Versatile Electrochemical Sensing with a Prussian Blue Zinc Oxide Carbon Nanotube Composite

Abstract

The design of a sensor is currently required for reliable, accurate and rapid quantification of hydrogen peroxide (H2O2). The selective measurement of H2O2 in complex systems is crucial because H2O2 plays a vital role in various fields such as cosmetic and pharmaceutical companies, clinical control, chemical and biochemical industry, agriculture products, fuel cells, environmental protection, organic synthesis and cancer cell analysis. Complex, time consuming and expensive methods are used to determine H2O2 concentrations under current practices. Our method uses electrochemical techniques for real-time monitoring of H2O2 directly. To design a selective and sensitive sensor for H2O2, the earth rich materials including ZnO, carbon nanotubes (CNTs) and Prussian Blue (PB) were synthesized and applied. ZnO nanoparticles were synthesized using a reflux-synthesis process before attaching them to functionalized CNTs (COOH-MWNTs). After tethering refluxed ZnO to carboxylic acid functionalized multiwalled carbon nanotubes (COOH-MWNTs), an electrochemical sensing composite was produced by electrostatically attaching Prussian Blue to ZnO/COOH-MWNTs to enhance sensitivity towards H2O2. ZnO nanoparticles were characterized by transmission electron microscopy (TEM). A simple ultrasonication process was used to tether ZnO synthesized nanoparticles. Finally, PZC concept was applied to attach PB on the surface of ZnO/COOH-MWNTs. The morphology and chemical composition of ZnO/COOH-MWNTs and PB/ZnO/COOH-MWNTs composites were studied under TEM, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The modification of glassy carbon electrode (GCE) was performed using the PB/ZnO/COOH-MWNTs. Nafion(2wt%) was used to cap the nanocomposite on the GCE to design a Nafion/PB/ZnO/COOH-MWNTs sensor to monitor H2O2. The electrocatalytic activity of the prepared sensor for the reduction and oxidation of H2O2 was examined under cyclic voltammetry (CV) and chronoamperometry (CA) techniques. The cytotoxicity study of the PB/ZnO/COOH-MWNTs composite for its potential in vivo use was also done with the help of an Alamar Blue assay. A practical use of Nafion/PB/ZnO/COOH-MWNTs/GCE sensor for ex situ determination of H2O2 in BT20 and 4T1 cancer cells was explained. The sensor demonstrated a wide linear response in the range of 1 µM to 3 mM concentration at an operating potential of -0.004 V on the potentiostat. In addition, this sensor was used to delineate the role of oxidative stress in cancer cell viability by measuring the concentration of H2O2 in response to apoptosis in BT20 cancer cells. This sensor shows excellent reproducibility, good stability and it is used as versatile sensor to measure H2O2 in different environments. In addition, the same sensor is versatile to study other analytes such as homomvanillic acid, dopamine and glutathione at different potentials.