Experimental and theoretical studies on electropolymerization of polar amino acids on platinum electrode (original) (raw)
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Electrochemical behaviour of amino acids on Pt(hkl). A voltammetric and in situ FTIR study
Journal of Electroanalytical Chemistry, 1998
The electrochemical behaviour of glycine on well-defined Pt(100) and Pt(110) electrodes has been studied in an acid medium by means of cyclic voltammetry and in situ FTIR spectroscopy. The results presented in this paper and those reported previously for the Pt(111)glycine system have shown that glycine oxidation is a surface structure-sensitive reaction. Adsorbed cyanide (band around 2100 cm − 1 ) and adsorbed nitric oxide (band at 1610 cm − 1 ) were the main poisoning species formed during the electro-oxidation of this amino acid on Pt(100). Adsorbed cyanate (2165 cm − 1 ) has been also identified as an intermediate species during such oxidation. The formation of a carbon monoxide ad-layer when the Pt(100) electrode was polarised below 0.4 V in a glycine-containing solution has been attributed to a cyanide surface reaction to produce CO ads and, probably, NH 4 + . On Pt(110), glycine electro-oxidation produces adsorbed cyanide as a unique poisoning species. The adsorbed cyanide can be removed from the surface at potentials below 0.1 V. Finally, the presence of reversibly adsorbed glycinate anions on both Pt(100) and Pt(110) surfaces has been shown. Glycinate anions are 2-fold coordinated to the electrode surface through their carboxylate groups.
Journal of Electroanalytical Chemistry, 1997
A spectroelectroehemical study of the adsorption and oxidation of glycine on a Pt(111) electrode has been carried out in 0.1 M HCIO4 solution. Two types of adsorbate were identified. On the one hand, strongly adsorbed cyanide which comes from the oxidative adsorption of the molecule. This adsorbate has been isolated and characterized. On the other hand reversibly adsorbed glycinate anions, which adsorb at potentials above 0.3 V, have been detected. As in the case of acetate anions, glycinate is two-fold coordinated to the Pt(l 11) surface through the carboxylate group. The analysis of the potential dependent band centre frequencies and integrated band intensities suggests that lateral interactions between adsorbed glycinate anions are at the origin of the small frequency shift observed with increasing potential.
Journal of the American Chemical Society, 2019
For years, polypeptide formation has fascinated the scientific world since its understanding would be one of the possible explanation for the origin of life. Anodic oxidation of aliphatic -amino acids in aqueous electrolytes can result either in their decomposition or polymerization into polypeptide. This behavior depends experimentally on both amino acid concentration and pH. The elucidation of the involved mechanisms remains a challenge due to the multitude of products which can be obtained. In this context, the electrochemical behavior of glycine and alanine on a biased platinum surface was examined at the nanoscale by quantum electrochemistry via the effective screening medium method. Several electrochemical systems with different concentration and pH have been explored. Simulations of the anodic oxidation of the amino acids have not only confirmed their electropolymerization and decomposition at high and low concentrations, respectively, but have also revealed unsuspected mechanisms at the origin of polypeptide formation. This sheds new light on electrochemistry of -amino acids, occurrence of polypeptides and more generally on organic electrochemistry.
Langmuir, 2006
The formation of a self-assembled monolayer (SAM) of 4-aminothiophenol (4-ATP) on polycrystalline platinum electrodes has been characterized by surface analysis and electrochemistry techniques. The 4-ATP monolayer was characterized by cyclic voltammetry (CV), linear sweep voltammetry, Raman spectroscopy, reflection-absorption infrared (RAIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). CV was used to study the dependence of the adsorption time and 4-ATP solution concentration on the relative degree of coverage of 4-ATP monolayers on polycrystalline Pt electrodes. The adsorption time range probed was 24-72 h. The optimal concentration of 4-ATP needed to obtain the highest surface at the lowest adsorption time was 10 mM. RAIR and Raman spectroscopy for 4-ATP-modified platinum electrodes showed the characteristic adsorption bands for 4-ATP, such as νNH, νCH arom , and νCS arom , indicating the adsorption on the platinum surface. The XPS spectra for the modified Pt surface presented the binding energy peaks of sulfur and nitrogen. High energy resolution XPS studies, RAIR, and Raman spectrum for platinum electrodes modified with 4-ATP indicate that the molecules are sulfur-bonded to the platinum surface. The formation of a S-Pt bond suggests that ATP adsorption leads to an amino-terminated electrode surface. The thickness of the monolayer was evaluated via angle-resolved XPS (AR-XPS) analyses, giving a value of 8 Å. As evidence of the terminal amino group on the electrode surface, the chemical derivatization of the 4-ATP SAM was done with 16-Br hexadecanoic acid. This surface reaction was followed by RAIR spectroscopy.
Journal of Electroanalytical Chemistry, 2000
The electroreflectance (ER) technique has been applied to the study of the electrooxidation of some simple amino acids (glycine, serine and alanine) on a Pt(111) surface in acid medium. A different behaviour in the (1/R)(#R/#E) response as a function of applied potential has been observed during the positive and negative scans as consequence of the formation of adsorbed cyanide originating from the oxidation of glycine and serine. Alanine on the other hand does not readily form significant amounts of adsorbed cyanide on the first oxidation cycle. The integrated ER spectra (DR/R) of the three amino acids have also shown that the reversible adsorption of the glycinate, serinate and alaninate anions is initiated at ca. 0.35 V and reaches maximum coverage at ca. 0.7 V. This reversible adsorption produces changes in the reflectivity comparable to that displayed by bisulphate adsorption.
2013
The electrooxidation of hydroxylamine, NH 2 OH, in 0.1 M phosphate buffer (PB, pH = 7) on Pt-, and Pd-modified Au electrodes prepared by galvanic displacement of underpotential deposited Cu, was investigated by electrochemical techniques and three and in situ vibrational probes, substrate-induced surface enhanced Raman scattering, SI-SERS, surface enhanced infrared absorption, SEIRAS, and Fourier transform infrared reflection-absorption, IRAS, spectroscopies. Analyses of the results obtained made it possible to identify at low overpotentials, solution phase (sol) and adsorbed (ads) nitric oxide, NO, as well as solution phase nitrous oxide, N 2 O. As the potential was increased, the peak(s) ascribed to NO(ads) gained in intensity and new features associated with NO 2 − (ads) and NO 2 − (sol) were clearly discerned. Further excursion toward higher potentials yielded an additional peak assigned to NO 2 (ads). This behavior is analogous to that found for bare Au electrodes in a potential region in which the metal is at least partially oxidized under otherwise the same experimental conditions.
Electrochemical and FTIR studies of l-phenylalanine adsorption at the Au (111) electrode
2001
The adsorption of l-phenylalanine (Phe) at the Au (111) electrode surface has been studied using electrochemical techniques and subtractively normalized interfacial Fourier transform infrared (SNIFTIR) techniques. The electrochemical measurements of cyclic voltammetry, differential capacity and chronocoulometry were used to determine Gibbs energies of adsorption and the reference (E1) and sample (E2) potentials to be used in the spectroscopic measurements.
The Journal of Physical Chemistry C, 2012
Electrodeposited poly(o-toluidine) (POT) on gold electrodes was investigated in a 0.5 M H 2 SO 4 aqueous solution using cyclic electrogravimetry with in situ vis−NIR spectroscopy. This coupling of different techniques allows the electrical, color, and mass changes during the electrochemical reactions of these polymers to be correlated. Therefore, this is a powerful tool to obtain valuable information on the physical models of polymer films and their electrochemical properties. The accurate analysis of the results from these techniques showed the contribution of three different redox transitions (leucoemeraldine−polaron transition, polaron−bipolaron transition, and bipolaron−pernigraniline transition) and the participation of cation (hydrated proton), anion (bisulfate ion), and free solvent (water) transfers in these redox transitions. Moreover, the contributions of each redox transition to the current, absorbance derivative, and mass derivative were separated. Figure 1. Theoretical linear chemical structures of poly(o-toluidine) in the leucoemeraldine form (LE), emeraldine form (EM), and pernigraniline form (PN) doped with anions (A − ).
Electrochimica Acta, 2009
The anodic oxidation of glycine in aqueous electrolyte on smooth platinum electrode was carried out by electrochemical quartz crystal microbalance coupled to cyclic voltammetry technique. Here, we performed electrochemical experiments in concentrated glycine-based electrolyte. Contrary to studies made in diluted medium, the reaction we describe leads to a strongly grafted polymer on the surface at pH values superior to 6, and up to 13, in an irreversible way. The electrodeposited mass is even very significant at pH 13. Several methods such as AFM topography and spectroscopic techniques were performed to characterize the resulting coating. The polymer growth in alkaline conditions during the anodic oxidation of glycine in water probably involves an electrocatalytic step. We showed the presence of amide bonds and then polypeptide formation on the smooth platinum surface. Periodic ab initio calculations on polyglycine II were performed and compared to XPS and vibrational spectra.