Highly sensitive volatile organic compounds vapour measurements using a long period grating optical fibre sensor coated with metal organic framework ZIF-8

Sergiy Korposh,Jiri Hromadka,Ricardo Correia,Stephen P Morgan,Begum Tokay

doi:10.1016/j.snb.2018.01.015

Sergiy Korposh, Jiri Hromadka + Show 3 more

Open Access

https://doi.org/10.1016/j.snb.2018.01.015

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Abstract

An optical fibre long period grating (LPG) based volatile organic compound (VOC) sensor coated with ZIF-8, a material from the zeolite imidazolate framework (ZIF) family, functional coating is presented. ZIF-8 film was deposited onto the surface of the LPG using an in-situ crystallization technique by mixing freshly prepared 12.5 mM zinc nitrate hexahydrate and 25 mM 2-metyl-imidazole solutions in methanol. A concentration specific response to acetone, ethanol and methanol vapour was obtained over the high concentration range up to tens thousands ppm. The LPG based sensor works at phase-matching turning point (PMTP) and such operates at the highest sensitivity. A novel approach for the data analysis based on the measurement of the bandwidth of the U-shaped attenuation band of the LPG is introduced. The optimized sensor shows a sensitivity of 0.015 ± 0.001 and 0.018 ± 0.0015 nm/ppm and limit of detection (LOD) of 6.67 and 5.56 ppm for acetone and ethanol respectively.

Highlights

The fabrication of low-cost, portable, accurate and real-time sensors for organic vapour detection is of considerable interest in biomedical fields and in food quality monitoring [1]
We have recently demonstrated for the first time, to the best of our knowledge, proof of concept data for the detection volatile organic compound (VOC) using a long period grating (LPG) coated with ZIF8 [39]
Where LOD indicates limit of detection, Sd is the average standard deviation obtained over the values measured in stable conditions over the 2 min period and m is the slope of the calibration curve

Summary

Introduction

The fabrication of low-cost, portable, accurate and real-time sensors for organic vapour detection is of considerable interest in biomedical fields and in food quality monitoring [1]. Ethanol and acetone represent the most common examples of volatile organic compounds (VOCs). VOCs are usually measured using gas chromatography–mass spectroscopy (GC–MS), the detection is expensive and needs experienced personnel [5]. Semiconducting material based sensors exhibit high sensitivity whilst they usually operate at high temperatures (200–400 ◦C) to achieve chemical reactivity between the sensing material and the target gases. The fabrication of the sensitive layer should be conducted at high temperature and is associated with high energy consumption [11,12]

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