EQCM study of influences of heparin and tannic acid on the precipitation of phenazinehydrine charge-transfer complex during redox switching of o-phenylenediamine in aqueous H₂SO₄

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• 作者：Meng Li ; Chunyan Deng ; Xinman Tu ; Zhijun Cao ; Qingji Xie ; ^{xieqj@hunnu.edu.cn} ; Zhengfa Fang ; Ming Ma ; Mingli Zhu ; Youyu Zhang ; Shouzhuo Yao
• 关键词：EQCM ; Cyclic voltammetric redox switching of o-phenylenediamine in aqueous H2SO4 ; Phenazinehydrine charge-transfer complex (CTC) ; Effects of coexisting tannic acid or sodium heparin on CTC precipitation
• 刊名：Journal of Electroanalytical Chemistry
• 出版年：2006
• 出版时间：1 September 2006
• 年：2006
• 卷：594
• 期：2
• 页码：133-142
• 全文大小：581 K

文摘

The electrochemical quartz crystal microbalance (EQCM) based on the piezoelectric quartz crystal impedance (PQCI) analysis was used to investigate the electrolyte effects on the precipitation of phenazinehydrine charge-transfer complex (CTC) during cyclic voltammetric redox switching of o-phenylenediamine (oPD) at Au electrodes in aqueous H₂SO₄. The response to concentration modulation for Na₂SO₄, K₂SO₄, sodium gluconate, tannic acid (TA), or sodium heparin as additives in 0.10 (or 0.30) mol L^? aqueous H₂SO₄ containing 0.050 mol L^? o-phenylenediamine was comparatively examined. In vivid contrast to and gluconate, the increase in the concentration of large-sized TA or sodium heparin strongly weakened the CTC precipitation, giving detectable responses down to the ¦Ìmol L^? level. Similar effects were also found in acidic phenazine systems. The anionic effect on the CTC precipitation is reasonably explained via the following mechanism, namely, the protonation at nitrogen atoms of the oligomers with phenazine units from oPD oxidation, induced anionic incorporation and resulting steric hindrance in CTC-formation reactions/processes, plus the concentration decrease for oligomers with phenazine units in the presence of large-sized anions.