Synergistic effect of Co + Mo codoping on the photocatalytic performance of titania thin films

Thin films of anatase codoped with 0.01 mol% Co and 0.01 mol% Mo up to 5.00 mol% Co and 5.00 mol% Mo were fabricated by spin coating on soda-lime-silica glass substrates. The films subsequently were calcined in air at 450 °C for 2 h. The mineralogical, chemical, morphological, topographical, optical, and photocatalytic properties of the films were investigated in order to assess the factors and mechanisms affecting the photocatalytic properties. The analytical techniques included glancing angle X-ray diffraction, X-ray photoelectron spectrometry, atomic force microscopy, UV–Vis spectrophotometry, and methylene blue photodegradation. A key determinant of the data was the solubility limit of the dopants, particularly Co. When this was exceeded (≥0.30 mol%), the formation of undetectable precipitates commenced blockage of the active sites, thereby reducing the photocatalytic performance. The initial precursor cation valences altered from Co²⁺ and Mo⁵⁺ to Co²⁺/Co³⁺ and Mo⁴⁺/Mo⁵⁺ upon interstitial solid solution. The absence of charge-compensating Ti³⁺/Ti⁴⁺ redox indicates that charge compensation for the codoping was by IVCT through the reaction Co²⁺ + Mo⁵⁺ ↔ Co³⁺ + Mo⁴⁺. While the three dominant factors affecting the band gap were crystallinity, grain size, and precipitation, the band gap did not dominate the photocatalytic performance or its kinetics. These were reduced by blockage of the active sites by dopant precipitates and, to a lesser extent, from contamination from the cations from the substrate. These phases were the dominant factor in decreasing the optical transmission and thus increasing the band gap through the absorption, reflection, and scattering mechanisms of these grains; the crystallinity and grain size were of secondary importance.     

Self-assembly of colloidal nanocrystals as route to novel classes of nanostructured materials

Colloidal crystallisation is the only way to obtain three-dimensional ordered materials in which semiconductor, metallic, and magnetic nanocrystals are in close contact. It is expected that the quantum mechanical and dipolar interactions between the nanocrystal units can lead to unseen physical phenomena and materials. Here we review the development of this new and exciting field. We first compare nanocrystal superlattices with regular atomic solids regarding their mechanical strength and opto-electronic properties. We describe how nanocrystal superlattices have been obtained from colloid suspensions in several ways. The thermodynamic driving force for colloidal crystallisation is discussed in terms of inter-particle interactions in a good solvent and entropy. We compare the binary superlattices that have been obtained by solvent evaporation with the predictions of the hard-sphere model and show that semiconductor nanocrystals in a good solvent can behave as hard spheres. Finally, we discuss the quantum mechanical and dipolar interactions in nanocrystal superlattices and review recent studies of the opto-electronic and magnetic properties of novel superlattice materials.     

Expression, Characterization and Synergistic Interactions of Myxobacter Sp. AL-1 Cel9 and Cel48 Glycosyl Hydrolases

The soil microorganism Myxobacter Sp. AL-1 regulates in a differential manner the production of five extracellular cellulases during its life cycle. The nucleotide sequence of a cel9-cel48 cluster from the genome of this microorganism was recently obtained. Cel48 was expressed in Escherichia coli to generate a His₆-Cel48 protein and the biochemical properties of the pure protein were determined. Cel48 was more efficient in degrading acid-swollen avicel (ASC) than carboxymethylcellulose (CMC). On the other hand, cel9 was expressed in Bacillus subtilis from an IPTG-inducible promoter. Zymogram analysis showed that after IPTG-induction, Cel9 existed in both the cell fraction and the culture medium of B. subtilis and the secreted protein was purified to homogeneity by FPLC-ionic exchange chromatography. The exocellobiohydrolase Cel48 showed a synergism of 1.68 times with the endocellulase Cel9 during ASC degradation using an 8.1-fold excess of Cel48 over Cel9. Western blot analysis revealed that both proteins were synthesized and secreted to the culture medium of Myxobacter Sp. AL-1. These results show that the cel9-cel48 cluster encodes functional endo- and exo-acting cellulases that allows Myobacter Sp. AL-1 to hydrolyse cellulose.     

NNK和B[a]P在卷烟烟气基质中的联合致突变性

以苯并[a]芘(B[a]P)、甲基亚硝胺吡啶基丁酮(NNK)为目标化合物,设置卷烟烟气冷凝物(CSC)的浓度为0(CK),0.005,0.010,0.015,0.020 mg/mL;NNK的浓度为0(CK),0.005,0.010,0.020,0.040 mg/mL;B[a]P的浓度为0(CK),0.00025,0.00050,0.00075,0.00100 mg/mL,研究了NNK,B[a]P和CSC的联合致突变性。结果表明:①CSC,NNK和B[a]P均可诱导鼠伤寒沙门氏菌TA98,TA100发生突变,且剂量-效应明显。②B[a]P与CSC联合呈相加作用;B[a]P与NNK联合高剂量呈弱相加作用;CSC与NNK联合低剂量呈弱相加作用。③在不同情况下,三者联合作用致TA98呈弱相加作用。综上,NNK和B[a]P在卷烟烟气基质中的联合致突变性呈现量效、时效和先后作用顺序的复杂性。     

Synergistic action between fractions of essential oils from Cymbopogon citratus, Ocimum gratissimum and Thymus vulgaris against Penicillium expansum

Penicillium expansum is a mould that causes the rotting of several fruits and vegetables, especially apples onto which it also synthesizes some dangerous mycotoxins. The degree of synergism between fractions of essential from Cymbopogon citratus, Ocimum gratissimum and Thymus vulgaris was evaluated against two mycotoxin producing strains of P. expansum. The antifungal activity determined by dilution method and expressed as a Number of Decimal Reduction of the colony forming units per ml (NDR cfu) showed that the essential oils extracted from O. gratissimum was significantly (P < 0.05) more active against P. expansum than those extracted from C. citratus and T. vulgaris. Fractions enriched with oxygenated terpenes were significantly (P < 0.05) more active than their respective essential oils, whereas most of the fractions enriched with terpene hydrocarbons, were significantly (P < 0.05) less active. The fungicidal activity of mixtures of fractions from the same essential oils or from two different essential oils showed that there exist synergistic, additive and antagonistic effects between fractions of the three essential oils tested against both fungal strains. The synergistic effects observed could be exploited in order to maximize the antimicrobial activity of essential oils and to minimize the concentrations of essential oil required to produce a given antimicrobial effect without any alteration of the food test.     

Carbohydrate derived copoly(lactide) as the compatibilizer for bacterial cellulose reinforced polylactide nanocomposites

A novel, entirely bio-derived polylactide carbohydrate copolymer (RP1) is used as a compatibilizer, to produce bacterial cellulose (BC) poly(l-lactide) (PLLA) nanocomposites with improved mechanical properties. Contact angle measurements of RP1 droplets on single BC nanofibres proved that it has a higher affinity towards BC than PLLA. RP1 has a comparable Young’s modulus, but lower tensile strength, than PLLA. When RP1 was blended with PLLA at a concentration of 5 wt%, the tensile modulus and strength of the resulting polymer blend decreased from 4.08 GPa and 63.1, respectively, for PLLA to 3.75 GPa and 56.1 MPa. A composite of BC and PLLA (with 5 wt% RP1 and 5 wt% BC) has a higher Young’s modulus and tensile strength, compared to either pure PLLA or PLLA–BC nanocomposites.     

Interaction Between Cationic and Anionic Surfactants: Detergency and Foaming Properties of Mixed Systems

The micellar and interfacial behavior of mixtures of the anionic surfactant (alcohol ether sulfate, AES) with quaternary ammonium type cationic surfactants dodecyltrimethyl ammonium chloride (DTAC), dodecyl-(2-hydroxyethyl)-dimethyl ammonium chloride (DHDAC), dodecyl-di(2-hydroxyethyl)-methyl ammonium chloride (DHHAC) were investigated by means of surface tension measurements. Various physicochemical properties such as surface activity parameters (CMC, γ _CMC, Г _max, A _min), the micellar and interfacial compositions (x ₁ ^m , x ₁ ^σ ), interaction parameters (β ^m , β ^σ ), and activity coefficients ( \(f_{1}^{m}\) , \(f_{2}^{m}\) , \(f_{1}^{\sigma }\) , \(f_{2}^{\sigma }\) ) were evaluated. The influence of the hydroxyethyl groups of cationic surfactant component on the physicochemical properties of mixed systems has been analyzed. It is observed that the CMC values of the three mixed systems decrease with increases in the number of hydroxyethyl groups of the cationic surfactant component. From the results of β ^σ and β ^m values, the interactions between molecules for the three surfactant mixtures at the air/liquid interface increase in the following order DHHAC/AES < DHDAC/AES < DTAC/AES, but it is the opposite for the interactions in mixed micelles. The detergency and foaming properties of mixed systems were also studied. As expected, complex surfactant systems exhibit good detergency and foaming properties.     

Cavitation Erosion Corrosion Behaviour of Manganese-nickel-aluminum Bronze in Comparison with Manganese-brass

The cavitation erosion corrosion behaviour of ZQMn12-8-3-2 manganese-nickel-aluminum bronze and ZHMn55-3-1 manganese-brass was investigated by mass loss, electrochemical measurements (polarization curves and electrochemical impedance spectroscopy) and the cavitation damaged surfaces were observed by scanning electron microscopy (SEM). The results showed that ZQMn12-8-3-2 had better cavitation erosion resistance than ZHMn55-3-1. After the cavitation erosion for 6 h, the cumulative mass loss of ZQMn12-8-3-2 w...     

猪油中复合型抗氧化剂的研究

研究了几种没食子酸酯对猪油氧化的抑制作用，以及与其它物质的协同增效作用，考查了一定配比组成的复合型抗氧化中增效剂的配比，发现没食子酸辛酯与柠檬酸及蛋氨酸按一定配比组成的复合抗氧化剂，对猪油有良好的抗氧化活性，并有高效、低毒的特点。     

有关聚乙二醇抑制机理的不同看法——读郭东荣等同志的“聚乙二醇抑制机理研究”一文之后

郭东荣等同志提出聚乙二醇抑制机理之一是聚乙二醇与K~ 形成复合物而起作用,而本文认为是协同作用的结果,就是K~ 能使粘土表面的水化膜变薄,有利于聚乙二醇的吸附包被作用,从而有利于抑制泥页岩的分散。