Development of a Highly Sensitive Gold and Bismuth Nanoparticle-Modified Amperometric Sensor for Ceftriaxone Detection: Experimental and Density Functional Theory Insights

The detection of pharmaceutical contaminants, such as Ceftriaxone (CTRX), in water sources is a critical environmental and public health concern. Conventional detection methods often suffer from limited sensitivity and stability, making the accurate quantification of low CTRX concentrations challenging. To overcome these limitations, a novel amperometric sensor was developed using a carbon paste electrode (CPE) modified with gold and bismuth nanoparticles (Au-BiNPs). The synergistic electrocatalytic properties of these nanoparticles significantly enhance the sensitivity and stability of CTRX detection in complex environments. The Au-BiNPs-modified CPE (Au-BiNPs/CPE) exhibited excellent electrocatalytic activity toward the oxidation of CTRX, achieving a low detection limit of 0.267 µM and a high sensitivity of 25.9 μA/μM cm². The sensor was optimized to operate at pH 4.0 using Britton–Robinson buffer, following a mixed adsorption–diffusion reaction mechanism. Furthermore, the electrode demonstrated remarkable reproducibility (relative standard deviation [RSD] = 3.0%) and repeatability (RSD = 1.5%). Stability and corrosion resistance were confirmed through Tafel polarization studies, underscoring the sensor's durability and long-term performance. Additionally, density functional theory calculations provided molecular-level insights into the CTRX oxidation mechanism, complementing the experimental findings and further validating the sensor's design. This study presents the first Au-BiNPs-modified CPE for the sensitive detection of CTRX, integrating experimental optimization with theoretical insights. The significant outcomes of this work lay the foundation for advanced sensor development, offering a reliable and efficient platform for the detection of antibiotics in environmental and clinical settings.