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抽象的

高級色譜 2019：基於表面支撐金屬有機薄膜材料的異質結用於三重態三重態湮滅上轉換 - Shargeel Ahmad - 大連理工大學。

沙吉爾·艾哈邁德

抽象的：

利用高度結晶和精密設計的MOF微膜異質接面開發出表面保持金屬自然結構的薄膜混雜材料。以金屬卟啉光敏劑（四苯基卟啉鋅（II））和光發射體（3,9-苝二甲酸腐蝕劑）形成異質結，進行三重態湮滅上轉換，以提升活力。透過克服Shockley-Queisser極限，可以使用一半和一半的MOF薄膜材料將低能量綠光轉變為高能量藍光。所獲得的資訊表明，該雜交材料可以作為基於TTA UC的升級活力轉化材料的動力來源之一。

介紹：

尋找用於太陽能轉換技術的新材料非常重要，這將有助於我們為下一代節省能源。利用三重態三重態湮滅上轉換 (TTA UC) 的概念需要一種智慧混合材料來克服所需的距離，以實現平穩、高效的三重態能量轉移 (TEnT)。然而，TTA UC過程是最好的波長移動方法之一，其中兩個高波長的低能量光子（hu1）被吸收並透過Dexter型能量轉移機制轉化為一個低波長的高能量光子（hu2）。在我們先前的討論中，我們透過固液界面和表面修飾，報告了乙腈溶液中作為敏化劑的PtOEP（PtOEP = Pt(II) 八乙基卟啉）和作為受體的Zn-苝SURMOF 之間的三重態能量轉移[5]。在這裡我們可以透過製作SURMOF-SURMOF異質接面來研究固-固界面來研究TTA UC。

TTA UC 使用各種材料進行了研究，以提高當代對太陽能的需求。此外，由於其可控的生長方向，現代表面錨定金屬有機框架（SURMOF）材料在氣體分離、電子、二氧化碳減排、水分解、光伏以及最近的TTA-UC系統中的應用做出了顯著的努力、可調的孔徑和最高的結晶度。

It has been reported that the Zn (II) tetraphenylpophyrin molecules have s and p bond between N atom and Zn+2 transition metal. The Zn+2 and N atom have p coordination due to d electrons which strengthens the (T1 ← S1) transition.As a matter of fact the Zn (II) tetraphenylpophyrin photosensitizer can also effectively utilize the long-lived S2 state (1.5 and 2.4 ps) with strong transition ( S2 ← S0 ) followed by hopping process with S2 excitation energy which needs the emitter of higher energy level.

Moreover, the blue emitter-perylene molecule has lower energy level which favors the triplet energy transfer (TEnT) followed by triplet triplet annihilation mechanism from sensitizer and the exchange of triplet energy with acceptor annihilating the triplets for the formation of singlets to generating the blue light with high energy. In this work we will introduce the formation of heterojunction with Zn (II) tetraphenylpophyrin molecules as sensitizer and 3,9-perpylenedicarboxylic acids as acceptor which will be used for triplet triplet annihilation upconversion (TTA UC)

Preparation of substrates

The quartz glass / FTO glass (SOLARONIX, Switzerland) substrates were cleaned in acetone for approximately ten minutes in an ultrasonic bath then these are treated with plasma under O2 for nearly thirty minutes to generate a surface with -OH (hydroxyl groups).These cleaned substrates were used instantaneously to grow SURMOF.

Preparation of Zn-perylene SURMOF

Liquid phase epitaxy technique is used for the preparation of the Zn-Perylene SURMOFs on top of FTO /Quartz Glass substrates. We prepared a concentration zinc acetate ethanolic solution (1 mM). On top of cleaned FTO we sprayed it for 5s. After 30s wait, 3,9 perylene dicarboxylic acid ethanolic solution was sprayed ( concentration:20-40M; spray time: 20 s, waiting time: 30 s). This alternate spray process of Zn-acetate as metal linker and 3,9 perylene dicarboxylic acid as organic linker supported the formation of highly crystalline metal organic framework thin film and more detail can be found somewhere in the literature.

Preparation of Zn-porphyrin SURMOF and Its Heterojunction

SURMOF of Zn (II) metalloporphyrin were fabricated using well established highly throughput automated spray system Briefly, a concentration of 20 mM Zn(II)metalloporphyrins in ethanol (spray time: 25 s, waiting time: 35 s) and a concentration of 1 mM zinc acetate in ethanol (spray time: 15 s, waiting time: 35 s) were one by one sprayed onto the FTO / Quartz Glass substrates in a layer-by-layer fashion using N2 as a carrier gas (0.2 mbar). In between, pure ethanol was used for rinsing to get rid of the unreacted species from the surface (rinsing time: 5 s). The thickness of the sample was controlled by the number of deposition cycles. Moreover, the SURMOF-SURMOF heterojunction was formed by firstly growing the 20 cycles of Zn-perylene SURMOF and on top of it 20 more cycles of Zn (II) metalloporphyrin SURMOF was added to make heterojunctions. Moreover, the formation of heterojunction which is described in the literature.

Triplet-triplet annihilation upconversion (TTA UC) setup

First of all, 40 mg/ml PMMA (poly methyl (methacrylate) was prepared in the acetonitrile solution. Then as prepared MOF thin film material consisting of  FTO/Quartz Glass-Zn-perylene SURMOF+Zn-porphyrin SURMOF were immersed into the well mixed acetonitrile solution of PMMA which was degassed with N2 for half an hour. The heterostructure was characterized for triplet triplet annihilation upconversion using laser light source.

XRD Characterizations

Results and Discussions

Comparative analysis of the ultraviolet-visible (UV-vis) spectrum of Zn-perylene SURMOF, Zn-porphysin SURMOF and Zn-perylene-Zn-porphyrin heterojunction is being shown in Figure 3. The UV¬-vis spectrum of Zn-perylene alone SURMOF range from 358 nm to 470nm (in brown) which is also compared with the solution of free perylene dicarboxylic[11] acids indicating a blue shift in MOF thin film sample. The UV-vis of Zn-porphyrin shows a Sorret Band at ~ 440nm and two Q bands between 530 nm to 614 nm. The Zn (II) tetraphenylpophyrin molecule shows two Q bands which are different from free base porphyrin generating four Q bands because Zinc+2 ion coordination with porphyrin  molecule changes the symmetry of the former molecule The combined UV vis of Zn-perylene SURMOF and Zn-porphyrin SURMOF heterostructure overlaps with all the bands of both MOF thin films shown in figure 3(red).The merging of all the bands in SURMOF heterostructure is very important for efficient absorption of green light and its conversion into blue light

The obtained quantum yield efficiency of Zn-perylene SURMOF+Zn-porphyrin SURMOF heterostructure is 0.182%. Following the same method of calculation mention in the reported literature, we found that the calculated value is consistent with the literature values. However, it is highly recommended to use the heterojunction for future dye sensitized solar cell devices.

結論與意義：基於MOF薄膜的智慧雜化材料可用來增強能量轉換三重態三重態湮沒上轉換。研究的混合材料可用於未來的能量轉換裝置。觀點是可以用高度結晶的 MOF 薄膜製造原型染料敏化太陽能電池裝置。此外，已經證明，透過克服更長的距離可以顯著增強光電流，最終可能克服Shockley-Queisser極限。在這個方向上的進一步努力可能會為探索更多用於太陽能轉換器件的 MOF 薄膜材料開闢新途徑。