title: Photosensitized H2Production Using a Zinc Porphyrin-Substituted Protein, Platinum Nanoparticles, and Ascorbate with No Electron Relay: Participation of Good's Buffers.
abstract: Development of efficient light-driven splitting of water, 2H2O → 2H2+ O2, often attempts to optimize photosensitization of the reductive and oxidative half-reactions individually. Numerous homogeneous and heterogeneous systems have been developed for photochemical stimulation of the reductive half reaction, 2H++ 2e-→ H2. These systems generally consist of various combinations of a H+reduction catalyst, a photosensitizer (PS), and a "sacrificial" electron donor. Zinc(II)-porphyrins (ZnPs) have frequently been used as PSs for H2generation, but they are subject to various self-quenching processes in aqueous solutions. Colloidal platinum in nanoparticle form (Pt NP) is a classical H+reduction catalyst using ZnP photosensitizers, but efficient photosensitized H2generation requires an electron relay molecule between ZnP and Pt NP. The present report describes an aqueous system for visible (white) light-sensitized generation of H2using a protein-embedded Zn(II)-protoporphyrin IX as PS and Pt NP as H+reduction catalyst without an added electron relay. This system operated efficiently in piperazino- and morpholino-alkylsulfonic acid (Good's buffers), which served as sacrificial electron donors. The system also required ascorbate at relatively modest concentrations, which stabilized the Zn(II)-protoporphyrin IX against photodegradation. In the absence of an electron relay molecule, the photosensitized H2generation must involve formation of at least a transient complex between a protein-embedded Zn(II)-protoporphyrin IX species and Pt NP.
authors.affiliation: Department of Chemistry, University of Texas at San Antonio , San Antonio, Texas 78249, United States.
authors.forename: Emily R
authors.initials: ER
authors.lastname: Clark
authors.affiliation: Department of Chemistry, University of Texas at San Antonio , San Antonio, Texas 78249, United States.
authors.forename: Donald M
authors.identifier: http://orcid.org/0000-0003-1179-1875
authors.initials: DM
authors.lastname: Kurtz
mesh_terms: D006859:Hydrogen / Q000737:chemistry*; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry*; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D017319:Photosensitizing Agents / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*
chemical_list: D008665:Metalloporphyrins; D017319:Photosensitizing Agents; C017802:zinc hematoporphyrin; D010984:Platinum; D006859:Hydrogen