In vivo solid phase microextraction sampling of human saliva for non-invasive and on-site monitoring

On-site sample preparation is an analytical approach based on direct sampling from the system under investigation. It has the advantage of combining sampling and sample preparation into a single step, thus generally is fast, minimizes the potential sources of error and eliminates the risks for analytes instability. For such analysis solid phase microextraction in thin film geometry (TF-SPME) can provide robust and convenient in vivo sampling, offering in the same time faster analysis and higher extraction recovery (i.e., better sensitivity) due to large surface to volume ratio.     

发光可调Au:ZnCdS合金量子点的水相合成

以巯基丙酸作为配体,在水溶液中合成了发光位置在495~583 nm可调的Au∶Zn Cd S合金量子点,研究了掺杂含量、Zn/Cd比和p H等对量子点光学性质的影响。对预提纯的Au∶Zn Cd S核量子点进行Zn S包覆,量子点表面的缺陷被有效去除,发光效率明显提高。利用X-射线粉末衍射、透射电子显微镜对其结构和形貌进行了表征。     

铁脂质体/水分配系数测定及影响因素考察

基于PAF-301分子模型通过Li 掺杂或B取代等模式设计了几种新型多孔芳香骨架(PAFs)材料, 采用量子力学和分子力学方法对新材料的储氢性能进行研究. 由量子力学计算得到了不同分子片段与H₂之间的结合能, 并结合DDEC方法计算了各分子片段的原子电荷分布. 利用巨正则蒙特卡洛(GCMC)模拟方法计算了77和298 K下H₂在不同PAFs材料中的吸附平衡性质. 结果表明, H₂直接与苯环的结合能较低, 但掺杂Li 原子能够提高H₂与六元环的结合能, 同时Li 原子体现出较高的正电性质, B原子取代苯环中的两个C原子后, 使得原有C原子电负性增强; 77 K下PAF-301Li 具有最高的储氢性能, 而PAF-C₄B₂H₄-Li₂-Si 和PAF-C₄B₂H₄-Li₂-Ge体现出较好的常温储氢性能, 各种材料的常温储氢性能远低于其低温储氢性能. 通过77 K下H₂在PAFs材料中的等位能面分布和吸附平衡质心密度分布对H₂在PAFs 材料中的优先吸附位置进行分析, 发现在PAF-301 和PAF-301Li 骨架中, 由于中心能量较低的等位能区域范围较宽, H₂在其中存在四个明显的吸附高密度分布区域, 而其它三种PAFs晶胞中心能量较低的等位能区域范围较窄, 使得H₂在其中只存在两个明显的吸附高密度分布区域.     

Electrochemical properties of niobium and phosphate doped spherical Li-rich spinel LiMn2O4 synthesized by ion implantation method

Spherical Li-rich lithium manganese oxide(LMO) spinel material was synthesized by an ion implanted method assisted by polyalcohol doped with Niobium and Phosphate simultaneously.The material was characterized by scanning electron microscopy,X-ray diffraction and BET specific surface area analysis.The electrochemical performances were investigated with galvanostatic techniques and cyclic voltammetry.The synthesis process was investigated with TG/DSC.The results show that the lithium ion can be immersed into the pore of manganese dioxide at a low temperature with the ion implanted method.The prepared materials have a higher discharge capacity and better crystallization than those prepared by solid phase method.The doped Nb can improve the capacity of the Li-rich LMO spinel and reinforce the crystal growth along(111) and(400) planes.The crystal grains show circular and smooth morphology,which makes the specific surface area greatly decreased.Phosphate-doped LMO spinel exhibits good high-rate capacity and structure stability.The prepared Li_(1.09)Mn_(1.87)Nb_(0.031)O_(3.99)(PO_4)_(0.021)delivers a discharge capacity of 119mAhg~(-1) at 0.2C(1C=148mAg~(-1)) and 112.8 mAhg~(-1) at 10 C,the discharge capacity retention reaches 98% at 1 ℃ after 50 cycles at 25 ℃ and 94% at 55 ℃.     

Modifications on reduced titanium dioxide photocatalysts: A review

A large variety of reduced titanium dioxide (TiO_2-x) materials have been reported recently. Reduced TiO₂, usually resulting from the removal of oxygen atoms or hydrogen incorporation, is proved to be efficient for achieving highly photocatalytic performance including photodegradation of organic compounds, hydrogen generation from water splitting, CO₂ reduction for CH₄ evolution, solar cells, etc. To further improve the properties and activities of TiO_2-x, a combination of the Ti³⁺ self-doping and other traditional modifications like nonmetals doping has been proposed in the past decades. This paper provides a general and critical review on the further modifications on reduced TiO₂ samples, including non-metal elements (N, B, S, F and I) doping, noble-metal (Au, Pt, Pd and Ag) and iron-group metal (Fe, Co and Ni) grafting, metal oxide compositing, carbon (nanotubes and graphene) and carbon-based-material compositing, special facets exposure (mainly dual {001}-{101} and {111}-{110} facets) of TiO_2-x and ordered structure controlling of TiO_2-x. These modifications enhance the physical and/or chemical properties of the reduced TiO₂, or create new features for the modified TiO_2-x samples, which finally leads to the enhancement of photocatalytic performance. Key examples such as N-doping, Au grafting and graphene-based compositing are discussed carefully, and the mechanisms for solar light enhancement, electron transfer and charge separation are also investigated. Finally, some challenging issues on TiO_2-x catalysts are also proposed to encourage new approaches for preparation of TiO_2-x catalysts with efficiently photocatalytic performance.     

Analytical methods for anti-doping control in sport: anabolic steroids with 4,9,11-triene structure in urine

Doping control in sport is mandatory to detect and to control the use of prohibited substances. Due to the growing number of targets, the analysis of doping compounds and their metabolites is carried out using established screening methods. However, detection of anabolic steroids with 4,9,11-triene structure in urine is problematic, so it is necessary to improve the methods.We review the state of the art in doping-control analysis of 4,9,11-trien-3-one steroids, providing an overview of the screening and confirmatory methods developed for these analytes in human urine. First, we review chromatographic techniques. We discuss difficulties in the derivatization of those compounds prior to gas chromatography analyses. In recent years, liquid chromatography has been the preferred technique in drug testing in sport, due to the reduced sample pre-treatment, improved limits of detection and comprehensiveness. We also report on advances and limitations of immunochemical techniques for the analysis of this group of substances.     

Enhanced Electrocatalytic Performance of Anthraquinonemonosulfonate‐Doped Polypyrrole Composite: Electroanalysis for the Specific Roles of Anthraquinone Derivative and Polypyrrole Layer on Oxygen Reduction Reaction

To analyze the specific roles of anthraquinone‐2‐sulfonate (AQS) and polypyrrole (PPy) layer on oxygen reduction reaction (ORR), the electrocatalytic reduction of oxygen was investigated on the AQS/PPy composite modified graphite electrode. Results show that the enhanced electrocatalytic performance is attributed to the excellent electrocatalytic activity of the immobilized AQS functional groups to mediate two‐electron reduction of O₂ to H₂O₂. The PPy layer may not participate in ORR, but it can further catalyze the two‐electron reduction of H₂O₂ to produce H₂O in the potential range more negative than that the two‐electron reduction of oxygen proceeds efficiently on the AQS sites.     

Consequences of the formation of 3,4-dimethyl-5-phenyl-1,3-oxazolidine on the analysis of ephedrines in urine by gas chromatography and a new method for confirmation as N-trifluoroacetyl-O-t-butyldimethylsilyl ether derivatives

The compound 3,4-dimethyl-5-phenyl-1,3-oxazolidine can appear as an artifact during the gas chromatographic analysis of ephedrines. Its presence is a risk for doping control and forensic analyses. An evaluation about the consequences of its formation showed the possibility of a false positive for ephedrine, a false negative for pseudophedrine and increased uncertainty in the quantitative approach. Misinterpretations can be avoided with the observation of fragments m/z 56 and 71 in the ephedrine mass spectrum during GC-MS analysis and also by the formation of N-TFA-O-TBDMS derivatives prior to GC analysis. These N-TFA-O-TBDMS derivatives lead to an increase in the number and mass of diagnostic ions, meet the identification criteria, and provide an improvement in chromatographic resolution, allowing the separation of the ephedrines.     

A fast, comprehensive screening method for doping agents in urine by gas chromatography-triple quadrupole mass spectrometry

The use of performance enhancing drugs in sports is prohibited. For the detection of misuse of such substances gas chromatography or liquid chromatography coupled to mass spectrometry are the most frequently used detection techniques. In this work the development and validation of a fast gas chromatography tandem mass spectrometric method for the detection of a wide range of doping agents is described. The method can determine 13 endogenous steroids (the steroid profile), 19-norandrosterone, salbutamol and 11-nor-Δ9-tetrahydrocannabinol.9carboxylic acid in the applicable ranges and to detect qualitatively over 140 substances in accordance with the minimum required performance levels of the World Anti-Doping Agency in 1ml of urine. The classes of substances included in the method are anabolic steroids, β2-agonists, stimulants, narcotics, hormone antagonists and modulators and beta-blockers. Moreover, using a short capillary column and hydrogen as a carrier gas the run time of the method is less than 8min.     

Ti和Al共掺杂ZnS的电子结构和光学性质

基于密度泛函理论的第一性原理研究Ti和Al单掺杂和(Ti,Al)共掺杂ZnS的能带结构、电子态密度分布、介电函数、光学吸收系数,分析了掺杂后电子结构与光学性质的变化.计算结果表明:掺杂后禁带中引入了新的杂质能级,费米能级进入导带.掺杂改变了ZnS晶体的导电特性,使它表现出金属特性,导电性能增强;与纯净ZnS相比,Ti单掺杂和(Ti,Al)共掺杂ZnS的吸收边均出现明显的红移,且在1.79eV左右出现了一个新峰;而Al单掺杂ZnS的吸收边则发生明显的蓝移,且不产生新的吸收峰.