Silk Protein-assisted Fabrication Of Novel Functional Inorganic Nanomaterials

In the past decades, various nanostructured materials have been synthesized via mature techniques. However, the currently emerging challenge is that how to efficiently utilize these novel functional nanomaterials in practical fields. The assembly of functional nano-building block into macroscale bulk materials within hierarchical micro-/nano-structures via advantaged fabrication techniques is a feasible route to broaden the practical applications of nanostructured materials. By hierarchical assembly of nano-building blocks, the obtained bulk materials not only own the properties of nano-building blocks but also behave the synergetic properties and multifunctionalities due to the hierarchical organizations. On the other hand, the research on bio-inspired hierarchical structures indicates that mimicking the biological hierarchical structure in artificial material can enhance and optimize the property and functionality. As one of the analogues of silk-fibroin like protein, silk fibroin (SF) derived from silkworm silk of Bombyx mori is a most common natural biomacromolecular unique sequence-specific self-assembly and their substrate recognition properties. In addition, silks can be formed into fibers, films, gels, and three dimensional scaffolds via all-aqueous processing. Therefore, silk fibroin has been attracted much attentions in chemistry, physics, materials, biology, medicine and other fields.This present thesis will focus on based on silk fibroin multilevel structure and assembly structure to synthesis novel functional inorganic nanocomposite material via different methods. Besides, the formation mechanism and practical properties for corresponding functional nanomaterials have been studied deeply. Use of the silk fibroin unique recognition site (amino acid residue) and self-assembly performance, it is expected to expand the silk fibroin to synthesis novel inorganic nanomaterials (including metal oxide and novel metal nanocomposite) in the electricity, magnetism and biomedical applications with various preparation methods. It is detailed as below.1. In situ reduced Ag nanoparticles with the silk fibroin as a biotemplate at room temperature under light. Regenerated silk fibroin (RSF) from the Bombyx mori silkworm silk were involved in the biotemplate synthesis, providing the dual function of Ag ion in situ reduction and stabilization of silver nanoparticles. Hydroxyl groups in Tyr residues in silk fibroin chains were further identified as the critical active functional groups for Ag ion reduction. The as-prepared RSF-AgNPs composite can maintain stability for up to1months of storage at room temperature in air. Moreover, the RSF-AgNPs composite possess a highly effective and long-term antibacterial and biofilm-inhibiting properties against the S. aurens. Furthermore, the RSF-AgNPs composite could efficiently promote the creaking of the formed mature S. aureus biofilm. The novel composite was expected to be an effective and economical antimicrobial material in biomedical fields.2. Three-dimensional copper oxide nanostructures were synthesized in regenerated silk fibroin aqueous solution at room temperature. In the synthesis process, silk fibroin served as a biotemplate and helped to form the hierarchical CuO nanostructures by self-assembly. Cu(OH)2nanowires were formed at first, and then transformed to almond-like CuO nanostructures with branched ends and compact middle part. The size of the final CuO nanostructures can be tuned by varying the concentration of silk fibroin in the reaction system. A possible mechanism has been proposed based on various characterizations, such as scanning and transmission electron microscopy, X-ray diffraction, and thermogravimetric analysis. The synthesized CuO nanostructure has been evaluated as anode materials for lithium ion batteries, and the result showed it had a good electrochemical performance. 3. Monodispersed hematite nanomaterials were synthesized by a silk fibroin-assisted hydrothermal method. In the synthesis process, silk fibroin served as a biotemplate and gave control over the formation and morphology of hematite nanostructures by self-assembly. The effects of reaction time and silk fibroin concentration on the morphology of hematite have been investigated systematically. Several morphologies including quasi-nanocubes, nanospheres that are composed of primary nanoparticles, and the coexistence of nanospheres and primary nanoparticles were obtained by varying silk fibroin concentration. In addition, these hematite nanomaterials exhibited interesting shape-dependent magnetic properties, which increase the potential application of our synthetic method.4. Porous hematite nanomaterials were synthesized by a silk fibroin-assisted hydrothermal method. Based on the previous research of monodispersed hematite nanomaterials, olive-like porous hematite nanomaterials were successfully synthesized with silk fibroin as a biotemplate by increasing the iron resource. Also, the silk fibroin gave control over the formation and morphology of hematite nanostructures by self-assembly. At first, α-FeOOH nanoneedles were formed, and then transformed to olive-like hematite nanostructures. It was found that the size and morphology of the final hematite was affected by varying the amount of iron resource in the reaction system and the olive-like hematite nanostructures were obtained only when the iron resource was exceed a certain amount. In addition, the concentration of silk fibroin played a critical role on the size and morphology of hematite nanomaterials and various hematite nanomaterials with different morphologies could be obtained by varying the concentration of silk fibroin in the reaction system.In conclusion, a variety of novel functional inorganic nanomaterials (such as noble metals and metal oxides) were successfully synthesized with silk fibroin as a biotemplate in this dissertation. The structures and practical applications of corresponding silk fibroin-assisted functional inorganic nanomaterials have been systematically investigated. In addition, the formation mechanisms for corresponding functional inorganic nanomaterials have been studied deeply. The researches showed that the silk fibroin act as a biotemplate could gave control over the formation and morphology of corresponding functional inorganic nanomaterials by self-assembly, which expand the silk fibroin application in functional material fields and furthermore provided some basis and events experience for the preparation of other novel type of functional materials.