Tapered-loop plastic optical fibre coated with ZnO nanorods using LED source for formaldehyde sensing application

• Main Author: Hisam, Mohamad Noriszakiy
• Format: Thesis
• Language: English; English
• Published: 2024
• Online Access: http://eprints.utem.edu.my/id/eprint/28322/1/Tapered-loop%20plastic%20optical%20fibre%20coated%20with%20ZnO%20nanorods%20using%20LED%20source%20for%20formaldehyde%20sensing%20application.pdf; http://eprints.utem.edu.my/id/eprint/28322/2/Tapered-loop%20plastic%20optical%20fibre%20coated%20with%20ZnO%20nanorods%20using%20LED%20source%20for%20formaldehyde%20sensing%20application.pdf; http://eprints.utem.edu.my/id/eprint/28322/; https://plh.utem.edu.my/cgi-bin/koha/opac-detail.pl?biblionumber=124260

The development of plastic optical fibre (POF) as an optical sensor presents a promising solution for low-cost sensor production. POF demonstrates commercial potential across various sensing applications, notably in humidity and chemical vapour sensing. Enhancing the sensor's performance involves coating a semiconductor material on a tapered POF. Furthermore, the shape and diameter of the optical sensor significantly influence its sensitivity; a larger diameter introduces more sensing region. Formaldehyde, a hazardous volatile organic compound commonly found in adhesives used in furniture production, building materials, and interior decoration, poses significant health risks, including cancer, when its concentration exceeds safe levels. This study aims to develop a formaldehyde vapour sensor utilising a POF coated with zinc oxide (ZnO) nanorods. The sensor's construction involves tapering the fibre to remove the outer cladding layer, exposing the core layer, and subsequently looping and coating it with ZnO nanorods using the hydrothermal method. Various loop diameters ranging from 3.5 cm to 6.11 cm were prepared with consistent waist diameter. Humidity sensing tests were conducted to determine the optimal diameter. The sensor's sensitivity to humidity levels ranging from 30% RH to 90% RH was observed across different diameter lengths. Results indicate that the sensor with a 6.11 cm diameter exhibited superior performance, with a sensitivity of 0.0285 V/RH and 98.13% linearity. A comparison between coated ZnO and uncoated POF sensors revealed higher sensitivity (0.0285 V/RH) for the former compared to the latter (0.0115 V/RH). Additionally, when subjected to different LED colours—red, blue, and green—the sensor exhibited heightened sensitivity to blue light. The optimised diameter was further tested with varying concentrations of formaldehyde vapour to evaluate the sensor's response, yielding a sensitivity of -0.0062 V/%, indicative of successful formaldehyde sensing capabilities.