Highly sensitive and selective chemiresistive temperature-dependent trace formalin sensor using hydrothermally grown hexagonal yttrium ferrite

Abstract

Formalin (HCHO) is widely employed in industries such as furniture, food processing, textiles, construction, printing, and cleaning. The presence of formalin both in environment and adulterated food can give rise to significant health perils, involving damage to the eyes, kidneys, respiratory, and nervous system. This study demonstrates a trace formaldehyde sensor using hydrothermally prepared yttrium ferrite (YFeO3). The synthesized material was characterized using sophisticated tools. XRD analysis confirms the formation of hexagonal phase with crystallite size ∼30 nm. FESEM, TEM micrographs show agglomerated microstructure is formed. Bandgap energy and surface area have been estimated using UV–Vis, and BET surface area analysis which are ∼2 eV and 10.4 m2/gm respectively. XPS investigation corroborates the existence of bivalent oxidation states of iron as well as oxygen vacancies within the sample. The sensor delineates a remarkably strong p-type response (∼3.12 folds) to 1 ppm formalin with an exceptionally rapid response time of 3 s. Furthermore, it achieved a lower detection limit of 500 ppb, at the optimum temperature of 240 °C. The sensor also showed an admirable ability to respond selectively to formalin, even when subjected to a variety of interfering chemicals (such as acetylene, ammonia, NO2, toluene, etc.), maintaining sensitivity value almost unchanged for a continuous 100 days. The enhanced formalin sensing performance of the hexagonal YFeO3 (YFO) based sensor can be ascribed to a synergistic influence arising from several factors, encompassing augmented surface area, lower bandgap energy, the presence of bivalent oxidation states of iron and oxygen defects.