CdSeZnS半導體奈米粒子合成、檢測及應用

Abstract

近年來，奈米技術蓬勃發展，當材料任一維度尺寸小於100奈米(nm)時，會具有量子侷限(quantum-confinement effect)現象，使之展現獨特的量子化效應。 其中，零維度之半導體奈米材料—量子點(quantum dot, QDs)，具有獨特的光電特性，量子產率(quantum yield, QY)高且半高寬(full-width at half-maximum, FWHM)窄，依據其組成和尺寸大小不同，在紫外光激發下會發出不同顏色的螢光(Fluorescence)，與一般染料相比，可以增加光穩定性，提高色飽和度以及螢幕解析度。 本研究分為兩部分。第一部分，利用熱注射法，將具有鎘(Cadmium)、硒(Selenium)、鋅(Zinc)和硫(Sulfur)元素的反應物先進行活化，形成錯合物，接著在高溫下反應，合成具有高亮度的CdSeZnS奈米粒子，依據調控組成比例得到放光位置在可見光的奈米粒子，量子產率可達70%以上，半高寬約35-50 nm，粒徑大小約在7-10 nm，並嘗試大量合成和降低成本。第二部分，將高亮度的CdSeZnS奈米粒子與具有四個硫醇基(-SH)的分子混合均勻，再加入聚合物單體和光起始劑(Photo initiator, PI)，經過強烈的紫外光照射，進行thio-ene reaction，使之交聯聚合(cross-linked)，量子點均勻分散在聚合物中，得到量子點-聚合物薄膜，另外，用熱起始劑(Thermal initiator)取代光起始劑，加溫使之交聯聚合，此方法可以避免光起始劑吸收波長與量子點吸收波長重疊問題，進而增加量子點的含量，其之後證明可應用在光電二極體(Light-Emitting Diode, LED)。

In recent years, nanotechnology has received much attention. When length of the material is less than 100 nanometers (nm), the quantum-confinement effect and unique quantum properties were exhibited. The zero-dimensional semiconductor nanomaterials (quantum dots) have an unique optical properties i.e. high quantum yield and narrow full-width at half-maximum. By a variety of quantum dots composition and size, the responding emission wavelengths of them are different. The light stability of sample shows better performance than conventional phosphors. Herein, the main goal of our study is to focus within two parts as follows. First, the Cd1-xZnxSe1-ySy quantum dots were synthesized via hot-injection approach. The reactants of Cadmium, Selenium, Zinc and Sulfur are being activated and then form metal-complexes, easily to react with following reactant. Then, the reaction maintains at high temperature lasting proper reaction time. After completion of reaction, high brightness CdSeZnS nanoparticles are successfully prepared. With different reacted composition, we can repeatedly obtain blue to red QDs, of which quantum yield (QY) and full width at half maximum (fwhm) of a composition-tunable Cd1-xZnxSe1-ySy quantum dots are up to 70-95% and 30-50 nm, respectively. The diameter of QDs are 7-10 nm. Thus, we attempt to produce large-scale QDs and reduce production cost. Second, the CdSeZnS QDs mixed with thio-modified monomer and then by adding other monomer and photo initiator for the photopolymerization of a thio crosslinker-encapsulated QDs and acrylate derivatives. After above-mentioned reaction, the thermal initiator reasonably replaces photo initiator and can slightly increase the concentration of QDs embedded in the resulting polymer. Finally, their latent potential as packaging materials for solid state light-emitting diode (LED) has preliminarily demonstrated.