second harmonic generation (SHG) efficiency measurement reveals that the incorporation of maleic acid to l-alanine leads to increase its value of SHG. The mechanical behavior and the thermal analysis have been carried out using Vickers microhardness and TG/DTA measurements respectively. Its hyperpolarizability was estimated by density functional theory (DFT).     

Lie group analysis for the effect of temperature-dependent fluid viscosity and thermophoresis particle deposition on free convective heat and mass transfer under variable stream conditions

This paper examines a steady two-dimensional flow of incompressible fluid over a vertical stretching sheet. The fluid viscosity is assumed to vary as a linear function of temperature. A scaling group of transformations is applied to the governing equa- tions. The system remains invariant due to some relations among the transformation parameters. After finding three absolute invariants, a third-order ordinary differential equation corresponding to the momentum equation and two second-order ordinary differential equations corresponding to energy and diffusion equations are derived. The equations along with the boundary conditions are solved numerically. It is found that the decrease in the temperature-dependent fluid viscosity makes the velocity decrease with the increasing distance of the stretching sheet. At a particular point of the sheet, the fluid velocity decreases but the temperature increases with the decreasing viscosity. The impact of the thermophoresis particle deposition plays an important role in the concentration boundary layer. The obtained results are presented graphically and discussed.     

Crystallization of benzimidazole by solution growth method and its characterization

The potential organic NLO crystal of benzimidazole (BMZ) has been successfully grown by slow evaporation solution growth technique at room temperature. The crystalline perfection has been verified by High resolution X‐ray diffraction (HRXRD) analysis. The very low angle boundary obtained for this solution‐grown specimen may be attributed to the segregation of solvent molecules (methanol), which were entrapped within the crystal during growth. The laser damage threshold has been measured by using high intensity Q‐switched Nd:YAG laser. The observed value is greater than that of KDP and lesser than that of melt grown benzimidazole. The NLO efficiency has been determined and it is compared with the KDP crystal. The thermal behaviour has been assessed by TG/DTA analysis. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Etching and dielectric studies on L‐lysine monohydrochloride dihydrate single crystal

The nonlinear optical single crystals of L‐Lysine monohydrochloride dihydrate (L‐LMHCl) have been grown and examined by High‐resolution X‐ray diffraction and etching studies for their perfection. The vibrational frequencies have been identified by the micro‐Raman studies and the dielectric behaviour has been studied and the results are presented in detail. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and characterization of 4,4′‐dihydroxy‐α‐methylstilbene crystal

4,4′‐dihydroxy‐α‐methylstilbene (DHAMS) was synthesized by condensation reaction with chloroacetone and phenol in the presence of concentrated sulfuric acid, and has been successfully grown by solution growth technique. This is the first report in the literature on the crystallization of DHAMS and exhibited the birefringent melt (liquid crystal property) of the optical properties. FTIR and FTNMR studies are in accordance with the structure. Good quality crystals were grown by slow evaporation technique by acetone as solvent. A transmission spectrum of the crystal was obtained in the region of 285 nm. The structural and optical properties were studied. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Investigations on the growth,optical behaviour and factor group of an NLO crystal: L‐alanine alaninium nitrate

Amino acid family crystals exhibit excellent nonlinear and electro‐optical properties. L‐alanine alaninium nitrate (LAAN) single crystal belonging to the amino acid group was grown by slow cooling solution growth technique. The High resolution X‐ray diffraction (HRXRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, UV‐Vis., Photoluminescence (PL) and Factor group analyses were carried out. The factor group analysis reveals 183 internal vibrations for the title compound. The second harmonic generation property was tested by Kurtz‐Perry powder technique. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal growth,dielectric and FIR reflectivity studies on PZN(0.91)‐PT(0.09) single crystals

Crystal growth of PZN‐PT single crystals using slow cooling flux technique with PbO flux is reported in this communication. Optimum growth conditions to maximize the amount of perovskite are also suggested. The grown crystals are characterized by dielectric and FIR spectroscopy. Temperature dependence of ε′ very close to the transition temperature shows a first order phase transition. Diffused phase transition and strong frequency dependence of ε′ around transition temperature are also observed. The real part of ε′ was found to obey the relation ε′ – ε_∞ = χ′(T‐T_o)². Dispersion in the ferroelectric phase is suggested to originate from ordering of domains. Competition in the B‐site occupancy by Zn, Nb and Ti ions is suggested to be the origin for the additional modes in the FIR reflectivity at room temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Recent study of nanomaterials prepared by inert gas condensation using ultra high vacuum chamber

The ultra high vacuum chamber was developed in the Department of Nuclear Physics, University of Madras with the funding from DST, India. This UHV chamber is used to prepare nanocrystalline materials by inert gas condensation technique (IGCT). Nanocrystalline materials such as PbF₂, Mn²⁺-doped PbF₂, Sn-doped In₂O₃ (ITO), ZnO, Al₂O₃, Ag₂O, CdO, CuO, ZnSe:ZnO etc., were prepared by this technique and characterized. Results of some of these materials will be presented in this paper. In solid-state²⁰⁷Pb NMR on PbF₂ a separate signal due to the presence of grain boundary has been observed. The structural phase transition pressure during the phase transformation from the cubic phase to orthorhombic phase under high pressure shows an increase with the decrease in grain size. Presence of electronic centres in nanocrystalline PbF₂ is observed from Raman studies and the same has been confirmed by photoluminescence studies. Al₂O₃ was prepared and⁵⁶Fe ions were implanted. After implantation segregation of⁵⁶Fe ions was examined by SEM. The oxidation properties of ITO were studied by HRTEM. As against the expectation of oxide coating on individual nanograins of In-Sn alloy, ITO nanograins grew into faceted nanograins on heat treatment in air and O₂ atmosphere. The growth of ITO under O₂ atmosphere showed pentagon symmetry. The PMN was initially prepared by solid-state reaction. Further, this PMN relaxor material will be used to convert into nanocrystalline PMN by IGCT with sputtering and will be studied     

Antioxidant,Anti-Bacterial,and Congo Red Dye Degradation Activity of AgxO-Decorated Mustard Oil-Derived rGO Nanocomposites

Scaling up the production of functional reduced graphene oxide (rGO) and its composites requires the use of low-cost, simple, and sustainable synthesis methods, and renewable feedstocks. In this study, silver oxide-decorated rGO (Ag_xO−rGO) composites were prepared by open-air combustion of mustard oil, essential oil-containing cooking oil commercially produced from the seeds of Brassica juncea. Silver oxide (Ag_xO) nanoparticles (NPs) were synthesized using Coleus aromaticus leaf extract as a reducing agent. Formation of mustard seed rGO and Ag_xO NPs was confirmed by UV-visible characteristic peaks at 258 nm and 444 nm, respectively. rGO had a flake-like morphology and a crystalline structure, with Raman spectra showing clear D and G bands with an I_D/I_G ratio of 0.992, confirming the fewer defects in the as-prepared mustard oil-derived rGO (M−rGO). The rGO-Ag_xO composite showed a degradation efficiency of 81.9% with a rate constant k⁻¹ of 0.9506 min⁻¹ for the sodium salt of benzidinediazo-bis-1-naphthylamine-4-sulfonic acid (known as the azo dye Congo Red) in an aqueous solution under visible light irradiation. The composite also showed some antimicrobial activity against Klebsilla pneomoniae, Escherichia coli, and Staphylococcus aureus bacterial cells, with inhibition zones of ~15, 18, and 14 mm, respectively, for a concentration of 300 µg/mL. At 600 µg/mL concentration, the composite also showed moderate scavenging activity for 2,2-diphenyl-1-picrylhydrazyl of ~30.6%, with significantly lower activities measured for Ag_xO (at ~18.1%) and rGO (~8%) when compared to control.     

Nanostructured metal particlemodified electrodes for electrocatalytic and sensor applications

Nanotechnology has become one of the most exciting frontier fields in analytical chemistry. The huge interest in nanomaterials, for example in chemical sensors and catalysis, is driven by their many desirable properties. Although metal is a poor catalyst in bulk form, nanometre-sized particles can exhibit excellent catalytic activity due to their relative high surface area-to-volume ratio and their interface-dominated properties, which significantly differ from those of the bulk material. The integration of metal nanoparticles into thin film of permselective membrane is particularly important for various applications, for example in biological sensing and in electrocatalysis. We have already established different techniques to design permselective membrane-coated chemically modified electrodes with incorporated redox molecules for electrocatalytic, electrochromic and sensor applications. Recently, we have prepared nanostructured platinum and copper (represented M_nano, M = Pt and Cu) modified GC/Nafion electrodes (GC/Nf/M_nano) and characterized by using AFM, XPS, XRD and electrochemical techniques. The nanostructured M_nano modified electrodes were utilized for efficient electrocatalytic selective oxidation of neurotransmitter molecules in the presence of interfering species such as ascorbic acid (AA) and uric acid (UA). It has been also shown that the modified electrodes could be used as sensors for the detection of submicromolar concentrations of biomolecules with practical applications to real samples such as blood plasma and dopamine hydrochloride injection solution. The GC/Cu_nano electrode has been used for catalytic reduction of oxygen.