Turn-on ratiometric fluorescent sensor for Pb detection

We report a ratiometric lead fluorescent sensor (LFS-1) with high affinity to Pb²⁺ that shows considerable selectivity over 12 other physiological related metal cations in aqueous media. Binding induces excimer formation, providing a highly sensitive ratiometric measure of lead concentrations.     

Selection of phage displayed peptides for the detection of 2,4,6-trinitrotoluene in seawater

We have selected for phage displayed peptides that showed specific binding to a 2,4,6-trinitrotoluene (TNT) derivative, 2,4,6-trinitrobenzene (TNB) in environmentally relevant conditions, and have integrated the selected phage into a continuous flow immunosensor platform for the detection of TNT. A library of 12 random amino acid peptides (12-mers) displayed on phage was panned against TNB coupled to the protein bovine serum albumin (BSA) in a solution of artificial seawater. Eight phage clones, seven of which share an identical amino acid sequence, bound selectively to TNB-BSA in artificial seawater as judged by enzyme-linked immunosorbent assay (ELISA). Addition of TNT, inhibited binding of the phage. Whole phage were labeled with the dye cyanine 5 (Cy5), and incorporated into a flow sensor platform. Labeled phage were loaded onto a TNB-affi-gel packed column, and a reproducible signal, at least five times greater than background, was observed on repeat injections of 10 mg/l TNT dissolved in seawater. This study presents one of the first examples of phage selection in a non-physiological medium, and the first demonstration that dye-labeled phage can be integrated into a continuous flow sensor.     

Colorimetric and fluorescent chemosensor for citrate based on a rhodamine and Pb complex in aqueous solution

In this paper we unveil a novel rhodamine compound based fluorescent chemosensor (1-Pb²⁺) for colormetric and fluorescent detection of citrate in aqueous solution. This is the first fluorescent chemosensor for citrate based on rhodamine compound. The comparison of this method with some other fluorescence methods for citrate indicates that the method can detect citrate in aqueous solution by both color changes and fluorescent changes with long emission wavelength. In the new developed sensing system, 1-Pb²⁺ is fluorescent due to Pb²⁺-induced fluorescence enhancement of 1. However, the addition of citrate may release 1 into the solution with quenching of fluorescence. The chemosensor can be applied to the quantification of citrate with a linear range covering from 1.0 × 10⁻⁷ to 5.0 × 10⁻⁵ M and a detection limit of 2.5 × 10⁻⁸ M. The experiment results show that the response behavior of 1-Pb²⁺ towards citrate is pH independent in medium condition (pH 6.0–8.0). Most importantly, the fluorescence changes of the chemosensor are remarkably specific for citrate in the presence of other anions (even those that exist in high concentration), which meet the selective requirements for practical application. Moreover, the response of the chemosensor toward citrate is fast (response time less than 1 min). In addition, the chemosensor has been used for determination of citrate in urine samples with satisfactory results.     

Probing Pb cation via the iridium based phosphorescent dye

We demonstrate the concept of Pb²⁺ cation sensing using the emissive Ir(III) complex (1) based on the associated decrease of room-temperature phosphorescence upon forming the 1:1 adduct 1-Pb²⁺. Complex 1 bears two cyclometalated N-phenyl pyrazoles with pyrazoles residing at the mutual trans dispositions as well as one 3,5-di(pyridyl) pyrazolate chelate. X-ray structural analyses on the adduct 1-Pb²⁺ confirm the key function of 3,5-di(pyridyl) pyrazolate as it forms chelate interaction with the metal analytes, while quenching of phosphorescent emission is probably due to the Pb²⁺ induced perturbation, which increases the intersystem crossing to another lower-lying triplet state for the host chromophore via an enhanced spin–orbit coupling.     

一步热解法制备Cu/Fe双金属生物炭复合材料及其高效吸附Pb2+性能

使用一步热解法制备了 Cu/Fe双金属生物炭复合材料(BC@Cu/Fe-X,X=3、5、10)和 Fe生物炭复合材料(BC@Fe)。考察了Cu掺杂量对BC@Cu/Fe-X吸附Pb²⁺的影响,确定最佳掺杂比例。结果显示BC@Cu/Fe-5吸附Pb²⁺性能最好。考察了吸附时间、Pb²⁺浓度、pH、背景离子、空气中老化等实验条件对 BC@Cu/Fe-5 吸附 Pb²⁺的影响。通过动力学、热力学数据拟合分析了BC@Cu/Fe-5吸附Pb²⁺的行为,利用X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、傅里叶变换红外光谱(FTIR)等表征手段解析了BC@Cu/Fe-5吸附Pb²⁺前后特征峰变化。BC@Cu/Fe-5吸附Pb²⁺的机理如下：大约42%的Pb²⁺被还原为Pb⁰,33%的Pb²⁺形成PbO/Pb(OH)₂,25%的Pb²⁺与O—H、C—O、C=O、COO、Fe—O等官能团形成配合物。Cu掺杂可以提高Fe还原Pb²⁺的能力。     

A squaraine-based chemosensor for Hg and Pb

A novel unsymmetrical cationic squaraine dye (USqH⁺), absorbing in the near-infrared region (600-850 nm), was synthesized by reacting a semi-squaric acid derivative 3-[4-(N,N-dioctylamino)phenyl]-4-hydroxycyclobutene-1,2-dione with the squarylium dye, bis(3-methylbenzothiazol-2-ylidene)squaraine. Addition of micromolar amounts of Hg²⁺ and Pb²⁺ to solutions of USqH⁺ in dichloromethane brings about significant changes in its absorption spectrum, resulting in a change in colour of the solution from green to pink. The absorption spectrum of the dye is relatively insensitive to other environmentally relevant metal ions, making it possible to visually detect Hg²⁺ and Pb²⁺ in the presence of other metal ions. Molecular modeling of the complexes at the density functional theory (DFT) and semiempirical PM3 levels strongly suggests that the oxygen atoms are the most likely choice for cation binding. The calculations also indicate a high affinity of Hg²⁺ and Pb²⁺ toward the formation of 2:1 complexes, which is in good agreement with the experimental results.     

A novel method for the simple and simultaneous preconcentration of Pb2+, Cu2+ and Zn2+ ions with aid of diethylenetriamine functionalized SBA-15 nanoporous silica compound

A rapid method for the extraction and monitoring of nanogram level of Pb²⁺, Cu²⁺ and Zn²⁺ ions using uniform silanized mesopor (SBA-15) functionalized with diethylenetriamine groups and flame atomic absorption spectrometry (FAAS) is presented. The preconcentration factor of the method is 100 and detection limit of the technique is 5.5?ng?mL^?1 and 1.4?ng?mL^?1 and 0.1?ng?mL^?1 for Pb²⁺, Cu²⁺ and Zn²⁺ respectively. The time and the optimum amount of the sorbent, pH and minimum amount of acid for stripping of ions from functionalized SBA-15 were tested. The maximum capacity the functionalized SBA-15 was found to be 183.0 (±1.9) µg, 156.0 (±1.5) µg and 80.0 (±1.6) µg of Pb²⁺, Cu²⁺ and Zn²⁺/mg functionalized SBA-15, respectively.     

Ratiometric and turn-on monitoring for heavy and transition metal ions in aqueous solution with a fluorescent peptide sensor

A novel fluorescent peptide sensor containing tryptophan (donor) and dansyl fluorophore (acceptor) was synthesized for monitoring heavy and transition metal (HTM) ions on the basis of metal ion binding motif (Cys-X-X-X-Cys). The peptide probe successfully exhibited a turn on and ratiometric response for several heavy metal ions such as Hg²⁺, Cd²⁺, Pb²⁺, Zn²⁺, and Ag⁺ in aqueous solution. The enhancements of emission intensity were achieved in the presence of the HTM ions by fluorescent resonance energy transfer (FRET) and chelation enhanced fluorescence (CHEF) effects. The detection limits of the sensor for Cd²⁺, Pb²⁺, Zn²⁺, and Ag⁺ were lower than the EPA's drinking water maximum contaminant levels (MCL). We described the fluorescent enhancement, binding affinity, and detection limit of the peptide probe for HTM ions.     

A novel method for the determination of Pb2+ based on the quenching of the fluorescence of CdTe quantum dots

A novel method for the determination of Pb²⁺ has been developed based on quenching of the fluorescence of thiol-capped CdTe quantum dots (QDs) by Pb²⁺ in aqueous solutions. Under optimum conditions, the relative fluorescence intensity was linearly proportional to the concentration of Pb²⁺ between 2.0 × 10⁻⁶ and 1.0 × 10⁻⁴ mol L⁻¹ with a detection limit of 2.7 × 10⁻⁷ mol L⁻¹. The relative standard deviation (RSD) was 4.6% for a 4.0 × 10⁻⁵ mol L⁻¹ Pb²⁺ solution (N = 5). As an application, the proposed method was successfully applied to the analysis of Pb²⁺ in food samples, and the results were satisfactory, i.e. consistent with those of flame atomic absorption spectrometry (FAAS). Correspondence: Heyou Han, College of Science, Institute of Chemical Biology, State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, P.R. China     

A highly selective visual and fluorescent sensor for Pb2+ and Zn2+ and crystal structure of Cu2+ complex based-on a novel single-armed Salamo-type bisoxime

A novel single-armed Salamo-type bisoximes (H₄L) has been designed and synthesised. An obvious colour change from yellow (H₄L) to pale pink (HL-Pb²⁺) which can be visually observed by the naked eye in visible light. H₄L can act as a fluorescent sensor for ratiometric recognition of Zn²⁺ with high selectivity and sensitivity. Crystallographic data of the [Cu(HL)(μ-OAc)Cu] reveals that the two Cu²⁺ ions are both penta-coordinated with square pyramidal geometries, and forms a 2D supramolecular plane structure by hydrogen bonding interactions.     

Specificity in the Cu interactions with prion protein fragments and related His-rich peptides from mammals to fishes

The prion proteins may play a critical role in copper homeostasis and the antioxidant activity in the brain. This review presents the state of art in the studies on Cu²⁺ prion systems. The proteins discussed are from different species from mammals to fishes. All proteins are His-rich and the research discussed clearly indicates the basic role of imidazole side chains and the adjacent amide nitrogen atoms in metal ion binding. Prions represent the family of proteins with new mode of Cu²⁺ binding which includes the amide nitrogen coordination. The multi-imidazole coordination is also likely and it can play a critical role in the antioxidant activity of the copper–prion complexes. The combination of the imidazole and amide nitrogen atoms to Cu²⁺ ions could also be relevant in histidine-rich peptide antibiotics including demegen. The impact of peptide sequence and His positions on copper binding ability is also discussed.     

电解液对全铅单液流电池电极性能的影响

研究Pb(II)和H+离子浓度对全铅单液流电池正、负电极在复合石墨基体上电化学行为的影响.结果表明,PbO2正极和Pb负极的电极过程受电化学和扩散混合控制.Pb(II)氧化沉积成PbO2时出现成核环,铅负极成核过电位小,充放电电压差远小于PbO2正极,电池极化主要来自PbO2正极.增加H+浓度有利于降低PbO2正极和Pb负极的极化,但析氧、析氢副反应和腐蚀加重.增大Pb(II)浓度有利于抑制析氧,但PbO2正极充电电压升高,充放电电压差增大.Pb(II)浓度较低时,充放电过程中PbO2沉积层少许脱落,充电电压进一步降低且更趋平稳.为此,电解液中HBF4浓度以2 mol L-1为宜,Pb(II)浓度应在0.9 mol L-1以上.     

Poly(vinyl chloride)-membrane ion-selective bulk optode based on 1,10-dibenzyl-1,10-diaza-18-crown-6 and 1-(2-pyridylazo)-2-naphthol for Cu and Pb ions

An ion-selective bulk optode (ISBO) for sensing Cu²⁺ and Pb²⁺ ions based on plasticized poly(vinyl chloride) containing 1,10-dibenzyl-1,10-diaza-18-crown-6 (DBzDA18C6) as ionophore and 1-(2-pyridylazo)-2-naphthol (PAN) as chromoionophore was prepared. The effects of DBzDA18C6/PAN and NaTPB/PAN mole ratios on the response behavior of the ISBO were investigated. The ISBO membrane shows enhanced selectivities for Cu²⁺ (at 530 nm) and Pb²⁺ (at 467 nm) over alkali, alkaline earth and other transition metal ions. The optical selectivity coefficients were measured using the separate solution method (SSM) in the two corresponding wavelengths at pH=5. The detection limit for Cu²⁺ and Pb²⁺ are 3.2×10⁻⁷ and 1.0×10⁻⁸ M, respectively.     

Synthetic Ionophores. Part 17. Synthesis of Ether-Amine-Amide Based m-Cyclophanes: A Search for Pb2+ Selective Ionophores

m-Cyclophanes 3, 4, and 5 possessing two ether oxygen, two amide, one NH and a -system, an optimal combination of ligating sites for selective Pb²⁺ binding, have been synthesized by condensations of diethylenetriamine, 3,3-diaminodipropylamine and 1,3-diaminopropane with 1,3-bis(ethoxycarbonylmethoxy) benzene (6) formed by the PTC reaction of resorcinol and ethyl chloroacetate. Ionophores 3-5 induced cation extraction/transport could not be studied due to their insolubility in CHCl₃/CH₂Cl₂ and solubility in water, but ¹³CNMR titrations of 4 with metal ions point to its binding preferences for Ag⁺ and Pb²⁺ over alkali/alkaline earth cations.     

Flow injection potentiometry by a new coated graphite ion-selective electrode for the determination of Pb(2+)

A new graphite coated electrode for the determination of Pb²⁺ based on a recently synthesized ionophore 1-hydroxy-2-{2-[2-(2-hydroxy-ethoxy)-ethoxy]-ethoxy methyl}-anthracene-9,10-dione (L) has been developed. The electrode was used in flow injection potentiometry by a home-made flow cell. Under both the batch and flow conditions, the electrode revealed a near Nernstian response over a wide lead ion concentration range (10⁻⁶ to 10⁻¹ M) and very low limit of detection. In flow injection potentiometry, excellent reproducibility (RSD%=0.49%), very high sampling rate (170 injections h⁻¹) and stable baseline was observed in the presence of 10⁻³ M KCl as ionic strength adjuster. The electrode showed high sensitivity and good selectivity for Pb²⁺ over a wide variety of alkali, alkali earth and transition metal ions and the electrode can be used for at least 3 months without any considerable change in potential response. The proposed sensor was successfully applied to the direct determination of lead in real samples and also used for the titrimetric determination of phosphate ions by both batch and flow injection potentiometry.     

Magnetic Nitrogen-Doped Porous Carbon Nanocomposite for Pb(II) Adsorption from Aqueous Solution

We report in the present study the in situ formation of magnetic nanoparticles (Fe₃O₄ or Fe) within porous N-doped carbon (Fe₃O₄/N@C) via simple impregnation, polymerization, and calcination sequentially. The synthesized nanocomposite structural properties were investigated using different techniques showing its good construction. The formed nanocomposite showed a saturation magnetization (M_s) of 23.0 emu g⁻¹ due to the implanted magnetic nanoparticles and high surface area from the porous N-doped carbon. The nanocomposite was formed as graphite-type layers. The well-synthesized nanocomposite showed a high adsorption affinity toward Pb²⁺ toxic ions. The nanosorbent showed a maximum adsorption capacity of 250.0 mg/g toward the Pb²⁺ metallic ions at pH of 5.5, initial Pb²⁺ concentration of 180.0 mg/L, and room temperature. Due to its superparamagnetic characteristics, an external magnet was used for the fast separation of the nanocomposite. This enabled the study of the nanocomposite reusability toward Pb²⁺ ions, showing good chemical stability even after six cycles. Subsequently, Fe₃O₄/N@C nanocomposite was shown to have excellent efficiency for the removal of toxic Pb²⁺ ions from water.     

Rhodamine-based chemosensing monolayers on glass as a facile fluorescent “turn-on” sensing film for selective detection of Pb

Rhodamine-based chemosensors 1 and 2 were synthesized and self-assembled onto glass surfaces for the selective fluorescent sensing of Pb²⁺. The immobilized chemosensors showed fluorescent responses that were turned-on with Pb²⁺ in CH₃CN, selectively over various metal ions. The Pb²⁺-selective fluorescent switch of the immobilized chemosensors was also reversible, allowing for repeated use for Pb²⁺ detection.     

A fluorescence reagent for the highly selective recognition and separation of lead ion (II) from aqueous solutions

A new fluorescence reagent, N,N-bi[4(1-pyrene)-butyroyl]-lysine (1) was synthesized. The new fluorescence sensor showed high sensitivity (detection limit up to 20.7 μg L⁻¹) and specific selectivity for Pb²⁺ over other metal ions examined in aqueous solutions. It could also be used to remove Pb²⁺ from aqueous solutions by filtering the insoluble 1–Pb²⁺ complex with sufficient reversibility.     

MnO2 nanozyme induced the chromogenic reactions of ABTS and TMB to visual detection of Fe2+ and Pb2+ ions in water

In this study, we used a simple and rapid colourimetric reaction for visual sensing of Fe²⁺ and Pb²⁺ ions in water by employing nano-MnO₂ as a natural oxidase mimic to respectively catalyse ABTS and TMB in citrate-phosphate buffer solution (C-PBS) at 25°C and pH 3.8. It was found that nano-MnO₂ possessed highly oxidase-mimicking activity with the K_m values of 0.030 and 0.027 toward ABTS and TMB, respectively, indicating TMB had a stronger affinity on nano-MnO₂ than ABTS. Interestingly, the presence of 0.01 mmol·L^?1 Fe²⁺/Pb²⁺ ion was able to significantly down-regulate the activity of MnO₂ nanozyme in nano-MnO₂-mediated ABTS reaction processes (P < 0.01), which mainly due to the strong adsorption of metal ion toward nano-MnO₂ surface via the electrostatic attractions, thus leading to the passivation and inactivation of MnO₂ nanozyme catalytic activity. Thereinto, Fe²⁺ reacted with multivalent manganese by oxidation-reduction, while Pb²⁺ was specifically adsorbed onto the surface of MnO₂ nanozyme and formed complexes. Notably, only Fe²⁺ ion inhibited the activity of MnO₂ nanozyme-TMB with a detection limit as low as 1.0 μmol·L^?1. In MnO₂ nanozyme-ABTS sensing systems, Fe²⁺ and Pb²⁺ ions detection limit of 0.5 and 2.0 μmol·L^?1 were, respectively, achieved with a linear response range of 0–0.02 and 0–0.8 mmol·L^?1, implying the developed MnO₂ nanozyme-ABTS sensor was potentially applicable for the visual determination of Fe²⁺ and Pb²⁺ ions in water. In the real water samples, MnO₂ nanozyme-ABTS achieved high accuracy (relative errors: 3.4?10.5%) and recovery (96?110%) for respective detection of Fe²⁺ and Pb²⁺ ions. The simple and rapid MnO₂ nanozyme-ABTS sensing systems might provide a practical assay for visual detection of Fe²⁺ and Pb²⁺ ions in the environmental water samples.     

Interdependence of Anion and Cation Exchanges in Calcium Hydroxyapatite: Pb and Cl

The ion exchange of Pb²⁺ and Cl⁻ into calcium hydroxyapatite from aqueous solutions is studied at 293 K. Although the exchange of Cl⁻ into CaHAp and PbHAp was not observed, in the presence of both Pb²⁺ and Cl⁻ in aqueous solution the exchange of both Pb²⁺ and Cl⁻ into CaHAp occurred, and, at least at intermediate concentrations of HCl, a proportionality between the sorbed quantities of these two ions was observed. The dissolution of CaHAp is shown to be dependent upon the pH, while the quantity of Pb²⁺ exchanged into the solid is not a function of the proton content; consequently, the exchange is not primarily a dissolution–precipitation process.