Fabrication and Environmental Responses of Nanostructured Polyaniline Prepared from Colloidal Crystal Templates and Core-Shell Particles
Date Issued
2007
Date
2007
Author(s)
Yang, Ling-Yueh
DOI
zh-TW
Abstract
In this dissertation, we studied two approaches to fabricating nanostructured polyaniline (PANI) using colloidal particles, its environmental responses, and the influence of the structure. One approach was templating polystyrene (PS) colloidal crystals, or close-packed self-assembly of monodisperse microspheres. After the adsorption of dodecylbenzene sulfonic acid (DBSA) and aniline, the polymerization around the PS spheres was initiated by ammonium peroxydisulfate. Removing PS yielded PANI inverse opals of high quality. The use of DBSA resulted in structures having less shrinkage, and thus the position of the optical stop band could be tuned. The conductivity of the inverse opals increased as well, and that of PANI was estimated to be 7 S/cm, comparable to the value in the literature. Moreover, the overall thickness of the inverse opals could be controlled by that of the templates. The other approach first prepared PS-PANI core-shell particles using PS particles as cores, onto whose surface aniline monomers adsorbed with the aid of sodium dodecyl sulfate and were polymerized to form thin PANI shells. The resulting suspensions of the core-shell particles were then drop-cast onto substrates and dried. Two kinds of films composed of randomly packed thin PANI shells of tens of nanometers were obtained by removing PS directly or after the formation of composite films through heating the core-shell particles. The UV-Vis spectra of the films indicate that the heating had no obvious effect on PANI. As for the environmental responses, four tests were included: dry gas flow (decreasing water content), ethanol vapor (swelling), hydrogen chloride (doping), and ammonia (dedoping). The nanostructured PANI was highly sensitive, and the resistance responded fast to different conditions because of the porosity facilitating diffusion and large surface area interacting with substances. The structure was found to greatly affect the response behavior. Concerning the two kinds of films prepared from the core-shell particles, the packing of PANI shells was more compact in the films whose fabrication involved heating; hence the performance was inferior. We also examined the difference between the responses of the inverse opals (highly ordered porous structures) and films prepared from the core-shell particles (disordered structures). Moreover, the optical stop band of the inverse opals could provide a novel sensing mechanism. The results suggest that the inverse opals have the potential of sensing ethanol vapor, hydrogen chloride, and ammonia by the change in the stop band.
Subjects
聚苯胺
膠體晶體
模板
核殼粒子
奈米結構
感測
polyaniline
colloidal crystals
templates
core-shell particles
nanostructures
sensing
Type
thesis
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