The vitamin C（VC） in crops was successfully determined using ascorbate oxidase（AO） electrochemical biosensor based on the biocompatible poly（3,4-ethylenedioxythiophene）（PEDOT） matrices,which was easily prepared by one-step electrodeposition technique in ionic liquid microemulsions.The fabricated biosensor displayed excellent bioelectrocatalytic performance to the oxidation of VC,wide linear range,low detection limit,fast response time,good operational and storage stability,the good results of the determination of VC in vegetable crops indicated that the fabricated biosensor will be a good candidate for the physiological and biochemical studies of crops in near future.
Yang Ping WenLi Min LuDong LiMing LiuHao Hua HeJing KunXu
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.
The biocompatiable and low-toxic poly（thiophene-3-aeetic acid） （PTAA） matrix was successfully electrosynthesized in ionic liquid 1-butyl-3-metbylimidazolium hexafluorophosphate （BmimPF6） in comparison with the electrosynthesis of PTAA matrix in acetonitrile （ACN）. Ascorbate oxidase （AO） was used as a model for the development and application of biosensor. Vitamin C （VC） biosensors were facilely fabricated by the covalent immobilization of AO molecules on PTAA matrices electrosynthesized in ACN containing tetrabutylammonium tetrafluoroborate and BmimPF6, respectively. Electrochemical impedance spectroscopy, scanning electron microscopy and FTIR spectroscopy indicated that AO molecules were covalently immobilized on PTAA matrices. Parameters of the as-obtained biosensors such as working potential, pH and temperature have been optimized. The amperometric biosensor based on PTAA matrix electrosynthesized in BmimPF6 exhibited wider linear range, lower detection limit, higher sensitivity and bioaffinity, and better operational and storage stability than that electrosynthesized in ACN under optimal conditions. The as-obtained biosensor based on PTAA matrix electrosynthesized in BmimPF6 was employed for the detection of VC content in comme：rcial juices, and the result was close to the data given by manufacturers. Excellent results indicate that the PTAA matrix electrosynthesized in ionic liquid is a promising platform for the covalent immobilization of biologically-active species and the development of biosensors.
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 promising electrochemical sensor was fabricated by electrodeposition of Pd nanoparticles （PdNPs） on poly（thiophene-3-acetic acid） （PTAA）-modified glassy carbon electrode （GCE）, forming a PdNPs/PTAA composites-modified GCE （PdNPs/PTAA/GCE）. Scanning electron microscope （SEM） and electrochemical techniques were used for the characterization of these composites. It was found that the PdNPs/PTAA layer was very uniform. ]Electrochemical experiments showed that this proposed PdNPs/PTAA composites-modified electrode exhibited excellent electrocatalytic activity towards the oxidation of hydrazine. Under the optimum conditions, the proposed sensor can be applied to the quantification of hydrazine with a wide linear range from 8.0 × 10-9 mol/L to 1.0 × 10-5 mol/L with a low detection limit of 2.67 × 10-9 mol/L. The experiment results also showed that the sensor exhibited good reproducibility and long-term stability, as well as high selectivity with no interference from other potential competing species.
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 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 ofrutin 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 p.mol/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.
Corrosion protection of the hull steel by the conventional epoxy paint containing a small amount of commercial poly（3,4-ethylenedioxythiophene）/poly（styrene sulfonate） （PEDOT/PSS）, which is one of the most popular and successful inherently conducting polymers as the corrosion inhibitor was studied. The corrosion behavior of the samples was investigated in seawater by electrochemical impedance spectroscopy and open circuit potential. Scanning electron microscopy was used to observe the surface morphology of the samples after corrosion. It was found that adding a small amount of PEDOT/PSS to the epoxy resin can significantly improve its corrosion protection.
