Beaklike SnO2 nanorods with strong photoluminescent and field-emission properties

Beaklike SnO2 nanorods were synthesized by a vapor-liquid-solid approach using Au as a catalyst. The nanorods grow along the [10 1] direction and the beak is formed by switching the growth direction to [1 12] through controlling the growth conditions at the end of the synthesis. The photoluminescence (PL) spectrum of the nanorods exhibits visible light emission with a peak at 602 nm. The field-emission (FE) properties of the nanorods have been measured to exhibit a turn-on field of 5.8 V microm(-1). A comparative study of FE measurements between SnO2 nanorods with uniform diameters and these beaklike nanorods suggests that the shape and curved tips are important factors in determining the FE properties.     

Preparation of poly(acrylic)/SiO2/EuL3 x 2H2O, hybrid thin films from monodispersed colloidal silica

In this study, poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films were prepared from various acrylic monomers (MMA and EDMA/TMPTA), lanthanide metal complexes (EuL3 x 2H2O, L = pyridine carboxylic acid), and monodispersed colloidal silica with a coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). It is a combination of the sol-gel reaction, thermal polymerization, and spin coating. The silica content in the hybrid thin films is fixed at 20 wt%, and the EuL3 x 2H2O content is varied from 0.01 g to 0.07 g. FTIR and EA analysis confirms the chemical structure of the prepared EuL3 x 2H2O and poly(acrylic)/SiO2/EuL3 x 2H2O hybrid thin films. UV-Vis spectra and n&k analysis shows that the hybrid thin film has good transparency in visible light. The refractive index of hybrid thin films can be effectively controlled through the EuL3 x 2H2O content. The PL spectra shows that the strongest emission peak occurs at 615 nm and the emission intensity increases to the peak maximum at an EuL3 x 2H2O content of 0.05 g. Both TGA and PL analysis show that the prepared hybrid thin films from the crosslinked acrylic polymer moiety have much better film uniformity, thermal stability, and fluorescence properties. The TEM diagram shows that the MSMA/SiO2/EuL3 x 2H2O particles with a size 15-20 nm are well dispersed in the reaction solution. The SEM diagram shows that the particle distribution in the prepared hybrid thin films is uniform and no phase separation is observed. Finally, AFM analysis indicates that the prepared hybrid thin films have an excellent surface planarity.     

Development of a Quantitative Multi-Mycotoxin Method in Rice, Maize, Wheat and Peanut Using UPLC-MS/MS

Mycotoxins are secondary metabolites produced by fungi, such as Fusarium, Penicillium, and Aspergillus, which are toxic to humans with high risk factors and pose a significant threat to human health. This study was focused mostly on well-known mycotoxins, such as aflatoxins (AFB₁, AFB₂, AFG₁ and AFG₂), fumonisin (FB₁, FB₂), deoxynivalenol (DON), zearalenone (ZON), ochratoxin A, T-2 and HT-2, in grains. The multi-mycotoxin methods developed in this study utilise an analysis of mycotoxin through liquid chromatography tandem mass spectrometry (LC-MS/MS), which can significantly improve sample analysis efficiency. The Myco6in1? immunoaffinity column was used for purification to reduce interference from the substrate. Gradient separation to obtain the best peak shift was conducted using solvent with 0.1 % formic acid in deionised water and methanol, and gradient separation was performed on an ACQUITY BEH C18 column chromatograph. The recovery rate test for each toxin using substrates such as rice, peanut, wheat and maize mostly indicated good average recovery rates between 70 % and 120 % and the coefficient of variation mostly under 15 %. The limits of quantification (LOQ) identified by this method are less than 5 ng/g in most toxins, except for 20 ng/g in FB₁and FB₂. This method can rapidly and simultaneously analyse 11 mycotoxins in 9 min. It can be applied for the practical examination of mycotoxins in food to protect public health.     

Preparation and optical properties of organic/inorganic nanocomposite materials by UV curing process

In this study, photo-polymerized poly(acrylic)/silica hybrid thin films were prepared from various acrylic monomers and monodispersed colloidal silica with the coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MSMA). The silica content in the hybrid thin films varied from 0 to 50 wt.%. The experimental results show that the particle size of silica in hybrid films could be effectively controlled at 15–20 nm as the weight ratio of MSMA to colloidal silica is higher than 0.68 and 0.60 for the poly(methyl methacrylate)/silica (US) and poly(ethylene glycol dimethacrylate-trimethylolpropane trimethacrylate)/silica (UDT) hybrid materials, respectively. The polymerization conversion for US and UDT hybrid materials could reach to 100% and 94.5%, respectively. The comparison of surface roughness with the film thickness is less than 0.10%, indicating the excellent surface planarity of the prepared hybrid thin films. Besides, the prepared hybrid films from the crosslinked acrylic polymer moiety show much better film uniformity, thermal stability and mechanical properties than those obtained from poly(methyl methacrylate). The refractive index decreases with increasing the silica content in the hybrid films. Excellent optical transparency is obtained in the prepared hybrid films. These results show that the prepared hybrid thin films have potential applications as passive films for optical devices.     

A novel synthetic route to Y2O3:Tb phosphors by bicontinuous cubic phase process

This study applies a novel approach to prepare the terbium-doped yttrium oxide phosphors (Y₂O₃:Tb³⁺) using the bicontinuous cubic phase (BCP) process. The experimental results show that the prepared precursor powder was amorphous yttrium hydroxide Y_1−xTb_x(OH)₃ with a spherical shape and primary size 30–50 nm. High crystallinity phosphors with body-centered cubic structures were obtained after heat treatment above 700 °C for 4 h. The primary size of the phosphors grew to 100–200 nm, and dense agglomerates with a size below 1 μm were formed during the calcination. The obtained Y₂O₃:Tb³⁺ phosphor had a strong green emitting at 542 nm. The optimum Tb³⁺ concentration was 1 mol% to obtain the highest PL intensity. This study indicates that the calcining temperature of 700 °C needed for high luminescence efficiency in this work is much lower than 1000 °C or above needed for the conventional solid-state method.     

Development of a modified concrete rheometer to measure the rheological behavior of conventional and self-consolidating concretes

The modified concrete rheometer (MCR) apparatus developed in this study is based on existing concrete rheometers, the main differences being the gap size and measurement method, and thus the interpretation of the results. The gap between the inner cylinder wall and the tip of the vane was set to 6.4 times the diameter of the largest coarse aggregate in order to reduce interaction between the aggregate and the wall and the friction force from the wall. The MCR apparatus was used to measure yield torque directly at different low rotational speeds (above 0.003 rev/s). A study of the yield torque and viscosity of 37 fresh concrete mixtures was also made, with a particular focus on self-compacting concrete or self-consolidating concrete (SCC), and the results were compared with those obtained using other workability tests. The test results showed that the MCR can differentiate between conventional concrete (CC), powder-type SCC and SCC with viscosity-modifying agents (VMA). The rheological behavior of powder-type SCC was found to be influenced by the composition of Class F fly ash and ground granulated blast-furnace slag (GGBFS), and this type of concrete exhibited a wider range of viscosity and yield torque values. Despite the lower powder content and larger water to binder ratio (w/b), the viscosity of VMA-type SCC was shown to be slightly lower than that of powder-type SCC, and the values were clustered together within a certain range; thus, the workability of SCC containing VMA is more easily controlled. In addition, the MCR apparatus can also be applied to CC of differing viscosity and yield torque, thus making this apparatus suitable for determination of the workability of all kinds of fresh concrete.     

Activation of Coronary Arteriolar PKCβ2 Impairs Endothelial NO-Mediated Vasodilation: Role of JNK/Rho Kinase Signaling and Xanthine Oxidase Activation

Protein kinase C (PKC) activation can evoke vasoconstriction and contribute to coronary disease. However, it is unclear whether PKC activation, without activating the contractile machinery, can lead to coronary arteriolar dysfunction. The vasoconstriction induced by the PKC activator phorbol 12,13-dibutyrate (PDBu) was examined in isolated porcine coronary arterioles. The PDBu-evoked vasoconstriction was sensitive to a broad-spectrum PKC inhibitor but not affected by inhibiting PKCβ2 or Rho kinase. After exposure of the vessels to a sub-vasomotor concentration of PDBu (1 nmol/L, 60 min), the endothelium-dependent nitric oxide (NO)-mediated dilations in response to serotonin and adenosine were compromised but the dilation induced by the NO donor sodium nitroprusside was unaltered. PDBu elevated superoxide production, which was blocked by the superoxide scavenger Tempol. The impaired NO-mediated vasodilations were reversed by Tempol or inhibition of PKCβ2, xanthine oxidase, c-Jun N-terminal kinase (JNK) and Rho kinase but were not affected by a hydrogen peroxide scavenger or inhibitors of NAD(P)H oxidase and p38 kinase. The PKCβ2 protein was detected in the arteriolar wall and co-localized with endothelial NO synthase. In conclusion, activation of PKCβ2 appears to compromise NO-mediated vasodilation via Rho kinase-mediated JNK signaling and superoxide production from xanthine oxidase, independent of the activation of the smooth muscle contractile machinery.     

The influence of surface oxide on the growth of metal/semiconductor nanowires

We report the critical effects of oxide on the growth of nanostructures through silicide formation. Under an in situ ultrahigh vacuum transmission electron microscope, it is observed from the conversion of Si nanowires into the metallic PtSi grains epitaxially through controlled reactions between lithographically defined Pt pads and Si nanowires. With oxide, instead of contact area, single crystal PtSi grains start forming either near the center between two adjacent pads or from the ends of Si nanowires, resulting in the heterostructure formation of Si/PtSi/Si. Without oxide, transformation from Si into PtSi begins at the contact area between them, resulting in the heterostructure formation of PtSi/Si/PtSi. The nanowire heterostructures have an atomically sharp interface with epitaxial relationships of Si(20-2)//PtSi(10-1) and Si[111]//PtSi[111]. Additionally, it has been observed that the existence of oxide significantly affects not only the growth position but also the growth behavior and the growth rate by two orders of magnitude. Molecular dynamics simulations have been performed to support our experimental results and the proposed growth mechanisms. In addition to fundamental science, the significance of the study matters for future processing techniques in nanotechnology and related applications as well.     

Injection molding of delamination‐free ultra‐high‐molecular‐weight polyethylene

When ultra‐high‐molecular‐weight polyethylene (UHMWPE) in powder form is injection molded, the so‐called delamination layering occurs near the skin of the parts. This layering defect hampers UHMWPE's superior wear resistance property and part surface quality. The delamination layer was caused by a combination of excessive shear stress near the part surface and high degree of molecular entanglement of UHMWPE. A mold insulation method that delays the rapid cooling of UHMWPE to reduce the shear stress and improve the polymer chain “interdiffusion” across the entangled chain bundles was used to eliminate the delamination layer. When the insulation layer thickness and mold temperature were optimized, the delamination layer was eliminated completely while still maintaining a reasonable cooling/cycle time. The delamination‐free parts were found to regain UHMWPE's superior impact resistance and tensile properties. POLYM. ENG. SCI., 59:2313–2322, 2019. © 2019 Society of Plastics Engineers