Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
Phys Chem Chem Phys. 2011 Nov 28;13(44):19848-55. doi: 10.1039/c1cp21855g. Epub 2011 Aug 31.
Desorption of carbon tetrachloride from beneath an amorphous solid water (ASW) overlayer is explored utilizing a combination of temperature programmed desorption and infrared spectroscopy. Otherwise inaccessible information about the dewetting and crystallization of ASW is revealed by monitoring desorption of the CCl(4) underlayer. The desorption maximum of CCl(4) on graphene occurs at ~140 K. When ASW wets the CCl(4) no desorption below 140 K is observed. However, the mobility of the water molecules increases with ASW deposition temperature, leading to a thermodynamically driven dewetting of water from the hydrophobic CCl(4) surface. This dewetting exposes some CCl(4) to the ambient environment, allowing unhindered desorption of CCl(4) below 140 K. When ASW completely covers the underlayer, desorption of CCl(4) is delayed until crystallization induced cracking of the ASW overlayer opens an escape path to the surface. The subsequent rapid episodic release of CCl(4) is termed a "molecular volcano". Reflection absorption infrared spectroscopy (RAIRS) measurements indicate that the onset and duration of the molecular volcano is directly controlled by the ASW crystallization kinetics.
利用程序升温脱附和红外光谱法研究了在非晶态水 (ASW) 覆盖层下四氯化碳的解吸。通过监测底层 CCl(4) 的解吸，揭示了有关 ASW 去湿和结晶的其他无法获得的信息。CCl(4) 在石墨烯上的解吸最大值出现在约 140 K。当 ASW 润湿 CCl(4 时，在 140 K 以下观察不到解吸。然而，水分子的流动性随着 ASW 沉积温度的增加而增加，导致水从疏水性 CCl(4)表面热力学驱动的去湿。这种去湿使一些 CCl(4 暴露在环境中，允许在 140 K 以下无阻地解吸 CCl(4。当 ASW 完全覆盖底层时，CCl(4 的解吸被延迟，直到 ASW 覆盖层的结晶诱导开裂为表面开辟了一条逃逸途径。随后迅速发生的 CCl(4 突发性释放被称为“分子火山”。反射吸收红外光谱 (RAIRS) 测量表明，分子火山的起始和持续时间直接受 ASW 结晶动力学的控制。
