【作者】 韩婕；

【导师】 张荻； 苏慧兰；

【作者基本信息】 上海交通大学 ， 材料学， 2012， 博士

【摘要】 光功能纳米材料在生命科学、医学、计算机等领域有着广泛的应用前景。为了更好地发挥其优异性能,通常将光功能纳米颗粒与基体材料进行复合,充分发挥各部分的优势,构成智能化、结构-功能一体化的新型材料,如纳米颗粒/修饰组分复合材料和纳米颗粒/基体结构复合材料。然而,这类新型材料在设计、制备和实际应用时存在一些亟需解决的瓶颈问题:合成纳米颗粒的条件苛刻,纳米复合的工艺繁琐,组装结构的样式有限等等。在这一领域,自然界经过上亿年的进化,有许多值得人类借鉴的方面:从成分角度看,许多生物的活性组分能够在极其温和的条件下引导纳米颗粒的合成和组装,并直接与之复合构成性能优异的天然纳米复合材料;从结构角度看,生物创造出了各式各样的集多功能为一体的精巧结构,其中一些微纳米级有序结构迄今为止还难以通过仿生手段实现。在大自然的启迪下,人们提出了以天然生物材料为模板制备新型功能材料的思想,充分利用生物组分和生物结构的优势,简化功能材料的制备工艺以及实现常规手段难以获得的精细结构和独特性能。本论文在此基础上,提出将天然生物材料应用于制备光功能纳米材料的设想,期望利用天然生物材料的活性组分和精细结构,解决上述光功能纳米材料在制备和应用中的瓶颈问题。具体思路是:生物的活性组分在制备过程中引导无机光功能纳米颗粒的合成和组装,起到简化工艺和化学模板的作用,并在复合产物中发挥其生物相容性,起到修饰纳米颗粒的作用;生物的精细结构在复合产物中起到提供固态基体和附加光学性能的作用。可见,基于生物模板的光功能复合材料将为功能材料的研究带来新的机遇。本论文开展了以下工作:1.以蚕丝丝素纤维为基体原位合成硫化物纳米颗粒的研究选用具有化学活性的蚕丝丝素纤维作为生物模板,引导典型光功能材料硫化镉纳米颗粒在其上的原位合成和组装,探索自然的启示对制备光功能纳米材料的借鉴作用。设计了一条常温常压的浸渍工艺,成功地在蚕丝丝素纤维上合成和组装了硫化镉纳米颗粒,获得了纳米硫化镉/蚕丝丝素纤维固态产物及分散于氯化钙溶液的纳米硫化镉/蚕丝丝素蛋白液态产物。制备过程中,蚕丝丝素纤维起到提供反应位点、作为固态载体及组装纳米颗粒的作用。得到的硫化镉为六方相,其颗粒直径(粒径)随着硫源前驱体浓度的增大而减小,随着在硫源前驱体中浸渍时间的延长而增加,变化范围是3.8~7.9 nm;其组装形态也受硫源前驱体浓度和在其中浸渍时间的影响,有沿蚕丝丝素纤维表面均匀排列的线形组装体和由蚕丝丝素纤维连结的六方片形组装体两种。通过改变纳米硫化镉的粒径与组装形态,可调控复合材料产物的光学性质:产物的吸收边和荧光带边发射峰随粒径的减小而蓝移;与常规分散态纳米颗粒相比,线形组装体表现出相同的荧光发射性质,六方片形组装体表现出红移和宽化的荧光发射峰。以上研究证实了蚕丝丝素纤维能在温和条件下引导纳米硫化镉的合成和组装,为后续工作的开展提供了实验依据。2.纳米氧化物/蚕丝生物相容光功能复合材料的研究在上述纳米硫化镉/蚕丝丝素纤维工作的基础上,先利用蚕丝丝素纤维引导合成对人体无毒、且能发射长波长可见光的氧化锌纳米颗粒,再利用生物相容的蚕丝丝素蛋白直接修饰所得的纳米氧化锌,探索自然的启示对制备生物医用光功能纳米材料的借鉴作用。设计了一条常压温和的制备工艺,获得了纳米氧化锌/蚕丝丝素纤维固态产物及纳米氧化锌/蚕丝丝素蛋白液态产物。制备过程中,蚕丝丝素纤维起到提供原位反应位点、作为纳米颗粒固态载体、控制颗粒形状及缺陷状态的作用,而工艺参数会影响纳米颗粒的分布均匀度。得到的氧化锌主要为平均粒径约13 nm的六方相圆形纳米颗粒。固态产物在日光下呈白色,其抗紫外线能力优于原始蚕丝丝素纤维,并且在小于370 nm的紫外光激发下能发射中心位于约600 nm的橙黄色磷光,持续时间大于0.1 ms。液态产物综合了纳米氧化锌的光功能性和蚕丝丝素蛋白的生物相容性,在紫外光照射下呈橙色,无明显细胞毒性,特别适合用作生物标记材料。以上研究成果有望应用于生物医用领域。3.纳米半导体/天然光子晶体新型复合光子晶体的研究在上述纳米半导体/蚕丝丝素纤维固态复合材料工作的基础上,选用常规手段无法获得的精细天然光子晶体结构作为固态生物模板,引导光功能纳米颗粒的合成和有序组装,构成对可见光有优异调控功能的新型纳米复合光子晶体,探索自然的启示对制备固态纳米光学器件的借鉴作用。设计了一条较为温和的制备工艺,获得了纳米氧化锌/孔雀羽毛复合材料。制备过程中利用了孔雀羽毛本身的活性位点,得到的氧化锌为六方相纳米颗粒,分布均匀,粒径随溶剂热反应时间的延长而增加,变化范围是8.5~13.5 nm。受羽毛角蛋白与氧化锌间相互作用的影响,所得氧化锌的荧光发射主要为位于可见光范围的缺陷发光。设计了一条“活化-原位反应-溶剂热”制备工艺,获得了纳米硫化镉/天然光子晶体新型复合光子晶体。制备过程中,天然光子晶体先经活化处理增加活性位点,再引导硫化镉种子的原位合成和纳米颗粒的有序组装,最后作为固态载体使产物无需基片便可自支撑。得到的硫化镉主要为立方相,粒径约6 nm。复合材料的形貌可通过选取不同样式的天然光子晶体和调节工艺参数,分别在光子晶体结构尺度(>100 nm)和纳米硫化镉小团簇尺度(<100 nm)进行调节。所获新型复合光子晶体对可见光有优异的调控功能,其反射性质不仅继承了天然生物结构随光子晶体结构样式、参数和观测角度可控的特性,还表现出随纳米硫化镉负载量而变的特征,即较长波段的相对反射强度随负载量的增加而下降。此外,纳米硫化镉/孔雀羽毛二维复合光子晶体的反射光谱揭示了纳米硫化镉与天然光子晶体之间的光学耦合作用,纳米硫化镉/巴黎翠凤蝶一维复合光子晶体的反射性质遵循典型一维光子晶体的特征,纳米硫化镉/异型紫斑蝶准一维复合光子晶体表现出独特的精细结构和新颖的“显色-失色”反射现象。反射光谱的初步模拟结果与实验吻合较好。以上研究结果为光子晶体研究领域提供了新型复合体系——纳米半导体/天然光子晶体,以及设计灵感。综上所述,本论文系统研究了以天然生物材料为基体合成半导体纳米颗粒,构成新型光功能纳米材料的工艺,以及纳米半导体/生物基体复合材料的光学性质。证实了生物组分的活性和生物相容性对制备纳米材料的有利影响,发现了复合材料中半导体纳米颗粒与生物精细结构之间的光学耦合作用,并且实现了常规手段难以获得的微纳米有序结构和可控光学性质。本论文的研究成果为光功能材料的设计和制备提供了新思路和新方法。更多还原

【Abstract】 Optical nanomaterials are widely used in biology, medical, computer science, and so on. Usually, optical nanoparticles are combined with matrix materials, like modification components and substrate structures, in order to obtain smart and multifunctional nanocomposites. However, there are some problems in dealing with these nanocomposites, for instance, the synthesis of nanoparticles requires harsh conditions, the hybridization process is complicated, and the pattern of nanostructures is limited. In this field, nature has some valuable solutions via millions of years’evolution. One is biocomponents: the active biocomponents in organisms could direct the synthesis and assembly of nanoparticles under mild environment, and form natural nanocomposites with excellent properties. The other is biostructures: nature has created all kinds of multifunctional biostructures, some of which are still hardly achieved artificially. Inspired by nature, people directly take biomasses as the templates to fabricate novel functional materials. Since biocomponents and biostructures have several advantages, the bio-inspired idea is supposed to accomplish simplified fabrication routes as well as novel functional materials with subtle nanostructures and attracting properties.Based on these investigations, we suggest that biomasses can serve as the templates to fabricate optical nanomaterials. Owing to the active biocomponents and subtle structures of biomasses, this process might give a solution to the above mentioned problems. In detail, active biocomponents can direct the synthesis and assembly of nanoparticles, which simplify the fabrication process. Then, they may modify the nanoparticles to improve the biocompatibilities. And the subtle biostructures could provide solid substrates and give additional optical properties to the final products. Therefore, the bio-inspired fabrication of optical nanocomposites would bring new opportunities to functional materials. The main contents and results are as follows:1. In situ synthesis of chalcogenide nanoparticles on silk fibroin fibers Reactive silk fibroin fibers (SFF) were chosen as the biotemplates to direct the in situ synthesis and assembly of the typical optical materials CdS nanoparticles (nano-CdS), in order to investigate whether the bio-inspired fabrication route is suitable for optical nanomaterials.We proposed a room-temperature facile process to synthesize and assemble nano-CdS on SFF, producing solid products nano-CdS/SFF and liquid products nano-CdS/silk fibroin (SF) dispersed in CaCl2 solution. During the process, SFF provided reactive sites, served as solid substrate, as well as assembled nanoparticles. As-prepared CdS were hexagonal phase nanocrystallites with diameters that proportional to the immersing time and inverse proportional to the S-precursor concentration (range: 3.8~7.9 nm). Nano-CdS could be assembled into nanoparticle strings and hexagons by SFF, which was also influenced by the immersing time and S-precursor concentration. The optical properties of the nanocomposites can be controlled by the nanoparticles’size and assembly patterns. The absorption edge and the band-edge fluorescence emission of the products were blue-shifted as nano-CdS became smaller. CdS nanoparticle strings performed fluorescence emission similar to that of separate nano-CdS, while CdS nanoparticle hexagons displayed red-shifted and broadened fluorescence emission compared with that of separate nano-CdS. This investigation demonstrated that it is possible to in situ synthesize and assemble nano-CdS on SFF under mild condition, which was the basis of the flowing works.2. Oxide nanoparticles/SFF(SF) biocompatible optical nanocomposites Based on the investigation of chalcogenide nanoparticles/SFF nanocomposites, the bio-inspired process was further introduced to fabricate optical nanocomposites with potential applications in biomedical fields. In this case, we used SFF to direct the fabrication of nano-ZnO, which were chosen for their nontoxicity and long wavelength visible photoluminescence. Then, as prepared nano-ZnO were directly modified by biocompatible SF. We proposed a facile route to obtain solid products nano-ZnO/SFF and liquid products nano-ZnO/SF. During the process, SFF provided reactive sites, served as solid substrate, as well as controlled the shape and defects of nanoparticles, while experimental conditions influenced the distribution of nano-ZnO. As-prepared ZnO were mainly hexagonal phase spherical nanoparticles with average diameter around 13 nm. The solid products appeared white under sunlight, and emitted orange-yellow phosphorescence centered around 600 nm with persisting time >0.1 ms under the UV excitation <370 nm. Their UV resistance was better than original SFF’s. The liquid products combined the optical functionalities of nano-ZnO as well as the biocompatibilities of SF. They displayed orange under UV illumination, and didn’t perform distinct cytotoxicity. Thus, nano-ZnO/SF might be used as bioimage labels. The above investigations have potential applications in biomedical fields.3. Semiconductor nanoparticles/natural photonic crystals novel nanocomposite photonic crystalsBased on the experience of using solid biomasses SFF to synthesize semiconductor nanoparticles, the bio-inspired process was further introduced to fabricate novel nanocomposite photonic crystals (PhCs) with potential applications in nanoscaled optical devices. In this case, unobtainable subtle natural PhC structures were taken as the solid biotemplates to direct the synthesis and ordered assembly of optical nanoparticles, which resulted in novel nanocomposite PhCs with superior abilities of controlling visible light.We proposed a relatively facile route to obtain nano-ZnO/feathers nanocomposites. During the process, the original active sites of feathers played important role to form homogeneously distributed hexagonal phase nano-ZnO. The particle size was proportional to the solvothermal reaction time (range: 8.5 to 13.5 nm). Due to the interaction between nanoparticle and feather keratin, nano-ZnO performed a visible defect emission. Also, we proposed the“activation-in situ synthesis-solvothermal”fabrication route to obtain nano-CdS/natural PhCs. During the process, natural PhCs gained additional active sites by the activation step, then directed the in situ synthesis of CdS seeds and ordered assembly of nano-CdS, finally provided solid substrate for the self-sustainable products. As-prepared nano-CdS were mainly cubic phase nanocrystallites with diameter around 6 nm. By taking diverse scales and adjusting procedure factors, the assembly patterns of nano-CdS/wings could be controlled at two levels: one was the PhC structures (>100 nm), the other was the nano-CdS small clusters (<100 nm). The obtained novel nanocomposite PhC had superior abilities of controlling visible light. Their reflection properties could be tuned by changing PhC styles and parameters, as well as detecting directions, which were inherited from natural PhCs. In addition, they were also influenced by nano-CdS loading amounts. The reflectance at longer wavelength decreased as nano-CdS loading amounts increased. Moreover, the reflection spectra of nano-CdS/feathers 2D nanocomposite PhCs revealed the optical interaction between nano-CdS and natural PhCs. The reflection properties of nano-CdS/Papilio Paris butterfly matched the features of typical 1D PhCs. Nano-CdS/Euploea mulciber butterfly displayed subtle structures and attractive“shining-dim”phenomenon. In addition, the primary simulations of the reflection spectra agreed with the experimental results. The above investigations provided novel composite systems“semiconductor nanoparticles/ natural PhCs”as well as design inspirations to the PhCs research fields.In this thesis, we systematically investigated the bio-inspired synthesis and optical properties of the novel optical nanocomposites constructed by natural biomasses and semiconductor nanoparticles. It is proven that the active and biocompatible components in natural biomasses could facilitate the fabrication of nanomaterials. And it is observed that the optical interaction between nano-CdS and natural PhCs exists in the nanocomposites. Moreover, it is achieved that as-prepared nanocomposites perform ordered nanostructures and specific optical properties that are hardly obtained by usual way. This work provides new ideas and new solutions to the design and fabrication of functional nanocomposites.更多还原