Synthesis and Characterization of Predesigned Gelators and Their Templated Fabrication of Silver Nanoconstructions

• Main Authors: Nguyen NgocThang, 阮玉勝
• Other Authors: Jui-Hsiang Liu
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/60681951066802461457

博士 === 國立成功大學 === 化學工程學系 === 102 === Gels, one of the most important class of soft materials, have received a great interest in terms of both fundamental and practical application in a variety of fields such as material science, environmental science, nanotechnology, regenerative medicine and drug delivery. Herein, two attractive types of gels, molecular gels and polymeric gels, have been designed, synthesized, characterized, and further investigated as soft templates for fabrication of silver nanoconstructions. For the first gel type, a molecular gelator based on cholesterol, cholesteryl-pyridine-carbamate (CPC), has been designed and synthesized. The self-assembly behaviors of this chiral gelator in various organic solvents and mixed solvents have been examined in order to obtain specific molecular aggregations. A number of testing means confirmed that the CPC gelator formed the gel in 17-solvent examinations with well-ordered nanofibrous structures. Especially, the chiral gelator promoted the formation of long nanotubes in the mixed solvents of water-anisole and water-ethanol. To realize the potential applications of soft materials in the bottom-up nanofabrication, the CPC nanotubes in the water-anisole system have been further developed as the soft templates for the fabrication of silver nanostructures, especially silver nanochains and silver nanowires. The ultra-high aspect ratio silver nanowires with diameters in the range of 20-70 nm and lengths up to hundreds of micrometers have been obtained via the classic silver mirror reaction at room temperature. Based on these results, the author anticipated that such system may not only advance the field of nanodevice fabrication, but also enable the development of various new nanomaterials for diverse promising applications. For the second gel type, a series of hydrogel thin films based on biocompatible polymers of poly(vinyl alcohol) (PVA) and chitosan (CTS) has been synthesized via ultraviolet (UV) irradiation using acrylic acid (AA) monomer as a crosslinker, without the addition of any other photo-initiator. The characteristics of the PVA/CTS hydrogel thin films, such as swelling behaviors, intermolecular chemical bonds, molecular structures, thermal behaviors, degrees of crystallinity, morphologies of the surfaces and internal structure, and their relationship to the UV irradiation time and AA concentration, have been examined by several analysis tools. It confirmed that the hydrogel films encompassed a uniform inter-porous structure and exhibited reversible swelling in response to changes in the pH of the media. To further extend promising applications of the prepared hydrogels for biomedical field, a green synthesis of silver nanoparticle-loaded PVA/CTS hydrogel thin films has been performed through the in situ reduction of silver nitrate by using glucose as a non-toxic reducing agent and sodium hydroxide as an accelerator. The composite films were characterized using several analysis tools and mechanical test. The results showed that the nanoparticle agglomeration was prevented through the use of the high-crosslinking and dense inter-porous network as an effective nanoreactor template. The tensile test revealed that the effective incorporation of silver nanoparticles within the hydrogel networks rendered the composite films more elastic. From these results, the author expected that the PVA/CTS hydrogel thin films and their nanocomposite films could provide smart hydrogels with some advantages of pH-responsive, antibacterial and good mechanical properties for biomedical applications such as wound dressing.