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This study involved the preparation of an all-solid-state ion-selective electrode (ASS-ISE) with copper and a poly(3,4-ethylenedioxythiophene) and polystyrene sulfonate (PEDOT/PSS) conversion layer through electrode deposition. The morphology of the PEDOT/PSS film was characterized, and the performance of the copper ion-selective film was optimized. Additionally, a microfluidic chip for the ASS-ISE with copper was designed and prepared. An integrated microfluidic chip test system with an ASS-ISE was developed using a self-constructed potential detection device. The accuracy of the system was validated through comparison testing with atomic absorption spectrophotometry (AAS). The experimental findings indicate that the relative standard deviation (RSD) of the integrated ASS-ISE with the copper microfluidic chip test system is 4.54%, as compared to the industry standard method. This value complies with the stipulated requirement of an RSD ≤ 5% in DL/T 955-2016. [ABSTRACT FROM AUTHOR]

Amino acids such as phenylalanine (Phe) are key building blocks of proteins and other biomolecules. Although recent advancements in electrochemical sensors have enabled the rapid detection of Phe, these sensors are often destructive as they irreversibly oxidise Phe. In addition, most of them rely on biorecognition elements, which suffer from limited stability at ambient conditions and sensitivity towards environmental fluctuations. Herein, we report the first example of ion transfer voltammetry of Phe using an all‐solid‐state ion‐selective electrode (ISE). The reversibility of this technique enables both the sensor and the Phe sample to be reused. The optimal voltammetric ISE (VISE) exhibits near Nernstian response (56.8 mV/decade) towards Phe and selectivity against amino acids of all classes (hydrophobic, hydrophilic and charged). Voltammetric interrogation of the ISE significantly enhances sensitivity, linear range, selectivity, and stability as compared to traditional open circuit potential measurements. Phe levels in a commercial nutritional supplement and drinking waters were determined to demonstrate the viability of our sensor in real life applications. This proof‐of‐concept can be applied to develop VISEs for other amino acids and biological ions for healthcare and nutrition sensing. [ABSTRACT FROM AUTHOR]

A novel freestanding all-solid-state polymeric membrane Cu2+-selective electrode (Cu2+-ISE) is proposed based on three-dimensional graphene sponge (3D GS). The 3D GS electrode has been characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and contact angle measurements. Experiments show that 3D GS possesses a large electrical double layer capacitance, good conductivity, and high hydrophobicity. Based on these superior properties, 3D GS has been applied as both electrode substrate and solid contact for construction of a freestanding all-solid-state polymeric membrane Cu2+-ISE. The 3D GS-based Cu2+-ISE shows a good Nernstian response ranging from 1.0 × 10−8 to 7.9 × 10−4 M with a low detection limit of 2.5 × 10−9 M. Moreover, the proposed Cu2+-ISE exhibits a stable potential response with a reduced water layer at the sensing membrane/3D GS interface and is not affected by interferences from light, O 2 and CO 2. A freestanding all-solid-state polymeric membrane Cu2+ -selective electrode based on three-dimensional graphene sponge was fabricated. Image 1 • A freestanding all-solid-state polymeric membrane Cu2+-ISE based on three-dimensional graphene sponge (3D GS) is developed. • The 3D GS can be used as both electrode substrate and solid contact for construction of Cu2+-ISE. • The electrode shows a stable potential response with a LOD of 2.5 × 10−9 M. [ABSTRACT FROM AUTHOR]

Nowadays the development of stable and highly efficient Solid-Contact Ion-Selective Electrodes (SC-ISEs) attracts much attention in the research community because of the great expansion of portable analytical devices. In this work, we present highly stable Li + all-solid-state ISEs exploiting noble metals nanostructures as ion-to-electron transducers. The detection of lithium is essential for therapeutic drug monitoring of bipolar patients. In addition, greater environmental exposure to this ion is occurring due to the large diffusion of lithium-ion batteries. However, only a limited number of SC Li + ISEs already exists in literature based on Conductive Polymers (CPs) and carbon nanotubes. The use of noble metals for ion-to-electron transduction offers considerable advantages over CPs and carbon materials, including fast and conformal one-step deposition by electrochemical means, non-toxicity and high stability. We investigate for the first time the use of gold nanocorals obtained by means of a one-step electrodeposition process to improve sensor performance and we compare it to all-solid-state ISEs based on electrodeposited platinum nanoflowers. In addition, the effect of substrate electrode material, membrane thickness and conditioning concentration on the potentiometric response is carefully analysed. Scanning Electron Microscopy (SEM) and Current Reversal Chronopotentiometry (CRC) techniques are used to characterize the morphology and the electrochemical behaviour of the different ISEs. The use of nanostructured gold and platinum contacts allows the increase of the SC capacitance by one or two orders of magnitude, respectively, with respect to the flat metal, while the SC resistance is significantly reduced. We show that the microfabricated sensors offer Nernstian behaviour (58.7 ± 0.8 mV/decade) in the activity range from 10 − 5 to 0.1 M, with short response time ( ∼ 15 s) and small potential drift during CRC measurements ( d E d t = 3 × 10 − 5 ± 2 × 10 − 5 V/s). The exceptional response stability is verified also when no potential is applied. The sensor shows high selectivity towards all clinically important ions, with values very similar to conventional ISEs. Furthermore, to our knowledge, the selectivity towards Ca +2 is the best ever reported for SC-ISEs. In conclusion, the present study opens up new interesting perspectives towards the development of simple and reproducible fabrication protocols to obtain high-quality and high-stability all-solid-state ISEs. [ABSTRACT FROM AUTHOR]

An aqueous dispersion of poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS) was cast on screen-printed gold substrates. PEDOT(PSS) was ionically (physically) crosslinked by multivalent cations, including Mg2+, Ca2+, Fe2+/3+ and Ru(NH3)62+/3+ to form a hydrogel in order to decrease the water solubility of the PEDOT(PSS). The resulting Au/PEDOT(PSS) electrodes were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and energy-dispersive X-ray analysis (EDXA). Ionic crosslinking of PEDOT(PSS) with Fe2+/3+ and Ru(NH3)62+/3+ was faster than with Mg2+ and Ca2+ ions and resulted in PEDOT(PSS) films that were less soluble in water. Among the multivalent cations tested, Ru(NH3)62+/3+ resulted in PEDOT(PSS) films with the most stable potential. Incorporation of Ru into PEDOT(PSS) was shown by EDXA. Based on CV and EIS, ionic crosslinking of PEDOT(PSS) with the electroactive Ru(NH3)62+/3+ was found to increase the bulk redox capacitance of the PEDOT(PSS) film, compared to ionic crosslinking with electroinactive Mg2+ ions. Potentiometric measurements showed that PEDOT(PSS) ionically crosslinked with Ru(NH3)62+/3+ was less sensitive to CO2 (pH) than the bare Au substrate. The Au/PEDOT(PSS) electrodes were found to work well as ion-to-electron transducer (solid contact) in all-solid-state K+-ion-selective electrodes (ISEs). [Copyright &y& Elsevier]

The electrochemical stability of poly(3,4-ethylenedioxythiophene) (PEDOT) is studied in view of its use as ion-to-electron transducer (solid contact) in all-solid-state ion-selective electrodes (ISEs). PEDOT is electrochemically deposited on glassy carbon (GC) and the resulting GC/PEDOT electrodes are studied by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potentiometry. Valinomycin-based all-solid-state K+-ISEs are constructed by placing a K+-selective poly(vinyl chloride) (PVC)-based membrane on the GC/PEDOT electrode (solid contact). The influence of dissolved O2 and CO2 on the potential of the GC/PEDOT electrodes and of all-solid-state K+-ISEs is studied. PEDOT is compared with polypyrrole (PPy) as the solid contact material. A significant difference between the two conducting polymers (CPs) is that PEDOT is less sensitive to O2 and CO2 (pH) than PPy. Therefore, PEDOT is a promising new candidate as ion-to-electron transducer (solid contact) in all-solid-state ISEs based on solvent polymeric membranes that are permeable to O2 and CO2. [Copyright &y& Elsevier]