Déborah de Oliveira Lopes

Titanate nanotubes (TiNTs) combine high surface area with remarkable ion‐exchange capability, making them attractive scaffolds for the construction of electrocatalytic interfaces. Herein, this property was exploited to promote the incorporation of Co(II) ions into TiNTs, followed by the electrochemical growth of cobalt hexacyanoferrate (CoHCF) on screen‐printed electrodes, yielding a robust hybrid electrocatalytic architecture. The resulting TiNT–CoHCF interface exhibited well‐defined and stable Fe(II)/Fe(III) and Co(II)/Co(III) redox processes, confirming the successful immobilization of the mediator and efficient electron‐transfer characteristics. The hybrid material showed excellent electrocatalytic activity toward hydrazine oxidation through a mediated EC′ mechanism, in which electrochemically generated Co(III) species oxidize hydrazine while being continuously regenerated at the electrode surface. Under optimized chronoamperometric conditions (+0.8 V, phosphate buffer solution pH 9.0), the platform displayed a linear response from 0.76 to 69 μmol L ⁻¹ , a sensitivity of 0.048 μA μmol ⁻¹ L, and a limit of detection of 0.56 μmol L ⁻¹ , together with good repeatability (RSD = 3.1%) and operational stability over ten days. The sensor was successfully applied to the determination of hydrazine in commercial X‐ray developer samples using the standard addition method. These findings demonstrate that TiNTs can serve as efficient ion‐exchange scaffolds for the electrosynthesis of prussian blue analog films, providing a simple and versatile strategy for engineering robust electrocatalytic interfaces for electrochemical sensing.

This study presents an electrochemical sensor developed from a glassy carbon electrode modified with nanodiamond film (ND/GCE). This electrochemical response of the proposed sensor was improved, and it showed excellent analytical performance for the detection of paracetamol (PAR), which was attributed to the high PAR charging capacity on the electrode surface and the excellent electrical conductivity of ND. Morphological and electrochemical characterizations of the sensor were performed via scanning electron microscopy (SEM) and cyclic voltammetry using a redox probe [Fe(CN)₆]³⁻. The sensor was applied for the determination of PAR. Quantification was performed using square-wave voltammetry, and it showed a linear concentration range from 0.79 to 100 µmol L⁻¹, with a limit of detection of 0.18 µmol L⁻¹. The proposed sensor exhibited satisfactory repeatability and high sensitivity in the determination of the analyte of interest. The electrochemical sensor was also employed for the analysis of PAR in real samples, with recovery rates ranging between 96.4 and 98.7%. This sensor was successfully used for the determination of the drug in pharmaceutical samples.