Zhang Xue Hua
Department of Chemical and Biomolecular Engineering and Particulate Fluid Processing Center, University of Melbourne, Melbourne, 3010, Australia.
Phys Chem Chem Phys. 2008 Dec 7;10(45):6842-8. doi: 10.1039/b810587a. Epub 2008 Oct 3.
The applications of quartz crystal microbalance (QCM) to the study of surface and interfacial science such as adsorption have become progressively common and popular these days. In this work, QCM with dissipation monitoring was used to study the formation of nanobubbles on bare and thiol-coated gold surfaces. The nanobubbles were produced using one of the established solvent exchange protocols and the formation was first confirmed by the tapping mode atomic force microscopy (AFM). By QCM measurements, we found that the formation of nanobubbles on the hydrophobic crystal surfaces can yield easily detectable shifts of frequency and dissipation from those measured directly in water without the presence of nanobubbles. The direction of the shifts is consistent with the depletion of water by gases of lower density. We also found that the formation of nanobubbles is a fast process and can be finished in less than a minute. The response of QCM at several overtones showed that nanobubbles cannot be used to explain why the shift in the half bandwidth is sometimes smaller than the negative frequency shift at higher overtones when the QCM crystal is operated in liquids.
如今，石英晶体微天平（QCM）在诸如吸附等表面和界面科学研究中的应用已变得越来越普遍和流行。在这项工作中，采用具有耗散监测功能的QCM来研究裸金表面和硫醇包覆金表面上纳米气泡的形成。纳米气泡是使用已确立的溶剂交换方案之一产生的，其形成首先通过轻敲模式原子力显微镜（AFM）得到证实。通过QCM测量，我们发现疏水晶体表面上纳米气泡的形成会使频率和耗散相对于在无纳米气泡的水中直接测量时产生易于检测到的偏移。偏移方向与密度较低的气体导致的水的消耗一致。我们还发现纳米气泡的形成是一个快速过程，可在不到一分钟内完成。QCM在几个泛音处的响应表明，当QCM晶体在液体中运行时，纳米气泡无法解释为什么在较高泛音处半带宽的偏移有时小于负频率偏移。
