Exploring Step-by-Step Assembly of Nanoparticle:Cytochrome Biohybrid Photoanodes.

Ee Taek Hwang,Colin W J Lockwood,Joseph Beton,Erwin Reisner,Katherine L Orchard,Julea N Butt,Tadafumi Adschiri,Daisuke Hojo,Lars J C Jeuken

doi:10.1002/celc.201700030

Abstract

Coupling light‐harvesting semiconducting nanoparticles (NPs) with redox enzymes has been shown to create artificial photosynthetic systems that hold promise for the synthesis of solar fuels. High quantum yields require efficient electron transfer from the nanoparticle to the redox protein, a property that can be difficult to control. Here, we have compared binding and electron transfer between dye‐sensitized TiO2 nanocrystals or CdS quantum dots and two decaheme cytochromes on photoanodes. The effect of NP surface chemistry was assessed by preparing NPs capped with amine or carboxylic acid functionalities. For the TiO2 nanocrystals, binding to the cytochromes was optimal when capped with a carboxylic acid ligand, whereas for the CdS QDs, better adhesion was observed for amine capped ligand shells. When using TiO2 nanocrystals, dye‐sensitized with a phosphonated bipyridine Ru(II) dye, photocurrents are observed that are dependent on the redox state of the decaheme, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the decaheme conduit. In contrast, when CdS NPs are used, photocurrents are not dependent on the redox state of the decaheme, consistent with a model in which electron transfer from CdS to the photoanode bypasses the decaheme protein. These results illustrate that although the organic shell of NPs nanoparticles crucially affects coupling with proteinaceous material, the coupling can be difficult to predict or engineer.

Highlights

The histogram was prepared from the measurements of 300 nanocrystals randomly taken from the TEM images
The size of the TiO2-NH3+ nanocrystals was evaluated to be 5.8 ± 1.0 nm. This relatively large size distribution was due to the shape of the nanocrystals, which deviate from a perfect spherical shape; the apparent size distribution is increased because two-dimensional projection image is taken from TEM
The isoelectric point is determined at pH 5.1, coinciding with aggregation of the nanoparticles as suggested by the increase in hydrodynamic radius

Summary

Introduction

The histogram was prepared from the measurements of 300 nanocrystals randomly taken from the TEM images. (Middle) FT-IR spectra of RuP, TiO2-NH3+ (= TiO2DHA) and RuP-TiO2-NH3+, as indicated. The peak marked with “*” correspond to the phosphonate groups of RuP.

Results

Conclusion