Samarium oxide (Sm₂O₃), such as electrochemical sensors, is a promising material in various application prospects and industries. Additionally, Sm₂O₃ leverages electron transport capabilities, high electrical conductivity, and thermal stability to develop an effective material in electrode modification for detecting hazardous pollutants. Hydrazine and p-nitrophenol are compounds commonly used in producing insecticides, pesticides, pharmaceuticals, and the chemical industry. However, these compounds can become hazardous environmental pollutants and pose serious health risks to humans. Therefore, this research aims to examine the impact of modifying gold electrode (GE) with Sm₂O₃ nanoparticles, characterizing the electrochemical results, and assessing sensor performance through the use of the GE/Sm₂O₃ NP electrode. In this context, the purpose is to detect hydrazine and p-nitrophenol through voltammetry, with analytical parameters including recovery, repeatability, detection limit, quantification limit, and linear range. The results show that the synthesis of Sm₂O₃ nanoparticles and the performance of the sensor and analytical parameters of GE/Sm₂O₃ NP are carried out in detecting hydrazine and p-nitrophenol using the Cyclic Voltammetry (CV) method. Furthermore, the significant increase in the current response validates the improvement of GE conductivity as an electron transporter. The sensor performance has been studied, and analytical parameters have been determined. For hydrazine and p-nitrophenol, the values are recovery of 98.74 % and 99.01 %, repeatability of 99.42 % and 98.45 %, limit of detection (LoD) of 0.4684 μM and 0.50332 μM, limit of quantification (LoQ) of 1.4194 μM and 1.5252 μM, and linear concentration range for both analytes from 0.1 μM to 7 μM.

Gadolinium (Gd) nanoparticles (NPs) are increasingly considered as a viable alternative to clinically employed Gd chelates in magnetic resonance imaging (MRI). The utilisation of these materials as contrast agents offers several advantages including lower toxicity, prolonged circulation time, and a sufficiently high Gd content, thereby enhancing disease imaging during MRI diagnosis. Therefore, this study synthesised Gd NPs using the hydrothermal method based on the response surface methodology Box-Behnken design (RSM-BBD) to determine the optimal conditions. In this experimental design, three independent variables, the mass of Gd₂O₃ (g), the synthesis temperature (°C) and time (h), were optimised to obtain sufficiently sized nanoparticles for further biomedical applications. In addition, polyethene glycol-6000 (PEG-6000) was used as a stabiliser to form uniformly sized nanoparticles. The optimal conditions were 0.4910 g of Gd₂O₃, a temperature of 180 °C, and a synthesis time of 7 h. Characterisation by scanning electron microscope-energy dispersive X-ray (SEM-EDX) and transmission electron microscope (TEM) demonstrated that the Gd NPs were spherical with a size range below 20 nm. Fourier transform infrared (FTIR) spectroscopy identified PEG molecules with low intensity on the Gd NPs and the obtained zeta potential value was +36.7±0.802 mV. The RSM-BBD analysis applied in this study facilitated the determination of the optimal synthesis conditions.