Photoisomerization of electroactive polyimide/multiwalled carbon nanotube composites on the effect of electrochemical sensing for ascorbic acid

We present the first investigation of photoisomerization of the azo‐based electroactive polyimide (PI)/amino‐functionalized multiwalled carbon nanotube (MWCNT) composite electrode on the effect of electrochemical sensing for ascorbic acid (AA). First, MWCNTs were grafted with 4‐aminobenzoic acid in a medium of polyphosphoric acid/phosphorous pentoxide to obtain MWCNTs functionalized with 4‐aminobenzoyl groups (AF‐MWCNTs). Subsequently, photoactive and electroactive PI/AF‐MWCNT composites (PEPACCs) were prepared by introducing pendant conjugated oligoaniline (amino‐capped aniline trimer) in the main chain and azobenzene chromophores in the side chain, in the presence of AF‐MWCNTs. Photoactive and electroactive PI (PEPI) and PEPACCs were characterized by ¹H NMR spectra, UV?visible absorption spectra, cyclic voltammetry (CV) and transmission electron microscopy. The CV study shows that the PEPACCs have higher electroactivity than PEPI. The redox and reversible photoisomerization (i.e. cis ? trans) behavior of PEPACCs was analyzed by in situ monitoring through systematic studies of CV and UV?visible spectroscopy. The light of the UV lamp was 365 nm. It should be noted that the sensor constructed from a trans‐PEPACC‐modified carbon‐paste electrode (CPE) demonstrated a higher electrocatalytic activity by 2.75‐fold and 1.12‐fold towards the oxidation of AA compared with those constructed using a PEPI‐ and cis‐PEPACC‐modified CPE, respectively. The detection limit of the trans‐PEPACC‐modified electrode was 1.73‐fold and 1.70‐fold lower than that of PEPI‐ and cis‐PEPACC‐modified CPE. Moreover, the differential pulse voltammetry data showed that the trans‐PEPACC‐modified electrode had high electrochemical sensing ability for the determination of AA, dopamine and uric acid. © 2014 Society of Chemical Industry