【作者】 张道军；

【导师】 霍启升；

【作者基本信息】 吉林大学 ， 无机化学， 2011， 博士

【摘要】 由于稀土离子具有相当丰富的能级和4f电子的跃迁特性,使稀土基发光材料成为一类非常重要的功能材料。稀土离子的f-f跃迁是Laporte禁阻的,故其摩尔吸光系数很小,直接吸收光的能力很弱,一般采用具有生色团的有机分子与稀土离子螫合,生成稀土配合物,通过生色团的“天线效应”把吸收的能量传递给稀土离子,敏化稀土离子发光。稀土配合物的这种f-f跃迁发射大多属于能量转移型荧光,稀土配合物具有发光单色性能好、发光效率高、寿命长等优点,是优良的发光材料,在荧光体、显示、细胞成像、闪烁体、激光和光纤放大等领域有着广泛的应用。单一的稀土发光配合物还是有相当的局限性(热稳定性、光稳定性和不易加工性等),而稀土基有机—无机杂化发光材料在一定程度上能摆脱这些缺点。设计和合成具有良好性能的稀土杂化发光材料在近十多年来一直引起相关化学工作者的关注,并且随着晶体工程学、纳米化学和超分子化学的飞速发展,为稀土有机—无机杂化发光材料提出了更高的要求。目前稀土有机—无机杂化发光材料的普遍研究是基于硅基化合物(包括硅酸盐、二氧化硅、介孔二氧化硅和介孔有机硅等)形成的无机或有机—无机框(骨)架上构筑(引入)稀土配合物发光中心,另外,也有一些不同构筑方式的新型杂化发光材料和新颖的无机基质得到不同程度的开发,包括微孔分子筛基质、层状化合物基质、纳米粒子基质(磁性纳米粒子、金纳米粒子、稀土纳米粒子、介孔纳米粒子等),碳纳米管等。除此之外,稀土有机—无机杂化发光多孔晶体材料(稀土金属—有机骨架发光配合物)作为一类新型的稀土杂化发光材料最近也有蓬勃发展的趋势。众所周知,纳米材料有着区别于传统块体材料和粉末材料的性质和优点。纳米杂化发光材料也不例外。鉴于这些原因,本论文集中于稀土有机—无机杂化纳米发光材料的制备与发光性能研究。本论文采用了不同的设计思路和合成方法合成或组装出不同体系的稀土有机—无机杂化纳米发光材料,并对其性质进行了表征。选用的无机基底主要有介孔二氧化硅纳米粒子,稀土杂化胶体粒子,稀土纳米粒子和具有纳米空穴的类分子筛金属—有机骨架化合物等,主要研究了下转换发光,上转换发光,近红外发光,白光,颜色可调发光材料以及荧光探针等性质。本论文主要研究内容如下：1.基于二氧化硅介孔纳米粒子稀土配合物复合发光材料合成研究介孔SiO2纳米粒子集中了纳米材料和多孔材料于一体的特点,并且SiO2具有毒副作用小,生物相容性好,易于修饰等优点。本论文以介孔SiO2纳米粒子为基底,通过开发合适的稀土敏化配体,控制稀土中心(Tb, Eu)的饱和(9配位环境)配位,以减少水或其它溶剂对稀土发光的非辐射猝灭作用等方面进行了相关研究,并取得了一些成果。(1)以4,5-咪唑二羧酸和苯并咪唑-5,6-二羧酸为配体构筑的稀土金属—有机配位聚合物有着良好的发光性能,可见这两种配体对稀土有着好的敏化效果。基于此通过适当的有机硅烷偶联剂连接敏化配体,通过后嫁接方法将其共价键连接到介孔纳米粒子上,合成多功能复合材料Eu-idc-Si-MSNs和Tb-bidc-Si-MSNs,这两种杂化材料分别呈现出良好的红光和绿光。研究表明这两种配体能够很好的敏化稀土发光,这种纳米体系的介孔发光材料在药物释放和生物标记方面有着潜在的应用价值。(2)2,6-吡啶二甲酸能够很好的敏化稀土Eu和Tb,通过对其4位上进行适当修饰,共价键连接到介孔纳米粒子表面,控制稀土中心与配体的9配位环境,得到杂化Eu-dpa-Si-MSNs和Tb-dpa-Si-MSNs,减少了配位水对稀土发光的非辐射猝灭作用,因此其在水中有着良好的发光效果。该杂化纳米材料在500℃反应3 h,冷却至室温后,用紫外光激发得到的光谱,仍然能示出Eu3+和Tb3+的红光和绿光特征锐线光谱,并且在400～750 nm有一个宽阔的谱带,这可能归结于主体介孔SiO2骨架体系中的杂质和生成的缺陷引起的发光。热处理后材料的CIE色坐标显示了全紫外光(240-380nm)激发下,荧光颜色始终保持近纯白色。这为制备白光纳米材料提供了有益的思路。2.有机配体复合敏化无机稀土胶体粒子的合成与光学性质表征(1)快速简单的方法制备Tb(OH)CO3@X杂化胶体发光粒子(X代表水杨酸类敏化剂)。稀土有机—无机杂化胶体粒子的研究有限,合成方法也比较复杂。因此亟需寻求快捷的方法制备发光性能良好的杂化胶体粒子。铽(Tb)配合物由于具有窄的发射谱带、高的发光强度和长的荧光寿命,可以应用在显示器、生物识别和荧光探针等方面。另外,中心稀土离子的特征发射必须通过有机配体的三重态能级将能量传递到稀土离子。由于Tb3+离子的共振能级约为20500 cm-1,与芳香羧酸类配体(如磺基水杨酸)的三重态能级相匹配完好,因此水杨酸类配体的铽配合物展现出优良的荧光性能。以硝酸铽为反应物,尿素为均相沉淀剂,采用尿素均相沉淀法合成Tb(OH)CO3胶体粒子,考虑到得到的Tb(OH)CO3一般为无定形粒子,在原位合成胶体粒子的同时加入少许的Tb的敏化剂(水杨酸,氨基水杨酸和磺基水杨酸),这样敏化剂就会包裹于无定形Tb(OH)CO3胶体粒子的内部或者配位吸附于粒子的外表面,Tb(OH)CO3起到两个作用,其一是作为主体骨架结构,其二是提供稀土发光中心Tb3+。制备得到的Tb(OH)CO3@X胶体粒子在紫外灯照射下都显示出肉眼可见的明亮的绿光,研究表明包覆水杨酸敏化配体得到的杂化材料发光性能最好,添加不同的敏化剂能够影响胶体粒子的形貌和结晶状态,并且研究了Tb(OH)CO3@X,rhB体系的荧光共振能量转移现象。(2)以介孔SiO2纳米粒子为模板合成核壳发光材料,并且研究了有机敏化剂对核壳发光材料光增强效果。单分散的介孔SiO2纳米粒子可以作为其它纳米材料的硬模板,与单分散的SiO2相比,其优点是内部孔道和外部表面都可以作为模板反应的场所,是制备核壳材料的优良载体。以介孔SiO2为模板,采用均匀沉淀方法在介孔表面沉积一薄层RE(OH)CO3,高温处理后得到MSNs@RE203。其中,得到的MSNs@ Y2O3:Eu,Er同时显示出可见区红光和近红外区发光。利用敏化配体构筑的稀土发光配合物一直是一个研究热点,然而这种策略也有其内在的局限性,稀土发光中心容易被其周围配体的高能振子(如-OH、-NH和-CH等)猝灭。运用MSNs做模板合成MSNs@Gd2O3:Eu,为了增强红光强度,在粒子表面配位一层敏化配体dpa,得到MSNs@Gd2O3:Eu-dpa杂化材料。研究表明发光强度增强了5.2倍,并且谱线的半峰宽变窄,光谱色度变纯,这种特殊的有机—无机杂化发光材料可能兼备有机敏化和无机基质保护两方面的优点,为制备杂化纳米发光材料提供了新思路。3.颜色可调类分子筛金属—有机骨架主客体发光材料的设计合成近年来,有机—无机杂化配位聚合物作为一种新型的多孔材料引起了人们的广泛关注。人们将这种配合物定义为金属—有机类分子筛,其孔穴处在纳米的数量级,又称纳米微孔配位聚合物。目前,设计和组装Ln-MOFs显得很重要,Ln-MOFs发光材料也得到一些开发,但是到目前为止具有颜色可调的稀土发光材料还没得到多少注意。我们展示一个新颖的方法构建颜色可调的类分子筛金属—有机骨架材料,策略是运用离子交换的方法在ZMOFs骨架中引入稀土离子,主体骨架的激发态能量能够有效的转移给客体稀土离子。选用具有阴离子骨架[In48(HImDC)96]48-的rho-ZMOFs,骨架中存在48个质子化的DMA+,具有良好的离子交换能力。我们最近的研究表明,rho-ZMOFs展示出良好的蓝光发射,另一方面H3ImDC能够好的敏化稀土Eu3+和Tb2+,大约纳米大小的空穴,这样一个距离理论上也能够使主体的能量较好的转移给客体离子。控制交换的稀土发光中心Eu3+(红光)和Tb3+(绿光)的比例,主体骨架能够很好的敏化客体稀土发光(主体骨架到客体离子的有效的能量转移),根据三基色原理展示了一个颜色可调的ZMOFs。我们可以在宽范围内调变材料的颜色(blue, green, white和red),通过稀土阳离子的量和调变激发波长甚至能调制出白光。更多还原

【Abstract】 Lanthanide complexes are a class of useful luminophores because they exhibit high quantum efficiency, sharp and intense emission lines, long life-times and high color purity under ultraviolet excitation, through protecting metal ions from vibrational quenching and increasing light absorption cross section by the well-known "antenna effect". However, they have not so far been used extensively in practical applications as phosphor devices mainly due to their poor thermal stabilities and low mechanical strength. Many lanthanide complexes have been incorporated into solid matrices, such as sol-gel-derived hybrid materials and mesoporous silica materials. Incorporation of lanthanide complexes into these matrices has not only improved the photo and thermal stabilities of the complexes, but also avoided the self-quenching resulting from the concentration effect. In this thesis, our research is focused on the synthesis of lanthanide-based organic-inorganic hybrid nano-phosphors, and the hybrid solid matrices include mesoporous silica nanoparticles, organic-inorganic hybrid colloidal particles, rare earth oxide nanoparticles and nanoporous zeolite-like metal-organic frameworks (ZMOFs).1. Lanthanide(Ⅲ) (Eu and Tb)-imidazoledicarboxylic acid complexes were immobilized on colloidal mesoporous silica with diameter smaller than 100nm by covalent bond grafting technique and uniform and monodisperse luminescent Eu-idc-Si and Tb-bidc-Si functionalized mesoporous silica hybrid nano-materials (MSNs) were obtained. The lanthanide(Ⅲ) complexes-functionalized MSNs were characterized by fluorescence spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and powder X-ray diffraction. The hybrid nano-materials Eu-idc-Si and Tb-bidc-Si functionalized MSNs show strong red and green photoluminescence upon irradiation with ultraviolet light, respectively. Both hybrid nano-materials exhibit long life-times. The mesoporous silica nanoparticles are stable colloid and may have some advantages for potential applications in drug delivery or optical imaging.2. We chose dipicolinic acid as a tridentate chelating units featuring ONO donors reacting with lanthanide(Ⅲ) ions to yield tight and protective N3O6 environments around the lanthanide(Ⅲ) ions, and immobilized lanthanide(Ⅲ)-dipicolinic acid complexes on colloidal mesoporous silica with diameter smaller than 100 nm by covalent bond grafting technique and obtained nearly monodisperse luminescent Eu-dpa-Si and Tb-dpa-Si functionalized hybrid mesoporous silica nanomaterials. The hybrid mesoporous silica nanoparticles exhibit intense emission lines upon UV-light irradiation, owing to the effective intramolecular energy transfer from the chromophore to the central lanthanidc Eu3+ and Tb3+ ions. The photoluminescence of colloidal mesoporous silica nanoparticles in water and ethanol is stable and may have some advantages for the potential applications of MSN-based luminescent nanomaterials in multifunctional optical imaging. Furthermore, the functionalized nano-materials MSNs after heat treatment exhibited a nearly white emission under UV irradiation, which might present a new way to create white emission materials.3. A general one-step route has been developed for the synthesis of rare-earth inorganic-organic hybrid colloidal (submicro-and nanospheres) particles. This kind of organic-inorganic hybrid colloidal particles can be prepared with a wide diversity of metal ions and organic ligands. The results show that organic-inorganic hybrid colloidal particles can be used as functional matrices for the encapsulation of a large variety of substances. Therefore, it is expected that this encapsulation approach will be extended to obtain amorphous/crystalline organic-inorganic hybrid particles that have novel functionalities. The combination of these capabilities with the encapsulated species open up new avenues in various fields, such as cell biology, drug delivery, diagnostics, and so on. Furthermore, the size of the colloidal particles can be controlled precisely and self-assembled into a photonic crystal.4. We present a new way to create color kinetic zeolite-like metal-organic frameworks by efficient energy transfer between host frameworks and guest lanthanide ions via ionic exchange. The tunable color emission is excited via energy transfer from H3ImDC ligands that upon filling the zeolite nanochannels act as light harvesting antenna. Furthermore, we can tune the luminescence color over a wide range (blue, green, white and red) by varying the amounts of the rare-earth cations and tailoring the excitation wavelength.更多还原