Poly Vinylalcohol Bearing Styrylpyridinium Groups Research Articles

Anti-freezing, tough, and stretchable ionic conductive hydrogel with multi-crosslinked double-network for a flexible strain sensor

Ionic conductive hydrogels are an ideal material for use in flexible strain sensors due to their electrical conductivity, accurate data retrieval, and extensibility. However, conventional ionic conductive hydrogels including salt/organics or salt-based hydrogels with high ionic content exhibit modest antifreeze and limited mechanical properties, hampering their practical use across diverse sectors. The preparation process is tedious due to the incorporation of toxic photoinitiator and chemical crosslinking agents. Herein, through a simple, low-cost, and environmentally friendly strategy, we have developed a multi-crosslinked double network ionic conductive hydrogel by using polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ) and sodium alginate (SA) via UV irradiation, followed by immersion in a mixed solution of ferric chloride (FeCl3) and glycerol (Gly)/water. This synergistic effect of FeCl3 and Gly has endowed the PVA-SbQ/SA/FeCl3/Gly hydrogel with exceptional mechanical properties (tensile strength of 2.48 ± 0.45 MPa and elongation at break of 1452 ± 101 %), anti-freezing ability (-42.3 °C), and electrical conductivity of 0.38 S/m and 0.32 S/m at room temperature and −30 °C, respectively. Moreover, the hydrogel exhibits remarkable strain sensitivity (GF = 2.49), allowing it to be used as a strain sensor under both room temperature and subzero conditions. Consequently, the prepared hydrogel sensor can monitor various human motions, such as joint bending, running, and speaking. Therefore, our work offers a promising strategy for the preparation of PVA-based hydrogels with outstanding mechanical properties, electrical conductivity, and resistance to freezing, rendering them a practical option for flexible sensors. In addition, our anti-freezing method has significant potential in enhancing the accessibility of ionic conductive hydrogels.

Effects of Tin Oxide Sputtered on a Carbon Electrode for Fabricating Glucose Biosensor

Tin oxide thin films are sputtered onto a commercial carbon electrode to develop a electrode. A mediator (ferrocene carboxylic acid) and an enzyme (glucose oxidase) are coimmobilized by polyvinylalcohol bearing styrylpyridinium groups on the surface of the carbon and electrodes, to fabricate carbon and amperometric glucose biosensors. Following electrode modification, the applied potential is reduced from and the current response increases from as the carbon and amperometric glucose biosensors are immersed in glucose solution. The detection limit of the carbon amperometric glucose biosensor is under an applied potential of . Furthermore, when the applied potential is set to , the detection limit of the amperometric glucose biosensor reaches . No significant interference is observed when the applied potential is set at . Furthermore, the glucose concentration determined by the glucose presence in the serum sample agrees closely with that in the buffer solution. The merits of reducing the applied potential and increasing current response enable a highly accurate amperometric glucose biosensor based on a low-cost substrate to be developed in this study.

Sensitive Detection of Organophosphorus Pesticides Using a Needle Type Amperometric Acetylcholinesterase-based Bioelectrode. Thiocholine Electrochemistry and Immobilised Enzyme Inhibition

An acetylcholinesterase (AChE) based amperometric bioelectrode for a selective detection of low concentrations of organophosphorus pesticides has been developed. The amperometric needle type bioelectrode consists of a bare cavity in a PTFE isolated Pt-Ir wire, where the AChE was entrapped into a photopolymerised polymer of polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ). Cyclic voltammetry, performed at Pt and AChE/Pt disk electrodes, confirmed the irreversible, monoelectronic thiocholine oxidation process and showed that a working potential of +0.410 V vs. Ag/AgCl, KCl sat was suitable for a selective and sensitive amperometric detection of thiocholine. The acetylthiocholine detection under enzyme kinetic control was found in the range of 0.01-0.3 U cm −2 of immobilised AChE. The detection limit, calculated for an inhibition ratio of 10%, was found to reach 5 μM for dipterex and 0.4 μM for paraoxon. A kinetic analysis of the AChE-pesticide interaction process using Hanes-Woolf or Lineweaver-Burk linearisations and secondary plots allowed identification of the immobilised enzyme inhibition process as a mixed one (non/uncompetitive) for both dipterex and paraoxon. The deviation from classical Michaelis Menten kinetics induced from the studied pesticides was evaluated using Hill plots.

PFeW 11-doped polymer film modified electrodes and their electrocatalytic activity for H 2O 2 reduction

A study of electrochemical and electrocatalytic properties, toward H 2O 2 reduction, of the [PFeW 11O 39] −4 polyoxoanion in solution as well as immobilized in partially oxidized polypyrrole (pPy) and in polyvinyl alcohol bearing styrylpyridinium groups (PVA) films is reported. Using cyclic voltammetry at different pH values and scanning rates it was observed that: (i) the two bielectronic waves corresponding to the tungstate-oxo cage are pH-dependent; (ii) the Fe center of the polyoxoanion has an excellent electrocatalytic effect on H 2O 2 reduction, giving a catalytic efficiency and an electrode sensitivity, both higher when dissolved than when immobilized onto electrode surface; and (iii) the one-step method used to obtain the pPy-doped film assures a greater amount of immobilized polyoxoanion than the ionic-exchange method used for PVA films. From rotating-disk electrode (RDE) measurements, the polyoxoanion diffusion coefficient was estimated at 4.1×10 −6 cm 2 s −1, which agrees to that obtained by cyclic voltammetry, 3.9×10 −6 cm 2 s −1, and the heterogeneous rate constant was found to vary between 3.5×10 −3 and 1.9×10 −3 cm s −1 at a variation of the electrode potential from 30 to −30 mV vs. SCE. The best amperometric response observed for the PFeW 11-doped pPy membrane, showed a linear response to H 2O 2 additions up to 9 mM and a sensitivity of 4.8 mA M −1 H 2O 2 in the first day of utilization.

Entrapment of chloroplasts and thylakoids in polyvinylalcohol-SbQ. Optimization of membrane preparation and storage conditions

Chloroplasts and thylakoids isolated from spinach were entrapped in six different polyvinylalcohol bearing styrylpyridinium groups (PVA-SbQ). Measurements of oxygen production were carried out in 0.01 M phosphate buffer (pH 6) at 25 °C. Immobilized preparations were compared for their electron transport activity measured as the initial rate of oxygen evolution with p-benzoquinone as artificial electron acceptor. The entrapped chloroplasts in PVA-SbQ 1700 and 3500 betaine retained 20% of their initial activity after 90-day storage in the dark at + 4 °C. A membrane made with PVA-SbQ 2300 kept 20% activity after 427-day storage at −18 °C in the dark whereas the same membrane retained only 10% activity after 90-day storage at + 4 °C in the dark. A 1% BSA concentration increased the stability of the membrane. The limits of detection (corresponding to a 10% inhibition) of atrazine were 10 μg/l and 12 μg/l for native and entrapped chloroplasts, respectively. The good stability of entrapped chloroplasts suggests that this system could be useful for the detection of pollutants in water.

Immobilization of thylakoids in polyvinylalcohol for the detection of herbicides

Thylakoid membranes isolated from spinach leaves were immobilized by entrapment in polyvinylalcohol bearing styrylpyridinium groups. The reduced species produced by photosynthetic membranes are oxidized at a platinum working electrode in a microphotoelectrochemical cell. Free and entrapped thylakoids were compared for their responses to inhibition by two herbicides: diuron and atrazine. The detection limits were respectively 2×10 −8 and 2×10 −7 M for diuron and atrazine.

Stabilization of Chloroplasts by Entrapment in Polyvinylalcohol Bearing Styrylpyridinium Groups

Abstract Chloroplasts isolated from spinach were immobilized by entrapment in polyvinyl alcohol bearing styrylpyridinium groups (PVA-SbQ). The best conditions of oxygen production (temperature, pH) were optimized and compared with native chloroplasts. The storage stability in a dry state was good. The results achieved with diuron could allow the use of entrapped chloroplasts to elaborate a method for the detection of pollutants inhibiting the photosynthetic electron flow.