Photoswitchable Sn‐Cyt c Solid‐State Devices

Abstract

Electron transfer across proteins plays an important role in many biological processes, including those relevant for the conversion of solar photons to chemical energy. Previous studies demonstrated the generation of photocurrents upon light irradiation in a number of photoactive proteins, such as photosystem I or bacteriorhodopsin. Here, it is shown that Sn-cytochrome c layers act as reversible and efficient photoelectrochemical switches upon integration into large-area solid-state junctions. Photocurrents are observed both in the Soret band (λ = 405 nm) and in the Q band (λ = 535 nm), with current on/off ratios reaching values of up to 25. The underlying modulation in charge-transfer rate is attributed to a hole-transport channel created by the photoexcitation of the Sn-porphyrin.

Protein bioelectronics: a review of what we do and do not know

“…156 Electron transfer of immobilized cytochrome c has been accomplished via various small organic linker molecules, especially those containing thiol groups. [252][253][254][255][256][257][258] Chemically functionalized long-chain molecules, such as silanes or thiols, can spontaneously assemble on metal, glass, and carbon surfaces to form stable covalent bonds between their terminal functional group and the activated metal, metal oxide, or silicate.…”

“…Common top contacts are Hg or In-Ga eutectic (E-GaIn) electrodes. 258,331,332 The former has the advantage of being semi-noble, and with a surface that will thus be much better defined and cleaner than those of most other contacts, with the possible exception of evaporated Pb (see below). Its main disadvantage (in addition to its toxicity) is its relatively high vapor pressure, which allows for ready amalgamation with Au, unless an extra molecular layer is adsorbed on it…”

“…While no mechanistic studies were done, it was suggested that intramolecular excitations, rather than photo-induced conformational changes, opened new transport channels,. 258 Conductance switching in the photoswitchable protein dronpa (similar to GFP, green fluorescent protein) self-assembled onto gold substrates (111), was measured using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) methods before and after the protein was reversibly switched to a non-fluorescent dark state and to the fluorescent bright state in a cyclic fashion using 488 and 405 nm light ( Figure 37). 479 ETp studies on photoreceptor proteins containing a flavin chromophore have shown that chromophore-protein interactions, and the electronic environment (which mostly originates from protein residues) around the chromophore, plays an important in lightinduced transport enhancements.…”

A dithiocarbamate anchoring group as a flexible platform for interface engineering

“…As substrates, atomically flat template stripped gold (TSG) was employed and prepared according to the reported procedures. 37,38 The Au films exhibited a root mean square (RMS) roughness of 0.3 nm, exposing preferably (111) oriented surfaces. The organic monolayers were prepared under nitrogen by immersing the freshly stripped TSG substrates into DTC solutions for B20 h at room temperature.…”

A robust bioderived wavelength-specific photosensor based on BLUF proteins

“…Photosensitive proteins possess a wide variety of light-induced biochemical or biophysical characteristics, such as strong and highly specific optical response [1][2][3][4]. We witnessed a history of biomolecule-based photoelectronic device from the 1980s when bacteriorhodopsin was used to produce photoswitchable capacitors and memories [5,6] to recent booming field of photodetectors containing complex photosynthesis systems [7,8].…”