Electrochemical Study of Dopamine at Electrode Fabricated by Cellulose-Assisted Aqueous Dispersion of Long-Length Carbon Nanotube

• Published in: Journal of physical chemistry. C Vol. 120; no. 22; pp. 12284 - 12292
• Main Authors: Muguruma, Hitoshi, Inoue, Yuki, Inoue, Hitoshi, Ohsawa, Tatsuya
• Format: Journal Article
• Language: English
• Published: American Chemical Society 09.06.2016
• Subjects: aqueous solutions; carbon electrodes; carbon nanotubes; cellulose; dopamine; electrochemistry; electron transfer; fullerene; graphene; nanofibers; oxidation; physical chemistry; surfactants
• ISSN: 1932-7447; 1932-7455; 1932-7455
• DOI: 10.1021/acs.jpcc.6b03715

A long-length (hundred micrometers) carbon nanotube is successfully dispersed in aqueous solution with surfactant cellulose while maintaining its length. An electrochemical study of the synthetic pathway of dopamine (DA), dopamine-o-quinone (DAQ), leucodopaminechrome (LDAC), and dopaminechrome (DAC) at the electrode fabricated by the long-length carbon nanotube dispersed solution is presented. The sequence DA ⇌ DAQ ⇀ LDAC ⇌ DAC for the reaction is electron transfer-chemical reaction-electron transfer (ECE)-type, which is a chemical reaction (DAQ ⇀ LDAC, C) interposed between two electron transfer reactions (DA ⇌ DAQ and LDAC ⇌ DAC, E). The salient electrochemical signals due to both DA ⇌ DAQ and LDAC ⇌ DAC can be obtained at the long-length carbon nanotube electrode, unlike other carbon electrodes such as carbon paste, graphene, fullerene, nanofiber, and graphite. The overall reaction is dominated by step DAQ ⇀ LDAC and is sensitive to pH. With cyclic voltammetry in acidic media, the peak current due to LDAC ⇀ DAC disappeared at a higher scan rate because the reaction rate for DAQ ⇀ LDAC was so slow that DAQ was completely consumed in the electron transfer of DAQ ⇀ DA before the chemical reaction of DAQ ⇀ LDAC could go forward. In alkaline media, the peak height due to DAC ⇀ LDAC became as high as that due to DA ⇀ DAQ because the DAQ ⇀ LDAC rate became fast enough that a sufficient amount of LDAC was generated for the subsequent reaction of LDAC ⇀ DAC. Concomitantly, the reaction DAQ + LDAC ⇌ DA + DAC was generated. Quantitative and selective detection of dopamine based on the signal due to LDAC ⇀ DAC is possible just as in the conventional strategy of direct oxidation of dopamine (DA ⇀ DAQ).