Silver-doped TiO2 nanotube array nanosensor for gallic acid detection: active surface and electrochemical enhancement

Original scientific paper

Abstract

The development of electrochemical methods for the detection of phenolic compounds is a highly active area of research, motivated by their simplicity, efficiency and versatility of application. This work presents the synthesis and characterization of an electrochemical nanosensor for the detection of gallic acid, a phenolic compound of nutraceutical and analytical relevance. The nanosensor is based on a titanium electrode superficially modified with a titanium oxide nanotube array doped with silver (Ag-TNA). It was synthesized via electrochemical anodization and characterized using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical properties and gallic acid sensing capability were tested using electrochemical impedance spectroscopy and cyclic voltammetry. The results confirmed the obtention of an electrode surface composed mainly of titanium oxide in the anatase phase with the presence of oxygen vacancies. Metallic silver was found incorporated in interstitial form, while the ionic silver state is present superficially. The presence of silver promotes crystallinity and active surface area of the electrode. The Ag-TNA nanosensor displays two oxidation peaks in response to gallic acid; the first peak, registered at 1.3 V vs. Ag/AgCl, was used for the detection method developed in a linear range of 565 to 4663 µM (R²= 0.997). Key analytical parameters were calculated, obtaining a sensitivity of 118 μA mM⁻¹ cm⁻², limit of detection of 13.2 μM, limit of quantification of 43.9 μM, and relative standard deviation of 3.4 and 4.5 % in repeatability and reproducibility tests, respectively. The sensor exhibited selectivity toward glucose and ascorbic acid, common interferents.