本研究係利用化學還原法來合成奈米級銅微粉。研究中以硫酸銅為前驅物，探討前驅鹽濃度、還原劑添加量、保護劑種類及添加量、反應溫度、溶劑種類、鹼液的添加等變因對所生成銅微粉之晶態、粒徑大小、粒徑分佈及UV/Vis吸收等特性之影響。此外，亦合成銅銀微粉，將所得之金屬微粉摻入PVA膜中，並進行導電性之量測，以期瞭解銅微粉粒徑及添加量對PVA膜導電性之影響。

實驗結果顯示，以聯胺為還原劑，PVA和PVP為保護劑，可製備出面心立方晶系（f.c.c.）、粒徑3~80 nm之純銅微粉。隨著保護劑比例、前驅鹽濃度之增加，所得粒徑有縮小之趨勢。而隨著還原劑比例、反應溫度之增高，微粉粒徑會隨之增大。由IR和XAS的分析結果發現，PVA與銅之作用過於微弱因而保護效果不彰，而PVP則對銅粒子有明顯之保護作用。

以乙醇/水為溶劑之系統中，以PVP為保護劑時，所得粒徑(9nm)明顯較相同條件下水溶液系統中所得之粒徑(4 nm)大。此乃由於乙醇之添加會破壞溶液中PVP與銅微粒之作用，而造成保護效果減弱，因此所得粒徑增大。但無保護劑之情況下，則乙醇/水溶液系統所得之粒徑(51 nm)較水溶液系統中所得之粒徑(109 nm)為小，且隨著乙醇比例之提高，所得微粒中之氧化銅量越多。若加入NH4OH或NaOH等鹼液，並未能降低聯胺之用量，但在無保護劑之情況下，銅微粉之粒徑可控制在15nm以下。

以逐步還原法可合成核殼型銅銀(Cu core/Ag shell)微粉。由UV/Vis光譜分析可知，除411.7nm處為銀之吸收峰外，509.6nm處之肩部吸收為核殼型銅銀結構之特徵。當銅/銀莫耳比為1：4.83時，所製備之核殼型銅銀微粉粒徑約11nm，而銅核之粒徑為5nm。

導電性量測結果顯示，以粒徑17 nm銅微粉混摻之PVA複合膠膜，當銅粉添加量增加至0.2 wt%時，其導電度有巨幅躍升。當固定銅微粉混摻量為1%，改變不同的銅微粉粒徑時，發現粒徑愈小，導電度愈高。以銀微粉混摻PVA複合膠膜時，其導電度躍升點(0.2wt%)與混摻銅微粉時相同。以核殼型銅銀微粉混摻PVA複合膠膜之躍升點(0.1wt%)，較混摻銅或銀微粉都較低。此顯示核殼型銅銀微粉之混摻效果較佳。由TEM分析結果推測，可能係水洗乾燥後之銅銀微粉在PVA膠膜中之分散性較佳所致。

In this work, Cu nanoparticles were obtained by the chemical reduction of copper sulfate with hydrazine at room temperature. Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) were used as the protecting agents (PA). The influences of synthesis parameters, including copper sulfate concentration, [N2H4]/[Cu2+] ratio, [PA]/[Cu2+] ratio, solvent, atmosphere, temperature, and the addition of alkali on the resultant Cu nanoparticles were investigated. The shape, crystalline structure, particle size and particle size distribution of the as-prepared particles were characterized by TEM, XRD, HRAEM, and UV/Vis spectra analyses.
The results showed that the f.c.c. structured Cu nanoparticles sized ranging from 3 to 80 nm can be obtained in the presence of PA. The particle size was decreased with increasing the CuSO4 concentration and the [PA]/[Cu2+] ratio. On the contrary, the particle size was increased with the increase of [N2H4]/[Cu2+] ratio and temperature. According to the analyses of IR and XAS, it was found that Cu nanoparticles can not be efficiently protected by PVA due to their weak interaction. However, the Strong interaction of Cu with PVP caused the decreasing in the particle size of Cu nanoparticles.
In the case of ethanol/water as solvent, and with the presence of PVP, the resulting size (9nm) of Cu nanoparticles was obviously larger than that in the aqueous solution (4nm). This could be inferred that the presence of ethanol would weaken the interaction between PVP and Cu nanoparticles, which resulted in the increase of particle size. Whereas, the particle size (51nm) was smaller than that in the aqueous solution (109nm) in the absence of protecting agent. Furthermore, from the result of XRD analysis, trace CuO and Cu2O were found in the products at high [ethanol]/[H2O] ratio.
When NH4OH and NaOH were used as the alkaline solutions, although the [N2H4]/[Cu2+] ratio could not be reduced, the Cu nanoparticles with size smaller than 15nm could be obtained without protecting agent.
The Cu-core/Ag-shell nanoparticles had also been synthesized by successive chemical reduction method. The core-shell structure of the as-synthesized Cu/Ag nanoparticles could be confirmed by the UV/Vis absorption spectra. When the molar ratio of Cu/Ag was 1:4.83, the particle size of obtained Cu- core/Ag-shell nanoparticles was about 11nm, and that of Cu cores was about 5nm.
Metal doped PVA films, including Cu-PVA, Ag-PVA, and Cu/Ag-PVA films, were used to measure the conductivity. The result showed that for Cu-PVA and Ag-PVA films, as the dosage of Cu nanoparticles was increased up to 0.2wt%, the conductivity was risen dramatically. Besides, the conductivity was increased with decreasing the particle size. However, the dosage of abrupt rise was about 0.1wt% for Cu/Ag-PVA film, which was smaller than that for others. This was probably because the Cu/Ag nanoparticles were relatively well-dispersed in the PVA films.

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