Liqi Dong

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.

Synthesis and characterization of chiral PEDOT enantiomers bearing chiral moieties in side chains: chiral recognition and its mechanism using electrochemical sensing technology

In this work, we present a pair of chiral PEDOT derivatives named poly((R)-2-(chloromethyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine) ((R)-PEDTC) and poly((S)-2-(chloromethyl)-2,3-dihydrothieno[3,4-b][1,4]dioxine) ((S)-PEDTC), which were employed as excellent chiral recognition materials for fabricating chiral sensors and then discriminating between 3,4-dihydroxyphenylalanine (DOPA) enantiomers. Importantly, the mechanism of the stereospecificity of the interaction between the DOPA enantiomers and chiral polymers was discussed specifically. A series of performances of corresponding polymers were characterized in some detail using different strategies including CV, CD, FT-IR, UV-vis, SEM, and TG. The CD spectrum indicated that (R)-PEDTC and (S)-PEDTC are mirror symmetric. CV shows that the polymers had superior redox reversibility in CH3CN–Bu4NPF6. Finally, different electrochemical methods including CV, square wave voltammetry (SWV) and differential pulse voltammetry (DPV) were introduced for the discrimination of DOPA enantiomers. Satisfactory measurement results demonstrated that (R)-PEDTC/GCE and (S)-PEDTC/GCE exhibited excellent enantioselectivity of DOPA enantiomers and the tendency was for anisotropic interaction between (R)-PEDTC and L-DOPA, and (S)-PEDTC and D-DOPA. This implied that the obtained polymer films could be promising candidates as enantioselective materials in the electrochemical sensor field.

Synthesis and characterization of D-/L-methionine grafted PEDOTs for selective recognition of 3,4-dihydroxyphenylalanine enantiomers

Two pairs of amino-acid functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, namely, poly(N-(tert-butoxycarbonyl)-L-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (L-PEDOT-Boc-Met) and poly(N-(tert-butoxycarbonyl)-D-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (D-PEDOT-Boc-Met); poly(L-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (L-PEDOT-Met) and poly(D-methionyl (3,4-ethylenedioxythiophene-2’-yl)methylamide) (D-PEDOT-Met) were synthesized via chemical oxidative polymerization of corresponding monomers. The structural characterization, spectroscopic properties and thermal stability of these monomers and polymers were systematically explored by FTIR spectra, Raman spectra, XRD spectra, UV-Vis spectra and thermogravimetric analysis. As chiral electrode materials, these polymers were employed to successfully recognize 3,4-dihydroxyphenylalanine (DOPA) enantiomers by cyclic voltammetry (CV) in sulphuric acid solution. The measurement results reveal that the tendency was hetero-chiral interaction between L-PEDOT-Met/PVA/GCE and D-DOPA, D-PEDOT-Met/PVA/GCE and L-DOPA, respectively. Also, the mechanism of chiral discrimination was discussed. All the results implied that the combination of electrochemical molecular recognition technology and chiral PEDOT materials can be a promising approach for chiral recognition and may open new opportunities for facile, biocompatible, sensitive and robust chiral assays in biochemical applications.

Preparation and characterization of poly(2′-aminomethyl-3,4-ethylenedioxythiophene) by chemical oxidative polymerization

Poly(2′-aminomethyl-3,4-ethylenedioxythiophene) was synthesized by the chemical oxidative polymerization of 2′-aminomethyl-3,4-ethylenedioxythiophene in the presence of different oxidants, such as FeCl3, Ce(SO4)2, (NH4)2Ce(NO3)6, and (NH4)2S2O8. The as-formed polymer was investigated by FTIR, UV–Vis, and Raman spectroscopy, fluorescence, thermogravimetry, and X-ray diffraction to determine the structure, photophysical properties, thermal stability, and polymer phase. FTIR and Raman spectra measurements indicated that the formation of macromolecules occurred exclusively via α,α-coupling of thiophene rings. Moreover, polymer obtained in polymerization using Ce(SO4)2 as the oxidant displayed superior thermal stability. All the characterizations indicated that FeCl3 was the more suitable oxidant for oxidative polymerization of the monomer and provided formation of polymer with higher yield.

Facile fabrication of three-dimensional graphene microspheres using β-cyclodextrin aggregates as substrates and their application for midecamycin sensing

Three-dimensional (3D) graphene (GR) microspheres have been successfully prepared for the first time using a simple, easy and green method using β-cyclodextrin aggregates (β-CDAs) as substrates, which could be easily obtained from concentrated aqueous solutions of β-CD. The 3D GR/β-CDAs composites synthesized were characterized using scanning electron microscopy, transmission electron microscopy, ultraviolet/visible spectroscopy, and Raman spectroscopy. A possible formation mechanism was derived. The as-prepared 3D GR/β-CDAs microspheres provided multidimensional electron transport pathways, and this has been exploited in an electrode material for the electrocatalytic oxidation of midecamycin (MD), a widely used macrolide antibiotic. Electrochemical results indicated that the as-prepared 3D GR/β-CDAs microspheres exhibited a higher electrocatalytic activity towards MD oxidation than two-dimensional (2D) GR or β-CDAs, which could be mainly attributed to the improved electrical properties and large surface area of the composite and the high recognition and enrichment capability of β-CDAs. Under optimal conditions, the peak currents on a 3D GR/β-CDA microsphere modified electrode increased linearly with the concentration of MD in the range 0.07–250 μM. The detection limit of MD reached 20 nM (S/N = 3). The present method is promising for the synthesis of high-performance catalysts for sensors, fuel cells and gas-phase catalysis.