Temperature-modulated acetone monitoring using Al2O3-coated evanescent wave fiber optic sensors

This paper presents an experimental study of a fiber-optic-based acetone sensor and its temperature effects for use as a breath analyzer to detect acetone in exhaled breath. The study employs fiber optic evanescent wave-based acetone sensing, utilizing sputter coated Aluminium Oxide (Al₂O₃)-coated probes fabricated via clad modification technique. The optical fibers were coated with Al₂O₃ to achieve thicknesses of 247.03 nm, 334.05 nm, and 468.75 nm. The sensor probes were characterized using, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Ultraviolet-Visible (UV-Vis) Spectroscopy, and Spectroscopic Ellipsometry for uniformity, elemental, optical constants, and thickness of the Al₂O₃. The spectral responses of the probes were analyzed for acetone concentrations ranging from 0 to 100 ppm, with temperature modulation from room temperature to 100 °C. The probe with a ∼334 nm thick Al₂O₃ coating exhibited the highest response, reaching 6.2 % at 100 °C in 100 ppm acetone. Linear regression revealed that the ∼334 nm coated probe had the highest sensitivity at 5.98 counts/ppm. The sensor showed response and recovery times of approximately 12 and 17 seconds, respectively. This study underscores the stability and repeatability of temperature-modulated Al₂O₃-coated fiber optic sensors for selective acetone detection in various non-invasive applications.