兰州大学机构库 >化学化工学院
新型镧系-金属有机框架的设计构筑及其在荧光传感中的应用研究
Alternative TitleDesign and Construction of Novel Lanthanide Metal-Organic Frameworks and Their Applications in Fluorescent Sensors
翟小永
Subtype博士
Thesis Advisor唐瑜
2023-05-30
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学博士
Degree Discipline化学
Keyword镧系-金属有机框架 Lanthanide metal-organic frameworks 比率型荧光传感器 Ratiometric fluorescence sensor 荧光调控 Regulated fluorescence 能量传递 Energy transfer
Abstract

金属有机框架(MOFs)是由金属节点与有机配体自组装形成的一种晶态多孔材料,被广泛用于气体存储与分离、药物递送、催化和传感等领域。MOFs具有可调的拓扑结构、形貌、孔隙尺寸以及限域空间,通过合理选择金属节点与有机配体即可实现其构筑。镧系元素具有量子产率高、荧光寿命长、线状发射、Stokes位移大以及近红外激发或发射等独特的发光特性,因而可用于构筑具有优异发光性能的镧系-金属有机框架(Ln-MOFs)。近年来,具有多发光中心的Ln-MOFs被成功合成,这为比率型荧光传感器提供了新的设计策略。然而,镧系离子(Ln3+)种类是有限的,仅通过变换Ln3+以获得多发光中心的Ln-MOFs限制了其发光性能的多样性和可调性。因此,通过合理设计和合成具有特殊光的有机配体,进而可制备具有高效荧光性质和多发光中心的Ln-MOFs。

本论文设计合成了多种具有不同光功能的桥连有机配体,构筑了三类具有新颖发光性质的Ln-MOFs,系统研究了这些材料的微观结构和内部能量传递过程,并将其应用于比率型荧光传感体系的构筑。

本论文主要分为以下五个部分:

第一章:概括了Ln-MOFs的研究背景及发光机理,重点介绍了Ln-MOFs的设计与合成策略,总结了Ln-MOFs在荧光传感中的应用现状,提出了本论文的研究思路和研究内容。

第二章:基于三苯胺型羧酸配体(H3TCA),制备了一种具有白光发射的混合双金属Ln-MOF (Eu2.2Tb97.8-TCA),该材料可作为新颖的双功能比率型荧光传感器,不仅能用于乙醇中微量水的检测,而且可实现特定范围内的温度传感。我们选用了荧光寿命长且单色性良好的Eu3+和Tb3+作为镧系发光中心,H3TCA用作敏化天线,构筑了Eu2.2Tb97.8-TCA。研究发现,配体和两种Ln3+形成的多发光中心对水和温度具有不同的荧光敏感度。随后,我们深入研究了Eu2.2Tb97.8-TCA对乙醇中微量水的比率型荧光检测特性,并对相关的机理进行了阐释。研究发现,该材料对乙醇中微量水展现了快速(< 20 s)且相对超灵敏(LOD = 0.016% v/v)的响应,并以多种读出方式实现了乙醇中微量水的灵敏可视化检测。其中,基于RGB数值中绿色(G)和红色(R)值,结合智能手机APP(颜色提取器),实现了乙醇中微量水的定量可视化检测,检测限为0.035% v/v。同时我们研究了Eu2.2Tb97.8-TCA的温度传感性质,发现该材料可以在300-380 K范围内监测温度变化,具有线性关系良好、准确度高以及可重复利用等优势。此外,我们发现Eu2.2Tb97.8-TCA也可作为白光发射材料,用作单相UV磷光粉。

第三章:在第二章工作的基础上,为了提升Ln-MOFs的化学稳定性,我们合成了四苯基吡嗪衍生的配体(H4TCPP)。通过溶剂热法构筑了一系列具有新颖结构和高化学稳定性的阴离子型Ln-MOFs,即Ln-TCPP (Ln = Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)。首先,系统研究了Ln-TCPP的微观结构与宏观形貌。晶体学数据表明,它们属于单斜晶系的I2/a空间群。单晶结构表明,Ln3+均是规则的六配位,此外,我们发现在反应过程中DMF分子热分解产生的质子化二甲基铵([(CH3)2NH2]+)与配体中未成键的氧原子形成氢键而稳定地存在于Ln-TCPP的孔道中,以此平衡了框架中的负电荷。其次,我们发现TCPP4-仅能敏化Eu3+,通过共掺杂法引入Tb3+实现了配体和Eu3+的双发射。我们选择Eu0.52Tb0.48-TCPP用于后续研究。一方面基于阳离子交换的设计思路,探究了Ag+调控Ln3+发光的现象和机理。在Eu0.52Tb0.48-TCPP的水悬浮液中,加入足量的Ag+后,配体的发光强度减小到原来的4.2倍,而Eu3+的发光强度增加到原来的2倍,且其发光强度比(I616/I416)从1.44提升到12.1。随后,我们通过理论计算解释了Ag+调控Ln3+发光的机理,以及在能级匹配的前提下,Tb-TCPP中配体不敏化Tb3+的原因。另一方面,我们研究了比率型传感器Eu0.52Tb0.48-TCPP对苦味酸的荧光传感性能和机理。

第四章:在第三章工作的基础上,为了调控Ln-MOF的结构和化学稳定性,我们通过调节配体尺寸合成了新的四苯基吡嗪衍生的“X”型配体(H4L)。通过调控配体及Ln3+的配位方式,利用溶剂热法合成了一系列结构新颖且化学稳定性高的Ln-MOFs,即Ln-L (Ln = Sm, Eu, Gd, Tb)。晶体学数据表明,Ln-L属于四方晶系的P4212空间群。晶体结构表明,Ln-L具有2D结构互穿形成的3D结构网络,其中,相邻的Ln3+通过L4-配体连接,形成了沿b轴方向延伸的左手性和右手性的两个双螺旋链,因而整个晶体为内消旋体。此外,所得晶体呈现花瓣状形貌,为了研究其生长过程,我们探究了不同反应时间下Eu-L的结构及形貌变化。最后,我们研究了该材料对水体系中四环素的传感性能和机理。研究表明,Eu-L对四环素及其类似物不仅展现了快速(< 30 s)且灵敏(TC、OTC和CTC的检测限分别为0.43、0.92和0.81 µM)的响应,而且具有优异的选择性和重复利用性。

第五章:对本论文工作进行了总结和展望。

Other Abstract

Metal-organic frameworks (MOFs) are crystalline and porous materials formed by organic linkers and metal nodes via coordination, which have been widely applied in abundant fields, such as gas storage and separation, drug delivery, catalysis, chemical sensing and so on. MOFs possess the characteristics including controlled topological structures, morphologies, pore sizes as well as confined space can be well engineered through judiciously selecting the metal nodes and organic linkers. Lanthanide endowed with high quantum yield, long fluorescence lifetime, sharp characteristic emission peaks, high color purity, large stokes shifts and near infrared excitation or emission, which are great candidates as metal nodes to fabricate lanthanide-based metal-organic frameworks (Ln-MOFs). Recent years, Ln-MOFs with multiple fluorescent centers have been successfully fabricated, which provides an alternative strategy to fabricate the ratiometric fluorescence sensors. However, there is huge limitation to fabricate Ln-MOFs with muti-luminescent centers by just converting lanthanide ions because the limited number of lanthanide ions. Therefore, rational design and synthesis of photoresponsive organic ligands is the promising way to prepare Ln-MOFs with high fluorescent yields and multi-luminescent centers.

In this thesis, three kinds of novel luminescent Ln-MOFs were fabricated by rational design and synthesis of several organic ligands with photoresponsive properties. The structure and intermolecular energy transfer process of these materials have been systematically studied. Finally, the Ln-MOFs were applied to the construction of ratiometric sensors.

This thesis is mainly presented as the following five parts:

Chapter 1: The research background and luminescence mechanism of Ln-MOFs were firstly summarized. Then the strategies to design and synthesize Ln-MOFs were emphatically introduced. Furthermore, their state-of-the-art applications in fluorescence sensing were enumerated. Finally, the research strategies and contents of this thesis were put forward.

Chapter 2: A mixed-lanthanide MOF (Eu2.2Tb97.8-TCA) with white-light- emitting was fabricated based on triphenylamine-derived carboxylic acid ligand (H3TCA). The material could not only serve as a ratiometric luminescent sensor for trace water detecting in ethanol, but also achieve a wide-range temperature sensing. Eu2.2Tb97.8-TCA was formed by Eu3+ and Tb3+, featuring with long fluorescence lifetime and high color purity, as the lanthanide luminescent centers, and H3TCA as sensitized antenna. Two lanthanides and organic linker formed multi-luminescent centers, which exhibited different sensitivities to water and temperature. Subsequently, the ability for fluorescent detection for trace water and the detecting mechanism of Eu2.2Tb97.8-TCA were investigated. Consequently, this material showed a fast (less than 20 s) and relatively ultrasensitive (LOD = 0.016% v/v) response to trace water in ethanol, and achieved the sensitive visual determination of water in ethanol with multiple readout methods. Interestingly, according to the ratio of green (G) to red (R) values combined with a smartphone color picker application (APP), the visual and quantitative detection of water with a LOD of 0.035% v/v was achieved. We also found that the sensor could detect temperature in the range of 300-380 K with good linear relationship, high accuracy and excellent recyclability. Finally, Eu2.2Tb97.8-TCA could also be acted as white light emitting material, which was used as a single-phase UV phosphor.

Chapter 3: On the basis of work in Chapter 2, tetraphenylpyrazine-derived ligand (H4TCPP) was designed and synthesized to improve the chemical stability of Ln-MOFs. A series of novel and chemically stable anionic Ln-MOFs i.e., Ln-TCPP (Ln = Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), were constructed by solvothermal method. Firstly, the microstructure and morphology of Ln-TCPP were systematically studied. The crystallographic data revealed that Ln-TCPP belonged to the monoclinic space group I2/a, where the Ln3+ as metal node was in regular six-coordinate mode. The single crystal structure showed that the charge-balancing dimethylammonium cations ([(CH3)2NH2]+) generated from the decomposition of DMF stably existed in the channel of Ln-TCPP through hydrogen bonds with the unbonded oxygen atoms in the ligand. Secondly, we found that TCPP4- could only sensitize Eu3+, and the dual emission of ligand and Eu3+ could be achieved by introducing Tb3+ through co-doping method. By comparing the performance, Eu0.52Tb0.48-TCPP was selected for subsequent research. Then, based on the strategy of cation exchange, the phenomenon and mechanism of lanthanide-luminescence in Ln-MOFs modulated by Ag+ were investigated. Consequently, upon adding of excess Ag+ into the aqueous solution of Eu0.52Tb0.48-TCPP, the luminescent intensity of ligand decreased to 4.2 times, while that of Eu3+ increased to about 2 times, and the luminescent intensity ratio (I616/I416) of them increased from 1.44 to 12.1. The mechanism of regulating luminescence by Ag+ and the reason that the ligand in Tb-TCPP couldn’t sensitize Tb3+ under the premise of energy level matching were explained by theoretical calculation. On the other hand, the fluorescence sensing performance and mechanism of ratiometric sensor Eu0.52Tb0.48-TCPP for picric acid were also studied.

Chapter 4: Considering the results of Chapter 3, a new tetraphenylpyrazine- derived “X” type ligand (H4L) was synthesized to improve the chemical stability and pore size of Ln-MOFs. In addition, a series of novel and stable Ln-MOFs, i.e., Ln-L (Ln = Sm, Eu, Gd, Tb), were constructed by regulating the coordinated mode of ligand and Ln3+. The crystallographic data revealed that Ln-L belonged to the tetragonal space group P4212. The single crystal structure showed that Ln-L had 3D structural network formed by interpenetration of 2D structure, in which the adjacent Ln3+ were connected through L4- to form double-stranded helical chains, with the right- and left-handed structure, extending along the b-axis. Therefore, the whole crystal was mesomeric. In order to study the growth process of Eu-L, the structure and morphology changes of Eu-L under different reaction times were investigated. Finally, the sensing properties and mechanism of Eu-L toward tetracycline in aqueous solution were also investigated. As a consequence, the tetracycline and its analogues could be quantitatively detected with a fast response less than 30 s and a low detection limit of 0.43, 0.92 and 0.81 µM for tetracycline, oxytetracycline and chlortetracycline, respectively. Furthermore, the material also exhibited a good reusability and an excellent selectivity.

Chapter 5: Summaries and perspectives of this thesis.

Subject Area稀土配位化学
MOST Discipline Catalogue理学 - 化学 - 无机化学
URL查看原文
Language中文
Other Code262010_120190903761
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/538901
Collection化学化工学院
Affiliation
兰州大学化学化工学院
Recommended Citation
GB/T 7714
翟小永. 新型镧系-金属有机框架的设计构筑及其在荧光传感中的应用研究[D]. 兰州. 兰州大学,2023.
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