Large-scale synthesis of Berlin green Fe[Fe(CN)(6)] microcubic crystals

Berlin green FeFe(CN)(6) microcubic crystals have been successfully prepared by a simple hydrothermal process between K-3[Fe(CN)(6)] with Na2S2O3 aqueous solution, free of any surfactant or template. The experimental results clearly show that the molar ratio of K-3[Fe(CN)(6)] to Na2S2O3 and their concentrations are the dominant processing factors in controlling the size, morphology, and composition of the resulting products.

Dibenzyl trithiocarbonate mediated reversible addition-fragmentation chain transfer polymerization of acrylonitrile

Reversible addition-fragmentation chain transfer polymerization has been successfully applied to polymerize acrylonitrile with dibenzyl trithiocarbonate as the chain-transfer agent. The key to success is ascribed to the improvement of the interchange frequency between dormant and active species through the reduction of the activation energy for the fragmentation of the intermediate. The influence of several experimental parameters, such as the molar ratio of the chain-transfer agent to the initiator [azobis(isobutyronitrile)], the molar ratio of the monomer to the chain-transfer agent, and the monomer concentration, on the polymerization kinetics and the molecular weight as well as the polydispersity has been investigated in detail. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and H-1 NMR analyses have confirmed the chain-end functionality of the resultant polymer.

Precursor induced synthesis of hierarchical nanostructured ZnO

As-synthesized ZnO nanostructures with a bladed bundle-like architecture have been fabricated from a flower-like precursor ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O via a mechanism of dissolution - recrystallization. Experimental conditions, such as initial reactants and reaction time, are examined. The results show that no bladed bundle-like ZnO hierarchical nanostructures can be obtained by using the same molar amount of other zinc salts, such as ZnBr2, instead of the flower-like ZnO (.) 0.33ZnBr(2) (.) 1.74H(2)O precursor, and keeping other conditions unchanged. The products were characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The ZnO nanostructures are mainly composed of nanowires with a diameter around 40 - 50 nm and length up to 1.5 - 2.5 mu m. Meanwhile, ZnO nanoflakes with a thickness of about 4 - 5 nm attached to the surface of ZnO nanowires with a preferred radially aligned orientation. Furthermore, the photoluminescence (PL) measurements exhibited the unique white-light-emitting characteristic of hierarchical ZnO nanostructures. The emission spectra cover the whole visible region from 380 to 700 nm.

A controllable synthesis of multi-armed CdTe nanorods

A simple, productive and low-cost route has been developed to synthesize multi-armed CdTe nanorods using myristic acid (MA) as a complex agent. The yield of this approach can reach 75%. The dimension of the multi-armed nanorods can be controlled by tuning the molar ratios of Cd/Te and Cd/MA; the diameter can be changed from 2 to 7 nm while the length from 15 to 60 nm. The hexagonal structure was confirmed in x-ray diffraction analysis. However, it was assumed that one crystal is composed of the dominant hexagonal structure along with a cubic structure in the core.

Well-organized structures of ZnS semiconductor nanocrystals using amphiphilic triblock copolymer aggregates as templates

Ring- and rod-shaped P4VP-b-PS-b-P4VP ( PS, polystyrene; P4VP, poly( 4-vinylpyridine)) triblock copolymer aggregates are used as templates to synthesize ZnS nanocrystals. Herein, PVP serves as both a stabilizing agent and a structure- directing agent. The resulting ZnS nanocrystals could be aligned along the corona of the copolymer aggregates in near-perfect structures through control of both the molar ratio of Zn2+ to P4VP and the reaction time. The diameter of the as-synthesized ZnS layer on the surface of polymer template is approximate 2 - 3 nm. High-resolution transmission electron microscopy images reveal that the ZnS particles are single crystal in a zinc blende structure. This method provides a simple, reproducible route at room temperature to prepare assembled hybrid polymer - semiconductor nanocrystal nanocomposites.

Self-assembly of cinnamic acid-capped gold nanoparticles

In this work, a new capping agent, cinnamic acid ( CA) was used to synthesize Au nanoparticles (NPs) under ambient conditions. The size of the NPs can be controlled by adjusting the concentration of reductant ( in our experiment sodium borohydride was used) or CA. The CA-stabilized Au NPs can self-assemble into 'nanowire-like' or 'pearl-necklace-like' nanostructures by adjusting the molar ratio of CA to HAuCl4 or by tuning the pH value of the Au colloidal solution. The process of Au NPs self-assembly was investigated by UV - vis spectroscopy and transmission electron microscopy. The results reveal that the induced dipole - dipole interaction is the driving force of Au NP linear assemblies.

Syntheses of chromium(III) complexes with Schiff-base ligands and their catalytic behaviors for ethylene polymerization

A series of chromium(III) complexes LCrCl3 (4a-c) bearing chelating 2,2'-iminodiphenyisulfide ligands [L = (2-ArMeC=NAr)(2)S] was synthesized in good yields from the corresponding ligands and CrCl3.(THF). Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display moderate activities towards ethylene polymerization, and produce highly linear polyethylenes with broad molecular weight distribution. Polymer yields, catalyst activities and the molecular weights, as well as the molecular weight distributions of the polymers can be controlled over a wide range by the variation of the structures of the chromium(III) complexes and the polymerization parameters, such as Al/Cr molar ratio, reaction temperature and ethylene pressure.

Synthesis and characterization of ultrafine CeF3 nanoparticles modified by catanionic surfactant via a reverse micelles route

In this article, we firstly reported on the synthesis and characterization of ultratine CeF3 nanoparticles (NPs) modified by catanionic surfactant via a reverse micelles-based route. The catanionic surfactant PN was prepared by mixing the di(2-ethylhexyl) phosphoric acid (DEHPA) and primary amine (N1923) with 1:1 molar ratio. It exhibited a high surface activity and formed much small reverse micelles in comparison with its individual component (DEHPA or N1923). The PN reverse micelles were then used as templates to prepare ultrafine CeF3 NPs. The narrow distributed nanoparticles have an average diameter 1.8 nm. FTIR spectra indicated that there existed strong chemical interactions between nanoparticles and the adsorbed surfactants. The modification resulted in the FFIR peak position of P=O shifting to lower energy. Due to the effect of modification and small size, the CeF3 NPs showed a remarkable red shift of 54 mn in the fluorescence emission in comparison with that of bulk material and a red shift of 18 nm in contrast with that of the normal CeF3 NPs with an average diameter of 16 nm.

Facile preparation of ZnTiO3 ceramic powders in sodium/potassium chloride melts

A facile molten salt synthesis route was developed to prepare ZnTiO3 ceramic powders with simple oxides ZnO and TiO2 using sodium and potassium chloride eutectic salts as flux. The role of calcination temperature and time and the amount of salt addition to ZnTiO3 formation was investigated by thermogravimetry-differential thermal analysis, X-ray diffraction and Fourier transformation-infrared spectroscopy measurements. Pure hexagonal phase of ZnTiO3 could be obtained from the mixture of the simple oxides and the chlorides (50 mol% KCl, 20 times to oxides in molar ratio) heating at 800 degrees C for 6 h. The scanning electron microscopy images revealed the products were hexagonal sheets of about 1-3 mu m size. Increasing the amount of salt aids in reducing the crystal sizes of final ceramic powders because of diluting the solution.

New double-ceramic-layer thermal barrier coatings based on zirconia-rare earth composite oxides

A series of La2O3-ZrO2-CeO2 composite oxides were synthesized by solid-state reaction. The final product keeps fluorite structure when the molar ratio Ce/Zr >= 0.7/0.3, and below this ratio only mixtures of La2Zr2O7 (pyrochlore) and La2O3-CeO2 (fluorite) exist. Averagely speaking, the increase of CeO2 content gives rise to the increase of thermal expansion coefficient and the reduction of thermal conductivity, but La-2(Zr0.7Ce0.3)(2)O-7 has the lowest sintering ability and the lowest thermal conductivity which could be explained by the theory of phonon scattering. Based on the large thermal expansion coefficient of La2Ce3.25O9.5, the low thermal conductivities and low sintering abilities of La2Zr2O7 and La-2(Zr0.7Ce0.3)(2)O-7, double-ceramic-layer thermal barrier coatings were prepared. The thermal cycling tests indicate that such a design can largely improve the thermal cycling lives of the coatings. Since no single material that has been studied so far satisfies all the requirements for high temperature thermal barrier coatings, double-ceramic-layer coating may be an important development direction of thermal barrier coatings.

Fe(2-EHA)(3)/Al(i-Bu)(3)/hydrogen phosphite catalyst for preparing syndiotactic 1,2-polybutadiene

Polymerizing 1,3-butadiene into syndiotactic 1,2-polybutadiene with art iron(III) catalyst system has been investigated. Activity of the catalyst was affected by the type of cocatalyst alkylaluminum and the phosphorus compound as an electron donor, molar ratio of catalyst components, and their aging sequence and aging time of the catalyst. The microstructure and configuration of the polymer was decided by the catalyst components, the higher [Al]/[Fe] molar ratio tending to yield syndiotactic 1,2-polybutadiene, while the higher [P]/[Fe] molar ratio favors the formation of amorphous 1,2-polybutadiene.

Study on QSPR of alcohols with a novel edge connectivity index F-m

A novel edge degree f(i) for heteroatom and multiple bonds in molecular graph is derived on the basis of the edge degree delta(e(r)). A novel edge connectivity index F-m is introduced. The multiple linear regression by using the edge connectivity index F-m and alcohol-type parameter delta, alcohol-distance parameter L can provide high-quality QSPR models for the normal boiling points (BPs), molar volumes (MVs), molar refraction (MRs), water solubility(log(1/S)) and octanol/water partition (logP) of alcohols with up to 17 non-hydrogen atoms. The results imply that these physical properties may be expressed as a liner combination of the edge connectivity index and alcohol-type parameter, 6, alcohol-distance parameter, L. For the models of the five properties, the correlation coefficient r and the standard errors are 0.9969,3.022; 0.9993, 1.504; 0.9992, 0.446; 0.9924,0.129 and 0.9973,0.123 for BPs, MVs, MRs, log(1/S) and logP, respectively. The cross-validation by using the leave-one-out method demonstrates the models to be highly reliable from the point of view of statistics.

Effects of acetic acid on product selectivity in gas phase oxidative dehydrogenation of cyclohexane

The effect of adding acetic acid on the product distribution in gas phase oxidative dehydrogenation of cyclohexane over alpha(1)-VOPO4 catalyst was investigated. The role of acetic acid in the reaction process was put forward. The proposed mechanism is that acetic acid take precedence of cyclohexane adsorbing on the active sites of alpha(1)-VOPO4 catalyst to form isolated active site. Thus, cyclohexene species can desorb quickly from the active sites, avoiding its deep oxidation dehydrogenation. Almost 100% selectivity to cyclohexene could be obtained when the molar ratio of acetic acid to cyclohexane was 12.9:1 at 450 degrees C, the conversion of cyclohexane was 6.9%.

Detection and characterization of non-covalent complex between lappaconitine and beta-cyclodextrin by electrospray ionization tandem mass spectrometry

The non-covalent complexes between lappaconitine (LA) and beta-cyclodextrin (beta-CD) have been detected and characterized by electrospray ionization combined with ion trap tandem mass spectrometry (ESI-MSn). The experimental results showed that only 1:1 non-covalent complex can be formed in different starting molar ratios of LA to beta-CD. Furthermore, the diagnostic fragmentation of the beta-CD-LA complex, with a significant contribution of covalent fragmentation of LA leaving the N-acetyl anthranoyl (AN) moiety inserted to beta-CD, provided the convincing evidence for the formation of non-covalent complex between LA and beta-CD and the cite of LA molecule included to cavity of beta-CD assigned to AN residue.

One-step synthesis and size control of dendrimer-protected gold nanoparticles: A heat-treatment-based strategy

Dendrimer-protected gold nanoparticles have been facilely obtained by heating an aqueous solution containing third generation poly(propyleneimine) dendrimers and HAuCl4 without the additional step of introducing other reducing agents. Transmission electron microscopy (TEM) and UV vis data indicate the size the nucleation and growth kinetics of gold nanoparticles thus formed which can be tuned by changing the initial molar ratio of dendrimer to gold.