Graphite oxide as an efficient and robust support for Pt nanoparticles in electrocatalytic methanol oxidation

An ultra-sensitive electrochemiluminescence probe based on ternary nanocomposite and boron nitride quantum dots for detection of diazinon

A new enzyme-free electrochemiluminescence (ECL) pesticide sensor was fabricated based on ternary nanocomposite of ruthenium nanoparticles/silver nanoparticles/graphene oxide on the surface of glassy carbon electrode for ultratrace determination of diazinon. Due to some drawbacks of enzyme-based sensors such as enzyme instability at elevated temperature, humidity, changes of pH, and high price of the enzyme, the use of enzyme was omitted in the construction of the developed sensor. The silver nanoparticles with good electrocatalytic proficiency as a signal improving agent and tris(2,2bipyridine) ruthenium(II) as a popular luminophore were uniformly deposited on the surface of the prepared graphene oxide/GC electrode at nanoscale. Boron nitride quantum dots as an efficient co-reactant created the superior efficiency in amplifying the ECL intensity of the ruthenium-based ECL system. The prepared electrode was utilized for the detection of diazinon via the robust ECL method. For the present sensor, a wide linear dynamic range and low detection limit were achieved (3.0 × 10^-15 to 6.5 × 10^-9 M and 9.5 × 10^-16 M, respectively). The obtained results confirmed the fabrication of the robust ECL probe, which is characterized by the cooperative effect of silver nanoparticles and the attached luminophore species. The main advantage of the presented sensor was that the samples could be diluted so that the effect of the interference species was negligible. Due to excellent properties toward accurate determination of diazinon, the ECL sensor as a new practical platform was applied for quantitative detection of diazinon in some real samples.

An enzyme-free electrochemiluminescence sensing probe based on ternary nanocomposite for ultrasensitive determination of chlorpyrifos

Herein, an innovative enzyme free electrochemiluminescence chlorpyrifos sensor was reported based on the incorporation of ternary nanocomposite (ruthenium nanobeads/silver nanoparticles/graphene oxide) on the surface of glassy carbon electrode. The silver nanoparticles as a robust signal enhancing agent were well deposited on the modified graphene oxide/glassy carbon electrode and exhibited supreme electrocatalytic proficiency. Then, Ru(bipy)₃²⁺ species in bead-like nanoparticles were uniformly anchored on the surface of the modified electrode with the help of chitosan, as a good crosslinking agent. Boron nitride quantum dots as a new coreactant species showed the excellent proficiency for signal enhancement of the fabricated electrode. The fabricated electrode was successfully used as an ultra-sensitive sensor for trace analysis of chlorpyrifos by ECL technique. The wide linear range and the low detection limit were obtained from 5.0 × 10^-15 to 4.2 × 10^-9 M and 6.5 × 10^-16 M, respectively.

Simultaneous voltammetric sensing of levodopa, piroxicam, ofloxacin and methocarbamol using a carbon paste electrode modified with graphite oxide and β-cyclodextrin

A carbon paste electrode (CPE) was modified with graphite oxide (GrO) and β-cyclodextrin (CD) to obtain a sensor for simultaneous voltammetric determination of levodopa (LD), piroxicam (PRX), ofloxacin (OFX) and methocarbamol (MCB). The morphology, structure and electrochemical properties of the functionalized GrO were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, contact angle measurements and cyclic voltammetry. Under the optimal experimental conditions, the sensor is capable of detecting LD, PRX, OFX and MCB by square wave voltammetry (SWV) at working potentials of +0.40, +0.60, +1.03 and + 1.27 V (versus Ag/AgCl), respectively. Response is linear from 1.0 to 20 μM for LD, from 1.0 to 15 μM for PRX, from 1.0 to 20 μM for OFX, and from 1.0 to 50 μM for MCB. The respective limits of detection are 65, 105, 89 and 400 nM. The method was successfully applied to the simultaneous determination of LD, PRX, OFX and MCB in (spiked) real river water and synthetic urine samples, and the results were in agreement with those obtained using a spectrophotometric method, with recoveries close to 100%. Graphical abstract Schematic presentation of a novel electroanalytical method employing a carbon paste electrode modified with graphite oxide and β-cyclodextrin for the simultaneous determination of levodopa, piroxicam, ofloxacin and methocarbamol in urine and river water samples by square wave voltammetry.