Elucidation of the electron transfer mechanism of marker ions at SAMs with charged head groups

Degefa, Tesfaye Hailu; Schön, Peter; Bongard, Dirk; Walder, Lorenz

doi:10.1016/j.jelechem.2004.07.026

Cited by 39 publications

(62 citation statements)

References 30 publications

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“…The deprotonation of COOH-Alk-SAM begins at around pH 4, suggesting that a small amount of terminal -COOH dissociates protons and becomes anionic -COO À . 15,21) On the other hand, the protonation of NH 2 -Alk-SAM takes place at pH 4, suggesting that all the -NH 2 was protonated to become cationic -NH 3 þ . 15) In the case of OH-Alk-SAM, no protonation or deprotonation occurs at pH 4 and the surface charge of the OH-Alk-SAM is neutral.…”

Section: Discussionmentioning

confidence: 99%

“…15,21) On the other hand, the protonation of NH 2 -Alk-SAM takes place at pH 4, suggesting that all the -NH 2 was protonated to become cationic -NH 3 þ . 15) In the case of OH-Alk-SAM, no protonation or deprotonation occurs at pH 4 and the surface charge of the OH-Alk-SAM is neutral. 22) It is reported that [Ru(NH 3À ions) can act as catalytic reagents for electron transfer between the electrode and the dissolved ions, and that the electron transfer between the dissolved ions and the electrode with SAM was enhanced.…”

Section: Discussionmentioning

confidence: 99%

“…22) It is reported that [Ru(NH 3À ions) can act as catalytic reagents for electron transfer between the electrode and the dissolved ions, and that the electron transfer between the dissolved ions and the electrode with SAM was enhanced. 15) Because most of the U(VI) exists in the di-oxo-cationic form in the solution, the adsorbed U on COOH-Alk-SAM (negatively charged SAM) can act as a catalytic reagent for the electron transfer as in the case of the above ions. This might cause a higher reduction current with COOH-Alk-SAM than with OH-Alk-SAM (neutrally charged SAM) or NH 2 -Alk-SAM (positively charged SAM) (Figs.…”

Section: Discussionmentioning

confidence: 99%

“…[14][15][16][17][18] The procedure was as follows: The Au/mica electrode was annealed using a hydrogen flame and immersed for 5 min without potential control into 20 mM 4, 4 0 -dithiodipyridine aqueous solution, which was deaerated to prevent the oxidation of thiol. The electrode was thoroughly rinsed with water, and then used as a 4, 4 0 -dithiodipyridine-modified self-assembled-monolayer (4-PyS-SAM) working electrode.…”

Section: Experimental Procedures 1 Materials and Solutionsmentioning

confidence: 99%

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Sorption of U(VI) on the 4-Mercaptopyridine Self-Assembled Monolayer

Nankawa

Ozaki

Francis

et al. 2008

J. Nucl. Sci. Technol.

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The sorption of U(VI) on the 4-mercaptopyridine self-assembled monolayer (4-PyS-SAM) on Au(111) was studied by cyclic voltammetry. Cyclic voltammograms (CVs) of the 4-PyS-SAM working electrode were obtained by contact with 1 mM UO 2 (NO 3 ) 2 solution, 1 mM UO 2 (NO 3 ) 2 and 50 mM acetic acid solution, or 1 mM UO 2 (NO 3 ) 2 and 50 mM oxalic acid solution for 6 h at pH 4. The reduction current of U(VI) to U(V) was detected in the CV. The CV of the U(VI) associated 4-PyS-SAM after transport to U(VI)-free 0.1 M NaClO 4 solution showed that the reduction current was detected in the cases of UO 2 (NO 3 ) 2 and U(VI)-acetate, but not in the case of U(VI)-oxalate solution, indicating that U(VI) was adsorbed on the 4-PyS-SAM from the UO 2 (NO 3 ) 2 and U(VI)-acetate solutions, but not from U(VI)-oxalate solution. These results suggest that stability of U(VI)-4-PyS-SAM is not so high that U(VI)-4-PyS-SAM cannot be formed in the presence of 50 mM oxalate.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Experimental Procedures 1 Materials and Solutionsmentioning

confidence: 99%

See 2 more Smart Citations

Sorption of U(VI) on the 4-Mercaptopyridine Self-Assembled Monolayer

Nankawa

Ozaki

Francis

et al. 2008

J. Nucl. Sci. Technol.

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“…32 Beside the galvinoxyl coated gold electrode ͑working electrode͒, a Ag/ AgCl reference electrode ͑Meth-rom, 6.0724.140, separated by a salt bridge containing the electrolyte of the measuring compartment͒, and a platinum wire as the counter electrode were used. As supporting electrolyte we used 0.1 M Na 2 HPO 4 .…”

Section: A Methodsmentioning

confidence: 99%

Galvinoxyl monolayers on Au(111) studied by STM, EPR, and cyclic voltammetry

et al. 2006

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Galvinoxyl layers on Au͑111͒ have been studied by scanning tunnelling microscopy ͑STM͒, electron paramagnetic resonance ͑EPR͒, and cyclic voltammetry ͑CV͒. We observe two phases: configuration I having a molecular density of 1.57± 0.16ϫ 10 −10 mol/ cm 2 and a rectangular lattice ͑15 Å by 7 Å͒ observed at room temperature and down to 140 K; configuration II with a slightly smaller molecular density of 1.37± 0.14 ϫ 10 −10 mol/ cm 2 and oblique cells ͑22.5 Å by 5.4 Å͒ arranged alternatingly in stacks yielding a molecular layer with lower symmetry and comparatively large crystallographic unit cell. The latter is only observed upon cooling down to 40 K and subsequent annealing to room temperature. For both assemblies typical domain sizes in the range of 100 nm have been found. The EPR results confirm that the radical character is preserved upon adsorption and that the intermolecular distance is smaller than 11 Å. The interaction between the overlapping singly occupied spin orbitals is high, indicating no participation of the unpaired electron in the binding to the surface or laterally between neighboring radicals. The average surface concentration deduced from CV measurements is in excellent agreement with the surface coverages deduced from STM topographies. In aqueous electrolyte the adsorbate undergoes a one-electron oxidation with concomitant loss of a proton as determined from oxidation potential vs pH curves in a similar fashion as known for the free radical in solution. This indicates no dramatic change of the electronic properties of the radical upon adsorption. Structure models are proposed with molecules standing upright like "bicycles in rows."

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