Enhanced Formaldehyde Sensing Performance using ReS2-Coated Tapered Optical Fibers

Abstract

Formaldehyde (CH₂O) is a toxic, colorless gas widely used in industrial and household materials. Prolonged exposure is known to cause respiratory irritation and increase cancer risk. However, current detection methods frequently suffer from limitations such as high cost, low sensitivity, and limited portability for real-time environmental monitoring. A simple and compact tapered optical fiber sensor is fabricated and coated with Rhenium Disulfide (ReS₂). The TOFs' waist diameters vary between 5 µm and 10 µm during the fabrication
process using a controlled heat-and-pull method. The coated and uncoated TOFs are tested by exposing them to formaldehyde vapor. The formaldehyde solution concentrations are varied from 1% to 5%, with relative humidity levels from 30% to 90%. The tunable laser source is set to 1550 nm, and the output is connected to the optical power meter. The results show that the 5 µm TOF exhibited higher sensitivity and stability than the 10 µm TOF, with ReS₂ coating further improving sensitivity by up to 80%. The sensor performance achieved a
sensitivity of −0.05839 dB/%RH and linearity above 95%. These results show that ReS₂-coated TOFs have the potential to be an affordable, stable, and sensitive platform for formaldehyde detection in humid conditions, with applications in industrial safety and indoor air quality monitoring.