【作者】 常雪灵；

【导师】 杨祥良； 徐辉碧；

【作者基本信息】 华中科技大学 ， 生物医学工程， 2007， 博士

【摘要】 近年来,由于小分子有机凝胶因子可以通过分子自组装形成有机凝胶超分子结构,并在纳米无机材料制备过程中独特的模板效应,使其在超分子化学和无机材料领域的应用得到了蓬勃发展。在本论文中,合成了具有优良凝胶能力的小分子有机凝胶因子双硬脂酰胺二苯甲烷(BSAPM),以此有机凝胶自组装结构为模板成功诱导形成纳米结构的二氧化硅,考察了阳离子表面活性剂、金属盐、二氧化硅前驱体以及pH等条件对有机凝胶模板效应的影响,并对纳米结构二氧化硅的荧光性质进行了研究,此外,采用变温光谱学对有机凝胶中的氢键和π-π叠加等作用力进行了初步探索。论文的主要结果如下:1.合成了有机凝胶因子1、2、3,采用FTIR、1H NMR、MS对有机凝胶因子1(双硬脂酰氨二苯基甲烷,BSAPM)进行了结构表征。对有机凝胶因子1、2、3的凝胶能力进行了评价,有机凝胶因子1 (BSAPM)甚至在浓度低于1 wt %的情况下使许多溶剂凝胶化,表现出优良的凝胶能力,尤其可以使质子惰性溶剂二甲基亚砜(DMSO)、N,N-二甲基甲酰胺(DMF)、苯、二甲苯等发生凝胶化,并且对三个碳以上的烷醇也表现出良好的凝胶效果。采用DSC对在正丁醇中有机凝胶因子1、2、3形成凝胶的相转变温度(Tgel)进行了测定,结果发现其相转变温度随有机凝胶因子分子结构的不同而发生变化,其中BSAPM正丁醇凝胶的Tgel (66℃)最低,形成的凝胶比较稳定。考察了正丁醇、二甲苯、DMF和DMSO四种溶剂和有机凝胶因子浓度对BSAPM有机凝胶Tgel的影响,结果发现四种溶剂的BSAPM有机凝胶,其Tgel随溶剂沸点的升高而升高;有机凝胶因子BSAPM在浓度(1-5 wt %)的范围内,其正丁醇凝胶的Tgel随浓度的增大而升高。这些表明有机凝胶的Tgel,受有机凝胶因子的分子结构、凝胶化的溶剂及有机凝胶因子的浓度等诸多因素影响,并呈现一定的规律性变化,其中溶剂对有机凝胶的Tgel改变影响最大。2.采用SEM、TEM、AFM观察,以BSAPM为模板诱导制备了棒状、片状、管状和颗粒状等纳米结构的二氧化硅。在有机凝胶模板制备过程中,通过改变凝胶化溶剂、SiO2前驱体及添加阳离子表面活性剂、金属盐等,制备了形态可控的纳米SiO2。在正丁醇和质子惰性溶剂二甲苯、DMSO、DMF溶剂中成功地诱导制备了纤维束聚集体、棒状、卷曲状和薄片状的纳米结构SiO2,对凝胶因子BSAPM,仅通过改变溶剂,即可简单、方便的制备不同形态的二氧化硅。硅烷偶联剂A-1891改变了SiO2前驱体,可以制备形状均匀、表面光滑、直径约为100 nm、长几个微米的纳米棒。CTAB阳离子电荷密度的增大,使二氧化硅的形态发生了从纤维聚集-片状叠加-片状弯曲-管状的变化,说明阳离子电荷的密度是纤维束聚集、相互联结最终卷曲形成管状的关键因素,与文献报道的结论相符。硝酸铜存在时,易形成结晶体,破坏了有机凝胶的模板效应。此外,煅烧温度以及凝胶因子浓度在一定范围内的变化对SiO2的形态改变影响不大,而pH的变化直接影响正硅酸乙酯(TEOS)的水解聚合,从而影响纳米SiO2的制备。3.此类小分子有机凝胶模板法制备的纳米SiO2具有荧光性质。荧光显微镜观察,纳米SiO2固体粉末经紫外波段(330-380 nm)激发可以发射强烈而稳定的蓝色荧光,经蓝色(450-480 nm)和绿色波段(510-550 nm)激发分别发射相对较弱的绿色、红色荧光。荧光光谱测定,其最大激发波长Ex=261 nm,最大发射波长Em=365 nm,激发光谱峰形对称,发射光谱峰以365 nm为主要发射峰,并且在279和304 nm具有弱的窄发射峰。对不同SiO2前驱体获得的纳米结构SiO2,其荧光光谱的激发和发射波长略微不同。纳米SiO2经IR和XRD测定,均表明为无定形的结构,BET测试比表面积为148.51 m2/g,存在10-30 nm和1000-2000 nm两种孔径,以孔径较小的为主。XPS结果显示O与Si的原子摩尔数之比为2:1,主要以SiO2的形式存在,Si2p1/2 (103.87 eV)与Si2p3/2 (103.08 eV)的峰面积之比约为1:1.4,意味着纳米SiO2表面存在Si-的悬挂键。纳米SiO2的荧光性质可能与其纳米结构及表面Si-悬挂键的存在有关。4.利用变温红外、紫外、荧光等光谱对BSAPM正丁醇凝胶的形成机制进行研究。结果表明BSAPM正丁醇凝胶主要是通过氢键协同π-π叠加作用力形成,此凝胶的温度稳定区间为5-25℃。变温紫外、荧光光谱是研究芳香族有机凝胶因子π-π共轭的重要手段,同时变温红外光谱也显示了其特征振动光谱。5.利用变温红外光谱初步探讨了BSAPM分别在六种溶剂中形成凝胶的氢键和π-π共轭叠加作用力的强度变化趋势,其微弱变化可以显著改变BSAPM有机凝胶的聚集形态。六种BSAPM有机凝胶主要是以氢键为驱动力,π-π叠加作用协同而形成的,其中氢键作用力的大小可能决定凝胶聚集纤维束的连结、扭曲或卷曲。另外,有机凝胶聚集形态也因有机凝胶因子分子结构的变化而不同,有机凝胶因子2疏水链中双键的引入使聚集纤维束扭曲缠结,基于二苯砜的有机凝胶因子3可以形成纳米管。本文主要研究了小分子有机凝胶模板结构诱导制备形态可控的纳米二氧化硅,并且发现该模板法制备的纳米二氧化硅具有荧光性质。同时采用变温光谱学进一步探索了模板凝胶的形成机理,以期对这类体系在纳米材料的制备和应用方面具有一定的指导意义。更多还原

【Abstract】 Recently, the use of organic compounds as templates for the generation of inorganic structures and materials has been receiving considerable attention. Low molecular weight organic gelators have become the focus of much attention. The gelator molecules self-assemble to form three-dimensional networks superstructures which are used as versatile building blocks in organogels and as templates for sol-gel transcription into nanostructured silica.In this dissertation, a bis-(4-stearoylaminophenyl) methane (BSAPM) organogelator based on 4, 4’-diaminodiphenylmethane was synthesized and possessed a versatile gelation ability. Multi-morphologic nanostructured SiO2 materials with controlled morphologies were prepared successfully by hydrolysis and polycondensation of a tetraethoxysilane (TEOS) precursor through a sol-gel transcription with the self-assembled organic superstructures of BSAPM as template. The addition of cation surfactant, metal-salt, silica precursor and hydrochloric acid will influence the transcription of the organogel as template. The fluorescence of nanostructured silica transcripted from the template method was investigated. On the other hand, the mainly driver of the aggregation of gelator molecules into fibrous network was studied by variable temperature FTIR spectra method.1. Three organogelators were synthesized and characterized by FTIR, 1H NMR and MS. Their gelation abilities of these gelators were evaluated in organic solvents under 1.0 wt %, indicating that the BSAPM possess a versatile and excellent gelation ability. The gelator BSAPM can gelate protic solvents (such as DMSO, DMF, benzene and toluene, etc) and alkyl alcohols. The phase transition temperatures (Tgel) of these organogels were determined by differential scanning calorimetry (DSC). Tgel of BSAPM gel was increased with concentration increasing of BSAPM gelator in n-butanol and boil point increasing of solvents in different organic solvents (such as n-butanol, xylene, DMF and DMSO). Moreover, the different molecular structure of gelator will lead to changes of Tgel.2. SEM, TEM and AFM observations of these nanostructured silica which transcripted from organogel as templates, showed various morphologies (such as stick-like, flake, tublar and granular, etc.). The nanostructured silica with controlled morphology was obtained by the addition of different solvents, cation surfactant, metal-salt and silica precursor in organogel systems. The silica obtained from n-butanol, xylene, DMSO and DMF had fibrous, stick-like, curly and thin flake nanostructured silica, respectively. All kinds of morphologies silica was obtained simply only by changed solvents in the template method. The silica obtained from n-butanol had changes from fibrous aggregation, flake stack, flake incurvate to tube like and granular with concentration increasing of cation surfactant (CTAB), whereas in the presence of A-1891 had a stick-like structure uniformly featuring the smooth surface and multi-layer wall with diameters of 100 nm and lengths of a few micron. The cationic charge generated by protonation of gelator and surfactant play a crucial role in the creation of such tube and stick like. These results indicate that various and novel silica can be prepared by transcription using various superstructures in one organogel as a template.3. The fluorescence property of nanostructured silica was validated by fluorescence spectrophotometer and microscopy. The blue light emission was stable and intense by ultraviolet excitation (330-380 nm) whereas the green and red emission was weak by blue and green (450-480 nm and 510-550 nm, respectively). The fluorescence spectra of nanostructured silica is Exmax=261 nm, Emmax=365 nm. The excitation curve had a symmetrical distribution. The emission curve had an intense main peak with two weak peaks at 279 nm and 304 nm. The different nanostructured silica has indistinct spectra. And that, the nanostructured silica was amorphous through FTIR, XRD and XPS. The nanostructured silica with two pore size distribution of 10-30 nm and 1000-2000 nm had a BET surface area of 148.51 m2/g. The XPS spectra of nanostructured silica displayed mainly O and Si peaks. Their peaks area revealed that the atomic ratio of O to Si is about 2:1. The spectrum of deconvoluted into multiple sub-peaks of Si2p peak (at103.87 eV, Si2p1/2 and 103.08 eV, Si2p3/2) indicated that nanotubes were composed of silica. The peaks area ratio of Si2p1/2 to Si2p3/2 is about 1:1.4, meaning there were Si- appended bonds in the surface of materials. The Si-O and Si- on the inner and outer surface presumably play an important role in the strong blue light emission of the nanotubes4. The gelation mechanism of BSAPM organogel from n-butanol was studied by FTIR, UV and FL spectra with variable temperature. The rudimental experiments results indicated that the organogel was very stable at 5-25℃and the intermolecular hydrogen-bonded play core role in the gelation process. Presumably, the BSAPM gel structure of 1-butanol system was self-assembled three dimension network mainly by intermolecular hydrogen-bonded cooperating with benzene ringπ-πconjugated. The variable temperature UV and FL spectra were important means for study of gel from gelator with aryl.5. The intensity and trend of hydrogen-bonded was investigated primarily with increasing temperature by FTIR in BSAPM organogels. Their weak changes would affect distinctly the aggregation of gelator. The aggregation of BSAPM molecular into fibrous network was driven mainly by hydrogen-bonded interaction in different gelatinized solvents. The intensity of hydrogen-bonded interaction may be decided to couple and twist between aggregation fibrous. On the other hand, different molecular structure of gelator would generate different aggregation morphologies of organogel. The aggregation fibrous of organogel from n-butanol was twisted owing to introducing one unsaturation of aliphatic alkyl chain in BSAPM gelator molecular structure and the nanotube of organogel from n-butanol was obtained due to 4, 4’-diaminodiphenyl sulphone instead of 4, 4’-diaminodiphenylmethane in BSAPM gelator molecular structure.In summary, the various novel nanostructured silicas with blue fluorescence can be prepared by transcription using various superstructures of the small molecular organogels as a template. The formation mechanism of the organogel superstructures was investigated primarily. It is very important that these results could also be expected to get further investigation and show great advantages for future preparation and application of nanostructured silica.更多还原