Sensitive Detection of Elemental Mercury Vapor by Gold Nanoparticle Decorated Carbon Nanotube Sensors

Low-cost, low power consumption gas sensors that can detect or quantify various gas analytes are of increasing interest for various applications ranging from mobile health, to environmental exposure assessment and homeland security. In particular miniature gas sensors based on nanomaterials that can be manufactured in the form of sensor arrays present great potential for the development of portable monitoring devices. In this study, we demonstrate that a chemiresistive nanosensor comprised of single walled carbon nanotubes decorated with gold nanoparticles has impressive sensitivity to elemental mercury (Hg) gas concentrations, with a lower detection limit as low as 2 ppb(v). Furthermore, this nanosensor was found to regenerate, though slowly, without any additional recovery steps. Finally, the mercury vapor sensing mechanism allowed for direct investigations into the origin of Surface Enhanced Raman Scattering (SERS) in carbon nanotubes decorated with Au nanoparticles.     

A highly selective colorimetric aqueous sensor for mercury

A new colorimetric mercury sensor is reported based on binding to terpyridine derivatives. It is able to selectively detect Hg II ions over a number of environmentally relevant ions including Ca II, Pb II, Zn II, Cd II, Ni II, Cu II, and others. The response time upon exposure to Hg II is instantaneous. By the "naked eye," the detection limit of Hg II is 2 ppm (25 microM) in solution. With a spectrometer, this detection limit is increased down to 2 ppb (25 nM), which is the current EPA standard for drinking water. The significant problem of mercury poisoning requires new methods of detection that are sensitive and selective. Here we report a new simple system that takes advantage of the unique optical properties generated by terpyiridine-Hg complexes.     

Nanocatalyst/Nanoplasmon‐Enabled Detection of Organic Mercury: A One‐Minute Visual Test

We present a fast and sensitive nanosensor that can detect organic mercury, exploiting the combination of the catalytic and plasmonic properties of gold nanoparticles (AuNPs). The method is one‐step and completely instrument‐free, and has a colorimetric readout clearly detectable by simple visual inspection. The AuNPs catalyze efficient organic mercury reduction to the metallic form (Hg⁰), allowing its nucleation and amalgam formation on particle surface, with consequent aggregation‐induced plasmon shift. This leads to very rapid (1 min) and specific colorimetric detection of mercury species. The achieved limit of detection (20 ppb) is compliant with current regulatory limits in food.     

Carbon Paste Electrode Modified with Carbamoylphosphonic Acid Functionalized Mesoporous Silica: A New Mercury‐Free Sensor for Uranium Detection

This study reports a new approach for developing a uranium electrochemical sensor that is mercury‐free, solid‐state, and has less chance for ligand depletion than existing sensors. A carbon‐paste electrode modified with carbamoylphosphonic acid self‐assembled monolayer on mesoporous silica was developed for uranium detection based on an adsorptive square‐wave stripping votammetry technique. Voltammetric responses for uranium detection are reported as a function of pH, preconcentration time, and aqueous phase uranium concentration. The uranium detection limit is 25 ppb after 5 minutes preconcentration and improved to 1 ppb after 20 minutes preconcentration. The relative standard deviations are normally less than 5%.     

H2S gas sensor based on integrated resonant dual-microcantilevers with high sensitivity and identification capability

Detection of trace-level hydrogen sulfide (H₂S) gas is of great importance whether in industrial production or disease diagnosis. This research presents a novel H₂S gas sensor based on integrated resonant dual-microcantilevers which can identify and detect trace-level H₂S in real-time. The sensor consists of two integrated resonant microcantilever sensors with different functions. One cantilever sensor can identify H₂S by outputting positive frequency shift signals, while the other cantilever sensor will detect H₂S as a normally used cantilever sensor with negative frequency shifts. Combined the two cantilever sensors, the proposed gas sensor can distinguish H₂S from a variety of common gases, and the detection limit to H₂S of the sensor is as sensitive as below 1 ppb.     

Calibrated nanoinjections of mercury vapor

A simple technique for the calibration of mercury vapor chemosensors is described. It is based on a reductive deposition of a well-defined quantity of mercury (0) onto gold wire followed by thermal evaporation of the mercury into the sensor cell. The quantity of mercury on the gold wire was measured electrochemically by oxidation before and after heating, as well as after storage under different conditions. It is shown that the technique can be used for calibrated injections of nanogram quantities of mercury. The approach was applied to test the performance of ultrasensitive mercury chemoresistors.     

Calibrated nanoinjections of mercury vapor

A simple technique for the calibration of mercury vapor chemosensors is described. It is based on a reductive deposition of a well-defined quantity of mercury (0) onto gold wire followed by thermal evaporation of the mercury into the sensor cell. The quantity of mercury on the gold wire was measured electrochemically by oxidation before and after heating, as well as after storage under different conditions. It is shown that the technique can be used for calibrated injections of nanogram quantities of mercury. The approach was applied to test the performance of ultrasensitive mercury chemoresistors.     

Direct colorimetric visualization of mercury (Hg) based on the formation of gold nanoparticles

It is critical to be able to detect and quantify Hg²⁺ ions under aqueous conditions with high sensitivity and selectivity. The technique presented herein provides a direct way for simple colorimetric visualization of Hg²⁺ ions in aqueous solution, based on the formation of gold nanoparticles through the Hg²⁺ catalyzed HAuCl₄/NH₂OH reaction. The outstanding selectivity and sensitivity result from the well-known amalgamation process that occurs between mercury and gold. The entire procedure takes less than 20 min. The limit of detection (2 ppb) shows excellent potential for monitoring ultralow levels of mercury in water samples.     

气相富集-溶出伏安法测定汞的研究

元素汞在常温下有很高的挥发性,并与金有很强的结合能力,本文利用汞的这些特性,建立了一个测汞的新方法,即气相富集-阳极溶出伏安法。本方法有很高的选择性和较高的灵敏度。用883型极谱仪,汞浓度的定量测定范围为0.2-8.0ppb,定性检出下限为0.05ppb,将此法用于实际水样的测定,得到了满意的结果。     

Gold Nanoparticle Modified Screen Printed Electrodes for the Trace Sensing of Arsenic(III) in the Presence of Copper(II)

Gold ensembles for the trace level sensing of arsenic(III) in the presence of copper(II) are reported. The gold ensembles are fabricated using citrate capped gold nanoparticles which are chemically synthesised in an aqueous solution with an aliquot of this simply cast onto an economical and disposable screen printed electrode. After drying at room temperature, the gold ensembles are ready for use. The gold ensembles are explored towards the sensing of arsenic(III) in the presence of copper(II) using anodic stripping voltammetry where the corresponding stripping peaks are well resolved and using this protocol it is possible to readily detect 3 µg L^?1 (3 ppb) with a detection limit of 0.4 µg L^?1 (0.4 ppb). Proof‐of‐concept is also shown for the sensing of arsenic(III) in a canal water sample. Given the low cost of the sensor and ease of fabrication, the gold ensembles hold promise for the sensing of arsenic(III) in water samples where copper(II) may be present.     

A surface plasmon resonance immunosensor for detecting a dioxin precursor using a gold binding polypeptide

A surface plasmon resonance (SPR) based biosensor was developed for monitoring 2,4-dichlorophenol, a known dioxin precursor, using an indirect competitive immunoassay. The SPR sensor was fabricated by immobilizing a gold-thin layer on the surface of an SPR sensor chip with an anti-(2,4-dichlorophenol) antibody using a gold binding polypeptide (GBP) and protein G. The SPR response based on the antigen-antibody reaction in a flow system was measured by injecting a 2,4-dichlorophenol sample solution into the flow system in which the SPR sensor was located. In a direct immunoassay system using the modified sensor chip, no significant SPR angle shift less than 0.001° was observed when a 25 ppm of 2,4-dichlorophenol solution was injected. In order to improve the sensitivity of the SPR sensor, an indirect competitive immunoassay method was used in conjunction with the SPR sensor system using 2,4-dichlorophenol conjugated with bovine serum albumin (BSA). In the competitive assay, a 350 ppm 2,4-dichlorophenol-BSA conjugate solution containing 2,4-dichlorophenol at various concentrations (10-250 ppb) were injected into the SPR sensor system. The sensitivity of this indirect immunoassay was found to be extremely sensitive, compared to the direct one, and a detection limit of 20 ppb was estimated. Verification that the use of GBP for immobilizing the antibody on the sensor chip enhanced the sensitivity to 2,4-dichlorophenol was obtained by comparing the procedure with another modification, in which BSA was used instead of GBP for immobilizing the antibody on the sensor chip. The affinity constant of 2,4-dichlorophenol and its conjugate to the antibody were estimated form the SPR response.     

A fluorescence turn-on sensor for iodide based on a thymine-Hg(II)-thymine complex

Iodide plays a vital role in many biological processes, including neurological activity and thyroid function. Due to its physiological relevance, a method for the rapid, sensitive, and selective detection of iodide in food, pharmaceutical products, and biological samples such as urine is of great importance. Herein, we demonstrate a novel and facile strategy for constructing a fluorescence turn-on sensor for iodide based on a T-Hg(II)-T complex (T=thymine). A fluorescent anthracene-thymine dyad (An-T) was synthesized, the binding of which to a mercury(II) ion lead to the formation of a An-T-Hg(II)-T-An complex, thereby quenching the fluorescent emission of this dyad. In this respect, the dyad An-T constituted a fluorescence turn-off sensor for mercury(II) ions in aqueous media. More importantly, it was found that upon addition of iodide, the mercury(II) ion was extracted from the complex due to the even stronger binding between mercury(II) ions and iodide, leading to the release of the free dyad and restoration of the fluorescence. By virtue of this fluorescence quenching and recovery process, the An-T-Hg(II)-T-An complex constitutes a fluorescence turn-on sensor for iodide with a detection limit of 126 nM. Moreover, this sensor is highly selective for iodide over other common anions, and can be used in the determination of iodide in drinking water and biological samples such as urine. This strategy may provide a new approach for sensing some other anions.     

基于免疫胶体金试纸条检测盐酸克伦特罗的便携式光电型传感器

利用免疫竞争抗制原理制备检测盐酸克伦特罗的免疫纳米金试纸条,盐酸克伦特罗与CLB-BSA复合物竞争性结合胶体金上抗体的有限位点,从而使试纸条上的检测带显色减弱或消失.将显色后的试纸条插入自行研制的光电型传感器的测试孔内,根据反射光的强弱计算出克伦特罗的浓度.结果表明:用光电传感方法检测盐酸克伦特罗的线性范围为1～10 μg/L,检出限为0.05 μg/L,回收率为85.5％～96.0％.此光电型传感器检测克伦特罗具有简便、快速、灵敏、特异性强的优点.     

A PEGylated Fluorescent Turn‐On Sensor for Detecting Fluoride Ions in Totally Aqueous Media and Its Imaging in Live Cells

Owing to the considerable significance of fluoride anions for health and environmental issues, it is of great importance to develop methods that can rapidly, sensitively and selectively detect the fluoride anion in aqueous media and biological samples. Herein, we demonstrate a robust fluorescent turn‐on sensor for detecting the fluoride ion in a totally aqueous solution. In this study, a biocompatible hydrophilic polymer poly(ethylene glycol) (PEG) is incorporated into the sensing system to ensure water solubility and to enhance biocompatibility. tert‐Butyldiphenylsilyl (TBDPS) groups were then covalently introduced onto the fluorescein moiety, which effectively quenched the fluorescence of the sensor. Upon addition of fluoride ion, the selective fluoride‐mediated cleavage of the Si? O bond leads to the recovery of the fluorescein moiety, resulting in a dramatic increase in fluorescence intensity under visible light excitation. The sensor is responsive and highly selective for the fluoride anion over other common anions; it also exhibits a very low detection limit of 19 ppb. In addition, this sensor is operative in some real samples such as running water, urine, and serum and can accurately detect fluoride ions in these samples. The cytotoxicity of the sensor was determined to be Grade I toxicity according to United States Pharmacopoeia and ISO 10993‐5, suggesting the very low cytotoxicity of the sensor. Moreover, it was found that the senor could be readily internalized by both HeLa and L929 cells and the sensor could be utilized to track fluoride level changes inside the cells.     

Reversible colorimetric probes for mercury sensing

The selectivity and sensitivity of two colorimetric sensors based on the ruthenium complexes N719 [bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) bis(tetrabutylammonium) bis(thiocyanate)] and N749 [(2,2':6',2' '-terpyridine-4,4',4' '-tricarboxylate)ruthenium(II) tris(tetrabutylammonium) tris(isothiocyanate)] are described. It was found that mercury ions coordinate reversibly to the sulfur atom of the dyes' NCS groups. This interaction induces a color change in the dyes at submicromolar concentrations of mercury. Furthermore, the color change of these dyes is selective for mercury(II) when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II). The detection limit for mercury(II) ions--using UV-vis spectroscopy--in homogeneous aqueous solutions is estimated to be approximately 20 ppb for N719 and approximately 150 ppb for N749. Moreover, the sensor molecules can be adsorbed onto high-surface-area mesoporous metal oxide films, allowing reversible heterogeneous sensing of mercury ions in aqueous solution. The results shown herein have important implications in the development of new reversible colorimetric sensors for the fast, easy, and selective detection and monitoring of mercuric ions in aqueous solutions.     

Development and applications of fluorogenic probes for mercury(II) based on vinyl ether oxymercuration

Mercury is a major threat to the environment and to human health. It is highly desirable to develop a user-friendly kit for on-site mercury detection. Such a method must be able to detect mercury below the threshold levels for drinking water, 1-2 ppb. We developed a fluorescence method based on the oxymercuration of vinyl ethers to detect mercury in dental and environmental samples. Chloride ions interfered with the oxymercuration reaction, but the addition of AgNO(3) solved this problem. Fine electronic and structural tuning led to the development of a more responsive probe that was less sensitive to chloride ion interference. This second-generation probe could detect 1 ppb mercury ions in water.     

Sequence-specific detection of femtomolar DNA via a chronocoulometric DNA sensor (CDS): effects of nanoparticle-mediated amplification and nanoscale control of DNA assembly at electrodes

We herein report a novel nanoparticle-based electrochemical DNA detection approach. This DNA sensor is based on a "sandwich" detection strategy, which involves capture probe DNA immobilized on gold electrodes and reporter probe DNA labeled with gold nanoparticles that flank the target DNA sequence. Electrochemical signals are generated by chronocoulometric interrogation of [Ru(NH(3))(6)](3+) that quantitatively binds to surface-confined capture probe DNA via electrostatic interactions. We demonstrated that the incorporation of a gold nanoparticle in this sensor design significantly enhanced the sensitivity and the selectivity. Nanoscale control of the self-assembly process of DNA probes at gold electrodes further increased the sensor performance. As a result of these two combined effects, this DNA sensor could detect as low as femtomolar (zeptomoles) DNA targets and exhibited excellent selectivity against even a single-base mismatch. In addition, this novel DNA sensor showed fairly good reproducibility, stability, and reusability.     

A plasmonic mercury sensor based on silver–gold alloy nanoparticles electrodeposited on indium tin oxide glass

We construct silver–gold alloy nanoparticles (Ag–AuNPs) as the basis of a reagentless, sensitive and simple mercury sensor. Ag–AuNPs were electrodeposited directly on transparent indium tin oxide film coated glass. Hg(II) ions in aqueous solution could be reduced by Ag atoms existing in Ag–AuNPs; the deposition/amalgamation of Hg on the nanoparticles resulted in a blue shift of the localized surface plasmon resonance peak. Therefore, Hg^2 + can be detected quantitatively by using a spectrophotometer. The sensor response is linear in the range from 0.05 to 500 ppb of Hg(II) concentration. No sample separation or preconcentration is required for detection of ultralow levels of mercury in water samples. The results shown herein have potential applications in the development of a new optical sensor for the detection of low concentrations of mercury.     

微电极研究Ⅵ.碳纤维微电极阳极溶出伏安研究

用电化学方法和扫描电镜对沉积晶体图象的观察,剖析了碳纤维微电极上汞膜的形成过程,提出了优化汞膜的实验条件;导出了碳纤维微汞膜电极上单扫描溶出电流方程式。通过搅拌和支持电解质对溶出峰电流影响的研究,提出了一个简化的分析手续,开发了CFME在ASV中的应用,Cu~(2+),Pb~(2+),In~(3+)和Cd~(2+)同时测定的检测限达3.0,0.6,1.2和0.5ppb,Zn~(2+)的检出限为1.3ppb。     

Determination of cis-diamminedichloroplatinum(II) in human plasma using ion-pair chromatography with electrochemical detection

A thin-layer gold/mercury electrode and a hanging mercury drop electrode are compared as part of an evaluation of liquid chromatography (LC) with electrochemical detection (ED) for the determination of platinum species in human plasma ultrafiltrate. The platinum species, derived from an aged aqueous solution of the antineoplastic agent cis-diamminedichloroplatinum(II) (CDDP), can be separated by ion-pair chromatography. Variation of a number of parameters is described along with the limitations and advantages of each kind of electrode system. We have used our LC-ED technique to separate CDDP from its hydrolysis products and other non-platinum-containing species in human plasma ultrafiltrate with a detection limit of 62 ng/ml (ppb).