acents We highlight the unique properties of nanomaterials as solid contacts. acents We describe potentiometric sensors based on ionophore-modified nanomaterials. acents We present recent developments in nanomaterial-based potentiometric biosensors.
An all-solid-state polymeric membrane Ca super(2+)-selective electrode based on hydrophobic octadecylamine-functionalized graphene oxide has been developed. The hydrophobic composite in the ion-selective membrane not only acts as a transduction element to improve the potential stability for the all-solid-state Ca super(2+)-selective electrode, but also is used to immobilize Ca super(2+) ionophore with lipophilic side chains through hydrophobic interactions. The developed all-solid-state Ca super(2+)-selective electrode shows a stable potential response in the linear range of 3.010 super(-7)-1.010 super(-3)M with a slope of 24.7 plus or minus 0.3mV/dec, and the detection limit is (1.6 plus or minus 0.2 )10 super(-7)M (n=3). Additionally, due to the hydrophobicity and electrical conductivity of the composite, the proposed all-solid-state ion-selective electrode exhibits an improved stability with the absence of water layer between the ion-selective membrane and the underlying glassy carbon electrode. This work provides a simple, efficient and low-cost methodology for developing stable and robust all-solid-state ion-selective electrode with ionophore immobilization.
An all-solid-state polymeric membrane Pb(2+) ion-selective electrode (Pb(2+)-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 Pb(2+)-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 Pb(2+)-ISE has been applied to determine Pb(2+) in real water samples and the results agree well with those obtained by anodic stripping voltammetry.
An all-solid-state polymeric membrane potentiometric sensor for determination of bisphenol S has been developed by using the imprinted polymer as the receptor and a nanoporous gold film as the solid contact. The sensor has a linear concentration range of 0.1 to 2 μM with a detection limit of 0.04 μM. An all-solid-state polymeric membrane potentiometric sensor for sensitive and selective determination of bisphenol S is developed for the first time.
A potentiometric aptasensing assay that couples the DNA nanostructure-modified magnetic beads with a solid-contact polycation-sensitive membrane electrode for the detection of Vibrio alginolyticus is herein described. The DNA nanostructure-modified magnetic beads are used for amplification of the potential response and elimination of the interfering effect from a complex sample matrix. The solid-contact polycation-sensitive membrane electrode using protamine as an indicator is employed to chronopotentiometrically detect the change in the charge or DNA concentration on the magnetic beads, which is induced by the interaction between Vibrio alginolyticus and the aptamer on the DNA nanostructures. The present potentiometric aptasensing method shows a linear range of 10-100 CFU mL-1 with a detection limit of 10 CFU mL-1, and a good specificity for the detection of Vibrio alginolyticus. This proposed strategy can be used for the detection of other microorganisms by changing the aptamers in the DNA nanostructures.
An all-solid-state polymeric membrane Ca2+-selective electrode based on hydrophobic octadecylamine-functionalized graphene oxide has been developed. The hydrophobic composite in the ion-selective membrane not only acts as a transduction element to improve the potential stability for the all-solid-state Ca2+-selective electrode, but also is used to immobilize Ca2+ ionophore with lipophilic side chains through hydrophobic interactions. The developed all-solid-state Ca2+-selective electrode shows a stable potential response in the linear range of 3.0x10(-7)-1.0x10(-3)M with a slope of 24.7 +/- 0.3mV/dec, and the detection limit is (1.6 +/- 0.2 )x10(-7)M (n=3). Additionally, due to the hydrophobicity and electrical conductivity of the composite, the proposed all-solid-state ion-selective electrode exhibits an improved stability with the absence of water layer between the ion-selective membrane and the underlying glassy carbon electrode. This work provides a simple, efficient and low-cost methodology for developing stable and robust all-solid-state ion-selective electrode with ionophore immobilization.
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 O-2, 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. (C) 2016 Elsevier B.V. All rights reserved.
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 cydic 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 x 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 polymenc 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.
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. (C) 2014 Elsevier B.V. All rights reserved.
Conducting polymer poly(pyrrole) (PPy) doped with Nafion was successfully used as ion-to-electron transducer in the construction of a solid-contact Pb.sup.2+-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 Pb.sup.2+-selective polymeric membrane electrode, based on PPy-Nafion film as solid contact, shows stable Nernstian characteristics in Pb(NO.sub.3).sub.2 solution within the concentration range of 1.0x10.sup.-71.0x10.sup.-3 M, and the detection limit is 4.3x10.sup.-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 Pb.sup.2+-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.