Photosensitized H 2 Evolution and NADPH Formation by Photosensitizer/Carbon Nitride Hybrid Nanoparticles

• Published in: Nano letters 2019-12, Vol.19 (12), p.9121-9130
• Main Authors: Chen, Wei-Hai, Zhou, Zhixin, Luo, Guo-Feng, Neumann, Ehud, Marjault, Henri-Baptiste, Stone, David, Nechushtai, Rachel, Willner, Itamar
• Format: Article
• Language: English
• ISSN: 1530-6984; 1530-6992
• DOI: 10.1021/acs.nanolett.9b04375

The broadband C N semiconductor absorbs in the UV region, λ = 330-380 nm, a feature limiting its application for light-to-energy conversion. The unique surface adsorption properties of C N allow, however, the binding of a photosensitizer, operating in the visible-solar spectrum to the surface of C N . Coupling of the energy levels of the photosensitizer with the energy levels of C N allows effective photoinduced electron-transfer quenching and subsequent charge separation in the hybrid structures. Two methods to adsorb a photosensitizer on the C N nanoparticles are described. One is exemplified by the adsorption of Zn(II)-protoporphyrin IX on C N using π-π interactions. The second method utilizes the specific binding interactions of single-stranded nucleic acids on C N and involves the binding of a Ru(II)-tris-bipyridine-modified nucleic acid on the C N nanoparticles. Effective electron-transfer quenching of the photoexcited photosensitizers by C N proceeds in the two hybrid systems. The two hybrid photosystems induce the effective photosensitized reduction of , '-dimethyl-4,4'-bipyridinium, MV , to MV , in the presence of Na EDTA as a sacrificial electron donor. The generation of MV is ca. 5-fold higher as compared to the formation of MV in the presence of the photosensitizer alone (in the absence of C N ). The effective generation of MV in the photosystems is attributed to the efficient quenching of the photosensitizers, followed by effective charge separation of the electrons in the conduction band of C N and the holes in the oxidized photosensitizer. The subsequent transfer of the conduction-band electrons to MV and the oxidation of Na EDTA by the oxidized photosensitizers lead to the effective formation of MV . The photogenerated MV by the two hybrid photosystems is used to catalyze H evolution in the presence of Pt nanoparticle catalysts and to mediate the reduction of NADP to NADPH, in the presence of ferredoxin-NADP reductase, FNR. The ability to couple the photogenerated NADPH to drive NADP -dependent biocatalytic transformations is demonstrated.