Gutierrez-Portocarrero Salvador, Sauer Kiley, Karunathilake Nelum, Subedi Pradeep, Alpuche-Aviles Mario A
Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States.
Anal Chem. 2020 Jul 7;92(13):8704-8714. doi: 10.1021/acs.analchem.9b05238. Epub 2020 Jun 24.
We demonstrate the use of digital frequency analysis in single nanoparticle electrochemical detection. The method uses fast Fourier transforms (FFT) of single entity electrochemical transients and digital filters. These filters effectively remove noise with the Butterworth filter preserving the amplitude of the fundamental processes in comparison with the rectangle filter. Filtering was done in three different types of experiments: single nanoparticle electrocatalytic amplification, photocatalytic amplification, and nanoimpacts of single entities. In the individual nanoparticle stepwise transients, low-pass filters maintain the step height. Furthermore, a Butterworth band-stop filter preserves the peak height in blip transients if the band-stop cutoff frequencies are compatible with the nanoparticle/electrode transient interactions. In hydrazine oxidation by single Au nanoparticles, digital filtering does not complicate the analysis of the step signal because the stepwise change of the particle-by-particle current is preserved with the rectangle, Bessel and Butterworth low pass filters, with the later minimizing time shifts. In the photocurrent single entity transients, we demonstrate resolving a step smaller than the noise. In photoelectrochemical setups, the background processes are stochastic and appear at distinct frequencies that do not necessarily correlate with the detection frequency (), of TiO nanoparticles. This lack of correlation indicates that background signals have their characteristic frequencies and that it is advantageous to perform filtering a posteriori. We also discuss selecting the filtering frequencies based on sampling rates and . In experiments electrolyzing ZnO, that model nanoimpacts, a band-stop filter can remove environmental noise within the sampling spectral region while preserving relevant information on the current transient. We discuss the limits of Bessel and Butterworth filters for resolving consecutive transients.
我们展示了数字频率分析在单纳米颗粒电化学检测中的应用。该方法使用单个实体电化学瞬变的快速傅里叶变换（FFT）和数字滤波器。与矩形滤波器相比，这些滤波器通过巴特沃斯滤波器有效去除噪声，同时保留基本过程的幅度。在三种不同类型的实验中进行了滤波：单纳米颗粒电催化放大、光催化放大和单个实体的纳米撞击。在单个纳米颗粒的逐步瞬变中，低通滤波器保持步长高度。此外，如果带阻截止频率与纳米颗粒/电极瞬变相互作用兼容，巴特沃斯带阻滤波器会在尖峰瞬变中保留峰值高度。在单个金纳米颗粒催化肼氧化过程中，数字滤波不会使阶跃信号的分析复杂化，因为矩形、贝塞尔和巴特沃斯低通滤波器都能保留逐个颗粒电流的逐步变化，其中巴特沃斯滤波器能最小化时间偏移。在光电流单个实体瞬变中，我们展示了分辨出比噪声还小的步长。在光电化学装置中，背景过程是随机的，且出现在与TiO纳米颗粒的检测频率（）不一定相关的不同频率处。这种缺乏相关性表明背景信号有其特征频率，因此事后进行滤波是有利的。我们还讨论了基于采样率和来选择滤波频率。在模拟纳米撞击的电解ZnO实验中，带阻滤波器可以在采样光谱区域内去除环境噪声，同时保留有关电流瞬变的相关信息。我们讨论了贝塞尔和巴特沃斯滤波器在分辨连续瞬变方面的局限性。
