流动注射-氢化物发生-原子吸收光谱法测定雪中的微量铅

建立了测定雪中微量铅的流动注射-氢化物发生-原子吸收光谱法。在优化条件下。测定铅的线性范围为0～52．0ng／mL，线性回归方程为A=0．018c 0．016，相关系数r=0．9995，检出限为0．2ng／mL。用于雪中微量铅的测定，加标回收率为94．2％～107．3％，相对标准偏差为1．47％～3．22％。该方法的测定结果与标准加入法基本一致。     

PBT／PC共混体系流变性能与形态结构研究

采用毛细管流交仪测定了ＰＢＴ／ＰＣ共混物的表观粘度、剪切应力，观察了不同共混物组成和不同温度下共混物的流变行为，并借助扫描电镜对共混物和微观形态结构进行分析。结果表明：ＰＢＴ／ＰＣ熔体共混物的流变行为接近假塑性流体．温度对共混物的流变行为影响很大，共混物的熔体粘度在ＰＢＴ／ＰＣ为９０／１０和６０／４０时呈双极值．共混物为两相结构，ＰＣ含量为４－５０％时呈两互锁结构。     

Synergistic effects between silicon-containing flame retardant and potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) on flame retardancy and thermal degradation of PC

A novel flame retardant (PSiN), containing silicon and nitrogen, was synthesized using N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane (KH-602) and diphenylsilanediol through solution polycondesation and it was used together with potassium-4-(phenylsulfonyl)benzenesulfonate (KSS) to prepare a flame-retardant system for polycarbonate (PC). The structure and thermal property of PSiN were characterized by Fourier transform infrared spectroscopy (FTIR), ¹HNMR and thermogravimetric analysis (TG) tests. Flammability and thermal behaviors of PC/KSS/PSiN systems were estimated by limited oxygen index (LOI), cone calorimeter, vertical burning test (UL-94), and TG tests. The results showed that the flame retardancy and char residues of PC/KSS system were improved with the addition of PSiN. When 1 mass% PSiN and 0.5 mass% KSS were incorporated, the LOI value of PC was found to be 46, and class V-0 of the UL-94 test. Moreover, both the heat release rate and the total heat release of PC/KSS/1 mass% PSiN decreased compared with those of PC and PC/KSS systems. The microstructures observed by scanning electron microscopy and FTIR indicated that the surface of the char for PC/KSS/PSiN system hold a more cohesive and denser char structure when compared with the pure PC and PC/KSS system.     

Effects of common synergistic agents on intumescent flame retardant polypropylene with a novel charring agent

In this article, the laboratory-made poly (p-ethylene terephthalamide) (PETA) was used as a novel charring agent and it combined with ammonium polyphosphate (APP) to prepare the intumescent flame retardant (IFR). For improving the flame-retardant efficiency of IFRs on polypropylene (PP), several general synergistic agents, such as common zinc oxide (Com-ZnO), nanometer structural zinc oxide (Nano-ZnO), zeolite 4A, and aluminum hypophosphite(Al(H₂PO₂)₃), were added in composites of PP/IFR, and the synergistic effect was investigated by the limited oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TG), thermogravimetry-fourier transform infraredspectroscopy (TG-IR) test, and scanning electron microscopy (SEM). It indicated that the flame retardancy was significantly enhanced in terms of prompting the char formation of PETA and interaction between APP and synergistic agents. Overall, Al(H₂PO₂)₃ was the most effective synergistic agent among them. TG-IR analysis showed that the addition of Al(H₂PO₂)₃ could delay the release of NH₃, and make the release of NH₃ more smooth, which was useful to form a dense char. SEM presented that compact, continuous and good intumescent charring layers were observed in all PP/IFR systems with synergistic agent.     

Synthesis of Methyl N‐Aryl Oxamate Using Soluble Polymer Support

A variety of methyl N‐aryl oxamates were synthesized using poly(ethylene glycol) (PEG) as a soluble polymer support and a monoproctection group with excellent yields.     

Conductive 2D Metal-organic Framework (Co,NiCo, Ni) Nanosheets for Enhanced Non-enzymatic Detection of Urea

2D metal-organic framework (MOF) has potential applications in electrocatalysis owing to fast mass transfer, charge transfer and large specific surface area. Here, we had prepared three conductive 2D MOF based on Ni, NiCo and Co in a simple and rapid way. The 2D nanostructure of MOF was confirmed by SEM and TEM. The chemical composition was studied by XRD, Raman and XPS spectrum. The electrochemical oxidation and detection was investigated through cyclic voltammetry and current-time method. Their sensing performance for urea was determined by varying oxidation potentials and metal sites. The non-enzymatic Ni-, NiCo- and Co-MOF sensors had good catalytic activity for urea. Compared with NiCo- and Co-MOF, Ni-MOF had a wider linear range (0.5–832.5 μM), high sensitivity (1960 μA mM⁻¹ cm⁻²), low detection limit (0.471 μM), and fast response time. The sensors had well repeatability, reproducibility, and selectivity to specific interfering species. Furthermore, Ni- and NiCo-MOF modified electrode was also applied to detection of milk samples. The results showed that the recovery was satisfactory, which further confirmed the effectiveness of non-enzyme sensor. In general, the highly-sensitive 2D Ni- and NiCo-MOF modified electrode has great potential as nonenzymatic urea sensors for real samples detection in hydrogen energy, clinical diagnostics, and environmental protection, et al.     

Large Hexagonal Bi‐ and Trilayer Graphene Single Crystals with Varied Interlayer Rotations

Bi‐ and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high‐quality large‐size bi‐ and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 μm pyramid‐like hexagonal bi‐ and trilayer graphene single‐crystal domains on Cu foils using chemical vapor deposition is reported. The as‐produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier‐transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first‐principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations.     

Optimized Fluorescent Probe for Specific Imaging of Glutathione S‐Transferases in Living Cells and Mice

GSTP1 has been considered to be a marker for malignancy in many tissues. However, the existing GST fluorescent probes are unfavorable for in vivo imaging because of the limited emission wavelength or insufficient fluorescence enhancement (six‐fold). The limited fluorescence enhancement of GST fluorescent probes is mainly ascribed to the high background signals resulting from the spontaneous reaction between GSH and the probes. In this work, a highly specific GST probe with NIR emission has been successfully developed through optimization of the essential unit of the probe to repress the spontaneous reaction. The novel GST probe exhibits over 100‐fold fluorescence enhancement upon incubation with GSTP1/GSH and high selectivity over other potential interference. In addition, the probe has been proved to be capable of tracking endogenous GST in A549 cells. Finally, the in vivo imaging results demonstrate that the probe can be used for effective imaging of endogenous GST activity in subcutaneous tumor mouse with high contrast.     

Temperature Dependence of the Mössbauer Effect on Prussian Blue Nanowires

Highly ordered Prussian blue nanowires with diameter of about 50 nm and length up to 4 m have been fabricated by an electrodepositing technology with two-step anodizing anodic aluminum oxide films. The Mössbauer spectra taken between 15 and 300 K indicate that the hyperfine parameters decrease as the temperature increases. The temperature dependence of the quadrupole splitting, the isomer shift and the spectra area are discussed. A decrease of Debye temperature for Prussian blue nanowires was found with respect to that of Prussian blue bulk.