The Interplay of Conjugation and Metal Coordination in Tuning the Electron Transfer Abilities of NTA-Graphene Based Interfaces.

Magdalena Kaźmierczak,Silvio Osella,Bartosz Trzaskowski

doi:10.3390/ijms23010543

Magdalena Kaźmierczak, Silvio Osella + Show 1 more

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https://doi.org/10.3390/ijms23010543

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Abstract

An artificial leaf is a concept that not only replicates the processes taking place during natural photosynthesis but also provides a source of clean, renewable energy. One important part of such a device are molecules that stabilize the connection between the bioactive side and the electrode, as well as tune the electron transfer between them. In particular, nitrilotriacetic acid (NTA) derivatives used to form a self-assembly monolayer chemisorbed on a graphene monolayer can be seen as a prototypical interface that can be tuned to optimize the electron transfer. In the following work, interfaces with modifications of the metal nature, backbone saturation, and surface coverage density are presented by means of theoretical calculations. Effects of the type of the metal and the surface coverage density on the electronic properties are found to be key to tuning the electron transfer, while only a minor influence of backbone saturation is present. For all of the studied interfaces, the charge transfer flow goes from graphene to the SAM. We suggest that, in light of the strength of electron transfer, Co2+ should be considered as the preferred metal center for efficient charge transfer.

Highlights

The inevitable depletion of fossil fuels is a fact, and becoming energy independent from them is an increasingly pressing problem
Throughout the study, we use the (M-XDB)n notation to define the SLG-self-assembled monolayer (SAM) interface, where M is Ni2+, Co2+, Cu2+ or PNTA, X is the number of double bonds, and n is the number of SAM molecules in the supercell
We investigate the effect of surface density on the WF and direct electron transfer (DET) abilities of the interfaces by increasing the number of SAM molecules in one supercell

Summary

Introduction

The inevitable depletion of fossil fuels is a fact, and becoming energy independent from them is an increasingly pressing problem. The processes governing natural photosynthesis are known, their reproduction on a laboratory scale is very complex, since it requires building up key components of the process without the lipid membrane present in the natural process, in a non-physiological environment [1] Despite these difficulties, biodevices based on artificial photosynthesis have been produced with encouraging results for energy conversion and water splitting processes [2,3,4,5]. One of the main challenges of these interfaces is the formation of sufficiently strong connections between the electrode and the light harvesting protein which will ensure efficient charge transfer between the two parts of the device, without losing the protein activity These connections can be created, for example, by incorporating small, organic molecules that serve as a linker between the peptide and the electrode surface [6,7]. Graphene is a flat and defect-free 2D material consisting of a single layer of carbon atoms arranged in a honeycomb structure, which as an electrode material has outstanding properties, including transparency, extraordinary mechanical strength, flexibility, exceptional electrical conductivity, and the ability to adsorb molecules on its surface [8,9,10,11,12,13]

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