Noncommutative Dirac oscillator in an external magnetic field

We show that (2+1)$(2+1)$-dimensional noncommutative Dirac oscillator in an external magnetic field is mapped onto the same but with reduced angular frequency in absence of magnetic field. We construct the relativistic Landau levels by solving corresponding Dirac equation in (2+1)$(2+1)$-dimensional noncommutative phase space. All the Landau levels become independent of noncommutative parameter for a critical value of the magnetic field. Several other interesting features along with the relevance of such models in the study of atomic transitions in a radiation field have been discussed.     

Tuning of phonon anharmonicity in pyrochlore titanates: temperature‐dependent Raman studies of Sm2Ti2‐xZrxO7 (x=0, 1/2, 3/4, and 2) and stuffed spin‐ice Ho2 + xTi2 − xO7 − x/2 (x=0, 1/3, and 2/3)

Anomalous temperature dependence of Raman phonon wavenumbers attributed to phonon–phonon anharmonic interactions has been studied in two different families of pyrochlore titanates. We bring out the role of the ionic size of titanium and the inherent vacancies of pyrochlore in these anomalies by studying the effect of replacement of Ti^{4 +} by Zr^{4 +} in Sm₂Ti₂O₇ and by stuffing Ho^{3 +} in place of Ti^{4 +} in Ho₂Ti₂O₇ with appropriate oxygen stoichiometry. Our results show that an increase in the concentration of the larger ion, i.e. Zr^{4 +} or Ho^{3 +}, reduces the phonon anomalies, thus implying a decrease in the phonon–phonon anharmonic interactions. In addition, we find signatures of coupling between a phonon and crystal field transition in Sm₂Ti₂O₇, manifested as an unusual increase in the phonon intensity with increasing temperature. Copyright © 2011 John Wiley & Sons, Ltd.     

Electroluminescence from hybrid organic–inorganic LEDs based on thermally evaporated CdS thin films

Hybrid organic–inorganic light emitting devices combine the color purity and durability of inorganic light emitting diodes (LEDs) with high efficiency, flexibility and low processing cost of organic LEDs (OLEDs). A significant challenge is to incorporate inorganic nanocrystals inside the OLED structure. In the present work, thin films of CdS were successfully incorporated inside standard OLED structure using vacuum thermal evaporation technique. For the characterization of these films, they were deposited on plain glass plates at room temperature and studied using structural (XRD and TEM), morphological (SEM and AFM) and optical (UV and PL) techniques. The films were found to be composed of nanocrystals of CdS in which the size of the crystals increased with the increase in film thickness. The hybrid organic–inorganic LEDs showed improved luminance and efficiency as compared to the organic LED without CdS layers.     

Processing of high density polyethylene and poly(ethylene terephthalate) blends

Commercial grades of high density polyethylene, HDPE and waste poly(ethylene terephthalate), PET were melt blended over a wide range of compositions. Effect of ethylene acrylic acid copolymer, EAA, ethylene vinyl acetate copolymer, EVA and maleic anhydride grafted EVA as compatibilizers on rheology and mechanical properties of the blend was studied. EAA was found most suitable compatibilizer.     

Thermonanalytical Investigations of Monochlorobis (2,4-Pentanedionato) Vanadium(IV) Aryloxides

The thermal decomposition of the complexes [Vcl (acac)₂(OAr)] (where acac=2,4-pentanedionato anion; OAr=–OC₆H₄O-M-4, OC₆H₄OBut-4) has been studied using non-isothermal techniques (DTA and TG). The TGA indicate that the substitution of chlorine in VCl₂(acac)₂ with aryloxide ligands results in an increase in the initial temperature of decomposition (IDT) of the new complexes. The role of the substituent at the aryloxide ring on the thermal stability of the complexes is depicted and hence described. The ultimate decomposition product in all the complexes has been identified as V₂O₅. The kinetic and thermodynamic parameters namely, the energy of activation E, the frequency factor A, entropy of activation S and specific reaction rate constant k _r etc. have been rationalized in relation to the bonding aspect of the aryloxide ligands. This revised version was published online in July 2006 with corrections to the Cover Date.     

The synthesis and antitumor activity of metal complexes of amine–carboxyborane adducts

The amine carboxyborane metal complexes, tetrakis - μ - (trimethylamine – boranecarbo - xylato)acetonitrile dicopper(II) and bis-μ- (morpholine–boranecarboxylato)zinc(II) dihydrate demonstrated cytotoxic activity against human Tmolt₃, HeLa-S³ and MB-9812 cell growth.Tetrakis-μ-(trimethylamine–boranecarboxylato)-acetonitrile dicopper(II) and bis - μ - (morpholine – boranecarboxylato)zinc (II) dihydrate inhibited L₁₂₁₀ DNA, RNA and protein syntheses, with greatest inhibitory effects on DNA synthesis. The reduction in DNA synthesis correlates well with inhibition of de novopurine synthesis and the key enzymes involved in this pathway, i.e. IMP dehydrogenase and PRPP amido transferase. These compounds were also observed to induce DNA strand scission but did not appear to intercalate between base pairs of DNA, alkylate bases or cause cross-linking of the strands of DNA. Tetrakis-μ-(trimethylamine – boranecarboxylato)acetonitrile dicopper(II) also demonstrated the ability to inhibit L₁₂₁₀ DNA topoisomerase II activity. © 1998 John Wiley & Sons, Ltd.     

Water Induced Alterations in Self-Assembly of a Bio-Surfactant in Deep Eutectic Solvent for Enhanced Enzyme Activity

Deep eutectic solvents (DESs) meet important requirements for green solvent technology, including non-toxicity, biodegradability, sustainability, and affordability. Despite possessing low cohesive energy density than water, DESs have been found to support the self-assembly of amphiphiles. It is very much pertinent to examine the effect of water on self-assembly of surfactants in DESs as the presence of water alters the inherent structure of DES, which is expected to affect the characteristic properties of self-assembly. Following this, we have investigated the self-assembly of amino-acid based surfactant, Sodium N-lauroyl sarcosinate (SLS), in DES-water mixtures (10, 30 and 50 w/w% of water) and explored the catalytic activity of Cytochrome-c (Cyt-c) in the formed colloidal systems. Investigations using surface tension, fluorescence, dynamic light scattering (DLS), and isothermal titration calorimetry (ITC) have shown that DES-water mixtures promote the aggregation of SLS, resulting in the lower critical aggregation concentration (cac ∼1.5–6-fold) of the surfactant as compared to water. The nanoclustering of DES at low water content and it's complete de-structuring at high water content affects the self-assembly in a contrasting manner governed by different set of interactions. Further, Cyt-c dispersed in DES-water colloidal solutions demonstrated 5-fold higher peroxidase activity than that observed in phosphate buffer.     

A Luminescent Zinc(II) Coordination Polymer for Selective Detection of Fe3+ and Cr2O72− in Water and Catalytic CO2 Fixation

Fluorescence-based detection technique using coordination polymer has been considered an attractive alternative over conventional approaches. Herein, a new luminescent zinc(II) coordination polymer, [Zn(4-ABPT)(NIPA)(H₂O)], SSICG-5 , is synthesized by using a Lewis acidic Zn(II) ion, aromatic nitro group containing ligand 5-nitroisophthalic acid (H₂NIPA), and basic −NH₂ rich ligand 3,5-di(pyridine-4-yl)-4H-1,2,4-triazol-4-amine (4-ABPT). SSICG-5 can detect Fe³⁺ and Cr₂O₇²⁻ selectively with a LOD of 0.16 μM and 1.94 μM, respectively. Additionally, carbon dioxide (CO₂) fixation via one-pot CO₂ cycloaddition reaction has significant importance for reduced waste formation, minimizing reaction time and lowering chemical usage. Zn metal centre of SSICG-5 possesses a replaceable coordinated water molecule. The active metal sites combined with the Lewis acidic and basic sites of the ligands make SSICG-5 an ideal bifunctional heterogeneous catalyst for efficient CO₂ cycloaddition reaction under room temperature (RT), solvent-free conditions. Notably, SSICG-5 exhibits near quantitative conversion (turnover number (TON) of 198) of propylene oxide to its carbonate compound under mild reaction conditions.