化学
超微电极
扫描电化学显微镜
电解质
电化学
电位滴定法
玻璃碳
无机化学
伏安法
化学工程
循环伏安法
分析化学(期刊)
电极
色谱法
工程类
物理化学
作者
Magdalena Michalak,Malgorzata Kurel,Justyna Jędraszko,Diana Toczydłowska,Günther Wittstock,Marcin Opałło,Wojciech Nogala
出处
期刊:Analytical Chemistry
[American Chemical Society]
日期:2015-11-10
卷期号:87 (23): 11641-11645
被引量:39
标识
DOI:10.1021/acs.analchem.5b03482
摘要
Nanoscale pH evaluation is a prerequisite for understanding the processes and phenomena occurring at solid–liquid, liquid–liquid, and liquid–gas interfaces, e.g., heterogeneous catalysis, extraction, partitioning, and corrosion. Research on the homogeneous processes within small volumes such as intracellular fluids, microdroplets, and microfluidic chips also requires nanometer scale pH assessment. Due to the opacity of numerous systems, optical methods are useless and, if applicable, require addition of a pH-sensitive dye. Potentiometric probes suffer from many drawbacks such as potential drift and lack of selectivity. Here, we present a voltammetric nanosensor for reliable pH assessment between pH 2 and 12 with high spatial resolution. It consists of a pyrolytic carbon nanoelectrode obtained by chemical vapor deposition (CVD) inside a quartz nanopipette. The carbon is modified by adsorption of syringaldazine from its ethanolic solution. It exhibits a stable quasi-reversible cyclic voltammogram with nearly Nernstian dependency of midpeak potentials (−54 mV/pH). This sensor was applied as a probe for scanning electrochemical microscopy (SECM) in order to map pH over a platinum ultramicroelectrode (UME), generating hydroxide ions (OH–) by the oxygen reduction reaction (ORR) at a diffusion-controlled rate in aerated phosphate buffered saline (PBS). The results reveal the alkalization of the electrolyte close to the oxygen reducing electrode, showing the insufficient buffer capacity of PBS to maintain a stable pH at the given conditions.
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