Evaluation of Antibacterial Activity of Nanostructured Copolymers of Poly (Naphthylamine)

The present preliminary investigation highlights for the first time the antibacterial activity of copolymers of nanostructured poly (naphthylamine) (PNA) with aniline (PNA-co-PANI) and o-toluidine (PNA-co-POT) against E. coli and S. aureus. The antibacterial effect of these nanosized polymers was found to be much higher than that reported for pristine polyaniline. The chemical structure and morphology of the copolymers was found to play a significant role in deciding the antimicrobial efficiency of the copolymers. A proposed mechanism of antimicrobial effect has also been suggested. Our results indicate that the antimicrobial effects of the copolymers could be useful ingredients for biomaterials used in the development of food packaging and medical devices.     

Photophysical Behaviors of Single Fluorophores Localized on Zinc Oxide Nanostructures

Single-molecule fluorescence spectroscopy has now been widely used to investigate complex dynamic processes which would normally be obscured in an ensemble-averaged measurement. In this report we studied photophysical behaviors of single fluorophores in proximity to zinc oxide nanostructures by single-molecule fluorescence spectroscopy and time-correlated single-photon counting (TCSPC). Single fluorophores on ZnO surfaces showed enhanced fluorescence brightness to various extents compared with those on glass; the single-molecule time trajectories also illustrated pronounced fluctuations of emission intensities, with time periods distributed from milliseconds to seconds. We attribute fluorescence fluctuations to the interfacial electron transfer (ET) events. The fluorescence fluctuation dynamics were found to be inhomogeneous from molecule to molecule and from time to time, showing significant static and dynamic disorders in the interfacial electron transfer reaction processes.     

Inversion Twin Boundaries in Zinc Oxide

The crystallography and atomic structure of inversion twin boundaries were studied in polycrystalline ZnO using conventional transmission electron microscopy and high-resolution electron microscopy. Inversion twin boundaries. In order to determine the atomic structure of the inversion twin boundary, high-resolution transmission electron images were compared with simulated images. The atomic structure of the inversion boundary was determined to have a head-to-head configuration and its stacking sequence is AαBβAα-ATCαA, where A, B, and C are Zn atomic planes and α, β, and T are O planes. A slight contraction of the planes in the boundary region is detected.     

Transmission Electron Microscope Study of Antimony-Doped Zinc Oxide Ceramics

A transmission electron microscope investigation of a ZnO powder and low-temperature air-sintered pellets with small additions of Sb₂O₃ was conducted in order to study the thin Sb-rich film on the surfaces of ZnO particles. This film was found to be noncrystalline at temperatures below 700°C, and partially crystalline or completely crystalline above this temperature. An oriented overgrowth of the spinel Zn₇Sb₂O₁₂ was observed on the prismatic planes as well as on the basal planes of ZnO crystallites. It is shown that these coherently overgrown spinel films are responsible for the inhibition of grain growth at high temperatures.     

Enhanced Activity and Sustained Release of Protocatechuic Acid,a Natural Antibacterial Agent,from Hybrid Nanoformulations with Zinc Oxide Nanoparticles

Hybrid nanostructures can be developed with inorganic nanoparticles (NPs) such as zinc oxide (ZnO) and natural antibacterials. ZnO NPs can also exert antibacterial effects, and we used them here to examine their dual action in combination with a natural antibacterial agent, protocatechuic acid (PCA). To produce hybrid nanoformulations, we functionalized ZnO NPs with four types of silane organic molecules and successfully linked them to PCA. Physicochemical assessment confirmed PCA content up to ~18% in hybrid nanoformulations, with a PCA entrapment efficiency of ~72%, indicating successful connection. We then investigated the in vitro release kinetics and antibacterial effects of the hybrid against Staphylococcus aureus. PCA release from hybrid nanoformulations varied with silane surface modification. Within 98 h, only 8% of the total encapsulated PCA was released, suggesting sustained long-term release. We used nanoformulation solutions collected at days 3, 5, and 7 by disc diffusion or log reduction to evaluate their antibacterial effect against S. aureus. The hybrid nanoformulation showed efficient antibacterial and bactericidal effects that also depended on the surface modification and at a lower minimum inhibition concentration compared with the separate components. A hybrid nanoformulation of the PCA prodrug and ZnO NPs offers effective sustained-release inhibition of S. aureus growth.     

Synthesis of carbon nanotubes on pulse plated Ni nanocrystalline substrate in ethanol flames

A novel process for synthesizing carbon nanotubes (CNTs) in ethanol flames is described. The CNTs grow on a nanocrystalline Ni layer which was electro-deposited on a Ni substrate using periodic reverse (PR) pulse plating. The grain size of the plating and CNT morphology were revealed using XRD, SEM, TEM and Raman spectroscopy. It was found that the quality of the plating and the corresponding CNTs were related to two plating parameters: output pulse frequency (f) and duty cycle (r). The growth mechanism of CNTs in this process is discussed.     

Nanostructures of pyrolytic carbon from a polyacetylene thin film

Pyrolysis of a polyacetylene thin film has been performed in order to carbonize at temperatures of 500 to 1000 °C in vacuum. A trans-polyacetylene thin film was synthesized using a Ziegler-Natta catalyst. A black char below 20% in weight of the original PA film remained after pyrolysis. Structural properties and morphology of the black chars were investigated using Raman scattering spectrum, X-ray diffraction measurements, and scanning and transmission electron microscopy. Dehydrogenation and carbonization of the PA film were almost finished at a pyrolysis temperature of 800 °C. However, hollow spherical or elliptical nano-particles of tens of nanometers in size, which are composed of graphite structure, were included in the black chars obtained at all pyrolysis temperatures in this work. The formation mechanism of a graphite crystal in nanometer size from a PA crystal was discussed.     

On the Enhanced Antibacterial Activity of Antibiotics Mixed with Gold Nanoparticles

The bacterial action of gentamicin and that of a mixture of gentamicin and 15-nm colloidal-gold particles on Escherichia coli K12 was examined by the agar-well-diffusion method, enumeration of colony-forming units, and turbidimetry. Addition of gentamicin to colloidal gold changed the gold color and extinction spectrum. Within the experimental errors, there were no significant differences in antibacterial activity between pure gentamicin and its mixture with gold nanoparticles (NPs). Atomic absorption spectroscopy showed that upon application of the gentamicin-particle mixture, there were no gold NPs in the zone of bacterial-growth suppression in agar. Yet, free NPs diffused into the agar. These facts are in conflict with the earlier findings indicating an enhancement of the bacterial activity of similar gentamicin–gold nanoparticle mixtures. The possible causes for these discrepancies are discussed, and the suggestion is made that a necessary condition for enhancement of antibacterial activity is the preparation of stable conjugates of NPs coated with the antibiotic molecules.     

Novel Green Synthesis of Zinc Oxide Nanoparticles Using Orange Waste and Its Thermal and Antibacterial Activity

Journal of Inorganic and Organometallic Polymers and Materials - Zinc oxide nanoparticles (ZnO NPs) prepared via eco-friendly synthesis (using orange peels) are investigated. Pseudomonas Aeruginosa...     

纳米氧化锌的制备及抑菌性能的研究

采用液相沉淀法制备了纳米氧化锌,分别用X射线衍射分析（XRD）、紫外可见吸收光谱（UV-Vis）、红外光谱等物理手段对纳米氧化锌进行了表征,并运用抑菌圈法对所制备的纳米氧化锌进行了定性的抗菌性研究。结果表明,制备的纳米氧化锌颗粒大小均匀,分散性较好,对金黄色葡萄球菌和大肠杆菌有良好的抑制效果。     

Functional Gelatin-Carbon Nanotubes Nanohybrids With Enhanced Antibacterial Activity

Hybrid materials with enhanced antibacterial activity were prepared by incorporation of carbon nanotubes within gelatin-fluoroquinolones bioconjugates. Gelatin bioconjugates were characterized by UV-Vis, FT-IR, and calorimetric analyses, nanohybrids by morphological analyses. Biocompatibility was evaluated on human mesenchymal stem cells, and antibacterial performance against Klebsiella pneumoniae and Escherichia coli. Minimun inhibitory concentrations from 0.025 to 0.05 µg mL^?1 and from 0.025 to 0.10 µg mL^?1, and MBC from 0.025 to 0.10 µg mL^?1 and from 0.05 to 0.20 µg mL^?1 were detected for Escherichia coli and Klebsiella pneumoniae, respectively, showing that nanotubes increase antimicrobial activity comparing to both free and gelatin-conjugated drugs.     

二氧化钛和氧化锌的光催化活性(英)

通过二氧化钛和氧化锌的光催化作用研究,讨论了有机及无机表面处理对该作用的影响。与无机处理相比,有机表面处理对降低二氧化钛和氧化锌的光催化活性有很大影响,进而显著地减小了其在化妆品中的副作用,具有重要的意义。     

La和Ce改性四针状氧化锌晶须抗菌纤维的制备与抗菌性

选用四针状氧化锌晶须(T-ZnOw)作为主要成分,并利用稀土元素可在T-ZnOw禁带中产生附加能级扩展光谱响应范围的性质,选用常见稀土元素La和Ce对T-ZnOw进行改性,采用浸渍法使改性T-ZnOw均匀分布在活性碳纤维上,制备出一种具有可见光响应的高性能广谱抗菌性纤维。结果表明,在经过稀土元素改性的T-ZnOw负载到活性碳纤维后,制成的新型纤维具有较好的抗菌性。     

Solvated structure of C60 nanowhiskers

This work characterizes the structure of C₆₀ nanowhiskers prepared by the liquid-liquid interfacial precipitation method in the C₆₀-saturated m-xylene and isopropyl alcohol system. Transmission electron microscopy and X-ray diffraction measurement show that the C₆₀ nanowhiskers had a hexagonal structure with cell dimensions a = 2.407 nm and c = 1.018 nm which is different from pristine C₆₀. The structure of the C₆₀ nanowhiskers in solution is different from that of the solvated structure reported for the C₆₀ nanotubes but similar to that reported for the C₆₀ bulk crystal solvated with m-xylene. X-ray diffraction analysis also showed a shift to fcc structure after solvent evaporation. The C₆₀ nanowhiskers prepared using toluene as solvent also showed a similar solvated structure, and a more rapid structural change into fcc upon drying was again observed.     

Partially graphitized carbon filaments from as-synthesized silica/surfactant composite

The carbonization behavior of surfactants templated within mesoporous silica is studied in detail. Cetyltrimethylammonium bromide and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (P123) are used as the structure-directing agents for MCM-41 and SBA-15 synthesis, respectively. Thermal treating the as made silica/surfactant composites under argon flow at 900 °C produces partially graphitized carbon filaments as a result of the carbonization of the surfactants within the mesopores. Furthermore, the carbon materials derived from P123 in SBA-15 yield a more developed graphite structure than the carbon obtained from CTAB in MCM-41, as evidenced by the narrower X-ray Bragg reflections in the powder XRD and larger I_G/I_D ratio in the Raman spectra.     

Nitrogen-Doped Zinc Oxide for Photo-Driven Molecular Hydrogen Production

Due to its thermal stability, conductivity, high exciton binding energy and high electron mobility, zinc oxide is one of the most studied semiconductors in the field of photocatalysis. However, the wide bandgap requires the use of UV photons to harness its potential. A convenient way to appease such a limitation is the doping of the lattice with foreign atoms which, in turn, introduce localized states (defects) within the bandgap. Such localized states make the material optically active in the visible range and reduce the energy required to initiate photo-driven charge separation events. In this work, we employed a green synthetic procedure to achieve a high level of doping and have demonstrated how the thermal treatment during synthesis is crucial to select specific the microscopic (molecular) nature of the defect and, ultimately, the type of chemistry (reduction versus oxidation) that the material is able to perform. We found that low-temperature treatments produce material with higher efficiency in the water photosplitting reaction. This constitutes a further step in the establishment of N-doped ZnO as a photocatalyst for artificial photosynthesis.     

Synthesis of nanoporous carbide-derived carbon by chlorination of titanium silicon carbide

Synthesis of nanoporous carbide-derived carbon, CDC, by extraction of titanium and silicon from Ti₃SiC₂ by chlorine is discussed in this work. Thermodynamic simulations using a Gibbs free energy minimization program provided general guidelines to the experimental design. Raman spectroscopy, X-ray diffraction, and electron microscopy studies showed that the structure of CDC depends on the chlorination temperature. The low temperature synthesis resulted in an amorphous CDC structure. Noticeable graphite formation starts above 800 °C and well ordered graphite ribbons of 1-3 nm in thickness form at 1200 °C. The macroscopic volume and shape of Ti₃SiC₂ preform were preserved during the transformation. However, the chlorination resulted in the formation of cracks between the former grains of the polycrystalline Ti₃SiC₂ preform. These cracks are believed to be caused by a contraction in the direction perpendicular to the basal planes of Ti₃SiC₂. The synthesized nanoporous carbon demonstrated excellent sorption properties. Energy dispersive X-ray spectroscopy studies showed that Ti₃SiC₂ material chlorinated at 400 °C is capable of trapping over 40 wt.% of Cl₂.     

形态学实验和分析方法在高分子研究中的意义与应用

论述了形态学实验分析方法（X射线衍射、电子显微镜和光学显微镜）的概况及其在高分子研究中的应用，为在高分子材料与工程实践中合理运用该实验方法。掌握正确的图象分析方法提供理论依据。     

氧化铝增强无机硅酸锌涂层的电化学阻抗谱研究

无机硅酸锌涂层是一种广泛使用的钢铁重防腐涂层。采用在涂料填料中加入氧化铝的方法可以得到具有更好耐磨性能的富锌涂层。本实验研究利用电化学阻抗谱法(EIS)研究了氧化铝的加入对涂层腐蚀防护性能的影响,结果表明氧化铝颗粒的加入使涂层的腐蚀防护性能略有提高。