Co-reporter:Jiawang Ding, Enguang Lv, Liyan Zhu, and Wei Qin
Analytical Chemistry March 21, 2017 Volume 89(Issue 6) pp:3235-3235
Publication Date(Web):March 6, 2017
DOI:10.1021/acs.analchem.7b00072
We report here on an optical ion sensing platform, in which a polymeric membrane ion-selective electrode (ISE) serves as not only a potentiometric transducer for ion activities in the sample solution but also a reference electrode for the potential-modulated release of enzyme from an iron-alginate-horseradish peroxidase (HRP) thin film modified working electrode. The ISE and working electrode are physically separated by a salt bridge. The dissolution of the HRP-embedded thin film can be triggered by the reduction of Fe3+, which is modulated by the potential response of the ISE to the target ion in the sample. The released enzyme induces the oxidation of its substrate mediated by H2O2 to produce a visual color change. With this setup, an optical ion sensing platform for both cations (e.g., NH4+) and anions (e.g., Cl–) can be obtained. The proposed platform provides a general and versatile visual-sensing strategy for ions and allows optical ion sensing in colored and turbid solutions.
Co-reporter:Xianzhong Zeng, Wei Qin
Analytica Chimica Acta 2017 Volume 982(Volume 982) pp:
Publication Date(Web):22 August 2017
DOI:10.1016/j.aca.2017.05.032
•A solid-contact ion selective electrode with MoO2 microspheres as ion-to-electron transducer was fabricated.•MoO2 microspheres work as metallic analogues based on non-carbon and non-noble metal materials.•MoO2 microspheres were synthesized from MoO3 with a certain morphology via a simple method.A solid-contact ion-selective electrode (SC-ISE) for potassium with MoO2 microspheres as ion-to-electron transducer is described. MoO2 microsphers can be synthesized via the reduction of MoO3 nanobelts in an isopropanol solvent with a mild process, and the obtained MoO2 microspheres have been characterized by X-ray diffraction and field-emission scanning electron microscopy. With the application of MoO2 microspheres, the newly fabricated SC-ISE for K+ exhibits a stable and rapid potential response. A near Nernstian slope of 55 mV/decade to potassium activities in the range of 10−5 ‒ 10−3 M is found and the detection limit is 10−5.5 M. Impedance spectra and chronopotentiometry results show that a smaller resistance together with a larger double layer capacitance is guaranteed due to the introduction of the intermediate layer of MoO2 microspheres. Additionally, light, O2 and CO2 do not induce significant influences to the present SC-ISE, and a reduced water layer between the ion selective membrane and the underlying conductor is formed. Thus, it is clear that MoO2 microspheres, as metallic analogues, can be used as a good candidate for the new type of transducing layer in SC-ISEs.Download high-res image (158KB)Download full-size image
Co-reporter:Dr. Rongning Liang;Dr. Jiawang Ding;Shengshuai Gao; Dr. Wei Qin
Angewandte Chemie 2017 Volume 129(Issue 24) pp:6937-6941
Publication Date(Web):2017/06/06
DOI:10.1002/ange.201701892
AbstractUsing sensors to quantify clinically relevant biological species has emerged as a fascinating research field due to their potential to revolutionize clinical diagnosis and therapeutic monitoring. Taking advantage of the wide utility in clinical analysis and low cost of potentiometric ion sensors, we demonstrate a method to use such ion sensors to quantify bioanalytes without chemical labels. This is achieved by combination of chronopotentiometry with a mussel-inspired surface imprinting technique. The biomimetic sensing method is based on a blocking mechanism by which the recognition reaction between the surface imprinted polymer and a bioanalyte can block the current-induced ion transfer of an indicator ion, thus causing a potential change. The present method offers high sensitivity and excellent selectivity for detection of biological analytes. As models, trypsin and yeast cells can be measured at levels down to 0.03 U mL−1 and 50 CFU mL−1, respectively.
Co-reporter:Dr. Rongning Liang;Dr. Jiawang Ding;Shengshuai Gao; Dr. Wei Qin
Angewandte Chemie International Edition 2017 Volume 56(Issue 24) pp:6833-6837
Publication Date(Web):2017/06/06
DOI:10.1002/anie.201701892
AbstractUsing sensors to quantify clinically relevant biological species has emerged as a fascinating research field due to their potential to revolutionize clinical diagnosis and therapeutic monitoring. Taking advantage of the wide utility in clinical analysis and low cost of potentiometric ion sensors, we demonstrate a method to use such ion sensors to quantify bioanalytes without chemical labels. This is achieved by combination of chronopotentiometry with a mussel-inspired surface imprinting technique. The biomimetic sensing method is based on a blocking mechanism by which the recognition reaction between the surface imprinted polymer and a bioanalyte can block the current-induced ion transfer of an indicator ion, thus causing a potential change. The present method offers high sensitivity and excellent selectivity for detection of biological analytes. As models, trypsin and yeast cells can be measured at levels down to 0.03 U mL−1 and 50 CFU mL−1, respectively.
Co-reporter:Tanji Yin, Xiaojing Jiang, Wei Qin
Analytica Chimica Acta 2017 Volume 989(Volume 989) pp:
Publication Date(Web):9 October 2017
DOI:10.1016/j.aca.2017.08.015
•A magnetic field-directed self-assembly strategy is proposed to prepare the solid contact.•The solid contact is fabricated by physically adsorbing magnetic graphene powder on a magnetic gold electrode.•The proposed method is simple, fast and general as compared to the multilayer drop-casting and electrodeposition methods.A magnetic field-directed self-assembly solid contact has been proposed for developing an all-solid-state polymeric membrane Ca2+-selective electrode. The solid contact is prepared by physically adsorbing magnetic graphene powder on a magnetic gold electrode under the direction of the magnetic field. The proposed method for preparing solid contact avoids using the aqueous solutions and is simple, fast and general as compared to the multilayer drop-casting and electrodeposition methods. The all-solid-state Ca2+-selective electrode based on magnetic graphene as solid contact shows a stable potential response in the linear range of 1.0 × 10−6-1.0 × 10−3 M with a slope of 28.2 mV/decade, and the detection limit is about 4.0 × 10−7 M. Additionally, the magnetic graphene-based electrode shows a comparable potential stability performance to other graphene-based all-solid-state ion-selective electrodes, such as reduced undesirable water layer and insensitive to the interferences of O2, CO2 and light. This work provides a favorable way to prepare solid contact for use in the field of all-solid-state ion-selective electrodes.Download high-res image (144KB)Download full-size image
Co-reporter:Jinghui Li, Tanji Yin, Wei Qin
Sensors and Actuators B: Chemical 2017 Volume 239() pp:438-446
Publication Date(Web):February 2017
DOI:10.1016/j.snb.2016.08.008
•An all-solid-state Cd2+-ISE based on 3D PGR-MPN composite is described.•The 3D PGR with MPNs as cross-linking sites is synthesized by a one-step method.•The electrode shows an excellent potential stability with a LOD of 10−8.8 M.The three-dimensional porous graphene-mesoporous platinum nanoparticle (3D PGR-MPN) composite is used as solid contact for developing an all-solid-state polymeric membrane Cd2+ ion-selective electrode (Cd2+-ISE). The 3D PGR with MPNs as cross-linking sites can be synthesized by a facile hydrothermal co-assembly method. The obtained 3D PGR-MPN composite is promising for acting as solid contact due to its unique characteristics such as high interfacial area, superior double layer capacitance, excellent conductivity and high hydrophobicity. The ISE exhibits a stable Nernstian response in the range of 10−8–10−4 M and the detection limit is 10−8.8 M. The 3D PGR-MPN-based Cd2+-ISE shows good potential response and no water layer exists between the polymeric membrane and the 3D PGR-MPN layer. Additionally, the proposed Cd2+-ISE is robust to O2, CO2 and light interferences. This work provides a versatile method for preparing an effective solid contact to develop a stable and reliable all-solid-state ISE.
Co-reporter:Xianzhong Zeng, Wei Qin
Materials Letters 2016 Volume 182() pp:347-350
Publication Date(Web):1 November 2016
DOI:10.1016/j.matlet.2016.07.026
•MoS2 nanoparticles were synthesized from MoO3 nanobelts via a surfacant-assisted hydrothermal method.•MoO3 with a certain morphology was used as the precursor and PVP was applied as the surfacant.•The presence of PVP was proved to be crucial for the synthesis of MoS2 nanoparticles and the possible mechanism was discussed.The synthesis of MoS2 nanoparticles from MoO3 with a certain morphology through a surfactant-assisted hydrothermal process is described in this paper. MoO3, which has a nanobelt morphology with a width of 100–500 nm and a length from one to several micrometers, is used as the precursor, and poly(vinylpyrrolidone) (PVP) is used as the surfactant. The morphology of the resulting MoS2 nanomaterial has been characterized by the field-emission scanning electron microscope, which shows that the obtained nanoparticles have diameters ranging from 50 to 100 nm with rough surfaces. Additionally, the composition and crystallinity as well as the phase information of the produced nanoparticles have been characterized by the energy-dispersive X-ray spectrometer and X-ray diffraction. Specifically, in this process, the presence of PVP plays a crucial role for the successful fabrication of the nanoparticle morphology, which may be due to the formation of PVP micelles leading to an oriented aggregation of MoS2 nuclei. In addition, comparative experiments have been conducted and the possible reaction mechanism is proposed.
Co-reporter:Xianzhong Zeng, Shunyang Yu, Qun Yuan, Wei Qin
Sensors and Actuators B: Chemical 2016 Volume 234() pp:80-83
Publication Date(Web):29 October 2016
DOI:10.1016/j.snb.2016.04.153
•Three-dimensional flowerlike MoS2 can be synthesized via a hydrothermal method.•3D flowerlike MoS2 has been used as solid contact for ion selective electrodes.•The solid contact is based on non-carbon and non-noble metal materials.Three-dimensional (3D) molybdenum sulfide (MoS2) nanoflowers have been synthesized via a novel hydrothermal method and applied as ion-to-electron transducer for solid-contact ion-selective electrodes (SC-ISEs). The morphology and elemental composition of the prepared nanomaterials have been characterized. The performance of the developed K+-SC-ISE has been demonstrated by determining K+ in solution with a polymeric membrane containing valinomycin as the ionophore. A Nernstian slope of 55.8 mV/decade with a detection limit of 10−5.5 M can be obtained. Using the 3D flowerlike MoS2 as solid contact, the fabricated K+-SC-ISE exhibits a smaller impedance and more stable potential response than the coated-wire electrode. In addition, the novel SC-ISE behaves well in the water layer test and shows good resistance to interferences from light, O2 and CO2. It is believed that the 3D MoS2 nanoflowers can be a good alternative as solid contact in SC-ISEs.
Co-reporter:Jiawang Ding, Yue Gu, Fei Li, Hongxia Zhang, and Wei Qin
Analytical Chemistry 2015 Volume 87(Issue 13) pp:6465
Publication Date(Web):June 5, 2015
DOI:10.1021/acs.analchem.5b01576
In this work, a simple, general, and sensitive potentiometric platform is presented, which allows potentiometric sensing to be applied to any class of molecule irrespective of the analyte charge. DNA nanostructures are self-assembled on magnetic beads via the incorporation of an aptamer into a hybridization chain reaction. The aptamer–target binding event leads to the disassembly of the DNA nanostructures, which results in a dramatic change in the surface charge of the magnetic beads. Such a surface charge change can be sensitively detected by a polycation-sensitive membrane electrode using protamine as an indicator. With an endocrine disruptor bisphenol A as a model, the proposed potentiometric method shows a wide linear range from 0.1 to 100 nM with a low detection limit of 80 pM (3σ). The proposed sensing strategy will lay a foundation for the development of potentiometric sensors for highly sensitive and selective detection of various targets.
Co-reporter:Jinghui Li, Tanji Yin, Wei Qin
Analytica Chimica Acta 2015 Volume 876() pp:49-54
Publication Date(Web):30 May 2015
DOI:10.1016/j.aca.2015.03.038
•An all-solid-state Pb2+-ISE with bimodal pore C60 as solid contact is developed.•The bimodal pore C60-based solid contact is prepared by electrochemical deposition.•The electrode shows an excellent potential stability with a LOD of 5.0 × 10−10 M.An all-solid-state polymeric membrane Pb2+ ion-selective electrode (Pb2+-ISE) based on bimodal pore C60 (BP-C60) as solid contact has been developed. A BP-C60 film can be readily formed on the surface of a glassy carbon electrode by electrochemical deposition. Cyclic voltammetry and electrochemical impedance spectroscopy have been employed to characterize the BP-C60 film. The large double layer capacitance and fast charge-transfer capability make BP-C60 favorable to be used as solid contact for developing all-solid-state ISEs. The all-solid-state BP-C60-based Pb2+-ISE shows a Nernstian response in the range from 1.0 × 10−9 to 1.0 × 10−3 M with a detection limit of 5.0 × 10−10 M. The membrane electrode not only displays an excellent potential stability with the absence of a water layer between the ion-selective membrane and the underlying BP-C60 solid contact, but also is insensitive to interferences from O2, CO2 and light. The proposed solid-contact Pb2+-ISE has been applied to determine Pb2+ in real water samples and the results agree well with those obtained by anodic stripping voltammetry.
Co-reporter:Jiahong Lei, Jiawang Ding, Yan Chen, Wei Qin
Analytica Chimica Acta 2015 Volume 858() pp:60-65
Publication Date(Web):9 February 2015
DOI:10.1016/j.aca.2014.12.018
•A potentiometric flow injection system for determination of heparin is described.•An external current is applied for controlled release of protamine.•The system has been employed for detection of heparin in whole blood.A flow injection system incorporated with a polycation-sensitive polymeric membrane electrode in the flow cell is proposed for potentiometric determination of heparin. An external current in nano-ampere scale is continuously applied across the polymeric membrane for controlled release of protamine from the inner filling solution to the sample solution, which makes the electrode membrane regenerate quickly after each measurement. The protamine released at membrane–sample interface is consumed by heparin injected into the flow cell via their strong electrostatic interaction, thus decreasing the measured potential, by which heparin can be detected. Under optimized conditions, a linear relationship between the potential peak height and the concentration of heparin in the sample solution can be obtained in the range of 0.1–2.0 U mL−1, and the detection limit is 0.06 U mL−1. The proposed potentiometric sensing system has been successfully applied to the determination of heparin in undiluted sheep whole blood.
Co-reporter:Rongning Liang, Tanji Yin, Wei Qin
Analytica Chimica Acta 2015 Volume 853() pp:291-296
Publication Date(Web):1 January 2015
DOI:10.1016/j.aca.2014.10.033
•A general method for fabricating nanomaterials based solid-contact ISEs is developed.•The mixture of an ionic liquid and a nanomaterial is used as intermediate layer.•The detection limits of the proposed sensors are in the nanomolar range.•The developed electrodes exhibit a good response time and excellent stability.A simple and robust approach for the development of solid-state ion-selective electrodes (ISEs) using nanomaterials as solid contacts is described. The electrodes are fabricated by using the mixture of an ionic liquid (IL) and a nanomaterial as intermediate layer, formed by melting the IL. Tetradodecylammonium tetrakis(4-chlorophenyl)borate (ETH 500) is chosen as an model of IL to provide strong adhesion between the inner glassy carbon electrode and the intermediate layer. Nanomaterials including single-walled carbon nanotubes (SWCNTs) and graphene were used as active ion-to-electron transducers between the glassy carbon electrode and the ionophore-doped ISE membrane. By using the proposed approach, the solid-contact Cu2+- and Pb2+-selective electrodes based on ETH 500/SWCNTs and ETH 500/graphene as transducers, respectively, have been fabricated. The proposed electrodes show detection limits in the nanomolar range and exhibit a good response time and excellent stability.
Co-reporter:Long Li and Wei Qin
RSC Advances 2015 vol. 5(Issue 122) pp:100689-100692
Publication Date(Web):19 Nov 2015
DOI:10.1039/C5RA19654J
The unexpected potential responses to electrically neutral thiophenols (ArSHs) of anion-exchanger doped polymeric membranes are described. Based on the dimerization reactions of ArSHs via horseradish peroxidase (HRP)-catalyzed oxidations, a sensitive and facile potentiometric biosensing platform for HRP has been developed.
Co-reporter:Fangfang Geng, Jiawang Ding, Cuiying Jia, Baojun Ding and Wei Qin
RSC Advances 2015 vol. 5(Issue 43) pp:34475-34480
Publication Date(Web):09 Apr 2015
DOI:10.1039/C5RA00263J
A potentiometric sensing system for the sensitive and selective detection of methyl parathion (MP) is described in this paper. The system is based on a degrading bacterium Klebsiella sp. MP-6 as recognition element and a polymeric membrane anion-sensitive electrode as a transducer. Klebsiella sp. MP-6 can be isolated from long-term organophosphorus pesticide contaminated soils, which is capable of biodegrading MP to produce p-nitrophenol. The product can be deprotonated under basic conditions and thus detected by using the anion exchanger based membrane electrode. The bioreactor is prepared by packing the bacterial cells between two polyether sulfone membranes placed in a holder. Molecularly imprinted solid-phase extraction using the MP imprinted polymer as a sorbent enables accumulation and separation of MP from real samples. Under the optimized experimental conditions, the potential response of the biosensing system is linear with the MP concentration in the range of 5–100 nM. The detection limit is 1 nM. The electrode exhibits an excellent selectivity towards other organophosphorus pesticides. The sensing system has been evaluated with spiked water samples and shows good recovery and high accuracy. This methodology is promising to develop potentiometric sensors for detecting organophosphorus pesticides at trace levels in the environment.
Co-reporter:Wenchao Wei, Rongning Liang, Zhuo Wang and Wei Qin
RSC Advances 2015 vol. 5(Issue 4) pp:2659-2662
Publication Date(Web):01 Dec 2014
DOI:10.1039/C4RA12555J
A hydrophilic molecularly imprinted polymer (H-MIP) for selective recognition of polycyclic aromatic hydrocarbons in an aqueous medium has been developed in which a hydrophilic functional co-monomer is used to improve the surface hydrophilicity. By using phenanthrene as a model, the proposed H-MIP exhibits remarkably improved selectivity in aqueous solution.
Co-reporter:Jiahong Lei, Jiawang Ding and Wei Qin
Analytical Methods 2015 vol. 7(Issue 3) pp:825-829
Publication Date(Web):05 Jan 2015
DOI:10.1039/C4AY02662D
In this research, we demonstrate a simple flow injection analysis system for chronopotentiometric aptasensing of E. coli O157. The sensing protocol is based on using an aptamer as a bioreceptor and the current-driven-release of protamine from a polyion-sensitive membrane electrode as a signal reporter.
Co-reporter:Rongning Liang, Yan Zhao, Yang Su, Wei Qin
Talanta 2015 Volume 144() pp:115-121
Publication Date(Web):1 November 2015
DOI:10.1016/j.talanta.2015.05.064
•The dummy molecularly imprinted polymer for OH-PCBs has been synthesized.•The MISPE shows good recovery and high specific recognition ability for OH-PCBs.•The MISPE-LC–MS/MS system offers a fetomolar detection limit for OH-PCBs.•The proposed system has been applied to the detection of OH-PCBs in real water samples.Hydroxylated polychlorinated biphenyls (OH-PCBs) can be detected by liquid chromatography–mass spectrometry coupled to solid-phase extraction (SPE) using a dummy molecularly imprinted polymer (DMIP) as a sorbent. The DMIP is prepared by using an analogue of OH-PCBs (i.e., 4, 4-dihydroxybiphenyl) as a dummy template, to avoid the leakage of the target molecules. The DMIP-SPE sorbent shows good recoveries for OH-PCBs at pH 11 due to the charge-assisted hydrogen bondings between OH-PCBs and the DMIP. It has been found that the DMIP is much more effective and selective than the traditional C18-SPE method. The sample pH, polymer dosage, elution solvent and volume have been optimized for higher recoveries. Under the optimum experimental conditions, OH-PCBs can be detected in the linear concentration range of 0.05–1.0 pM, with the detection limits ranging from 11 fM to 82 fM for 4′-OH-CB 9, 4′-OH-CB 30, 4′-OH-CB 61, 4′-OH-CB 106 and 4′-OH-CB 112. The proposed system has been successfully applied to the determination of trace OH-PCBs in spiked water samples with recoveries in the range of 89–110%.
Co-reporter:Xuewei Wang, Yangang Yang, Long Li, Mingshuang Sun, Haogen Yin, and Wei Qin
Analytical Chemistry 2014 Volume 86(Issue 9) pp:4416
Publication Date(Web):April 7, 2014
DOI:10.1021/ac500281r
The oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) has great utility in bioanalysis such as peroxidase/peroxidase mimetic-based biosensing. In this paper, the behaviors of TMB oxidation intermediates/products in liquid/liquid biphasic systems have been investigated for the first time. The free radical, charge transfer complex, and diimine species generated by TMB oxidation are all positively charged under acidic and near-neutral conditions. Electron paramagnetic resonance and visible absorbance spectroscopy data demonstrate that these cationic species can be effectively transferred from an aqueous phase into a water-immiscible liquid phase functionalized by an appropriate cation exchanger. Accordingly, sensitive potential responses of TMB oxidation have been obtained on a cation exchanger-doped polymeric liquid membrane electrode under mildly acidic and near-neutral conditions. By using the membrane electrode responsive to TMB oxidations, two sensitive potentiometric biosensing schemes including the peroxidase-labeled sandwich immunoassay and G-quadruplex DNAzyme-based DNA hybridization assay have been developed. The obtained detection limits for the target antigen and DNA are 0.02 ng/mL and 0.1 nM, respectively. Coupled with other advantages such as low cost, high reliability, and ease of miniaturization and integration, the proposed polymeric liquid membrane electrode holds great promise as a facile and efficient transducer for TMB oxidation and related biosensing applications.
Co-reporter:Xuewei Wang, Dengfeng Yue, Enguang Lv, Lei Wu, and Wei Qin
Analytical Chemistry 2014 Volume 86(Issue 4) pp:1927
Publication Date(Web):January 31, 2014
DOI:10.1021/ac500028v
The tremendous applications of boronic acids (BAs) in chemical sensing, medical chemistry, molecular assembly, and organic synthesis lead to an urgent demand for developing effective sensing methods for BAs. This paper reports a facile and sensitive potentiometric sensor scheme for heterogeneous detection of BAs based on their unexpected potential responses on quaternary ammonium salt-doped polymeric liquid membranes. 11B NMR data reveal that a quaternary ammonium chloride can trigger the hydrolysis of an electrically neutral BA in an aprotic solvent. Using the quaternary ammonium salt as the receptor, the BA molecules can be extracted from the sample solution into the polymeric membrane phase and undergo the concomitant hydrolysis. Such salt-triggered hydrolysis generates H+ ions, which can be coejected into the aqueous phase with the counterions (e.g., Cl–) owing to their high hydrophilicities. The perturbation on the ionic partition at the sample–membrane interface changes the phase boundary potential and thus enables the potentiometric sensing of BAs. In contrast to other transduction methods for BAs, for which labeled or separate reporters are exclusively required, the present heterogeneous sensing scheme allows the direct detection of BAs without using any reporter molecules. This technique shows superior detection limits for BAs (e.g., 1.0 × 10–6 M for phenylboronic acid) as compared to previously reported methods based on colorimetry, fluorimetry, and mass spectrometry. The proposed sensing strategy has also been successfully applied to potentiometric indication of the BA reactions with hydrogen peroxide and saccharides, which allows indirect and sensitive detection of these important species.
Co-reporter:Jiawang Ding, Jiahong Lei, Xia Ma, Jun Gong, and Wei Qin
Analytical Chemistry 2014 Volume 86(Issue 19) pp:9412
Publication Date(Web):September 14, 2014
DOI:10.1021/ac502335g
Exposure to pathogens in recreational or drinking water is a serious public health concern. It is important to rapidly determine and identify trace levels of pathogens in real environmental samples. We report here on a label-free potentiometric aptasensor for rapid, sensitive, and selective detection of Listeria monocytogenes (LM), a pathogen widely distributed in the environment. An aptamer binds specifically to internalin A, a surface protein present in LM cells. The target-binding event prevents the aptamer from electrostatically interacting with protamine, which can be sensitively detected using a polycation-sensitive membrane electrode. Using this method, LM can be detected down to 10 CFU mL–1. Coupled to an online filtration system, the bioassay has been evaluated with spiked coastal seawater samples and shows good recovery and high accuracy. This work demonstrates the possibility of developing potentiometric aptasensors for determination and identification of various bacteria in environmental samples.
Co-reporter:Tanji Yin, Dawei Pan, and Wei Qin
Analytical Chemistry 2014 Volume 86(Issue 22) pp:11038
Publication Date(Web):October 16, 2014
DOI:10.1021/ac5029209
A new type of all-solid-state polymeric membrane ion-selective electrodes (ISEs) is developed by using a nanoporous gold (NPG) film as solid contact. The NPG film is in situ formed on the surface of a gold wire electrode by the multicyclic electrochemical alloying/dealloying method. The characteristics of the NPG film, such as the large surface area, high double layer capacitance, and good conductivity, have been demonstrated by cyclic voltammetry and electrochemical impedance spectroscopy. The NPG film offers a well-defined interface between the electronic conductor and the ion-selective membrane. The NPG film-based all-solid-state K+ ISE shows a stable Nernstian response within the concentration range from 10–6 to 10–2 M, and the detection limit is 4.0 × 10–7 M. The proposed electrode exhibits an improved potential stability with a reduced water layer in comparison with the coated-wire K+-ISE, which is due to the bicontinuous electron- and ion-conducting properties of the ionophore-doped polymeric membrane/NPG film interlayer. Unlike the additionally coated intermediate layers as single-use solid contacts, the in situ formed NPG film as solid contact is reusable. This work provides a versatile method for fabricating the robust, reliable, and low-maintenance miniaturized ISEs.
Co-reporter:Jiawang Ding, Hongxia Zhang, Falong Jia, Wei Qin, Dan Du
Sensors and Actuators B: Chemical 2014 199() pp: 284-290
Publication Date(Web):
DOI:10.1016/j.snb.2014.04.012
Co-reporter:Jiawang Ding, Xuewei Wang, and Wei Qin
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 19) pp:9488
Publication Date(Web):September 9, 2013
DOI:10.1021/am402245f
Pulsed galvanostatic control of ion fluxes across polymeric membrane ion-selective electrodes (ISEs) is an emerging field for potentiometric sensing. Herein we report a novel potentiometric enzyme immunoassay based on current-controlled release of an enzyme substrate, which eliminates the addition of marker ions in the sample solution. In this method, the carboxylated poly(vinyl chloride) matrix at the outer layer of the ISE membrane is employed to attach a primary antibody. A sandwich immunoassay with an alkaline phosphatase labeled antibody (ALP-Ab) as the reporter is used for the determination of human IgG (as a model protein). The large difference between the lipophilicity of the substrate ion and that of the product ion allows p-nitrophenyl phosphate to be used as the enzyme substrate for potentiometric immunosensors. After the immunoreactions, the captured ALP-Ab catalyzes the hydrolysis of the substrate ions released at the sample–membrane interface by using the pulsed galvanostatic technique. This process can be potentiometrically determined by measuring the open circuit potential of the ISE. Under optimal conditions, the potential response of the proposed immunosensor is proportional to the concentration of human IgG in the range of 50–1000 ng/mL with a detection limit of 30 ng/mL (3σ). Owing to simplicity and independence of sample volume and sample turbidity, the proposed potentiometric immunoassay offers a viable alternative to those based on optical absorbance.Keywords: immunoassays; polymeric membrane electrodes; potentiometry; pulsed galvanostatic technique; sample-membrane interface;
Co-reporter:Xuewei Wang, Zhaofeng Ding, Qingwei Ren, and Wei Qin
Analytical Chemistry 2013 Volume 85(Issue 3) pp:1945
Publication Date(Web):January 5, 2013
DOI:10.1021/ac3035629
The first potentiometric transducer for G-quadruplex/hemin DNAzyme-based biosensing has been developed by using potential responses of electrically neutral oligomeric phenols on polymeric membrane electrodes. In the presence of G-quadruplex/hemin DNAzyme and H2O2, monomeric phenols (e.g., phenol, methylphenols, and methoxyphenols) can be condensed into oligomeric phenols. Because both substrates and products are nonionic under optimal pH conditions, these reactions are traditionally not considered in designing potentiometric biosensing schemes. However, in this paper, the electrically neutral oligomeric phenols have been found to induce highly sensitive potential responses on quaternary ammonium salt-doped polymeric membrane electrodes owing to their high lipophilicities. In contrast, the potential responses to monomeric phenolic substrates are rather low. Thus, the G-quadruplex/hemin DNAzyme-catalyzed oxidative coupling of monomeric phenols can induce large potential signals, and the catalytic activities of DNAzymes can be probed. A comparison of potential responses induced by peroxidations of 13 monomeric phenols indicates that p-methoxyphenol is the most efficient substrate for potentiometric detection of G-quadruplex/hemin DNAzymes. Finally, two label-free and separation-free potentiometric DNA assay protocols based on the G-quadruplex/hemin DNAzyme have been developed with sensitivities higher than those of colorimetric and fluorometric methods. Coupled with other features such as reliable instrumentation, low cost, ease of miniaturization, and resistance to color and turbid interferences, the proposed polymeric membrane-based potentiometric sensor promises to be a competitive transducer for peroxidase-mimicking DNAzyme-involved biosensing.
Co-reporter:Xuewei Wang; Wei Qin
Chemistry - A European Journal 2013 Volume 19( Issue 30) pp:9979-9986
Publication Date(Web):
DOI:10.1002/chem.201300284
Abstract
The determination of peroxidase activities is the basis for enzyme-labeled bioaffinity assays, peroxidase-mimicking DNAzymes- and nanoparticles-based assays, and characterization of the catalytic functions of peroxidase mimetics. Here, a facile, sensitive, and cost-effective solvent polymeric membrane-based peroxidase detection platform is described that utilizes reaction intermediates with different pKa values from those of substrates and final products. Several key but long-debated intermediates in the peroxidative oxidation of o-phenylenediamine (o-PD) have been identified and their charge states have been estimated. By using a solvent polymeric membrane functionalized by an appropriate substituted tetraphenylborate as a receptor, those cationic intermediates could be transferred into the membrane from the aqueous phase to induce a large cationic potential response. Thus, the potentiometric indication of the o-PD oxidation catalyzed by peroxidase or its mimetics can be fulfilled. Horseradish peroxidase has been detected with a detection limit at least two orders of magnitude lower than those obtained by spectrophotometric techniques and traditional membrane-based methods. As an example of peroxidase mimetics, G-quadruplex DNAzymes were probed by the intermediate-sensitive membrane and a label-free thrombin detection protocol was developed based on the catalytic activity of the thrombin-binding G-quadruplex aptamer.
Co-reporter:Tanji Yin, Wei Qin
TrAC Trends in Analytical Chemistry 2013 Volume 51() pp:79-86
Publication Date(Web):November 2013
DOI:10.1016/j.trac.2013.06.009
•We highlight the unique properties of nanomaterials as solid contacts.•We describe potentiometric sensors based on ionophore-modified nanomaterials.•We present recent developments in nanomaterial-based potentiometric biosensors.Nanomaterials play an important role in the fabrication of chemosensors and biosensors, due to their unique physical and chemical properties, such as large surface area/volume ratio, good conductivity, excellent electrocatalytic activity and high mechanical strength. We review recent advances in the applications of these nanomaterials in potentiometric sensors. We highlight the development of stable solid-state polymeric membrane ion-selective electrodes (ISEs). We describe ISEs based on ionophore-modified nanomaterials. Also, we present highly-sensitive potentiometric biosensors based on nanomaterials.
Co-reporter:Jiawang Ding, Wei Qin
Biosensors and Bioelectronics 2013 Volume 47() pp:559-565
Publication Date(Web):15 September 2013
DOI:10.1016/j.bios.2013.03.066
•Potentiometric sensing of nuclease activities and oxidative DNA damage is proposed.•Protamine is used as an indicator.•Protamine-sensitive membrane electrode is used as a detector.•Measurements can be done with a titration mode or a direct detection mode.A simple, general and label-free potentiometric method to measure nuclease activities and oxidative DNA damage in a homogeneous solution using a polycation-sensitive membrane electrode is reported. Protamine, a linear polyionic species, is used as an indicator to report the cleavage of DNA by nucleases such as restriction and nonspecific nucleases, and the damage of DNA induced by hydroxyl radicals. Measurements can be done with a titration mode or a direct detection mode. For the potentiometric titration mode, the enzymatic cleavage dramatically affects the electrostatical interaction between DNA and protamine and thus shifts the response curve for the potentiometric titration of the DNA with protamine. Under the optimized conditions, the enzyme activities can be sensed potentiometrically with detection limits of 2.7×10−4 U/µL for S1 nuclease, and of 3.9×10−4 U/µL for DNase I. For the direct detection mode, a biocomplex between protamine and DNA is used as a substrate. The nuclease of interest cleaves the DNA from the protamine/DNA complex into smaller fragments, so that free protamine is generated and can be detected potentiometrically via the polycation-sensitive membrane electrode. Using a direct measurement, the nuclease activities could be rapidly detected with detection limits of 3.2×10−4 U/µL for S1 nuclease, and of 4.5×10−4 U/µL for DNase I. Moreover, the proposed potentiometric assays demonstrate the potential applications in the detection of hydroxyl radicals. It is anticipated that the present potentiometric strategy will provide a promising platform for high-throughput screening of nucleases, reactive oxygen species and the drugs with potential inhibition abilities.
Co-reporter:Jiawang Ding, Wei Qin, Yan Zhang, Xuewei Wang
Biosensors and Bioelectronics 2013 Volume 45() pp:148-151
Publication Date(Web):15 July 2013
DOI:10.1016/j.bios.2013.01.052
In this article, we introduce a general, sensitive, facile, and label-free potentiometric assay based on metal-mediated DNA base pairs. A nucleic acid with one adenosine-5′-triphosphate (ATP) binding sequence (aptamer) in the middle and two cytosine(C)-rich sequences at the lateral portions was employed as a model. A rigid hairpin structure can be formed in the presence of Ag+ ions, in which the C residues of the spatially separated nucleotides are linked by the ions. The strong interaction between Ag+ ions and cytosines forms a stable C–Ag+–C structure, which could reduce the concentration of silver ions released from the polymeric membrane silver ion-selective electrode (ISE) at the sample–membrane interface and decrease the potential response. In the presence of its target, the aptamer (the loop sequence of the probe) binds specifically to the target via reaction incubation. Such target-binding induced aptamer conformational change prevents the formation of C–Ag+–C structure, leaving more silver ions at the sample–membrane interface, which can be detected by the silver ISE. ATP can be quantified in the range of 0.5–3.0 μM with a detection limit of 0.37 μM. The relative standard deviation for 5 μM ATP is 5.5%. For the proposed method, the combination of using ion fluxes of silver ions as modulating reagents and as signal reporters greatly simplifies the detection procedures. In addition, by changing the binding sequence in the middle of the probe, the present detection method will be able to explore new applications of ISE for the detection of a large variety of targets.Highlights► A label-free potentiometric assay based on metal–DNA base pairs is proposed. ► Ag+ ions interacting with the C–C mismatch in the DNA probe serve as a signal reporter. ► The target-binding induced conformational change prevents the formation of C–Ag+–C structure. ► The ion fluxes of a silver ion-selective electrode are used for potentiometric aptasensing.
Co-reporter:Xuewei Wang and Wei Qin
Chemical Communications 2012 vol. 48(Issue 34) pp:4073-4075
Publication Date(Web):05 Mar 2012
DOI:10.1039/C2CC31020A
Reactive intermediates rather than stable reactants or products have been found to induce large potential responses on an appropriately formulated polymeric membrane electrode, which provides a novel methodology for ultrasensitive potentiometric biosensing based on the horseradish peroxidase-H2O2 oxidation reaction.
Co-reporter:Wei Qin, Rongning Liang, Xiuli Fu, Qianwen Wang, Tanji Yin, and Wenjing Song
Analytical Chemistry 2012 Volume 84(Issue 24) pp:10509
Publication Date(Web):November 19, 2012
DOI:10.1021/ac3024312
Polymeric membrane ion-selective electrodes (ISEs) have become attractive tools for trace-level environmental and biological measurements. However, applications of such ISEs are often limited to measurements with low levels of electrolyte background. This paper describes an asymmetric membrane rotating ISE configuration for trace-level potentiometric detection with a high-interfering background. The membrane electrode is conditioned in a solution of interfering ions (e.g., Na+) so that no primary ions exist in the ISE membrane, thus avoiding the ion-exchange effect induced by high levels of interfering ones in the sample. When the electrode is in contact with the primary ions, the interfering ions in the membrane surface can be partially displaced by the primary ions due to the favorable ion–ligand interaction with the ionophore in the membrane, thus causing a steady-state potential response. By using the asymmetric membrane with an ion exchanger loaded on the membrane surface, the diffusion of the primary ions from the organic boundary layer into the bulk of the membrane can be effectively blocked; on the other hand, rotation of the membrane electrode dramatically reduces the diffusion layer thickness of the aqueous phase and significantly promotes the mass transfer of the primary ions to the sample–membrane interface. The induced accumulation of the primary ions in the membrane boundary layer largely enhances the nonequilibrium potential response. By using copper as a model, the new concept offers a subnanomolar detection limit for potentiometric measurements of heavy metals with a high electrolyte background of 0.5 M NaCl.
Co-reporter:Jiawang Ding, Yan Chen, Xuewei Wang, and Wei Qin
Analytical Chemistry 2012 Volume 84(Issue 4) pp:2055-2061
Publication Date(Web):January 22, 2012
DOI:10.1021/ac2024975
A potentiometric label-free and substrate-free (LFSF) aptasensing strategy which eliminates the labeling, separation, and immobilization steps is described in this paper. An aptamer binds specifically to a target molecule via reaction incubation, which could induce a change in the aptamer conformation from a random coil-like configuration to a rigid folded structure. Such a target binding-induced aptamer conformational change effectively prevents the aptamer from electrostatically interacting with the protamine binding domain. This could either shift the response curve for the potentiometric titration of the aptamer with protamine as monitored by a conventional polycation-sensitive membrane electrode or change the current-dependent potential detected by a protamine-conditioned polycation-sensitive electrode with the pulsed current-driven ion fluxes of protamine across the polymeric membrane. Using adenosine triphosphate (ATP) as a model analyte, the proposed concept offers potentiometric detection of ATP down to the submicromolar concentration range and has been applied to the determination of ATP in HeLa cells. In contrast to the current LFSF aptasensors based on optical detection, the proposed strategy allows the LFSF biosensing of aptamer/target binding events in a homogeneous solution via electrochemical transduction. It is anticipated that the proposed strategy will lay a foundation for development of potentiometric sensors for LFSF aptasensing of a variety of analytes where target binding-induced conformational changes such as the formation of folded structures and the opening of DNA hairpin loops are involved.
Co-reporter:Yan Chen, Jiawang Ding and Wei Qin
Analyst 2012 vol. 137(Issue 8) pp:1944-1949
Publication Date(Web):22 Feb 2012
DOI:10.1039/C2AN35176E
A polycation-selective polymeric membrane electrode using dinonylnaphthalene sulfonate as an ion exchanger has been developed as a protamine controlled-release system for potentiometric detection of heparin. The incorporation of tetradodecylammonium tetrakis(4-chlorophenyl)borate as a lipophilic salt in the membrane dramatically improves the sensor's selectivity towards protamine over sodium ions via influencing the activity coefficient of protamine in the membrane, and a stable potential baseline can be obtained in the presence of an electrolyte background. The electrostatic binding interaction between heparin and protamine decreases the concentration of free protamine released at the sample–membrane interface and facilitates the stripping of protamine out of the membrane surface via the ion-exchange process with sodium ions, thus decreasing the membrane potential. Under optimal conditions, the proposed polymeric membrane electrode exhibits a linear relationship between the initial slope of the potential change and the heparin concentration in the range of 0.025–1.25 U mL−1 with an improved detection limit of 0.01 U mL−1.
Co-reporter:Yan Chen, Rong Ning Liang, Wei Qin
Chinese Chemical Letters 2012 Volume 23(Issue 2) pp:233-236
Publication Date(Web):February 2012
DOI:10.1016/j.cclet.2011.10.021
A polymeric membrane ion-selective electrode for determination of heparin is described in this paper. Protamine is incorporated into the organic membrane phase and functions as sensing element for selective recognition of heparin. The proposed membrane electrode exhibits high selectivity for heparin over lipophilic anions such as thiocyanide and salicylate. The potentiometric response to the concentration of heparin is linear in the range of 0.01–0.4 U/mL and a lower detection limit of 0.005 U/mL can be achieved.
Co-reporter:Wen-Jing SONG, Xue-Wei WANG, Jia-Wang DING, Jun ZHANG, Rui-Ming ZHANG, Wei QIN
Chinese Journal of Analytical Chemistry 2012 Volume 40(Issue 5) pp:670-674
Publication Date(Web):May 2012
DOI:10.1016/S1872-2040(11)60545-8
A novel electrochemical flow sensing system for determination of heavy metals in seawater is described in this paper. Processes including on-line filtration, UV digestion, electrochemical enrichment, and ion-selective electrode potentiometric detection are involved in the system for sensitive, selective and rapid detection. For measurements of cadmium, lead and copper ions in seawater matrix, the linear response ranges are 1.0 × 10−9−1.0 × 10−7 M, 3.0 × 10−9−1.0 × 10−7 M and 1.0 × 10−9−1.0 × 10−7 M, respectively with the corresponding detection limits of 2.8 × 10−10, 6.6 × 10−10 and 5.1 × 10−10 M. For six successive measurements, the system showed relative standard deviations of less than 5%. The whole analysis process could be completed within 25 min. The system was applied to determination of heavy metals in seawater and the results agreed with those obtained by stripping voltammetry. With advantages of simplicity, accuracy and low cost, the sensing system offers promising potentials for on-site analysis of heavy metals in seawater.
Co-reporter:Rong-Ning LIANG, Qi GAO, Wei QIN
Chinese Journal of Analytical Chemistry 2012 Volume 40(Issue 3) pp:354-358
Publication Date(Web):March 2012
DOI:10.1016/S1872-2040(11)60535-5
A polymeric membrane ion-selective electrode for determination of clenbuterol is described. It is based on a molecularly imprinted polymer as an ionophore for molecular recognition, which can be synthesized by precipitation polymerization using clenbuterol hydrochloride as the template molecule. Under optimized conditions, the proposed membrane electrode exhibits Nernstian response to the protonated clenbuterol over the concentration range of 1.0 × 10−7 M to 1.0 × 10−4 M with a slope of 55.7 mV/dec., and a detection limit of 7.0 × 10−8 M. The MIP-based sensor shows excellent selectivity, rapid response time and satisfactory long-term stability. The potentiometric sensor has been successfully applied to the determination of clenbuterol in pig urine samples with recoveries between 98% and 107% and an analysis time of less than 3 min.
Co-reporter:Tanji Yin;Dawei Pan
Journal of Solid State Electrochemistry 2012 Volume 16( Issue 2) pp:499-504
Publication Date(Web):2012 February
DOI:10.1007/s10008-011-1358-z
Conducting polymer poly(pyrrole) (PPy) doped with Nafion was successfully used as ion-to-electron transducer in the construction of a solid-contact Pb2+-selective polymeric membrane electrode. The Nafion dopant can effectively increase the capacitance of the conducting polymer and improve the mechanical robustness of the coating. The transducer layer, PPy-Nafion, characterized by cyclic voltammetry and electrochemical impedance spectroscopy, exhibits a sufficiently high bulk (redox) capacitance and fast ion and electron transport process. The new Pb2+-selective polymeric membrane electrode, based on PPy-Nafion film as solid contact, shows stable Nernstian characteristics in Pb(NO3)2 solution within the concentration range of 1.0 × 10−7–1.0 × 10−3 M, and the detection limit is 4.3 × 10−8 M. The potential stability of the electrode and the influence of the interfacial water layer were also evaluated by chronopotentiometry and potentiometric water layer test, respectively. The results show that the solid-contact Pb2+-selective electrode, based on PPy-Nafion film as ion-to-electron transducer, can effectively overcome the potential drift and reduce the water layer between the PPy-Nafion transducer layer and the ion-selective membrane.
Co-reporter:Xuewei Wang, Qing Wang, Wei Qin
Biosensors and Bioelectronics 2012 Volume 38(Issue 1) pp:145-150
Publication Date(Web):October–December 2012
DOI:10.1016/j.bios.2012.05.020
Traditional potentiometric polyion-sensitive electrodes can only work effectively in samples with vigorous convection fulfilled by magnetic stirrer, electrode rotator, or other moving components. The dependence on complex moving parts prohibits the fabrication of compact, cost-effective, and energy-effective test devices from the commercial point of view. In this paper, a novel potentiometric sensing protocol without using any moving parts has been proposed for polycationic protamine. In contrast to traditional protamine-sensitive electrodes conditioned by discriminated ion (Na+), the proposed electrode is conditioned with primary ion (protamine). Upon a medium exchange from the conditioning solution into an unstirred sample solution without protamine, protamine loaded in the membrane is stripped into the aqueous phase via ion exchange with aqueous sodium ion, thereby inducing a large potential drop. Interestingly, when the sample solution initially contains protamine, the ion-exchange process has been found to be sensitively inhibited by the sample protamine, and thus the potential drop is suppressed, which forms the basis of the moving-part-free potentiometric polyion sensing strategy. Utilizing the digestion ability of protease to protamine, the electrode was employed to determine the activity of trypsin with a detection limit at least one order of magnitude lower than traditional potentiometric methods. The trypsin inhibitor in both buffer and plasma samples was also sensitively detected with the moving-part-free protamine-sensitive electrode. Finally, the ability of the proposed electrode to detect polyanionic heparin was demonstrated.Highlights► A sensing principle based on stripping of protamine from a membrane is proposed. ► Concept allows potentiometric measurements to be done without any moving parts. ► Trypsin and its inhibitors can be sensitively detected by the proposed electrode. ► Heparin can be measured by the electrode based on its interaction with protamine.
Co-reporter:Yan Chen, Jiawang Ding, Wei Qin
Bioelectrochemistry 2012 Volume 88() pp:144-147
Publication Date(Web):December 2012
DOI:10.1016/j.bioelechem.2012.04.002
A potentiometric biosensor for the determination of trypsin is described based on current-controlled reagent delivery. A polymeric membrane protamine-sensitive electrode with dinonylnaphthalene sulfonate as cation exchanger is used for in situ generation of protamine. Diffusion of protamine across the polymeric membrane can be controlled precisely by applying an external current. The hydrolysis catalyzed with trypsin in sample solution decreases the concentration of free protamine released at the sample–membrane interface and facilitates the stripping of protamine out of the membrane surface via the ion-exchange process with sodium ions from the sample solution, thus decreasing the membrane potential, by which the protease can be sensed potentiometrically. The influences of anodic current amplitude, current pulse duration and protamine concentration in the inner filling solution on the membrane potential response have been studied. Under optimum conditions, the proposed protamine-sensitive electrode is useful for continuous and reversible detection of trypsin over the concentration range of 0.5–5 U mL− 1 with a detection limit of 0.3 U mL− 1. The proposed detection strategy provides a rapid and reagentless way for the detection of protease activities and offers great potential in the homogeneous immunoassays using proteases as labels.Highlights► A protamine-sensitive electrode is used for in situ generation of protamine. ► Diffusion of protamine across the membrane can be controlled with a current. ► The hydrolysis catalyzed with trypsin in sample solution consumes the protamine. ► The decrease in the protamine concentration decreases the membrane potential.
Co-reporter:Wenjing Song, Jiawang Ding, Rongning Liang, Wei Qin
Analytica Chimica Acta 2011 Volume 704(1–2) pp:68-72
Publication Date(Web):17 October 2011
DOI:10.1016/j.aca.2011.08.004
A polymeric membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the polymeric membrane can be controlled precisely. The permanganate ions released at the sample-membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured membrane potential, by which the reductant can be sensed potentiometrically. Ascorbate, dopamine and norepinephrine have been employed as the model reductants. Under the optimized conditions, the potential peak heights are proportional to the reductant concentrations in the ranges of 1.0 × 10−5 to 2.5 × 10−7 M for ascorbate, of 1.0 × 10−5 to 5.0 × 10−7 M for dopamine, and of 1.0 × 10−5 to 5.0 × 10−7 M for norepinephrine, respectively with the corresponding detection limits of 7.8 × 10−8, 1.0 × 10−7 and 1.0 × 10−7 M. The proposed system has been successfully applied to the determination of reductants in pharmaceutical preparations and vegetables, and the results agree well with those of iodimetric analysis.Graphical abstractA polymeric membrane permanganate-selective electrode has been developed as a current-controlled reagent release system for potentiometric detection of reductants in flow injection analysis. By applying an external current, diffusion of permanganate ions across the polymeric membrane can be controlled precisely. The permanganate ions released at the sample-membrane interface from the inner filling solution of the electrode are consumed by reaction with a reductant in the sample solution thus changing the measured membrane potential, by which the reductant can be sensed potentiometrically.Highlights► A novel reagentless sensor is developed for consecutive detection of reductants in FIA. ► The ion-selective electrode is used as a permanganate controlled-release system. ► The amount of permanganate released at the membrane surface can be controlled precisely by an external current. ► The recovery of the sensor is rapid.
Co-reporter:Shunyang Yu, Fuhai Li, Tanji Yin, Yongming Liu, Dawei Pan, Wei Qin
Analytica Chimica Acta 2011 Volume 702(Issue 2) pp:195-198
Publication Date(Web):30 September 2011
DOI:10.1016/j.aca.2011.06.049
In this work, a novel all-solid-state polymeric membrane Pb2+-selective electrode was developed by using for the first time poly(2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene) (MEH-PPV) as solid contact. To demonstrate the ion-to-electron transducing ability of MEH-PPV, chronopotentiometry and electrochemical impedance spectroscopy measurements were carried out. The proposed electrodes showed a Nernstian response of 29.1 mV decade−1 and a lower detection limit of subnanomolar level. No water film was observed with the conventional plasticized PVC membrane. This work demonstrates a new strategy for the fabrication of robust potentiometric ion sensors.Graphical abstractHighlights► All reagents used for the electrodes preparation were commercially available. ► The lower detection limit of the proposed electrode reached subnanomolar levels. ► No water film was observed with conventional commercially available PVC ion-sensing membranes. ► This research provides an excellent strategy for fabrication of robust polymeric ion sensors.
Co-reporter:Shunyang Yu, Fuhai Li, Wei Qin
Sensors and Actuators B: Chemical 2011 Volume 155(Issue 2) pp:919-922
Publication Date(Web):20 July 2011
DOI:10.1016/j.snb.2011.01.052
A new all-solid-state Cd2+-selective electrode with a low detection limit was prepared by using conjugated thiophene oligomer α-sexithiophene (α-6T) as solid contact deposited between an ionophore-doped poly(vinyl chloride) membrane and a gold disc substrate. The electrode exhibited a Nernstian response for Cd2+ ions over a wide concentration range of 10−3–10−7 M with a detection limit as low as 1.3 × 10−8 M. Results showed that the fabricated potentiometric sensor was suitable for use within the pH range of 2.0–9.0 and exhibited good reproducibility for long-term measurements.
Co-reporter:Lin Jiang, Yuane Wang, Jiawang Ding, Tingting Lou, Wei Qin
Electrochemistry Communications 2010 Volume 12(Issue 2) pp:202-205
Publication Date(Web):February 2010
DOI:10.1016/j.elecom.2009.11.024
A novel ionophore–Nafion modified bismuth electrode is described for sensitive and selective anodic stripping analysis of cadmium(II). The electrode is prepared by coating the glassy carbon electrode with the cadmium ionophore N,N,N′,N′-tetrabutyl-3,6-dioxaoctanedi(thioamide) and Nafion composite. Bismuth is deposited in situ on the electrode surface by plating simultaneously with cadmium in sample solution. Numerous key variables affecting the current response of cadmium have been optimized. The electrode has a linear concentration range of 0.5–10 nM with a deposition time of 180 s. The detection limit is 1.3 × 10−10 M and the relative standard deviations for 0.5 and 7 nM cadmium are 6.5% and 4.5%, respectively. The proposed electrode shows excellent selectivity over other heavy metals, such as copper, lead and indium. The attractive performance of such electrode offers a feasible way to monitor trace cadmium(II) rapidly and precisely in complex matrixes.
Co-reporter:Jun Zhang, Shun Yang Yu, Tan Ji Yin, Xue Feng Hu, Wei Qin
Chinese Chemical Letters 2010 Volume 21(Issue 4) pp:464-467
Publication Date(Web):April 2010
DOI:10.1016/j.cclet.2009.11.028
Four 20-membered N2S4-monoazathiacrown ethers have been synthesized and explored as neutral ionophores for Ag+-selective electrodes. Potentiometric responses reveal that the flexibility of the ligands has great effect on the selectivity and sensitivity to Ag+ ions. The electrode based on ionophore 9,10,20,25-tetrahydro-5H,12H-tribenzo[b,n,r][1,7,10,16,4,13]tetrathiadiaza cycloicosine 6,13-(7H,14H)-dione (C) with 2-nitrophenyl octyl ether (o-NPOE) as solvent in a poly(vinyl chloride) (PVC) membrane matrix shows a measuring range of 1.0 × 10−6 to 1.0 × 10−3 mol/L with a Nernstian slope of 54.9 ± 0.3 mV/decade. This electrode has high selectivity for Ag+ with negligible interference from many other cations and can be used in a wide pH range of 3.6–9.2.
Co-reporter:De An Song, Rong Ning Liang, Rui Ming Zhang, Jia Wang Ding, Jun Zhang, Wei Qin
Chinese Chemical Letters 2010 Volume 21(Issue 11) pp:1378-1381
Publication Date(Web):November 2010
DOI:10.1016/j.cclet.2010.06.003
A novel potentiometric detection strategy based on functionalized magnetic nanoparticles has been developed for rapid and sensitive sensing of polyions. Highly dispersed magnetic nanoparticles coated with ion exchanger and plasticizer could promote an in situ cooperative ion-pairing interaction between the ion exchanger and the polyion analyte in sample solution by dramatically reducing the mass-transfer distance. With applying a magnetic field, the nanoparticles can be attached to the surface of ion exchanger free polymeric membrane. The observed potential signals are related to the polyion concentrations. The proposed polymeric membrane electrode exhibits a linear relationship between the greatest potential response slope (dE/dt) and the logarithm of protamine concentration in the range of 0.05–5 μg/mL with a lower detection limit of 0.033 μg/mL.
Co-reporter:Jun Zhang, Jiawang Ding, Tanji Yin, Xuefeng Hu, Shunyang Yu, Wei Qin
Talanta 2010 Volume 81(Issue 3) pp:1056-1062
Publication Date(Web):15 May 2010
DOI:10.1016/j.talanta.2010.01.060
Nine monoazathiacrown ethers have been synthesized and explored as ionophores for polymeric membrane Ag+-selective electrodes. Potentiometric responses reveal that the ion-selective electrodes (ISEs) based on 2,2′-thiodiethanethiol derivatives can exhibit excellent selectivities toward Ag+. The plasticized poly(vinyl chloride) membrane electrode using 22-membered N2S5-ligand as ionophore has been characterized and its logarithmic selectivity coefficients for Ag+ over most of the interfering cations have been determined as <−8.0. Under optimal conditions, a lower detection limit of 2.2 × 10−10 M can be obtained for the membrane Ag+-ISE.
Co-reporter:Rong-Ning Liang;De-An Song;Rui-Ming Zhang
Angewandte Chemie 2010 Volume 122( Issue 14) pp:2610-2613
Publication Date(Web):
DOI:10.1002/ange.200906720
Co-reporter:Rong-Ning Liang;De-An Song;Rui-Ming Zhang
Angewandte Chemie International Edition 2010 Volume 49( Issue 14) pp:2556-2559
Publication Date(Web):
DOI:10.1002/anie.200906720
Co-reporter:Jiawang Ding
Journal of the American Chemical Society 2009 Volume 131(Issue 41) pp:14640-14641
Publication Date(Web):September 28, 2009
DOI:10.1021/ja906723h
A polymeric membrane ion-selective electrode (ISE) for rapid potentiometric biosensing has been developed. Butyrylcholinesterase, as a target enzyme, is immobilized on the surface of the polymeric membrane. A macro-command-controlled procedure for switching between the potentiostatic and galvanostatic steps has been designed to provide a current-driven release of the butyrylcholine substrate for in situ biosensing of the enzyme and its inhibitors. This system has the flexibility of trapping substrate ions in the ISE inner filling solution and provides rapid, continuous, and reproducible measurements of enzymes and other bioanalytes involved in enzymatic systems.
Co-reporter:Jiawang Ding and Wei Qin
Chemical Communications 2009 (Issue 8) pp:971-973
Publication Date(Web):19 Dec 2008
DOI:10.1039/B817064A
A novel reagentless biosensor has been developed in which the traditional ion selective electrode is used as a controlled-release system for in situ generation and detection of enzyme substrates.
Co-reporter:Dawei Pan, Yuane Wang, Zhaopeng Chen, Tingting Lou and Wei Qin
Analytical Chemistry 2009 Volume 81(Issue 12) pp:5088
Publication Date(Web):May 12, 2009
DOI:10.1021/ac900417e
A novel nanomaterial/ionophore-modified glassy carbon electrode for anodic stripping analysis of lead (Pb2+) is described. Nanosized hydroxyapatite (NHAP) with width of 20−25 nm and length of 50−100 nm has been prepared and used to improve the sensitivity for detection of Pb2+ because it provides unique three-dimensional network structure and has strong adsorption ability toward Pb2+. An ionophore, usually used in ion-selective electrodes, is utilized here for its excellent selectivity toward Pb2+. Nafion, a cation-exchange polymer, is employed as the conductive matrix in which NHAP and the ionophore can be tightly attached to the electrode surface. Such a designed NHAP/ionophore/Nafion-modified electrode shows remarkably improved sensitivity and selectivity to Pb2+. The electrode has a linear range of 5.0 nM to 0.8 μM with a 10 min accumulation time at open-circuit potential. The sensitivity and detection limit of the proposed sensor are 13 μA/μM and 1.0 nM, respectively. Interference from other heavy metal ions such as Cd2+, Cu2+, and Hg2+ associated with lead analysis can be effectively diminished. The practical application of the proposed sensor has been carried out for determination of trace levels of Pb2+ in real water samples.
Co-reporter:Yuane Wang;Dawei Pan;Xinming Li
Chinese Journal of Chemistry 2009 Volume 27( Issue 12) pp:2385-2391
Publication Date(Web):
DOI:10.1002/cjoc.201090013
Abstract
A bismuth/multi-walled carbon nanotube (Bi/MWNT) composite modified electrode for determination of cobalt by differential pulse adsorptive cathodic stripping voltammetry is described. The electrode is fabricated by potentiostatic pre-plating bismuth film on an MWNT modified glassy carbon (GC) electrode. The Bi/MWNT composite modified electrode exhibits enhanced sensitivity for cobalt detection as compared with the bare GC, MWNT modified and bismuth film electrodes. Numerous key experimental parameters have been examined for optimum analytical performance of the proposed electrode. With an adsorptive accumulation of the Co(II)-dimethylglyoxime complex at −0.8 V for 200 s, the reduction peak current is proportional to the concentration of cobalt in the range of 4.0×10−10−1.0×10−7 mol/L with a lower detection limit of 8.1×10−11 mol/L. The proposed method has been applied successfully to cobalt determination in seawater and lake water samples.
Co-reporter:Rongning Liang, Ruiming Zhang, Wei Qin
Sensors and Actuators B: Chemical 2009 Volume 141(Issue 2) pp:544-550
Publication Date(Web):7 September 2009
DOI:10.1016/j.snb.2009.05.024
A polymeric membrane ion-selective electrode for determination of melamine is described in this paper. It is based on a molecularly imprinted polymer (MIP) for selective recognition, which can be synthesized by using melamine as a template molecule, methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a cross-linking agent. The membrane electrode shows near-Nernstian response (54 mV/decade) to the protonated melamine over the concentration range of 5.0 × 10−6 to 1.0 × 10−2 mol L−1. The electrode exhibits a short response time of ∼16 s and can be stable for more than 2 months. Combined with flow analysis system, the potentiometric sensor has been successfully applied to the determination of melamine in milk samples. Interference from high concentrations of ions co-existing in milk samples such as K+ and Na+ can be effectively eliminated by on-line introduction of anion- and cation-exchanger tandem columns placed upstream, while melamine existing as neutral molecules in milk of pH 6.7 can flow through the ion-exchanger columns and be measured downstream by the proposed electrode in an acetate buffer solution of pH 3.7.
Co-reporter:Huimin Guo, Tanji Yin, Qingmei Su, Wei Qin
Talanta 2008 Volume 75(Issue 3) pp:851-855
Publication Date(Web):15 May 2008
DOI:10.1016/j.talanta.2007.12.023
A novel potentiometric method for the determination of ascorbate is described in this communication. It is based on ascorbate oxidation with permanganate which is continuously released from the inner reference solution of a ligand-free tridodecylmethylammonium chloride (TDMAC)-based polymeric membrane ion selective electrode (ISE). The ISE potential determined by the activity of permanganate ions released at the sample–membrane phase boundary is increased with the consumption of permanganate. The proposed membrane electrode is useful for continuous and reversible detection of ascorbate at concentrations in 0.1 M NaCl ranging from 1.0 × 10−6 to 1.0 × 10−3 M with a detection limit of 2.2 × 10−7 M.
Co-reporter:Xuewei Wang and Wei Qin
Chemical Communications 2012 - vol. 48(Issue 34) pp:NaN4075-4075
Publication Date(Web):2012/03/05
DOI:10.1039/C2CC31020A
Reactive intermediates rather than stable reactants or products have been found to induce large potential responses on an appropriately formulated polymeric membrane electrode, which provides a novel methodology for ultrasensitive potentiometric biosensing based on the horseradish peroxidase-H2O2 oxidation reaction.
Co-reporter:Jiawang Ding and Wei Qin
Chemical Communications 2009(Issue 8) pp:NaN973-973
Publication Date(Web):2008/12/19
DOI:10.1039/B817064A
A novel reagentless biosensor has been developed in which the traditional ion selective electrode is used as a controlled-release system for in situ generation and detection of enzyme substrates.
![[1,1'-Biphenyl]-4-ol,2',3,3',4',5'-pentachloro-](http://img.cochemist.com/ccimg/192200/192190-09-3.png)
![[1,1'-Biphenyl]-4-ol,2',3,3',4',5'-pentachloro-](http://img.cochemist.com/ccimg/192200/192190-09-3_b.png)
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