Development of an amperometric biosensor based on a redox‐mediator‐doped polypyrrole film

An amperometric biosensor was developed for the quantitative estimation of phenolic compounds in aqueous media. The enzyme tyrosinase [poly(phenol oxidase) (PPO)] was adsorbed onto a hexacyanoferrate(II)‐ion‐doped conducting polypyrrole (PPY) film deposited on an indium tin oxide (ITO) coated glass‐plate support. The PPO activity in the PPO/Fe²⁺‐PPY/ITO film was assayed as a function of the concentration of phenolic compounds. Cyclic voltammetric studies were carried out on this enzyme electrode, and the surface morphology of the enzyme‐immobilized polymer film was studied with scanning electron microscopy. The results of the amperometric response of the PPO/Fe²⁺‐PPY/ITO film showed sensitivities of 0.14, 0.21, and 0.36 A M^?1cm^?2 and linear response ranges of 9.9–84.7, 6.7–72.6, and 3.9–48.8 μM for phenol, catechol, and p‐chlorophenol, respectively. The PPO/Fe²⁺‐PPY/ITO electrode exhibited a response time of about 50 s and was stable for about 12 weeks at 4°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 927–933, 2004     

Application of conducting poly(aniline‐co‐pyrrole) film to cholesterol biosensor

Cholesterol oxidase (ChOx) has been covalently immobilized onto poly(aniline‐co‐pyrrole), electrochemically deposited onto indium‐tin‐oxide (ITO) glass plates, using glutaraldehyde as a crosslinker. These poly (An‐co‐Py)/ChOx films have been characterized using UV–visible spectroscopy fourier transform infrared spectroscopy, scanning electron microscopy, and photometric and amperometric techniques, respectively. The poly(An‐co‐Py)/ChOx bioelectrodes have been utilized for cholesterol estimation in the range of 1–10 mM. The ChOx activity in poly(An‐co‐Py)/ChOx bioelectrode has been found to be the highest at pH 7.0 at 25°C. The sensitivity and stability of poly(An‐co‐Py)/ChOx bioelectrode have been experimentally determined as 93.35 μA/mM and 10 weeks at 4°C, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Cholesterol biosensor based on electrochemically prepared polyaniline conducting polymer film in presence of a nonionic surfactant

Cholesterol biosensor has been fabricated by covalently coupling cholesterol oxidase (ChOx) via glutaraldehyde onto electrochemically prepared polyaniline film in presence of TritonX-100 [4-(1,1,3,3-tetramethylbutyl) phenyl polyethylene glycol], a non-ionic surfactant onto indium-tin-oxide (ITO) glass substrate. These ChOx/PANI-TX-100/ITO bioelectrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV) and scanning electron microscopy (SEM) techniques. The results of response measurements carried out on ChOx/PANI-TX-100/ITO bioelectrodes using amperometric and photometric techniques, reveal detection limit as 5 mg/dl, linearity from 5 to 400 mg/dl of cholesterol and sensitivity as 131 μA/(mg/dl cm⁻²). These biosensing electrodes are thermally stable up to 65 °C, can be used about 20 times and have a shelf-life of about 10 weeks when stored at 4 °C. Attempts have also been made to utilize the ChOx/PANI-TX-100/ITO bioelectrodes for estimation of free cholesterol concentration in serum samples.     

Preparation and characterization of an enzyme electrode based on cholesterol esterase and cholesterol oxidase immobilized onto conducting polypyrrole films

Cholesterol esterase (ChEt) and cholesterol oxidase (ChOx) enzymes were entrapped within polypyrrole (PPy) films on a platinum disc electrode during electrochemical polymerization. The characteristics of the PPy/ChEt/ChOx enzyme electrode thus prepared were investigated as a function of the time, pH, temperature, and concentration of cholesteryl palmitate by a spectrophotometric method. PPy/ChEt/ChOx electrodes can be used for the estimation of cholesteryl palmitate concentrations from 1 to 8 mM, can be used least 10 times, and have a shelf life of about 1 month at 4–10°C. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3769–3773, 2004     

Construction of a choline biosensor through enzyme immobilization on a poly(2‐hydroxyethyl methacrylate)‐grafted Teflon film

An amperometric choline biosensor was constructed by immobilizing choline oxidase (ChO) on poly(2‐hydroxyethyl methacrylate) (PHEMA)‐grafted Teflon (polytetrafluoroethylene, PTFE) film. Grafting was achieved by γ irradiation. PHEMA‐grafted Teflon films were activated with epichlorohydrin or glutaraldehyde to achieve covalent immobilization of enzyme onto the film. To decrease the diffusional barrier caused by the enzyme‐immobilized film, the film was stretched directly on the electrode. The PHEMA‐grafted Teflon film, therefore, had to have appropriate mechanical properties. Glucose oxidase (GOD) was used in the determination of optimum immobilization conditions, then these were applied to ChO. With GOD, the effect of activation type and film position in electrode on enzyme activity was studied and the highest catalytic activity was obtained when the enzyme was immobilized using glutaraldehyde and the film was stretched over the electrode surface. Further studies revealed that the films activated with glutaraldehyde, immobilized in 2 mg/mL ChO concentration, and stretched directly on the electrode were suitable (specific activity, 0.427 ± 0.068 U mg^?1) for use in the choline biosensor. The linear working range of this biosensor was found to be 52–348 μM, with a 40 ± 5 μM minimum detection limit. The response of the sensor, however, decreased linearly upon repeated use. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Fourier transform infrared study of polypyrrole–poly(vinyl alcohol) conducting polymer composite films: Evidence of film formation and characterization

The electrochemical preparation of polypyrrole (PPY)–poly(vinyl alcohol) (PVA) conducting polymer composite films on an indium–tin oxide glass electrode from an aqueous solution containing a pyrrole monomer, a p‐toluene sulfonate electrolyte, and a PVA insulating polymer is reported. The prepared PPY–PVA composite films were characterized by Fourier Transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and conductivity measurements. The FTIR study showed that the composite of PPY and PVA formed through bond formation between PVA and the p‐toluene sulfonate dopant anion. The conductivity data of PPY–PVA showed that with increasing PVA concentration in the pyrrole solution, the conductivity of the prepared PPY–PVA film increased up to a certain level due to an increase in conjugation length, and later, it decreased with further increases in the PVA concentration in the solution due to a decrease in conjugation length. This was supported by the FTIR band intensity I₁₅₆₀/I₁₄₈₀. The TGA results show that the PPY–PVA polymer composite film was thermally more stable than the PPY film. A shielding effectiveness of 45.6 dB was exhibited by the PPY–PVA composite film in the microwave frequency range. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4107–4113, 2006     

Development of a POA/DBS/GOx Biosensor for the Determination of Glucose

In the present work, a simple technique is described for constructing a poly(o-anisidine) (POA)-dodecylbenzene sulphonic acid (DBS)-glucose oxidase (GOx) (POA-DBS-GOx) electrode. The enzyme glucose oxidase (GOx) was immobilized by crosslinking via glutaraldehyde on the POA-DBS film. The POA-DBS films were synthesized electrochemically on platinum substrate. The synthesized films were characterized by using electrochemical technique, conductivity measurement, UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The conductivity of the polymer films was found to be about 7.61 × 10^?2 S/cm. The crosslinking of enzyme and the porous morphology of the polymer film lead to good stability and good response time of the enzyme electrode. The stability and lifetime of the POA-DBS-GOx electrode have been studied. It shows very good stability and response for 3–4 weeks at 4°C. The results of this study reveal that a phosphate buffer gives better response than acetate buffer in amperometric measurements.     

Dielectric spectroscopic studies on polypyrrole glucose oxidase films

An investigation was made into the dielectric spectroscopic characteristics of p-toluene sulfonate (PTS) doped polypyrrole (PPY) films in the presence and absence of immobilized glucose oxidase (GOX) in three different configurations: Al-PTS-PPY-Al-PTS-PPY/GOX-Al, and Al-PTS-PPY/GOX/β-D -glucose-Al, respectively. Measurement of dielectric loss and capacitance yielded valuable information about the dielectric properties of GOX immobilized in PTS doped PPY films. The effect of both the temperature and varying βD -glucose concentrations on the mobility of the charge carriers in these films was also systematically studied. © 1996 John Wiley & Sons, Inc.     

Lamination of conductive polypyrrole films to poly(tetrafluoroethylene) films via interfacial graft copolymerization

A simple technique for the lamination of a conductive polymer film to an inert dielectric polymer film was demonstrated. The electrochemically synthesized and p‐toluenesulfonic acid‐doped polypyrrole (PPY) film was laminated simultaneously to the argon plasma‐pretreated PTFE film during the thermally induced graft copolymerization of the PTFE surface with a functional monomer. The graft copolymerization was carried out using glycidyl methacrylate (GMA) monomer containing 20% v/v hexamethyldiamine (HMDA) and in the absence of any polymerization initiator. Thermally induced graft copolymerization of the GMA monomer on the PPY surface was minimal. The lap shear and T‐peel adhesion strengths of the laminates were found to be dependent on the GMA graft concentration on the PTFE surface, which, in turn, was affected by the plasma pretreatment time of the film. To increase the GMA graft concentration for the enhancement of adhesion strength, the plasma‐pretreated PTFE surfaces were premodified via UV‐induced graft copolymerization with GMA prior to the simultaneous thermal graft copolymerization and lamination process. The modified surfaces and interfaces were characterized by X‐ray photoelectron spectroscopy (XPS). Through XPS measurements of the delaminated surfaces, it was found that the PPY/PTFE laminates failed predominantly by cohesive failure inside the PTFE substrate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 716–727, 2001     

Nanostructured manganese oxide–chitosan-based cholesterol sensor

Manganese oxide nano-rod (nano-MnO₂) was prepared by simple oxidation method. To fabricate nanocomposite film (nano-MnO₂/CT) onto glassy carbon electrode (GCE), nano-MnO₂ was homogeneously dispersed in chitosan (CT). Cholesterol oxidase (ChOx) was immobilized onto nano-MnO₂/CT by physisorption. Modified electrode was characterized by Fourier transform infrared, X-ray diffraction, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrochemical impedance spectroscopy techniques. Prepared ChOx/nano-MnO₂/CT/GCE bioelectrode exhibited 0.03–11.66 mM linearity and 2.07 × 10^?3 mM limit of detection for cholesterol. Biosensing characteristics of modified bioelectrode were superior than other electrodes modified with metal oxide nanoparticles, reported in the literature.     

有机溶剂热生长技术制备硫族化合物及其光学特性的研究

以有机溶剂热生长技术(solvothermaltechnique)制备了半导体硫族化合物(CdS、ZnS、MoS2)等纳米颗粒,采用XRD、TEM等技术对其结构进行表征.以ITO导电玻璃以及导电聚合物(PANI、PPY)膜为基底,将纳米颗粒涂布其上并以PL法研究其光学特性,实验结果表明:经修饰后,材料的荧光发射位置发生显著的变化.     

Preparation of plasma‐polymerized 3‐quinolinecarbonitrile and its photo(electro)‐luminescence properties

A novel plasma‐polymerized 3‐quinolinecarbonitrile (PP3QCN) thin film was prepared by plasma polymerization of 3‐quinolinecarbonitrile (3QCN) for the first time. The PP3QCN thin films show a blue emission with a narrow peak at ～ 475 nm and there appeared a relatively high intensity of PL peak. The EL devices with PP3QCN as electroluminescent layer sandwiched between ITO and Al were fabricated. It was found that the ITO/PP3QCN/Al devices also show a blue emission and PP3QCN thin film was stable and appropriate for the electroluminescent layer. The external quantum efficiency of ITO/PP3QCN/Al devices can reach to 0.0068%. The plasma‐polymerized conjugated polynitrile thin film obtained from 3QCN precursor might be a promising material for application in LED and photodiode device. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characterization and application of immobilized lipase enzyme on different radiation grafted polymeric films: Assessment of the immobilization process using spectroscopic analysis

Lipase has been immobilized onto different films, polypropylene and poly(tetrafluoroethylene‐perfluroro‐propyl vinyl ether) using glutalaradehyde as a crosslinker. Differential scanning calorimetery, Fourier transform infrared spectroscopic, x‐ray diffraction, and scanning electron microscopy measurements were carried out to confirm the structure of the polymer films as well as the immobilization process of the enzyme onto the polymeric carrier. The activity and stability of the resulting biopolymers produced by lipase have been compared to those for the native lipase. The experimental results showed that the optimum temperature and pH were 40°C and 8.0, respectively. The activity of the immobilized lipases varied with lipase concentration and with the yield of grafting. Subjecting the immobilized enzymes to a dose of γ‐radiation of (0.5–10 Mrad) showed complete loss in the activity of the free enzyme at a dose of 5 Mrad. A leakage of the enzyme from the irradiated membranes was not observed in the repeated batch enzyme reactions. The operational stability of the free and immobilized lipase in n‐hexane showed that the immobilized enzyme was much more stable than the free one. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 155–167, 2003     

Immobilization of GOD on Ppy–PVS Composite Film for Determination of Glucose: A Comparative Study of Phosphate and Acetate Buffers

The Polypyrrole-polyvinylsulphonate-glucose oxidase (Ppy–PVS–GOD) biosensor for determination of glucose has been described in the present investigation. The enzyme, glucose oxidase (GOD) was immobilized by crosslinking via glutaraldehyde on a polypyrrole–polyvinyl sulphonate (Ppy–PVS) composite film. The Ppy–PVS film was electrochemically synthesized on indium-tin-oxide (ITO)–coated glass plate. The synthesized composite films were characterized using galvanostatic electrochemical technique, electrical conductivity, UV-Visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The crosslinking of enzyme and porous morphology of the polymer film leads to high enzyme loading and an increase in lifetime, stability, and fast response time of the enzyme electrode. Characterization of resulting amperometric biosensor for the estimation of glucose has been experimentally determined in terms of linear response range, optimum pH, applied potential, and shelf-life. These Ppy–PVS–GOD electrodes can be used for glucose estimation from 1 to 50 mM and have a shelf-life of about 5–6 weeks at 4°C. The sensitivity of Ppy–PVS–GOD electrode in phosphate and acetate buffer has been studied. It was found that the phosphate buffer gives fast response as compared to acetate buffer in amperometric measurements.     

Immobilization of chymotrypsin with interpolymer complexes of P(TM‐co‐AAm)/PAA

Chymotrypsin was immobilized with interpolymer complexes formed by the cationic polymer poly(allyltrimethyl ammonium chloride‐co‐acrylamide) [P(TM‐co‐AAm)] and poly(acrylic acid) (PAA). The introduction of a small amount of cationic groups led to a much stronger polymer–polymer interaction between P(TM‐co‐AAm) and PAA. The characteristic pH sensitivity of this kind of complex provided the possibilities of controlling the activity of the immobilized enzyme and separating the immobilized enzyme from the batch by changing the pH of the medium. Compared with the free enzyme, the immobilized chymotrypsin had higher thermal stability, acid–base stability, and stability in use. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2013–2018, 2001     

Polymerization of pyrrole and processing of the resulting polypyrrole as blends with plasticised PVC

Polypyrrole was synthesized by chemical oxidation of pyrrole in water containing various sulphonic acids like toluene sulphonic acid (TSA), sulphosalicylic acid (SSA), and camphor sulphonic acid (CSA), as well as a combination of each sulphonic acid with sodium dodecyl benzene sulphonate (NaDBS) to investigate the effect of doping on conductivity, yield, and processability of the conducting polymer. Free‐standing blend films of polypyrrole and plasticized polyvinyl chloride (PVC) were obtained by casting an homogeneous suspension of the two polymers in tetrahydrofuran. The maximum conductivity of the blend film is ～ 0.3 S/cm, corresponding to a weight fraction of 0.16 w/w polypyrrole. The blend film is semiconducting in the range 300–10 K. A TG‐DTA scan indicates the blend film to be amorphous with a stepwise decomposition process similar to pristine PVC. The choice of a dual dopant system during synthesis and the plasticised polymer during subsequent processing were keys to obtaining homogeneous high‐quality films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1544–1548, 2001     

Immobilization of glucoamylase on the plain and on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres

Immobilization glucoamylase onto plain and a six‐carbon spacer arm (i.e., hexamethylene diamine, HMDA) attached poly(2‐hydroxyethylmethacrylate‐ethyleneglycol dimethacrylate) [poly(HEMA‐EGDMA] microspheres was studied. The microspheres were prepared by suspension polymerization and the spacer arm was attached covalently by the reaction of carbonyl groups of poly(HEMA‐EGDMA). Glucoamylase was then covalently immobilized either on the plain of microspheres via CNBr activation or on the spacer arm‐attached microspheres via CNBr activation and/or using carbodiimide (CDI) as a coupling agent. Incorporation of the spacer arm resulted an increase in the apparent activity of the immobilized enzyme with respect to enzyme immobilized on the plain of the microspheres. The activity yield of the immobilized glucoamylase on the spacer arm‐attached poly(HEMA‐EGDMA) microspheres was 63% for CDI coupling and 82% for CNBr coupling. This was 44% for the enzyme, which was immobilized on the plain of the unmodified poly(HEMA‐EGDMA) microspheres via CNBr coupling. The K_m values for the immobilized glucoamylase preparations (on the spacer arm‐attached microspheres) via CDI coupling 0.9% dextrin (w/v) and CNBr coupling 0.6% dextrin (w/v) were higher than that of the free enzyme 0.2% dextrin (w/v).The temperature profiles were broader for both immobilized preparations than that of the free enzyme. The operational inactivation rate constants (k_iop) of immobilized enzymes were found to be 1.42 × 10^?5 min^?1 for CNBr coupled and 3.23 × 10^?5 min^?1 for CDI coupled glucoamylase. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2702–2710, 2001     

Retention of activity of urease immobilized on grafted polymer films

Expanded poly(tetrafluoroethylene) (ePTFE) films grafted with 2‐hydroxyethyl methacrylate (HEMA) and 2‐hydroxyethyl acrylate (HEA) were applied to a polymer support for urease immobilization. The HEMA‐ and HEA‐grafted ePTFE (ePTFE‐g‐PHEMA and ePTFE‐g‐PHEA) films prepared by the combined use of the plasma treatment and photografting possessed high water‐absorptivities. Imidazole groups were introduced to grafted PHEMA and PHEA chains with 1,1′‐carbonyldiimidazole (CDI) in acetonitrile. The activity of urease covalently immobilized to the ePTFE‐g‐PHEMA and ePTFE‐g‐PHEA films in a pH 7.0 buffer at 4°C had the maximum value at the optimum pH value of 7.5 for native urease. Urease immobilized on the ePTFE‐g‐PHEMA films with the extent of CDI bonding of about 20% had the maximum activity, and the repeatedly measured activity was kept almost constant. The relative activity of immobilized urease stayed almost constant in the range of the immobilized amounts between 10 and 30 mg/g for both grafted ePTFE films, and decreased at higher immobilized amounts because of the crowding of immobilized urease molecules in the grafted layers. The relative activity of immobilized urease had the maximum values at the grafted amounts of 1.2 and 1.7 mmol/g for the ePTFE‐g‐PHEMA and ePTFE‐g‐PHEA films, respectively, and the further increase in the grafted amount resulted in the decrease in the relative activity. The optimum temperature of the activity for immobilized urease was shifted from 30 to 50°C for native urease by the covalent immobilization on both grafted ePTFE films and immobilized urease was repeatedly usable without a considerable decrease in the activity in the regions of the pH 6.0–9.0 and 10–60°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4886–4896, 2006     

Electrical properties of metal/Langmuir–Blodgett layer/semiconductive devices

Metal–insulator–semiconductor (MIS) structures were fabricated by vacuum deposition of various metals like indium, aluminum, and tin on Langmuir–Blodgett (LB) films of cadmium stearate (CdSt₂) obtained on polypyrrole (PPY) films electrochemically deposited on indium-tin-oxide glass. Junction parameters such as rectification ratio, barrier height, and work function of such devices were experimentally determined. Passivation of semiconducting polypyrrole film is seen to result in a lower value of the ideality factor. For example, measured ideality factors of CdSt₂ LB layer/semiconducting PPY structures are 6.63, 6.57, and 6.54 for various metals like Sn, Al, and In, respectively, in comparison to the values of 8.85, 8.82, and 8.20 obtained with semiconducting PPY interface with same elements. The value of the dielectric constant of the insulating CdSt₂ LB film was calculated as 1.84 and this is in reasonable agreement with the value (2.13) reported earlier. © 1996 John Wiley & Sons, Inc.     

PANI/PPY blend thin films electrodeposited for use in EGFET sensors

Galvanostatic electrodeposited thin films of polyaniline (PANI)/polypyrrole (PPY) blend were tested as chemical sensors and evaluated according to the relative monomer concentration in polymerization solution aiming to obtain a reliable reference field‐effect transistor able to be used as contrast sensing film. The blend material presented properties that can be controlled by the polymerization process. The films were produced using aniline (0.25 M) and pyrrole (0.25 M) mixed in five different proportions (90/10, 70/30, 50/50, 30/70, 10/90) with HCl (1.0 M) in an aqueous solution. The current density was 1 mA/cm² for 300 s. The films were analyzed by their chronopotentiometric curves, thickness, reflectance spectroscopy, optical color parameters, and surface morphology. The characteristics and properties analyzed were correlated to the relative monomer concentration in the polymerization solution. The polymerization of PANI is favorable in aqueous acid solution compared to PPY, which resulted in thin films with properties varying from PANI down to PPY. The blend films presented controllable sensitivity when applied as sensing stage in field‐effect transistor devices as function of the relative monomer concentration. The sensitivity varied from 57 ± 1 mV/pH for the PANI sample, down to 25 ± 1 mV/pH for the PPY sample, presenting an exponential behavior. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46625.