Growth, optical, mechanical and dielectric studies on NLO active pure and metal ion doped single crystals of bis-thiourea zinc chloride

Good quality single crystals of pure and metal ion (Ni²⁺) doped bis-thiourea zinc chloride (BTZC) possessing excellent nonlinear optical properties have been grown from aqueous solution by the slow solvent evaporation technique. The lattice parameters of the grown crystals are determined by single crystal X-ray analysis. The well defined sharp peaks in the powder X-ray diffraction pattern reveals the crystalline perfection and the EDAX spectrum confirms the presence of dopant in the lattice of the parent crystal. The DRS UV-visible spectral study reveals improved transparency for the doped crystal, ascertaining the inclusion of metal ion in the lattice. The optical band gap of the pure and doped crystals was calculated to be 4.8 and 5.2 eV respectively from the UV transmission spectrum. The vickers hardness test brings forth higher hardness value for Ni²⁺doped BTZC as compared to pure BTZC crystal. The dielectric measurement exhibits very low dielectric constant and dielectric loss at higher frequencies for both the pure and Ni²⁺doped BTZC. The existence of second harmonic generation signals in the crystal also has been confirmed by performing the Kurtz powder test.     

Mechanism of Evolution of Koneramine Complexes from One‐Pot Reactions: Snapshots of Intermediates Offer Facile Routes to New Dipicolylamines

Koneramines (L^ROR′, R=Ph or Ts; R′=Me, iPr) and their complexes were found to emerge from the system of pyridine‐2‐carboxaldehyde and N‐phenyl/tosylethylenediamine when a primary or secondary alcohol was used as solvent. Imidazolidinylpyridines (L^R, R=Ph or Ts) became major emergents whereas hemi‐aminals (L^ROH, R=Ph or Ts) are minor emergents of the system when tertiary butanol was used as the solvent; the bulky tertiary butyl group prevented the addition of alcohol to the iminium ion that diverted the equilibrium towards imidazolidinylpyridines. By playing with the components of the reaction mixture, crystals of the metastable intermediates bound to copper(II) and/or zinc(II) were obtained and the structures were determined by X‐ray diffraction analysis. The reported results shed light on how to control the emergents of the multicomponent reaction mixture that forms koneramines. Reactivity studies of the intermediates pave the way for a new type of koneramine complexes that are new dipicolylamines where the two pyridine moieties of the resulting koneramine are not the same.     

Studies on the synthesis and characterization of Zn1− x Cd x S and Zn1− x Cd x S:Mn2+ semiconductor quantum dots

Quantum dots (3–4?nm) of Zn_{1? x} Cd _x S (both free of Mn²⁺ and with Mn²⁺ incorporated) were synthesized through a novel solvothermal-microwave irradiation technique. Detailed structural analysis of the Zn_{1? x} Cd _x S and Zn_{1? x} Cd _x S:Mn²⁺ (x?=?0, 0.25, 0.5, 0.75 and 1) materials was carried out using powder X-ray diffraction technique. For all the compositions, the crystallite size was controlled to less than 1.5?nm. The optical energy gap for Zn_{1? x} Cd _x S was found to vary from 3.878 to 2.519?eV and for Zn_1?x Cd _x S:Mn²⁺ it varies from 3.830 to 2.442?eV when x is increased from 0 to 1. Overall, the optical energy gap could be tuned from a minimum of 2.442?eV to a maximum of 3.878?eV. DC conductivity analysis (from 40°C to 150°C) and electrical energy gap analysis for all the compositions were also performed. The dc conductivity for Zn_{1? x} Cd _x S solid solutions varies from 0.3840?×?10^?10 to 8.7782?×?10^?10?mho/m at 150°C and for Zn_{1? x} Cd _x S:Mn²⁺ it varies from 0.5751?×?10^?10 to 9.8078?×?10^?10 mho /m at 150°C (for x?=?0 to x?=?1). The method of synthesis and the results observed in this investigation may assist in the fabrication of optical devices when the required operational performance falls under the range observed in the study.     

Spatiotemporal binary interaction and designer quasi-particle condensates

We introduce a new integrable model to investigate the dynamics of two component quasi-particle condensates with spatiotemporal interaction strengths. We derive the associated Lax pair of the coupled Gross-Pitaevskii （GP） equation and construct matter wave solitons, We show that the spatiotemporal binary interaction strengths not only facilitate the stabilization of the condensates, but also enables one to fabricate condensates with desirable densities, geometries, and properties, leading to the so-called ＂designer quasi-particle condensates＂.     

Impact of zinc substitution on the structural and magnetic properties of chemically derived nanosized manganese zinc mixed ferrites

Mn_1−xZn_xFe₂O₄ nanoparticles (x=0-1) were synthesized by wet chemical co-precipitation techniques. X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy were effectively utilized to investigate the different structural parameters. The elemental analysis was conducted using energy-dispersive spectrum and inductively coupled plasma analysis. The magnetic properties such as magnetization and coercivity were measured using vibrating sample magnetometer. The observed magnetization values of the nanoparticles were found to be lower compared to the bulk counterpart. The magnetization showed a gradual decrease with zinc substitution except for a small increase from x=0.2 to 0.3. The Curie temperature was found to be enhanced in the case of ferrites in the nanoregime. The variation in lattice constant, reduced magnetization values, variation of magnetization with zinc substitution, the presence of a net magnetic moment for the zinc ferrite and the enhancement in Curie temperature in Mn_1−xZn_xFe₂O₄ all provide evidence to the existence of a metastable cation distribution together with possible surface effects at the nanoregime.     

Thermal decomposition mechanism of synthesized copper octoate

Present study describes the synthesis and characterization of copper octoate. Attenuated total reflectance–Fourier transformation infra red (ATR–FTIR) and energy dispersive X-ray (EDX) spectrometric techniques have been used for the characterization of the synthesized compound. The surface morphology of the compound has been studied using scanning electron microscopy (SEM). Thermal behavior and decomposition mechanism of copper octoate has been explained on the basis of simultaneous thermo-gravimetry–differential thermal analysis–evolved gas analysis (TG–DTA–EGA) and high temperature X-ray diffraction (HTXRD) measurements. Copper octoate is stable up to 250 °C. The decomposition process consists of two overlapping steps. A plausible decomposition mechanism is proposed and details of the studies carried out are being discussed here.     

Ultrasound‐Assisted Pechmann Condensation of Phenols With β‐Ketoesters to Form Coumarins,in the Presence of Bismuth(III) Chloride Catalyst

Ultrasound was found to synergistically accelerate the condensation of phenol with β‐ketoesters in the presence of BiCl₃. In the absence of ultrasound, under the same conditions, the reaction was found to be slow. Thus, the reaction can be carried out in the presence of ultrasound at room temperature (28–30°C), with a considerable reduction of reaction time, with high yield and high purity of coumarins.     

Investigations on temperature dependent structural evolution of NaPO3 glass

The understanding of molecular level structural information of phosphate glasses is very much essential. The unique microwave-absorbing ability of NaH₂PO₄·2H₂O was found to be very useful for preparing crystal and glassy sodium super ionic conductors (Nasicon's) as a component of batch mixtures. In this work NaPO₃ glass was prepared by both conventional melt quench and microwave heating from NaH₂PO₄·2H₂O as a starting material. The structure of NaPO₃ glass and their structural evolution upon heating through glass transition were probed by combination of complementary techniques like differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) and thermo-Raman spectroscopy.This revised version was published online in November 2005 with corrections to the Cover Date.