Key Engineering Materials Vols. 531-532

Abstract: Titanium dioxide (TiO2) nanoparticles have been widely used in many fields, including biomedicine, cosmetics and environmental engineering. Recently, it was reported that TiO2 nanoparticles could exert genotoxicity on organisms via the generation of reactive oxygen species (ROS). In the present study, we investigated the effect of TiO2 nanoparticles on RGC-5 cells with or without ultraviolet (UV) B irradiation through MTT assay and determination of hydroxyl radical production. The results demonstrated that TiO2 nanoparticles could efficiently inhibit the growth of RGC-5 cells in the presence of UVB irradiation, whereas there was little impact on target cells in the absence of UV irradiation; UV irradiation could apparently increase the level of hydroxyl radicals in RGC-5 cells and further efficiently inhibit the growth of RGC-5 cells, suggesting that UV irradiation plays an important role in growth inhibition in RGC-5 cells exposed to TiO2 nanoparticles.

Abstract: In order to explore the possibility of the novel CdTe QDs (cadmium telluride quantum dots) as future delivery carrier material, the cytotoxicity effects of CdTe QDs was evaluated in human lung adenocarcinoma A549 cells and with normal HELF cells as control. The cell proliferation fraction was analyzed under the treatments of CdTe QDs by MTT and RTCA. The results showed that CdTe QDs present minor cytotoxicity on the proliferation of these two cell lines at the lower concentrations less than 0.18µmol/L within 72 h, and show toxicity effects under high concentrations. Besides, combination of CdTe QDs at lower concentration (<0.18µmol/L) together with DOX can enhance the killing fraction on A549 more than that of DOX alone, which indicated the drug carrier potential of CdTe QDs, and provided the important basic experiments for further development.

Abstract: One-step and controlled pH hydrothermal synthesis of transition metal disulfide using double molybdenum sources to synthesize MoS2 nano-flowers at low temperature was first reported. Anhydrous molybdenum pentachloride (MoCl5) and four sulfur ammonium molybdate ((NH4) 6Mo7O24•4H2O) were the molybdenum source and CS (NH2) 2 was the sulfur source. Through hydrothermal method, MoS2 was obtained at 180 °C. The pH value of system was controlled by adjusting the molar ratio of MoCl5 and (NH4) 6Mo7O24•4H2O. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area (BET) and transmission electron microscopy (TEM). The results show that the products were hexagonal MoS2 with a high crystalline and flower-like structure consisted of small particles. The thickness of petals is a few to tens of nanometers. By changing the molar ratio of molybdenum sources, the resultant phase from the mixed phase transited to the pure phase and the purity of synthetic MoS2 crystal increaseed.

Abstract: In this paper, we report a successful synthesis of CaWO4:Eu3+ phosphor via an ethanol assisted hydrothermal process. X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscope (FE-SEM) were used to investigate the growth of the products. The water and ethanol volume ratio is found to have extraordinary effect on the particle size and morphological appearance. Flower like ~ 1µm superstructures can be obtained with mixed solution of w/e of 50/50 at 120 °C hydrothermal sysnthesis for 12 h. High concentration of ethanol in aqueous solution was discovered to have a tendency in limiting the interaction between the small particles for crystallization. Temperature and time experiments were also performed to further investigate the growth mechanism of the ethanol assisted hydrothermal process. The photoluminescence properties of flower like CaWO4:Eu3+ has also been investigated.

Abstract: Capacitive sensors for dimethyl methylphosphonate (DMMP) detection were prepared on interdigitated electrodes by airbrush process. Multi-walled carbon nanotubes (MWNTs) and single-walled carbon nanotubes (SWNTs) were used as the chemically sensitive materials, respectively. Different airbrush carbon nanotube thin films were observed and compared by field-emission scanning electron microscope. It indicated that the capacitance of airbrush MWNT sensor decreased immediately when exposed to DMMP and recovered rapidly when removed DMMP in the range of 12-60 mg/m³ (2.4-12 ppm). The sensitivity of airbrush MWNT sensor was about -1.39% at the concentration of 12 mg/m³ (2.4 ppm). It was obvious that the capacitance sensitivity was higher when the MWNTs were more and the film was denser by airbrush. It was also found that the capacitance sensitivity of airbrush SWNT sensor was higher than the corresponding airbrush MWNT sensor.

Abstract: Diamond-like carbon (DLC) films have been extensively studied for more than a decade due to their unique combination of properties. The internal compressive stress affects their adhesion and preventing wide usage of these films. Metal-containing DLC films are expected to relax internal stress. The present work focused on the synthesis, chemical bond and mechanical property characterization of Cr-containing DLC films. The films thickness, internal stress and composition were characterized by scanning electron microscopy, optical interferometry and X-ray photoelectron spectroscopy respectively. Incorporation of Cr into DLC causes an initial internal stress reduction and subsequent stabilization around 0.5 GPa. The hardness behavior was found to depend on Cr content. Films with less than 7.36 at.% Cr (no formation of C-Cr bond) showed a dramatically hardness reduction compared to pure DLC films. Above 7.36 at.% Cr (C-Cr bond formed) the hardness increases above 12 GPa.

Abstract: Polysulfonamide (PSA) superfine fibers were prepared by the self-developed device using the electrospinning technology. The micro surface morphology of the manufactured PSA fibers was characterized by the Scanning Electron Microscope (SEM). It was found that the diameter of PSA fibers and its variance can be influenced by the electrospinning parameters. The experimental results indicate that the morphology of PSA fibers ranged from irregular (beaded) to uniform structure with an increase of solution concentration; the thickness and its variance of the PSA fibers were decreased with the increasing of applied voltage; the morphology and thickness of the PSA fibers were also affected by the tip-to-collector distance. Our investigation shows that the diameter of the PSA fibers can reach around 100nm when spun at the conditions of 28kv applied voltage, 10wt% solution concentration and 15 cm tip-target distance, with a related homogeneous network distribution.

Abstract: In this paper, regenerated silk fibroin/polybutylene terephthalate blended mats were prepared using electrospinning method with different blending ratios. The influence of regenerated silk fibroin/polybutylene terephthalate ratio on the morphology behaviors, fiber diameter and the surface wettability of the blended mats were studied. The morphology of the electrospun fibers were characterized by SEM. The average fiber diameter and its distribution can be obtained from the SEM pictures using software Image J. The average fiber diameter was 280nm to 486nm and it changed with the blending ratio. The contact angles and penetration times were used to characterize the surface wettability of the nanofiber membranes. It was found that with the increase of regenerated silk fibroin amount, the surface contact angles and penetration times decreased, which meant that the wettability was greatly improved.

Abstract: Various mechanisms and correlations have been developed for prediction of thermal conductivity of nano-suspensions. However, seldom theoretical researches on thermal conductivity of nanofluids containing surfactant are found. In this work, a thermal conductivity prediction-model of nanofluid containing surfactants is proposed based on Leong et al.’s model and Langmuir adsorption theory by considering the interfacial surfactant layers. The thickness of the interfacial layer is defined by Langmuir adsorption theory. Compared with the experimental data available in the literature on thermal conductivity of nanofluid containing surfactants, the calculated values on the proposed model have been verified that the proposed models show reasonably good agreement with the experimental results and give better predictions for the effective thermal conductivity of nanofluids compared to existing classical models.

Abstract: New nano nickel-doped titanium dioxide composites had been produced by a conducting sol-gel method. The alginate gel was used as a template to prevent the conglomeration of the inorganic materials. In this experiment, nickel nitrate, tetrabutyl titanate and sodium alginate were used as main materials to prepare different amount nickel-doped TiO₂ particles. The amount of Ni was studied from 0 to 9 mol.-% (where mol.-% refers to the Ni/TiO₂ molar ratio), and the Ni/TiO₂ composites were characterized by XRD, FT-IR, TG-DTA, and we carried out doping amount, catalyst amount and illumination time influence on photocatalytic performance of nano Ni/TiO₂ composite in aqueous methyl orange. The activity of TiO₂ gradually increased with the increasing of doping amount, and there was highest catalytic efficiency when Ni = 9 % mol.