高透明性有機系奈米鑽石懸浮液的製備

藉由爆炸法合成的超分散奈米鑽石(ultradispersed nanodiamond)帶有許多非鑽石碳相，這些非鑽石碳相是硬團聚(tight agglutinates)的來源，更由於這些硬團聚而降低了奈米鑽石的應用範圍。欲提升其應用性，則必須將奈米鑽石進行解團聚處理(Deagglomeration)。拉曼光譜顯示出熱氧化(thermal oxidation)後的奈米鑽石，非鑽石碳相將隨著處理時間的增加而減少。霍式轉換紅外線光譜與Zeta potential曲線可推論奈米鑽石表面也衍生出大量的路易士酸位置(Lewis acid sites)。從UV-vis吸附量測試結果可得知，熱氧化奈米鑽石的表面呈現酸性，有利於添加鹼性官能基分散劑進行表面修飾。以油胺為分散劑添加進四氫呋喃溶劑中，並進行濕式珠磨法可製備出低團聚的奈米鑽石懸浮液，其粒徑僅有25 nm左右且具有高度透光性。從霍式轉換紅外線光譜中發現，油胺會吸附在奈米鑽石表面形成離子鍵結(zwitterionic bond)，並在中極性的四氫呋喃溶劑中分散良好。此外，我們也嘗試在其他中極性有機溶劑(acetone、MEK)中進行相同的研磨處理，亦能達到25 nm的低團聚粒徑，經由此一簡單的處理方式，得到具有高度懸浮穩定性的有機系透明懸浮液，該懸浮液可望應用在光學材料上。

關鍵字

超分散奈米鑽石；分散性；表面修飾；濕式珠磨法

並列摘要

In recent years, the detonation nanodiamond has received increased attention in the applications of abrasive pastes and suspensions for high-precision polishing, nanofluids for thermal conduction and nanodiamond–polymer composites for wear–resistant surface coatings, thermal conduction coatings, transparent coatings and biological implant coatings. However, the typical detonation nanodiamond has an extremely small particle size of about 4–5 nm and usually forms micro-sized aggregates. Thus, its applications will be hindered if the aggregates are not broken up. To disperse the nanodiamond powder in organic solvents, an easy process of oxidizing the powder at 420℃ for 3 hours and then dispersing it into solvents by beads–milling with addition of amino–containing surfactants is used in this investigation. The results of Fourier transform infrared spectroscopy and zeta potential measurements confirm that an apparent amount of Lewis acid sites composed of mainly carboxylic acid and cyclic acid anhydrides are derived on the surface of thermally oxidized nanodiamonds (T–ND). This acid sites–derived T–ND is chemically active, favoring the formation of the ionic zwitterion with the amino–containing surfactants such as oleylamine (OLA) and octadecylamine (ODA). After being dispersed with surfactants of OLA or ODA, the T–ND shows good dispersion stability in organic solvents; However, the dispersion efficiency of the saturated ODA is not as good as that of the unsaturated OLA. By using the dispersant of OLA accompanied with de–agglomeration by beads-milling, a clear colloidal solution of T–ND in solvents of tetrahydrofuran, methyl ethyl ketone or acetone can be easily attained and stabilized for at least three months.

並列關鍵字

ultradispersed nanodiamond ； dispersibility ； surface modification ； beads milling method

參考文獻

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高透明性有機系奈米鑽石懸浮液的製備

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