이황화몰리브덴(MoS2) 나노입자가 코팅된 광섬유 기반 습도 센서 연구

Abstract

In this study, a humidity sensor was developed by combining the etched multimode optical fiber and the side polished optical fiber with the MoS2 nanoparticle sheet. We quantified and predicted the change in optical properties due to the interaction of MoS2 and H2O molecules. We simulated using the correlation between the refractive index of MoS2 and the attenuation coefficient k with respect to the change in hole carrier concentration for the doping material. Here, the doping material means H2O. It was confirmed that as the hole carrier concentration increased, the refractive index of MoS2 decreased and the attenuation coefficient k increased. At this time, the amount of change in each component changed nonlinearly. MoS2 was produced by synthesizing 0.363 g of Na2MoO4·2H2O and 0.33 g of Ch3CSNH2 at 200 °C for 24 hours. The sensitivity was improved by etching the multimode optical fiber up to about 50 μm in diameter. MoS2 synthesized to coat MoS2 on the fiber optic surface was mixed with a Dimethylformamide (DMF) solution. DMF solutions are mainly used as suspension solvents of materials such as MoS2. MoS2 mixed with the DMF solution changes in particle size and properties over time. We selected a coating solution by comparing MoS2 and DMF solutions without DMF solutions with sensitivity over time. The coating solution had the highest sensitivity when used immediately after MoS2 and DMF were mixed. We developed a humidity sensor by etching multimode optical fibers up to a core size of 50 um, thereby improving etching difficulty and reproducibility. In the case of an etched optical fiber sensor, the reactivity to breathing was up to 0.5 dB. The response rate to breathing was about 0.85 seconds, and the recovery rate was about 2.952 seconds. In the case of lateral polishing optical fibers, the reactivity to breathing was up to 0.14 db. The response rate to breathing was about 0.7 seconds, and the recovery rate was about 3.212 seconds. In the reported study, the reactivity of the single-mode optical fiber-based MoS2 humidity sensor is up to 0.01 dB. We conducted an experiment using a humidity chamber to confirm the performance of the developed sensor for humidity changes. The signal change of the sensor was monitored by applying a change in humidity from 40 to 80% in the humidity chamber. Due to the limitation of the humidity control capability of the humidity chamber, a rapid change in humidity occurred in some humidity changes. However, the developed sensor also detected such a change in humidity. The humidity sensor developed in this study uses an absolute humidity measurement method. However, the commonly used humidity measurement method is the relative humidity measurement method. Relative humidity is calculated and expressed based on absolute humidity and current temperature. Therefore, a system for simultaneously measuring temperature and humidity using fiber-based temperature sensor Fiber Bragg Grating (FBG) was proposed. Through the respiratory response index, the direction of improving the performance of humidity sensors in future studies is presented.