Photoinduced electron transfer in GFP/viologen/TCNQ structured hetero-LB film

The photoinduced electron transfer rate in hetero-Langmuir–Blodgett (LB) films, composed of electron sensitizing protein and electron accepting organics, was investigated. The hetero-LB film was fabricated by sequentially depositing green fluorescence protein (GFP), viologen, and TCNQ, which functioned as an electron sensitizer, a relay, and an acceptor, respectively. To verify the hetero-LB film formation, surface morphologies of the GFP film and viologen/TCNQ LB film were observed by atomic force microscopy (AFM). The fast charge separation of the molecular interface was investigated by analyzing the time-resolved fluorescence decays of GFP homo-, GFP/viologen hetero- and GFP/viologen/TCNQ hetero-LB film using a time-correlated single photon counting (TCSPC) method. In GFP/viologen hetero-films, the fluorescence decay of excited GFP was faster than that in the GFP homo-film. Based on the decay of fluorescence the charge separation rates of excited GFP were calculated. The fluorescence lifetime and charge separation rate of the GFP/viologen/TCNQ hetero-LB film increased slightly compared to that of the GFP/viologen hetero-LB film as a result of the addition of the TCNQ layer, electron acceptor. On the basis of its molecular interface charge separation behavior, the proposed molecular array can be used as a component of the molecular photodiode.