Sustainable synthesis of a PtNPs@rGO nanohybrid for detection of toxic fluoride ions using hand-made screen-printed electrodes in aqueous medium

High fluoride (F^-) concentrations in groundwater affect over 200 million people across 25 countries, making accurate detection and quantification of fluoride in water essential for safety assessment. There is a growing demand for advanced water quality testing systems that provide real-time, location-specific data without requiring specialized expertise. This study presents the development of a simple, eco-friendly, and cost-effective nanosensor for electrochemical F^- detection in environmental water samples. To our knowledge, this is the first report on the green synthesis of platinum nanoparticles (PtNPs) using <i>Ficus religiosa</i> (sacred fig) leaf extract <i>via</i> a co-precipitation method. Additionally, PtNPs were synthesized <i>ex situ</i> and decorated on reduced graphene oxide (rGO) to form a nanohybrid using ultrasonication. The PtNPs@rGO nanohybrid was then deposited on a disposable screen-printed carbon electrode (SPCE) to fabricate the PtNPs@rGO/SPCE nanosensor using a drop-casting technique. This approach enhances the specificity and sensitivity of the sensor, addressing current analytical challenges. The PtNPs@rGO nanohybrid was characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis, contact angle (CA) measurement, and electrochemical techniques such as differential pulse voltammetry (DPV) and cyclic voltammetry (CV). The PtNPs@rGO/SPCE nanosensor exhibited a wide linear range from 0.001 to 160 μM for F^- concentrations, with a limit of detection of 10 nM and a limit of quantification of 0.036 μM. The sensitivity was 4.126 μA μM^-1 cm^-2. The sensor demonstrated excellent reproducibility and strong anti-interference properties. It was successfully applied for F^- detection in tap, drain, and tube well water samples, yielding satisfactory recoveries, and its performance surpasses those of previously reported sensors for aqueous F^- sensing.