2016年3月14日星期一

A Humidity Sensor Based on Silver Nanoparticles Thin Film Prepared by Electrostatic Spray Deposition Process

In this work, thin film of silver nanoparticles for humiditysensor application was deposited by electrostatic spray deposition technique. The influence of the deposition times on properties of films was studied. The crystal structures of sample films, their surface morphology, and optical properties have been investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and UV-VIS spectrophotometer, respectively. The crystalline structure of silver nanoparticles thin film was found in the orientation of (100) and (200) planes of cubic structure at diffraction angles 2θ  =  38.2° and 44.3°, respectively. Moreover, the silver nanoparticles thin films humidity sensor was fabricated onto the interdigitated electrodes. The sensor exhibited the humidity adsorption and desorption properties. The sensing mechanisms of the device were also elucidated by complex impedance analysis.

The humidity measurement is essential in a wide range of industrial applications including the pharmaceutical, food, medicine, and electronics industries. Some humidity sensors have been developed based on a reversible interaction between a material and water vapor, hence acting as a gas sensor. Existing humidity sensing methodologies also rely upon optical, gravimetric, capacitive, resistive, piezoresistive, and magnetoelastic properties of selected materials. Recently, it is reported that the use of nanostructures, such as nanoparticles, nanowire, nanotubes, and polymer nanocomposites, as the humidity sensing materials could enhance the performance of humidity sensors greatly. For these nanostructured materials, the surface effect becomes dominant due to their large surface-to-volume ratio, which is beneficial to construct the humidity sensors and the gas sensors.

In the past few years, electrostatic spray deposition (ESD) technique has been used to prepare a variety of functional materials thin films. Compared with other film fabrication techniques, ESD is a simple set-up process, low cost, a wide choice of precursors, relatively large film growth rate, ambient atmosphere operation, and a good control of the morphology of the deposited layers. The ESD technique was used so far to deposit thin films of functional materials with application in different fields, that is, rechargeable lithium batteries, solid oxide fuel cells, heat exchange reactors, biomedical implants, and sensors.

In this paper, we report the preparation of silver nanoparticles (Ag NPs) thin film by ESD technique. The structural, optical properties and surface morphology were investigated for using for the humidity sensor application. The sensing mechanism of the Ag NPs device was performed by the complex impedance analysis.





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