Fabrication of ß-cyclodextrin-coated poly (diallyldimethylammonium chloride)-functionalized graphene composite film modified glassy carbon-rotating disk electrode and its application for simultaneous electrochemical determination colorants of sunset yellow and tartrazine.

We proposed a green and facile approach for the synthesis of ß-cyclodextrin-coated poly(diallyldimethylammonium chloride)-functionalized graphene composite film (ß-CD-PDDA-Gr) by using L-ascorbic acid (L-AA) as the reducing agent at room temperature. The ß-CD-PDDA-Gr composite film modified glassy carbon-rotating disk electrode (GC-RDE) was then developed for the sensitive simultaneous determination of two synthetic food colorants: sunset yellow (SY) and tartrazine (TT). By cyclic voltammetry (CV), the peak currents of SY and TT increased obviously on the developed electrochemical sensor. The kinetic parameters, such as diffusion coefficient D and standard heterogeneous rate constant kb, were estimated by linear sweep voltammetry (LSV). Under the optimal conditions, the differential pulse voltammetry (DPV) signals of SY and TT on the ß-CD-PDDA-Gr modified GC-RDE were significantly enhanced. The enhanced anodic peak currents represented the excellent analytical performance of simultaneous detection of SY and TT in the range of 5.0×10(-8) to 2.0×10(-5) mol L(-1), with a low limit of detection (LOD) of 1.25×10(-8) mol L(-1) for SY and 1.43×10(-8) mol L(-1) for TT (SN(-1)=3). This proposed method displayed outstanding selectivity, good stability and acceptable repeatability and reproducibility, and also has been used to simultaneously determine SY and TT in some commercial soft drinks with satisfactory results. The obtained results were compared to HPLC of analysis for those two colorants and no significant differences were found. By the treatment of the experimental data, the electrochemical reaction mechanisms of SY and TT both involved a one-electron-one-proton-transfer process.

Synthesis of PtAu bimetallic nanoparticles on graphene-carbon nanotube hybrid nanomaterials for nonenzymatic hydrogen peroxide sensor.

PtAu bimetallic nanoparticles (NPs) were successfully synthesized on graphene sheets-multi walled carbon nanotubes (G-CNTs) hybrid nanomaterials via a simple one-step chemical co-reduction method in ethylene glycol (EG)-water system. The nanocomposites (PtAu/G-CNTs) were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Then a sensitive nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated based on PtAu/G-CNTs nanocomposites modified glassy carbon electrode (GCE). The results of electrochemical experiments demonstrated that the sensor exhibited excellent electrocatalytic activity to the reduction of H2O2. The sensor displayed a fast amperometric response time of less than 4s with linear detection range from 2.0 to 8561 µM and a relatively low detection limit of 0.6 µM (S/N=3). In addition, the sensor also showed good selectivity for H2O2 detection, long-term stability and reproducibility.

Sensitive detection of acetaminophen based on Fe3O4 nanoparticles-coated poly(diallyldimethylammonium chloride)-functionalized graphene nanocomposite film.

An electrochemical sensor based on Fe(3)O(4) nanoparticles (NPs)-coated poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (Fe(3)O(4)-PDDA-G) nanocomposite was fabricated for sensitive detection of acetaminophen. The nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). The electrochemical behaviors of acetaminophen on Fe(3)O(4)-PDDA-G composite film modified glassy carbon electrode (GCE) were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results indicated that the incorporation of Fe(3)O(4) NPs with PDDA-G greatly enhanced the electrochemical response of acetaminophen. This fabricated sensor displayed excellent analytical performance for acetaminophen detection over a range from 0.1 to 100 µ mol L(-1) with a detection limit of 3.7×10(-8) mol L(-1) (S/N=3). The redox peaks of acetaminophen, dopamine (DA) and ascorbic acid (AA) can be well separated on the Fe(3)O(4)-PDDA-G/GCE. Moreover, the proposed electrochemical sensor also exhibited good reproducibility and stability, and has been used to detect acetaminophen in tablets with satisfactory results.

Study of phenol biodegradation using Bacillus amyloliquefaciens strain WJDB-1 immobilized in alginate-chitosan-alginate (ACA) microcapsules by electrochemical method.

An aerobic microorganism with an ability to utilize phenol as sole carbon and energy source was isolated from phenol-contaminated wastewater samples. The isolate was identified as Bacillus amyloliquefaciens strain WJDB-1 based on morphological, physiological, and biochemical characteristics, and 16S rDNA sequence analysis. Strain WJDB-1 immobilized in alginate-chitosan-alginate (ACA) microcapsules could degrade 200 mg/l phenol completely within 36 h. The concentration of phenol was determined using differential pulse voltammetry (DPV) at glassy carbon electrode (GCE) with a linear relationship between peak current and phenol concentration ranging from 2.0 to 20.0 mg/l. Cells immobilized in ACA microcapsules were found to be superior to the free suspended ones in terms of improving the tolerance to the environmental loadings. The optimal conditions to prepare microcapsules for achieving higher phenol degradation rate were investigated by changing the concentrations of sodium alginate, calcium chloride, and chitosan. Furthermore, the efficiency of phenol degradation was optimized by adjusting various processing parameters, such as the number of microcapsules, pH value, temperature, and the initial concentration of phenol. This microorganism has the potential for the efficient treatment of organic pollutants in wastewater.

Sensitive detection of esculetin based on a CdSe nanoparticles-decorated poly(diallyldimethylammonium chloride)-functionalized graphene nanocomposite film.

An electrochemical sensor based on a CdSe nanoparticles (NPs)-decorated poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene (CdSe-PDDA-G) nanocomposite was fabricated for the sensitive detection of esculetin. The nanocomposite was characterized by X-ray diffraction (XRD), ultraviolet/visible spectra (UV-vis) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to investigate the electrochemical behaviors of esculetin on the CdSe-PDDA-G composite film-modified glassy carbon electrode (GCE). The experimental results indicated that the incorporation of CdSe NPs with PDDA-G greatly enhanced the electrochemical response of esculetin. This electrochemical sensor displayed satisfactory analytical performance for esculetin detection over a range from 1.0 × 10(-8) to 5.0 × 10(-5) mol L(-1) with a detection limit of 4.0 × 10(-9) mol L(-1) (S/N = 3). Moreover, the sensor also exhibited good reproducibility and stability, and could be used for the detection of esculetin in real samples with satisfactory results.