Showing papers by "David E. Cliffel published in 2014"

Photosystem I Protein Films at Electrode Surfaces for Solar Energy Conversion

Abstract: Over the course of a few billion years, nature has developed extraordinary nanomaterials for the efficient conversion of solar energy into chemical energy. One of these materials, photosystem I (PSI), functions as a photodiode capable of generating a charge separation with nearly perfect quantum efficiency. Because of the favorable properties and natural abundance of PSI, researchers around the world have begun to study how this protein complex can be integrated into modern solar energy conversion devices. This feature article describes some of the recent materials and methods that have led to dramatic improvements (over several orders of magnitude) in the photocurrents and photovoltages of biohybrid electrodes based on PSI, with an emphasis on the research activities in our laboratory.

Photoactive films of photosystem I on transparent reduced graphene oxide electrodes.

Abstract: Photosystem I (PSI) is a photoactive electron-transport protein found in plants that participates in the process of photosynthesis. Because of PSI’s abundance in nature and its efficiency with charge transfer and separation, there is a great interest in applying the protein in photoactive electrodes. Here, we developed a completely organic, transparent, conductive electrode using reduced graphene oxide (RGO) on which a multilayer of PSI could be deposited. The resulting photoactive electrode demonstrated current densities comparable to that of a gold electrode modified with a multilayer film of PSI and significantly higher than that of a graphene electrode modified with a monolayer film of PSI. The relatively large photocurrents produced by integrating PSI with RGO and using an opaque, organic mediator can be applied to the facile production of more economic solar energy conversion devices.

Integration of Photosystem I with Graphene Oxide for Photocurrent Enhancement

Abstract: Photosystem I is a photoactive membrane protein used in nature to photo-excite electrons with nearly unit internal quantum efficiency, sparking interest in using this biomaterial for solar energy conversion. Films of PSI deposited on p-doped silicon have previously demonstrated significant photocurrents with an electrochemical mediator; however, improvement in electron transfer is needed. Here, it is investigated how PSI can be combined with graphene oxide (GO) or reduced graphene oxide (RGO) to generate composite films capable of improved photoelectrochemical performance. It is found that both composite films outperformed the PSI film alone, and the PSI-GO composite film is found to perform the best. The enhancement is attributed to the decreased impedance and shift in the onset potential of the composite films.

Multichamber Multipotentiostat System for Cellular Microphysiometry.

Abstract: Multianalyte microphysiometry is a powerful technique for studying cellular metabolic flux in real time. Monitoring several analytes concurrently in a number of individual chambers, however, requires specific instrumentation that is not available commercially in a single, compact, benchtop form at an affordable cost. We developed a multipotentiostat system capable of performing simultaneous amperometric and potentiometric measurements in up to eight individual chambers. The modular design and custom LabVIEW™ control software provide flexibility and allow for expansion and modification to suit different experimental conditions. Superior accuracy is achieved when operating the instrument in a standalone configuration; however, measurements performed in conjunction with a previously developed multianalyte microphysiometer have shown low levels of crosstalk as well. Calibrations and experiments with primary and immortalized cell cultures demonstrate the performance of the instrument and its capabilities.