【作者】 王振轩；

【导师】 武利民；

【作者基本信息】 复旦大学 ， 材料物理与化学， 2008， 博士

【摘要】 在有着各种形态和结构的低维无机材料制备中,具有空心纳米结构的新型材料正越来越引起广泛的关注并得到长足的发展。这类材料在光学器件、药物传输、活性胶囊、离子插层、长效催化/负载、表面功能化以及尺寸选择性反应等方面都有广泛的应用。然而对于制备零维金属空球和一维非圆形纳米管方面,进展却很有限。基于这种情况,我们就单质银空球和方形三氧化钨纳米管的制备作了一些尝试性的创新工作。具体研究内容和结果如下:（1）以相变乳液为模板,制备出了单分散银质空球。这种模板的前期阶段被通过简单的乳化过程而得到,然后乳液中的油相（这里我们选用的是蜂蜡）在超声场中凝固成硬模板。在相变过程中,AgBr粒子作为Pickering乳化剂与CTAB共同稳定相变乳液。相变结束后得到AgBr粒子包覆的固体乳胶粒子,其数均直径为160.5nm,多分散指数为1.046。接下来,AgBr粒子被通过一种“照相化学”的方法还原成单质银粒子。当更多的AgNO₃加入到反应体系,初始形成的单质银粒子此时作为固体催化剂催化还原处于它周围的银离子,直到固体乳胶粒子被完全包覆。固体乳胶粒子周围的银壳厚度可以通过控制AgNO₃的加入量而进行方便地调节。最后,银壳下的蜂蜡核被热乙醇溶出,并被收集提纯以循环利用。因为蜂蜡是多种小分子的聚集体,它可以被有效的从银壳孔隙中溶出,在实验过程中未发现银壳的塌缩和破裂。该方法结合了软模板方法（容易获得模板）和硬模板法（在反应过程中微球不易产生变形,且对反应环境不敏感）的优点。此外,反应结束后,蜂蜡能被方便地回收,避免了模板溶出后对环境的污染,因此该方法是一种环境友好的方法（2）我们在插层PANI的帮助下制备了WO₃.H₂O方形纳米管。首先,采用双乳液法制备了WO₃.H₂O纳米片和PANI分子,在WO₃.H₂O纳米片的形成过程过程中,同时质子化的聚苯胺分子通过离子交换对WO₃.H₂O纳米片实现了插层。然后我们选择形态规则的纳米片作为前驱物,在60℃密闭反应六天,结果显示纳米片卷曲为纳米管。根据在不同反应时间段的XRD分析,可以得出WO₃.H₂O纳米片的层间距不断减小的结论;而TGA数据表明这种减小并不是因为WO₃.H₂O结晶水或层间PANI分子的脱除;但是通过FTIR分析,我们发现PANI分子在层间被原位氧化,这种氧化所带来的构象和构型的变化又被UV-vis-near IR分析所证明。在一系列的对比试验后,证实了APS对PANI分子的氧化是卷曲的驱动力,而驱动是通过层间PANI分子构象或构型改变所引起的分子链转动来实现的。在PANI分子和WO₃.H₂O纳米片的协同运动下,PANI分子实现了卷曲形态向平板形态的转变,而WO₃.H₂O纳米片也同时卷曲为管。这种制备纳米管的方法最大的特点在于制备过程的比较温和,且纳米片直接卷曲成管而无需经历“纳米卷轴”阶段。通过该方法制备的WO₃.H₂O纳米管的磁化率在90K时,迅速由正值变为负值。这个有趣的现象与普通的PANI和WO₃.H₂O都不相同,这暗示着WO₃.H₂O纳米管在电磁器件方面可能有潜在的应用。更多还原

【Abstract】 Among the many lower-dimension inorganic materials with distinct structural and geometrical features, freestanding hollow micro-, meso-, and nanostructures represent an important class of novel materials attracting special interest, due to their potential scale-dependent applications such as in photonic devices, drug delivery, active material encapsulation, ionic intercalation, surface functionalization, robust catalysts/carriers, and size-selective reactions. However, there has been only little progress in the synthesis of one-dimension noncircular nanotubes and zero-dimension metal hollow sphere, particularly in hollow silver spheres and rectangular nanotubes. Based on the current situation, we attempt some new methods to prepared hollow silver spheres and rectangular tungstic oxide nanotubes. The detail research contents and results are summarized as follows:（1） Monodisperse hollow silver spheres were synthesized by using phase-change emulsion as template. The preceeding state of this template could be obtained via simple emulsification like the soft-template method, and then the oil-phase （here we select beeswax） underwent coagulation process to achieve a kind of hard-template under ultrasonic treatment. It is proposed that AgBr "seeds" （precursor of silver nanoparticle） here performed a role of Pickering emulsifier. They successfully cooperated with CTAB molecules to stabilize the emulsions during the phase transition. The mean diameter of the resultant AgBr-coated solid emulsion beads is 160.5nm and the polydispersity index is 1.046. AgBr "seeds" were sequently reduced to form silver particles just like in the standard photographic procedure. When more silver nitrate solution was added, primary silver particles make silver ions around them initiated catalytic reduction until the integrated silver shell was completed. The silver wall-thickness can be conveniently modulated through change the content of AgNO₃. Our results show that not only is this approach simple but also the removal of the template is high efficient since beeswax is a aggregate of multiple small molecules which are easily transfer from inside to outside. Moreover, the natural beeswax template can be recycled, so the whole process is environmentally friendly.（2） We prepare rectangular WO₃.H₂O nanotubes by the aid of intercalated PANI. Firstly, as compared to conventional synthetic process of intercalated materials, the oxidative polymerization of aniline and the intercalation of nanosheets formed at the same time along with concomitant ion exchange by means of double-emulsion method. We choose the resultant uniform nanosheets as precusor followed by continuous stirring for six days at 60℃. According to different morphologies we observed at different reaction time stage, we found PNAI-intercalated WO₃.H₂O nanosheets rolling into nanotubes. Furthermore, we also found the corresponding interlayer distances of WO₃.H₂O layers decreases as the reaction time is increased. FTIR data indicates that the degree of in-situ oxidation of PANI increased with increasing reaction time. At the same time, UV/Vis-near IR monitors polymer conformational change between layers. So the decreases of interlayer distances depicted in XRD could not be ascribed to water loss or emigration of PANI from a kinetic point of view but to change of configuration in PANI under oxidation. Further, this change in cross-sectional area and arrangement of PANI also bring out curling movement of WO₃.H₂O layers. The uniqueness of this method is that not only the preparation is made under a relatively mild condition, but also the nanosheets directly roll into rectangular cross-sectional nanotubes without suffering nanoscrolls stage.The reciprocal magnetic susceptibility of PANI-intercalated WO₃.H₂O nanotubes rapidly decreased from positive to negative at 90k, which endowed them with potential material for electromagnetic device.更多还原