Lanka Satyanarayana

N-Alkylation of amines with alcohols over nanosized zeolite beta

Direct N-alkylation of amines with alcohols was successfully performed by using nanosized zeolite beta, which showed the highest catalytic activity among other conventional zeolites. This method has several advantages, such as eco-friendliness, moderate to high yields, and simple work-up procedure. The catalyst was successfully recovered and reused without significant loss of activity and only water is produced as co-product. In addition, imines were also efficiently prepared from the tandem reactions of amines with 2-, 3- and 4-nitrobenzyl alcohols using nanosized zeolite beta.

Luminescence and high temperature ferromagnetism in YAlO nanophosphors: materials for efficient next generation LEDs and spintronic applications

Current research on environment friendly and efficient luminescent materials for white LEDs, envisaged as next generation energy efficient lighting devices, has spurred research into the different forms of yttrium-aluminum-oxide (YAlO) (YAG: garnet structured YAlO and YAM: monoclinic structured YAlO), including the discovery of a new phase of tetragonal structured YAlO named YAT. Appropriate luminescence in the visible-yellow region has been realized by doping rare earth (Ce) in the YAlO host. Interestingly, this work indicates that all the studied YAlO nanophosphors (NPs) exhibit dilute ferromagnetism up to 600 K. The observed magnetic character of YAlO NPs is attributed to the oxygen vacancies and remains unperturbed even after Ce doping, thereby establishing the independent nature of the two phenomena. This non-interfering luminescence and magnetic character of the YAlO NPs is anticipated to have a wide application potential in high temperature spintronics, LEDs and other biological applications.

Oxidative coupling of 2-naphthol to (R)/(S)-BINOL by MCM-41 supported Mn-chiral Schiff base complexes

Three Mn(III)-chiral Schiff base complexes supported on MCM-41 are found to be effective reusable catalysts for enantioselective oxidation of 2-naphthol to (R)- and (S)-BINOL (1,1′ bi-2-naphthol) in the presence of oxygen. The supported Mn(III)-complexes are characterized by PXRD, FTIR, solid state-NMR, BET, and cyclic voltammetry study. The homo-coupling reaction with oxygen as the oxidant is promoted by 20 mg of Mn(III) Schiff base complexes to afford binaphthols in nearly quantitative yields with high enantioselectivity of up to 91% ee. The catalytic activities of the homogeneous and heterogeneous chiral catalyst are found to be almost similar. However, the heterogeneous counterparts are found to be advantageous in terms of recyclability and storability. Oxygen partial pressure, the nature of the solvent, temperature and the amount of catalyst affect the catalytic oxidation process. High temperature and highly polar solvent are found to have adverse effects on the catalytic oxidation process.

4.3.5 One-pot Hydrothermal Synthesis of SnO and SnO2 Nanostructures: Enhanced H2 Sensing Attributed to in-situ p-n Junctions

Herein, we present a novel hydrothermal synthetic approach for the formation of SnO/SnO2 nanorods and their assembly into micro cubes as an effective gas sensing material. The synthesized materials were characterized by powder x-ray diffraction, Micro-Raman, FT-IR, XPS, and thermogravimetry. Morphological evaluations by SEM revealed the rods of about 10 nm and cube about 6 um. Electrical characterization results attribute the enhanced hydrogen gas sensing response to the formation of SnO2/SnO local p-n junctions. Significantly improved sensor response and sensitivity could be achieved using Pd functionalization. Further, the anomalous room temperature ferromagnetic behavior of the as synthesized materials and its consequence on the enhanced sensing property is discussed.

Structural, magnetic and magnetocaloric properties of sputtered Gd films

Gd films with different thicknesses varying from 100 nm to 750 nm have been deposited on single crystal Si (100) substrate by ultra high vacuum magnetron sputtering system. X-ray diffraction analysis reveals the crystalline nature and hcp crystal structure of the films. Microstructure investigations have been carried to study the surface morphology of the films. Thermo magnetic studies confirm the magnetic transition of the films and are ∼275 K, close to bulk. Magnetocaloric effect (MCE) has been studied from magnetic isotherms measured around magnetic transition and the maximum isothermal entropy change of 2.0 J/kg-K is achieved for a magnetic field change of 2 T for the 750 nm film. The sputtered Gd films are useful for micro cooling device applications.