本文選題：相互作用 + 聚合物發(fā)光�。� 參考：《中國科學技術(shù)大學》2017年博士論文

【摘要】：材料是支撐人類文明發(fā)展的物質(zhì)基礎。高效、經(jīng)濟和實用的新型材料的持續(xù)涌現(xiàn)為社會進步提供了不竭助力。因此,新材料的研發(fā)成為了當前一項長久的目標。然而,材料結(jié)構(gòu)的復雜性為實驗的合成和表征帶來了困難。幸運的是,理論計算和模擬從內(nèi)部機制和電子結(jié)構(gòu)層次為材料的解析提供了有力的工具。特別是近年來高性能計算和復雜電子結(jié)構(gòu)理論和模型的快速發(fā)展,使得第一性原理電子結(jié)構(gòu)計算和分子動力學模擬能力進一步提升。從原子和分子尺度上對材料性能進行預測和解釋,抓住體系的關鍵要素,進行合理的構(gòu)效和設計,與實驗相輔相成,成為了新型材料研發(fā)的有力手段。不同體系如分子或材料之間的相互作用是連接物質(zhì)結(jié)構(gòu)和性質(zhì)的關鍵橋梁。通過解析體系中分子或材料本身的結(jié)構(gòu)和性能,利用分子間和材料間的相互作用進行理性的構(gòu)效和復合,為提高材料本身固有性能,彌補缺陷,協(xié)同增效,設計并獲得新型性能的功能化材料研發(fā)提供了新的思路和途徑。本論文從不同體系間(分子和材料)的相互作用出發(fā),采用第一性原理的密度泛函理論(DFT)進行模擬計算,研究分子間的相互作用(π-π耦合)對分子發(fā)光的影響(第三章)和功函數(shù)、電負性等不同的材料間相互作用引起的電荷極化對催化機理的影響(第四章)。主要包括四個部分:第一部分即第一章,主要基于后面的工作介紹了兩個內(nèi)容,第一個是聚合物發(fā)光材料研究進展。與改變發(fā)光材料本身的內(nèi)部結(jié)構(gòu)(如官能團修飾,增加共軛長度)調(diào)控發(fā)光過程相比,通過分子間π-π耦合相互作用形成的聚合物發(fā)光材料操作性更大,應用范圍更廣,因而,引起了人們的關注和研究。雖然最基本的發(fā)光原理與其他發(fā)光分子相同,但由于分子間的相互作用,聚合物發(fā)光又有其獨特的內(nèi)部機制,這種獨特的機制為聚合物的發(fā)光帶來了特定的性能,也為調(diào)控分子發(fā)光過程提供了可能性。第二個是金屬半導體及二維材料催化反應的研究進展。催化反應的核心內(nèi)容是催化劑的設計和研究。金屬催化劑反應性能優(yōu)越,但缺點是穩(wěn)定性較差,價格昂貴,而相對而言,半導體催化劑穩(wěn)定性較好,但催化活性又相對較低。因此,催化劑構(gòu)效時,可以利用不同材料間的相互作用進行復合,在性能互補的前提下,產(chǎn)生協(xié)同效應,提高材料的催化反應效率和穩(wěn)定性,降低成本。另一方面,作為一類無金屬的材料,以石墨烯為代表的二維材料催化劑因其優(yōu)良的化學穩(wěn)定性、半導體性、易調(diào)控性和優(yōu)異的光學性質(zhì)也在化學反應中展現(xiàn)出優(yōu)越的性能,成為了當前催化研究的一個重要的焦點。第二章主要介紹了以第一性原理為基礎的密度泛函理論,包括它的理論框架,發(fā)展流程,含時密度泛函理論以及量化應用軟件包。密度泛函(DFT)的理論基礎是量子力學,其基本研究量是體系的電子密度。通過對Kohn-Sham方程的求解,把相互作用的多粒子體系轉(zhuǎn)換成無相互作用的單粒子體系,并通過合適的交換關聯(lián)泛函進行近似,經(jīng)過一系列的循環(huán)迭代直到收斂,計算出體系基態(tài)時的能量和密度。而在密度泛函中引入含時微擾的含時密度泛函理論,則可更為精確的模擬激發(fā)態(tài)的電子結(jié)構(gòu)。密度泛函理論在應用上的最終實現(xiàn)依賴量化軟件包的計算模擬。第三章介紹了分子間相互作用與分子發(fā)光的研究,主要包括兩個工作:第一工作是分子聚集誘導系間竄越增強磷光。分子內(nèi)的系間竄越(ISC)在各種光電應用中起著重要的作用。然而,利用傳統(tǒng)的化學修飾和重金屬摻雜等方法提高系間竄越幾率十分不便,限制了其應用范圍。在我們的工作中,我們提出了一種新型的"聚集誘導系間竄越"(AI-ISC)機制。在聚合物分子中,利用分子間相互作用引起的激發(fā)態(tài)能級分裂,可以改善單重和三重激發(fā)態(tài)的能級匹配,進而提高系間竄越的幾率。通過第一性原理的模擬計算和實驗光譜檢測,分子聚集體中這種增強的系間竄越幾率大大促進了分子的磷光發(fā)射。同時,磷光發(fā)射也隨著聚集程度的增強而發(fā)生紅移,為磷光波長的調(diào)節(jié)提供了一個便捷的渠道。第二個工作是自組裝有機量子點的發(fā)光機制。在這個工作中,我們模擬設計并合成了一種新型的有機染料量子點,該量子點體系在溶液中展現(xiàn)出了超高的熒光量子產(chǎn)率,而其通過疏水相互作用和π-π堆積形成固態(tài)時,熒光產(chǎn)率較低,且發(fā)光波長對激發(fā)波長具有很強的依賴。理論計算發(fā)現(xiàn)這種量子點的發(fā)光原理為在在溶液中分子聚合被破壞,主要以單分子形式存在,通過與溶劑發(fā)生作用,形成了 push-pull電荷轉(zhuǎn)移機制,進而影響了發(fā)光效率。而在固態(tài)時,分子發(fā)生π-π堆積和H-聚集,能級產(chǎn)生分裂,分子振動受到抑制,弛豫變慢,違反了 Kasha's規(guī)則,發(fā)光波長對激發(fā)波長具有很強的依賴性,同時激發(fā)態(tài)的輻射躍遷幾率下降,熒光量子產(chǎn)率降低。第四章介紹了材料間相互作用引起的電荷極化與催化機理的研究,主要包括三個工作:第一個工作是石墨烯基復合材光催化制氫與安全儲氫。在這個工作中,我們設計了一種C_xN_y和石墨烯基材料復合的三明治結(jié)構(gòu),其中,碳氮材料(g-C_xN_y)夾在兩層官能團修飾的石墨烯中(GR_F)。第一性原理計算發(fā)現(xiàn),由于g-C_xN_y和GR_F之間相互作用引起的電荷極化,使得這種三明治體系可以同時捕獲紫外光和可見光,進而激發(fā)產(chǎn)生空穴遷移到外層的GR_F上。在光生空穴的幫助下,吸附在GR_F上的水發(fā)生裂解,產(chǎn)生質(zhì)子,受聚集負電荷的C_xN_y靜電吸引,質(zhì)子穿透石墨烯遷移到C_xN_y上,并在光生電子的作用下,產(chǎn)生氫氣。由于外層的石墨烯結(jié)構(gòu)不允許氫氣的穿透,使得氫氣與外界分離,儲存在體系中。綜合可知,我們設計的這種三明治復合體系實現(xiàn)了光催化制氫和安全儲氫一體化。第二個工作是氮摻雜石墨烯催化還原對羥基苯酚。實驗中,通過多種MOF材料為前驅(qū)模板在高溫下燒結(jié)得到了氮摻雜石墨烯的多層碳材料并催化還原對硝基苯酚。含有吡咯N摻雜石墨烯最多的材料催化活性最佳。理論計算通過對三種N摻雜石墨烯的構(gòu)型,電子結(jié)構(gòu),吸附性能,導電性的研究,發(fā)現(xiàn):摻雜的N原子和石墨烯由于電負性的差異,相互作用后發(fā)生電荷極化,電荷發(fā)生聚集,提供活性位點;吡咯N摻雜石墨烯中活性位點附近正電荷聚集最多,對4-NP-的吸附能最強,耦合活化程度較高;吡咯N摻雜石墨烯體系延續(xù)了石墨烯材料優(yōu)良的導電性能,為還原反應的發(fā)生提供源源不斷的驅(qū)動力。因此,吡咯N摻雜石墨烯對催化還原對硝基苯酚具有較高的反應活性,與實驗結(jié)果吻合。第三個工作是TiO_2-Pd@Pt光催化裂解水。理論和實驗合作設計并合成了原子厚度可調(diào)節(jié)的Pd@Pt殼層結(jié)構(gòu),并將這種殼層結(jié)構(gòu)與n型半導體,銳鈦礦TiO_2結(jié)合。在這一體系中,Pd@Pt殼層結(jié)構(gòu)在光催化水裂解反應中,起到了雙重功效,這雙重功效均取決于復合材料中金屬Pt的原子厚度。這雙重功效分別是:利用Pd,Pt間相互作用引起的界面電荷極化提高金屬上的電子捕獲能力,進而促進電荷分離;通過Pt表面電荷密度的增加和晶格應力提高對于水的吸附能力。這些性能的提高顯著的增強了光催化裂解水的催化活性。
[Abstract]:Material is the material foundation to support the development of human civilization. The continuous emergence of new materials with high efficiency, economy and practicality has provided an inexhaustible contribution to social progress. Therefore, the development of new materials has become a permanent goal. However, the complexity of the material structure has brought difficulties to the synthesis and characterization of the experiment. Fortunately, theoretical calculation. And simulation provides a powerful tool for the analysis of materials from the internal mechanism and the electronic structure level. Especially in recent years, the high performance calculation and the rapid development of complex electronic structure theory and model make the ability of the electronic structure calculation and molecular dynamics simulation of the first principle to be further improved. From the atomic and molecular scales to material properties The key elements of the system can be predicted and explained, and the key elements of the system are seized and the structure efficiency and design are reasonable. It is complementary to the experiment. It has become a powerful tool for the research and development of new materials. The interaction between different systems, such as molecules or materials, is a key bridge to connect the structure and nature of material. And properties, using the interaction of intermolecular and material to make rational structure effect and compound, and provide new ideas and ways to improve the intrinsic properties of the material, make up the defects, synergy the efficiency, design and obtain the new functional functional materials. This paper is based on the interaction of different systems (molecules and materials). The density functional theory (DFT) of the first principle is used to simulate the effects of intermolecular interaction (PI - pi coupling) on molecular luminescence (third chapter) and the effect of charge polarization on the catalytic mechanism caused by the interaction of power functions, electronegativity and other intermaterial interactions (fourth chapter). The first part is the first chapter, the first chapter Two contents are introduced mainly based on the later work. The first is the progress in the research of polymer luminescent materials. Compared with the changes in the internal structure of the luminescent materials, such as the functional group modification and the increase of the conjugate length, the polymer luminescent materials formed by the interaction of the intermolecular pion coupling interaction are more operable and applied. More widely, it has attracted people's attention and research. Although the most basic principle of luminescence is the same as other luminescent molecules, because of the interaction between molecules, the luminescence of polymer has its unique internal mechanism. This unique mechanism provides specific properties for the luminescence of polymers and provides the possibility for the regulation of molecular luminescence. The second is the progress in the catalytic reaction of metal semiconductors and two-dimensional materials. The core content of the catalytic reaction is the design and research of the catalyst. The catalytic performance of the metal catalyst is superior, but the disadvantage is that the stability is poor and the price is expensive, and the stability of the catalyst is better, but the catalytic activity is relatively low. Therefore, the catalytic activity is relatively low. When the agent is constructed, it can be combined with the interaction of different materials to produce synergistic effects on the premise of complementing performance, to improve the efficiency and stability of the catalytic reaction and to reduce the cost. On the other hand, as a kind of non metal material, the two-dimensional material catalyst with graphene as the substitute for its excellent chemical stability. Semiconductors, easy regulation and excellent optical properties also exhibit superior properties in chemical reactions. The second chapter mainly introduces the density functional theory based on the first principle, including its theoretical framework, development process, time-dependent density functional theory and quantitative response. The theoretical basis of the density functional (DFT) is the quantum mechanics, which is based on the quantum mechanics. Its basic research amount is the electronic density of the system. By solving the Kohn-Sham equation, the interacting multiple particle system is converted into a single particle system without interaction. The energy and density of the system ground state are calculated, and the time-dependent density functional theory with time-dependent perturbation is introduced in the density functional. The electronic structure of the excited state can be more accurately simulated. The final realization of the density functional theory in the application depends on the calculation simulation of the quantitative software package. The third chapter introduces the intermolecular interaction and the molecules. The research of luminescence mainly consists of two tasks: the first work is the enhancement of phosphorescence between the molecular aggregation induced lines. The intermolecular channeling and crossing (ISC) plays an important role in various optoelectronic applications. However, it is very inconvenient to use traditional chemical modification and heavy metal doping to increase the probability of intersystem channeling, which limits its application. In our work, we propose a new type of "AI-ISC" mechanism. In polymer molecules, the energy level division caused by intermolecular interaction can be used to improve the energy level matching between the single and three excited states, and then the probability of the intersystem crossing is improved. In the experimental spectrum, the increasing probability of this enhancement in the molecular aggregates greatly promotes the molecular phosphor emission. At the same time, the phosphor emission also redshifts with the enhancement of the aggregation degree, providing a convenient channel for the adjustment of the phosphorescence wavelength. The second work is the luminescence mechanism of the self assembled organic quantum dots. In this study, a novel quantum dot of organic dye was designed and synthesized. The quantum dot system showed a high fluorescence quantum yield in the solution. The fluorescence yield was lower when the hydrophobic interaction and pion pion accumulated to form solid state, and the luminescence wavelength had a strong dependence on the excitation wavelength. Theoretical calculations found that the quantum dots have a strong dependence on the excitation wavelength. The principle of quantum dots luminescence is that the molecular polymerization in the solution is destroyed, mainly in the form of single molecule. By the action of the solvent, the push-pull charge transfer mechanism is formed, and the luminescence efficiency is influenced. In the solid state, the molecules have pion pion accumulation and H- aggregation, the energy level is split, the molecular vibration is suppressed and the relaxation slows down. In violation of the Kasha's rule, the luminescence wavelength has a strong dependence on the excitation wavelength, while the radiation transition probability of the excited state decreases and the fluorescence quantum yield is reduced. The fourth chapter introduces the study of the charge polarization and the catalytic mechanism caused by the intermaterial interaction, including three work: the first work is the photoluminescence of graphene based composites In this work, we have designed a sandwich structure of C_xN_y and graphene based materials, in which carbon and nitrogen (g-C_xN_y) is sandwiched between two layers of functionalgraphene modified graphene (GR_F). First principle calculation shows that the charge polarization caused by the interaction between g-C_xN_y and GR_F makes this three The Meiji system can capture both ultraviolet and visible light at the same time, and then stimulate the GR_F of the hole moving to the outer layer. Under the help of the photogenerated hole, the water adsorbed on the GR_F occurs cracking, produces protons, is attracted by the C_xN_y electrostatic charge of the aggregated negative charge, the proton transmigrates to the C_xN_y through the graphene, and produces hydrogen under the action of photogenerated electrons. Gas. As the structure of the outer layer of graphene does not allow hydrogen penetration, the hydrogen is separated from the outside and stored in the system. It is known that the sandwich composite system designed by us has realized the integration of photocatalytic hydrogen production and safe hydrogen storage. The second work is the nitrogen doped graphene catalyzed reduction of hydroxyl phenol. In the experiment, through a variety of MOF The material was sintered at high temperature to obtain the multilayer carbon material of nitrogen doped graphene at high temperature and catalyze the reduction of p-nitrophenol. The best catalytic activity of the material containing pyrrole N doped graphene was the best. The theoretical calculation was carried out through the study of the configuration, electronic structure, adsorption and conductivity of three kinds of N doped graphene, and found that doped N atoms Due to the electronegativity difference between graphene and graphene, the charge polarization, charge accumulation and active site are provided after interaction. The active site of positive charge near the active site in pyrrole N doped graphene is the most, the adsorption energy of 4-NP- is the strongest, and the coupling activation degree is higher. The pyrrole N doped graphene system continues the excellent conductivity of graphene materials. It provides a constant source of driving force for the reduction of the reaction. Therefore, pyrrole N doped graphene has a high reaction activity to the catalytic reduction of p-nitrophenol, which is in agreement with the experimental results. The third work is TiO_2-Pd@Pt photocatalytic cracking water. The theoretical and experimental cooperating design and synthesis of the atomic thickness adjustable Pd@Pt shell structure, The shell structure is combined with the N type semiconductor, anatase TiO_2. In this system, the Pd@Pt shell structure has dual functions in the photocatalytic water cracking reaction, which all depend on the atomic thickness of the metal Pt in the composite. The double effects are the increase of the interface charge polarization caused by the interaction of Pd and Pt, respectively. The electron capture on the metal promotes charge separation and increases the adsorption capacity of water by increasing the surface charge density of the Pt and the stress of the lattice. These properties increase the catalytic activity of the photocatalytic cracking water.
【學位授予單位】：中國科學技術(shù)大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O643.3;O644.1

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