Spreading Chlorophyll Phospholipid Bilayer on Mn₃O₄/TiO₂ Semiconductor Substrate to Mimic Thylakoid Photosystem II...

There is a growing interest in the design and construction of artificial oxygen evolution center (OEC) materials for solar energy utilization and conversion. Inspired by the natural structure of thylakoid photosystem II (PS II) membrane, we present herein a hybrid photocatalytic semiconductor substrate Mn₃O₄/TiO₂ supported chlorophyll a-phospholipid bilayer (CPB) for light harvesting and oxygen releasing. Our design spreads a lipid bilayer containing light-harvesting pigments onto the surface of a semiconductor substrate via the emerging solvent-assisted lipid bilayer (SALB) method. The Clark oxygen electrode measured the photoelectron transfer efficiency of Mn₃O₄/TiO₂@CPB. Its excellent light-harvesting and oxygen production performance was greatly accelerated because Mn₃O₄/TiO₂ exported high-energy electrons in excited states and suppressed the recombination of photogenerated electrons and holes of chlorophyll, accelerating the photoelectron transfer efficiency of chlorophyll in the phospholipid bilayer. Moreover, the effect of chlorophyll content, composite semiconductor matrix, and lateral liquidity of phospholipid bilayer on the photoelectron transfer performance was systematically studied. Several characterization methods were used in combination, including differential scanning calorimeter (DSC) analysis, 1,6-diphenyl-1,3,5-hexanotriene (DPH) fluorescence anisotropy spectra, and fluorescence quenching technique. It was observed that the lateral liquidity of the phospholipid bilayer is distinctly affected by the amount of chlorophyll and temperature, and the membrane fluidity reaches its maximum when n _Chla:n _Lecithin is 1:20 at 30 °C, and low and high temperatures actually cause a decrease in the photoactivity of the material. The combination of Mn₃O₄/TiO₂ and chlorophyll a-phospholipid bilayer (CPB) not only broadens the light absorption region and prolongs their lifetime but also effectively reduces the transmission barriers of photogenerated electrons by constructing a tight interface contact.