Enhanced sensitivity for biosensors: multiple functions of DNA-wrapped single-walled carbon nanotubes in self-doped polyaniline nanocomposites

A nanocomposite of poly(anilineboronic acid), a self-doped polyaniline, with ss-DNA-wrapped single-walled carbon nanotubes (ss-DNA/SWNTs) was fabricated on a gold electrode by in situ electrochemical polymerization of 3-aminophenylboronic acid monomers in the presence of ssDNA/SWNTs. We used this nanocomposite to detect nanomolar concentrations of dopamine and found that the sensitivity increased 4 orders of magnitude compared to the detection at an electrode modified with only poly(anilineboronic acid). For the first time, this work reports the multiple functions of the ss-DNA/SWNTs in the fabrication and biosensor application of a self-doped polyaniline/ss-DNA/SWNT nanocomposite. First, the ss-DNA/SWNTs acted as effective molecular templates during polymerization of self-doped polyaniline so that not only was the polymerization speed increased but also the quality of the polymer was greatly improved. Second, they functioned as novel active stabilizers after the polymerization, significantly enhancing the stability of the film. Furthermore, the ss-DNA/SWNTs also acted as conductive polyanionic doping agents in the resulting polyaniline film, which showed enhanced conductivity and redox activity. Finally, the large surface area of carbon nanotubes greatly increased the density of the functional groups available for sensitive detection of the target analyte. We envision that polyaniline with other functional groups as well as other conducting polymers may be produced for different targeted applications by this approach.     

Saccharide imprinting of poly(aniline boronic acid) in the presence of fluoride

A new approach for the electrosynthesis of saccharide-imprinted poly(aniline boronic acid) is described. The method involves the formation of a saccharide-aminophenylboronic acid complex in the presence of fluoride to allow the electropolymerization of a self-doped, molecularly imprinted polyaniline. The formation of the anionic monomer complex enables electrochemical polymerization at near neutral pH (5-7) ensuring the incorporation of saccharide in the resulting, self-doped polymer. In this work, films were imprinted with D-fructose where saccharide-aminophenylboronic acid complexation occurred in the presence of one equivalent of fluoride. The selectivity toward D-fructose relative to D-glucose showed an increase of over 25% as a result of imprinting. In addition to the enhanced selectivity, to the best of our knowledge this is the first example of the electropolymerization of a self-doped polyaniline homopolymer under neutral pH conditions.     

In situ fabrication of a water-soluble, self-doped polyaniline nanocomposite: the unique role of DNA functionalized single-walled carbon nanotubes

Dispersion of carbon nanotubes into solvents affects their surface chemistries, electronic structures, and subsequent functionalization. In this Communication, a water-soluble self-doped polyaniline nanocomposite was fabricated by in situ polymerization of the 3-aminophenylboronic acid monomers in the presence of single-stranded DNA dispersed- and functionalized-single-walled carbon nanotubes. For the first time, we found that the carbon nanotubes became novel active stabilizers owing to the DNA functionalization. The nanotubes reduced the polyaniline backbone from the unstable, degradable, fully oxidized pernigraniline state to the stable, conducting emeraldine state because of their reductive ability, which could improve the chemical stability of the self-doped polyaniline. Electrical measurements demonstrate that the conductivity of the nanocomposite was much higher than that of the pure self-doped polyaniline in both acidic and neutral solutions.     

Synthesis of self-doped conducting polyaniline bearing phosphonic acid

As a self-doped conducting polyaniline bearing phosphonic acid, poly(2-methoxyaniline-5-phosphonic acid) (PMAP) was synthesized via oxidative polymerization of 2-methoxyaniline-5-phosphonic acid. The pyridinium salt of thus-obtained PMAP was water-soluble and its film exhibited conductivity.     

A novel water-soluble and self-doped conducting polyaniline graft copolymer

A water-soluble and self-doped conducting polyaniline graft copolymer, poly(styrenesulfonic acid-g-aniline) (PSSA-g-PANI), was first synthesized and its electrical properties were investigated.     

The electronic role of DNA-functionalized carbon nanotubes: efficacy for in situ polymerization of conducting polymer nanocomposites

We have found that the polymerization process was 4,500 times faster when a self-doped polyaniline nanocomposite was fabricated using in situ polymerization in the presence of single-stranded DNA-dispersed and -functionalized single-walled carbon nanotubes (ssDNA-SWNTs). More importantly, the quality of the composite was significantly improved: fewer short oligomers were produced, and the self-doped polyaniline backbone had a longer conjugation length and existed in the more stable and conductive emeraldine state. The functionality of the boronic acid group in the composite and the highly improved electronic performance may lead to broad applications of the composite in flexible electronic devices. Blending of preformed polymer with carbon nanotubes is straightforward and widely used to fabricate nanocomposites. We demonstrate that this simple mixing approach might not fully and synergistically combine the merits of each individual component. Surprisingly, these advantages also cannot be obtained using in situ polymerization with preoxidized ssDNA-SWNTs, which is renowned as the "seed" method for production of conducting-polymer nanowires. The electronic structures of the carbon nanotubes and the monomer-nanotube interaction during polymerization greatly impact the kinetics of nanocomposite fabrication and the electronic performance of the resulting composites.     

低头-头链含量的聚偏氟乙烯合成

研究了偏氟乙烯的聚合条件与其聚合物的头-头链含量的关系。实验表明聚合物的头-头链的含量与聚合温度有关,而与引发剂的种类无关。因而,可以在较低的聚合温度下聚合制得带有低的头-头结构(约3％)的聚偏氟乙烯。将聚合物链的A结构含量对其熔点作图,得一直线,可表示为方程式A=24.8+0.362T_m(％)。     

Amperometric determination of ascorbic acid at a novel ‘self-doped’ polyaniline modified microelectrode

A ‘self-doped’ polyaniline modified microelectrode, prepared by cyclic potential sweep on a microdisk gold electrode from –0.2 to 0.85 V in 0.5 mol/L sulfuric acid containing aniline and o-aminobenzoic acid, has been developed. The copolymerized process and the resulting polymer characteristics were investigated in detail. This composite film indicated a good electrochemical activity in a wide pH range even in basic solution. Meanwhile, the redox couple exhibited an excellent electrocatalytic activity for the oxidation of ascorbic acid. The oxidation overpotential of ascorbic acid was decreased over 200 mV at this modified electrode compared with a bare gold one. Moreover, the effects of film thickness and pH on the catalytic efficiency were further studied. The dependence of catalytic currents on the concentration of ascorbic acid was linear in the range of 1.2 × 10^–5～ 2.4 × 10^–3 mol/L with a correlation coefficient of 0.996. Also, the determination of ascorbic acid in actual samples was evaluated and the results are satisfactory.     

Glucose biosensor based on three dimensional ordered macroporous self-doped polyaniline/Prussian blue bicomponent film

In this paper, a three dimensional ordered macroporous self-doped polyaniline/Prussian blue (3DOM SPAN/PB) bicomponent film was fabricated via the inverted crystal template technique using step-by-step electrodeposition. In this bicomponent film, PB not only acted as a redox mediator, but also presented increased stability in neutral or weak alkaline solution by the protection of SPAN layer on the top. A novel glucose biosensor was fabricated based on the large active surface area and excellent conductivity possessed by the 3DOM SPAN/PB film. The applying experimental conditions of the glucose biosensor have been optimized. Under the optimal conditions, the biosensor showed a wide linear range over three orders of magnitude in glucose concentrations (from 2 to 1600 μM) and a low detection limit of 0.4 μM. Moreover, the biosensor exhibited short response time, high selectivity and excellent operation stability, which can be applied to detect the blood sugar in real samples without any pretreatment.     

SYNTHESIS OF POLY(VINYLIDENE FLUORIDE) WITH LOW CONTENTS OF HEAD-TO-HEAD CHAIN

The relations between polymerization conditions of vinylidene fluoride and contents of head-tohead chain in the polymer have been studied. It shows that the contents of head-to-head chain of the polymer are related to its polymerization temperature, but are not related with the kinds of initiators used. Therefore, poly(vinylidene fluoride) with low contents of head-to-head chain (ca. 3%) can be prepared under lower polymerization temperature. Plot of the contents of A chains against melting points of the polymer is linear, which can be expressed by an equation: A=24.8 + 0.362 T_m(%).     

Electropolymerization of 2-aminophenylboronic acid and the use of the resulting polymer for determination of sugars and oxyacids

Electropolymerization of aminophenylboronic acids proceeds by the mechanism typical of conducting polyaniline, if the substituent in the ring is the electron donor and its position favors the electrophilic substitution into the para position with respect to the amino group in the ring. For the same reason, the polymerization of meta-aminophenylboronic acid requires the presence of fluoride ions to transform the weak electron acceptor, boronic acid group into the electron-donating trifluoroborate anion. It is shown that electropolymerization of ortho-aminophenylboronic acid can be carried out in strongly acidic media in the absence of fluoride ions, in analogy to unsubstituted polyaniline. The conductivity of the resulting polyanilineboronic acids synthesized under optimal conditions increases upon their binding with sugars and oxyacids, which allows detecting the specific interactions only, while the nonspecific interactions lower down the polymer conductivity.     

A Novel Potentiometric Glucose Biosensor Based on Polyaniline Semiconductor Films

Abstract

Application of polyaniline semiconductor films to potentiometric biosensor development provides certain advantages comparing with the known systems. Using self-doped polyaniline instead of common polymer as pH transducer the stable potentiometric response of 70 mV/pH was obtained. Taking as an example glucose biosensor we showed that polyaniline based electrode possessed three-four fold increased potential shift than glucose-sensitive field-effect transistor did. One can increase the sensitivity of potentiometric biosensor using thick ion-exchange membranes (in our case Nafion) in order to concentrate product near electrode surface. Such sensor possessed higher response time.     

Electrochemical polymerization of substituted thiophenes

The electrochemical polymerization of 3-(n-butyl)thiophene and of several 3- or 3,4- substituted α, α'-terthienyls is described and the properties of the conducting polymers are discussed. A solution in acetonitrile of the terthienyl substituted by a potassium propylsulfonate group is polymerizable as such, and the polymer is the first proven example of a self-doped conducting polymer. This polymer dissolves readily in water and remains partially self-doped in solution.     

Electrochemical synthesis of self-doped polyaniline and its use to the electrooxidation of ascorbic acid

Self-doped polyaniline (PAN) film on platinum electrode surface has been synthesized via electrochemical copolymerization of aniline with orthanilic acid (OAA). Fourier transform infrared, UV–Vis, and elemental analysis indicate the formation of the copolymer and that the copolymer has the structure of a head-to-tail coupling of aniline and OAA units. It was found that the internal doping of PAN with OAA can extend the electroactivity of PAN in neutral and even in alkaline media. The obtained self-doped PAN (PAN-OAA)-coated platinum electrode is shown to be a good surface for the electrooxidation of ascorbic acid (AA) in phosphate buffer solution of pH 7. The anode peak potential of AA shifts from 0.63 V at bare platinum electrode to 0.34 V at the PAN-OAA-modified platinum electrode with greatly enhanced current response. A linear calibration graph is obtained over the AA concentration range of 5–60 mM using cyclic voltammetry. Rotating disk electrode voltammetry and chronoamperometry have been employed to investigate the electrooxidation of AA. The PAN-OAA-modified platinum electrode shows good stability and reproducibility.     

A glassy carbon electrode modified with a nanocomposite consisting of molybdenum disulfide intercalated into self-doped polyaniline for the detection of bisphenol A

Thin-layered molybdenum disulfide (MoS₂) was intercalated, via ultrasonic exfoliation, into self-doped polyaniline (SPAN). This material, when placed on a glassy carbon electrode (GCE), exhibits excellent electrical conductivity and synergistic catalytic activity with respect to the detection of bisphenol A (BPA). The electrochemical response of the modified GCE to BPA was investigated by cyclic voltammetry and differential pulse voltammetry. Under optimal conditions, the oxidation peak current (measured best at 446 mV vs. SCE) is related to the concentration of BPA in the range from 1.0 nM to 1.0 μM, and the detection limit is 0.6 nM.

Thin-layered molybdenum disulfide (MoS₂) was intercalated into self-doped polyaniline (SPAN) via ultrasonic exfoliation. The special conjugated structure and functional groups of MoS₂-SPAN composite help to adsorb BPA easily. MoS₂-SPAN has a synergistic effect for catalyzing the oxidation of BPA. The BPA electrochemical sensor based on MoS₂-SPAN has a high sensitivity and low detection limit.

     

自掺杂磺酸化聚苯胺之最优化实验设计(英文)

应用实验设计法包括部分析因设计与中心组合设计,优化自掺杂磺酸化聚苯胺的导电性.部分析因设计发现,需用低温(4℃)、短反应时间(1 h)和少量发烟硫酸(10 mL)等实验条件进行磺酸化反应才能得到好的导电性(ca.127 mS.cm-1);中心组合设计与确认实验表明,其最佳导电性(ca.141 mS/cm)的磺酸化条件是4℃、75 m in反应时间以及8 mL 30%的发烟硫酸.应用傅立叶变换红外光谱(FTIR)、四探针与X光光电子能谱等分析制备的材料.此外,发现磺酸化速率与程度与聚合反应时所使用的酸有关.     

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline (PANi) and polyaniline-poly(vinylidene fluoride) blend (PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.     

聚苯胺/贵金属复合纳米材料的可控合成及催化应用

导电高分子/贵金属复合纳米材料因其在催化、传感、表面增强拉曼、光热治疗等诸多领域的应用前景而受到广泛关注.本文主要介绍我们课题组近年来利用可控合成策略制备的负载型和包埋型两种结构聚苯胺/贵金属复合纳米材料,以及利用复合纳米材料的结构和功能特性,对其在多相催化领域的应用、结构与催化性能之间构效关系的探索.     

Electrochemical Polymerization of Aniline in Polyamide and Polyvinyl Alcohol Matrices

The electrochemical polymerization of aniline was studied in polymer matrices (polyamid-12 and polyvinyl alcohol) on an electrode in the potential cycling mode from –0.2 to +0.8 V vs. SCE. The indices of this process such as the potentials and currents of the polyaniline redox peaks, polymerization rate, and properties of the conducting composite formed depend on the nature of the matrix polymer and are a function of the extent of interaction of this matrix polymer with aniline and polyaniline.     

Plasma polymerization of aniline on different surface functionalized substrates

The plasma polymerization of aniline on different surface functionlized low-density polyethylene (LDPE) substrates was investigated, and the resulting polymer was characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy. The results showed that the structure of plasma-polymerized polyaniline was rather different from polyaniline synthesized by conventional chemical and electrochemical methods. This difference may be due to extensive coupling reactions and cross-linking reactions during the plasma polymerization process. The use of acrylic acid graft copolymerized LDPE substrate significantly enhanced the adhesion of the polyaniline to the substrate over that observed with pristine LDPE. The plasma polymerized polyaniline can be rendered electrically conductive if the polymerization is carried out on a polystyrenesulfonic acid-coated LDPE substrate. Conductivity can also be induced by acid protonation of the polyaniline by HClO(4). The reaction of the plasma-polymerized polyaniline with viologen grafted on the substrate under UV irradiation and with AuCl(3) and Pd(NO(3))(2) in acid solutions was also investigated.