Green synthesis of nickel oxide nanoparticles using Lilium pensylvanicum extract for electrochemical detection of hazardous carbon monoxide gas
摘要
Nickel oxide (NiO) nanoparticles were synthesized via a green, plant-extract-mediated route and systematically characterized for structural, optical, morphological, and gas-sensing properties. X-ray diffraction confirmed the formation of face-centered cubic NiO with nanoscale crystallinity (~ 16 nm), while FTIR and Raman analyses verified Ni–O bonding and the presence of oxygen vacancies essential for gas sensing. The nanoparticles exhibited a strong optical absorption at 370 nm with an indirect band gap of 3.50 eV, attributed to quantum confinement effects. FESEM and TEM revealed uniformly distributed spherical nanoparticles (~ 26 nm). The NiO NPs exhibited a specific surface area of 8.89 m2/g and a pore volume of 25.35 cm3/g, confirming their mesoporous nature. The distinct hysteresis loop observed in the isotherm corresponds to a Type IV isotherm, indicative of capillary condensation within mesopores. When evaluated for carbon monoxide detection, the NiO sensor achieved an outstanding response of 445 at 250 °C for 100 ppm CO, with a rapid response/recovery time of 42/28 s, nearly two times faster than many previously reported NiO-based sensors. The enhanced performance was attributed to abundant oxygen vacancies and efficient charge exchange at the surface. These results highlight the green-synthesized NiO nanoparticles as a promising and sustainable material for high-performance CO detection in environmental and industrial monitoring.