X-ray photoelectron spectroscopy of metal, metal oxide, and carbon electrode surfaces chemically modified with ferrocene and ferricenium

Umaña, M.; Rolison, Debra R.; Nowak, Robert J.; Daum, P. H.; Murray, Royce W.

doi:10.1016/0039-6028(80)90623-8

Cited by 44 publications

(31 citation statements)

References 34 publications

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“…The position of the doublet is in excellent agreement with previously reported values for adsorbed ferrocene 29 and is consistent with the presence of Fc in its reduced state given that the XPS Fe 2p 3/2 signal of the ferricenium cation is expected at 710.6 eV. 30 The S 2p XP spectra of all SAMs show a broad signal with a high binding energy shoulder that can be fitted with two sets of doublets each corresponding to the S 2p 3/2 and the S 2p 1/2 components with a spin orbit coupling of 1.2 eV. The low binding energy contribution is centered at 162 eV and corresponds to thiolate bound to the Au surface and it confirms the expected covalent bond formation between the organic thiol and the Au substrate.…”

Section: B Xps Measurementssupporting

confidence: 91%

Molecular and electronic structure of electroactive self-assembled monolayers

Leo

Llave

Scherlis

et al. 2013

The Journal of Chemical Physics

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Self-assembled monolayers (SAMs) containing electroactive functional groups are excellent model systems for the formation of electronic devices by self-assembly. In particular ferrocene-terminated alkanethiol SAMs have been extensively studied in the past. However, there are still open questions related with their electronic structure including the influence of the ferrocene group in the SAMinduced work function changes of the underlying metal. We have thus carried out a thorough experimental and theoretical investigation in order to determine the molecular and electronic structure of ferrocene-terminated alkanethiol SAMs on Au surfaces. In agreement with previous studies we found that the Fc-containing alkanethiol molecules adsorb forming a thiolate bond with the Au surface with a molecular geometry 30• tilted with respect to the surface normal. Measured surface coverages indicate the formation of a compact monolayer. We found for the first time that the ferrocene group has little influence on the observed work function decrease which is largely determined by the alkanethiol. Furthermore, the ferrocene moiety lies 14 Å above the metal surface covalently bonded to the alkanethiol SAM and its HOMO is located at −1.6 eV below the Fermi level. Our results provide new valuable insight into the molecular and electronic structure of electroactive SAMs which are of fundamental importance in the field of molecular electronics.

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Section: B Xps Measurementssupporting

confidence: 91%

Molecular and electronic structure of electroactive self-assembled monolayers

Leo

Llave

Scherlis

et al. 2013

The Journal of Chemical Physics

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“…The peak shape and position for the iron 2 p doublet at 708.1 and 720.8 eV are consistent with previously reported ferrocene XPS data. 47 Significantly, only trace amounts of copper, palladium, and iodine were observed on the modified surfaces by high-resolution XPS (Fig 3b–d). In all cases, these elements were detected at significantly lower levels than the signal for iron (Table 1), which strongly supports a successful on-surface cross-coupling reaction.…”

Section: Resultsmentioning

confidence: 94%

On-surface cross-coupling methods for the construction of modified electrode assemblies with tailored morphologies

et al. 2013

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Controlling the molecular topology of electrode–catalyst interfaces is a critical factor in engineering devices with specific electron transport kinetics and catalytic efficiencies. As such, the development of rational methods for the modular construction of tailorable electrode surfaces with robust molecular wires (MWs) exhibiting well-defined molecular topologies, conductivities and morphologies is critical to the evolution and implementation of electrochemical arrays for sensing and catalysis. In response to this need, we have established modular on-surface Sonogashira and Glaser cross-coupling processes to synthetically install arrays of ferrocene-capped MWs onto electrochemically functionalized surfaces. These methods are of comparable convenience and efficiency to more commonly employed Huisgen methods. Furthermore, unlike the Huisgen reaction, this new surface functionalization chemistry generates modified electrodes that do not contain unwanted ancillary metal binding sites, while allowing the bridge between the ferrocenyl moiety and electrode surface to be synthetically tailored. Electrochemical and surface analytical characterization of these platforms demonstrate that the linker topology and connectivity influences the ferrocene redox potential and the kinetics of charge transport at the interface.

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“…It was suggested that the electrode area equivalent to the footprint of the protein molecule should include at least ten carboxylic acid residues to achieve an efficient coupling of the protein. [24b] The average distance, about 5 , between surface carboxylic groups was determined [54] by labeling experiments and X-ray analysis. The deposition of albumin on the electrode surface as a submonolayer resulted in an increase in the amount of the peroxidase linked to it as a secondary monolayer.…”

Section: Willner and E Katzmentioning

confidence: 99%

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications

Willner

Katz

2000

Angew. Chem. Int. Ed.

977

598

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Integration of redox enzymes with an electrode support and formation of an electrical contact between the biocatalysts and the electrode is the fundamental subject of bioelectronics and optobioelectronics. This review addresses the recent advances and the scientific progress in electrically contacted, layered enzyme electrodes, and discusses the future applications of the systems in various bioelectronic devices, for example, amperometric biosensors, sensoric arrays, logic gates, and optical memories. This review presents the methods for the immobilization of redox enzymes on electrodes and discusses the covalent linkage of proteins, the use of supramolecular affinity complexes, and the reconstitution of apo-redox enzymes for the nanoengineering of electrodes with protein monolayers of electrodes with protein monolayers and multilayers. Electrical contact in the layered enzyme electrode is achieved by the application of diffusional electron mediators, such as ferrocene derivatives, ferricyanide, quinones, and bipyridinium salts. Covalent tethering of electron relay units to layered enzyme electrodes, the cross-linking of affinity complexes formed between redox proteins and electrodes functionalized with relay-cofactor units, or surface reconstitution of apo-enzymes on relay-cofactor-functionalized electrodes yield bioelectrocatalytic electrodes. The application of the functionalized electrodes as biosensor devices is addressed and further application of electrically "wired" enzymes as catalytic interfaces in biofuel cells is discussed. The organization of sensor arrays, self-calibrated biosensors, or gated bioelectronic devices requires the microstructuring of biomaterials on solid supports in the form of ordered micro-patterns. For example, light-sensitive layers composed of azides, benzophenone, or diazine derivatives associated with solid supports can be irradiated through masks to enable the patterned covalent linkage of biomaterials to surfaces. Alternatively, patterning of biomaterials can be accomplished by noncovalent interactions (such as in affinity complexes between avidin and a photolabeled biotin, or between an antibody and a photoisomerizable antigen layer) to provide a means of organizing protein microstructures on surfaces. The organization of patterned hydrophilic/hydrophobic domains on surfaces, by using photolithography, stamping, or micromachining methods, allows the selective patterning of surfaces by hydrophobic, noncovalent interactions. Photoactivated layered enzyme electrodes act as light-switchable optobioelectronic systems for the amperometric transduction of recorded photonic information. These systems can act as optical memories, biomolecular amplifiers, or logic gates. The photoswitchable enzyme electrodes are generated by the tethering of photoisomerizable groups to the protein, the reconstitution of apo-enzymes with semisynthetic photoisomerizable cofactor units, or the coupling of photoisomerizable electron relay units.

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X-ray photoelectron spectroscopy of metal, metal oxide, and carbon electrode surfaces chemically modified with ferrocene and ferricenium

Cited by 44 publications

References 34 publications

Molecular and electronic structure of electroactive self-assembled monolayers

Molecular and electronic structure of electroactive self-assembled monolayers

On-surface cross-coupling methods for the construction of modified electrode assemblies with tailored morphologies

Integration of Layered Redox Proteins and Conductive Supports for Bioelectronic Applications

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