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.