Electrochemical detection of nitrofurazone using laser-engraved three-electrode graphene array.

BACKGROUND: Nitrofurazone (NFZ) is a widely-used antimicrobial agent in aquaculture. The NFZ residue can be transmitted to humans through the food chain, and cause adverse health effects including carcinogenesis and teratogenesis. Until now, a number of modified electrodes have been developed for NFZ detection, however, there are some issues that need to be improved. For example, the reported detection sensitivity is relatively low, the modification procedure is complicated, and conventional three-electrode system is used. Therefore, it is quite important to develop new NFZ detection method with higher sensitivity, simplicity and practicality. RESULTS: Herein, a kind of integrated three-electrode array consisted with porous graphene is easily prepared through laser engraving of commercial polyimide tape. Five kinds of graphene arrays were prepared at different laser power percentage (i.e. 30 %, 40 %, 50 %, 60 % and 70 %). It is found that their structure, morphology, fluffiness and porosity show great difference, consequently affecting the electrochemical performance of graphene arrays such as conductivity, active area and electron transfer ability. The engraved graphene array at 50 % laser power percentage (LIG-50 array) is superior owing to uniform 3D structure, abundant pores and high stability. More importantly, LIG-50 array is more active for NFZ oxidation, and significantly enhances the detection sensitivity. The linear range of LIG-50 sensor is from 0.2 to 8 µM, and the detection limit is 0.035 µM, which is successfully used in fish meat samples. SIGNIFICANCE: A sensitive, portable and practical electrochemical sensor has been successfully developed for NFZ using laser-engraved graphene array. The demonstration using fish meat samples manifests this new sensor has good accuracy and great potential in application. This study could provide a new possibility for the design and fabrication of other high-performance electrochemical sensor for various applications in the future.

Size-Dependent Electrochemistry of Oxygenated Ti3 C2 Tx MXenes.

2D MXenes are widely proved to be potential electrode materials, although the size effect on their electrochemistry is not fully understood. In this work, Ti3 C2 Tx nanoflakes are prepared through acidic etching of Ti3 AlC2 powders, followed by the intercalation treatment with tetrapropylammonium hydroxide. Such a method produces large-scale delaminated and oxygenated nanoflakes. With aid of centrifugation, the nanoflakes with varied lateral sizes and thicknesses are collected, where electrochemical response of charged redox probes and polar phenol molecules is varied. Density functional theory and energy dispersive spectroscopy confirm such electrochemical response is dependent on the size and thickness of used nanoflakes, more exactly the oxygen content on their surface. Taking the nanoflakes obtained using a centrifugal speed of 5000 rpm (MX-TPA0.2 ) as an example, they feature good dispersibility, a high oxygen content, a small size, and a thin thickness. On these nanoflakes electrochemical response of polar p-substituted phenols is pronounced, stemming from a strong electron-withdrawing interaction of their oxygenated termination with the Ar-OH. A sensitive electrochemical sensor is further constructed for the detection of p-nitrophenol. This work thus provides an approach to synthesize MXenes with different sizes and thicknesses as well as further to reveal size-dependent electrochemistry of MXenes.

Electrochemically functionalized graphene for highly sensitive detection of nitrofurazone.

Graphene nanosheets (GS) were prepared by ultrasonic exfoliation of bulk graphite in N-methyl-2-pyrrolidone with the assistance of sodium pyrophosphate. The obtained GS suspension was modified on a glassy carbon electrode (GS/GCE), and then functionalized at different voltages (e.g. 1.0, 1.4 and 1.6 V) for 2 min in pH 7.0 phosphate buffer. The electrochemically functionalized GS/GCE (i.e. EGS/GCE) possesses more oxygen-containing groups and a higher defect level. More importantly, the active response area, electron transfer ability and interface adsorption capacity of the EGS/GCE enhanced remarkably. The possible mechanism of the performance enhancement is discussed, and the sensing application of the EGS/GCE in the detection of nitrofurazone (NFZ) is investigated. Compared with the GS/GCE, the EGS/GCE is much more active for NFZ oxidation and greatly increases the detection sensitivity. As a result, a highly sensitive electrochemical detection method has been developed for NFZ, with a detection limit of 2.1 nM. The practical application of the EGS/GCE was tested in fish meat samples, showing good accuracy and feasibility.