【作者】 范迎菊；

【导师】 钱逸泰； 占金华；

【作者基本信息】 山东大学 ， 无机化学， 2009， 博士

【摘要】 本论文主要探讨了利用液相化学法对氧化铟及银纳米结构材料的控制合成。分别从材料制备和表征、形成机制以及性质研究三个方面进行了论述,内容涉及双表面活性剂辅助下亚稳相（corundum-type structure）In₂O₃多级结构的制备、形成机制以及气敏性质;不同形貌的银纳米颗粒的合成及其在汞离子识别方面的应用;以及银掺杂二氧化钛在光催化方面的应用。通过以功能为导向的纳米结构材料的控制合成和性能方面的研究,探索纳米材料的尺寸、形貌等参数对器件应用方面的影响。具体归纳如下:1.亚稳相In₂O₃多级结构的制备及其气敏性能测试将InCl₃·4H₂O溶于正庚烷中,以十二胺和油酸为添加剂,在220℃反应一定时间得到正交晶系InOOH前驱体,然后在常压下对其进行退火处理,InOOH脱水并相转变为六方相In₂O₃多级结构。双表面活性剂对多级结构的形成起了重要作用,在反应最初阶段,由于静电相互作用和疏水链之间的排斥力,阴离子表面活性剂油酸和阳离子表面活性剂十二胺混合后会形成双分子膜。在溶剂热条件下,随着温度的升高和压力的增大,InOOH纳米晶不断成核。表面活性剂和InOOH纳米晶[001]方向形成强的氢键,从而导致了晶粒的一维生长。因此,在双表面活性剂的作用下,颗粒沿着[001]方向定向聚集,形成了InOOH纳米线,纳米线非定向聚集形成稻草捆状多级结构。随着反应时间的延长,纳米线之间二次成核并生长,InOOH多级结构不断分支,新的分支再作为下一级末端继续分叉,使得活性成核点以级数的方式快速增加,经过几级分叉扩增,InOOH逐渐由稻草捆状变为哑铃形,最终生长为毛线球状。十二胺单独存在的条件下,对产品的形貌没有任何调控作用,这可能与十二胺与生长中的InOOH晶面的结合力弱有关系。此外十二胺可以提供In³⁺水解所必需的碱性环境,与氢氧化钠等强碱导致快速水解不同,十二胺作为路易斯碱,可提供一个极弱的碱性环境,这有助于In³⁺的水解温和平缓的进行,对产物的形貌起了关键的作用。该多级结构对2-氯苯酚气体具有快速敏感的传感性能。当2-氯苯酚气体浓度低至5ppm时也具有明显的感应信号,响应和恢复时间分别为55s和47s。多级结构In₂O₃传感器在280℃条件下对苯、甲苯、三氯甲烷、二氯甲烷、氨气均没有任何响应,电阻值几乎没有变化。2.不同形貌纳米银的合成及其在汞离子检测方面的应用银的纳米颗粒是在可溶性淀粉溶液中通过AgNO₃和NaBH₄的还原反应得到。所得银溶胶为鲜艳的黄色,其紫外可见吸收光谱显示出银纳米颗粒的吸收峰位于400nm左右的可见光区。根据朗伯-比尔定律A=Kbc计算,该银纳米粒子在400nm处的摩尔吸收系数为1.3×10⁵ M^-1·cm^-1,可满足比色法检测的需求。利用单质银和汞离子之间能够发生氧化还原反应的原理,室温下,在制备的银纳米粒子中添加不同浓度的Hg²⁺,进行紫外可见吸收光谱检测。随着加入汞离子浓度不断增大,银溶胶的吸光度逐渐减小。这是由于随着反应的不断进行,银颗粒不断被消耗,其浓度逐渐减小,因此吸收峰的强度逐渐降低。银纳米粒子的吸光度和加入的Hg²⁺浓度呈良好的线性关系,其回归方程为A=1.41-5.75×10^-4c(A为吸光度,c为Hg²⁺浓度),线性相关系数为R=0.9984。根据Mie理论和金属自由电子论的Drude模型,对银溶胶的吸光度和浓度之间呈现线性关系进行了公式推导。该方法对Hg²⁺显示出良好的选择性,Na⁺、K⁺、Ba²⁺、Mg²⁺、Ca²⁺、Fe³⁺和Cd²⁺等不会造成较大干扰,实现了在水相中Hg²⁺的检测。利用硼氢化钠和抗坏血酸两种还原剂的合理搭配,在阴离子双链表面活性剂NaAOT的作用下,成功制备了规则纳米银三角片。随着加入Hg²⁺的浓度逐渐增大,银纳米片逐渐由三角形变为截顶的三角,再变为圆片。银三角片和汞离子反应后溶液的最大吸收峰位置的改变量Δλ和Hg²⁺浓度在50ppb-550ppb范围内呈良好的线性关系。3.Ag@TiO₂复合空心球的制备及其光催化性能研究以碳纳米球为模板和还原剂,制备了C@Ag复合结构,碳球表面由于具有还原性基团,可以还原Ag⁺,从而实现Ag纳米颗粒的表面原位沉积。利用钛酸四丁酯的缓慢均匀水解反应常温下对C@Ag进行包覆,碳球表面丰富的羟基有利于钛酸四丁酯的水解,因此水解产物均匀包覆在碳球表面。随后在500℃下焙烧去掉碳球模板,成功合成了Ag@TiO₂空心复合结构,通过改变AgNO₃的浓度,可控制银的负载量。研究发现银的存在有助于光生电子-空穴的快速分离,Ag的Fermi能级低于TiO₂,在每处Ag与纳米TiO₂连接位点形成了肖特基势垒（Schottkybarriers）。Ag能捕获纳米TiO₂产生的光生电子,使光生空穴向TiO₂纳米粒子表面移动,使TiO₂带多余的正电荷,这不但增大了TiO₂纳米粒子表面对带负电的-OH以及亚甲基蓝的吸附;而且纳米TiO₂表面光生空穴（h⁺）浓度提高,有助于光生空穴迅速、有效地与粒子界面吸附OH^-作用,生成·OH,从而提高了其光催化性能。更多还原

【Abstract】 This paper is focused on the controlled synthesis of indium oxide nanostructures through liquid-phase chemistry routes.Investigations are based on three aspects: controlled synthesis,formation mechanism,properties and applications.The contents mainly include metastable corundum-type In₂O₃ of hierarchical nanostructured preparation,size-controlling,formation mechanism and gas-sensing properties, morphosynthesis of Ag nanoparticles and Hg²⁺ Recognition in Aqueous Media, intending to study the intrinsic controlling mechanism of the nanocrystal formation and their effects on the devices’ applications.1.Catanionic-surfactant-controlled morphosynthesis and gas-sensing properties of corundum-type In₂O₃InCl₃-4H₂O was dissolved in heptane,oleic acid and laurylamine were used as the additives.After the solution was heated at 220℃for a setting time,orthorhombic InOOH is separated by centrifugation,indium oxyhydroxide dehydrated to form indium oxides hierarchical nanostructure upon heating.On the basis of the reaction conditions,it is believed that the InOOH wire-bundles in this study are formed mainly via the following sequence.At the initial stage,catanionic-surfactant was obtained by mixing laurylamine and oleic acid,which can induce bilayers due to the electrostatic and hydrophobic interactions.With the increased temperature and pressure,nucleation and growth of the InOOH crystals occur under solvothermal conditions.The surfactants will interact strongly with InOOH crystals by forming hydrogen bonds along the[001]direction,which in turn help one-dimentional growth and prevent side-ripening.Thus,with the assistance of catanionic-surfactant,bundle-like morphology based on nanowires was obtained.Finally,dumbbell-like hierarchical InOOH nanostructures were generated through the outward bending the nanowires by secondary nucleation and growth of new nanowires in each space among the as-grown bundle-like nanostructures.The results suggested that laurylamine alone had no effect on the crystal morphologies of InOOH,possibly due to the weak interaction between laurylamine and growing InOOH crystals.But laurylamine provided the necessary alkaline environment for the hydrolyzing of In³⁺ as well as promote the preferential growth of different crystal planes with the coexistence of oleic acid.Novel gas sensors based on the corundum-type In₂O₃ hierarchical nanostructures exhibited high response and selectivity to 2-chlorophenol at 280℃with a detection limit of about 5 ppm.The response of the sensor to other gases,such as benzene, toluene,CHCl₃,CH₂Cl₂,and ammonia under the operating temperature of 280℃was totally insensitive.So the sensor based on corundum-type In₂O₃ hierarchical structures shows an obvious advantage in selective detection of 2-chlorophenol.2.Synthesis of Ag Nanoparticles and Hg²⁺ Recognition in Aqueous MediaThe silver nanoparticles were obtained through a reduction reaction of silver nitrate with NaBH₄ in the presence of starch.It showed a characteristic peak centered at 400 nm in the visible light area.Calculated according to the Lambert-Beer’s law,the extinction coefficients of the as-prepared silver nanoparticles is about 1.39104 M^-1 cm^-1（at 400 nm）,which can meet the demand of colorimetric sensing detection.The sensitivity of silver nanoparticles toward Hg²⁺ was identified by UV-vis absorption spectra in this work.The sensing begins by adding an aliquot of an aqueous solution of Hg²⁺ at a designated concentration to a solution of the Ag nanoparticles at room temperature.Various concentrations of Hg²⁺ from one stock solution were tested.The absorbance peak of the Ag nanoparticles could be depressed with the increased concentration of Hg²⁺ ion.A linear relationship(y=1.41-5.75×10^-4x,R²=0.9984),stands between the absorbance intensity of the Ag nanoparticles and concentration of Hg²⁺ ion over the range from 10 ppb to 1 ppm at the absorption of 390 nm.The limit of quantification,at a signal-to noise ratio of 3,was down to 5 ppb.the selectivity of this system for Hg²⁺ has been evaluated through testing the response of the assay to various environmentally relevant metal ions,including Hg²⁺,Na⁺,K⁺,Ba²⁺,Mg²⁺,Ca²⁺, Fe³⁺ at a concentration of 10^-4 M.Only the Hg²⁺ sample shows a significant fading relative to that of the blank.The facile synthesis,high stability and high water solubility of the starch-stabilized Ag nanoparticle probes allow a reliable assay performed in aqueous environments.3.Hollow Ag/TiO₂ Nanocomposites with Enhanced Photocatalytic ActivityCarbonaceous microspheres,which serve as the templates,are first prepared from saccharide starting materials by dehydration under hydrothermal conditions.The surface of the spheres is hydrophilic,being functionalized with C=O groups,silver were loaded onto their surfaces by room-temperature surface reduction.The polysaccharide-like hydrophilic surface of the spheres,bearing hydroxyl roups（-OH）, favored the hydrolysis of tetrabutyltitanate.Thus,a shell of TiO₂ precursor formed on the surface.The Fermi level of silver is lower than TiO₂,so a Schottky barrier formed at the metal-semiconductor interface.Investigation dicated that optimized amount of Ag deposits not only acted as electron sinks to enhance the eparation of photoinduced electrons from holes,but also elevated the amount of the surface hydroxyl,leading o the formation of more hydroxyl radicals（·OH） and then the higher photodegradation efficiency to MB solutions.更多还原