Electrochemically reduced graphene oxide with enhanced electrocatalytic activity toward tetracycline detection

An electrochemically reduced graphene oxide sample, ERGO_0.8v, was prepared by electrochemical reduction of graphene oxide （GO） at -0.8 V, which shows unique electrocatalytic activity toward tetracycline （TTC） detection compared to the ERGO-12v （GO applied to a negative potential of-1.2 V）, GO, chemically reduced GO （CRGO）-modified glassy carbon electrode （GC） and bare GC electrodes. The redox peaks of TTC on an ERGO-0.8v-modifled glass carbon electrode （GC/ERGO-0.8v） were within 0-0.5 V in a pH 3.0 buffer solution with the oxidation peak current correlating well with TTC concentration over a wide range from 0.1 to 160 mg/L Physical characterizations with Fourier transform infrared （FT-IR）, Raman, and X-ray photoelectron spectroscopies （XPS） demonstrated that the oxygen-containing functional groups on GO diminished after the electrochemical reduction at -0.8 V, yet still existed in large amounts, and the defect density changed as new sp2 domains were formed. These changes demonstrated that this adjustment in the number of oxygen-containing groups might be the main factor affecting the electrocatalytic behavior of ERGO. Additionally, the defect density and sp2 domains also exert a profound influence on this behavior. A possible mechanism for the TTC redox reaction at the GC/ERGO-0.8v electrode is also presented. This work suggests that the electrochemical reduction is an effective method to establish new catalytic activities of GO by setting appropriate parameters.

The pharmacokinetic study of rutin in rat plasma based on an electrochemically reduced graphene oxide modified sensor

An electrochemical method based on a directly electrochemically reduced graphene oxide （ERGO） film coated on a glassy carbon electrode （GCE） was developed for the rapid and convenient determination of rutin in plasma. ERGO was modified on the surface of GCE by one-step electro-deposition method. Electrochemical behavior of rutin on ERGO/GCE indicated that rutin underwent a surface-controlled quasi-reversible process and the electrochemical parameters such as charge transfer coefficient （α）, electron transfer number （n） and electrode reaction standard rate constant （ks） were 0.53, 2 and 3.4 s -1, respectively. The electrochemical sensor for rutin in plasma provided a wide linear response range of 4.70 × 10 ^-7 1.25 × 10^-5 M with the detection limit （s/n=3） of 1.84 × 10^-8 M. The assay was success- fully used to the pharmacokinetic study of rutin. The pharmacokinetic parameters such as elimination rate half-life （t1/2）, area under curve （AUC）, and plasma clearance （CL） were calculated to be 3.345 ± 0.647 rain, 5750 ±656.0 μg min/mL, and 5.891± 0.458 mL/min/kg, respectively. The proposed method utilized a small sample volume of 10 μL and had no complicated sample pretreatment （without deproteinization）, which was simple, eco-friendly, and time- and cost-efficient for rutin pharmacokinetic studies.

High-performance asymmetric supercapacitors based on reduced graphene oxide/polyaniline composite electrodes with sandwich-like structure

The sandwich-like structure of reduced graphene oxide/polyaniline （RGO/PANI） hybrid electrode was prepared by electrochemical deposition. Both the voltage windows and electrolytes for electrochemical deposition of PANI and RGO were optimized. In the composites, PANI nanofibers were anchored on the surface of the RGO sheets, which avoids the re-stacking of neighboring sheets. The R（;O/PANI composite electrode shows a high specific capacitance of 466 F/g at 2 mA/cm2 than that of previously reported RGO/PANI composites. Asymmetric flexible supercapacitors applying RGO/PANI as positive electrode and carbon fiber cloth as negative electrode can be cycled reversibly in the high-voltage region of 0-1.6 V and displays intriguing performance with a maximum specific capacitance of 35.5 mF cm^-2. Also, it delivers a high energy density of 45.5 mW h cm^-2 at power density of 1250 mW cm^-2. Furthermore, the asymmetric device exhibits an excellent long cycle life with 97.6Z initial capacitance retention after 5000 cycles. Such composite electrode has a great potential for applications in flexible electronics, roll-up display, and wearable devices.2017 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science ＆ Technology.

Electrodeposition of Prussian Blue Nanoparticles on Electro- chemically Reduced Graphene Oxide and Synergistically Elec- trocatalytic Activity toward Guanine

In this paper, a simple and reliable fabrication method about electrochemically reduced graphene oxide （ERGNO）-prussian blue （PB） nanocomposite was proposed for determination of guanine. Due to its unique struc- tural, physical and chemical properties, ERGNO, which was fabricated on the carbon paste electrode （CPE） before- hand through electrochemical reduction of graphene oxide, was selected as a compatible precursor for next-step PB electrodeposition. Electrochemical behaviors of the resulted PB/ERGNO/CPE were investigated by electrochemical impedance spectroscopy （EIS）, cyclic voltammetry （CV） and differential pulse voltammetry （DPV）. The electro- chemical results showed that PB/ERGNO/CPE exhibited good electrochemical performances. The electrocatalytic results of guanine further illustrated that graphene prompted the electrocatalytie ability of PB via the redox shift between PB and prussian yellow （PY） in the potential range from 0.5 to 1.2 V, which has not been widely adopted in the PB based electrochemical sensors. The detection limit of guanine could be calculated to be 1.0 × 10^-8 mol/L. It means this PB/ERGNO/CPE platform is quite sensitive and can be readily applied in biosensor field.

Electrochemical Detection of Superoxide Anion Released by Living Cells by Manganese(Ⅲ) Tetraphenyl Porphine as Superoxide Dismutase Mimic

Superoxide anion,one of the most active reactive oxygen species,is associated with the development of many diseases.So monitoring superoxide anion in living cells is of great significance for the pathological research of many diseases.In this work,a new non-enzymatic sensor tor the detection of superoxide anion(O^·-2)was developed,which was iabricated by the nanocomposites composed of manganese(Ⅲ)tetraphenyl porphine(MnTPP)as superoxide dismutase mimic and electrochemical reduced graphene oxide(ERGO)as electrode support material to modify the glassy carbon electrode(GCE).The electrochemical behavior of the fabricated electrode(MiiTPP/ERGO/GCE)was performed by electrochemical impedance spectroscopy(EIS)and cyclic voltammetry(CV),which revealed that MnTPP/ERGO/GCE possessed good catalytic ability to theelectrochemical reduction of O^·-2.The MnTPP/ERGO/GCE showed excellent electroanalysis perfonnance towards O^·-2 using the technique of diflerential pulse voltanimetry(DPV)with a linear relationship in the range of 0.2—110.0μmol/L,a sensitivity of 445 μA· L·mmol^-1·cm^- 2 and a detection limit of 0.039 μmol/L(S/N=3).The real-time monitoring of O^·-2 from MCF-7 breast cancer cells stimulated by zymosan was realized in this work,which indicates that the MnTPP/ERGO/GCE hold potential application for electrochemical quantification of superoxide anions in biological applications.

CuS/RGO hybrid by one-pot hydrothermal method for efficient electrochemical sensing of hydrogen peroxide

In this study,a non-enzymatic hydrogen peroxide sensor was successfully fabricated on the basis of copper sulfide nanoparticles/reduced graphene oxide（CuS/RGO） electrocatalyst.Using thiourea as reducing agent and sulfur donor,CuS/RGO hybrid was synthesized through a facile one-pot hydrothermal method,where the reduction of GO and deposition of CuS nanoparticles on RGO occur simultaneously.The results confirmed that the CuS/RGO hybrid helps to prevent the aggregation of CuS nanoparticles.Electrochemical investigation showed that the as-prepared hydrogen peroxide sensor exhibited a low detection limit of 0.18μmol/L（S/N = 3）,a good reproducibility（relative standard deviation（RSD） of4.21%）,a wide linear range（from 3 to 1215 μmol/L） with a sensitivity of 216.9 μA L/mmol/cm-2 under the optimal conditions.Moreover,the as-prepared sensor also showed excellent selectivity and stability for hydrogen peroxide detection.The excellent performance of CuS/RGO hybrid,especially the lower detection limit than certain enzymes and noble metal nanomaterials ever reported,makes it a promising candidate for non-enzymatic H2O2 sensors.