Yangping Wen

Electroactive species-doped poly(3,4-ethylenedioxythiophene) films: enhanced sensitivity for electrochemical simultaneous determination of vitamins B2, B6 and C.

Herein, functionalized PEDOT films were prepared by incorporation of two electroactive species, ferrocenecarboxylic acid (Fc(-)) and ferricyanide (Fe(CN)6(4-)) as doping anions during the electropolymerization of PEDOT at glassy carbon electrodes (GCEs) from aqueous solution. The electrochemically synthesized electroactive species-doped PEDOT films have been carefully characterized by scanning electron microscopy (SEM), FTIR and UV/Vis spectra and various electrochemical techniques. Such nanostructured films combined the advantages of PEDOT (high conductivity and stability) together with electroactive species (good electrochemical activity) and were applied as electrochemical sensors for simultaneous determination of vitamin B2 (VB2), vitamin B6 (VB6) and vitamin C (VC). The results showed that the oxidation peak currents of vitamins obtained at the GCEs modified with electroactive species-doped PEDOT films were much higher than those at the ClO4(-)-doped PEDOT films and bare GCEs. The experiment results also illustrated that the sensors possessed high selectivity with no interference from other potential competing species. Moreover, the proposed sensors were successfully employed for the determination of vitamins in orange juice samples with satisfactory results.

Electrochemical recognition and trace-level detection of bactericide carbendazim using carboxylic group functionalized poly(3,4- ethylenedioxythiophene) mimic electrode

The electrochemical recognition and trace-level detection of bactericide carbendazim (MBC) in paddy water and commercial juice were realized using carboxylic group functionalized poly(3,4-ethylenedioxythiophene) (PC4-EDOT-COOH) film electrode. PC4-EDOT-COOH film was prepared by one step, low-cost, and green electrosynthesis in aqueous microemulsion system and characterized by FT-IR, cyclic voltammetry, UV-vis and SEM. In comparison with poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDTM), PC4-EDOT-COOH exhibited the best electrochemical recognition towards MBC and the recognition mechanism was proved by quantitative calculation. Sensing parameters such as pH values, accumulation potential, accumulation time, supporting electrolyte, and scan rate on the current response of MBC were discussed. In addition, the sensor can be applied to quantification of MBC in the concentration range of 0.012-0.35 μM with a low detection limit of 3.5 nM (S/N=3). Moreover, PC4-EDOT-COOH film electrode showed good stability, high selectivity, and satisfactory anti-interference ability. Satisfactory results indicated that PC4-EDOT-COOH film is a promising sensing platform for the trace-level analysis of bactericide residue carbendazim in agricultural crops and environment.

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.

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.

Water-dispersed carboxymethyl cellulose-montmorillonite-single walled carbon nanotube composite with enhanced sensing performance for simultaneous voltammetric determination of two trace phytohormones

A simple and sensitive method for the simultaneous voltammetric detection of two trace phytohormones both indole-3-acetic acid (IAA) and salicylic acid (SA) was successfully realized using composite film modified glassy carbon electrode (GCE) with enhanced sensing performance. Carboxymethyl cellulose (CMC), a water-soluble biopolymer with good film-forming ability and adhesive property was selected as the disperser, stabilizer, and binder for improving the water-dispersibility of single-walled carbon nanotube (SWCNT) with excellent electrocatalytic ability and montmorillonite (MMT) with high effective surface area and surface adsorption capacity, and enhancing the water stability and adhesion between the coating and substrate electrode. CMC-SWCNT-MMT/GCE displayed enhanced electrode stability in water, effective surface area, adhesive property and adsorption capacity, and good electrocatalytic activity for the oxidation of both IAA and SA, which could simultaneously detected two trace phytohormones with high sensitivity, low detection limit, and good sensing stability. Satisfactory results indicated the water-dispersed CMC-SWCNT-MMT with enhanced sensing performance provided a promising platform for the electrochemical application of high-performance composite film-modified electrode.

Preparation of black phosphorus-PEDOT:PSS hybrid semiconductor composites with good film-forming properties and environmental stability in water containing oxygen

The environmental instability of black phosphorus (BP) is one of the difficult issues nowadays that need to be addressed urgently due to its serious degradation, damage in structure and deterioration in properties after exposure to ambient conditions, which severely limits the practical application of BP and its devices under humidity circumstances containing oxygen, particularly watery environments containing oxygen. In this study, PEDOT:PSS with high electrical conductivity, good film-forming ability, excellent environmental stability, and satisfactory solution processability was introduced to improve the environmental instability of BP with unusual structure and extraordinary properties. The mixed dispersions of BP-PEDOT:PSS with different weight ratios were successfully prepared by sonication-assisted liquid-phase exfoliation in isopropanol containing PEDOT:PSS particles under an anhydrous and oxygen-free nitrogen atmosphere. The hybrid semiconductor films of BP-PEDOT:PSS were obtained by drying corresponding BP-PEDOT:PSS mixed dispersions under vacuum; these films were then exposed to ambient air for days before their morphology, structure, and other properties were characterized. The BP-PEDOT:PSS film electrodes were prepared by drop-coating corresponding isopropanol dispersions of BP-PEDOT:PSS, and their environmental stabilities were investigated by electrochemistry in different water systems containing oxygen. The introduction of PEDOT:PSS not only enhanced film-forming ability and electrical conductivity of BP composite films, but also improved their environmental stability in water containing oxygen, which will afford a new opportunity for their application in electronics and optoelectronics of inorganic/organic polymer hybrid semiconductors based on graphene-like materials/conducting polymers under moist air conditions, particularly the electrochemical application in sensors, capacitors, and batteries/cells of BP-PEDOT:PSS composites and their devices in watery environments containing oxygen.