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 degrees C. The probe with a similar to 334 nm thick Al2O3 coating exhibited the highest response, reaching 6.2 % at 100 degrees C in 100 ppm acetone. Linear regression revealed that the similar to 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.