Electrochemical and nanogravimetric studies of poly(copper phthalocyanine) microparticles immobilized on gold in aqueous solutions

Katalin Borsos, G. Inzelt

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

An electrochemical quartz crystal nanobalance has been used to study the redox behavior of poly(copper phthalocyanine) (poly(CuPc)) microparticles attached to gold. The electrodes were investigated in contact with aqueous solutions at different pH values. In acid solutions, in the pH range from 0 to 3, one pair of reduction and reoxidation waves can be detected in the potential region from 0.8 V vs. SCE to the beginning of the hydrogen evolution. Until 0.8 V, no oxidation of the poly(CuPc) sample occurs. The reduction is accompanied with a mass increase; the original mass of the surface layer is regained during reoxidation. Below pH 0, two pairs of waves appear attesting the formation of the doubly protonated poly(CuPc). A ca. −60 mV/pH dependence of the peak potentials indicates the participation of H+ ions in the redox reactions in an 1 H+/1 e ratio in acidic and neutral solutions and the formation of 1 OH ion/1 e in basic electrolytes. In neutral and alkaline solutions, however, the mass changes become more complicated. In alkaline media, during electroreduction, a mass decrease occurs in the beginning of the reduction which is followed by a mass increase. In the course of reoxidation, the opposite pattern can be detected in respect of the mass changes. The peak currents show a minimum value at neutral pH. On the other hand, the mass changes are substantially higher in alkaline solutions than in acidic ones, i.e., the apparent molar mass values that can be determined are much higher, which is related to the dimerization causing a structural change and dehydration of the layer. The redox processes can be assigned to the reduction and oxidation of the Pc ring. The mass changes are related to the sorption and desorption of counterions and solvent molecules; however, coions also enter and leave the layer. Based on these observations, redox schemes are proposed.

Original languageEnglish
Pages (from-to)2565-2577
Number of pages13
JournalJournal of Solid State Electrochemistry
Volume19
Issue number9
DOIs
Publication statusPublished - Sep 5 2015

Fingerprint

microparticles
Gold
gold
aqueous solutions
Copper
copper
Ions
Oxidation
Quartz
Dimerization
Molar mass
Redox reactions
Dehydration
Contacts (fluid mechanics)
Electrolytes
Sorption
Hydrogen
Desorption
copper phthalocyanine
oxidation

Keywords

  • Electrochemical quartz crystal nanobalance (EQCN)
  • Microparticles
  • Poly(copper phthalocyanine)
  • Redox transformations
  • Structural changes

ASJC Scopus subject areas

  • Electrochemistry
  • Electrical and Electronic Engineering
  • Condensed Matter Physics
  • Materials Science(all)

Cite this

@article{547e0428a5d34527b1c56f725612262d,
title = "Electrochemical and nanogravimetric studies of poly(copper phthalocyanine) microparticles immobilized on gold in aqueous solutions",
abstract = "An electrochemical quartz crystal nanobalance has been used to study the redox behavior of poly(copper phthalocyanine) (poly(CuPc)) microparticles attached to gold. The electrodes were investigated in contact with aqueous solutions at different pH values. In acid solutions, in the pH range from 0 to 3, one pair of reduction and reoxidation waves can be detected in the potential region from 0.8 V vs. SCE to the beginning of the hydrogen evolution. Until 0.8 V, no oxidation of the poly(CuPc) sample occurs. The reduction is accompanied with a mass increase; the original mass of the surface layer is regained during reoxidation. Below pH 0, two pairs of waves appear attesting the formation of the doubly protonated poly(CuPc). A ca. −60 mV/pH dependence of the peak potentials indicates the participation of H+ ions in the redox reactions in an 1 H+/1 e− ratio in acidic and neutral solutions and the formation of 1 OH− ion/1 e− in basic electrolytes. In neutral and alkaline solutions, however, the mass changes become more complicated. In alkaline media, during electroreduction, a mass decrease occurs in the beginning of the reduction which is followed by a mass increase. In the course of reoxidation, the opposite pattern can be detected in respect of the mass changes. The peak currents show a minimum value at neutral pH. On the other hand, the mass changes are substantially higher in alkaline solutions than in acidic ones, i.e., the apparent molar mass values that can be determined are much higher, which is related to the dimerization causing a structural change and dehydration of the layer. The redox processes can be assigned to the reduction and oxidation of the Pc ring. The mass changes are related to the sorption and desorption of counterions and solvent molecules; however, coions also enter and leave the layer. Based on these observations, redox schemes are proposed.",
keywords = "Electrochemical quartz crystal nanobalance (EQCN), Microparticles, Poly(copper phthalocyanine), Redox transformations, Structural changes",
author = "Katalin Borsos and G. Inzelt",
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T1 - Electrochemical and nanogravimetric studies of poly(copper phthalocyanine) microparticles immobilized on gold in aqueous solutions

AU - Borsos, Katalin

AU - Inzelt, G.

PY - 2015/9/5

Y1 - 2015/9/5

N2 - An electrochemical quartz crystal nanobalance has been used to study the redox behavior of poly(copper phthalocyanine) (poly(CuPc)) microparticles attached to gold. The electrodes were investigated in contact with aqueous solutions at different pH values. In acid solutions, in the pH range from 0 to 3, one pair of reduction and reoxidation waves can be detected in the potential region from 0.8 V vs. SCE to the beginning of the hydrogen evolution. Until 0.8 V, no oxidation of the poly(CuPc) sample occurs. The reduction is accompanied with a mass increase; the original mass of the surface layer is regained during reoxidation. Below pH 0, two pairs of waves appear attesting the formation of the doubly protonated poly(CuPc). A ca. −60 mV/pH dependence of the peak potentials indicates the participation of H+ ions in the redox reactions in an 1 H+/1 e− ratio in acidic and neutral solutions and the formation of 1 OH− ion/1 e− in basic electrolytes. In neutral and alkaline solutions, however, the mass changes become more complicated. In alkaline media, during electroreduction, a mass decrease occurs in the beginning of the reduction which is followed by a mass increase. In the course of reoxidation, the opposite pattern can be detected in respect of the mass changes. The peak currents show a minimum value at neutral pH. On the other hand, the mass changes are substantially higher in alkaline solutions than in acidic ones, i.e., the apparent molar mass values that can be determined are much higher, which is related to the dimerization causing a structural change and dehydration of the layer. The redox processes can be assigned to the reduction and oxidation of the Pc ring. The mass changes are related to the sorption and desorption of counterions and solvent molecules; however, coions also enter and leave the layer. Based on these observations, redox schemes are proposed.

AB - An electrochemical quartz crystal nanobalance has been used to study the redox behavior of poly(copper phthalocyanine) (poly(CuPc)) microparticles attached to gold. The electrodes were investigated in contact with aqueous solutions at different pH values. In acid solutions, in the pH range from 0 to 3, one pair of reduction and reoxidation waves can be detected in the potential region from 0.8 V vs. SCE to the beginning of the hydrogen evolution. Until 0.8 V, no oxidation of the poly(CuPc) sample occurs. The reduction is accompanied with a mass increase; the original mass of the surface layer is regained during reoxidation. Below pH 0, two pairs of waves appear attesting the formation of the doubly protonated poly(CuPc). A ca. −60 mV/pH dependence of the peak potentials indicates the participation of H+ ions in the redox reactions in an 1 H+/1 e− ratio in acidic and neutral solutions and the formation of 1 OH− ion/1 e− in basic electrolytes. In neutral and alkaline solutions, however, the mass changes become more complicated. In alkaline media, during electroreduction, a mass decrease occurs in the beginning of the reduction which is followed by a mass increase. In the course of reoxidation, the opposite pattern can be detected in respect of the mass changes. The peak currents show a minimum value at neutral pH. On the other hand, the mass changes are substantially higher in alkaline solutions than in acidic ones, i.e., the apparent molar mass values that can be determined are much higher, which is related to the dimerization causing a structural change and dehydration of the layer. The redox processes can be assigned to the reduction and oxidation of the Pc ring. The mass changes are related to the sorption and desorption of counterions and solvent molecules; however, coions also enter and leave the layer. Based on these observations, redox schemes are proposed.

KW - Electrochemical quartz crystal nanobalance (EQCN)

KW - Microparticles

KW - Poly(copper phthalocyanine)

KW - Redox transformations

KW - Structural changes

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