Search

Hexagonal lattices of two-dimensional (2D) DNA arrays were prepared via two kinds of three-point-star motifs on the basis of Watson- Crick complementarity. We studied the influence of different molar ratio of single-stranded DNA on the structure of three-point-star motif and the influence of different annealing temperature on the self-assembly of 2D arrays with gel electrophoresis and atomic force microscopy (AFM). The results showed that the structure of three-point-star motifs is more stable when the molar ratio of three single-stranded DNA is 1:3:3, corresponding to the stoichiometry of the assembly ratio. The 2D arrays are integrated better when the annealing temperature is 50℃. The height of the array is 2 nm; and the length of hexagonal side is 20 nm. The mechanism of three-point-star motif self-assembly to 2D arrays was suggested.

We prepared Fe3O4 nanoparticles using chemical coprecipitation and studied the factors affecting the magnetic characteristics of nano-Fe3O4 particles. We identified four factors and three levels of an orthogonal experiment and investigated these four factors that affect the magnetic characteristics of the Fe3O4 particles. We obtained important information from this investigation. The Fe3+ to Fe2+ molar ratio, the iron precursor salt, the amount of surfactant and the amount of alkali were found to be important. We also studied the influence of the order of alkali and surfactant addition, the aging time and the stirring speed on the magnetic characteristics of the nano-Fe3O4 particles. The Fe3O4 preparation process was also analyzed.

Vanadium oxide nanotubes (VOx-NTs) have been synthesized by using n-butylamine as structure-directing template and V2O5 as precursor under hydrothermal conditions. XRD, FTIR, SEM, TEM, BET and TG-DTA characterizations have been performed to both optimize the synthetic conditions and understand the growth mechanism of VOx-NTs. The results showed that open-ended VOx-NTs were obtained under the optimized conditions (hydrothermal temperature: 150–160°C, hydrothermal time: 5–7 d, the molar ratio of V2O5 to n-butylamine is 1:1) with diameters ranging from about 30 to 100 nm and several micrometers in length. The BET surface area and the desorption cumulative pore volume of pores of the as-synthesized sample were about 27.4609 m2/g and 0.191087 cm3/g, respectively. The result presents that the synthesis of VOx-NTs is controlled by the “rolling” mechanism and temperature is primary driving force for rolling.

Flowerlike, spherical and cubic PbS nanoparticles have been successfully synthesized by refluxing cysteine and lead nitrate in an alkaline solution. The influences of the cysteine to Pb2+ molar ratio, the pH value of the reaction mixture as well as the refluxing time on the shape of PbS nanoparticles were investigated. Detailed experimental results demonstrated that a higher molar ratio of cysteine to Pb2+ (5.2:1) and shorter refluxing time favor the formation of flowerlike PbS nanoparticles at pH 9.0. While lower pH value (8.0) favors the formation of spherical PbS nanoparticles, and higher pH value (10.0), however, favors the formation of cubic PbS nanoparticles. The mechanism for the shape control of PbS nanoparticles is discussed.

Cage-like octa(trimethylsiloxy)silsesquioxane [ (Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)4 with aqueous tetramethylammonium hydroxide in equal molar ratio. Elementary analysis, FT-IR,1H,13C,29Si NMR are used to characterize these silsesquioxanes.

The permeation properties ofn-butane,i-butane andn-butane/i-butane mixture (n-butane 24.3% (molar ratio),i-butane 75.7%) through a tubular silicalite-1 zeolite membrane were studied at 298 and 473 K respectively. The permselectivities ofn-butane andi-butane under pressure difference of 0.06 MPa at 298 and 473 K were 16.3 and 7.4 respectively. The separation factors ofn-butane/i-butane mixture were between 2.0 and 2.5 at 298 and 473 K. At 298 K, the permeances ofn-butane in the mixture were lower than those of single component while the permeances ofi-butane in the mixture were almost the same as those of single component. At 473 K, the permeances ofn-butane andi-butane in the mxiture were decreased compared with those of the single component, and the permeance ofn-butane decreased more rapidly than that ofi-butane.

Cp2Yb·2THF reacts with CpNa in 1:1 molar ratio in THF at 40°C for 2 h, and the in situ generated anionic divalent complex NaYbCp3(THF)n reacts further with an excess of CpH at 40°C for 48 h, after work-up, affording the trivalent anionic ytterbium complex [Na(THF)2(μ2-η5-Cp) (η5,η5,η1-Cp3Yb)(THF)]n (1) by oxidation reaction of Cp2Yb with CpH. Crystal structure determination reveals that complex 1 has one-dimension polymeric chains of distinct Na(THF)2(μ2-η5 -Cp)(η5, η5, η1-Cp3Yb)(THF) units, which were formed by the coordination of the bridging Cp ligand with Cp3Yb·THF and Na(THF)2 in η5,η5 mode via self-assembly.