Studies on the Zetapotential of Calcite/p-Sulfonato-calix[4,8]arenes

Zeta potential of calixarenes has been reported for the first time. The water-soluble calixarenes has been used as dispersion media in solid/liquid interface. p-sulfonato-calix[4]arene (PSC4) and p-sulfonato-calix[8]arene (PSC8) were synthesized and characterized by FTIR, NMR, mass spectrometry, and HPLC techniques. It was proved that the zeta potential is a fast and simple measurement to know the adsorption behavior of sufonato calixarnes on calcite. The chemisorption of p-sulfonato-calix[n]arene was confirmed by shift in iso electric point, adsorption studies and FTIR. The calculated free energy of adsorption value and its sign suggests the chemical interaction between the calcite surface and p-sulfonato calix[4]and[8]arene.     

Glucosamine-functionalized silver glyconanoparticles: characterization and antibacterial activity

We report the analytical and in vitro antibacterial activity of glucosamine-functionalized silver glyconanoparticles. Morphological characterization ensured the surface topography and particle size distribution of both silver and glucosamine–silver nanoparticles. Surface plasmon resonance of both types of nanoparticle was determined from UV–visible spectroscopy using four different sample concentrations (10–40 μL). The resulting functionalized glyconanoparticles show maximum absorbance with a red shift of 30 ± 5 nm (390–400 nm) from their initial absorbance (425–430 nm). FT-Raman and ¹H-NMR spectroscopic measurement confirmed the surface functionalization of glucosamine on the silver surface through the carbonyl group of a secondary amide linkage (–NH–CO–), elucidated by the conjugation of N-hydroxysuccinimide (NHS)-terminated silver nanoparticles and the amino group of glucosamine. Antimicrobial experiments with well-characterized silver nanoparticles (AgNPs) and glucosamine-functionalized silver nanoparticles (GlcN-AgNPs) demonstrate that GlcN-AgNPs have similar and enhanced minimum inhibitory concentration (MIC) against eight gram-negative and eight gram-positive bacteria compared with AgNPs. MIC data shows that Klebsiella pneumoniae (ATCC 700603) and Bacillus cereus isolate express high levels of inhibition, with the quantity and magnitude of inhibition being higher in the presence of GlcN-AgNPs.     

Initial stage of the adsorption of fluorofullerene molecules on Si surface

Spatially resolved images of an individual C₆₀F₁₈ fluorofullerene molecule on Si(100) − 2 × 1 surface have been obtained using scanning tunneling microscopy. Scanning tunneling microscopy results and ab initio calculations show that the fluorofullerene molecules interact with the Si(100) − 2 × 1 surface with F atoms pointing down towards the surface. The adsorption energy of a C₆₀F₁₈ molecule on Si(100) − 2 × 1 surface is ∼12.1 eV, which is much higher than the adsorption energy of the same molecule on Si(111) − 7 × 7 surface (6.65 eV). C₆₀F₁₈ molecules are located in the troughs in-between the dimer rows occupying the four-dimer site on Si(100) − 2 × 1 surface.     

Studies on optical absorption and structural properties of Fe doped CdS quantum dots

Fe doped CdS quantum dots have been prepared using simple precursors by chemical precipitation technique. Fe doped CdS quantum dots have been synthesized by mixing cadmium nitrate, sodium sulfide and adding Fe under suitable conditions. X-ray diffraction analysis reveals that undoped and Fe doped CdS crystallizes in hexagonal structure. The lattice constants of Fe doped CdS nanoparticles decreased slightly with incorporation of Fe and no secondary phase was observed. The average grain size of the nanoparticles is found to lie in the range of 2.8–4.2 nm. HRTEM results show that undoped and 3.75% Fe doped CdS nanoparticles exhibit a uniform size distribution and average size of the nanoparticles is about 2–3 nm. Raman spectra show that 1LO and 2LO peaks of the Fe doped CdS samples are slightly red shifted compared with those of undoped CdS. Optical absorption spectra of Fe doped CdS nanoparticles exhibited red shift.     

Synthesis,characterization, and heterogeneous catalysis of polymer‐supported poly(propyleneimine) dendrimer stabilized gold nanoparticle catalyst

We report here, the synthesis of two types of heterogeneous nanoparticle catalysts viz., polymer‐supported poly(propyleneimine)‐G2 dendrimer stabilized gold nanoparticle catalysts using crosslinked poly(4‐vinylpyridine) matrix (PSP4VP) as support material. The grafting of dendrimer on the surface of P4VP beads was characterized by FTIR spectrophotometer and CHN analyses. The immobilization of AuNPs was characterized by UV‐Vis spectrum, SEM, and HRTEM studies. The resultant polymer‐supported dendrimer stabilized AuNPs were used as a heterogeneous catalyst for the reduction of 4‐nitrophenol. The catalytic activity is found to be excellent and it can also be reused many times by simple filtration and activity remains maintained. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2525–2532, 2010     

Syntheses and structures of square-pyramidal acetonitrile coordinated copper(II) complexes with N-(aroyl)-N′-(5-nitrosalicylidene)hydrazines

The syntheses and structures of two square-pyramidal acetonitrile coordinated copper(II) complexes, [Cu(HbhsNO₂)(CH₃CN)₂]ClO₄ (1) and [Cu(HahsNO₂)(CH₃CN)(ClO₄)] (2), are described. The mononegative ligands are obtained by deprotonation of the phenolic-OH of N-(benzoyl)-N-(5-nitrosalicylidene)hydrazine (H₂bhsNO₂) and of N-(anisoyl)-N-(5-nitrosalicylidene)hydrazine (H₂ahsNO₂). Crystal data for 1: monoclinic, P2₁/c (#14), a = 9.7245(14), b = 20.23(4), c = 11.042(3) Å, = 91.86(2)°, V = 2171.0(7) ų, and Z = 4 and for 2: triclinic, P1¯ (#2), a = 9.7710(19), b = 9.9687(15), c = 11.062(5) Å, = 73.10(3), = 88.77(3), = 88.379(14)°, V = 1030.4(5) ų, and Z = 2. In each complex the planar ligand binds the metal ion via phenolate-O, imine-N, and amide-O. The nitrogen of an acetonitrile molecule satisfies the fourth site of the square-plane containing the metal ion. In 1 the axial coordination is provided by the nitrogen of a second acetonitrile molecule, whereas in 2 one of the oxygen atoms of the perchlorate occupies the fifth axial site. The axial acetonitrile molecule of 1 is bound to the metal center in a bent mode. The other noticeable difference between the two structures is in the geometry at the metal center. A large displacement (0.23 Å) of the metal ion from the ONON basal plane towards the axial coordinating atom is observed in 1. On the other hand, there is no displacement of the metal center from the same ONON basal plane in 2. The EPR and electronic spectral features in acetonitrile solutions are consistent with the solid state structures.     

What does pressure decide to cook with orientationally disordered plastic phase of cubane: an orientational glass or crystal?

The effect of pressure on the structure and reorientational motion of molecules in orientationally disordered (OD) crystalline phase of cubane has been investigated in detail using variable shape molecular simulations in constant-pressure constant-temperature ensemble. Complete orientational ordering occurs at a pressure of 1.0 GPa and the OD phase transforms to an orientationally ordered phase at this pressure. The transition is associated with a kink in the variation of structural parameters such as cell parameters, unit-cell volume, and interaction energy. This transition is also associated with an anomaly in specific heat. Above this transition pressure, the structural quantities display only smaller changes with further increase in pressure. The structure of high-pressure orientationally ordered (HPOO) phase has been characterized using radial distribution functions and orientational distribution function. From detailed analysis of the structure of HPOO phase we conclude that it is isostructural with low-temperature orientationally ordered phase. The OD phase has four times larger compressibility than the HPOO phase.