Electrochemical Properties of Two Dimensional Assemblies of Insulating Diamond Particles

Wiphada Hongthani, Neil A. Fox, David J. Fermin*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

16 Citations (Scopus)

Abstract

The electrochemical properties of two-dimensional assemblies of 500 nm type Ib diamond particles are investigated as a function of their surface oxidation state. High Pressure High Temperature particles are sequentially exposed to a hot strong acid bath and to H-2 plasma in order to generate oxygen (ODP) and hydrogen surface terminations (HDP). Changes in the surface composition following the chemical treatments are confirmed by FTIR Electrophoretic mobility measurement:, show that the diamond particles exhibit a negative surface charge at pH above 7 independently of the surface termination. Oxidation in the acid bath and subsequent reduction in the H-2 plasma only affects about 30% of the particle surface charge. The intrinsic negative charge allows the formation of 2D assemblies by electrostatic adsorption on poly(diallyldimethylammonium chloride) (PDADMAC) modified In-doped SnO2 electrodes (ITO). The particle number density in the assembly was controlled by the adsorption time up to a maximum coverage of ca. 40%. Cyclic voltammetry in the absence of redox species in solution show that the acid treatment effectively removes responses associated with sp(2) carbon impurities, resulting in a potential independent capacitive signal. On the other hand, HDP assemblies are characterized by a charging process at a potential above 0.1 V vs Ag/AgCl. These responses are associated with hole-injection into the valence band edge which is shifted to approximately -4.75 eV vs vacuum upon hydrogenation. Information concerning the position of the valence band edge as well as hole number density at the HDP surface as a function of the applied potential are extracted from the electrochemical analysis.

Translated title of the contributionElectrochemical Properties of Two Dimensional Assemblies of Insulating Diamond Particles
Original languageEnglish
Pages (from-to)5112-5118
Number of pages7
JournalLangmuir
Volume27
Issue number8
DOIs
Publication statusPublished - 19 Apr 2011

Keywords

  • DIAMOND/AQUEOUS ELECTROLYTE INTERFACE
  • VAPOR-DEPOSITED DIAMOND
  • NITROGEN-DOPED DIAMOND
  • SURFACE CONDUCTIVITY
  • NANOCRYSTALLINE DIAMOND
  • NANODIAMOND PARTICLES
  • NANOSCALE DIAMOND
  • NANOPARTICLES
  • AFFINITY
  • FILMS

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