Synthesis and electrochemical properties of environmental free l-glutathione grafted graphene oxide/ZnO nanocomposite for highly selective piroxicam sensing.

A simple and reliable strategy was proposed to engineer the glutathione grafted graphene oxide/ZnO nanocomposite (glutathione-GO/ZnO) as electrode material for the high-performance piroxicam sensor. The prepared glutathione-GO/ZnO nanocomposite was well characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). The novel nanocomposite modified electrode showed the highest electrocatalytic activity towards piroxicam (oxidation potential is 0.52 V). Under controlled experimental parameters, the proposed sensor exhibited good linear responses to piroxicam concentrations ranging from 0.1 to 500 µM. The detection limit and sensitivity were calculated as 1.8 nM and 0.2 µA/µM·cm2, respectively. Moreover, it offered excellent selectivity, reproducibility, and long-term stability and can effectively ignore the interfering candidates commonly existing in the pharmaceutical tablets and human fluids even at a higher concentration. Finally, the reported sensor was successfully employed to the direct determination of piroxicam in practical samples.

Synthesis and electrochemical properties of environmental free L-glutathione grafted graphene oxide/ZnO nanocomposite for highly selective piroxicam sensing / 药物分析学报

A simple and reliable strategy was proposed to engineer the glutathione grafted graphene oxide/ZnO nanocomposite(glutathione-GO/ZnO)as electrode material for the high-performance piroxicam sensor.The prepared glutathione-GO/ZnO nanocomposite was well characterized by X-ray diffraction(XRD),Fourier transform infrared spectrum(FTIR),X-ray photoelectron spectroscopy(XPS),field emission scanning electron microscopy(FE-SEM),cyclic voltammetry(CV),electrochemical impedance spectros-copy(EIS)and differential pulse voltammetry(DPV).The novel nanocomposite modified electrode showed the highest electrocatalytic activity towards piroxicam(oxidation potential is 0.52 V).Under controlled experimental parameters,the proposed sensor exhibited good linear responses to piroxicam concentrations ranging from 0.1 to 500 μM.The detection limit and sensitivity were calculated as 1.8 nM and 0.2 μA/μM·cm2,respectively.Moreover,it offered excellent selectivity,reproducibility,and long-term stability and can effectively ignore the interfering candidates commonly existing in the pharmaceutical tablets and human fluids even at a higher concentration.Finally,the reported sensor was successfully employed to the direct determination of piroxicam in practical samples.

Synchronous detection of cadmium and lead in honey, cocos nucifera and egg white samples using multiwalled carbon nanotube/hyaluronic acid/amino acids nanocomposites.

Electrochemical Synchronous detection of cadmium (Cd(II)) and lead (Pb(II)) was obtained by acid treated multiwalled carbon nanotube (A-MWCNT) functionalized with hyaluronic acid (Hyalu) and this mixture was separately further modified with l-cysteine (l-Cys) and l-serine (l-Ser). Under the optimized circumstance best voltammetric responses were produced by A-MWCNT/Hyalu/l-Cys and A-MWCNT/Hyalu/l-Ser modified electrodes. The peak current was linearly dependent on the Cd(II) and Pb(II) concentrations in the range from 0.4 to 4 µg L-1. The sensitivities were calculated as 0.7 µA/nM (Cd(II)) and 3.5 µA/nM (Pb(II)) for A-MWCNT/Hyalu/l-Cys/GCE and 0.6 µA/nM (Cd(II)) and 2.6 µA/nM (Pb(II)) for A-MWCNT/Hyalu/l-Ser/GCE. From the calibration plot LODs were calculated to be 0.032 µg L-1 (Cd(II)) and 0.015 µg L-1 (Pb(II)) for A-MWCNT/Hyalu/l-Cys/GCE and 0.057 µg L-1 (Cd(II)) and 0.034 µg L-1 (Pb(II)) for A-MWCNT/Hyalu/l-Ser/GCE. Moreover, the proposed electrodes were subjected to the real sample application in honey, cocos nucifera and egg white.

Binary Mixture of Lanthanide Metal Doped ZnO Nanorod: f-MWCNT Nanocomposite for Simultaneous and Selective Determination of Vitamins B² and B6.

An electrochemical sensor using lanthanide element Gadolinium doped Zinc oxide and functionalized Multiwalled Carbon Nanotube (Gd-ZnO:f-MWCNT) fabricated electrode was presented for the simultaneous determination of vitamins (Riboflavin (VB2) and Pyridoxine (VB6)). The nanocomposite was characterized by FESEM, EDS, XRD and FTIR techniques. The CV, EIS and DPV techniques were used to evaluate the electrochemical properties of the nanocomposite. Under optimum conditions, the peak current of VB2 and VB6 are linearly proportional to its concentration in the range from 0.05 to 10 µM and the estimated detection limits were 0.009 and 0.001 µM for VB2 and VB6 respectively. The sensitivities calculated were 0.94 µA nM-1 cm-2 (VB2) and 1.43 µA nM-1 cm-2 (VB6). In addition, the proposed electrode was exhibited high selectivity, reproducibility, as well as long-term stability for the determination of vitamins. Finally, the vitamins contained in pharmaceutical formulation and commercial orange juice has been determined by the proposed sensor and the obtained results were validated with HPLC.

3D cloves bud like Gd doped ZnO strewn rGO hybrid for highly selective determination of l-dopa in the presence of carbidopa and ascorbic acid.

An electrochemical sensor using three dimensional (3D) cloves bud like gadolinium doped ZnO nanoflowers strewn reduced graphene oxide (GZO@rGO) modified glassy carbon electrode was proposed for the sensitive and selective detection of l-dopa. The GZO@rGO nanocomposite was synthesized by hydrothermal method and characterized by a variety of analytical and spectroscopy techniques, viz. Field Emission Scanning Electron Microscopy, X-Ray Diffraction, Fourier Transformed Infrared Spectrum and X-ray photoelectron spectroscopy. The electrochemical characterization was evaluated by Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Differential Pulse Voltammetry (DPV). The 3D cloves bud like GZO@rGO hybrid displayed the highest electro-catalytic behaviour for the selective l-dopa detection. Under optimum conditions, the oxidation current response of l-dopa is directly proportional to its concentration ranging from 10 to 100 nM. The sensitivity and limit of detection was calculated as 0.1 µA nM-1 cm-2 and 0.82 nM respectively. Moreover, the proposed electrode offers excellent selectivity, because it can efficiently evade the intervention of carbidopa and ascorbic acid even in the higher concentration. Thus, the reported sensor exhibits accurate determination of l-dopa (in the presence of carbidopa & ascorbic acid) and possesses an excellent real-time application with Mucuna prurita, pharmaceutical and human urine samples.

Ultra sensitive detection of Cd (II) using reduced graphene oxide/carboxymethyl cellulose/glutathione modified electrode.

The present work describes the electrochemical detection of Cd2+ using reduced graphene oxide (rGO), carboxymethyl cellulose (CMC) and glutathione (GSH) modified glassy carbon electrode (GCE) by Square Wave Anodic Stripping Voltammetry (SWASV). The prepared nanocomposite was characterized by X-ray diffraction (XRD), RAMAN, Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS), Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS). The influence of experimental parameters such as effect of pH, choice of supporting electrolyte, deposition time and deposition potential, were optimized. Under the optimized conditions, the linear relationship between the current intensity and Cd2+ concentration (2-20 nM) was I (µA) = -6.78 (c/nM) + 4.547 (R2 = 0.996). The detection limit and sensitivity achieved for the modified electrode were 0.05 nM and 4.5 µA/nM respectively. Finally, rGO/CMC/GSH/GCE was successfully demonstrated for the detection of Cd2+ in real samples, and the results were compared with AAS analysis.

A novel voltammetric sensor for the simultaneous detection of Cd2+ and Pb2+ using graphene oxide/κ-carrageenan/l-cysteine nanocomposite.

Simultaneous determination of Cd2+ and Pb2+ was achieved by using graphene oxide/κ-carrageenan/l-cysteine (GO/κ-Car/l-Cys) nanocomposite modified glassy carbon electrode (GCE) by Square Wave Anodic Stripping Voltammetry (SWASV). The morphology and functionalization of the prepared nanocomposite were characterized by XRD analysis, Raman spectroscopy, Field emission scanning electron microscopy and FTIR analysis. Under optimum conditions, outstanding linearity was obtained for both Cd2+ and Pb2+ in the range from 5 to 50nM with the detection limits as 0.58nM and 1.08nM respectively. The sensitivity calculated from the slope of calibration curve was 1.39µA/nM and 1.32µA/nM for Cd2+ and Pb2+ respectively. We also carried out multiple metal ion detection, interference of anions and surfactants for the detection of Cd2+ and Pb2+ ions. The modified electrode has been applied to the detection of Cd2+ and Pb2+ present in water and milk samples, and the accessed results were satisfactory with that of AAS.