三维荧光等高线特征谱及其应用研究

用图像信息统计法,得到了三维荧光等高线指纹图谱在发射波长方向和激发波长方向的1对特征谱以及1个沿发射波长方向并带有激发波长信息的特征谱.基于3种特征谱,对花生油、调和油和芝麻油的29个食用植物油样本进行了模式识别,结果表明:3种特征谱均能以数值集的形式描述物质的荧光性质,具有特征性和可计算性;数据客观,识别结果准确.将现代的数值分析技术与3种特征谱结合,不仅可实现物质的分类与鉴别,还可揭示化学变化过程中物质结构变化的客观规律.     

基于聚类分析对易燃液体塑料容器盖的光谱检验

将光谱分析方法与聚类方法相结合,对38个模拟案件环境的纵火现场助燃剂塑料容器盖样本进行X射线荧光光谱分析,根据元素种类将38个样本分为6组,建立了一种无损快速检验纵火现场物证的光谱分析方法。使用最短距离聚类法,以欧氏距离作为度量区间表示样本间亲疏关系,进行系统聚类分析,同时使用K-Means快速聚类法与t检验验证聚类效果。结果表明,38个样本分为6组时效果最好。并将各类的样本观测点在Fisher判别空间中的分布和位置情况绘出,与使用元素种类进行分类结果一致,为确定火灾案件性质,侦破案件线索提供了理论依据。     

基于三维荧光光谱的乳制品脂氧化判别方法

为快速、无损判别乳制品脂氧化程度,提出了利用乳制品三维荧光光谱的氧化水平进行判别的方法。该方法用平行因子分析对荧光矩阵进行分解,用载荷向量组确定脂氧化过程中的光敏成分,用不同成分得分向量对样本进行聚类,并建立了不同氧化水平样本的偏最小二乘判别模型。实验采集不同存储环境下氧化程度各异的酸奶样本,找出了核黄素等荧光团在脂氧化过程中的变化规律,选取得分向量建立偏最小二乘判别模型对不同存储阶段氧化程度各异的样本判别分类,其特异度和灵敏度达88.9%以上,验证了该法对评判乳制品脂氧化水平的有效性。     

近红外荧光染料的结构、性质及生物荧光成像应用

近红外荧光生物成像技术由于具有深的组织穿透性、低背景荧光干扰、最小生物样本光损伤等特点引起人们越来越多的关注。开发高荧光效率、低毒性的近红外荧光染料是近红外荧光成像技术发展的关键所在。本文综述了五类主要的有机近红外荧光染料(菁类、BODIPY类、罗丹明类、方酸类、卟啉类)的研究进展,重点分析其结构与光学性质等构效关系,为近红外荧光染料的设计和制备提供指导。另外,总结了有机近红外荧光材料功能化修饰的主要方法以改善生物相容性、靶向性能等,最后对近红外荧光染料存在的主要问题以及未来的热点方向进行了分析和展望。     

X射线荧光光谱结合聚类分析对橡胶轮胎的检验

应用X射线荧光光谱结合系统聚类分析对30种不同的橡胶轮胎样本进行检验研究。利用X射线荧光光谱仪对橡胶轮胎中的主要元素及其含量进行测定,根据测定结果使用聚类分析对样本进行分类。选择最长距离法作为类与类之间距离的定义方法,采用平方欧式距离作为度量区间描述样品间亲疏程度进行系统聚类,最终将30个样本分为12类。该方法简单易行,分类结果可靠且无损轮胎样本,为实际案件的橡胶轮胎检验提供了一种检验思路。     

基于三维荧光特性的汽油聚类分析

应用三维荧光光谱法研究了90#、93#及97#3种汽油纯样品以及它们的相互掺杂样品的荧光特性。选取激发波长(λex)为330nm,发射波长(λem)在340～500nm间的荧光强度数据,用主成分聚类分析法作了研究。结果表明:所得的荧光数据分为三类,属90#汽油样品的数据为一类,处于第Ⅰ象限中;属97#汽油样品为第二类,处于第Ⅲ象限;属93#汽油样品为第三类,处于第Ⅳ象限。在第Ⅰ及第Ⅳ象限中的荧光数据又分为二类,一类为纯品油样,另一类为混杂油样。因此,根据聚类分析结果可方便地对不同标号的汽油加以区别。而且根据纯品汽油样品与混杂油样品的试验点之间的距离可推测油样中混杂组分量的多少。     

城市污水处理过程中有机污染物三维荧光特性的变化规律

采用三维荧光光谱法研究了城市污水处理过程中溶解性有机物的三维荧光特性变化规律。研究结果表明,生活污水中荧光类溶解性有机物主要以类蛋白有机物、UV腐殖质和可见腐殖质为主;污水生物处理前后特征荧光峰中心位置和强度均发生明显的改变,表明污水中有机物的相对组成和含量随生物处理过程而变化。三维特征荧光参数可以反映污水处理过程中污染物的种类、性质和含量变化等丰富信息。其测定迅速简便、灵敏度高,可用于污水处理效果的定性分析、定量评价,易于实现污水处理过程的实时在线监测,指导污水处理工艺的设计、运行、管理和控制。     

计算机模式识别法对关节变形强直性脊柱炎微量元素谱的研究

测定了关节变形强直性脊柱炎患者及健康人头发样本中的十五种微量元素含量,运用计算机模式识别技术研究两类样本的微量元素谱差异,选择Ca、Pb、Zn、Ti、Ni、Mg和Sr元素为特征参量,用马氏距离法对两类样本进行回判和预报,其准确率均高于92%,高维空间分类成功,表明两类人的微量元素谱确实存在明显差异。     

三维荧光光谱技术在溶解有机质-吸附态砷相互作用中的应用进展

溶解有机质使含砷矿物还原溶解是地下水中砷富集的因素之一,三维荧光光谱技术可以进一步研究溶解有机质在砷迁移过程中的多重作用。本文从溶解有机质的组分、荧光特征指数以及荧光猝灭三个方面综述了三维荧光光谱技术在溶解有机质-砷相互作用中的应用。溶解有机质中的腐殖质组分会与砷形成络合物促进砷向地下水中迁移,还原性醌类充当电子穿梭体,增强了砷在水中的迁移性能。通过荧光指数、腐殖化指数和氧化还原指数可以判断溶解有机质的来源、腐殖化程度以及氧化还原态组分。地表水中砷浓度低,荧光指数高,腐殖化指数较低且以腐殖质物质为主;地下水中砷浓度和腐殖化指数较高,荧光指数低,且腐殖质的醌类部分较少,表明随着水中砷浓度升高,荧光指数成下降趋势,地表水中的腐殖质醌类充当电子穿梭加强了氧化铁的还原和砷迁移作用,促进地表水中的砷向地下水中迁移。砷和溶解有机质会形成砷-溶解有机质络合物,使溶解有机质发生荧光猝灭。pH值和金属离子会影响溶解有机质和砷的络合,但pH值主要影响溶解有机质自身的荧光强度,对砷-溶解有机质络合物的荧光强度影响不大,Ca²⁺能够明显增强溶解有机质-砷的类蛋白荧光。     

OFF沸石中锂离子在骨架外的分布及可接近性

对OFF沸石进行离子交换制备出NH4-OFF沸石,然后通过Li2CO3/NH4-OFF体系的固态反应制备了不同锂离子交换度的Li-OFF沸石。对吸附氮气和氧气的Li-OFF样品进行了7Li MAS NMR表征。研究发现,所有吸附氧气样品的部分7Li MAS NMR共振峰均发生了顺磁位移。通过对实验谱的拟合,得知Li-OFF沸石中的锂离子可分布在三类阳离子位置（A、B和C）上,对应于三个不同位移的谱峰。Li+离子并非等比例地进入三个可交换的位置,而是优先占据主孔道中的A位置,随着交换度的升高,位能较高的C和B位置上的Li离子占有率逐渐增加。在100％固态交换度样品中,Li+离子在不同离子位的占有率分别为17％(位置B)、29％(位置C)和54％(位置A)。其中,位置B是O2分子不可接近的,所以Li-OFF沸石中有83％的阳离子是可以接近的。     

Occurrence of Phthalates in Bottled Drinks in the Chinese Market and Its Implications for Dietary Exposure

Ubiquitous occurrences of phthalic acid esters (PAEs) or phthalates in a variety of consumer products have been demonstrated. Nevertheless, studies on their occurrence in various types of bottled drinks are limited. In this study, fifteen PAEs were analyzed in six categories of bottled drinks (n = 105) collected from the Chinese market, including mineral water, tea drinks, energy drinks, juice drinks, soft drinks, and beer. Among the 15 PAEs measured, DEHP was the most abundant phthalate with concentrations ranging from below the limit of quantification (LOQ) to 41,000 ng/L at a detection rate (DR) of 96%, followed by DIBP (DR: 88%) and DBP (DR: 84%) with respective concentration ranges of below LOQ to 16,000 and to 4900 ng/L. At least one PAE was detected in each drink sample, and the sum concentrations of 15 PAEs ranged from 770 to 48,004 ng/L (median: 6286 ng/L). Significant differences with respect to both PAE concentrations and composition profiles were observed between different types of bottled drinks. The median sum concentration of 15 PAEs in soft drinks was over five times higher than that detected in mineral water; different from other drink types. Besides DEHP, DBIP, and DBP, a high concentration of BMEP was also detected in a tea drink. The estimated daily dietary intake of phthalates (EDI_drink) through the consumption of bottled drinks was calculated based on the concentrations measured and the daily ingestion rates of bottled drink items. The EDI_drink values for DMP, DEP, DIBP, DBP, BMEP, DAP, BEEP, BBP, DCP, DHP, BMPP, BBEP, DEHP, DOP, and DNP through the consumption of bottled mineral water (based on mean concentrations) were 0.45, 0.33, 12.5, 3.67, 2.10, 0.06, 0.32, 0.16, 0.10, 0.09, 0.05, 0.81, 112, 0.13, and 0.20 ng/kg-bw/d, respectively, for Chinese adults. Overall, the EDI_drink values calculated for phthalates through the consumption of bottled drinks were below the oral reference doses suggested by the United States Environmental Protection Agency (U.S. EPA).     

Simultaneous Determination of Caffeine and Pyridoxine in Energy Drinks using Differential Pulse Voltammetry at Glassy Carbon Electrode Modified with Nafion®

A new voltammetric method for simultaneous determination of caffeine and pyridoxine present in different types of commercial energy drinks has been developed. This electroanalytical method is based on anodic oxidation of these biologically active nitrogen‐containing heterocycles at glassy carbon electrode covered with thin layer of sulfonated fluoropolymer Nafion® using differential pulse voltammetry in 0.1 M Britton‐Robinson buffer of pH 4.5 at potential step 5 mV, potential amplitude 70 mV, and scan rate 50 mV/s. Linear ranges for caffeine and pyridoxine determination were 63.1–600 μM and 7.5–200 μM with the detection limits of 18.9 and 2.2 μM, respectively. It was validated using high‐performance liquid chromatography with spectrophotometric detection. Obtained results have shown that voltammetric approach is very simple and low‐cost analytical method which can be used for routine determination of caffeine and pyridoxine in energy drinks.     

掺Tb3+聚醋酸乙烯乳液的制备及性质研究

在PVAc乳液聚合过程,将一定比例的三氯化铽(TbCl3)溶液与醋酸乙烯(VAc)单体同步滴入聚合体系,获得掺Tb3+ 离子的PVAc乳液, 研究Tb3+离子对PVAc乳液性能的影响。研究表明,Tb3+ 离子对PVAc的颗粒形貌、大小及其质量指标影响不大,但对发光性能有一定的影响,即掺Tb3+ 离子的PVAc会产生很强的Tb3+ 离子特征荧光,且随Tb含量的提高,其荧光强度随之增强,无荧光浓度猝灭现象。     

Enzyme digestion of entrapped single-DNA molecules in nanopores

The real-time digestion of entrapped single-DNA molecules by λ-exonuclease in nanoporous alumina membranes was observed using an epifluorescence microscope. The alumina membrane provides pL (∼10⁻¹² L) containers for confining single-DNA molecules without immobilization. When one end of the DNA molecule was inserted into a nanopore, it was possible to monitor the digestion process outside, near and inside the pore, where the individual DNA molecules exhibited different characteristic digestion modes. The digestion rates calculated from the decrease in fluorescence intensity showed different values according to the location of the individual molecules. Entrapment rather than immobilization allows the DNA strand to be fully exposed to the enzyme and the reaction buffer. These results confirm that the enzymatic digestion of DNA molecules is affected by their three-dimensional (3D) environment.     

原位聚合法制备透明聚苯乙烯的表征及其荧光性质研究

以极性较小的三异丙氧基铽为原料,选择与铽离子发光相匹配的乙酰丙酮为有机配体掺杂于苯乙烯（St）／少量的甲基丙烯酸甲酯（MMA）的混合单体中,通过原位本体聚合直接得到一类改性聚苯乙烯材料。并用红外光谱和紫外光谱表征其结构。可见光透过曲线表明这类改性聚苯乙烯材料具有高铽含量、高透过率的特点,用荧光光谱表征它们的荧光性能,结果表明：该材料在高铽含量下仍能发射很强的Tb3＋离子的特征荧光,未出现明显的荧光猝灭现象。     

Characterization of Polypropylene in Dibutoxymethane by High-Temperature Gel Permeation Chromatography with Triple Detection

This study presents the possibility of replacing the 1,2,4-trichlorobenzene (TCB) recommended by ASTM D 6474 for the analysis by gel permeation chromatography (GPC) of polypropylenes with dibutoxymethane (DBM, butylal), a halogen-free and less toxic solvent. The molecular weight distributions as well as the K and alpha parameters of the Mark-Houwink-Sakurada equation were measured for different types of commercial polypropylene samples solubilized in TCB and DBM, using a GPC system with triple detection (light scattering, differential refractive index, and viscometer). For the analyzed resins, covering typical applications of polypropylene, the GPC method in DBM provided results similar to those obtained in TCB.     

Catalytic Kinetics of Different Types of Surface Atoms on Shaped Pd Nanocrystals

To understand the catalytic properties or roles of different types of surface atoms on metal nanocatalysts, the catalytic kinetics and dynamics of the different types of surface atoms (plane and edge) were revealed for the first time by a statistical quantitative deconvolution of observables obtained from traditional single‐molecule nanocatalysis of Pd nanocrystals.It was found that the edge and plane of Pd nanocubes show similar size‐dependent product formation processes, but inverse product dissociation processes. This work helps push the traditional single‐molecule nanocatalysis method towards the sub‐particle level.     

两种不同光谱类型的R-藻红蛋白的荧光性质研究

红藻中的R-藻红蛋白(R-PE)依照其吸收光谱可分为两种不同的光谱类型,即“双峰型”和“三峰型”。本文通过对不同pH条件下的R-PE的荧光光谱及荧光寿命的研究,发现“三峰型”R-PE的pH稳定范围较“双峰型”R-PE大。在R-PE浓度对荧光光谱的影响实验中,随着蛋白浓度的增加,荧光峰位置逐渐红移。荧光寿命逐渐增大,荧光强度先行增加而后减弱。用碘离子对其荧光进行猝灭,随着碘离子浓度的增大,荧光强度逐渐降低,荧光寿命逐渐缩短,并服从Stem-Volmer规则。