A highly sensitive perovskite oxide sensor for detection of p-phenylenediamine in hair dyes

Effective regulation of p-phenylenediamine (PPD), a widely used precursor of hair dye that is harmful to human health in large concentration, relies upon an accurate yet simple detection of PPD. In this context, amperometric electrode sensor based on perovskite oxide becomes attractive given its portability, low cost, high sensitivity, and rapid processing time. This work reports the systematic characterization of a series of Sr-doped PrCoO_3-δ perovskite oxides with composition of Pr_1-xSr_xCoO_3-δ(x = 0, 0.2, 0.4, 0.6, 0.8, and 1) for PPD detection in an alkaline solution. PSC82 deposited onto glassy carbon electrode (PSC82/GCE) generates the highest redox currents which correlates with the highest hydrogen peroxide intermediates (HO₂^-) yield and the σ*-orbital (e_g) filling of Co that is closest to unity for PSC82. PSC82/GCE provides the highest sensitivities of 655 and 308 μA mM^-1 cm^-2 in PPD concentration range of 0.5-2,900 and 2,900-10,400 μM, respectively, with a limit of detection of 0.17 μM. PSC82/GCE additionally demonstrates high selectivity to PPD and long term stability during 50 consecutive cyclic voltammetry scans and over 1-month storage period. The potential applicability of PSC82/GCE was also demonstrated by confirming the presence of very low concentration of PPD of below 0.5% in real hair dyes.