Revalesio Corporation , 1200 East D Street, Tacoma, Washington 98421, United States.
ACS Nano. 2014 Jun 24;8(6):6193-201. doi: 10.1021/nn5016049. Epub 2014 Jun 2.
Currently there is no widespread agreement on an explanation for the stability of surface nanobubbles. One means by which several explanations can be differentiated is through the predictions they make about the degree of permeability of the gas-solution interface. Here we test the hypothesis that the gas-solution interface of surface nanobubbles is permeable by experimental measurements of the exchange of carbon dioxide. We present measurements by attenuated total reflection Fourier transform infrared (ATR-FTIR) and atomic force microscopy (AFM), demonstrating that the gas inside surface nanobubbles is not sealed inside the bubbles, but rather exchanges with the dissolved gas in the liquid phase. Such gas transfer is measurable by using the infrared active gas CO2. We find that bubbles formed in air-saturated water that is then perfused with CO2-saturated water give rise to distinctive gaseous CO2 signals in ATR-FTIR measurements. Also the CO2 gas inside nanobubbles quickly dissolves into the surrounding air-saturated water. AFM images before and after fluid exchange show that CO2 bubbles shrink upon exposure to air-equilibrated liquid but remain stable for hours. Also air bubbles in contact with CO2-saturated water increase in size and Ostwald ripening occurs more rapidly due to the relatively high gas solubility of CO2 in water.
目前，对于表面纳米气泡稳定性的解释还没有达成广泛共识。一种可以区分几种解释的方法是通过它们对气体-溶液界面渗透性的预测。在这里，我们通过二氧化碳交换的实验测量来检验表面纳米气泡的气体-溶液界面是可渗透的假设。我们通过衰减全反射傅里叶变换红外（ATR-FTIR）和原子力显微镜（AFM）进行了测量，证明了气泡内部的气体并未密封在气泡内，而是与液相中的溶解气体进行了交换。这种气体转移可以通过使用红外活性气体 CO2 进行测量。我们发现，在空气饱和的水中形成的气泡，然后用 CO2 饱和的水进行灌注，会在 ATR-FTIR 测量中产生独特的气态 CO2 信号。此外，纳米气泡内的 CO2 气体很快溶解在周围的空气饱和水中。流体交换前后的 AFM 图像显示，CO2 气泡在暴露于空气平衡的液体中会收缩，但仍能稳定数小时。与 CO2 饱和水接触的空气泡也会增大，由于 CO2 在水中的相对高溶解度，奥斯特瓦尔德熟化过程会更快发生。
