一維硒-二氧化矽奈米串珠核殼結構之合成 ：實心及空心二氧化矽奈米球結構

The Synthesis of One-dimensional Se-silica Bead-like Nanostructures with Solid or Hollow Silica Nanospheres

劉語慈(Yu-Tzu Liu)

指導教授 ： 王崇人

國立中正大學/理學院/化學暨生物化學系/碩士(2014年)

摘要

我們過去開發之一維硒奈米粒子合成方法，已說明可得到特殊區段式晶相之結構，而此一維奈米硒經由表面修飾後可得到特殊魚標狀核殼結構，然而在硒奈米線的例子可得串珠之結構，但是該製程上一直有聚集現象尚未克服。為此，本研究分為兩部分去探討，第一部分為合成分散的一維硒-二氧化矽奈米串珠核殼結構（1D-Se@segmented-SiO2 spheres；1D-Se@s-SS），並探討此結構與長度的關係。第二部分為操控合成具有實心或空心二氧化矽之1D-Se@s-SS奈米串珠核殼結構，並展示該奈米結構物在選擇性反應的初步結果。
首先，我們選用結構特殊且分散的一維硒奈米粒子做為起始物，長度範圍操控介於500 nm至4000 nm之間，接著利用傳統溶膠-凝膠法製備而得1D-Se@s-SS奈米串珠核殼結構，由TEM分析得知隨著不同長度分布之一維硒奈米粒子起始物，除了表面鍍上一層厚度均勻的二氧化矽殼層外，還會得到不同顆粒數的二氧化矽球，在此也提供一維硒奈米粒子晶相具連續區段式（tSe-mSe-tSe）n的另一證據。經由統計得知二氧化矽球之間的平均間距為647 ± 276 nm，二氧化矽球平均直徑為197 ± 24 nm。於第二部分，經由操控溶膠-凝膠法所用起始物之水解縮合程度，我們可成功合成具有實心或空心二氧化矽球之1D-Se@s-SS奈米核殼結構。溶膠-凝膠法所用起始物水解縮合程度的操控，可經由加入微量水與適量鹼為之。我們同時展示對兩種奈米串珠硒核殼結構進行厚度的操控，透過改變溶膠-凝膠法所用起始物之添加量，觀察其二氧化矽球之厚度。於實心的情況，厚度109 - 182 nm；於空心的情況，殼層厚薄可操控介於13至45 nm之間，而其內徑維持一致約93 nm，證實先前所主張之一維硒奈米粒子本身具有連續區段式之晶型變化，進而造成所使用的穩定劑於單一晶型的表面發生凝結的現象，因而導致連續區段式二氧化矽球之生成。最後，我們展示對於奈米串珠核殼結構之選擇性反應部分所達成的初步認識，透過選用不同厚度之奈米串珠核殼結構作為前驅物，以聯胺作為侵蝕反應試劑，發現當t-Se厚度小於5 nm時，主要以移除m-Se為主；當t-Se厚度達15 nm時，則該侵蝕反應主要以移除t-Se為主。

關鍵字

奈米串珠核殼結構 ； 溶膠-凝膠法 ； 一維硒奈米粒子

並列摘要

The synthesis of one-dimensional selenium nanoparticles with unique segmented monoclinic (m) and trigonal (t) cystal phases has been demonstrated previouly. Such segmented crystal phase nanostructure was evidenced while the selenium surface was coated by silica via sol-gel process. The products own a unique nanofloat structure with typically one solid or hollow silica nanosphere located at the middle of individual selenium nanorod. To extend the above findings, we report herein two series of studies : First, the synthesis of dispersed one-dimensional Se-silica bead-like nanostructures (1D-Se@segmented-SiO2 spheres; 1D-Se@s-SS) in more detail, particularly for the cases containing Se nanowires. Meanwhile, we demonstrated the evolution of such bead-like nanostructure from Se nanorods to nanowires in terms of both the number of beads and their mean spacing. Secondly, a series of studies were conducted in order to describing the detailed formation mechanism for the bead-like 1D-Se@s-SS nanostructures with solid or hollow silica nanospheres. In addition, we demonstrated the results of our preliminary studies regarding their selective reactivity towards the selenium removal reactions.
In the first part, one-dimensional selenium nanoparticles with the average lengths ranging from 500 nm to 4000 nm were used as the starting material and the bead-like 1D-Se@s-SS nanostructures with good dispersivities were synthesized using sol-gel method. The results indicated that the number of beads increases accordingly to the increase of the length for the 1D nano-Se. Also, the averaged diameters of the silica nanospheres are of 197 ± 24 nm and the averaged spacings between two adjacent silica nanospheres are of 647 ± 276 nm. They provided a more clear picture regarding the segmented cystal-phase of the 1D nsnoSe, (tSe-mSe-tSe)n. In the second part, we demonstrated the formation of the bead-like 1D-Se@s-SS nanostructures with solid or hollow silica nanospheres can be achieved by the use of the starting material (mercaptopropyl trimethoxysilan, MPTMS) for the sol-gel process with a carefully controlled extent of its hydrolysis/condensation prior to the silica coating. It was sensitive to the humidity and pH value, the aging of the starting chemicals, and the trace amount of water/NaOH added. The bead-like 1D-Se@s-SS nanostructures with hollow silica nanospheres can be synthesized by using relatively fresh MPTMS, or less extent of the hydrolysis/condensation, and a subsequent wash by ethanol. Meanwhile, the thickness of the silica shells can be controlled from the sol-gel process to obtain in a range from 13 to 45 nm and the inner diameters are roughly constant in size of ca. 93 nm. This constant averaged inner diameter was attributed to the existence of the condensation of the nanoparticle stabilizing agent (carboxymethylcellulose, CMC) at the m-Se sites. Finally, we demonstrated the results of our preliminary studies of the selective reactivity in the chosen system of the bead-like 1D-Se@s-SS nanostructures with solid silica nanospheres. The reactants were prepared containing different thickness at the surface of t-Se. The Se etching reaction, resulting in the Se removal, was chosen in this demonstration. Our results indicated that the removal of Se occurred at the m-Se while the thickness was less than 5 nm, and at the sites of t-Se while the thickness was greater than 15 nm.

並列關鍵字

sol-gel process ； one-dimensional selenium nanoparticles ； bead-like nanostructure

參考文獻

20.Chen, C.C; Chao, C.Y.; Lang, Z. H. Chem.Mater.2000, 12, 1516-1518.

39.Yeh, Y.-Q.; Chen, B.-C.; Lin, H.-P.; Tang, C.-Y. Langmuir 2005, 22, 6-9.

3.Lieber, C. M.; Wang, Z. L. MRS Bull. 2007, 32, 99-108.

35.Zhang, H. G.; Zhu, Q. S.; Zhang, Y.; Wang, Y.; Zhao, L.; Yu, B. Adv. Funct. Mater. 2007, 17, 2766−2771.

8.Chen, L.; Zhang, W.; Feng, C.; Yang, Z.; Yang, Y., Industrial & Engineering Chemistry Research 2012, 51 (11), 4208-4214.