Fabricating carbon-nanotubes-based porous foam for superoxide electrochemical sensing through one-step hydrothermal process induced by phytic acid.

The detection of superoxide anions (O2 •- ) is widely considered as a potential way for cancer diagnosis and the development of enzyme-mimic catalysts is the main challenge in the establishment of electrochemical sensors for O2 •- sensing in real samples. Here we present a novel enzyme- and metal-free electrochemical catalyst for superoxide (O2 •- ) sensing based on the widely-used carbon nanotubes (CNT). Through a one-step hydrothermal process induced by phytic acid (PA), CNT-based porous foam (PACNTF) was successfully obtained. Characterizations demonstrated the enhanced defect and disorder degree of PACNTF after PA treatment, which leaded to the increased active sites of PACNTF for electron transfer and the adhesion of O2 •- during the electrochemical process. As a result, the PACNTF presented higher conductivity and larger current response toward O2 •- sensing when compared with CNT precursor and CNTF without PA treatment. The sensitivity of PACNTF/SPCE was calculated to be 1230 μA cm-2  mM-1 in the linear range of 0-193.6 μM (R2  = 0.965) and 373 μA cm-2  mM-1 in the linear range of 193.6-1153.6 μM (R2  = 0.995) with a limit of detection of 0.16 μM (S/N = 3). Further, the PACNTF/SPCE presented fast response toward cell-released O2 •- stimulated by Zymosan A. The above results indicated that the fabricated sensor holds potential usage in biological samples.