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Structure, Electronic Properties, and Electrochemical Behavior of a Boron-Doped Diamond/Quartz Optically Transparent Electrode Naihara Wac̈ hter,† Catherine Munson,‡ Romana Jarošová,‡ Isil Berkun,§ Timothy Hogan,§ Romeu C. Rocha-Filho,† and Greg M. Swain*,‡ †
Departamento de Química, Universidade Federal de São Carlos, C. P. 676, 13560-970 São Carlos, SP, Brazil Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States § Department of Computer and Electrical Engineering, Michigan State University, East Lansing, Michigan 48824, United States ‡
ABSTRACT: The morphology, microstructure, chemistry, electronic properties, and electrochemical behavior of a boron-doped nanocrystalline diamond (BDD) thin film grown on quartz were evaluated. Diamond optically transparent electrodes (OTEs) are useful for transmission spectroelectrochemical measurements, offering excellent stability during anodic and cathodic polarization and exposure to a variety of chemical environments. We report on the characterization of a BDD OTE by atomic force microscopy, optical spectroscopy, Raman spectroscopic mapping, alternating-current Hall effect measurements, X-ray photoelectron spectroscopy, and electrochemical methods. The results reported herein provide the first comprehensive study of the relationship between the physical and chemical structure and electronic properties of a diamond OTE and the electrode’s electrochemical activity. KEYWORDS: optically transparent diamond electrode, optical, chemical, and electronic properties, electrochemical characterization, ionic liquids
1. INTRODUCTION The use of diamond as an optically transparent electrode (OTE) for spectroelectrochemical measurements was first reported back in the early 2000s.1,2 Our group and others have made use of either free-standing diamond plates or thin films of boron-doped diamond (BDD) deposited on quartz for transmission spectroelectrochemical measurements in the UV− vis region of the electromagnetic spectrum1,3−6 or on undoped Si for measurements in the mid- to far-IR region.2,7 In our opinion, the use of optically transparent diamond electrodes in spectroelectrochemistry is an underdeveloped area of research with this material. BDD possesses attractive qualities as an OTE: a wide optical window, a wide working potential window (>3 V in aqueous media), low background current, microstructural stability during anodic and cathodic polarization, and resistance to molecular adsorption and fouling.1,4−8 Depending on the doping level and film thickness, diamond films are transparent in the visible (300−700 nm) and mid- to far-IR (
