Adsorption of ionic surfactants on polar surfaces with a low content of chemically adsorbed alkyl chains

Colloidal silica and titanium dioxide were surface-modified by chemisorption of octadecyl dimethylmethoxy silane. The surface density of these alkyl silane groups was adjusted to less than 7% of the available surface hydroxyls, leaving the adsorbents hydrophilic and electrically charged in aqueous solution.Ionic surfactants (tetradecylpyridinium chloride and sodium lauryl sulfate) are adsorbed onto the surface-modified silica and titanium dioxide from aqueous solution, even in the case where the surface of the adsorbents exhibits the same sign of electrical charge as the surfactant ionic head groups. According to the adsorption model of Gu the chemiadsorbed alkyl chains are supposed to serve as anchors for small surface aggregates of the ionic surfactants.     

Synthesis and X-ray crystal structure of oxamido-bridged heterobinuclear Ni(Ⅱ)-Cu(Ⅱ) complexes

The two complexes [Ni(oxen)Cu(L)2](ClO4)2.xH2O (L=2,2'-bipyridyl(bpy), 1,10-phenanthroline(phen)) have been synthesized, where oxen is N,N'-bis(2-aminoethyl)oxamido di-anion. The crystal structure of [Ni(oxen)Cu(bpy)2](ClO4)2.CH3OH has been determined by X-ray diffraction method. The crystal is triclinic system, space group P1 with a=12.179(1),b=12.298(2), c=11.476(2) A, a=97.57(1), B=97.52(1), 7=80.29(2), V=1669.04(67) A3, Z=2, Dcalcd=1.667 g/cm3. The structure has been refined to final R of 0.076 and Rw of 0.080, respectively. The complexes have an extended oxamido-bridged structure and consist of Ni(Ⅱ) ion in a square planar environment and Cu(Ⅱ) ion in a distorted octahedral environment.     

Characteristic features of intra- and intermolecular interactions in crystals of pyrrole-2-carbaldehyde isonicotinoylhydrazone and its hydrate

Pyrrole-2-carbaldehyde isonicotinoylhydrazone (1) and its hydrate [1·H₂O] (2) were studied by single-crystal X-ray diffraction analysis. The introduction of the pyrrole substituent into N"-substituted isonicotinic hydrazide (INH) causes the intramolecular redistribution of the electron density compared to those in INHs studied earlier, which increases the basicity of the hydrazone nitrogen atom (N") involved in intermolecular hydrogen bonding. This effect has not been observed in the structures of N"-substituted INHs and benzhydrazides studied previously. Intermolecular hydrogen bonds play a decisive role in the formation of the crystal structures of 1 and 2.     

Preparation and Characteristics of Porous Silica Films by a Modified Base-Catalyzed Sol-Gel Process Containing PVA: II. Film Preparation

Porous SiO₂ films were successfully deposited on silicon substrates by a modified base-catalyzed Sol-Gel process (MBCP) containing polyvinyl alcohol (PVA). The process conditions, such as the gelation time, the synthesis temperature, the stabilizing agent of the precursor solution and the spin coating speed, the heat-treatment, the annealing temperature of the film on the microstructure and porosity of porous SiO₂ films were systematically investigated by SEM, XRD and ellipsometry techniques. This study provides a novel preparation technique for the porous SiO₂ film. Using this process, the resultant film can reach a thickness of 3.6 m for one layer, a porosity of 25–50%, a low thermal conductivity of 0.11 W/m·K. This film will be used as a low dielectric layer, an thermal-insulating layer and a low refractive index layer.     

Racemization of chiral amino alcohols III: Effect of Mg or Ca addition on the activity and stability of the Co/γ-Al2O3 catalyst

The racemization of R-(-)-2-amino-1-butanol in a reaction using Co/γ-Al₂O₃ catalysts and catalysts modified by Mg or Ca was investigated in this paper. Complete racemization was achieved with a yield of over 83% at using the Mg modified Co/γ-Al₂O₃ catalyst under optimized reaction conditions of 170°C and 2.5 MPa of H₂. The catalysts were thoroughly characterized by XRD, XPS, TPR, SEM and TEM. The addition of Mg and Ca may be advantageous for dispersing and stabilizing the active species of the Co/γ-Al₂O₃ catalyst, protecting from sintering, significantly improving its catalytic activity and stability.     

Synthesis of some sulfur-containing pyrido[1,2-α]pyrimidines

4-Methylthiopyrido[1,2-α]pyrimidin-2-one and 2-hydroxypyrido[1,2-α]pyrimidine-4-thione derivatives were synthesized by the addition ofN-(4-R-pyrid-2-yl)acetoacetamides (R = H, Me) to CS₂ under phase-transfer conditions followed by the alkylation of the reaction products with Mel. The molecular structure of 3-acetyl-4-methylthiopyrido[1,2-α]pyrimidin-2-one is established by X-ray analysis.     

Photochemical degradation of hyaluronic acid by singlet oxygen

Changes of the rheological properties of hyaluronic acid (sodium-magnesium salt) solutions after exposure to UV radiation indicate a vigorous decrease in their viscosity, but its still strong shear rate dependence. Whereas the presence of the singlet oxygen sensitizer (anthracene-1-sulphonic acid) brings about a loss of shear dependence; the studied solutions show newtonian behavior.     

An Efficient Method for the Synthesis of Acyl-diazenes Using NaNO_2/NaHSO_4·H_2O

Azo compounds are widely utilized as analytic reagents and dyes1, they can also be used in material of non-linear optics, material of optics information storing in laser disks, and dyes with oil solubility in photochromy in modern technology2. Recently, many noteworthy studies have shown that some azo compounds possess excellent optical memory and photoelectric properties3,4. For example, polymer scaffolds bearing azobenzene-potential are useful for optical information storage, azo-dye doped…     

Fractionation and purification of antioxidant peptides from Chinese sturgeon (Acipenser sinensis) protein hydrolysates prepared using papain and alcalase 2.4L

Protein hydrolysates have the potential to be natural and safer sources of bioactive peptides. In this study, two proteases were used to hydrolyze Chinese sturgeon (Acipenser sinensis) protein, and the hydrolysates were then purified to yield antioxidant peptides. The degree of hydrolysis of 23.56 % and 18.14 % was obtained using papain and alcalase 2.4L, respectivly, and hydrolysates had 96.80 % and 87.24 % total amino acid content, respectivly. The papain hydrolysate (PH) and alcalase 2.4L hydrolysate (AH) showed good antioxidant activity against DPPH^? (IC₅₀ of 3.64 and 3.15 mg/mL) and ABTS^?+ (IC₅₀ of 1.92 and 1.58 mg/mL), respectively. The low-molecular-weight (<1000 Da) fraction of both hydrolysates demonstrated the highest antiradical activity (IC₅₀ of 2.59 and 2.31 mg/mL, DPPH) and (IC₅₀ of 1.54 and 1.36 mg/mL, ABTS), respectively. Nine peptides were separated from both hydrolysates using reverse phase high performance liquid chromatography (RP-HPLC). The IC₅₀ for ABTS^?+ scavenging activity of peptide P5 with valine, glycine and asparagine (MW of 282.13 Da) from PH, and peptide P3 with histidine, glycine and alanine (MW of 302.74 Da) from AH was 0.89 and 0.72 mg/mL, respectively. The fractions and purified peptides obtained from Chinese sturgeon hydrolysates could be utilized as natural antioxidant substitutes in pharmaceuticals and food products.