Journal of the Electrochemical Society

A graphene-supported Pd–Ag bimetallic alloy catalyst for rapid detection of low concentrations of chlorophenols (CPs) in environmental monitoring was prepared by wet chemical reduction. The catalyst was used to construct an electrochemical CP sensor. Catalyst-modified glassy carbon electrodes were evaluated for the determination of aqueous CP contaminants, i.e., 4-chlorophenol (4-CP), 3-chlorophenol (3-CP), 2-chlorophenol (2-CP), and 2,4-dichlorophenol (2,4-DCP), at low concentrations. Synergies between the Pd–Ag bimetallic alloy component and the graphene component of the electrochemical catalyst significantly affected the electrochemical reactions of the CPs, by enhancing the electron transfer rate and the electrochemical oxidation–reduction reaction efficiency. The optimal experimental conditions for a Pd0.5Ag0.5/reduced graphene oxide-modified electrode sensor were 0.1 mol/L phosphate-buffered saline, a scan rate of 100 mV/s, and pH 7. The detection ranges for the monochlorophenols (4-CP, 3-CP, and 2-CP) were wide, namely 0.1–80, 0.1–100, and 0.1–80 μmol/L, respectively. The dichlorophenol (2,4-DCP) detection range was broader, i.e., 0.002–100 μmol/L. The detection limits were low, namely 0.0075, 0.0077, 0.0047, and 0.00036 μmol/L (S/N = 3), respectively. These electrode sensors give good accuracy and reproducibility, and high recovery rates (almost 100%). They have anti-interference properties and long-term stability. The results indicate that such sensors could be used for detection of low concentrations of CPs in wastewater, and have good potential for use in practical applications.

Published in: "Journal of the Electrochemical Society".

How to fabricate a stable and efficient systems for enantiomers discrimination has drawn enormous attention from researchers. Herein, our group presented a novel, convenient and fast electrochemical chiral sensor for chiral recognition based on a regular self-assembly micro-nano structure by sodium carboxymethyl cellulose (CMC) covalently functionalized reduced graphene oxide (rGO) with ethylenediamine (EDA) as a linker (rGO-EDA-CMC (2)), which successfully solved the agglomeration of sodium CMC. Also, the effect of preparation temperature for rGO-EDA-CMC (2) and the extent of amide formation among GO, CMC and EDA were investigated. The regular self-assembly micro-nano structure of rGO-EDA-CMC (2) with a large number of chiral microenvironments, which is meaningful for construction of electrochemical chiral sensor for enantiorecognition of Tryptophan (Trp) enantiomers based on three-point force, which exhibits excellent affinity for D-Trp by optimizing the interaction temperature, contact time and pH between Trp enantiomers and chiral interfaces. Further research drew conclusions that the percentage of D-Trp exhibits a fine linear relationship in Trp racemic mixtures. The proposed electrochemical chiral sensor is the first example to exploring a regular micro-nano structure material with sodium carboxymethyl cellulose self-assembly for electrochemical enantiorecognition of chiral compounds.

Published in: "Journal of the Electrochemical Society".

Reduced graphene oxide-nanocrystals has attracted considerable attention since it has great potential due to its great chemical activity, high mechanical stability and excellent electrical properties. But the synthesis of reduced graphene oxide-nanocrystals still faces challenges, for example introduce of RGO would contribute to change the morphology of nanocrystals. To address the challenge, we designed a simple method to prepare the common composite material and it was successfully adopted to fabricate glucose sensor with higher catalytic activity. Under the optimal conditions, the experimental results indicated that RGO-Pd NCs@CuO/GC electrode showed excellent electrocatalysis for glucose oxidation with a lower detection limit of 10 nM. This sensor was of excellent stability and sensitivity. This study not only provides a new sensor for selective and reliable detection of glucose but also offers a common and facile strategy for syntheses of nanocrystals supported on reduced graphene oxide.

Published in: "Journal of the Electrochemical Society".

As a binder for the stabilization and dispersion of CoNi nanoparticles (NPs), ionic liquids (IL) were designed to connect inorganic anion on IL-functionalized reduced graphene oxide (rGO) and metal cation. The CoNi/IL-rGO described excellent oxygen reduction reaction (ORR) and the selective adsorption of bimetallic CoNi for chlorophene hydrodechlorination (HDC). The prepared electrocatalyst was characterized by SEM, TEM, XPS, Raman spectroscopy, XRD, and UV–vis spectroscopy. Results indicated that ILs could be functionalized by – stacking on the rGO surface. The optimal bimetallic CoNi NPs (Co-to-Ni weight ratio of 2.5:2.5) with small particles sizes (3.33 ± 0.03 nm) were uniformly dispersed on the surface of IL-rGO (mass ratio of IL:GO was 2:1) among a series of as-prepared catalysts. The IL on the rGO surface could prevent rGO agglomeration and provide sufficient binding sites to anchor the CoNi NPs via electrostatic interaction. Co(2.5)Ni(2.5)/IL(2)-rGO demonstrated low impedance (7.5 ) and diffusion resistance due to the introduction of IL. Co(2.5)Ni(2.5)/IL(2)-rGO exhibited a high peak current (–0.35 mA), preferred two-electron selectivity and high H2O2 productivity (>80%) toward ORR in an alkaline solution. The possible dechlorination mechanism of chlorophene was ascribed to the combination of adsorbed hydrogen on Co and adsorbed chlorophene on Ni.

Published in: "Journal of the Electrochemical Society".

A sensitive and simple electrochemical sensor for determination of norepinephrine (NE) was developed. The electrode (ERG-UiO-67-bpy/GCE) was fabricated by modifying the glassy carbon electrode with a Zr (IV) metal-organic framework (MOF) with 2,2′-bipyridyl-5,5′-dicarboxylate (UiO-67-bpy) and graphene oxide (GO), followed by electrochemical reduction of GO to ERG (electrochemically reduced graphene). The ERG and UiO-67-bpy components of the composite electrode show a synergic electrocatalytic effect, leading to much enhanced voltammetric response to the oxidation of NE. Comparative studies indicate that the hydrogen bonds between the bipyridyl moiety of the MOF and the 2-aminoethanol moiety of NE play an important role in promoting electron transfer on the electrode surface. Differential pulse voltammetry using the composite electrode shows a wide linear-response concentration range with a submicromolar detection limit of 0.026 μM. The sensor shows good reproducibility and stability and also be used for sensitive simultaneous detection of NE and uric acid.

Published in: "Journal of the Electrochemical Society".