Sensitive determination of metronidazole based on Graphene-TiO2 modified glassy carbon electrode in human serum and urine samples

In the present work, a new Graphene-TiO2 (GR-TiO2) modified glassy carbon electrode (GCE) is suggested for sensitive electrochemical determination of metronidazole (MTZ). Electrochemical studies revealed that GR-TiO2 nanoparticles increased the efficiency of electron transfer kinetics by increasing the available surface area of the electrode and charge mobility between MTZ and GR-TiO2 modified electrode. Compared to bare GCE, the modified electrode greatly enhanced the reduction signal of MTZ. The electrochemical behaviour of the modified electrode and the electrochemical reduction of MTZ were investigated with electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry techniques. The charge transfer coefficient (α) was calculated to be 0.694. Under optimized conditions, the linear concentration range and detection limit of MTZ were 5.0×10-7 to 2.5×10-5 M-1 and 5.4×10-8 (S/N = 3), respectively. Finally, this sensing method was successfully applied for the determination of MTZ in human blood serum and urine samples. 

Polyaniline–multi-wall-carbon nanotube nanocomposites as a dopamine sensor

A composite of polyaniline with multi-wall-carbon nanotubes (PANi/ /MWCNTs) was synthesized by an in situ chemical oxidative polymerization method. The PANi nanoparticles were synthesized chemically using aniline as the monomer and ammonium peroxydisulfate as the oxidant. The nanocomposites were prepared as a carbon paste using functionalized MWCNTs and PANi nanoparticles. The PANi–MWCNTs were characterized physically using scanning electron microscopy (SEM) and the electrochemical behavior of the composites in acidic solution (HCl) was investigated using cyclic voltammetry. The PANi/MWCNT composite electrode was used for studying dopamine (DA) as an electroactive material. The cyclic voltammetric results indicated that multi-wall carbon nanotubes (MWCNTs) significantly enhanced the electrocatalytic activity in favor of the oxidation of DA. The kinetics of the catalytic reaction was investigated using the chronoamperometry technique whereby the average va¬lue of the diffusion coefficient (D) and the catalytic rate constant (k) for DA were determined to be (7.98±0.8)×10-7 cm2 s-1 and (8.33±0.072)×104 dm3 mol-1 s-1, respectively

Original scientific paper Polyaniline–multi-wall-carbon nanotube nanocomposites as a dopamine sensor

Abstract: A composite of polyaniline with multi-wall-carbon nanotubes (PANi/ /MWCNTs) was synthesized by an in situ chemical oxidative polymerization method. The PANi nanoparticles were synthesized chemically using aniline as the monomer and ammonium peroxydisulfate as the oxidant. The nanocomposites were prepared as a carbon paste using functionalized MWCNTs and PANi nanoparticles. The PANi–MWCNTs were characterized physically using scanning electron microscopy (SEM) and the electrochemical behavior of the composites in acidic solution (HCl) was investigated using cyclic voltammetry. The PANi/MWCNT composite electrode was used for studying dopamine (DA) as an electroactive material. The cyclic voltammetric results indicated that multi-wall carbon nanotubes (MWCNTs) significantly enhanced the electrocatalytic activity in favor of the oxidation of DA. The kinetics of the catalytic reaction was investigated using the chronoamperometry technique whereby the average value of the diffusion coefficient (D) and the catalytic rate constant (k) for DA were determined to be (7.98±0.8)×10-7 cm 2 s-1 and (8.33±0.072)×10 4 dm 3 mol-1 s-1, respectively

Silver nanoparticles as a cyanide colorimetric sensor in aqueous media

The interaction between aqueous colloidal silver nanoparticles (AgNPs) and cyanide ions was studied using UV-Vis absorption and scanning electron microscopy (SEM) techniques. It was found that AgNPs were oxidized by dissolved oxygen in the presence of cyanide ions, resulting in a considerable decrease in the intensity of the surface plasmon resonance (SPR) absorption band of AgNPs. So, we propose a simple, cost effective, rapid, sensitive and selective colorimetric sensor for the detection of cyanide using AgNPs in aqueous media. There is a linear relationship between the absorbance intensity of AgNPs and the concentration of cyanide ions over the range of 16.7 mu mol L-1-133.3 mu mol L-1 at 394 nm. The proposed method has been successfully used for the determination of cyanide in water samples

Amperometric biosensor for cholesterol based on novel nanocomposite array gold nanoparticles/acetone-extracted propolis/multiwall carbon nanotubes/gold

In this reported work, the electrochemical behaviour of gold electrodes modified with gold nanoparticles, acetone-extracted propolis, multiwall carbon nanotubes and cholesterol oxidase was established for the detection of hydrogen peroxide by using cyclic voltammetry and amperometric techniques. The obtained results confirmed that the current enzymatic biosensor exhibits a fast, highly sensitive, and cost-effective detection of cholesterol. Cholesterol in the concentration range of 0.15-0.55 mmol l(-1) was determined with a detection limit of 4.9 x 10(-5) mol l(-1) by the amperometric method, and the sensitivity of the proposed method was found to be 17.38 mu A/mmol l(-1). Normal electroactive species such as ascorbic acid and glucose in the presence of the constant concentration of cholesterol in the samples do not interfere with the determination

The AgcorePdshell bimetallic nanoparticles: simple biological synthesis and characterization

In this work and for the first time, bimetallic Ag-Pd nanoparticles equipped with a core-shell structure were prepared biologically by employing a galvanic displacement reaction in which the added PdCl2 reacts with an Ag nanotemplate containing an adsorbed soaproot (Acanthe phylum bracteatum) extract. Four samples with different Ag/Pd molar ratios of 100:2, 100:5, 100:10 and 100:15 were prepared to synthesize the bimetallic nanoparticles with a core-shell structure. The bimetallic Ag-Pd nanoparticles were characterized using UV-visible spectroscopy (UV-Vis), X-ray diffraction (XRD), scanning electron microscopy with an energy-dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) analysis. The results from UV-Vis revealed an optimal molar ratio of 100:15 for Ag/Pd, which is appropriate to prepare bimetallic Ag-Pd nanoparticles with the core-shell structure. The results of FTIR and XRD confirmed the pure bimetallic Ag-Pd nanoparticles formation. The images prepared by TEM depicted spherical and uniformly shaped nanoparticles without any agglomeration and a particle size of 15 nm

Amperometric biosensor for cholesterol based on novel nanocomposite array gold nanoparticles/acetone‐extracted propolis/multiwall carbon nanotubes/gold

In this reported work, the electrochemical behaviour of gold electrodes modified with gold nanoparticles, acetone-extracted propolis, multiwall carbon nanotubes and cholesterol oxidase was established for the detection of hydrogen peroxide by using cyclic voltammetry and amperometric techniques. The obtained results confirmed that the current enzymatic biosensor exhibits a fast, highly sensitive, and cost-effective detection of cholesterol. Cholesterol in the concentration range of 0.15-0.55 mmol l(-1) was determined with a detection limit of 4.9 x 10(-5) mol l(-1) by the amperometric method, and the sensitivity of the proposed method was found to be 17.38 mu A/mmol l(-1). Normal electroactive species such as ascorbic acid and glucose in the presence of the constant concentration of cholesterol in the samples do not interfere with the determination