A new route to obtain shape-controlled gold nanoparticles from Au(III)-beta-diketonates

Ligands with a beta-diketone skeleton have been employed for the first time as reductant to produce ligand stabilized gold nanoparticles of different shapes from aqueous HAuCl(4) solution. Evolution of stable gold nanoparticles follows first order (k approximately equal to 10(-2) min(-1)) kinetics with respect to Au(0) concentration. Growth of particles of different shapes (spherical or triangular or hexagonal) goes hand in hand under the influence of different beta-diketones, which have excellent capping and reducing properties. Chlorine insertion was observed to take place in the beta-diketone skeleton.     

Size-selective synthesis and stabilization of gold organosol in C(n)TAC: enhanced molecular fluorescence from gold-bound fluorophores

Gold nanoparticles of variable sizes have been synthesized in toluene employing two-phase (water-toluene) extraction of AuCl4- followed by its reduction with sodium borohydride in the presence of a series of cationic surfactants of a homologous series having the general formula C(n)TAC. The solubility features of the gold particles in the organic solvent have been accounted qualitatively by calculating the van der Waals interaction potential between the particles. The effect of thermal energy and medium dielectric constant on the stability of metal particles has been studied by measuring the surface plasmon resonance. The stabilization of surfactant-mediated gold particles as hydrosol or organosol has been elucidated by considering the double-layer interaction as a function of the dielectric constant of the solvent medium. The influence of the counterion of the phase transfer reagent and stabilizing ligand on the photochemical stability of the gold colloids has been investigated. The fluorescence probe 1-methylaminopyrene (MAP) was considered for the surface functionalization of the gold particles, and it has been found that there is an enhancement of molecular fluorescence from the gold-probe assembly.     

Solution phase evolution of AuSe nanoalloys in Triton X-100 under UV-photoactivation

A solution phase UV-irradiation technique has been exploited to produce an AuSe nanoalloy through fusion of preformed Au (photoproduced) and Se (chemically prepared) in a micellar (TX-100) medium.     

Monoclinic CuO nanoflowers on resin support: recyclable catalyst to obtain perylene compound

Monoclinic CuO crystallite in grams has been obtained from resin bound Cu(II)-1,10-phenanthroline complex, R(-)[Cu(1,10-phen)(2)](2+) that becomes a recyclable catalyst for oxidative phenol coupling (OPC) reaction. Thus an exclusively intuitive blue fluorescing perylene derivative is derived from colorless 2,7-dihydroxynaphthalene (2,7-DHN) in high yield.     

Fabrication of Large‐Scale Hierarchical ZnO Hollow Spheroids for Hydrophobicity and Photocatalysis

We report here the preparation of a crystalline, pure hexagonal phase of ZnO as hollow 500–800 nm spheroids in the presence of organic bases, such as pyridine, using zinc acetate as the precursor salt. The spheroids exhibit unique 3D hierarchical architectures, like cocoons, and demonstrate improved superhydrophobic (water contact angle, 150°) character due to the inherited air‐trapped capillarity within the cocoon structure. The simple synthetic strategy used in this process is modified hydrothermolysis (MHT), which represents a general approach and may contribute to the formation mechanism of the hollow nanostructures with highly improved porosity. Depending on the concentration of the precursor salt, it has been possible to cover glass plates or the inner wall of a reaction vessel with ZnO nanocrystals. A low salt concentration (<0.01 M ) allows the easy preparation of a superhydrophobic glass surface, whereas a high salt concentration (>0.01 M ) results in the precipitation of cocoons at the bottom of the reaction vessel as a solid mass together with a deposited thin film of ZnO nanocrystals covering the inner wall of the glass vessel. The thickness of the film successively grows through repetitive hydrothermolysis processes for which a low salt concentration (<0.01 M ) was employed. Because of the hollow cocoonlike morphology, the surface area of the film is greatly increased, which makes it accessible for functionalization by incoming substrates from both sides (internally and externally) and helps to drive a competent photocatalytic dye degradation pathway. The heterocyclic base pyridine exclusively develops cocoons. Thus, the mechanism of self‐aggregation of ZnO nanocrystals under MHT reaction conditions has been studied and the characterization of the compounds has been supported with physical measurements.     

An approximate analysis of the interaction between two tearing modes of the same helicity

The interaction between tearing modes with the mode numbersm=1,n=1 andm=2,n=2 is investigated for different initial amplitudes of the modes, using a single helicity approximation, a step-current profile and a time-independent resistivity. Also included are the results on the temporal behaviour of the amplitude of the uncoupled modem=2,n=2 in the situation with identical equilibrium parameters as ours.     

Controlled interparticle spacing for surface-modified gold nanoparticle aggregates

Aggregation of gold nanoparticles of increasing size has been studied as a consequence of adsorption of 2-aminothiophenol (ATP) on gold nanoparticle surfaces. The capping property of ATP in the acidic pH range has been accounted from UV-vis absorption spectroscopy and surface-enhanced Raman scattering (SERS) studies. The effect of nanoparticle size (8-55 nm) on the nature of aggregation as well as the variation in the optical response due to variable degree of interparticle coupling effects among the gold particles have been critically examined. Various techniques such as transmission electron microscopy, X-ray diffraction, zeta-potential, and average particle size measurement were undertaken to characterize the nanoparticle aggregates. The aggregate size, interparticle distances, and absorption band wavelengths were found to be highly dependent on the pH of the medium and the concentration of the capping agent, ATP. The acquired SERS spectra of ATP relate the interparticle spacing. It has been observed that the SERS signal intensities are different for different sized gold nanoparticles.     

Gram level synthesis of lead-free solder in the nanometer length scale obtained from tin and silver compounds using silicone oil

A straightforward route to gram level synthesis of a pure phase of the Sn-Ag nanoalloy in an eutectic composition (Sn/Ag 96.5:3.5) in silicone oil is reported. The composition, morphology, and microstructure of the alloy were fully characterized. In a mixture of ethylene glycol and silicone oil, direct reduction of Sn(II) acetate and Ag(I) nitrate gave the Sn-Ag nanoalloy. The nanoalloy disintegrates by sonication and reforms by heating, leading to smaller particles with a melting point as low as 128 degrees C.     

Diiminic Schiff Bases: An Intriguing Class of Compounds for a Copper‐Nanoparticle‐Induced Fluorescence Study

The condensation products of salicylaldehyde and different diamines constitute an important class of diiminic Schiff bases (DSBs). This class of compounds has been rediscovered as reducing as well as capping agents under UV irradiation. UV irradiation of alkaline DSB solutions in the presence of water‐soluble copper salts has been employed to produce copper nanoparticles (CuNPs). Intriguing CuNP‐stimulated fluorescence behavior of the solution has been observed. Depending upon the nature of the spacer in between two iminic bonds, fluorescence enhancement or quenching is observed. Such surprising fluorescence contrast has been ascribed to far‐field radiation and lossy surface waves.     

Photo-induced decolorization of dimethylmethylene blue with selenious acid: a novel method to examine selective monomer-dimer distribution of the dye in micelle

In this report, selenious acid (H2SeO3) has been exploited to study the decolorization of a cationic dye, dimethylmethylene blue (DMMB) with UV-light. Micelles have effectively been employed as organized media to promote the rate of decolorization of the dye molecules. Micellar catalysis has been explained as a consequence of electrostatic, hydrophobic and charge transfer interactions. It has also been shown that strong charge transfer and electrostatic interaction lead to an appreciable enhancement of the reaction rate in micelle, whereas, weak hydrophobic interaction is of marginal importance. Existence of monomer-dimer equilibrium for the dye molecules under certain selective environments has been identified spectrophotometrically. Then the shift of dimer-monomer equilibrium of the dye has been successfully studied in aqueous and micellar environments exploiting photodecolorization process for the dye in solution. 'Salting-in' and 'salting-out' agents were introduced into the reaction mixture to examine the viability of the dye decolorization process for dye contaminated water samples.