Zn(II)-Protoporphyrin IX-Based Photosensitizer-Imprinted Au-Nanoparticle-Modified Electrodes for Photoelectrochemical Applications

• Published in: Advanced functional materials 2015-11, Vol.25 (41), p.6470-6477
• Main Authors: Metzger, Tzuriel Simcha, Tel-Vered, Ran, Albada, Hendrik Bauke, Willner, Itamar
• Format: Article
• Language: English
• Subjects: Au nanoparticles; Binding; Charge; Electrodes; electropolymerization; Gold; molecular imprinting; Nanoparticles; Photocurrent; Photoelectric effect; porphyrin; Transport
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201502801

The electropolymerization of thioaniline‐modified Au nanoparticles (NPs) on thioaniline monolayer‐functionalized electrodes in the presence of Zn(II)‐protoporphyrin IX yields bis aniline‐crosslinked Au NPs matrices that include molecular imprinted sites for binding the Zn(II)‐protoporphyrin IX photosensitizer. The binding of the photosensitizer yields photoelectrochemically active electrodes that produce anodic photocurrents in the presence of the electron donor benzohydroquinone. The efficient photocurrents formed in the presence of the imprinted electrode are attributed to the high‐affinity binding of the photosensitizer to the imprinted sites, Ka = 3.2 × 106 m−1, and to the effective transport of the photoejected electrons to the bulk electrode via the bridged Au NPs matrix. Similarly, a N,N′‐dialkyl‐4,4′‐bipyridinium‐modified Zn(II)‐protoporphyrin IX photosensitizer‐electron acceptor dyad is imprinted in the bis aniline‐crosslinked Au NPs matrix. The photocurrent generated by the imprinted matrix is approximately twofold higher as compared to the photocurrent generated by the Zn(II)‐protoporphyrin IX‐imprinted Au NPs matrix. The efficient photocurrents generated in the presence of the bipyridinium‐modified Zn(II)‐protoporphyrin IX‐imprinted matrix are attributed to the effective primary charge separation of the electron–hole species in the dyad structure, followed by the effective transport of the photoejected electrons to the electrode via the bis aniline‐crosslinked Au NPs matrix. The structural features of Zn(II)‐protoporphyrin IX or bipyridinium‐modified Zn(II)‐protoporphyrin IX are imprinted in electropolymerized bis aniline‐crosslinked Au nanoparticle matrices associated with electrodes. The concentration of the photosensitizers at the electrodes by means of the imprinted sites leads to effective charge separation resulting in intensified photocurrents.