除去氣體對於奈米碳管與水混和物之影響

Abstract

疏水交互作用（hydrophobic interaction）被認為是非極性物質在水中會聚集的主要原因。已知水中的氣體是可以對該作用有增益的效果。若將疏水顆粒混合於水中，則除去氣體的混合物較富含空氣的混合物有較長的生命期。本研究以單層及多層奈米碳管的水混合物為材料，實驗除去氣體對於碳管與水混合物的影響。碳管於水中的生命期與所形成之結構是以攝影與動態光散射進行觀測。實驗中發現：除去氣體後，單層碳管於水中聚集的速率較未除氣的混合物中慢，且形成較緻密的碳管團塊。多曾碳管若未進行除氣，則碳管於水中形成類凝膠(gel-like)結構；此結構在除去氣體的碳管與水混合物中較未除氣者不明顯。實驗中所觀察到，除去氣體對單層與多層碳管的水混合物所產生之影響，是可以被石墨基板上所發現的表面奈米氣泡（surface nanobubble）解釋的。

The hydrophobic interaction causes the aggregation of non-polar materials in water. This interaction can be enhanced by the existence of gas in water; the dispersion of hydrophobic particles have longer lifetime in degassed water than in air-rich water. We study the gas-enhanced hydrophobic interaction in both single-walled and multi-walled carbon nanotubes/water mixture with and without degassing. The lifetime and structure in carbon nanotube aggregates observed by photography and multi-angle dynamic light scattering. The single-walled carbon nanotubes (SWNTs) aggregate slower and form more compact clumps in water with degassing than without degassing. The multi-walled carbon nanotubes (MWNTs) form gel-like structure in the air-containing MWNT/water mixture; this gel-like structure is less significant in degassed MWNT/water mixture. The observation can be explained with the presence of the surface nanobubbles on graphene substrates, which is similar to the walls of the carbon nanotubes, when the water is not degassed.