A dually functional 4-aminophenylboronic acid dimer for voltammetric detection of hypochlorite, glucose and fructose

The authors report on the electrochemical process for the modification of a screen printed carbon electrode (SPCE) with an azo-functionalized dimer of 4-amino phenylboronic acid. The dimer is prepared on the surface of the SPCE through the formation of azo bond, and the presence of the dimer is confirmed by cyclic voltammetry, X-ray photoelectron spectroscopy and functional group specific sensing studies. Specifically, this unique dimer-modified electrode possesses dual functionalities (R-N=N-R' and -B(OH)(2)) which makes its suitable for selective detection of hypochlorite (i.e., free chlorine) and sugar molecules (demonstrated for glucose and fructose), respectively. The heterogeneous electron transfer rate constant is 7.89 s(-1) which indicates a fast electron transfer process at the dimer-modified SPCE. The sensor, operated at a voltage of typically 0.05 V (vs. Ag/AgCl), gives a linear response in the 1 mu M to 10 mM hypochlorite concentration range and has a sensitivity of 408.16 mu A mM(-1) cm(-2) at neutral pH values. The catalytic rate constant is 49,872 M s(-1) for free chlorine. By using hexacyanoferrate as an electrochemical probe and at a typical working voltage of 0.18 V (vs. Ag/AgCl), the sensor displays a linear response in the 1 to 500 mu M fructose and glucose concentration range, with detection limits (for S/N = 3) of 0.24 mu M for fructose and 0.36 mu M for glucose.