Composite of Cu metal nanoparticles-multiwall carbon nanotubes-reduced graphene oxide as a novel and high performance platform of the electrochemical sensor for simultaneous determination of nitrite and nitrate.

In the present research, we aimed to fabricate a novel electrochemical sensor based on Cu metal nanoparticles on the multiwall carbon nanotubes-reduced graphene oxide nanosheets (Cu/MWCNT/RGO) for individual and simultaneous determination of nitrite and nitrate ions. The morphology of the prepared nanocomposite on the surface of glassy carbon electrode (GCE) was characterized using various methods including scanning electron microscopy (SEM), atomic force microscopy (AFM), and electrochemical impedance spectroscopy. Under optimal experimental conditions, the modified GCE showed excellent catalytic activity toward the electro-reduction of nitrite and nitrate ions (pH=3.0) with a significant increase in cathodic peak currents in comparison with the unmodified GCE. By square wave voltammetry (SWV) the fabricated sensor demonstrated wide dynamic concentration ranges from 0.1 to 75µM with detection limits (3Sb/m) of 30nM and 20nM method for nitrite and nitrate ions, respectively. Furthermore, the applicability of the proposed modified electrode was demonstrated by measuring the concentration of nitrite and nitrate ions in the tap and mineral waters, sausages, salami, and cheese samples.

New nano-composite potentiometric sensor composed of graphene nanosheets/thionine/molecular wire for nanomolar detection of silver ion in various real samples.

A novel nanographene carbon composite potentiometric sensor for the determination of trace amounts of silver(I) ion was fabricated. Its sensing layer was prepared with the addition of graphene nanosheets into the matrix consisting of graphite powder, diphenylacetylene "a typically molecular wire (MW) as the conductive binder" and thionine as an efficient ionophore. For investigation of the ion-to-electron transducing ability of graphene nanosheets and molecular wire on the electrode surface, the electrochemical impedance spectroscopy measurements were done and the morphology and properties of the electrode surfaces were characterized by scanning electron microscopy. Under the optimized experimental conditions, the suggested potentiometric silver(I) sensor exhibited an excellent Nernstian slope of 59.70 mV decade(-1) with a rapid response to silver(I) ion within ~ 6s. The response was linear in the range 8.00 × 10(-9) to 1.00 × 10(-2) mol L(-1) and calculated detection limit was 4.17 × 10(-9) mol L(-1). The suggested sensor was successfully applied to the determination of silver in radiological film, environmental and drug samples with satisfactory results.

Facile stripping voltammetric determination of haloperidol using a high performance magnetite/carbon nanotube paste electrode in pharmaceutical and biological samples.

Multi-walled carbon nanotubes decorated with Fe3O4 nanoparticles were prepared to construct a novel sensor for the determination of haloperidol (Hp) by voltammetric methods. The morphology and properties of electrode surface were characterized by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. This modified sensor was used as a selective electrochemical sensor for the determination of trace amounts of Hp. The peak currents of differential pulse and square wave voltammograms of Hp increased linearly with its concentration in the ranges of 1.2×10(-3)-0.52 and 6.5×10(-4)-0.52µmol L(-1), respectively. The detection limits for Hp were 7.02×10(-4) and 1.33×10(-4)µmol L(-1) for differential pulse and square wave voltammetric methods, respectively. The results show that the combination of multi-walled carbon nanotubes and Fe3O4 nanoparticles causes a dramatic enhancement in the sensitivity of Hp quantification. This sensor was successfully applied to determine Hp in pharmaceutical samples and biological fluids. The fabricated electrode showed excellent reproducibility, repeatability and stability.

Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base.

A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0×10(-4) and 6.0×10(-4) µmol L(-1) for Hg(II) and Pb(II) with a 90 s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.