Desenvolvimento de sensor eletroquímico para bisfenol a utilizando nanoesferas de sílica carregadas com nanopartículas de ouro

Abstract

The growing concern with chemical compounds classified as endocrine disruptors has awakened increasing attention in the scientific environment. Those compounds act or interact when absorbed by the body by altering the animal endocrine system, causing the replacement or blocking of natural hormone actions in living organisms, altering and impairing normal functioning, such as growth, metabolism and reproduction. Because of their wide distribution and the various potentially harmful effects attributed to pesticides, herbicides, fungicides, a diversity of drugs and other industrial chemicals, such as Bisphenol A (BFA), there is a need to identify, quantify and inactivate these species in the most several matrices in which they are found. Because they present active physiological activity at low concentrations (ng L-1), it is necessary to detect and quantify these species in this concentration range. In this way, the use of electrochemical sensors has been increasingly exploited as an alternative technique to the conventional techniques of identification and quantification, due to its low cost, in loco operation and possibility of modification of the working electrodes, providing greater applications. The development of new materials using silica nanospheres as a support for gold nanoparticles has been an alternative in the manufacture of modified electrodes because they have different properties such as high surface area, structure diversity with different porosities and high reactivity have had a variety of applications. The synthesized materials were characterized by Infrared Spectroscopy with Fourier transform (IV-TF) and Scanning Electron Microscopy (SEM). It was observed that all materials presented silica bands in the IV-TF and size of nanospheres similar to SiO2 and AuSiO2300, at 60.4 and 60.1 nm, respectively. A reduction in bead size was observed in AuSiO2700 material (54.1 nm), which may be due to the heat treatment employed. Incorporation of the metal on the surface of the materials was performed by the precipitation deposition method using urea and HauCl4 as the metal precursor. The materials were characterized by Electronic Spectroscopy in the Visible Ultraviolet (UV-Vis) region, Electronic Transmission Electron Microscopy (TEM) and X-ray Diffraction (XRD). The formation of absorption bands characteristic of gold spherical nanoparticles at 523 and 528 nm was observed. The presence of hollow silica nanospheres was observed in the TEM images. The diameter of the gold nanoparticles for the materials was calculated using data obtained by XRD and applying the Scherrer equation. Values of 25 and 27 nm were obtained for the materials AuSiO2300 and AuSiO2700, respectively. The materials were characterized by electrochemical techniques. The electrode modified with AuSiO2700/QTS was applied as an electrochemical sensor for Bisphenol A, presenting an oxidation potential of 0.842 V and higher peak current among the tested materials. The AuSiO2700/QTS electrode showed a linear response for detection of Bisphenol A in the range of 1 to 1000 nmol L-1, with a detection limit of 1.0 nmol L-1. Thus, the electrode modified with AuSiO2700/QTS was presented as a promising alternative of electrochemical sensor in the detection of Bisphenol A.