Tianrong Zhan

Electrochemical sensor for bisphenol A based on ionic liquid functionalized Zn-Al layered double hydroxide modified electrode

The plate-like Zn-Al layered double hydroxide modified with 1-aminopropyl-3-methylimidzaolium tetrafluoroborate (named as ILs-LDH) was synthesized by coprecipitation method. Several techniques confirmed the layered structure of ILs-LDH with a disk-like morphology. A novel electrochemical sensor based on ILs-LDH modified glass carbon electrode (GCE) was developed for bisphenol A (BPA) determination. Experimental factors including modified content, pH, scan rate, accumulation time and potential had been carefully optimized. ILs-LDH/GCE performed the excellent electro-oxidation ability toward BPA with the more negative oxidation overpotential and larger peak current than bare GCE or LDH/GCE. Differential pulse voltammetry determination of BPA afforded a wider linear range from 0.02 to 3μM with the detection limit of 4.6nM (S/N=3). The fabricated sensor demonstrated an acceptable reproducibility, good stability and high sensitivity. The proposed method was successfully used to detect BPA in real water samples with satisfactory recovery ranging from 94.9% to 102.0%.

Structural characterization and electrocatalytic application of hemoglobin immobilized in layered double hydroxides modified with hydroxyl functionalized ionic liquid

Hemoglobin (Hb) was immobilized in Zn2Al-Layered Double Hydroxides (LDH) modified with Hydroxyl Functionalized Ionic Liquid (HFIL) through adsorption and coprecipitation method, respectively. Adsorption experiments showed that the presence of HFIL could enhance the maximum protein loading. However, the Hb loading through coprecipitation technique was far higher than that for adsorption. The role of HFIL on the interaction between Hb and LDH was investigated by XRD, FTIR, UV-vis and fluorescence spectroscopies. Although the quaternary structure of Hb entrapped in HFIL-LDH through coprecipitation technique (denoted as HFIL-LDH-Hbcop) might be altered slightly more than that in LDH (LDH-Hbcop), its secondary structure and redox-active heme groups kept intact. Morphologies of LDH-Hbcop and HFIL-LDH-Hbcop biohybrids were analyzed through SEM and TEM images. The direct electrochemistry of the immobilized Hb indicated that the coprecipitation bioelectrode performed better than that of the corresponding adsorption one. Regardless of adsorption and coprecipitation, the introduction of HFIL could distinctly promote the electron transport. Among all bioelectrodes, HFIL-LDH-Hbcop/GCE displayed the best electrocatalytic activity for H2O2 determination with a larger electroactive Hb percentage (6.76%), higher sensitivity (40.63A/Mcm(2)) and lower detection limit (0.0054μmol/L). So HFIL-LDH could effectively immobilize enzymes via coprecipitation technique, which had potential applications in the fabrication of electrochemical biosensors.

Ionic liquid microemulsions of 1-butyl-3-methylimidazolium hexafluorophosphate, N,N-dimethylformamide, and water

The phase behavior of a ternary system consisting of the hydrophobic ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), N,N-dimethylformamide, and water was investigated. Single-phase microemulsion and multiphase regions were observed in the ternary phase diagram. To the best of our knowledge, this is the first report of aqueous IL microemulsions prepared in the absence of traditional surfactants, i.e., surfactant-free microemulsions (SFMEs) containing IL. The microstructures and structural transitions of the aqueous IL SFMEs were investigated using cyclic voltammetry, electrical conductivity, and dynamic laser light scattering techniques. The results showed that the aqueous IL SFMEs exhibit IL-in-water, bicontinuous, and water-in-IL microstructures, similar to the case of traditional surfactant-based microemulsions. The three kinds of microstructures were confirmed from freeze-fracture electron microscopy observations. Ultraviolet-visible and fluorescence spectroscopies were used to examine the polarities of microdomains in the microemulsions, using methyl orange and pyrene, respectively, as probes. It was found that these two techniques can be used to identify the microstructures and microstructural transitions of the aqueous IL microemulsions.