Nanorod-Engineered Sm ₂ O ₃ Modified Screen-Printed Carbon Electrodes for Electrochemical Sensing of Sildenafil, Nitrite, and Paracetamol

Accurate voltammetric determination of paracetamol (acetaminophen; ACT), nitrite (NO 2 – ), and sildenafil (SILD) analytes in a single step is highly required yet challenging in biofluids and pharmaceutical matrices. Herein, samarium oxide (Sm 2 O 3 ) with rod-like morphology was synthesized via a direct hydrothermal route, followed by thermal treatment at 400 °C. The Sm(OH) 3 nanorods (NRs) were initially formed and subsequently transformed into cubic crystals of Sm 2 O 3 NRs with an average diameter of 50 nm and a length of 0.6 μm. The resulting Sm 2 O 3 NRs exhibit well-defined surface cavities, high surface exposure, and preferential crystallographic growth, which are desired for enhancing electron-transfer processes. The Sm 2 O 3 NRs were drop-cast onto screen-printed carbon electrodes (SPEs) and employed as a nonenzymatic platform for simultaneous electrochemical analysis of ACT, SILD, and NO 2 – . Well-resolved oxidation peaks of ACT, NO 2 –, and SILD were observed on the Sm 2 O 3 NRs-SPEs at 0.57, 0.81, and 1.30 V (vs Ag/AgCl), respectively, in Britton–Robinson (B.R.) buffer of pH 2.0. The potential peak separation enabled sensitive individual and simultaneous analysis of the target analytes in wide concentration ranges of 2.65–2511.72 μmol/L ACT, 14.97–8849.79 μmol/L NO 2 –, and 0.49–1316.95 μmol/L SILD with low limit of detections (LODs) of 1.24 μmol/L, 1.477 μmol/L, and 97 nmol/L, respectively. Exceptional selectivity, stability, and recovery in pharmaceutical formulations and biological samples underscore the potential of Sm 2 O 3 NRs-SPE as a promising electrochemical sensor for multianalytes.