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Carotenoids as chemisorbed layers
at gold electrodes

Presented at the 36th Heyrovský Discussion, 2003

In cooperation with Bente-Jeanette Foss, Ana Ion, Vassilia Partali and  Richard Sliwka

Details: Bente-Jeanette Foss, Ana Ion, Vassilia Partali, H.-R.Sliwka, and F. G. Banica, ”Electrochemical and EQCM investigation of a selenium derivatized carotenoid in the self-assembled state at a gold electrode”, J. Electroanal. Chem., 593 (2006) 15-28.  Full paper ; Bente Jeanette Foss, Ana Ion, Vassilia Partali, H -R Sliwka and F. G. Banica,  "1-(7-Selenaoctanoyl)-glycerol as an Anchor for Self-Assembly of Biological Compounds at the Gold Surface",  Collect. Czech. Chem. Commun.,69 ( 2004) 1971-1996. Abstract

Background

Selenium-derivatizes carotenoids were adsorbed to the gold electrode surface via the Se function.The  electrochemical behavior of the surface layer was  thereafter investigated in an aqueous solution.


Compounds:

Se-anchored carotenoid derivatives
 
 
 
 


 
 
 
 
 


Caro-Glyc-Se

Anodic reactions

Electrolyte: 0.01 M HClO4
 
 

Peak A: Carotenoid anodic reaction

Peak B: Anodic desorption + Au oxidation

Peak C: AuO reduction

Curve 1: Plain gold
Curves 2- 6: Succesive scans at the modified electrode

CARO-Glyc-Se: Effect of the modification time

Modifier: 4 mM in acetonitrile. CV runs in 0.01 M HClO4

Curves 1 and 2: Charge (Q) for:

1. Anodic reaction of the carotenoid fragment (peak A)
2. Anodic desorption (peak B, corrected for Au oxidation)

Curve 3: AC current at +0.10 V (250 Hz, 10 mV rms)

CARO-Glyc-Se: Anodic reaction of the CARO fragment

Electrolyte: 0.01 M HClO4

A: Carotenoid anodic reaction

B: Anodic desorption + Au oxidation

C: AuO reduction

1 - 4: Succesive scans

CARO-Glyc-Se

Effect of the anodic reaction (peak A)

on the anodic desorption process (peak B)

Electrolyte: 0.01 M HClO4


 
 

Conclusion: Peak A reaction has no effect on the anodic desorption process


 

CARO-Glyc-Se

FRA for (1) a freshly modified electrode and

(3) after performing the anodic reaction (curve 2, peak A)

Fe(CN)63-/4- (5 mM each) in 1 M KNO3

 
 

Conclusion:q > 0.995 and increses after performing peak A reaction
 
 

CARO-Glyc-Se: Cathodic reactions

0.5 M KOH; scan rate 100 mV/s


 
 
 

CARO-Glyc-Se: Cathodic reactions

A test for the occurrence of the cathodic desorption

Q1  = Charge for anodic desorption; Q2  = Charge for gold oxide reduction


 
Sequence 
Q1, mC
Q2, mC
Q1/Q2
1. CV scan in the anodic region
53.74
45.56
1.17
2.(i) CV scan in the cathodic region, followed by (ii) a CV scan as in (1)
67.64
52.38
1.29
3. (i) Anodic oxidation of the carotenoid fragment (peak A), followed by (ii) a CV scan in the cathodic range and (iii) a CV scan as in (1)
53.44
48.56
1.10

 

Conclusion: no cathodic desorption occurs