動態光散射在氣體對亞微米尺度膠體分散體穩定性的影響的研究

Abstract

我們研究氣體對膠體分散體問定性的影響。分別使用油(dodecane and squalane)和多層奈米碳管作為分散向，使其分散在水或是去氣體水中，樣品中不加入界面活性劑。利用動態光散射溶液中的油滴或是碳管團塊的大小進行量測，以觀察膠體溶液的穩定度。我們架設了一台動態光散射儀，並使用直徑38nm、500nm、1μm的聚苯乙烯小球進行校正。從指數函數與累積量展開擬合可以得到與樣品相符合的粒徑大小。但CONTIN的分析結果，無法確定可以得到愈樣品相符合的粒徑分布。在使用油進行的無界面活性劑乳膠溶液的實驗中，我們發現與水相比在去起體水中，油可以較容易的形成很小的油滴並可以較穩定的分散在水中，並在完成的乳膠溶液中加入氣體，對樣品的穩定性影響不大。在使用多層奈米碳管的實驗中，我們發現使用去起體水可以做出至少能穩定存在半個月的奈米碳管膠體分散體；而若是使奈米碳管膠體分散體與空氣劇烈混合，則會有明顯的聚合、沉澱現象。We study effect of gas presence on the stability of colloidal dispersions by using two kinds of colloidal particles, surfactant-free oil droplets and Multi-Walled Carbon Nanotubes (MWNTs) dispersed in degassed or regular deionized (DI) water. Dodecane and squalane are used in surfactant-free oil-in-water emulsion. The technique of dynamic light scattering (DLS) is employed to measure the size evolution of oil droplets and MWNT aggregates. We constructed a DLS system and calibrated it with polystyrene spheres having diameters 38nm, 500nm, and 1000nm. In the calibration, we fit the autocorrelation functions with the exponential decay, the cumulant expansion, and a widely used program CONTIN. The exponential decay and the cumulant expansion yield reasonable particle sizes but CONTIN does not give consistent results. For surfactant-free oil-in-water emulsions, we find that the oil droplets dispersed in degassed DIwater are more stable than those in regular DI water. Once the emulsions are made, mixing them with N2 gas does not significantly alter the droplet stability. For MWNT suspensions, samples made with degassed water can be stable at least for half a month. However, violent shaking in presence of air or injection with air leads to visible aggregation in short time.