Effect of MCl2 (M=Hg, Zn, Cu) subphase on photoinduced electron transfer in a pyrazinium styryl dye Langmuir–Blodgett film

Abstract

An amphiphilic heteroaromatic styryl dye, 2-(4-dihexadecylaminostyryl)-1,5-dimethylpyrazinium iodide (I) was synthesized. Its Langmuir–Blodgett films fabricated from different subphases, namely pure water (Ia), 10⁻⁵ M CuCl₂ (Ib), 10⁻⁵ M ZnCl₂ (Ic) and 10⁻⁵ M HgCl₂ (Id), were characterized by UV-Vis spectra and XPS measurements. The photoelectrochemistry of these film-modified conducting transparent indium–tin oxide (ITO) electrodes was investigated on a traditional three-electrode cell. The experimental data indicated that the films fabricated from different subphases have distinctive photoelectric responses. Under ambient conditions (0.5 M KCl), the quantum yields of photoelectric conversion were 0.03, 0.05, 0.06, and 0.1% for films Ia, Ib, Ic and Id, respectively. The effects of factors such as bias voltage, methylviologen (MV²⁺), and hydroquinone (H₂Q) on the photocurrent generation were also investigated. Based on the experimental data, a possible mechanism of photoinduced electron transfer in this system is proposed.