Preparation of flower-like molybdenum disulfide for solid-phase extraction of N-nitrosoamines in environmental water samples

In this paper, a flower-like molybdenum disulfide material was prepared by hydrothermal method and was first used as adsorbents in the solid-phase extraction process for enriching N-nitrosoamines. Molybdenum disulfide exhibited three-dimensional petal-like microspheres with about 500 nm in diameter. The relevant analyte extraction and elution parameters (sample volumes, solution pH, washing solvents, elution solvents, and elution volumes) were optimized to improve the solid-phase extraction efficiency. The solid-phase extraction process coupled with high-performance liquid chromatography-tandem mass spectrometry for determining N-nitrosoamines in environmental water samples was established. The limits of detection were in the range of 0.01–0.05 ng/mL. The satisfactory recoveries (68.9–106.1%) were obtained at three different spiked concentrations (2, 5, and 8 ng/mL) in water samples, and the relative standard deviations were between 1.96 and 8.38%. This proposed method not only showed high sensitivity and good reusability but also provided a new adsorbent for enriching trace N-nitrosoamines in environmental water samples.     

Dual recognition strategy for ultra-sensitive fluorescent detection of Hg2+ at femto-molar level based on aptamer functionalized sulfur quantum dots

In the present study, a dual recognition strategy for ultrasensitive detection of Hg²⁺ was successfully developed for the first time based on aptamer functionalized sulfur quantum dots (Apt-SQDs). The developed Apt-SQDs not only retained the good fluorescence properties of quantum dots but also overcame the problem of poor selectivity of SQDs for heavy metal ions. This system used the dual recognition strategy, including the combination of S_x^2? and Hg²⁺ and T-Hg²⁺-T structures to excellently identify and capture Hg²⁺, and an ultrahigh sensitivity fluorescent aptasensor was fabricated. The fluorescent aptasensor had a good response to Hg²⁺ at concentrations ranging of 10^?15 to 10^?7 M with an ultralow limit of detection of 0.3 fM, and the response to other metal ions was far less than that to Hg²⁺. It was successfully applied to detect Hg²⁺ in nearby environmental water samples (tap water, lake water and river water) with a good recovery rate. Moreover, portable test papers that would be useful for Hg²⁺ monitoring in environmental water were designed. The dual recognition strategy not only achieves ultrasensitive fluorescent detection of Hg²⁺ but also provides a new insight into the further expansion of the application of SQDs.     

基于非靶向代谢组学的茄梨和红茄梨成熟期果皮代谢产物的差异分析

为了探究西洋梨品种茄梨及其红色芽变红茄梨成熟期果皮代谢产物差异,采用超高效液相色谱-质谱联用技术,对茄梨和红茄梨成熟期果皮进行非靶向代谢组学研究。通过主成分分析和正交偏最小二乘判别分析,构建了多变量统计分析模型,结合模型和变量重要性投影与最大差异倍数值,基于精确质量数、二级碎片以及同位素分布,使用PMDB(Plant Metabolome Database)数据库进行定性,筛选并鉴定出茄梨和红茄梨果皮中显著性变化(P<0.05, VIP(variable importance in project)≥1)的差异代谢物有83种,主要包括酚酸类、黄酮类和氨基酸类物质,涉及类黄酮代谢、氨基酸代谢、苯丙烷类代谢等代谢途径,其中53种物质含量上调,30种物质表达下调。通过KEGG(Kyoto Encyclopedia of Genes and Genomes)数据库进一步对差异代谢物质进行通路富集分析,差异代谢物主要分布在20条代谢途径中,P<0.05的代谢途径有6条,分别是类黄酮生物合成、黄酮和黄酮醇生物合成、苯丙烷生物合成、丁酸酯代谢、苯丙氨酸代谢、酪氨酸代谢。这些差异代谢物的变化可能是导致茄梨和红茄梨果皮色泽不同的原因。该研究从植物代谢组学角度初步揭示了茄梨和红茄梨成熟期果皮的代谢产物差异性。     

面向产出的高分子化学课程教学大纲的构建*

基于工程教育认证的核心理念,制定了面向产出的高分子化学课程教学大纲。与传统课程教学大纲不同,本大纲的课程目标是使学生具备推演、阐述、分析和研究高分子材料领域复杂工程问题的能力,体现以学生为中心、面向产出和持续改进的理念。课程教学内容既包含知识点又包含能力要求,强调课程知识点与学生能力达成的支撑关系。在课程考核部分,提出了分目标模块化的考核方法和评分标准,满足了工程认证可衡量、易操作的考核要求。     

SC-ICP-MS法测定金属元素的方法研究

为了使用单细胞电感耦合等离子体质谱(SC-ICP-MS)方法准确测定单个细胞中的铬(Cr)、锰(Mn)、铁(Fe)、铜(Cu)和锌(Zn)等多种内源性金属元素,该文基于动态反应池(DRC)模式对目标分析物的反应气流量和极杆抑制参数q(RPq)进行了优化,并研究了进样速度、细胞密度、驻留时间等因素对SC-ICP-MS检测的影响。分别采用细胞悬液直接进样、使用超声波探头使细胞悬液中的细胞破碎后进样和使用浓硝酸消解细胞后进样的ICP-MS测定结果对SC-ICP-MS定量结果的准确性进行验证分析。实验结果表明,可采用超声波破碎细胞的ICP-MS测定结果评估SC-ICP-MS测定的单细胞内Zn和Cu含量的准确性,采用酸消解细胞的ICP-MS检测结果验证单细胞内Fe和Cr的含量。缺少细胞标准物质时对SC-ICP-MS方法定量结果进行多角度验证是必要的。研究表明,使用SC-ICP-MS法可以较好地进行单细胞元素相关分析。     

Tailoring Pore Structure and Morphologies in Covalent Organic Frameworks for Xe/Kr Capture and Separation

As a rising star among porous solid materials, covalent organic frameworks(COFs) with excellent properties including but not limit to facilely controllable structure, high porosity, and multi-chemical functionality represent significant potential for efficient ¹²⁷Xe/⁸⁵Kr capture and separation. In this study, through tuning the length of the organic ligands, two-dimensional(2D) COF mate-rials with identical connection group but different pore properties, denoted as ATFG-COF and TpPa-COF with AA-stacking model and TpBD-COF with AB-stacking model were synthesized and tested for Kr and Xe adsorption for the first time. Adsorption measurements indicate that the narrower pore apertures and higher porosity are conducive for COF materials to capture Xe and Kr. Furthermore, the Henry's constant, isosteric heat of adsorption(Q_st), and ideal adsorbed solution theory(IAST) selectivity of ATFG-COF, the pore size of which is closest to the kinetic diameter of the Xe atom(0.41 nm) among 2D COF materials, were carried out based on the single component sorption isotherms. The results illustrate that the high isosteric heat values of Xe/Kr adsorption on ATFG-COF are 25 and 16 kJ/mol at room temperature, respectively. Henry's law predicts that the selectivity factor of Xe to Kr is 6.07, consistent with the adsorption selectivity(ca. 6) calculated based on the IAST.     

基于多肽识别的电化学生物传感技术

多肽具有分子量小、易于合成、生物兼容性好、稳定性高及序列灵活多样等优点。因此,多肽作为新型生物识别元件,已被广泛应用于生物传感器的构建。电化学分析灵敏度高、准确度好、设备简单、检测范围广且易于操作。本文介绍了基于多肽识别的电化学生物传感器技术,包括多肽的修饰与固定化、多肽与待测物的识别及检测原理;综述了近五年多肽电化学生物传感器对重金属离子、小分子、蛋白质、细菌和病毒的检测;展望了肽基电化学生物传感器的发展趋势。     

Cu-BTC及其衍生物在苯甲醇选择氧化反应中的催化活性

以硝酸铜和均苯三甲酸(BTC)为原料,水热合成了一种金属有机骨架化合物Cu-BTC,在水相中催化苯甲醇选择氧化反应,H2O2氧化剂,优化了Cu-BTC的晶化条件.70℃反应1 h,Cu-BTC(110C/24 h)上的苯甲醇转化率为75.4%、苯甲醛选择性83.5%,但反应后Cu-BTC骨架完全塌陷.在氮气中高温焙烧Cu-BTC,制得衍生物Cu@C,也用于催化苯甲醇氧化反应.结果表明:Cu@C催化剂重复使用5次,可维持较高的苯甲醇转化率,但苯甲醛选择性有所下降.用X射线衍射(XRD)、N2物理吸附(BET)、热分析(TG-DSC)、红外光谱(FTIR)、能量色散X射线光谱分析(EDX)等技术对催化剂进行了结构表征,发现:Cu@C在反应中生成的Cu2O促进了苯甲醛的深度氧化.     

Carbene tetrel-bonded complexes

An ab initio calculation has been carried for the carbene tetrel bonded complexes CH₃Y???CH₂ (Y = F, CN, NC, and NO₂), CH₃F???CZ₂ (Z = Cl and CH₃), XH₃F???CF₂ (X = C, Si, Ge, and Sn), SiF₄???CF₂, and XH₃F???NHC (N-heterocyclic carbene), where carbene is treated as a Lewis base and XH₃Y is a Lewis acid. Formation of the tetrel bond is mainly attributed to charge transfer from the lone pair on the C atom in the carbene toward the σ* X–Y orbital and also the σ* X–H one in the strong tetrel bond. The carbene tetrel bond is strengthened/weakened by the electron-withdrawing group in the tetrel donor/acceptor and enhanced by the methyl group in C(CH₃)₂. NHC forms a stronger carbene tetrel bond in XH₃F???NHC (X = Si, Ge, and Sn) where it exceeds that of the majority of H-bonds. Interestingly, the tetrel bond becomes stronger in the order of X = C < Ge < Sn < Si in XH₃F???NHC and the largest interaction energy occurs in SiH₃F???NHC, amounting to ?103 kJ/mol. The carbene tetrel bond can be strengthened by cooperative effect with the N???M interaction in trimers H₂C???CH₃CN???M (M = CH₃CN, HCN, ICN, SbH₂F, LiCN, and BeH₂) and has doubled in H₂C???CH₃CN???BeH₂.

     

Decoupled schemes for unsteady MHD equations. I. time discretization

In this article, a time discretization decoupled scheme for two‐dimensional magnetohydrodynamics equations is proposed. The almost unconditional stability and convergence of this scheme are provided. The optimal error estimates for velocity and magnet are provided, and the optimal error estimate for pressure are deduced as well. Finite element spatial discretization and numerical implementation are considered in our article (Zhang and He, Comput Math Appl 69 (2015), 1390–1406). © 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 956–973, 2017