本文關(guān)鍵詞：功能化氧化石墨烯的制備及其與共軛聚合物的相互作用　出處：《山東大學》2017年博士論文　論文類型：學位論文

  更多相關(guān)文章： 氧化石墨烯 功能化 分散性 共軛聚合物 界面

【摘要】：石墨烯是一種單原子層厚度的二維材料,具有十分優(yōu)異的力學、電學、光學、熱學性質(zhì),正吸引著越來越多的研究力量致力于其基礎(chǔ)研究與應用開發(fā)。氧化石墨烯作為石墨烯的衍生物,具有與石墨烯相似的二維結(jié)構(gòu),性質(zhì)卻完全不同。氧化石墨烯的結(jié)構(gòu)通常由Lerf-Klinowski描述,即在石墨烯骨架的側(cè)邊修飾有羧基、羰基以及在二維平面上修飾有羥基、環(huán)氧基。含氧基團賦予了氧化石墨烯親水性和水溶液可分散性,因而單層氧化石墨烯可由氧化石墨超聲分散獲得,而后者可通過Hummers法等低成本途徑對石墨粉進行氧化得到。氧化石墨烯的親水性為氧化石墨烯的制備以及水相應用提供了便利,但也限制了氧化石墨烯在有機溶劑中的分散。因此,各種各樣的修飾方法,包括非共價鍵、共價鍵化學修飾,被采用來對氧化石墨烯進行功能化修飾,增加其在有機溶劑中的分散性,從而拓展它們在相關(guān)領(lǐng)域的應用范圍。氧化石墨烯以及功能化氧化石墨烯在納米復合材料、光催化、儲能、能量轉(zhuǎn)化等領(lǐng)域具有潛在的應用價值。作為柔性二維材料,他們具有巨大的比表面積(～2630 m2g-1),因此可以作為納米材料的載體提供非常大的界面面積,實現(xiàn)復合材料的結(jié)構(gòu)改性、光催化性能的提升、儲能密度以及能量轉(zhuǎn)換效率的提高等功能增強。氧化石墨烯中含氧官能團的碳原子以sp3雜化成鍵(σ鍵),從而引入了帶隙,并且?guī)兜拇笮∮珊趿繘Q定,因此,氧化石墨烯可被當作一種帶隙可調(diào)的二維半導體材料,從而在光電轉(zhuǎn)換領(lǐng)域獲得應用。近年來,以共軛聚合物為代表的有機半導體材料因其低成本、柔性、溶液可加工性在半導體照明、有機光伏等領(lǐng)域獲得了極大的發(fā)展。其中,以共軛聚合物復合薄膜為活性層實現(xiàn)光電轉(zhuǎn)換制備高性能的光電探測器、光伏器件等光電功能器件是目前的研究熱點。利用氧化石墨烯對共軛聚合物進行摻入,實現(xiàn)聚合物薄膜結(jié)構(gòu)及電荷傳輸特性的改變,是獲得性能增強的有機光電功能器件的有效途徑,具有非常重要的研究價值。由于大多數(shù)的共軛聚合物都只能在有機溶劑中進行加工處理,因而對氧化石墨烯進行功能化修飾以獲得非極性有機溶劑可分散性是實現(xiàn)氧化石墨烯摻入提高有機光電功能器件性能的重要前提。為獲得在非極性有機溶劑中可分散的功能化氧化石墨烯,并實現(xiàn)摻入提高基于共軛聚合物薄膜的光電功能器件性能,本論文針對功能化氧化石墨烯的制備方法及其與共軛聚合物的相互作用機制展開了系統(tǒng)研究,主要內(nèi)容包括:1.氧化石墨烯的離子鍵修飾我們改進了一種表面活性劑——雙十二烷基二甲基溴化銨(DDAB)離子鍵修飾氧化石墨烯的方法,在更為簡易的條件下實現(xiàn)功能化氧化石墨烯(DDAB-GO)從水相到有機溶劑相(鄰二氯苯,DCB)的轉(zhuǎn)移�；趯DAB-GO在相轉(zhuǎn)移前后結(jié)構(gòu)性質(zhì)改變的測量,我們提出了實驗條件下DDAB-GO的相轉(zhuǎn)移模型。組成氧化石墨烯的結(jié)構(gòu)成分——氧化碎片(OD)以及多余的DDAB分子在相轉(zhuǎn)移及凈化過程中被分離到水相中,使得DDAB-GO在非極性有機溶劑——DCB中形成潔凈、穩(wěn)定的分散液。DDAB-GO的DCB分散液與共軛聚合物——聚(3-己基噻吩-2,5-二基)(P3HT)的DCB溶液共混后可形成穩(wěn)定的分散液,一定比例的P3HT分子可附著在DDAB-GO二維片層表面,在光激發(fā)下實現(xiàn)P3HT向DDAB-GO的電荷轉(zhuǎn)移或能量傳遞,表明了 DDAB-GO在共混體系中作為電子受體的可能性。2.離子鍵功能化氧化石墨烯的可控還原基于極性有機溶劑——二甲基甲酰胺(DMF)的溶劑熱還原法被用來實現(xiàn)對分散在鄰二氯苯(DCB)中DDAB-GO的可控還原,獲得在DCB中穩(wěn)定分散的、具有不同還原程度的DDAB-rGO。我們提出了一種結(jié)合紫外-可見光吸收與電化學循環(huán)伏安法的能級結(jié)構(gòu)(LUMO/HOMO)測試方法。測試結(jié)果表明,DDAB-GO的帶隙在還原之后減小,DDAB-rGO的LUMO與HOMO能級位置隨著還原程度的增加而相互靠近,并趨向于本征石墨烯的費米能級。對DDAB-GO、DDAB-rGO與共軛聚合物——P3HT共混物薄膜的光物理特性以及基于共混薄膜的光電探測器原型器件的性能研究表明,作為受體的DDAB-rGO與給體P3HT之間的能級匹配程度是決定DDAB-rGO:P3HT共混薄膜中電荷轉(zhuǎn)移機制的重要因素,由此反映出調(diào)控DDAB-rGO的還原程度并通過測量給出DDAB-rGO能級結(jié)構(gòu)對于實現(xiàn)功能化氧化石墨烯在光電轉(zhuǎn)換領(lǐng)域高性能應用的重要價值。3.離子功能化氧化石墨烯的共價鍵修飾在離子鍵修飾的基礎(chǔ)上,分散在DCB中的DDAB-GO通過與鄰氯苯異氰酸酯(CI)進行酯化反應可得到進一步的共價鍵修飾,獲得在DCB中穩(wěn)定分散的功能化氧化石墨烯(CI-DDAB-GO)。DDAB-GO的單層分散為后續(xù)的共價鍵修飾提供了很大的反應界面,DDAB-GO剩余在二維片層表面的大量羥基則為CI基團的共價鍵修飾提供了足夠的鏈接位置。CI-DDAB-GO相比于DDAB-GO具有與共軛聚合物——P3HT更高的兼容性,對P3HT進行摻入得到的共混薄膜擁有更均勻的形貌。CI-DDAB-GO摻入可有效降低基于P3HT薄膜的光電二極管的暗電流,并提高其開關(guān)比,顯示出CI-DDAB-GO在提高共軛聚合物光電功能器件性能方面的重要價值。4.氧化石墨烯的π-π作用修飾利用共軛聚合物——P3HT輔助的GO相轉(zhuǎn)移法,我們制備了 P3HT π-π作用修飾的氧化石墨烯(P-GO)。在DCB中,P3HT分子通過與GO中sp2共軛區(qū)域的π-π作用附著在GO表面,賦予了 P-GO在DCB中的良好分散性。光物理性質(zhì)以及結(jié)構(gòu)信息的研究表明,P-GO對P3HT:PCBM共混薄膜的摻雜可促進薄膜的相分離,以獲得利于器件性能的更優(yōu)化的薄膜形態(tài)結(jié)構(gòu)。基于P-GO2.5%質(zhì)量比摻入的P3HT:PCBM共混薄膜的體異質(zhì)結(jié)有機光伏器件的性能相比于本征器件具有明顯提升,其中光電轉(zhuǎn)化效率(PCE)提高接近18%。
[Abstract]:Graphene is a two-dimensional material with a single atomic layer thickness. It has excellent mechanical, electrical, optical and thermal properties. It is attracting more and more research efforts for its basic research and application development. As a derivative of graphene, graphene oxide has a two dimensional structure similar to graphene, and its properties are completely different. The structure of graphene oxide is usually described by Lerf-Klinowski, that is, there are carboxyl and carbonyl groups on the side of graphene skeleton, and hydroxyl and epoxy groups are modified on 2-D plane. The oxygenated group gives the graphene hydrophilicity and dispersibility of aqueous solution. Therefore, monolayer graphene oxide can be obtained by ultrasonic dispersion of graphite oxide, while the latter can be oxidized by graphite powder through low cost way such as Hummers method. The hydrophilicity of graphene oxide provides convenience for the preparation of graphene oxide and the application of water phase, but it also restricts the dispersion of graphene oxide in organic solvents. Therefore, a variety of modification methods, including non covalent and covalent chemical modifications, are used to functionalized graphene oxide and increase their dispersion in organic solvents, thereby expanding their application in related fields. Graphene oxide and functionalized graphene oxide have potential applications in the fields of nanocomposites, photocatalysis, energy storage and energy conversion. As a flexible two-dimensional material, they have a huge specific surface area (~ 2630 m2g-1), so it can be used as a carrier of nano materials provide a very large interfacial area, the structure of the composite modification and photocatalytic performance improvement, energy storage density function and improve the energy conversion efficiency enhancement. The oxygen-containing functional groups of graphene oxide in carbon atoms in SP3 hybrid orbitals (sigma bond), which introduced the band gap, and the gap is adjusted by the oxygen content decided, therefore, graphene oxide can be regarded as a kind of two-dimensional semiconductor materials with tunable band gap, which was applied in the field of photoelectric conversion. In recent years, organic semiconductor materials represented by conjugated polymers have made great progress in semiconductor lighting, organic photovoltaic and other fields because of their low cost, flexibility and solution processability. Among them, conjugated polymer thin film as active layer to achieve photoelectric conversion to prepare high-performance photoelectric detectors, photovoltaic devices and other photoelectric functional devices is the current research hotspot. Using graphene oxide to conjugate polymers, the structure and charge transfer properties of polymer films are changed. It is an effective way to obtain enhanced organic photoelectric functional devices, and has very important research value. Because most of the conjugated polymers can only be processed in organic solvents, so the functionalization of graphene oxide to obtain non-polar organic solvent dispersion of the graphene oxide incorporation is important premise to improve the performance of organic optoelectronic devices. In order to obtain non functionalized graphene oxide can be dispersed in polar organic solvents, and improve the incorporation of photoelectric devices based on the properties of conjugated polymer film and preparation method for the functionalization of graphene oxide and its interaction mechanism with conjugated polymers developed system were studied, the main contents include: ion key 1. graphene oxide modified we improved a surfactant - alkyl two methyl bromide (DDAB) method of modified graphene oxide ionic bond, the more function of the oxidation of graphene simple conditions (DDAB-GO) from the aqueous phase to the organic phase (o two chlorobenzene, DCB transfer). Based on the measurement of the structural properties of DDAB-GO before and after phase transfer, we propose a phase transfer model of DDAB-GO under experimental conditions. The structural components of graphene oxide -- oxidized debris (OD) and redundant DDAB molecules are separated into water phase during phase transfer and purification process, making DDAB-GO form a clean and stable dispersion in non-polar organic solvents DCB. DDAB-GO DCB dispersions and conjugated polymer poly (hexylthiophene: 3- -2,5- two) (P3HT) DCB solution can be formed after the dispersion stability of P3HT molecules, a certain proportion can be attached to the DDAB-GO two-dimensional sheet surface, the realization of P3HT to DDAB-GO charge transfer and energy transfer in the light show the possibility of DDAB-GO in the blends as electron acceptor. Controllable 2. ionic bond functionalized graphene oxide reduction of polar organic solvent - two methyl formamide (DMF) method was used based on the realization of the dispersion in the adjacent two chlorobenzene solvent thermal reduction (DCB) controlled the reduction of DDAB-GO, obtain stable dispersion in DCB, with different degree of reduction of DDAB-rGO. An energy level structure (LUMO/HOMO) method combining ultraviolet visible light absorption and electrochemical cyclic voltammetry is proposed. The test results show that the band gap of DDAB-GO decreases after reduction. The location of LUMO and HOMO level of DDAB-rGO is close to each other with the increase of reduction degree, and tends to the Fermi level of intrinsic graphene. The photophysical properties of DDAB-GO, DDAB-rGO and P3HT blends of conjugated polymer films and shows that the performance of the photoelectric detector prototype device based on the blend film, as the receptor DDAB-rGO and P3HT to the level between the degree of matching is an important factor in determining the charge transfer mechanism of DDAB-rGO:P3HT blend thin films, thus reflecting the reduction degree of regulation of DDAB-rGO and by measuring the energy level structure of DDAB-rGO is given for the functionalization of graphene oxide to achieve an important value in high performance applications in the field of photoelectric conversion. 3., the covalent bond modification of ion functionalized graphene oxide is based on ionic bond modification. The DDAB-GO dispersed in DCB can be further covalent modified by esterification with CI, and stable dispersion of DCB is achieved.
【學位授予單位】：山東大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：O613.71;O631
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本文編號：1344955