Volatile Organic Compound Optical Fiber Sensors: A Review

Abstract

Volatile organic compound (VOC) detection is a topic of growing interest with applications in diverse fields, ranging from environmental uses to the food or chemical industries. Optical fiber VOC sensors offering new and interesting properties which overcame some of the inconveniences found on traditional gas sensors appeared over two decades ago. Thanks to its minimum invasive nature and the advantages that optical fiber offers such as light weight, passive nature, low attenuation and the possibility of multiplexing, among others, these sensors are a real alternative to electronic ones in electrically noisy environments where electronic sensors cannot operate correctly. In the present work, a classification of these devices has been made according to the sensing mechanism and taking also into account the sensing materials or the different methods of fabrication. In addition, some solutions already implemented for the detection of VOCs using optical fiber sensors will be described with detail.

Detection of Odorant Molecules in the Gaseous Phase Using α-, β-, and γ-Cyclodextrin Films on a Quartz Crystal Microbalance

“…After rinsing with Milli-Q water, the sensor cell was filled with 500 µL of EGDE solution (1 mM), buffered with 10 mM HEPES/NaOH (pH 8.0) for 1 h to immobilize epoxide groups on the sensor surface through reaction of EGDE with the amino groups. The sensor cell was rinsed with HEPES buffer, and then filled with 20 µL of CD solution, prepared by mixing 20 µL of 3 wt% EGDE aqueous solution with 100 µL of 8 M NaOH solution containing 5 mg of CD (α-, β-, or γ-CD) or pentaerythritol and 0.05 mg of NaBH 4 . After incubating for 20 min at 20-23 • C, the sensor surface was rinsed three times with 500 µL of Milli-Q water to quench the reaction, and to remove unreacted reagents from the film.…”

“…The gas-sensing of volatile organic compounds (VOCs), such as benzene, toluene, and xylene, is important for the air safety of indoor environments [4][5][6]. The detection and quantification of odorant molecules from fruits are useful for quality control in agriculture, due to reports that fragrance intensity may be related to the maturity of fruits [7,8].…”

Optical Sensing Performance of Multimode Polymer Optical Fiber (POF) Coated with ZnO towards Methanol Vapour

“…[13] Modification cladding of the optical fiber was found to be more sensitive due to the manner of light propagation in the on the unclad portion of optical fiber core. A fraction of the optical power was found to propagate outside the tapered optical fiber core.…”

Detection of Ethanol in Human Breath Using Optical Fiber Long Period Grating Coated with Metal-Organic Frameworks

“…This coupling can be observed in the transmission spectrum as a series a loss bands, whose central wavelength is sensitive to external conditions, such as temperature, bending or refractive index. In order to develop a VOC sensor based on LPG, this structure must be functionalized with a coating that is sensitive to the target VOC [13]. In this work, the LPG has been coated with a ZIF-8 sensing coating, which is a metal-organic framework that exhibits cavities for gas storage [14].…”