Preparation Of Surface Plasmon Humidity Sensor And Research On Its Sensing Characteristic

Humidity sensors are one of the most common sensors and are widely used in industrial production,meteorological research,critical respiratory detection,medical transportation and many other fields.In recent years,with the continuous improvement of micro and nano processing technology,people’s need to grasp real-time information has become stronger and stronger,and correspondingly,higher requirements have been put forward for humidity sensors.Thanks to the special optical properties of nanostructures,optical humidity sensors made by combining moisture-sensitive materials have the advantages of being immune to electromagnetic interference,wide monitoring range,and high sensitivity.Among them,polyvinyl alcohol(PVA)has a large number of hydroxyl groups(-OH)on its side chain,which makes the sensor have excellent moisture absorption characteristics.In this thesis,humidity sensors with different structures are mainly studied,and the main research contents are as follows:(i)A self-assembled optical humidity sensor based on nanosphere lithography is proposed to achieve bendable and foldable humidity sensing with strong compliance to detected objects on uneven surfaces,and the size of the sensor obtained by using polymer filling and magnetron sputtering can reach the micron level.The optical properties of the structure are investigated using the time-domain finite difference method to clarify the surface plasmon exciton type modes of structural excitation: metal-insulator-metal(MIM),Fabry-Perot(F-P)and Surface Plasmon Polaritons(SPP)modes,and to understand the influence of the parameters of each part of the nanostructure The effect on the sensor.Based on the sensing mechanism of the structure,the paper demonstrates the humidity sensing characteristics in the visible and near-infrared wavelengths and achieves a relative humidity sensitivity of 2.1 nm/%RH.(ii).A PVA/Au nanorod film sensitized optical fiber humidity sensor is proposed,which has significantly improved humidity sensitivity compared with the humidity sensor with only one layer of PVA film.Before the sensitization,this paper simulates the composite structure with Au nanorods placed on the outer side of the metal film,and finds that the surface plasmons resonance(SPR)sensing sensitivity of the pure metal film structure can be significantly improved due to the enhanced local electromagnetic field excited by Au nanorods themselves,and its refractive index sensitivity can reach 3942.3 nm/RIU.After mixing PVA aqueous solution with Au nanorods,the humidity sensitivity can reach-4.25 nm/%RH,and the sensor has good repeatability and stability.