Study of polyaniline-silver nanocomposite as humidity sensor
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Study of polyaniline-silver nanocomposite as humidity sensor J. Bhadra, A. Popelka, N. J. Al-Thani, A. Abdulkareem Center for Advanced Materials, Qatar University, Qatar Abstract In this piece of work focus on fabrication of resistive type humidity sensor using polyaniline-silver nanocomposite (PPVA-Ag). Four different nanocomposites using four concentrations of silver (0.5,1.0, 1.5 and 2.0 M) and polyaniline (PANI) dispersed in polyvinyl alcohol matrix (PVA). PANI, and PVA concentrations are kept constant. Thin PPVA-Ag film on interdigited gold electrode fingers gives excellent sensitivity towards humidity at room temperature. 1. Introduction Since last few decades the information of nanoscience and nanotechnology has been explored extensively to obtain functionalized nanomaterials. One such category of nanomaterial is the polymer- metal nanocomposite, with enhanced mechanical, elastic, optical, electrical and dielectric properties . Polymer nanocomposites are materials with nanosized one dimensional inorganic filler particles (around 10–100 ˚A), dispersed in an organic polymer matrix. An important parameter which has significant importance in many industries such as food, agricultural, clinical equipment and electronics is humidity, it is considered to be one of the most frequently measured physical parameters [2-3]. With the advancement in moisture sensitive technologies, research to achieve high efficient, low cost, reliable and miniature size of material sensitive to humidity change has gained acceleration. As among metal nanoparticles, Ag has high electrical and thermal conductivities, so the composite of Ag dispersed in PANI-PVA matrix gives rise to a functional materials, with improved antimicrobial activity and sensitivity towards humidity. This paper we focus on surface analysis of the thin film obtained using scanning electron microscopy and study on the humidity sensitivity. 2. Methods 2.1 Synthesis of Ag nanoparticles Four different concentrations of silver nitrate (AgNO3) is dispersed in aqueous PVA solution under constant stirring and heating at 60°C followed by photo reduction using UV-lamp having wavelength 390 nm for 24 hours. After exposing the above solutions with UV light for 24 hours, finally, yellowish-red colloid of Ag nanoparticles with average diameters of ∼30 nm and ∼70 nm uniformly dispersed in PVA are obtained. 2.2. Synthesis of PANI-Ag nanocomposite and pure PANI: The PANI-Ag nanocomposite blend is synthesized by in-situ chemical polymerization (Figure-1) of aniline monomer in the colloid solution obtained from section 2.1. During this process, aniline-DBSA is added to the Ag-PVA colloidal solution, followed by addition of the aqueous APS solution dropwise. The resulting blend mixture is left to react for 24 h under constant stirring at 5–10 °C. The colloidal solution obtained are used to prepare thin film on glass slide and interdigitated gold electrode washed with DI water and acetone and dried. Keeping the other concentrations and methods constant four different PPVA-Ag nanocomposites are prepared with 0.5, 1.0,1.5 and 2.0 M of AgNO3.
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