Study For Refracometric Porous Moisture Sensitive Films

At present, the field of environmental protection, food safety, petroleum chemical industry, medical and biological technology has a wide range and the urgent demand of the humidity sensor. one of the effective factors of moisture measurement is the porous humidity sensitive film which has specific function to the measured molecular. Our study shows that we should design and prepare the refractive index of porous type humidity sensitive film, which is of great significance for the development of high sensitivity, wide detection range, response speed and good long-term stability of light type humidity sensor. In the light type humidity sensor, the chemical and physical properties of porous humidity sensitive film directly influences the performance of light type humidity sensor. The output of sensor is through the concentration of the substance to be determined refractive porous humidity sensitive film and the rate of the environment to establish quantitative relationship. In order to make the humidity sensitive material has a appropriate refractive index and change, there is a basic requirement for the material of humidity sensitive film: the water molecules easily import humidity sensitive film and interact with the humidity sensitive material. Therefore, an effective method is to use a humidity sensitive film is designed and fabricated into mesoporous film. In the humidity sensitive film formed appropriate mesopores to reduce the resistance of diffusion of water molecules in the pores of the porous membrane.This paper mainly includes the following four aspects:.(1)In the light type humidity sensor, the key are the refractive index of humidity sensing film and its change with environmental humidity. Therefore, from the theoretical research we must first discuss the optical properties of humidity sensitive film, especially the change of refractive index of humidity sensitive film before and after the adsorption of water molecules. In addition, in some light type humidity sensor, the thickness of humidity sensitive film with the change of environmental humidity is also very important, so this paper also discussed volume change of the humidity sensitive membrane after adsorbing water molecules.(2)Using the template syntheses inorganic mesoporous materials(SiO2,Al2O3 films), and using polymer materials directly syntheses three kinds of organic porous films, such as SAN film, PVA film and Nafion film. Through the characterization of these films to explore their pore size distribution, the factors of influencing pore size and the methods of controlling pore size and distribution.(3)In order to understand the process of the water molecules import humidity sensitive film, the interaction of water molecules with humidity sensitive film and the adsorption amount of humidity sensitive film, we introduce the kinetics adsorption model and adsorption isotherm model. Using vapor adsorption instrument, through the micro balance experiment measure and analysis the adsorption kinetics curve and adsorption isotherm of several materials on water molecules.(4)In order to explore the immobilized technology of humidity sensitive film on gold glass and gold plated SPR optical fiber probe. And based on the numerical simulation, we used SPR tester and cone SPR sensing system to detect the SPR spectrums of SiO2 film, PVA film and Nafion film in different humidity environment. Also discussing the resonance angle and their refractive index changes with the relative humidity of the environment.