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Cite This: ACS Appl. Nano Mater. XXXX, XXX, XXX−XXX
Electron Transfer and Near-Field Mechanisms in Plasmonic GoldNanoparticle-Modified TiO2 Photocatalytic Systems Ramesh Asapu,†,⊥ Nathalie Claes,‡ Radu-George Ciocarlan,§ Matthias Minjauw,∥ Christophe Detavernier,∥ Pegie Cool,§ Sara Bals,‡ and Sammy W. Verbruggen*,†
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Department of Bioscience Engineering, Sustainable Energy Air & Water Technology, Campus Groenenborger, University of Antwerp, Groenenborgerlaan 171, Antwerp 2020, Belgium ‡ Department of Physics, EMAT Research Group, Campus Groenenborger, University of Antwerp, Antwerp 2020, Belgium § Department of Chemistry, LADCA Research Group, Campus Drie Eiken, University of Antwerp, Antwerp 2610, Belgium ∥ Department of Solid State Sciences, CoCooN Research Group, Ghent University, Krijgslaan 281/S1, Ghent 9000, Belgium S Supporting Information *
ABSTRACT: The major mechanism responsible for plasmonic enhancement of titanium dioxide photocatalysis using gold nanoparticles is still under contention. This work introduces an experimental strategy to disentangle the significance of the charge transfer and near-field mechanisms in plasmonic photocatalysis. By controlling the thickness and conductive nature of a nanoparticle shell that acts as a spacer layer separating the plasmonic metal core from the TiO2 surface, field enhancement or charge transfer effects can be selectively repressed or evoked. Layer-by-layer and in situ polymerization methods are used to synthesize gold core− polymer shell nanoparticles with shell thickness control up to the sub-nanometer level. Detailed optical and electrical characterization supported by near-field simulation models corroborate the trends in photocatalytic activity of the different systems. This approach mainly points at an important contribution of the enhanced near field. KEYWORDS: gold, titanium dioxide, surface plasmon resonance (SPR), hot electron, near field, charge transfer, core−shell
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INTRODUCTION The diverse application of plasmonic gold nanoparticles in multiple study fields such as photocatalysis1−8 and sensing applications9−12 has driven a tremendous amount of research. In the field of plasmon-enhanced photocatalysis, extensive research has been done with gold nanoparticles as it has been shown to improve the photocatalytic efficiency.13−18 Although plasmonic gold-modified TiO2 photocatalytic systems are widely reported to have better performance than pristine TiO2 systems, the primary mechanism responsible for this enhancement is still under debate.2,17,19−22 This study presents a novel approach to acquire new insights in the contributions from both the charge transfer (often also referred to as “hot electron”) and near-field enhancement mechanisms; the most frequently discussed theories related to plasmonic Au-TiO2 photocatalytic systems using small (
