鈥/銪摻雜二氧化鈰奈米粒子之螢光研究

Studies of photoluminescence properties in Ho/Eu-doped Cerium oxide nanoparticles.

陳裕文(Yu-Wen Chen)

指導教授 ： 蘇雲良

國立清華大學/原子科學院/先進光源科技學位學程/碩士(2013年)

https://doi.org/10.6843/NTHU.2013.00163

摘要

本實驗由化學沉澱法做出二氧化鈰(CeO2)分別摻雜銪與鈥的奈米粒子，本實驗藉由控制鍛燒溫度與氣體來改變奈米粒子中Ce三價的數量以及空間上的分布，並探討Ce三價在空間上的分布對奈米粒子螢光強度的影響。
我們控制溫度於500oC、700oC、900oC做鍛燒，由X光繞射數據中得知在不同溫度下分別得到粒徑大小約15nm、30nm、70nm的奈米粒子。由延伸X光吸收精密結構實驗中確定摻雜原子取代晶格中鈰的位置。在螢光光譜實驗中發現，摻雜鈥的樣品以氧氣鍛燒後可觀察到較強的螢光訊號，然而在摻雜銪的樣品中則是以還原氣鍛燒擁有較強的螢光訊號。而紫外光至可見光光譜實驗告訴我們螢光訊號主要來自樣品表面。
在摻雜鈥的樣品中，經由紫外光至可見光光譜與紅外線光譜實驗中確定，以還原氣鍛燒的樣品表面含有較多的有機物與OH-導致在可見光波段的吸收率增加降低螢光強度。
在摻雜銪的樣品中，於近邊X光吸收精密結構實驗數據確定Ce三價的濃度在不同氣體、相同溫度的鍛燒條件下並無明顯差別，然而在X光電子能譜測量表面物性的實驗中卻發現以氧氣鍛燒的樣品表面擁有較高的Ce三價濃度。藉由以上的實驗，我們提出一個模型解釋不同氣體鍛燒對Ce三價於奈米粒子內空間分布情形的影響，此模型成功解釋了近邊X光吸收精密結構與X光電子能譜的實驗結果，也解釋了螢光光譜量測中以還原氣鍛燒摻雜銪的樣品為何擁有較強的螢光訊號。

關鍵字

螢光 ； 二氧化鈰 ； 奈米粒子 ； 鈥 ； 銪

並列摘要

Europium/Holmium doped Cerium dioxide were synthesized by chemical precipitation technique and annealed at 500、700 and 900 °C under different gas to study its effect on the 〖Ce〗^(3+) concentration and the 〖Ce〗^(3+) spatial distribution inside nanoparticle. This research investigates the correlation between the 〖Ce〗^(3+) distributed inside nanoparticle and the intensity of luminescence.
X-ray diffraction result shows the particle size increases from 5nm to 15nm, 30nm and 70nm respectively under different annealed temperature. The extended X-ray absorption fine structure result shows the doped atom substitute the Cerium atom. Photoluminescence studies show samples of Holmium doped Cerium dioxide have higher luminescence intensity after being annealed under oxygen and samples of Europium doped Cerium dioxide have higher luminescence intensity after being annealed under forming gas. Ultraviolet–visible spectroscopy result shows the luminescence signals were mainly from the surface of nanoparticle.
Ultraviolet–visible spectroscopy and Infrared spectroscopy explain why samples of Holmium doped Cerium dioxide have higher luminescence intensity after being annealed under oxygen. Ultraviolet–visible spectroscopy results show samples of Holmium doped Cerium dioxide after being annealed under forming gas have high absorption in visible light. Infrared spectroscopy studies show those samples have more organics and OH groups on the surface.
In Europium doped Cerium dioxide, X-ray absorption near edge structure results show not much difference on 〖Ce〗^(3+) concentration between the samples annealed under oxygen and forming gas. However, X-ray photoelectron spectroscopy studies show samples have more 〖Ce〗^(3+) concentration on the surface after being annealed under oxygen. From the above two experiment result, I propose a model to explain the effect on the 〖Ce〗^(3+) spatial distribution inside nanoparticle from different gas annealed. This model successfully explains the experiment results of X-ray absorption near edge structure and X-ray photoelectron spectroscopy. It also explains Europium doped Cerium dioxide has higher luminescence intensity after being annealed under forming gas in the Photoluminescence result.

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