Wang Jianan, Zhang Xing, Li Hua, Wang Constance, Li Haoran, Keller Stacia, Mishra Umesh K, Nener Brett D, Parish Giacinta, Atkin Rob
School of Engineering, The University of Western Australia, Perth, WA 6009, Australia; School of Molecular Sciences, The University of Western Australia, Perth, WA 6009, Australia.
School of Engineering, The University of Western Australia, Perth, WA 6009, Australia.
J Colloid Interface Sci. 2021 Feb 1;583:331-339. doi: 10.1016/j.jcis.2020.09.036. Epub 2020 Sep 19.
The net surface charge of AlGaN/GaN structures, where AlGaN is in contact with the solution, is controlled by the pH-dependent protonation and deprotonation of the surface hydroxyl groups and possibly the electron-deficient surface electronic states. We hypothesize that atomic force microscopy (AFM) force measurements of ionic surfactant adsorption can reveal how the AlGaN surface properties vary with pH.
AFM force curves and images were used to probe the AlGaN/solution interface in water as a function of pH, and with added cationic surfactant cetyltrimethylammonium bromide (CTAB) or anionic surfactant sodium dodecylsulfate (SDS).
The AlGaN/solution interface is negatively charged at pH 12, has an isoelectric point near pH 5.5, and is positively charged at pH values less than 5.5. Surfactant adsorption data suggests AlGaN surface is somewhat hydrophobic at acidic pH. Compared to gallium nitride (GaN), at pH 2, AlGaN has a lower charge density and hydrophobicity, but at other values of pH, the surface properties of AlGaN and GaN are similar.
在AlGaN与溶液接触的AlGaN/GaN结构中，其净表面电荷由表面羟基的pH依赖性质子化和去质子化以及可能的缺电子表面电子态控制。我们假设，通过离子表面活性剂吸附的原子力显微镜（AFM）力测量可以揭示AlGaN表面性质如何随pH变化。
使用AFM力曲线和图像来探测水中AlGaN/溶液界面随pH的变化情况，并添加阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）或阴离子表面活性剂十二烷基硫酸钠（SDS）。
AlGaN/溶液界面在pH 12时带负电，在pH约5.5处有一个等电点，在pH值小于5.5时带正电。表面活性剂吸附数据表明，AlGaN表面在酸性pH下略显疏水。与氮化镓（GaN）相比，在pH 2时，AlGaN的电荷密度和疏水性较低，但在其他pH值下，AlGaN和GaN的表面性质相似。
