Abstract
Non-noble metal plasmonic materials, e.g. doped semiconductor nanocrystals, compared to their noble metal counterparts, have shown unique advantages, including broadly tunable plasmon frequency (from visible to infrared) and rich surface chemistry. However, the fate and harvesting of hot electrons from these non-noble metal plasmons have been much less explored. Here we report plasmon driven hot electron generation and transfer from plasmonic metal oxide nanocrystals to surface adsorbed molecules by ultrafast transient absorption spectroscopy. We show unambiguously that under infrared light excitation, hot electron transfers in ultrafast timescale (<50 fs) with an efficiency of 1.4%. The excitation wavelength and fluence dependent study indicates that hot electron transfers right after Landau damping before electron thermalization. We revealed the efficiency-limiting factors and provided improvement strategies. This study paves the way for designing efficient infrared light absorption and photochemical conversion applications based on non-noble metal plasmonic materials.
Highlights
Non-noble metal plasmonic materials, e.g. doped semiconductor nanocrystals, compared to their noble metal counterparts, have shown unique advantages, including broadly tunable plasmon frequency and rich surface chemistry
The former assumes that the hot electrons generated in metal nanostructures with energy higher than the lowest-unoccupied-molecular-orbital (LUMO) of the acceptor molecules or metal-semiconductor Schottky barrier can inject into molecules or semiconductors[21]
F and In co-doped CdO (FICO) NCs were synthesized by colloidal method according to the procedure developed by Ye et al.[26]
Summary
Non-noble metal plasmonic materials, e.g. doped semiconductor nanocrystals, compared to their noble metal counterparts, have shown unique advantages, including broadly tunable plasmon frequency (from visible to infrared) and rich surface chemistry. The strong light absorption and hot electron/hole harvesting from plasmonic metal nanostructures have been extensively reported, where plasmon induced hot electron transfer (PIHET) occurs at interface for photochemical[4,5,6,7,8], photovoltaic[9,10], and photodetection applications[11,12]. Unlike metal nanostructures with relatively inert surface, doped semiconductor NCs with rich coordination surface sites enable feasible and tunable surface modification[14] Despite these unique properties, hot-electron harvesting and conversion from doped semiconductor-based plasmon has been rarely reported, except a few recent studies of plasmon induced charge transfer in semiconductor nano-heterostructures and their applications in photocatalysis[15,16,17] and photodetections[18,19]. Together with the pump wavelength- and power-dependent studies, we demonstrate and provide a mechanistic picture of indirect hot-electron transfer from plasmonic semiconductor NCs after Landau damping but before electron thermalization
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