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Zhang L, Vogel YB, Noble BB, et al. TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical. J Am Chem Soc. 2016;138(30):9611-9doi: 10.1021/jacs.6b04788.
Zhang, L., Vogel, Y. B., Noble, B. B., Gonçales, V. R., Darwish, N., Brun, A. L., Gooding, J. J., Wallace, G. G., Coote, M. L., & Ciampi, S. (2016). TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical. Journal of the American Chemical Society, 138(30), 9611-9. https://doi.org/10.1021/jacs.6b04788
Zhang, Long, et al. "TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical." Journal of the American Chemical Society vol. 138,30 (2016): 9611-9. doi: https://doi.org/10.1021/jacs.6b04788
Zhang L, Vogel YB, Noble BB, Gonçales VR, Darwish N, Brun AL, Gooding JJ, Wallace GG, Coote ML, Ciampi S. TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical. J Am Chem Soc. 2016 Aug 03;138(30):9611-9. doi: 10.1021/jacs.6b04788. Epub 2016 Jul 19. PMID: 27373457.
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J Am Chem Soc. 2016 Aug 03;138(30):9611-9. doi: 10.1021/jacs.6b04788. Epub 2016 Jul 19.

TEMPO Monolayers on Si(100) Electrodes: Electrostatic Effects by the Electrolyte and Semiconductor Space-Charge on the Electroactivity of a Persistent Radical.

Journal of the American Chemical Society

Long Zhang, Yan Boris Vogel, Benjamin B Noble, Vinicius R Gonçales, Nadim Darwish, Anton Le Brun, J Justin Gooding, Gordon G Wallace, Michelle L Coote, Simone Ciampi

Affiliations

  1. ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong , Wollongong, New South Wales 2500, Australia.
  2. ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University , Canberra, Australian Capital Territory 2601, Australia.
  3. School of Chemistry, Australian Centre for NanoMedicine and ARC Centre of Excellence for Convergent Bio-Nano Science and Technology, The University of New South Wales , Sydney, New South Wales 2052, Australia.
  4. Institut de Bioenginyeria de Catalunya (IBEC) , Baldiri Reixac 15-21, Barcelona 08028, Catalonia Spain.
  5. Bragg Institute, Australian Nuclear Science and Technology Organisation (ANSTO) , Locked Bag 2001, Kirrawee DC, New South Wales 2232, Australia.

PMID: 27373457 DOI: 10.1021/jacs.6b04788

Abstract

This work demonstrates the effect of electrostatic interactions on the electroactivity of a persistent organic free radical. This was achieved by chemisorption of molecules of 4-azido-2,2,6,6-tetramethyl-1-piperdinyloxy (4-azido-TEMPO) onto monolayer-modified Si(100) electrodes using a two-step chemical procedure to preserve the open-shell state and hence the electroactivity of the nitroxide radical. Kinetic and thermodynamic parameters for the surface electrochemical reaction are investigated experimentally and analyzed with the aid of electrochemical digital simulations and quantum-chemical calculations of a theoretical model of the tethered TEMPO system. Interactions between the electrolyte anions and the TEMPO grafted on highly doped, i.e., metallic, electrodes can be tuned to predictably manipulate the oxidizing power of surface nitroxide/oxoammonium redox couple, hence showing the practical importance of the electrostatics on the electrolyte side of the radical monolayer. Conversely, for monolayers prepared on the poorly doped electrodes, the electrostatic interactions between the tethered TEMPO units and the semiconductor-side, i.e., space-charge, become dominant and result in drastic kinetic changes to the electroactivity of the radical monolayer as well as electrochemical nonidealities that can be explained as an increase in the self-interaction "a" parameter that leads to the Frumkin isotherm.

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