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     

Electropolymerization and ion exchange properties of a polypyrrole film doped by para‐toluene sulfonate

Electropolymerization and ion exchange properties of the polypyrrole film doped by para‐toluene sulfonate (PPy/pTS) were investigated in aqueous solutions. The film with a column‐like surface morphology was galvanostatically synthesized at 3 mA/cm² during 1800 s. Cyclic voltammetric measurements of the PPy/pTS film in sodium para‐toluene sulfonate (NapTS), tetraethylammonium chloride ((C₂H₅)₄NCl), and NaCl aqueous solutions showed a cation exchange property, an anion exchange property, and a combination of them, respectively. Moreover, the large ions could decrease the transport of the small ions coexisting in the same solution, and the redox processes were proved to be electrochemically irreversible and ion transport‐limiting reactions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2518–2522, 2006     

Poly(hydroxyethyl methacrylate‐co‐glycidyl methacrylate) reactive membrane utilised for cholesterol oxidase immobilisation

Poly(2‐hydroxyethyl methacrylate‐co‐glycidyl methacrylate) p(HEMA–GMA) membrane was prepared by UV‐initiated photopolymerisation of 2‐hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) in the presence of an initiator, azobisisobutyronitrile (AIBN). Cholesterol oxidase was immobilised directly on the membrane by forming covalent bonds between its amino groups and the epoxide groups of the membrane. An average of 53 µg of enzyme was immobilised per cm² of membrane, and the bound enzyme retained about 67% of its initial activity. Immobilisation improved the pH stability of the enzyme as well as its temperature stability. The optimum temperature was 5 °C higher than that of the free enzyme and was significantly broader. The thermal inactivation rate constants for free and immobilised preparations at 70 °C were calculated as k_{i (free)} 1.06 × 10^?1 min^?1 and k_{i (imm)} 2.68 × 10^?2 min^?1, respectively. The immobilised enzyme activity was found to be quite stable in the repeated experiments. © 2002 Society of Chemical Industry     

Organic phase PPO biosensor based on hydrophilic films of electropolymerized polypyrrole

We described herein, the construction of an organic phase enzyme electrode (OPEE) via polyphenol oxidase (PPO) entrapment within a hydrophilic polypyrrole film electrogenerated from on a new bispyrrolic derivative (1) containing a long hydrophilic spacer. The so-called “adsorption step procedure” was adopted for the preparation of the organic phase PPO biosensor. The amperometric detection of catechol was carried out in anhydrous chloroform at −0.2 V versus Ag/AgCl. The electroanalytical parameters of the biosensor strongly depend on its configuration and on the hydration state of the enzyme matrix. The best sensitivity obtained for catechol in chloroform was 15.6 mA M⁻¹ cm⁻².     

The actuation behavior and stability of p‐toluene sulfonate doped polypyrrole films formed at different deposition current densities

Free‐standing films of polypyrrole doped with p‐toluene sulfonate (PPy/pTS) were electropolymerized galvanostatically at different deposition current densities and their electrochemomechanical deformation (ECMD) properties were measured in situ during cyclic voltammetry experiments. It was found that films exhibiting a higher cation‐driven actuation strain were generated when a lower current density was used in electropolymerization, which also led to an increase in PPy conductivity and doping level. A decrease in cation‐driven strain with time was observed in all cases due to a loss of pTS anions from the films. Raman, FTIR, and elemental analyses were used to characterize the films grown at different deposition current densities and no sign of excessive overoxidation was found. SEM images revealed that the morphology of the films was affected by the current density during electropolymerization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Immobilization of glucose oxidase and acetylcholinesterase onto modified polyamide sorbent

Two types of polyamide (PA) sorbents with high specific area were prepared. The effects of solvent type, concentrations of formic acid, and polymer on the porosity characteristics were studied. The sorbent with the highest specific area was obtained by using C₂H₅OH—HCOOH solvent (60% HCOOH) and the rest of the experiments were carried out with this type of sorbent. The possibility of applying the PA sorbent as carrier for immobilization of glucose oxidase (GOD) and acetylcholinesterase (AChE) was investigated. In order to increase the active groups content (necessary for enzyme immobilization), the sorbent was modified with dimethylaminoethylmethacrylate (DMAEM) and 2-acrylamido-2-methylpropensulfonic acid. The amount of the active groups introduced during the modification and the degree of hydrophilicity were determined. The quantity of bound protein and relative activity of GOD and AChE immobilized onto unmodified and modified sorbents were studied. Optimum pH and temperature of the immobilized GOD and AChE were also determined. The influence of three phosphoroorganic compounds on the activity of the immobilized AChE was investigated. Tetrachlorvinvos was found to be the strongest inhibitor, while AChE immobilized onto PA sorbent modified with DMAEM showed the highest stability. The possibility of using immobilized GOD and AChE in a flow-injection system for determination of the concentrations of glucose and phosphoroorganic compounds was studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68:323–329, 1998     

Electrochemically stimulated 2‐ethylhexyl phosphate (EHP) release through redox switching of conducting polypyrrole film and polypyrrole/poly (N‐methylpyrrole) or self‐doped polyaniline bilayers

2‐Ethylhexyl phosphate (EHP) released from poly(pyrrole 2‐ethylhexyl phosphate) (PP‐EHP) was investigated at open circuit and compared with electrochemically stimulated release during potential cycling. It was found that the fast EHP release from the PP‐EHP single layer is substantially retarded and that amounts of spontaneously and electrochemically released EHP can be reduced by constructing bilayers, consisting of a PP‐EHP inner layer and a poly(N‐methylpyrrole)‐poly(styrene sulfonate) (PNMP‐PSS) or self‐doped poly(aniline) sulfonate (SPANI) as the outer films. The presence of outer film over the PP‐EHP allowed surface‐property modification, as well as the control of the rate of EHP release, while electrochemically stimulated EHP release from inner films was not substantially hampered by the outer layer. The quantity of the EHP released was investigated using UV‐vis spectrophotometery and an electrochemical quartz‐crystal microbalance (EQCM) during reduction of PP‐EHP from single layer and bilayers through electrochemical stimulation. EHP was reincorporated to the inner film by applying an anodic potential and then the release of EHP was performed again. The results showed that the outer film could act as a barrier to ion‐and solvent‐transport between the inner film and electrolyte, yielding a more balanced counter‐directional movement of anions. © 2002 Society of Chemical Industry     

硝酸溶液中十二烷基苯磺酸钠对锌的缓蚀作用及吸附热力学研究

采用失重法研究了硝酸介质中烷基磺酸盐类阴离子表面活性剂对锌的缓蚀及吸附作用,考察了在不同温度的3%硝酸中,不同浓度的十二烷基苯磺酸钠对锌的缓蚀作用。实验结果表明,十二烷基苯磺酸钠能很好的抑制锌的腐蚀,当其含量达到一定浓度后,缓蚀作用基本保持不变,而其在锌表面上的吸附是产生缓蚀作用的重要原因。在浓度为0~300 mg/L时,十二烷基苯磺酸钠在锌表面的吸附规律服从Langmuir吸附等温式。用Sekine方法处理实验数据,从而获得了ΔH0、ΔS0和ΔG0等一系列相关的热力学参数。     

Immobilization of polyphenol oxidase on carboxymethylcellulose hydrogel beads: preparation and characterization

Carboxymethylcellulose (CMC) beads were prepared by a liquid curing method in the presence of trivalent ferric ions, and epicholorohydrin was covalently attached to the CMC beads. Polyphenol oxidase (PPO) was then covalently immobilized onto CMC beads. The enzyme loading was 603 µg g⁻¹ bead and the retained activity of the immobilized enzyme was found to be 44%. The K_m values were 0.65 and 0.87 mM for the free and the immobilized enzyme, and the V_max values were found to be 1890 and 760 U mg⁻¹ for the free and the immobilized enzyme, respectively. The optimum pH was 6.5 for the free and 7.0 for the immobilized enzyme. The optimum reaction temperature for the free enzyme was 40 °C and for the immobilized enzyme was 45 °C. Immobilization onto CMC hydrogel beads made PPO more stable to heat and storage, implying that the covalent immobilization imparted higher conformational stability to the enzyme. © 2000 Society of Chemical Industry     

CuBr2‐induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin‐film counter electrodes for high‐efficiency dye‐sensitized solar cells

Nanocolloidal polypyrrole (PPy):poly(styrene sulfonate) (PSS) particles were synthesized by chemical oxidative polymerization using 15 wt% of PSS. The highly processable polymer composite (PPy:PSS) was spin‐coated at 4000 rpm on fluorine‐doped tin oxide glass and subsequently employed as a counter electrode (CE) for dye‐sensitized solar cells (DSCs). PPy:PSS multilayer (one, three, five) CEs were treated with CuBr₂ salt, which enhances the efficiency of the DSCs. Optical studies reveal that a bulkier counterion hinders interchain interactions of PPy which on salt treatment shows a moderate redshift in absorption maxima. Salt‐treated PPy:PSS films exhibit lower charge transfer resistance, higher surface roughness and better catalytic performance for the reduction of I₃^?, when compared with untreated films. The improved catalytic performance of salt‐treated PPy:PSS multilayer films is attributed to charge screening and conformational change of PPy, along with the removal of excess PSS. Under standard AM 1.5 sunlight illumination, salt treatment is shown to boost the efficiency of multilayer PPy:PSS composite film‐based DSCs, leading to enhanced power conversion efficiency of 6.18, 6.33 and 6.37% for one, three and five layers, respectively. These values are significantly higher (ca 50%) than those for corresponding devices without CuBr₂ salt treatment (3.48, 2.90 and 2.01%, respectively). © 2016 Society of Chemical Industry     

Development of electrochemical oxidase biosensors based on carbon nanotube-modified carbon film electrodes for glucose and ethanol

Functionalised multi-walled carbon nanotubes (MWCNTs) were cast on glassy carbon (GC) and carbon film electrodes (CFE), and were characterised electrochemically and applied in a glucose-oxidase-based biosensor. MWCNT-modified carbon film electrodes were then used to develop an alcohol oxidase (AlcOx) biosensor, in which AlcOx-BSA was cross-linked with glutaraldehyde and attached by drop-coating. The experimental conditions, applied potential and pH, for ethanol monitoring were optimised, and ethanol was determined amperometrically at −0.3 V vs. SCE at pH 7.5. Electrocatalytic effects of MWCNT were observed with respect to unmodified carbon film electrodes. The sensitivity obtained was 20 times higher at carbon film/MWCNT-based biosensors than without MWCNT.     

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     

Synthesis and characterization of water‐soluble polypyrrole/multi‐walled carbon nanotube composites

Water‐soluble polypyrrole (PPy)/multi‐walled carbon nanotube (MWCNT) composites were prepared by mixing chemically modified MWCNTs carrying carboxylic groups (c‐MWCNTs) and sulfonated PPy (SPPy) aqueous colloids in solution. Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction, field‐emission scanning electron microscopy and high‐resolution transmission electron microscopy were used to characterize the structure and morphology of the resulting composites. Raman and X‐ray photoelectron spectra demonstrate the presence of electrostatic interactions between the radical species of the SPPy and the carboxylic acid species of the c‐MWCNTs. The addition of c‐MWCNTs into SPPy efficiently enhances its thermal stability and electrical conductivity. Owing to the doping effect and one‐dimensional linear structure of the c‐MWCNTs, the conductivity of SPPy/c‐MWCNT composites at room temperature is increased by two orders of magnitude by the introduction of 5 wt% c‐MWCNTs into the SPPy matrix. Copyright © 2010 Society of Chemical Industry     

Potassium-doped carbon nanotubes toward the direct electrochemistry of cholesterol oxidase and its application in highly sensitive cholesterol biosensor

We demonstrate herein a newly developed serum total cholesterol biosensor by using the direct electron transfer of cholesterol oxidase (ChOx), which is based on the immobilization of cholesterol oxidase and cholesterol esterase (ChEt) on potassium-doped multi-walled carbon nanotubes (KMWNTs) modified electrodes. The KMWNTs accelerate the electron transfer from electrode surface to the immobilized ChOx, achieving the direct electrochemistry of ChOx and maintaining its bioactivity. As a new platform in cholesterol analysis, the resulting electrode (ChOx/KMWNTs/GCE) exhibits a sensitive response to free cholesterol, with a linear range of 0.050–16.0 μmol L⁻¹ and a detection limit of 5.0 nmol L⁻¹ (S/N = 3). Coimmobilization of ChEt and ChOx (ChEt/ChOx/KMWNTs/GCE) allows the determination of both free cholesterol and esterified cholesterol. The resulting biosensor shows the same linear range of 0.050–16.0 μmol L⁻¹ for free cholesterol and cholesteryl oleate, with the detection limit of 10.0 and 12.0 nmol L⁻¹ (S/N = 3), respectively. The concentrations of total (free and esterified) cholesterol in human serum samples, determined by using the techniques developed in the present study, are in good agreement with those determined by the well-established techniques using the spectrophotometry.     

Humidity sensitivity of polypyrrole and polypyrrole/SBA‐15 host–guest composite materials

Polypyrrole (PPY) and PPY/SBA‐15 host–guest composite materials have been prepared using chemical synthesis route and characterized by XRD, IR, N₂ adsorption–desorption isotherms, and SEM. The humidity sensitive properties (HSP) of this kind of materials have been studied by analyzing the variation curve of impedance as a function of relative humidity. It was found that the PPY/SBA‐15 host–guest composites materials exhibit better HSP than that of the corresponding pure PPY. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3301–3305, 2006     

Well‐functioned photovoltaics based on nanofibers composed of PBDT‐TIPS‐DTNT‐DT and graphenic precursors thermally modified by polythiophene,polyaniline and polypyrrole

Reduced graphene oxide nanosheets modified by conductive polymers including polythiophene (GPTh), polyaniline (GPANI) and polypyrrole (GPPy) were prepared using the graphene oxide as both substrate and chemical oxidant. UV–visible and Raman analyses confirmed that the graphene oxide simultaneously produced the reduced graphene oxide and polymerized the conjugated polymers. The prepared nanostructures were subsequently electrospun in mixing with poly(3‐hexylthiophene) (P3HT)/phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) and poly[bis(triisopropylsilylethynyl)benzodithiophene‐bis(decyltetradecylthien)naphthobisthiadiazole] (PBDT‐TIPS‐DTNT‐DT)/PC₇₁BM components and embedded in the active layers of photovoltaic devices to improve the charge mobility and efficiency. The GPTh/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM devices demonstrated better photovoltaic features (J_sc = 11.72 mA cm^?2, FF = 61%, V_oc = 0.68 V, PCE = 4.86%, μ_h = 8.7 × 10^?3 cm² V^–1 s^?1 and μ_e = 1.3 × 10^?2 cm² V^–1 s^?1) than the GPPy/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.30 mA cm^?2, FF = 60%, V_oc = 0.66 V, PCE = 4.08%, μ_h = 1.4 × 10^?3 cm² V^–1 s^?1 and μ_e = 8.9 × 10^?3 cm² V^–1 s^?1) and GPANI/PBDT‐TIPS‐DTNT‐DT/PC₇₁BM (J_sc = 10.48 mA cm^?2, FF = 59%, V_oc = 0.65 V, PCE = 4.02%, μ_h = 8.6 × 10^?4 cm² V^–1 s^?1 and μ_e = 7.8 × 10^?3 cm² V^–1 s^?1) systems, assigned to the greater compatibility of PTh in the nano‐hybrids and the thiophenic conjugated polymers in the bulk of the nanofibers and active thin films. Furthermore, the PBDT‐TIPS‐DTNT‐DT polymer chains (3.35%–5.04%) acted better than the P3HT chains (2.01%–3.76%) because of more complicated conductive structures. © 2019 Society of Chemical Industry     

Aqueous dispersions of DBSA‐doped polyaniline: One‐pot preparation,characterization, and properties study

Aniline was polymerized in the presence of dodecylbenzene sulfonic acid (DBSA) as a functionalized protonic acid, in an aqueous medium to directly synthesize polyaniline (PANI)‐DBSA particles. DBSA acted as a dopant and a surfactant with stabilizing PANI‐DBSA dispersions by formation of strong hydrogen bonds. The NH⁺…SO interactions between the PANI chains and the DBSA appeared at 1026 cm^?1 in Fourier transform infrared (FTIR) spectrum. Elemental analysis was used to determine the degree of sulfonation (S/N ratio) of PANI chains and resulted that the sulfur‐to‐nitrogen ratio is 0.35. Thermogravimetric analysis (TGA) technique was used to analyze thermal properties of the particles and resulted that the synthesized PANI‐DBSA particles have high thermal stability. The moisture, DBSA and PANI contents of the PANI‐DBSA were estimated from TGA curve, and then the number of aniline repeating units doped with one DBSA molecule was approximately calculated. X‐ray diffraction (XRD) analysis confirmed that a chemical crosslinking reaction occurs between the PANI chains during thermal treatment of PANI‐DBSA. The morphology of PANI‐DBSA powder was investigated by scanning electron microscopy technique and showed that the PANI particles develops from round particles to a smooth surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009