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/Nation-SWCNT） biosensor. The biocompatible PEDOTM matrix was prepared facilely by the one-step electrochemical deposition technique in lithium perehlorate 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 Nation 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-s-3 x 10-s mol/L）, low detection limit （13 I^mol/L）, pronounced sensitivity （1.4072 mA （mmol/L） i cm 2）, high bioaftinity （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 Nation-SWCNT films also provide a promising platform for the development of biosensing devices.
Yang-ping WenDong LiYao Lu贺浩华徐景坤Xue-min DuanMing Liu
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-MeOIq） 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 rim. 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） ^-1 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.
Novel conducting oligocatecholborane （OCOB） with electrical conductivity of 3.73 × 10^-2 S cm-1 was successfully synthesized by low-potential electropolymerization of catecholborane （COB） in boron trifluoride diethyl etherate at 0.70 V versus Ag/AgC1. FT-IR and ^1H-NMR spectra, together with the computational results, proved that COB was polymerized through the coupling at C（4） and C（5} positions and the reactive B- H bond was stable during the electrochemical polymerization. The resulting product was mainly composed of oligomers with short chain lengths by GPC and mass spectral results. The as-formed OCOB film showed good electrochemistry in monomer-free electrolytes with the electrochromic property from opaque blue to sap green. Fluorescence studies indicated that soluble OCOB can emit bright blue light under excitation of 365 nm UV light with the maximum emission at 396 nm and a fluorescence quantum yield of 0.21. The deposited OCOB also exhibited favorable thermal stability and smooth and compact morphology even at high magnifications.
A simple and sensitive platinum nanoparticles/poly（hydroxymethylated-3,4-ethylenedioxylthiophene） nanocomposite （PtNPs/PEDOT-MeOH） modified glassy carbon electrode （GCE） was successfully developed for the electrochemical determination of quercetin. Scanning electron microscopy and energy dispersive X-ray spectroscopy results indicated that the PtNPs were inserted into the PEDOT- MeOH layer. Compared with the bare GCE and poly（3,4-ethylenedioxythiophene） （PEDOT） electrodes, the PtNPs/PEDOT-MeOH/GCE modified electrode exhibited a higher electrocatalytic ability toward the oxidation of quercetin due to the synergic effects of the electrocatalytic activity and strong adsorption ability of PtNPs together with the good water solubility and high conductivity of PEDOT-MeOH. The electrochemical sensor can be applied to the quantification of quercetin with a linear range covering 0.04-91μmol L-1 and a low detection limit of 5.2 nmol L-1. Furthermore, the modified electrode also exhibited good reoroducibilitv and long-term stability, as well as high selectivity.
A novel graphene oxide （GO） doped poly（hydroxymethylated-3,4-ethylenedioxythiophene） （PEDOTM） film has been achieved via one-step co-electrodeposition and utilized for electrochemical studies of indole-3-acetic acid （IAA）. The incorporation of GO into PEDOTM film facilitated the electrocatalytic activity and exhibited a favorable interaction between the PEDOTM/GO film and the phytohormone during the oxidation of IAA. Under optimized conditions, differential pulse voltammetry and square wave voltammetry were used for the quantitative analysis of IAA, respectively, each exhibiting a wide linearity range from 0.6 μmol L-1 to 10 μmol L-1 and 0.05 μmol L-1 to 40 μmol L-1, good sensitivity with a low detection Iimit of 0.087 μmol L-1 and 0.033μmol L T, respectively, as well as good stability. With the notable advantages of a green, sensitive method, expeditious response and facile operation, the as-prepared PEDOTM/GO organic-inorganic composite film provides a promising platform for electrochemical studies of IAA.
