Department of Inorganic and Analytical Chemistry, University of Geneva , Quai Ernest-Ansermet 30, CH-1211 Geneva, Switzerland.
Anal Chem. 2015 Sep 1;87(17):8640-5. doi: 10.1021/acs.analchem.5b01941. Epub 2015 Aug 20.
While ion to electron transducing layers for the fabrication of potentiometric membrane electrodes for the detection of cations have been well established, similar progress for the sensing of anions has not yet been realized. We report for this reason on a novel approach for the development of all-solid-state anion selective electrodes using lipophilic multiwalled carbon nanotubes (f-MWCNTs) as the inner ion to electron transducing layer. This material can be solvent cast, as it conveniently dissolves in tetrahydrofuran (THF), an important advantage to develop uniform films without the need for using surfactants that might deteriorate the performance of the electrode. Solid contact sensors for carbonate, nitrate, nitrite, and dihydrogen phosphate are fabricated and characterized, and all exhibit comparable analytical characteristics to the inner liquid electrodes. For example, the carbonate sensor exhibits a Nernstian slope of 27.2 ± 0.8 mV·dec(-1), a LOD = 2.3 μM, a response time of 1 s, a linear range of four logarithmic units, and a medium-term stability of 0.04 mV·h(-1) is obtained in a pH 8.6 buffered solution. Water layer test, reversibility, and selectivity for chloride, nitrate, and hydroxide are also reported. The excellent properties of f-MWCNTs as a transducer are contrasted to the deficient performance of poly(3-octyl-thiophene) (POT) for carbonate detection. This is evidenced both with a significant drift in the potentiometric measures as well as a pronounced sensitivity to light (either sunlight or artificial light). This latter aspect may compromise its potential for environmental in situ measurements (night/day cycles). The concentration of carbonate is determined in a river sample (Arve river, Geneva) and compared to a reference method (automatic titrator with potentiometric pH detection). The results suggest that nanostructured materials such as f-MWCNTs are an attractive platform as a general ion-to-electron transducer for anion-selective electrodes.
虽然已经建立了用于检测阳离子的电位膜电极制造的离子到电子转导层，但类似的用于检测阴离子的进展尚未实现。因此，我们报告了一种使用亲脂性多壁碳纳米管（f-MWCNT）作为内部离子到电子转导层来开发全固态阴离子选择性电极的新方法。由于它方便地溶解在四氢呋喃（THF）中，因此可以进行溶剂铸造，这是开发均匀膜的重要优势，而无需使用可能会恶化电极性能的表面活性剂。制备并表征了用于碳酸盐、硝酸盐、亚硝酸盐和磷酸二氢盐的固态接触传感器，它们都表现出与内部液体电极相当的分析特性。例如，碳酸盐传感器具有 27.2 ± 0.8 mV·dec（-1）的 Nernst 斜率、LOD = 2.3 μM、响应时间为 1 s、四个对数单位的线性范围和 0.04 mV·h（-1）的中期稳定性在 pH 8.6 缓冲溶液中获得。还报告了水层测试、可逆性和对氯离子、硝酸盐和氢氧化物的选择性。f-MWCNT 作为传感器的优异性能与聚（3-辛基噻吩）（POT）对碳酸盐检测的性能不足形成对比。这在电位测量中明显的漂移以及对光（无论是阳光还是人工光）的明显敏感性中都得到了证明。后一方面可能会影响其在环境原位测量（昼夜循环）中的潜在应用。在河流水样（日内瓦的阿尔沃河）中测定了碳酸盐的浓度，并与参考方法（带电位 pH 检测的自动滴定仪）进行了比较。结果表明，纳米结构材料如 f-MWCNT 是作为阴离子选择性电极的通用离子到电子换能器的有吸引力的平台。
