Sensores eletroquímicos a base de policaprolactona/óxido de grafeno a partir de fontes de matéria-prima biodegradáveis

Abstract

Endocrine disrupting compounds (EDCs) represent a class of harmful substances for living organisms due to its ability to disrupting the human and animal endocrine hormonal system. Among several EDCs, a xenobiotic known as Bisphenol A (BPA; 4,4'-dihydroxy-2,2-diphenylpropane) has become a crucial public health problem in the last few years. BPA is an organic compound that has been widely used in plastic food packaging, children's toys and even medical materials, and it has been now considered an emerging pollutant capable of causing damage to living organisms, especially in the endocrine system, even at low concentrations (1 pM). In this context, aiming at the detection and quantification of BPA, different methods have been proposed in the last years focusing on simple and reliable strategies. In the last decade, the use of electrospinning technique for the design of sensors/sensory platforms has stood out due to the possibility of producing ultrathin polymeric fiber networks (100 nm < diameter < 1000 nm) and nanofibers (diameter < 100 nm) in a relatively simple and versatile way. The generation of polymeric fibers in these dimensions has a huge influence on the sensitivity of the final devices, due to the improvement of the interconnectivity and increase of the surface area. In addition, electrospinning technique allows the incorporation of chemically functional compounds to the fibers, such as graphene and its derivatives, which may expand and/or maximize the properties of the final materials. Thus, the present work approached the development of a nanostructured electrochemical sensor for the detection of Bisphenol A, based on a sustainable and low-cost route. The design of this sensory platform was based on the electrospinning of a low cost and biodegradable polyester, name polycaprolactone (PCL), with the combination of this material with graphene derivatives (graphene oxide - GO and graphene quantum dots - GQDs) obtained from the complete or incomplete carbonization of citric acid. The incorporation of these derivatives was considered in two ways: i) direct addition to the polymeric solution, before electrospinning process; ii) adsorption of the derivatives directly to the surface of electrospun PCL membranes. Among the tested platforms, the nanomaterials produced from PCL (5 min of electrospinning) on a glass substrate coated with tin oxide and doped with fluorine (FTO), using a voltage of 10kV, and swollen in GO solution for 3 h [adsorption process, ii)], presented higher current intensity, verified by cyclic voltammetry analyzes. Therefore, this platform was chosen for further testing aiming at BPA detection. The sensors revealed a high sensitivity for BPA with a very low detection limit of approximately 23 nM. In addition, the sensors showed good reproducibility, with a relative standard deviation (RSD) of 7.9%, while the sensor's response to 2 µM BPA was 5.7% for seven successive measurements. These results open up a window of applications for this nanostructured material, due to the easy combination of a biodegradable polyester with GO obtained through a sustainable and low-cost process.