聚甲基丙烯酸单层保护金纳米粒子选择性检测Pb2+

以聚甲基丙烯酸单层保护的金纳米粒子(GNPs)作为传感器, 实现了水溶液中Pb²⁺的选择性循环检测.先采用柠檬酸钠还原法获得尺寸均匀的GNPs, 再通过具有硫醇端基的聚甲基丙烯酸与金的强耦合作用, 获得了聚甲基丙烯酸单层保护的金纳米粒子(PMAA-@-GNPs).动态光散射、紫外-可见吸收光谱及透射电子显微镜表征证实了其单层结构.在Pb²⁺的诱导下, PMAA-@-GNPs溶液颜色从酒红色变为紫色并可肉眼识别.透射电子显微镜结果证实, 这种变化是由于Pb²⁺交联羧基使聚合物发生收缩, 并诱导GNPs的聚集所致.对比Pb²⁺与Hg²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Na⁺, Ni²⁺, Fe³⁺, Cd²⁺, K⁺和Fe²⁺溶液颜色的变化, 证实此体系具有一定的选择性.用EDTA可夺取交联的Pb²⁺, 使PMAA-@-GNPs 的吸收峰恢复并可用于循环检测Pb²⁺.     

Pb2+促进乙醇氧化C―C键断裂的在线电化学透射红外光谱研究

近些年来,直接乙醇燃料电池(DEFC)凭借其能量密度高、绿色环保、毒性低等诸多优点受到了广泛关注,相关的机理研究重点关注的是如何高效地催化乙醇C―C键的断裂。本文通过建立电化学在线透射红外方法,对碱性体系下Pb²⁺对Pt催化乙醇氧化反应(EOR)的影响进行了研究。结果发现,在不同温度、催化剂载量和电势条件下,Pb2+的加入都有利于Pt催化EOR活性的提高,同时能够提高乙醇氧化电流的稳定性。我们利用电化学在线透射红外光谱(ETIRS)方法对Pt催化EOR的反应产物进行了检测,发现Pb²⁺存在时产物碳酸根的电流效率明显高于Pb²⁺不存在时的结果,这一结果说明了Pb²⁺存在下Pt催化EOR中C―C键断裂比例的提高可能是反应活性提高的重要原因。     

改性氧化石墨烯去除重金属离子的分子动力学模拟

通过硅烷化反应在氧化石墨烯(Graphene oxide, GO) 表面嫁接螯合官能团N-(三甲氧基硅丙烷)乙二胺三酸(EDTA-Si), 得到改性氧化石墨烯(GO-EDTA), 采用分子动力学模拟在分子水平上研究了Pb²⁺在GO-EDTA 表面的动态吸附分布、 构象及动力学性质, 比较了Pb²⁺和单价Na⁺离子在氧化石墨烯上的吸附行为, 模拟了GO-EDTA与Ca²⁺相互作用, 与Pb²⁺的吸附行为进行了对比. 模拟结果表明, Pb²⁺和Na⁺的吸附位点是GO-EDTA 体系中的羧基, 而非氧化石墨烯表面的羟基; Pb²⁺和 Na⁺ 与羧基的吸附构象不同, 前者吸附构象以摩尔比2:1为主, 即两个羧基对一个Pb²⁺离子, 而后者更多倾向于摩尔比1:1的吸附模式, 即一个羧基对一个Na⁺离子; Pb²⁺离子相对于Ca²⁺和Na⁺离子, 形成的COO^--Pb²⁺离子对构象越过的能垒最低, 但是破坏该离子对构象时能垒较高, 表明Pb²⁺离子在氧化石墨烯膜上表现出良好的吸附性.     

蒙脱土表面键合配位体固相萃取填料的制备及其对重金属离子的吸附性能

通过酸洗、硅烷偶联剂表面活化、键合苯甲酰异硫氰酸酯对蒙脱土进行改性,制得新型固相萃取(SPE)材料。 采用红外光谱、扫描电子显微镜、X射线光电子能谱表征了改性蒙脱土的结构和形貌。 考察了制备的SPE填料对水中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺的吸附性能,确定了最佳固相萃取条件,对6种金属离子吸附容量分别为10.83、11.92、12.67、10.43、10.01及10.54 mg/g。 通过SPE与电感耦合等离子体质谱联用测定了样品中As³⁺、Bi³⁺、Cu²⁺、Sb³⁺、Sn²⁺和Pb²⁺ 6种重金属离子的含量,检出限分别为0.024、0.013、0.075、0.037、0.011和0.064 μg/L。     

Pb2+和Zn2+对亲水型光敏热成像材料感光性能和存储稳定性能的影响

分别研究了Pb²⁺和Zn²⁺对以聚乙烯醇(PVA)为粘合剂的亲水型光敏热成像(PTG)材料的感光性能以及老化稳定性能的影响.实验结果表明,涂布液中加入Pb²⁺或Zn²⁺后,PTG材料的热显影灰雾和相对感光度均明显降低,并且随着离子加入量的增加,下降程度更加显著.另外,含有Pb²⁺或Zn²⁺的PTG材料在经过不同时间的老化后,与未老化PTG材料相比,其热显影灰雾缓慢增加,相对感光度也略有上升.     

丁二酸酐接枝纤维素纳米纤维膜及其重金属离子吸附

采用热致相分离(TIPS)法以三醋酸纤维素(TCA)为原料成功制备直径为(110±28)nm TCA多孔纳米纤维膜。将TCA纤维膜通过水解转化为纤维素(Cell)、接枝制备丁二酸酐接枝改性纤维素(Cell-g-SAA)膜。将Cell膜和Cell-g-SAA膜用于吸附水中Cu~(2+)、Pb~(2+),并对膜样品的吸附动力学、等温吸附和吸附热力学进行了研究。结果表明,二级动力学拟合和Langmuir模型更适合于该体系。与Cell膜相比,改性后Cell-g-SAA膜对Cu~(2+)和Pb~(2+)的最大吸附容量分别从51.73和34.29 mg/g增加到116.41和51.73 mg/g。纤维膜对Cu~(2+)、Pb~(2+)的吸附更趋近于单层吸附且化学吸附占主导地位。     

Conformation Changes of Enkephalin in Coordination with Pb2+ Investigated by Gas Phase Hydrogen/Deuterium Exchange Mass Spectrometry Combined with Theoretical Calculations

In this study, the effects of lead ions(Pb²⁺) on the conformations of leucine encephalin(LE) and methionine encephalin(ME) in gas phase were studied using hydrogen/deuterium exchange mass spectrometry(HDX-MS) and quantum chemistry theoretical calculations at the molecular level. The HDX-MS result revealed that the complexes with the monovalent compounds [LE+Pb–H]⁺ and [ME+Pb–H]⁺had a 1:1 stoichiometric ratio, and different HDX reactivates were observed in a follow of [ME+H]⁺>[LE+H]⁺>[LE+Pb–H]⁺> [ME+Pb–H]⁺. Combining the collision-induced dissociation energies of the complexes and their HDX results, it was found that the more stable the complex, the harder it was for HDX. In addition, the favo-rable conformations of the complexes were obtained by theoretical calculations, revealing that the similar coordination type with diffe-rent bond lengths was obtained. Then, the proton affinity(PA) values of the optimized complexes were calculated to interpret the HDX observations, indicating that the higher the PA values, the more difficult it was for HDX. Overall, the experiments and theoretical calculations revealed that Pb²⁺ could induce conformational changes of LE and ME, and generate ME into a more rigid conformation than LE. The results will prompt further fundamental investigations on the conformational properties of LE/ME in coordination with Pb²⁺.     

基于硫代黄素T诱导G-四联体构成的生物传感器检测铅离子

硫代黄素T(ThT)荧光分子在自由状态下荧光强度很弱, 通过在Tris-HCl缓冲液中加入Pb²⁺的适配体即富含G的DNA序列, 可与ThT荧光分子形成G-四联体结构, 使荧光信号迅速增强; 向溶液中加入Pb²⁺, Pb²⁺与其适配体有很好的结合特异性, 可生成更牢固的G-四联体结构, 使ThT分子被释放出来, 导致溶液的荧光强度降低, 基于此可检测溶液中的Pb²⁺离子. 实验中优化了缓冲溶液组成、 ThT荧光分子浓度、 Pb²⁺适配体浓度及反应时间等条件. 结果表明, 在10 mmol/L Tris-HCl(pH=8.3, 含2 mmol/L MgCl₂)缓冲溶液中, ThT荧光分子和Pb²⁺适配体的浓度分别为10 μmol/L和200 nmol/L, 反应10 min时, 随着溶液中Pb ²⁺浓度的增加, 荧光强度减弱. Pb²⁺浓度在20~1000 nmol/L范围内时, 荧光强度与Pb²⁺的浓度呈现良好的线性关系(R²=0.9941), 检出限为1 nmol/L. 实际水样测试结果表明, 该方法的回收率在98.8%~101.3%之间. 该传感器灵敏、 快速、 无需化学修饰荧光分子且成本低.     

钾离子浓度依赖的铅离子稳定G-四链体构型转化

已有研究普遍认为铅离子(Pb²⁺)诱导富G适体链形成的G-四链体(Pb²⁺-G4)比钾离子(K⁺)诱导富G适体链形成的G-四链体(K⁺-G4)更为稳定,因而Pb²⁺可以置换K⁺-G4中的K⁺,而且K⁺的存在不影响Pb²⁺-G4的稳定性。有趣的是本研究发现K⁺ (20 μmol∙L⁻¹–1 mmol∙L⁻¹)不仅可以诱导10 µmol∙L⁻¹ Pb²⁺稳定的T2TT(Pb²⁺-T2TT,杂合G4结构)发生构型转换,甚至还可取代Pb²⁺-T2TT中的Pb²⁺,形成K⁺稳定的T2TT (K⁺-T2TT,平行G4结构),最终转化形成的K⁺-G4结构与单独K⁺诱导富G适体链形成K⁺-G4的构型基本一致。随后,进一步考察了另外7条富G适体链,发现这一转化过程具有一定的普适性。该研究结果为理解G4构型转化以及内嵌离子交换提供了新的视角,也为拓展G4在生化分析和生物领域的应用提供了新的理论基础。     

离子强度对膨润土/木质素磺酸钠接枝丙烯酰胺-马来酸酐复合吸附树脂吸附Pb2+/Cu2+的影响

为揭示外加电解质离子强度对重金属离子吸附的影响规律与内在机制, 制备了膨润土/木质素磺酸钠接枝丙烯酰胺-马来酸酐复合吸附树脂(BLPAMA), 研究了外加电解质离子强度对BLPAMA吸附单一和二元Pb²⁺/Cu²⁺的影响规律, 以及有、无外加0.2 mol/L NaNO₃时BLPAMA对二元Pb²⁺/Cu²⁺的吸附等温线、吸附热力学及吸附动力学。 结果表明, 在单一Pb²⁺或Cu²⁺溶液中, 随离子强度增加, Pb²⁺和Cu²⁺吸附量降低;在二元Pb²⁺/Cu²⁺溶液中, 随离子强度增加, Pb²⁺吸附量降低而Cu²⁺吸附量提高。     

双水杨醛邻苯二胺柱前衍生-高效液相色谱法测定茶叶中的Pb~(2+)

建立了利用双水杨醛邻苯二胺希夫碱(SALOPHEN)作为衍生剂结合高效液相色谱(HPLC)测定茶叶中Pb~(2+)含量的方法。Hypersil ODS2 C18反相色谱柱(250 mm×4.6 mm,5μm)为固定相,甲醇-水(80∶20,v/v)为流动相,检测波长为226 nm,反应体系pH为10.0。结果表明,样品中Pb~(2+)的线性范围为0.1~30 mg/L,线性相关系数为0.998 8,检出限为0.01 mg/L,加标回收率为91.87%~96.96%。该方法具有较高的灵敏度和稳定性,适用于茶叶中Pb~(2+)的检测。     

Gamma coloration of mixed crystals of KCl–KBr doped with Pb

The amount of the first stage coloration in KCl_1−xBr_x doped with Pb²⁺ has been investigated as a function of the dose rate and impurity concentration. For a dose rate of 12.88 kGy/h, the F color center production was independent of the quantity of Pb²⁺, and varied according to the ratio KCl/KBr. At a proportion of 50% of each halogen the typical stages were observed. However, if the dose rate is less than 3.22 kGy/h, the coloration production depends on the quantity of Pb²⁺.     

A highly selective magnetic sensor with functionalized Fe/Fe3O4 nanoparticles for detection of Pb2+

A magnetic sensor for detection of Pb~(2+) has been developed based on Fe/Fe_3O_4 nanoparticles modified by3-(3,4-dihydroxyphenyl)propionic acid(DHCA). The carboxyl groups of DHCA have a strong affinity to coordination behavior of Pb~(2+) thus inducing the transformation of Fe/Fe_3O_4 nanoparticles from a dispersed to an aggregated state with a corresponding decrease, then increase in transverse relaxation time(T_2) of the surrounding water protons. Upon addition of the different concentrations of Pb~(2+) to an aq. solution of DHCA functionalized Fe/Fe_3O_4 nanoparticles(DHCA-Fe/Fe_3O_4 NPs)([Fe] = 90 mmol/L), the change of T_2 values display a good linear relationship with the concentration of Pb~(2+) from 40 μmol/L to 100 μmol/L and from 130 μmol/L to 200 μmol/L, respectively. Owing to the especially strong interaction between DHCA and Pb~(2+), DHCA-Fe/Fe_3O_4 NPs exhibited a high selectivity over other metal ions.     

Retention behavior of transition metals on a bifunctional ion-exchange column with oxalic acid as eluent

The common eluents used with a bifunctional ion-exchange column (IonPac CS5A) for separating transition metals are pyridine-2,6-dicarboxylic acid and oxalic acid (Ox). When Ox is used, cadmium and manganese co-elute. Although much research has been done to overcome the Cd²⁺–Mn²⁺ co-elution problem, the role of lithium hydroxide in separating the transition metals has received little attention. In this study, it is found that when the Ox concentration is higher than 35 mM, Cu²⁺ elutes after Pb²⁺ and Ox plays a predominant role in the retention behavior of the seven metals. When Ox concentration is lower than 35 mM especially when its concentration (25 mM) is half of the usually used standard concentration (50 mM), Cu²⁺ elutes before Pb²⁺, and at the same time, Mn²⁺and Cd²⁺ can also be baseline separated. Lithium hydroxide plays a predominant role in the separation of the metals separated by cation exchange. So, lithium hydroxide is used to adjust the pH of the eluent. The use of an isocratic elution (25 mM Ox/LiOH/2 mM Na₂SO₄, pH 3.88) allows the separation of seven metals (Cu²⁺, Pb²⁺, Co²⁺, Mn²⁺, Cd²⁺, Zn²⁺ and Ni²⁺) in a single run. The effects of inorganic modifiers such as NaNO₃, Na₂SO₄ and Na₄P₂O₇ on retention behavior of the metals are also investigated.     

Electrochemical sensor for Cd2+ and Pb2+ detection based on nano-porous pseudo carbon paste electrode

An electrochemical sensor based on self-made nano-porous pseudo carbon paste electrode (nano-PPCPE) has been successfully developed, and used to detect Cd²⁺ and Pb²⁺. The results showed that the electrodes can quantitatively detect trace Cd²⁺ and Pb²⁺, and with satisfied limit of detection, which has great significance in electrochemical analysis and detection.     

热剥离法制备石墨烯纳米片对Pb2+和Cd2+的吸附

石墨粉氧化后,在氮气气氛下,快速高温剥离制得石墨烯纳米片。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(HRTEM)、拉曼(Raman)光谱、傅里叶变换红外(FT-IR)光谱和氮气吸附-脱附等分析手段对石墨烯样品进行了表征。这些分析测试结果显示:石墨烯样品主要由很薄的1-4层石墨组成,呈褶皱状态,比表面积为628.5 m²·g^-1。研究了石墨烯吸附水溶液中的Pb²⁺和Cd²⁺的pH值、吸附时间、吸附温度和金属离子初始浓度等影响因素, Pb²⁺和Cd²⁺的最大吸附量分别为460.20和72.39 mg·g^-1。结果表明,热剥离法制得的高质量石墨烯纳米片可以作为一种高效的从水中去除Pb²⁺和Cd²⁺的吸附材料。     

Evaluation of dithiocarbamates and beta-diketones as chelating agents in supercritical fluid extraction of Cd, Pb, and Hg from solid samples

The use of four dithiocarbamates and three fluorinated β-diketones as potential chelating agents for three transition metal ions (Cd²⁺, Pb²⁺, and Hg²⁺) extracted from spiked sand and filter paper samples by supercritical fluid extraction (SFE) was investigated. The extractions were performed at 45°C and 250 atm for spiked sand samples and at 60°C and 200 atm for filter paper samples using supercritical carbon dioxide modified with 5% methanol. At 250 atm and using carbon dioxide modified with 5% methanol, the recoveries of Cd²⁺, Pb²⁺, and Hg²⁺ ions from spiked sand samples were 95% with lithium bis(trifluoroethyl)dithiocarbamate (LiFDDC) as the chelating agent; they ranged from 83–97% with diethylammonium diethyldithiocarbamate and from 87–97% with sodium di-ethyldithiocarbamate as chelating agents, and from 68–96% with trifluoracetylacetone, hexafluoroacetylacetone, and thenoylfluoroacetone as chelating agents. Ammonium pyrrolidinedithiocarbamate was not effective in the chelation SFE of Cd²⁺, Pb²⁺, and Hg²⁺ ions from either spiked sand or spiked filter paper samples under the extraction conditions used. Supercritical carbon dioxide alone gave consistently lower analyte recoveries than supercritical carbon dioxide modified with 5% methanol. The results suggest that the solubility of the metal chelate in the supercritical fluid plays a more important role than the solubility of the chelating agent in the supercritical fluid, as long as sufficient chelating agent is present in the fluid phase. Fluorination of the chelating agent, as in the case of LiFDDC, increases the solubility of the metal chelate, and subsequently enhances the extraction efficiency for the metal ions.     

巯基乙酸-纳米银比色传感快速检测水样中的Pb2+

利用巯基乙酸含S配位原子,能与纳米银形成Ag-S配位键吸附在纳米银表面,防止纳米银团聚,Pb²⁺的引入导致纳米银溶胶发生团聚现象,溶液的颜色由亮黄色变灰红色,由此建立了测定痕量Pb²⁺的比色方法。在优化的实验条件下,Pb²⁺的线性范围为0.1~5.0×10^-6mol/L (R²=0.9956),裸眼检出限为0.5μmol/L。此方法用于环境中Pb²⁺的检测,其回收率在90%~110%之间,RSD <2.5%。     

金属离子对溴碘化银乳剂微晶体的掺杂效应——Ⅱ. Pb2+的掺杂

应用常规感光测定法、电镜法、介电损耗仪和微波光导仪研究了Pb²⁺对卤化银乳剂微晶的掺杂效应。结果表明:Pb²⁺使乳剂的感光度降低,灰雾明显升高,而反差变化不大。由电子显微镜照片表明,Pb²⁺对乳剂微晶大小和形状影响不大,但是离子电导和微波光导数据显示出,Pb²⁺的掺杂使离子电导率降低0.15个对数单位,电子电导成倍降低。上述结果暗示:Pb²⁺对照相性能的影响不是由于乳剂微晶大小和形状的变化,可能由以下两个原因引起:(1)Pb²⁺起了深的电子陷阱作用,使光电子徙动路程缩短,影响潜影的形成效率,(2)Pb²⁺(或PbBr₂)成为复合中心,加速光电子与空穴的复合,催化显影过程。     

Adsorption Mechanism of Composite Whisker on Copper Ions and Lead Ions

A new kind of inorganic composite adsorbent based on chitin whiskers(CHW) and potassium tetratitanate whiskers(PTW) was synthesized via the thermal deposition to remove Cu²⁺ and Pb²⁺ from wastewater. CHW could be successfully coated on the surface of PTW when thermal treated 8 times. The adsorption process was better fitted with the Langmuir and Freundlich models. The adsorption process was more conformed to the Pseudo-second-order model. The results from XPS(X-ray photoelectron spectrum) further show that the adsorption mechanism between CHW-PTW and Cu²⁺, Pb²⁺ are both ion exchange and chemical adsorption. Thermodynamic parameters suggest that the adsorption processes are nonspontaneous. The adsorption of Cu²⁺ and Pb²⁺ is endothermic and exothermic, respectively.