Inverse Hall–Petch effect in nanostructured ZnS

Vickers microhardness of compacted nanoparticles of ZnS of average grain sizes 3–12 nm was studied for different compaction pressures. The hardness was found to increase rapidly with load for smaller values of the load and then to become practically independent of load. The microhardness was found to increase with increase in grain size showing inverse Hall–Petch relation in the present study.     

Electronic Structure of Nanostructured Nickel Oxide Using Ni 2p XPS Analysis

We examine the electronic structure of nanostructured nickel oxide with an average particle size of 4–5nm using Ni 2p X-ray photoelectron spectrum. The most striking features of the spectrum are the Ni 2p main line broadening and an increase in the relative intensity of the 1.5eV satellite. We explain the observations as due to an enhancement in the non-local screening process on the basis of Ni₇O₃₆ cluster model by taking into account the large surface area to volume ratio and high Ni²⁺ vacancy concentration in nanostructured nickel oxide. The important contribution of an enhanced Ni 3d–O 2p hybridization and the origin of shake-up peaks above the 7eV satellite is also discussed. The study underlines the importance of factors such as the actual local environment of the core hole site, defect density and distribution, possible structural transitions, etc. in determining the Ni 2p core level X-ray photoelectron spectrum of nanostructured nickel oxide and shows that the actual synthesis routes and the thermal history greatly influence the electronic structure of nanostructured nickel oxide.     

Dopant concentration dependent magnetism of Cu-doped TiO2 nanocrystals

Journal of Nanoparticle Research - Mannosylation is a method commonly used to deliver nanomaterials to specific organs and tissues via cellular macrophage uptake. In this work, for the first time,...     

Acoustic non-linearity parameter B/A and related molecular properties of binary organic liquid mixtures

Acoustic non-linearity parameter B/A is calculated for binary mixtures using four different methods. The interactions in the liquid mixtures are explained on the basis of excess non-linearity parameter and excess adiabatic compressibility. Sehgal's relations for calculating molecular properties of pure liquids are extended to binary mixtures.     

Microhardness studies of nanocrystalline calcium tungstate

Nanocrystals of calcium tungstate (CaWO₄) of three different grain sizes were synthesized through chemical precipitation technique and the grain sizes and crystal structure were determined using the broadening of X‐ray diffraction patterns and transmission electron microscopy. The microhardness of compacted pellets of nanocrystalline calcium tungstate (CaWO₄) with different grain sizes were measured using a Vickers microhardness tester for various applied loads ranging from 0.049 N to 1.96 N. The values of microhardness showed significant reverse indentation size effect at low indentation loads. The microhardness data obtained for samples of different grain sizes showed grain size dependent strengthening obeying normal Hall‐Petch relation. The dependence of compacting pressure and annealing temperature on microhardness of the nanostructured sample with grain size of 13 nm were also studied. The samples showed significant increase in microhardness as the compacting pressure and annealing time were increased. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Simultaneous determination of titanium and molybdenum in steel samples using derivative spectrophotometry in neutral micellar medium

A simple, selective and sensitive spectrophotometric method has been developed for the individual and simultaneous determination of Ti(IV) and Mo(VI) using resacetophenone p-hydroxybenzoylhydrazone (RAPHBH) in presence of Triton X-100, without any prior separation. Beer's law is obeyed between 0.13-1.2 microg mL-1 and 0.18-1.90 microg mL-1 concentration of Ti(IV) and Mo(VI) at 455 nm and 405 nm, respectively. The molar absorptivity and Sandell's sensitivity of the coloured complexes at pH 3.0 are 3.1x10(4) L mol-1 cm-1, 4.2x10(4) L mol-1 cm-1, and 1.6 ng cm-2, 2.3 ng cm-2 for Ti(IV) and Mo(VI), respectively. The stoichiometry of the complexes were found to be 1:2 and 1:1 (metal:ligand) for Ti(IV) and Mo(VI), respectively. These metal ions interfere with the determination of each other in zero-order spectrophotometry. The first derivative spectra of these complexes permitted a simultaneous determination of Ti(IV) and Mo(VI) at zero crossing wavelengths of 500.0 nm and 455.0 nm, respectively. The effect of foreign ions in the determination of Ti(IV) and Mo(VI) were investigated. The proposed method has been successfully applied for the determination of titanium and molybdenum in standard alloy steel, mineral and soil samples.     

The solvation of Cu2+ with gas-phase clusters of water and ammonia

A detailed study has been undertaken of the gas-phase chemistry of [Cu(H2O)N]2+ and [Cu(NH3)N]2+ complexes. Ion intensity distributions and fragmentation pathways (unimolecular and collision-induced) have been recorded for both complexes out as far as N=20. Unimolecular fragmentation is dominated by Coulomb explosion (separation into two single charged units) on the part of the smaller ions, but switches to neutral molecule loss for N>7. In contrast, collisional activation promotes extensive electron capture from the collision gas, with the appearance of particular singly charged fragment ions being sensitive to the size and composition of the precursor. The results show clear evidence of the unit [Cu(X)8]2+ being of special significance, and it is proposed that the hydrogen-bonded structure associated with this ion is responsible for stabilizing the dipositive charge on Cu2+ in aqueous solution.     

Fourier transform infrared spectroscopy study of nanostructured nickel oxide

Nanostructured nickel oxide having different average particle sizes ranging from 3 to 16 nm were synthesized and Fourier transform infrared (FTIR) spectra of the samples were recorded in the far infrared (IR) region. The spectra were found to be dominated by surface mode absorptions with no distinct absorption corresponding to the bulk transverse optical mode. IR absorption coefficient, alpha, for the nanostructured NiO samples were calculated as a function of frequency using a macroscopic approach devised by Fuchs. The effects of crystalline geometry, numerical values of optical constants, filling factor and increased damping on the spectral features of the samples were analyzed. Though the simulations approximately reproduced the occurrence of a shoulder in the experimental spectra, the most intense peak in the simulated spectra was found to be about 50 cm(-1) above the corresponding experimentally observed peak. It was shown that the experimentally observed absorption maximum of all the samples were in close agreement with that determined using a microscopic theory based on the rigid ion model. The weak absorption peaks in the frequency region 60-100 cm(-1) appearing in the spectra of all the samples were identified as surface induced transverse acoustical modes, omegaTA, which became IR active due to the breakdown of translational symmetry in the nanocrystallites.     

Characterization of chemically synthesized CdS nanoparticles

II-VI semiconductor nanoparticles are presently of great interest for their practical applications such as zero-dimensional quantum confined materials and for their applications in optoelectronics and photonics. The optical properties get modified dramatically due to the confinement of charge carriers within the nanoparticles. Similar to the effects of charge carriers on optical properties, confinement of optical and acoustic phonons leads to interesting changes in the phonon spectra. In the present work, we have synthesized nanoparticles of CdS using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The UV-visible absorption, photoluminescence and Raman spectra of the sample are recorded and discussed briefly     

Towards Advances in Molecular Understanding of Boric Acid Biocatalyzed Ring-Opening (Co)Polymerization of δ-Valerolactone in the Presence of Ethylene Glycol as an Initiator

Following our previous studies on the molecular level structure of (co)oligoesters obtained via anionic homo- and co-polymerization of novel β-substituted β-lactones, prepared by the atmospheric pressure carbonylation reaction of respective epoxides, the boric acid biocatalyzed ring-opening (co)polymerization of δ-valerolactone has been studied. As a co-monomer the 6-methy-ε-caprolactone, prepared by the one-pot oxidation of respective alcohol, and ethylene glycol as polymerization initiator were used. The obtained copolymers were characterized by ¹H-NMR, GPC and ESI-MS, respectively in order to confirm their chemical structures and identity. Subsequently, tandem mass spectrometry (MS-MS studies) via collision-induced dissociation were utilized to characterize the fragmentation pattern. ESI-MS and NMR analyses confirmed the formation of random linear copolymer chains composed of different polyester repeat units. MS-MS experiments showed that fragmentation proceeds via ester bound cleavage along the (co)polyester chains. The innovative aspect of this contribution is related to the elaboration of the telechelic (co)polymers end-capped with hydroxyl end groups and well-defined molecular architectures, which could facilitate the development of new flexible macromolecular systems for potential biomedical applications.