本實驗的目的在開發一種高產量的水溶性ZnS:Mn2+量子點製程。我們將高濃 度的氯化鋅與硫化鈉水溶液逐滴加入當作緩衝溶液的乙二醇中，並控制反應時的 pH 值，會得到白色不透明的硫化鋅。將沉澱物用去離子水清洗後，離心取出沉 澱物，進行XRD 作晶體鑑定，可以確定產物為硫化鋅的閃鋅礦(zinc-blend)結構。 從結晶峰的半高寬估計其晶粒大小在2~4nm 之間。我們也發現在酸性中合下的 產物，粒子粒徑分佈較窄且小。 將上述清洗過之硫化鋅產物，再利用MPA 於水溶劑中進行改質，可得到 ZnS:Mn2+@MPA 水溶性量子點。此一量子點可分散在pH=6~11 的水中呈現透明狀。 由UV-abs 的起始吸收波長可計算出結晶大小在4~7nm 之間。而TEM 觀察的結果 也顯示出單顆結晶大小在5~7nm。 我們也嘗試了在不同的鋅硫比例下進行反應，發現在硫原子過量的情況下， 結晶會變大且會降低420nm 的藍光放射。另外，也試著將MPA 在合成的過程中加 入。使MPA 不僅當做改質劑，也當作保護劑使用。在鹼性合成(pH>10.8)下，MPA 的硫醇基團會解離，而與鋅有較強鍵結能力。但添加有MPA 並且在鹼性下進行反 應者，硫化鋅產物之結晶性會大幅降低。同樣先添加MPA 而在酸性下合成者，XRD 繞射強度較高，且UV-abs 也有相當明顯的吸收峰。從起始吸收波長計算出的結 晶大小為3.7nm。所以整體而言，應該在酸性條件下進行硫化鋅沉澱才可以獲得 較小及較整齊之結晶。 The purpose of this research is to develop a low-cost, low environmental impact, and high yield of ZnS: Mn2 + QDs process. ZnS: Mn2 + QD were successfully prepared by neutralizing aqueous solution of zinc chloride and sodium sulfide under controlled the pH value. Using XRD to identify the crystal shows that the product was ZnS sphalerite (zinc-blend) structure, whose domain size is only 2~3nm calculated from the power XRD peak width. ZnS: Mn2 + QD was washed by deionized water, centrifuged out the sediment, and modified by MPA aqueous. The obtained ZnS: Mn2 +@ MPA QDs can be dispersed in water. The transparent dispersed solution crystal size also calculated by on-set of the UV-abs absorption, it shows that crystal size was between 4 ~ 7nm. TEM observation also showed that the size of a single crystal in 5 ~ 7nm. We also tried to add different ratio of Zn/S. We found that when sulfur atoms were excess, it will cause crystal size became larger and reduces the 420nm blue light radiation. We not only use the MPA as a modifier, but also try to add it as a protective agent during synthesis process. Although the pH value of synthesis under the alkaline (pH> 10.8), MPA will dissociate its thiol groups and enhance its bonding ability. However, we found that will significantly reduce the crystallization of zinc sulfide. But under acid synthesis, XRD showed that the larger diffraction intensity. UV-abs also had quite obvious absorption peak, calculated by on-set of the UV-abs absorption, crystal size was 3.7nm.
