Visible LED light photoelectrochemical sensor for detection of L-Dopa based on oxygen reduction on TiO2 sensitized with iron phthalocyanine

•A novel photoelectrochemical sensor based on TiO2 nanoparticles sensitized by iron phthalocyanine was developed.•The photoelectrochemical sensor exhibited enhanced photoelectrochemical activity under visible LED light.•Photoelectrochemical sensor was firstly developed for L-Dopa determination.•This study opened up a new type of photoelectrochemical assay for L-Dopa photoelectrochemical sensing.

The present work describes the development of a new strategy to photoelectrochemical detection of L-Dopa at low potential based on oxygen reduction on TiO2 sensitized with iron phthalocyanine (FePc/TiO2). The FePc/TiO2 composite shows a photocurrent 10-fold higher than that of pure TiO2 nanoparticles and it was 4-fold higher than that of FePc exploiting visible light. The band gaps of pure TiO2 nanoparticles, FePc and FePc/TiO2, calculated according to the Kubelka–Munk equation, were 3.22 eV, 3.11 eV and 2.82 eV, respectively. The FePc/TiO2 composite showed a low charge transfer resistance in comparison to the photoelectrode modified with FePc or TiO2. Under optimized conditions, the photoelectrochemical sensor shows a linear response range from 20 up to 190 μmol L− 1 with a sensitivity of 31.8 μA L mmol− 1 and limit of detection of 1.5 μmol L− 1 for the detection of L-Dopa.