Xuemin Duan

Synthesis and electrochromic properties of polyacrylate functionalized poly(3,4-ethylenedioxythiophene) network films

A novel acrylate modified 3,4-ethylenedioxythiophene (EDOT-AA) was synthesized, and its free radical polymerization and electrochemical polymerization led to the formation of corresponding precursor polymer polyacrylate (PAA) functionalized with 3,4-ethylenedioxythiophene (EDOT-PAA) and uniform electrodeposition of acrylate modified poly(3,4-ethylenedioxythiophene) (PEDOT-AA) and polyacrylate modified poly(3,4-ethylenedioxythiophene) (PEDOT-PAA), respectively. The structure, electrochemical, optical, thermal properties and morphology of as-formed polymers were systematically investigated by FT-IR, cyclic voltammetry, UV–vis, thermogravimetry (TG) and scanning electron microscopy (SEM). Cyclic voltammetry and spectroelectrochemistry studies demonstrated that PEDOT-AA and PEDOT-PAA can be reversibly oxidized and reduced accompanied by obvious color changes from dark brown to transmissive blue for PEDOT-AA, and from magenta to blue for PEDOT-PAA. The introduction of the acrylate group significantly improves the electrochromic properties of PEDOT and results in high contrast ratios (ΔT% = 50.9 % at 620 nm for PEDOT-AA) and coloration efficiencies (339 cm2 C−1 for PEDOT-AA and 211 cm2 C−1 for PEDOT-PAA), low switching voltages and fast response time (1.4 s for PEDOT-AA and 0.9 s for PEDOT-PAA).

Electrosynthesis and characterization of poly(hydroxy-methylated-3,4-ethylenedioxythiophene) film in aqueous micellar solution and its biosensing application

A new and efficient synthetic route to hydroxymethylated-3,4-ethylenedioxylthiophene (EDOT-MeOH) was developed by a simple four-step sequence, and its global yield was approximately 41.06%. The poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDOT-MeOH) film was electrosynthesized in aqueous sodium dodecylsulfate micellar solutions and characterized by different methods. The EDOT-MeOH possessed better water solubility, and lower onset oxidation potential than EDOT. The as-obtained PEDOT-MeOH film displayed good reversible redox activity, stability and capacitance properties in a monomer-free electrolyte, especially the good solubility of PEDOT-MeOH film in strong polar organic solvents such as dimethyl sulfoxide and tetrahydrofuran created a potential application in many different fields. Fluorescent spectra indicated that PEDOT-MeOH was a yellow-green-light-emitter with maximum emission at 568 nm. The as-formed PEDOT-MeOH film had good biocompatibility and was used for fabricating the electrochemical vitamin C biosensor. The proposed biosensor showed a linear range of 3 × 10−6 mol/L to 1.2 × 10−2 mol/L with the detection limit of 1 μmol/L, a sensitivity of 95.6 μA (mmol/L)− cm−2, and a current response time less than 10 s and a fairly good stability (The relative standard deviation was 0.43% for 20 successive assays, the proposed biosensor still retained 93.5% of bioactivity after 15 days storage. This result indicated that the prepared PEDOT-MeOH film as immobilization matrix of biologically-active species could be a promising candidate for the design and application of biosensor.

Facile synthesis of the necklace-like graphene oxide-multi-walled carbon nanotube nanohybrid and its application in electrochemical sensing of Azithromycin

A novel electrochemical platform was designed for the determination of Azithromycin (Azi), a widely used macrolide antibiotic, by combining the hydrophilic properties of graphene oxide (GO) and the excellent electronic and antifouling properties of multi-walled carbon nanotubes (MWCNTs). Stable MWCNTs aqueous dispersion has been prepared using GO nano-sheets as surfactant and the obtained GO-MWCNTs nanohybrid was characterized by UV-vis spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, transmission electron microscopy and electrochemical impedance spectroscopy, which confirmed that GO nano-sheets were attached onto the wall of MWCNTs to form a necklace-like structure. Electrochemical results obviously reveal that the oxidation peak currents of Azi obtained at the GC electrode modified with GO-MWCNTs hybrid are much higher than those at the MWCNTs/GC, GO/GC and bare GC electrodes. Under optimized conditions, the anodic peak current was linear to the concentration of Azi in the range from 0.1 to 10 μM with the detection limit of 0.07 μM. To further validate its possible application, the proposed method was successfully used for the determination of Azi in pharmaceutical formulations with satisfactory results.

Synthesis of novel chiral L-leucine grafted PEDOT derivatives with excellent electrochromic performances

Two amino acid-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, poly(N-(tert-butoxycarbonyl)-L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide) (PEDOT–Boc–Leu) and poly(L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide) (PEDOT–Leu) were synthesized electrochemically via potentiostatic polymerization of corresponding monomers N-(tert-butoxycarbonyl)L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide (EDOT–Boc–Leu) and L-leucyl(3,4-ethylenedioxythiophene-2′-yl)methylamide (EDOT–Leu), which were synthesized by grafting Boc-L-leucine and L-leucine into a 3,4-ethylenedioxythiophene (EDOT) side chain. The electrochemical behaviors, structural characterization, circular dichroism, spectroscopic properties, surface morphology, electrochromic properties and thermal stabilities of PEDOT–Boc–Leu and PEDOT–Leu films were systematically investigated. These L-leucine grafted PEDOT derivatives displayed excellent reversible redox activities, rough and compact surface, and good thermal stability. The circular dichroism spectra suggested the chirality of these polymers. Importantly, the introduction of the L-leucine group enhanced the electrochromic properties of PEDOT and resulted in high contrast ratios (ΔT% = 49% at 600 nm for PEDOT–Boc–Leu) and high coloration efficiencies (431 cm2 C−1 at 960 nm for PEDOT–Leu). Satisfactory results implied that the obtained polymer films can probably be further developed in various applications, such as electrochromic devices, optical displays and chiral recognition.

Trace analysis of Ponceau 4R in soft drinks using differential pulse stripping voltammetry at SWCNTs composite electrodes based on PEDOT:PSS derivatives.

Ponceau 4R, an edible synthetic colorant used in drinks, syrups, and sweets, has been successfully detected using differential pulse voltammetry at a single-walled carbon nanotubes-modified composite electrode based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) and two derivatives thereof. The electrochemical parameters of three Ponceau 4R sensors, such as pH value, pre-concentration time, and scan rate, have been optimized, and their electrochemical performances have been compared. A poly(acrylate-modified 3,4-ethylenedioxythiophene-co-3,4-ethylenedioxythiophene):poly(styrene sulfonate)-single-walled carbon nanotubes-poly(vinyl alcohol)-modified electrode showed the best electrocatalytic activity, with the highest response current, lowest detection limit (1.8 nm), widest linear range (0.0055-110.6 μm), and best sensing stability. Additionally, the modified electrode has also been successfully employed for real sample analysis with soft drinks. Satisfactory results were obtained, demonstrating this to be an easy and effective approach for trace analysis of Ponceau 4R in food samples.

Electrochemical sensing application of poly(acrylic acid modified EDOT- co -EDOT):PSS and its inorganic nanocomposite with high soaking stability, adhesion ability and flexibility

A novel and simple strategy to prevent swelling, disintegration, cracking and peeling-off of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) film in water was developed. This strategy was based on the film of a conducting polymer, poly(acrylic acid modified EDOT-co-EDOT):PSS (poly(EDOT-co-EDOT-AA):PSS). The film had high soaking stability, good adhesive ability, and high flexibility, which are crucial to maintaining long-term electrode stability in water of the PEDOT:PSS film. The most widely studied novel carbon nanomaterial, graphene, and a unique and versatile clay nanomaterial, halloysite, were introduced into poly(EDOT-co-EDOT-AA):PSS aqueous dispersion to prepare organic polymer–inorganic nanocomposites. Use of poly(EDOT-co-EDOT-AA):PSS film and its composite films as electrode coatings enabled long-term high performance of the film electrodes and provided high electrode stability and high adhesive ability. The structure, optical, flexibility, conductivity properties and morphology of poly(EDOT-co-EDOT-AA):PSS and its composites were systematically investigated. The performance of poly(EDOT-co-EDOT-AA):PSS film and its composite films, and their electrodes in sensing applications was also evaluated. The as-prepared electrochemical electrodes displayed high electrocatalytic activity in the detection of epinephrine, tryptophan, maleic hydrazide, and vitamin B6, as well as high sensing stability. The results indicated that poly(EDOT-co-EDOT-AA):PSS and its composites had potential applications for various electrode coatings.

A cost-effective and practical polybenzanthrone-based fluorescent sensor for efficient determination of palladium (II) ion and its application in agricultural crops and environment.

A highly selective and sensitive fluorescent chemosensor suitable for practical measurement of palladium ion (Pd(2+)) in agricultural crops and environment samples has been successfully fabricated using polybenzanthrone (PBA). PBA was facilely electrosynthesized in the mixed electrolyte of acetonitrile and boron trifluoride diethyl etherate. The fluorescence intensity of PBA showed a linear response to Pd(2+) in the concentration range of 5 nM-0.12 mM with a detection limit of 0.277 nM and quantification limit of 0.925 nM. Different compounds existing in agricultural crops and environment such as common metal ions, anions, natural amino acids, carbohydrates, and organic acids were used to examine the selectivity of the as-fabricated sensor, and no obvious fluorescence change could be observed in these interferents and their mixtures. A possible mechanism was proposed that the coordination of PBA and Pd(2+) enhance the aggregation of polymer chains, which led to a significant quenching of PBA emission, and this was further confirmed by absorption spectra monitoring and transmission electron microscopy. The excellent performance of the proposed sensor and satisfactory results of the Pd(2+) determination in practical samples suggested that the PBA-based fluorescent sensor for the determination of Pd(2+) will be a good candidate for application in agriculture and environment.

Poly(3,4-ethylenedioxythiophene methanol)/ascorbate oxidase/nafion-single-walled carbon nanotubes biosensor for voltammetric detection of Vitamin C

Vitamin C (VC) content in commercial juices was voltammetrically determined using a highly selective and sensitive poly(3,4-ethylenedioxythiophene methanol)/ascorbate oxidase/Nafion-single-walled carbon nanotubes (PEDOTM/AO/Nafion-SWCNT) biosensor. The biocompatible PEDOTM matrix was prepared facilely by the one-step electrochemical deposition technique in lithium perchlorate aqueous solutions. AO was dip-coated on the surface of the biocompatible PEDOTM matrix. The mixture of Nafion-SWCNT was dip-cast onto the surface of AO layer when it was obtained by blending Nafion solution and SWCNT dispersion together in a volume ratio of 1:1. The prepared PEDOTM/AO/Nafion-SWCNT biosensor was used for the voltammetric determination of VC, which exhibited the good linear range (4.0 × 10−5−3 × 10−3 mol/L), low detection limit (13 μmol/L), pronounced sensitivity (1.4072 mA (mmol/L)−1 cm−2), high bioaffinity (low apparent Michaelis-Menten constant), good stability (good repeatability), high specificity (good anti-interference ability) coupled with the good reliability and feasibility (the determination of VC in commercial juices). Meanwhile, the good aqueous solubility and the low onset oxidation potential of EDOTM will be more beneficial to the application in biosensor field compared to 3,4-ethylenedioxythiophene. Moreover, the good biocompatibility of PEDOTM matrix and high selectivity of Nafion-SWCNT films also provide a promising platform for the development of biosensing devices.

Electrosynthesis and characterization of aminomethyl functionalized PEDOT with electrochromic property

We herein report the electrosynthesis of an aminomethyl functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivative, poly(2′-aminomethyl-3,4-ethylenedioxythiophene) (PEDOT-MeNH2), in CH2Cl2-Bu4NPF6 (0.1 mol·L-1) system containing 2% boron trifluoride diethyl etherate (BFEE). The electrochemical behavior, structure characterization, thermal properties and surface morphology of this novel polymer were systematically investigated by cyclic voltammetry (CV), Fourier-transform infrared spectroscopy (FTIR), thermogravimetry (TG) and scanning electron microscopy (SEM), respectively. Electrochemistry results demonstrated that PEDOT-MeNH2 film displayed good redox properties and high electrochemical stability. Besides, PEDOT-MeNH2 films exhibited the electrochromic nature with obvious color changing from purple in the reduced form to blue upon oxidation. By further investigation, kinetic studies revealed that PEDOT-MeNH2 film had decent contrast ratio (41.8%), favorable coloration efficiency (152.1 cm2·C-1), low switching voltages and moderate response time (2.4 s). Satisfactory results implied that the obtained PEDOT-MeNH2 film is a promising optoelectronic material and holds promise for electrochromic devices and display applications.

Graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene): enhanced sensitivity for electrochemical determination of rutin and ascorbic acid

A novel graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene) (PEDOT-MeOH/GO) composite film was synthesized and utilized as an efficient electrode material for simultaneous detection of rutin and ascorbic acid (AA). PEDOT-MeOH/GO films were synthesized on glassy carbon electrode (GCE) by a facile one-step electrochemical approach and were characterized by scanning electron microscopy, UV-Vis spectroscopy, FTIR spectra and electrochemical methods. Then the PEDOT-MeOH/GO/GCE was applied successfully in the simultaneous detection of rutin and AA. The results showed that the oxidation peak currents of rutin and AA obtained at the PEDOT-MeOH/GO/GCE were much higher than those at the traditional conducting polymer PEDOT/GO/GCE, PEDOT-MeOH/GCE, PEDOT/GCE and bare GCE. Under optimized conditions, the linear ranges for rutin and AA are 20 nmol/L−10 μmol/L and 8 μmol/L−1 mmol/L, respectively. The detection limit is 6 nmol/L for rutin and 2 μmol/L for AA (S/N = 3), which are lower than those of the reported electrochemical sensors.