A Fast Electrochemical Quartz Crystal Microbalance,which Acquires Frequency and Bandwidth on Multiple Overtones
A Fast Electrochemical Quartz Crystal Microbalance,which Acquires Frequency and Bandwidth on Multiple Overtones
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快速电化学石英晶体微天平采集多个泛音的频率和带宽
DOI：
10.1002/elan.201600580
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发表时间：
2017
期刊：
影响因子：
3
通讯作者：
D. Johannsmann
中科院分区：
文献类型：
--
作者：
J. Petri;Sebastian Hochstädt;T. Nentwig;A. Pausch;A. Langhoff;D. Johannsmann
介绍了一种电化学石英晶体微天平 (EQCM)，它可以以 10 毫秒的时间分辨率测量多个谐波的频率和带宽变化。该技术要求所研究的过程是重复的。例如方波电流分析法和循环伏安法。数据采集速度很快，因为原始数据由固定频率下的电导纳迹线组成。在晶体谐振周围均匀间隔的一组频率处顺序采集一些（〜10）这样的时间轨迹。由于所有时间轨迹均由相同的重复过程触发，因此可以事后生成来自恒定时间延迟 t 的电导 G(ωi, t) 和电纳 B(ωi, t) 与频率的关系图。位移 ΔG(ωi) 和 ΔB(ωi) 量化了与样本的参考状态和时间 t 时的状态有关的两条共振曲线之间的差异。将两条谐振曲线的差异与这些数据进行拟合，即可获得频率偏移 Δf(t) 和带宽偏移 ΔΓ(t) 随时间的变化。对于不同的泛音重复此过程。考虑到这一过程的重复性，可以进行累积和平均，从而将噪声降低至几十毫赫兹。该仪器的功能通过两个示例进行了演示，即铜沉积/溶解和含有弱酸性侧基的聚合物薄膜的电响应性。
An electrochemical quartz crystal microbalance (EQCM) is described, which measures the shifts of frequency and bandwidth on multiple harmonics with a time-resolution of 10 milliseconds. The technique requires the process under study to be repetitive. Examples are square wave amperometry and cyclovoltammetry. Data acquisition is fast because the raw data consist of traces of the electrical admittance at fixed frequencies. A few (∼10) such time traces are acquired sequentially at a set of frequencies evenly spaced around the crystal's resonance. Since all time-traces are triggered by the same repetitive process, plots of the conductance G(ωi, t) and the susceptance B(ωi, t) from constant time delays, t, versus frequency can be produced a posteriori. The shifts, ΔG(ωi) and ΔB(ωi) quantify a difference between two resonance curves, pertaining to the sample's reference state and the state at time t. Fitting a difference of two resonance curves to these data, one obtains shifts of frequency, Δf(t) and shifts of bandwidth, ΔΓ(t), versus time. This procedure is repeated for the different overtones. Given the repetitive nature of the process, one may accumulate and average, which lowers the noise down to a few tens of mHz. The capabilities of this instrument are demonstrated with two examples, which are copper deposition/dissolution and electro-responsivity of a polymer film containing weakly acidic side groups.