疏水性表面奈米泡泡之分子動力學模擬

表面奈米泡泡在傳統理論上是個不穩定的系統，因為擁有很小半徑的奈米泡泡會有非常大的拉普拉斯壓力的泡泡，所以被預測會在幾個微秒時間內就會溶解。但是實驗上我們可以觀察到存在幾個小時甚至到一兩天的穩定表面奈米泡泡。因此，我們想要利用分子動力學模擬去模擬以及分析此系統，試著找出其穩定的原因。我們模擬SPC/E 模型之水分子和氬氣在石墨表面形成之奈米氣泡。與前人的只有12-6 勢溶解劑的模擬相比，我們做出了在沒有表面釘住效應下穩定超過一百奈秒的表面奈米泡泡，而只有12-6勢的溶劑溶質系統在沒有表面釘住效應下則是會在十秒內消失。兩者最大的不同在於是否有氫鍵效應的存在，因此我們研究了水的偶極方向發現在水和氣體界面有特殊的結構，也在水氣界面上看到了氣體的聚集現象。在氣體和固體的介面上，有一層氣體豐富層，我們用朗繆耳模型去解釋此層與相對應上方泡泡內部之間的密度關係，探討了氣體豐富層提供了取代釘住效應的基底來維持泡泡的穩定。

關鍵字

奈米泡泡；疏水性表面；分子動力學模擬

並列摘要

We study the formation and stability of surface nanobubbles by molecular dynamics simulation with SPC/E water model and argon gas near a hydrophobic graphite solid surface. Our results indicate nanobubbles can be stable without any artificially-introduced surface pinning for longer than ninety nanosecond, whereas previous simulations with binary mixtures consisting of Lenard-Jones (LJ) particles showed the nanobubbles dissolve in less than ten nanosecond. This is attributed to hydrogen bond formation near the water-gas interface, which plays an important role in our simulation. We also found that the argon particle accumulate near the liquid-gas interface, which is unobserved in the LJ binary particle model. We also investigate properties in the interface region, including the argon-solid and argon-water interface to figure out the stability of surface nanobubble. The lowering surface tension due to hydrogen bond can stabilize the bubble. Also, the enrichment layer on the argon-solid interface can supply a stable basement instead of the demand of hydrophilic site in our simulation.

並列關鍵字

Interfacial nanobubble ； Hydrophobic Surface ； MD Simulation ； SPC/E water

參考文獻

[1]Parker, J. L.; Claesson, P. M.; Attard, P. Bubbles, Cavities, and the Long-Ranged Attraction between Hydrophobic Surfaces. J. Phys. Chem. 1994, 98, 8468−8480.

[3]Ishida, N.; Inoue, T.; Miyahara, M.; Higashitani, K. Nano Bubbles on a Hydrophobic Surface in Water Observed by Tapping-Mode Atomic Force Microscopy. Langmuir 2000, 16, 6377−6380.

[4]Michiel A. J. van Limbeek ; James R. T. Seddon. “Surface Nanobubbles as a Function of Gas Type” Langmuir, 2011, 27 (14), pp 8694–8699

[5]Ljunggren, S. and Eriksson, C., “The lifetime of a colloid-sized gas bubble in water and the cause of the hydrophobic attraction” Colloids and Surface A, Vol. 129-139, pp. 151-155, 1997

[6]Zhang, X. H.; Maeda, N.; Craig, V. S. J. Physical Properties of Nanobubbles on Hydrophobic Surfaces in Water and Aqueous Solutions. Langmuir 2006, 22, 5025−5035

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疏水性表面奈米泡泡之分子動力學模擬

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