Organic-Inorganic Nanohybrid Electrochemical Sensors from Multi-Walled Carbon Nanotubes Decorated with Zinc Oxide Nanoparticles and In-Situ Wrapped with Poly(2-methacryloyloxyethyl ferrocenecarboxylate) for Detection of the Content of Food Additives.

Jing-Wen Xu,Zhan-Qing Liu,Zhuo-Miao Cui,Feng Xu,Ya-Shao Chen,Yan-Ling Luo

doi:10.3390/nano9101388

Abstract

An electrochemical sensor for detection of the content of aspartame was developed by modifying a glassy carbon electrode (GCE) with multi-walled carbon nanotubes decorated with zinc oxide nanoparticles and in-situ wrapped with poly(2-methacryloyloxyethyl ferrocenecarboxylate) (MWCNTs@ZnO/PMAEFc). MWCNTs@ZnO/PMAEFc nanohybrids were prepared through reaction of zinc acetate dihydrate with LiOH·H2O, followed by reversible addition-fragmentation chain transfer polymerization of 2-methacryloyloxyethyl ferrocenecarboxylate, and were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Raman, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), scanning electron microscope (SEM), and transmission electron microscope (TEM) techniques. The electrochemical properties of the prepared nanohybrids with various composition ratios were examined by cyclic voltammetry (CV), and the trace additives in food and/or beverage was detected by using differential pulse voltammetry (DPV). The experimental results indicated that the prepared nanohybrids for fabrication of electrochemical modified electrodes possess active electroresponse, marked redox current, and good electrochemical reversibility, which could be mediated by changing the system formulations. The nanohybrid modified electrode sensors had a good peak current linear dependence on the analyte concentration with a wide detection range and a limit of detection as low as about 1.35 × 10−9 mol L−1, and the amount of aspartame was measured to be 35.36 and 40.20 µM in Coke zero, and Sprite zero, respectively. Therefore, the developed nanohybrids can potentially be used to fabricate novel electrochemical sensors for applications in the detection of beverage and food safety.

Highlights

Aspartame is a dipeptide artificial sweetener, and extensively used in the manufacturing of many sugar-free, low calorie, and dietary products [1,2]
Inspired by the above description, our aim is to prepare MWCNTs scattered with zinc oxide (ZnO) (MWCNTs@ZnO) nanocomposites, and to wrap poly(2-methacryloyloxyethyl ferrocenecarboxylate) (PMAEFc) around MWCNTs@ZnO to achieve a novel MWCNTs@ZnO/PMAEFc organic–inorganic nanohybrid for modification of amperometric sensing electrodes
The increased IG/ID values with increasing the PMAEFc mass percentage are maybe due to more π–π conjugation interactions between MWCNTs and Cp, which have a contribution to good crystalline graphitic structure of the MWCNTs. These findings indicate that the ZnO nanoparticles (ZnO NPs) and PMAEFc homopolymer are decorated or covered at the defect dots or/and on the surface of MWCNTs successively

Summary

Introduction

Aspartame is a dipeptide artificial sweetener, and extensively used in the manufacturing of many sugar-free, low calorie, and dietary products [1,2]. Most extensively adopted detection methods for aspartame have capillary electrophoreses [7,8] and high-performance liquid chromatography (HPLC) techniques [9]. These techniques have satisfying selectivity and limit of detection (LOD); the drawback is time-consuming and needs expensive instruments and pre-treatment steps in comparison with the electrochemical analyses that have the advantage of quick response, high sensitivity, and simple operation [10]. Electronic tongues and electronic noses have received increasing attention as these techniques gain more and more applicability in pharmaceutical industry including sweeteners analysis [11,12] Their sensitivity, specificity and response range are yet to be improved. This offers us a strong impetus in engineering and developing new sensitive and selective aspartame detection techniques for food safety detection and consumer protection

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