Photocurrent Generation of Reconstituted Photosystem II on a Self-Assembled Gold Film.

Photosystem II (PSII)-modified gold electrodes were prepared by the deposition of PSII reconstituted with platinum nanoparticles (PtNPs) on Au electrodes. PtNPs modified with 1-[15-(3,5,6-trimethyl-1,4-benzoquinone-2-yl)]pentadecyl disulfide ((TMQ(CH2)15S)2) were incorporated into the QB site of PSII isolated from thermophilic cyanobacterium Thermosynechococcus elongatus. The reconstitution was confirmed by QA-reoxidation measurements. PSII reconstituted with PtNPs was deposited and integrated on a Au(111) surface modified with 4,4'-biphenyldithiol. The cross section of the reconstituted PSII film on the Au electrode was investigated by SEM. Absorption spectra showed that the surface coverage of the electrode was about 18 pmol PSII cm-2. A photocurrent density of 15 nAcm-2 at E = +0.10 V (vs Ag/AgCl) was observed under 680 nm irradiation. The photoresponse showed good reversibility under alternating light and dark conditions. Clear photoresponses were not observed in the absence of PSII and molecular wire. These results supported the photocurrent originated from PSII and moved to a gold electrode by light irradiation, which also confirmed conjugation with orientation through the molecular wire.

Conjugates between photosystem I and a carbon nanotube for a photoresponse device.

Photosystem I (PS I) is a large pigment-protein complex embedded in the thylakoid membranes that performs light-driven electron transfer across the thylakoid membrane. Carbon nanotubes exhibit excellent electrical conductivities and excellent strength and stiffness. In this study, we generated PSI-carbon nanotube conjugates dispersed in a solution aimed at application in artificial photosynthesis. PS I complexes in which a carbon nanotube binding peptide was introduced into the middle of the PsaE subunit were conjugated on a single-walled carbon nanotube, orienting the electron acceptor side to the nanotube. Spectral and photoluminescence analysis showed that the PS I is bound to a single-walled carbon nanotube, which was confirmed by transmission electron microscopy. Photocurrent observation proved that the photoexcited electron originated from PSI and transferred to the carbon nanotube with light irradiation, which also confirmed its orientated conjugation. The PS I-carbon nanotube conjugate will be a useful nano-optoelectronic device for the development of artificial systems.

Fluorescent azadipyrrinato zinc(II) complex: hybridisation with a dipyrrinato ligand.

We synthesised heteroleptic azadipyrrinato-dipyrrinato hybrid zinc(II) complex 1-Zn-2, by means of the stepwise coordination method. Homoleptic bis(azadipyrrinato)zinc(II) complex 1-Zn-1 was non-fluorescent, whereas 1-Zn-2 exhibited detectable fluorescence from azadipyrrinato ligand 1.