ELECTROCHEMICAL SENSOR BASED ON BLACK TIO2 FOR DETECTION OF FIPRONIL

Black TiO2 (BT) materials have recently attracted interest in electrochemistry due to the presence of Ti3+ and oxygen vacancies in their structure, leading to a drastic increase in conductivity and a reduction in electron transport time [1,2]. Fipronil (FIP) is a phenylpyrazole insecticide used for pest control in crops, and its residues have already been detected in soil, water, and food [3]. Therefore, developing a simple, sensitive, and reliable method for detecting FIP is crucial. This study aimed to synthesize and characterize black TiO2 for detecting FIP in water. BT was synthesized as proposed elsewhere [4], where NaBH4 reduces TiO2 nanoparticles. The material was characterized by N2 physisorption, X-ray fluorescence, X-ray diffraction, and scanning electron microscopy. Carbon paste electrodes modified with 10% by mass of BT were prepared and used as the working electrode in a three-electrode electrochemical cell, including an Ag/AgCl reference electrode (3 mmol L-1 NaCl) and a platinum wire counter electrode. The sensors were electrochemically characterized by cyclic voltammetry using a 5 mmol L-1 standard solution of ferricyanide ([Fe(CN)₆]³⁻) in 0.1 mol L-1 KCl and for their detection performance with a 2.5 mmol L-1 FIP solution in Britton Robinson (BR) buffer at pH 10 by cyclic voltammetry (CV). The specific surface area of BT is about 126 m2/g. The XRD patterns of this material present the anatase and brookite crystalline phases, without the rutile phase. The electrochemical characterization showed an increase in the Ipa/Ipc ratio and a reduction in ΔEp, revealing an improvement in the reversibility of the system in the presence of BT. FIP oxidation peaks were detected at 0.85 V vs. Ag/AgCl (3 mmol L-1 NaCl) using the electrode modified with black TiO2. The results show promising future applications in efficient electroanalytical detection for this new electrode material (black TiO2).