Design and construction of bio carbon derived Bi2Fe4O9 nanocomposites sensor for clad modified optical fiber sensors for detection of ethanol gas

Bio carbon (BC) derived Bi₂Fe₄O₉ hybrid sensor was fabricated via sonochemical approach. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and N₂ adsorption-desorption were used to determine the structural, morphological and porosity characteristics, respectively. The materials' gas-sensing properties were evaluated using a clad-modified optical fiber sensor. The orthorhombic structure with Pbam space group of Bi₂Fe₄O₉ confirmed by the relative diffraction pattern. All sharp intense diffracted patterns might be indexed based on the standard value ((JCPDS card No. 74-1098). Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images illustrate those granular sheets with aggregated spherical shaped morphology of BC and Bi₂Fe₄O₉, respectively. The pristine Bi₂Fe₄O₉ exhibits Raman modes at 378 cm⁻¹ and 617 cm⁻¹, which is ascribed to the orthorhombic structure. The orthorhombic structure was already confirmed from XRD results. BFOG5 sample shows high SSA (107.5 m²/g) and pore size (38.4 nm), which is nearly 2.2 times greater than that of pristine Bi₂Fe₄O₉ (54.3 m^2/g and 23.4 nm). Fiber optic sensor was fabricated and tested for ethanol gas with various gas concentrations (0–500 ppm). The sensitivity (defined as slope of fitted line) enhanced from 14.69 (count/%) for bare Bi₂Fe₄O₉ to 33.94 (count/%) for Bi₂Fe₄O₉/BC (BFOG5). The response and recovery time was 25 s and 20 s for Bi₂Fe₄O₉/BC (BFOG5) sensor, which is higher than that of bare Bi₂Fe₄O₉ (42 s and 33 s). Our findings pave the way for a unique hybrid Bi₂Fe₄O₉/BC composite to be used in a highly sensitive C₂H₅OH gas sensor system at RT.