Electrodeposition of nano-sized nuclei of magnetic Co–Ni alloys onto n-Si (1 0 0)

Nanometer-sized nuclei of Co–Ni alloys were electrodeposited onto n-Si (1 0 0) electrodes from buffered solutions of the metallic ions. The energy levels of the interface Si/(Co(II),Ni(II))_aq were determined from Mott–Schottky plots. Electrodeposition of the alloys occurs by an anomalous mechanism and preferential deposition of Co took place at all the Co(II)/Ni(II) ratios investigated. The morphology and magnetic properties of the nuclei were studied by AFM and MFM, respectively. It is showed that nuclei of height <30 nm and low aspect ratio present a single-domain magnetic behaviour. Larger nuclei depict complex magnetic characteristics, with a progressive built-up of multi-domains.     

Synthesis of Ag_2S nano-sized clusters and their chemical sensitizations in AgCl cubic and {100} tabular microcrystal imaging systems

1 Introduction Since the 1990s, silver chloride {100} tabular grain emulsion has attracted much attention from research-ers working in different enterprises all over the world, such as Eastman Kodak[1―5], Agfa-Gavaert[6,7] and the Lucky Group Company in …     

Interaction of an antituberculosis drug with nano-sized cationic micelle: Förster resonance energy transfer from dansyl to rifampicin in the microenvironment

In this contribution, we report studies on the interaction of an antituberculosis drug rifampicin (RF) in a macromolecular assembly of CTAB with an extrinsic fluorescent probe, dansyl chloride (DC). The absorption spectrum of the drug RF has been employed to study Förster resonance energy transfer (FRET) from DC, bound to the CTAB micelle using picosecond resolved fluorescence spectroscopy. We have applied a kinetic model developed by Tachiya to understand the kinetics of energy transfer and the distribution of acceptor (RF) molecules around the donor (DC) molecules in the micellar surface with increasing quencher concentration. The mean number of RF molecules associated with the micelle increases from 0.24 at 20 μm RF concentration to 1.5 at 190 μm RF concentration and consequently the quenching rate constant (k_q) due to the acceptor (RF) molecules increases from 0.23 to 0.75 ns^?1 at 20 and 190 μm RF concentration, respectively. However, the mean number of the quencher molecule and the quenching rate constant does not change significantly beyond a certain RF concentration (150 μm ), which is consistent with the results obtained from time resolved FRET analysis. Moreover, we have explored the diffusion controlled FRET between DC and RF, using microfluidics setup, which reveals that the reaction pathway follows one‐step process.     

Synthesis of an aluminum nitride–yttria (AlN–Y2O3) composite from nano-sized porous AlN and YCl3

In order to enhance the thermal conductivity of aluminum nitride (AlN) with sintering additives including yttria (Y₂O₃), it is necessary to form yttrium aluminate garnet (YAG) and secondary phases both within and around the boundaries of AIN drains. Nano-sized porous AlN particles were produced to form YAG and secondary phases within AlN grains, after which a AlN–Y₂O₃ nano–nano composite was formed from AlN and amorphous Y₂O₃. Porous AlN powders were first successfully synthesized by the chemical vapor synthesis (CVS) method. Highly crystalline and nano-sized porous AlN powders were synthesized at 1,200 °C. Brunauer–Emmett–Teller (BET) analysis showed that these powders had very large surface areas, suggesting that the particles approached nano-scale sizes with very small pores. To form composites of Y₂O₃ and AlN, we prepared a yttrium source solution that infiltrated the nano-sized pores of the AlN particles. Such an infiltration of AlN with amorphous Y₂O₃ was expected to effectively reduce the residual oxygen content by facilitating the formation of YAG and secondary phases during the sintering process. We characterized the composite powders of AlN–Y₂O₃ and the sintered bodies using BET, XRD, SEM, TEM, and thermal conductivity analyses.

     

Distorted colloidal crystal of similar-sized aggregates (1.5 μm in diameter) of nano-sized diamond particles (4 nm in diameter)

Distorted colloidal crystal suspension of similar-sized aggregates of diamonds (1.5 μm in diameter) was obtained by the deionization of aqueous suspension of the pre-particles of diamond, 4 nm in diameter. The stability, characteristics, and the rigidity of the crystal-like suspensions were studied. The main cause for the formation of the similar-sized aggregates is deduced to be the cooperation between the van de Waals inter-particle attraction and the repulsion induced by the vigorous thermal motion of the pre-particles. The rigidity was evaluated from the microscopic observation in the sedimentation equilibrium. Fluctuation parameters of the distorted colloidal crystals estimated from the rigidities were between 0.03 and 0.06, which are quite similar to those of typical colloidal crystals and solids of hard spheres.     

Preparation and characterization of nanocomposite ZnO–Ag thin film containing nano-sized Ag particles: influence of preheating,annealing temperature and silver content on characteristics

Nanocomposite ZnO–Ag thin film containing nano-sized Ag particles have been grown on glass substrate by spin-coating technique using zinc acetate dihydrate as starting precursor in 2-propanol as solvent and monoethanolamine as stabilizer. Silver nanoparticles were added in the ZnO sol using silver nitrate dissolved in ethanol-acetonitrile. Their structural, electrical, crystalline size and optical properties were investigated as a function of preheating, annealing temperature and silver content. The results indicated that the crystalline phase was increased with increase of annealing temperature up to 550 °C at optimum preheating temperature of 275 °C. Thermal gravimetric differential thermal analysis results indicated that the decomposition of pure ZnO and nanocomposite ZnO–Ag precursors occurred at 225 and 234 °C, respectively with formation of ZnO wurtzite crystals. The scanning electron microscopy and atomic force microscopy revealed that the surface structure (the porosity and grain size) of the ZnO–Ag thin film (the film thickness is about 379 nm) was changed compared to pure ZnO thin film. The result of transmission electron microscopy showed that Ag particles were about 5 nm and ZnO particles 58 nm with uniform silver nanoclusters. Optical absorption results indicated that optical absorption of ZnO–Ag thin films decreased with increase of annealing temperature. Nanocomposite ZnO–Ag thin films with [Ag] = 0.068 M and [Ag] = 0.110 M showed an intense absorption band, whose maximum signals appear at 430 nm which is not present in pure ZnO thin films. The result of X-ray photoelectron spectroscopy revealed that the binding energy of Ag 3d_5/2 for ZnO–Ag shifts remarkably to the lower binding energy compared to the pure metallic Ag due to the interaction between Ag and ZnO.     

Drying dissipative structure of similar sized aggregates (1.5 μm in diameter) of nano-sized diamond particles (4 nm in diameter)

Macroscopic and microscopic drying patterns were observed on a cover glass, a watch glass, and a Petri glass dish during the course of dryness of aqueous suspensions of similar sized aggregates of diamonds (CD1), which formed from the deionization of the pre-particles of diamond 4 nm in diameter. Two kinds of macroscopic patterns, i.e., outer and inner broad rings, and spoke lines were formed. Cooperative drying processes of the convection, sedimentation, and solidification were clarified. Microscopic drying patterns showing the formation of very large dendritic aggregates from the CD1 particles were observed only when the excess amount of sodium chloride higher than 2 mM coexisted in the initial suspensions before dryness and further initial CD1 concentration is lower than 0.17 wt%.     

Synthesis and characterization of some acetoxime-modified hetero-metal alkoxide precursors of zinc(II) and aluminum(III) for sol–gel transformation to nano-sized ZnAl2O4

Reactions of [ZnAl₂(OPr_i)₈] [A] with acetoxime in different molar ratios in refluxing anhydrous benzene, yield complexes of the type [ZnAl₂(OPrⁱ)_8?n{(CH₃)₂CNO}_n] {where, n = 1–4}. All the complexes are transparent viscous/foamy solids. They were characterized by elemental analyses, FT-IR and NMR (¹H, ¹³C {¹H}) spectral studies. ²⁷Al NMR spectrum of [ZnAl₂(OPrⁱ)₄{(CH₃)₂CNO}₄] [4] in CDCl₃ suggests presence of four coordination around both the aluminum atoms. IR spectra suggest that the oximato ligands bind the aluminum atoms in a side on manner in all the complexes. The ESI-mass spectrum of the representative derivative [4] suggests its monomeric nature while the thermo-gravimetric curve shows its low thermal stability. Sol–gel transformations of the precursors (A), (1), and (4) yielded nano-sized ZnAl₂O₄ samples (a), (b) and (c) at ~500 °C, respectively. The XRD patterns of (a), (b) and (c) indicate formation of cubic phase nano-sized zinc aluminate in all the samples. Surface morphologies of these samples were investigated by SEM images. IR spectra as well as EDX analyses indicate formation of pure zinc aluminate in all the cases. TEM image of sample (c) shows spherical (~5–8 nm) morphology.     

The synthesis of nano-sized undoped,Bi doped and Bi,Cu co-doped SrTiO3 using two sol–gel methods to enhance the photocatalytic performance for the degradation of dibutyl phthalate under visible light

Two sol–gel methods (the citric acid gel and the Pechini methods) were used for the preparation of nano-sized undoped, Bi-doped and Bi, Cu co-doped SrTiO₃ samples to optimize their properties for the photocatalytic degradation of dibutyl phthalate. The perovskite-like phase was detected for the samples prepared by the citric acid gel method after calcination at 800 °C for 3 h, while in the case of the Pechini method; it was detected after calcination at 800 °C for 9 h. The particle size of the samples prepared by the citric acid gel method is greater than that of the samples prepared by the Pechini method. Cu doping in both methods increased the particle size. Cu doping, Bi doping and Bi, Cu co-doping in both methods shifted the absorption edge to the visible light range as well. The band gap of Bi, Cu co-doped SrTiO₃ is smaller than that of Bi doped SrTiO₃, which in turn is smaller than that of undoped SrTiO₃. The highest removal of the total organic carbon (TOC) of DBP was obtained using a Bi, Cu co-doped SrTiO₃ sample prepared by the citric acid gel method. TOC removal of DBP followed pseudo-first order kinetics.