有別於均質材料(homogeneous material)展示整體材料性質一致的特性，非均質材料(heterogenous material)由於材料內部的性質會因空間上的組成或結構的差異，使材料的性質非均一而獲得特殊的應用性。本研究以兩種不同的方式製造新型態之非均質性材料: (1)逐層堆疊(Layer-by-layer, LBL)法製造高分子-金屬奈米晶體複合材料; (2)以晶核成長(seed mediated) 法合成具有非均質組成與結構之奈米晶體[1]。
逐層堆疊合成技術廣泛被應用於建構多成分組成之層狀結構材料，這些材料包含了聚合物、膠體粒子、生物分子。在近期逐層堆疊的技術被用來製備以高分子與奈米晶體堆疊形成層狀奈米複合材料，此複合材料是由兩個不互溶的高分子薄膜交互逐層堆疊組成。然而，利用兩種不互溶的高分子進行逐層堆疊形成之複合材限制了此合成法廣泛應用於製備各種奈米複合材料。本研究提供了一種創新的合成方法來製備多層堆疊的奈米複合材料，此奈米複合材料利用逐層堆疊技術交互堆疊高分子薄膜與電漿子奈米晶體陣列(plasmonic nanocrystal)形成具有多層奈米晶體陣列堆疊於均質高分子基質中之奈米複合材料。此製備技術需要在奈米晶體表面的配位殼層(ligand-shell)上與高分子基質間具有很強的吸引力(亦可稱為配位體與高分子基質間的弗洛里-哈金斯交互作用力(Flory−Huggins interaction parameter,χ<0)，藉由此作用力可以有效地增強多層堆疊結構中各層間的穩定性，並且調控各層內（intra-layer）或相鄰層間（inter-layer）相近的奈米晶體之間的距離進而控制奈米晶體的耦合效應(coupling)來製備光學可調性之奈米複合材料，其中各層內奈米晶體之間的距離可藉由二維奈米晶體的堆積密度加以控制，而奈米晶體在相鄰層間之距離可藉由調整高分子層厚度加以控制。此實驗結果提供了一個方法在均質高分子基質中設計具有可控性且結構複雜的奈米複合材料。
另一種合成非均質材料的方式是以第一種材料為晶核(seed)與其上生成第二種材料，例如以金屬奈米晶體為晶核於其上生成雙金屬(bimetallic)或半導體-金屬之非均質奈米晶體。此晶核成長方法(seed-mediated method)在控制非均質奈米晶體之大小、形狀、組成上展示其優異的精確性。然而，以晶核成長方法於合成高均勻度的非均質奈米晶體，仍有許多問題需要克服，例如晶種的尺寸和形狀分佈不均的情況，以及晶種在反應溶液中的分散性不佳。我們使用了創新的方法來解決晶種尺寸分布、分散性的問題，此法是藉由將尺寸分布均勻的奈米晶體規則分散並且固定於具有高分子基質的矽或玻璃基板上，以此複合材料之基板作為反應模板，將其置入反應溶液中形成非均質奈米晶體，反應過程中此高分子基質充當非均相界面來抑制反應之生成，進而生成多種獨特型態的非均質奈米晶體。例如：將銀奈米立方體(AgNCs)規則排列並且嵌入聚苯乙烯基質中，然後將其置入在Au3+離子水溶液中進行反應，以生成非均質的Au-Ag合金奈米晶體。根據精密控制反應條件，如AgNC在高分子基質中的嵌入深度、還原劑濃度、Au3+離子濃度等，可以合成出許多不同的形貌的Au-Ag 合金奈米晶體，如：花狀(flower-like)、蘑菇狀(mushroom-like)與半框架狀(half-cage)等奈米晶體。這些非均質奈米晶體獨特的形貌源於以下兩種反應相互競爭下的產物：（1）Au3+離子在反應溶液中進行還原反應並沉積在AgNC表面上（2）Au3+離子直接在AgNC表面進行與銀原子進行電置換反應(galvanic replacement reaction)。此方法使得設計具有獨特且多功能特徵的非均質奈米晶體變的更加簡便。

Heterogeneous materials have special applications due to the spatial composition or structural differences in the internal properties of the materials. In this study, new types of heterogeneous materials were fabricated in two different ways: (1) Layer-by-layer (LBL) method to fabricate polymer-metal nanocrystalline composites; and (2) seed mediated method to synthesize nanocrystals with heterogeneous composition and structure.
This study provides an innovative approach to prepare multilayer nanocomposite materials, which utilize a layer-by-layer stacking technique to interactively stack polymer films and plasmonic nanocrystal arrays to form nanocomposite materials with multilayer nanocrystal arrays stacked in a homogeneous polymer matrix. This technique requires a strong attractive force between the ligand-shell on the surface of the nanocrystal and the polymer matrix (also known as the Flory-Huggins interaction parameter (χ<0) between the ligand and the polymer matrix).This force can effectively enhance the stability of each layer in nanocomposite, and regulate the distance between nanocrystals in close proximity to each intra-layer or inter-layer to produce nanocomposite materials with optical tunability.
Another way to synthesize heterogeneous materials is to generate a second material on top of the first material as a nucleus. This seed-mediated method demonstrates excellent precision in controlling the size, shape, and composition of heterogeneous nanocrystals. We have used an innovative method to solve the problem of size distribution and dispersion of seeds by regularly dispersing and immobilizing uniformly sized nanocrystals on a substrate with a polymer matrix and using this composite material as a reaction template to form heterogeneous nanocrystals in the reaction solution. The polymer matrix acts as a heterogeneous interface during the reaction to inhibit the formation of the reaction. In this study, silver nanocubes (AgNCs) were arranged regularly and embedded in a polystyrene matrix, which was then placed in an aqueous Au3+ ionic solution for the reaction to produce heterogeneous Au-Ag alloy nanocrystals. For example, flower-like mushroom-like and half cage-like. This method makes it easier to design heterogeneous nanocrystals with unique and versatile features.

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