ISSN:
0894-3230
Keywords:
molecular optoelectronics
;
bio-optoelectronics
;
photoisomerizable monolayers
;
functionalized electrodes
;
photoactive monolayers
;
photochemical switch
;
optical switches
;
molecular electronic gates
;
cytochrome c
;
cytochrome oxidase
;
protein monolayer interactions
;
quartz crystal microbalance
;
photochromic compounds
;
redox switch
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Molecular and biomolecular optobioelectronic systems that yield the amperometric transduction of recorded optical signals are described. Phenoxynaphthacene quinone is assembled as a monolayer on an Au electrode. Photoisomerization of the monolayer between the redox-active trans-quinone state and the redox-inactive ‘ana’-quinone state provides a means to transduce electrochemically optical signals recorded by the monolayer. Coupling of the redox-active trans-quinone monolayer electrode to the secondary reduction of N,N′-dibenzyl-4,4′-bipyridinium, BV2+, provides a means to amplify the transduced current. As the redox potential of the trans-quinone monolayer is pH dependent, the electrocatalyzed monolayer-mediated reduction of BV2+ is controlled by light and the pH. The system represents an ‘AND’ gated molecular electronic assembly. A thiol nitrospiropyran monolayer was assembled on an Au electrode. The functionalized electrode acts as photo-triggered ‘command interface’ that controls the electrooxidation of dihydroxyphenylacetic acid (DPAA). The electrical properties of the monolayer are controlled by the photoisomer state of the monolayer and the pH of the medium. The monolayer in the nitromerocyanine state exists at pH 9.2 and 7.0 in zwitterionic or positively charged states, respectively. Electrooxidation of the negatively charged substrate, DPPA, is enhanced only in the presence of the protonated nitromerocyanine monolayer electrode. This permits the gated oxidation of the substrate by two complementary triggering signals, light and pH. A mixed monolayer consisting of nitrospiropyran and thiolpyridine units assembled on an Au electrode is applied as a photoisomerizable command surface for controlling the electrical contact of cytochrome c (Cyt c) with the electrode. In the nitrospiropyran-pyridine configuration electrical contact of Cyt c and the electrode is attained by the association of Cyt c to pyridine promoter sites. Photoisomerization of the monolayer to the protonated nitromerocyanine state results in the electrostatic repulsion of Cyt c from the monolayer, and the electrical contact of Cyt c with the electrode is blocked. Coupling of the electrically contacted Cyt c and nitrospiropyran-pyridine monolayer electrode configuration to the cytochrome oxidase biocatalyzed reduction of oxygen provides a means to amplify the transduced amperometric response. The photostimulated association and dissociation of Cyt c to and from the photoisomerizable monolayer were confirmed by microgravimetric, quartz crystal microbalance analyses. The system mimics the function of the native vision process. © 1998 John Wiley & Sons, Ltd.
Additional Material:
25 Ill.
Type of Medium:
Electronic Resource
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