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Polymeric membrane ion-selective electrodes (ISEs) have been widely used in environmental monitoring. However, in complicated marine environments, marine biofouling usually becomes a sticky problem for these electrodes. Herein, for the first time, a novel maintenance-free antifouling potentiometric marine sensor based on a self-polishing coating (SPC) is proposed. The SPC is synthesized by using the seeded emulsion polymerization method based on the triisopropylsilyl methacrylate monomer as the regulator of the self-renewal rate. This coating can be simply modified onto the electrode surface by drop-casting. The silyl acrylate side groups of the obtained SPC on the sensor surface can be hydrolyzed in the marine alkaline medium. The shear movement of seawater driven by sea waves, wind, gravity, or vibration removes the leftover (fouled) brittle polymer backbone and thus the fouling marine microorganisms. As a proof-of-concept experiment, a polymeric membrane Ca2+-ISE is chosen as a model. Compared to the unmodified electrode, the SPC-coated Ca2+-ISE exhibits remarkable improved antifouling properties in terms of superior anti-adhesive abilities towards marine microorganisms, such as bacterial cells and algae and excellent long-term stability even in the presence of high levels of marine microorganisms. Since no additional manual maintenance is required for maintaining the antifouling abilities of the sensor, the proposed self-polishing sensor may lay an important foundation for construction of unattended long-term potentiometric monitoring systems in real marine environments. [ABSTRACT FROM AUTHOR]

Carrier-based polymeric membrane potentiometric sensors are an ideal tool for detecting ionic species. However, in the fabrication of these sensors, the screening of carriers still relies on empirical trial- and error-based optimization, which requires tedious and time-consuming experimental verification. In this work, computer-aided screening of carriers is applied in the preparation of polymeric membrane potentiometric sensors. Molecular docking is used to study the host–guest interactions between receptors and targets. Binding energies are employed as the standard to screen the appropriate carrier. As a proof-of-concept experiment, the antibiotic ciprofloxacin is selected as the target model. A series of supramolecular macrocyclic receptors including cyclodextrins, cucurbiturils and calixarenes are chosen as potential receptors. The proposed sensor based on the receptor calix[4]arene screened by molecular docking shows a lower detection limit of 0.5 μmol L−1 for ciprofloxacin. It can be expected that the proposed computer-aided screening technique of carriers can provide a simple but highly efficient method for the fabrication of carrier-based electrochemical and optical sensors. [ABSTRACT FROM AUTHOR]

In this work, a potentiometric polyion sensing strategy based on the surface layer-enhanced transmembrane ion transfer is demonstrated. A polydopamine (PDA) nanolayer with negative charges is modified onto the surface of the polycation-sensitive electrode membrane and used to increase the ion fluxes from the sample phase to the membrane phase. Such modification can significantly improve the detection sensitivity of potentiometric polyion sensors through electrostatic interactions between the cationic targets and anionic PDA groups, which can effectively promote the accumulation of the targets in the boundary layer of the organic membrane phase. By using a thin membrane protamine-sensitive electrode as a model, the detection sensitivity of the PDA-coated electrode (55 mV/μg·mL−1) is nearly five times higher than that of the unmodified electrode (12 mV/μg·mL−1). Moreover, the proposed surface PDA-modified polyion sensor can also be utilized as a general tool for sensitive detection of other polycationic targets and polyanionic species (e.g., the new cancer biomarker cell-free DNA). The proposed potentiometric sensing platform based on surface enhancement of ion transfer offers great potential for sensitive detection of various polyionic targets. [Display omitted] • A surface PDA nanolayer is used to enhance the transmembrane ion transfer of potentiometric polyion sensors. • Such modification can significantly improve detection sensitivity of polycation-sensitive electrodes. • The detection sensitivity of the PDA-coated electrode is nearly five times higher than that of the unmodified one. • Beyond protamine, the proposed sensor can be utilized as a general tool for sensitive detection of other polyions. • The concept may pave the way to using PSEs for sensitive detection of a variety of polyionic biological targets. [ABSTRACT FROM AUTHOR]

In this work, we describe a novel method to improve the detection limits of the non-classical polymeric membrane ion-selective electrodes (ISEs) which are conditioned with highly discriminated ions instead of primary ions. It is based on a thin-layer ISE membrane with a thickness of 5 μm, which is coated on ordered mesoporous carbon used as solid contact. The diffusion of the primary ion from the surface of the sensing membrane to the bulk of the membrane could be avoided by the proposed thin membrane configuration. Since the detection sensitivity of the non-classical ISEs depends on the accumulation of the primary ion in the interfacial layer of the sensing membrane, a lower detection limit can be obtained. By using the copper ion as a model, the present potentiometric sensor shows a significantly improved detection sensitivity compared to the conventional ISE with a membrane thickness of ca. 200 μm. Low detection limits of 0.29 and 0.53 nM can be obtained in 0.01 and 0.5 M NaCl, respectively. In addition, the proposed sensor exhibits an excellent reversibility by using a neutral proton-selective ionophore incorporated in the thin membrane. For the first time, a thin membrane configuration based on non-equilibrium mechanism is used to improve the detection limit of the non-classical ISEs. Image 1 • A novel thin polymeric membrane potentiometric sensor is developed. • The thin membrane configuration is used to improve the detection limit of the non-classical potentiometric sensor. • The proposed sensor shows a significantly improved detection sensitivity compared to the conventional ISEs. • The thin membrane-based concept can be extended to improve sensing performance of other polymeric membrane ISEs. [ABSTRACT FROM AUTHOR]

Molecularly imprinted polymer (MIP)-based polymeric membrane potentiometric sensors are ideal candidates for detection of organic species. The development of such sensors has opened new attractive horizons for potentiometric sensing. However, it should be noted that in the preparation of these MIP receptors, the selection of the functional monomer usually depends on empirical trial- and error-based optimization, which involves tedious and time-consuming experiments. In this work, the computer-aided design and synthesis of an MIP receptor are applied in the fabrication of an MIP-based potentiometric sensor. The density functional theory calculation with the B3LYP model and 6-31G(d) basis set is used to study the interactions between the functional monomer and template molecules. The binding energies of the complexations between the template molecule and different functional monomers are used as a criterion for the selection of the proper monomer. The designed MIP is then synthesized and employed as the receptor for the fabrication of the potentiometric sensor. As a proof-of-concept experiment, the antibiotic sulfadiazine has been selected as a model and 4 functional monomers, 2-hydroxyethyl methacrylate, methyl methacrylate, N-isopropylacrylamide and N-phenylacrylamide, have been chosen. The designed MIP-based sensor exhibits excellent sensitivity with a linear range of 1–10 μM and also shows a good selectivity. We believe that the proposed computer-aided synthesis technique for the MIP receptor selection can provide a general and facile way to replace the traditional empirical MIP preparation method in the fabrication of MIP-based electrochemical and optical sensors. Computer-aided design and synthesis of an MIP receptor are applied in the fabrication of an MIP-based potentiometric sensor for detection of antibiotic for the first time. [Display omitted] • Solid-contact potentiometric sensor using computationally designed MIP is proposed. • Density functional theory calculation is used to explore the interactions. • The monomer 2-hydroxyethyl methacrylate shows the lowest binding energy. • The developed MIP-based potentiometric sensor exhibits excellent performance. • The method is generally applicable to MIP-based electrochemical and optical sensors. [ABSTRACT FROM AUTHOR]

Polymeric membrane ion-selective electrodes (ISEs) have been widely used in various fields including clinical diagnosis, environmental monitoring and industrial analysis. Although most samples of analytical interest measured by the ISEs are aqueous solutions, the applications of these electrodes in nonaqueous media are often inevitable. Unfortunately, so far, little has been known about the extent to which the properties of the ISEs could be affected by the organic solvents. Herein, the feasibility for the applications of the polymeric membrane ISEs in nonaqueous media has been investigated. A polymeric membrane Ca2+-ISE is chosen as a model of potentiometric sensors. Four typical water miscible organic solvents (three protic solvents: ethanol, acetic acid, and methanol, and one aprotic dipolar solvent: acetonitrile) are used as the representative examples. Experiments show that the aprotic solvent acetonitrile has the strongest destructive ability towards the sensing performance of the ISE in terms of Nernstian slope and selectivity coefficient. Moreover, the effect on the sensing performance depends on the kind of the protic solvent, the immersion time and the polarity of the membrane plasticizer. We believe that the obtained results could promote further applications of the polymeric membrane ISEs in the organic solvent-containing samples, which could significantly extend the application scope of the ISEs. [Display omitted] • Feasibility for application of polymeric membrane ISEs in nonaqueous media is tested. • Effect of water-miscible organic solvents on ISE sensing performance is investigated. • Aprotic solvent has a stronger destructive ability towards ISE than protic solvent. • Leaching of the membrane components in organic solution is quantified for the first time. • The present work may lay a foundation for application of ISEs in nonaqueous samples. [ABSTRACT FROM AUTHOR]

Reliable potentiometric ion sensing in complex samples (e.g., biological fluids, wastewater and seawater) remains a great challenge for polymeric membrane ion-selective electrodes (ISEs). As one of the major impediments, electrode fouling which is caused by the undesirable adsorptions of organic molecules and biological cells on the electrode surfaces can seriously impair the analytical performance of ISEs. Development of polymeric membranes with fouling resistance is a fundamental strategy to deal with this ubiquitous problem. To date, it has become an important research direction for applications of polymeric membrane ISEs. This paper presents an overview on the advances in anti-fouling ISEs. The major foulants for polymeric membrane ISEs and the fouling influences on the sensors' performance are described. The anti-fouling strategies, preparation methods and future prospects for antifouling ISEs are discussed. • An overview on the advances in anti-fouling polymeric membrane ion-selective electrodes is presented. • Major foulants and their influences on polymeric membrane ion-selective electrodes are summarized. • Anti-fouling strategies of polymeric membrane ion-selective electrodes are discussed. • Preparation methods of anti-fouling polymeric membrane ion-selective electrodes are summarized. • Future directions in development of anti-fouling polymeric membrane ion-selective electrodes are provided. [ABSTRACT FROM AUTHOR]

Highlights: [•] We report a novel potentiometric sensor based on molecularly imprinted nanoparticles. [•] Imprinted nanoparticles are used for the polymeric membrane ISE. [•] An asymmetric membrane rotating ISE is applied to improve the detection sensitivity. [•] The new method offers a low detection limit of 1.9×10−9 molL−1 for triclosan. [ABSTRACT FROM AUTHOR]

Carrier-based polymeric membrane potentiometric sensors have been widely used for determination of inorganic ions in clinical and environmental applications. In view of the need for a wider application scope of these sensors, the list of targets needs to be increased. Molecularly imprinted polymer (MIP)-based potentiometric sensors are ideal candidates for sensing of organic and biological species. The development of such sensors may open attractive horizons for potentiometric sensing and further expand the field. The past few decades have witnessed remarkable achievements in these sensors. This review summarizes recent advances in the MIP synthesis, the detection modes of these sensors and their applications for organic and biological species in environmental and biological analyses, and attempts to illustrate the research directions. We hope that this review will shed new light on the understanding of MIP-based potentiometric sensors and pave the way for the widespread applications of polymeric membrane potentiometric sensors. • Advances and future directions in MIP-based potentiometric sensors are presented. • MIP synthesis method, detection mode and application of such sensors are discussed. • MIP-based sensing strategies are generally applicable for chemical sensing. • Our review may promote the development of polymeric membrane potentiometric sensors. • This review will appeal to a broad variety of chemical communities. [ABSTRACT FROM AUTHOR]

• Ag NPs are modified onto the ISE membrane surface for the first time to improve anti-biofouling properties. • Ag NPs can be in situ formed on the membrane surface through the selfpolymerization of dopamine. • The bifunctional material-based sensor exhibits excellent anti-bacterial activity (93.3 %) and anti-adhesion abilities. • The concept could be extended to improve the anti-fouling properties of other polymeric membrane-based electrochemical sensors. Polymeric membrane ion-selective electrodes (ISEs) have been widely applied in environmental analysis. In many cases of practical relevance, however, when these sensors are applied in complex samples, they could suffer from problems of biofouling (related to microorganisms and biofilms) which may shorten the sensors' lifetimes and cause the measurement errors. Herein, we describe a robust and effective method to endow the ISE membranes with anti-biofouling properties based on surface modification of silver nanoparticles (Ag NPs). The ISE membrane is modified with the hydrophilic polydopamine (PDA) followed by in-situ formation of Ag NPs. The PDA modification enhances anti-adhesive properties of the ISE membrane by increasing the surface hydrophilicity, while Ag NPs impart strong anti-microbial properties to the membrane. A classical polymeric membrane K+-ISE has been chosen as a model. Compared to the unmodified K+-ISE, the Ag NPs modified K+-ISE exhibits significantly improved anti-biofouling properties in terms of the low viability and adhesion rates of bacteria while retaining its original potentiometric ion response properties. Moreover, Ag NPs on the sensor surface show an excellent long-term stability. We believe that the proposed approach can be extended to improve the anti-fouling abilities of other polymeric membrane-based electrochemical sensors for detection in complex environmental samples. [ABSTRACT FROM AUTHOR]

Polymeric membrane potentiometric sensors based on molecularly imprinted polymers (MIPs) as the receptors have been successfully developed for detection of organic and biological species. However, it should be noted that all of the polymeric membrane matrices of these sensors developed so far are the plasticized poly(vinyl chloride) (PVC) membranes, which are usually suffered from undesired plasticizer leaching. Hence, for the first time, we describe a novel plasticizer-free MIP-based potentiometric sensor. A new copolymer, methyl methacrylate and 2-ethylhexyl acrylate (MMA-2-EHA), is synthesized and used as the sensing membrane matrix. By using neutral bisphenol A (BPA) as a model, the proposed plasticizer-free MIP sensor shows an excellent sensitivity and a good selectivity with a detection limit of 32 nM. Additionally, the proposed MMA-2-EHA-based MIP membrane exhibits lower cytotoxicity, higher hydrophobicity and better MIP dispersion ability compared to the classical plasticized PVC-based MIP sensing membrane. We believed that the new copolymer membrane-based MIP sensor can provide an appealing substitute for the traditional PVC membrane sensor in the development of polymeric membrane-based electrochemical and optical MIP sensors. For the first time, a novel plasticizer-free MIP-based potentiometric sensor is described. Image 1 • A novel plasticizer-free MIP-based potentiometric sensor is developed. • A new copolymer, MMA-2-EHA, is synthesized and used as the sensing membrane matrix. • The proposed MIP sensor shows an excellent sensitivity and a good selectivity. • The proposed sensor exhibits obvious advantages in cytotoxicity and hydrophobicity. • The copolymer membrane-based strategy is generally applicable for chemical sensors. [ABSTRACT FROM AUTHOR]