微波法製備高量子產率螢光分子與碳奈米點之應用

本研究使用含有羧酸基以及胺基基團的有機化合物做為起始物，利用微波合成法，在短時間內製備出高螢光量子產率之螢光寡聚物(Fluorescent oligomer，FO)與奈米碳點(Carbon Nanodots，CNDs)。反應過程所使用的溶劑為超純水，使製程更為環保。在相同的微波功率下(1000W)，透過改變微波時間的長短可以得到不同類型與光學性質的產物，起始物經過120秒與180秒的微波反應並經透析純化後，能分別得到透明無色的膠狀產物與黃褐色的固體產物，兩者皆能溶於水，且在紫外光的照射下能發出藍色螢光，其量子產率分別為74.86%與17.16%。此外，透過雷射粒徑、質譜儀、拉曼光譜儀與X光繞射儀的鑑定得知經120秒微波反應得到的產物為寡聚物(FO)，其分子量約為1296 Da；經180秒微波反應得到的產物為奈米碳點(CNDs)，其平均粒徑約為4.3 nm。兩種產物皆利用螢光光譜儀測量其光激發光的性質、紫外線-可見光光譜儀測量其最大吸收波長、拉曼光譜儀鑑定是否存在石墨與無序碳的結構、X光繞射儀分析其晶相，以及傅立葉紅外線光譜儀鑑定其化學官能基。最後，將具有高量子產率的產物FO應用於白光發光二極體（WLED）製作，透過旋轉塗佈的方式，將產物FO作為發光層的材料，以此研究其電激發光的特性。實驗結果表明，當施予元件8V的驅動電壓時，其色度座標為(0.3457, 0.3496)，與純白光的位置(0.33, 0.33)相近，顯示其潛在的應用性。

In this study, high quantum yield oligomer and carbon nanodots are synthesized in a short time period by one-step procedure based on microwave heating method, using organic compounds incorporating carboxylic acid (citric acid) and amino groups (tris (hydroxymethyl)-aminomethane hydrochloride) as precursors. The solvent used in reactions is ultrapure water which makes the process more environmentally friendly. Under the same microwave power radiation (1000 W), two types of products can be obtained by changing the reaction time. For 120 or 180 secs irradiation, the reaction system change from solution to colorless colloid (FO) or orange solid (CNDS) Both products are water-soluble and display blue fluorescence under the UV light. After dialysis, the quantum yield of FO and CNDS are 74.86% and 17.16%, respectively. In addition, through a series of characterization, the FO is regarded as oligomer and the CNDS is taken as carbon nanodots. According to dynamic light scattering analysis, the average size of CNDS in solution is 4.3 nm and based on the mass spectrum, the molecular weight of FO is about 1296 Da. Besides, both are characterized by photoluminescence spectrometer for PL properties, X-ray diffraction analyzer for crystallinity, UV-visible spectrometer for absorbance, fourier-transform infrared spectrometer for chemical functional groups, and Raman for graphitization. Finally, in order to study the electroluminescence properties of FO, it is taken as emissive material in an emitting layer to fabricate white light-emitting diode (WLED) by using the spin-coating technique and it turns out that when the WLED device operated at voltages of 8, it result in bluish white-light emission with the CIE coordinate (0.3457, 0.3496) , which is close to the CIE coordinates for pure white light, (0.33, 0.33), suggesting the FO might be useful in WLED in the future.