Voltammetric response of [Co(phen)3]3+ and gold nanoparticles/multi-walled carbon nanotubes to two C-6 substituted purines

•[Co(phen)3]3+ has assembled on purine ring of 6-MP on MWCNTs surface.•[Co(phen)3]3+ is immobilized on Hx/MWCNTs/C electrode by p–π interactions.•S–Au bond hinders presence of characteristic redox peaks of 6-MP-[Co(phen)3]3+.•An effective approach is proposed to achieve the binding constant (8.4 × 103 M−1).

Voltammetric response of [Co(phen)3]3+ (phen = 1,10-phenanthroline) and gold nanoparticles/multi-walled carbon nanotubes (GNPs/MWCNTs) to 6-mercaptopurine (6-MP) and hypoxanthine (Hx) is comparatively investigated by means of cyclic voltammetry in combination with scanning electron microscopy. The presence of 6-MP and Hx is found to influence the electrochemical assembly of [Co(phen)3]3+ on GNPs/MWCNTs modified graphite (C) electrodes. [Co(phen)3]3+ is electrochemically assembled on the 6-MP/GNPs/C and Hx/MWCNTs/C electrodes by S–Au bond and p–π interactions, showing only a pair of well-defined redox peaks. The addition of MWCNTs to the GNPs/C electrode leads to the presence of a new pair of characteristic redox peaks via π–π stacking interactions of [Co(phen)3]3+/MWCNTs with 6-MP. On basis of the voltammetric response of [Co(phen)3]3+/MWCNTs/C electrode to 6-MP, a new approach has been proposed to achieve the binding constant of 8.4 × 103 M−1. Taken together, [Co(phen)3]3+ and GNPs/MWCNTs have shown interesting voltammetric responses, which can be used to discriminate between two C-6 substituted purine analogues.

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