Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.
Anal Chim Acta. 2013 Aug 20;792:110-4. doi: 10.1016/j.aca.2013.07.007. Epub 2013 Jul 8.
Poly (N-isopropylacrylamide)-co-acrylic acid (pNIPAm-co-AAc) microgels were "painted" on the Au electrode of a quartz crystal microbalance (QCM). Another Au layer (overlayer) was subsequently deposited on the microgel layer. This structure is known as a microgel-based etalon. These devices have been shown to exhibit optical properties (i.e., color) that depend on solution pH and temperature, among other things. Previously, we measured QCM frequency shifts that are a result of solution pH changes; the frequency shifts are a direct result of the pH dependent solvation state of the microgels that make up the etalon. In fact, the shifts observed for the etalons were much greater in magnitude than just a microgel layer immobilized on the QCM crystal without the Au overlayer. We reasoned that the Au overlayer lead to an enhancement of the observed frequency change due to its mass. In this submission we investigate how the Au overlayer thickness (mass) affects the observed sensitivity to solution pH. We found that the change in QCM resonant frequency depended dramatically on the mass of the Au overlayer.
聚（N-异丙基丙烯酰胺）-共-丙烯酸（pNIPAm-co-AAc）微凝胶被“涂”在石英晶体微天平（QCM）的 Au 电极上。随后，在微凝胶层上沉积了另一层 Au（覆盖层）。这种结构被称为基于微凝胶的标准具。这些器件已被证明具有光学性质（即颜色），这些性质取决于溶液 pH 值和温度等因素。以前，我们测量了由于溶液 pH 值变化而导致的 QCM 频率偏移；这些频率偏移是构成标准具的微凝胶的 pH 值依赖性溶剂化状态的直接结果。事实上，与仅仅将微凝胶层固定在没有 Au 覆盖层的 QCM 晶体上相比，观察到的标准具的偏移幅度要大得多。我们推断 Au 覆盖层由于其质量而导致观察到的频率变化增强。在本提交中，我们研究了 Au 覆盖层厚度（质量）如何影响对溶液 pH 值的观察灵敏度。我们发现，QCM 共振频率的变化强烈依赖于 Au 覆盖层的质量。
