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Colloidal ReO3 Nanocrystals: Extra Re d-Electron Instigating a Plasmonic Response

preprint
submitted on 02.07.2019 and posted on 03.07.2019 by Sandeep Ghosh, Hsin-Che Lu, Shin Hum Cho, Thejaswi Maruvada, Murphie C. Price, Delia Milliron

Rhenium (+6) oxide (ReO3) is metallic in nature, which means it can sustain localized surface plasmon resonance (LSPR) in its nanocrytalline form. Herein, we describe the colloidal synthesis of nanocrystals (NCs) of this compound, through a hot-injection route entail- ing the reduction of rhenium (+7) oxide with a long chain ether. This synthetic protocol is fundamentally different from the more widely em- ployed nucleophilic lysing of metal alkylcarboxylates for other metal oxide NCs. Owing to this difference, the NC surfaces are populated by ether molecules through an L-type coordination along with covalently bound (X-type) hydroxyl moieties, which enables easy switching from nonpolar to polar solvents without resorting to cumbersome ligand exchange procedures. These as-synthesized NCs exhibit absorption bands at around 590 nm (≈2.1 eV) and 410 nm (≈3 eV), which were respectively ascribed to their LSPR and interband absorptions by Mie theory simulations and Drude modeling. The LSPR response arises from the oscillation of free electron density created by the extra Re d-electron per ReO3 unit in the NC lattice, which resides in the conduction band. Further, the LSPR contribution facilitates the observation of dynamic optical modulation of the NC films as they undergo progressive electrochemical charging via ion (de)insertion. Ion (de)insertion leads to distinct dynamic optical signatures, and these changes are reversible in a wide potential range depending on the choice of the ion (lithium or tetrabu- tylammonium). Nanostructuring in ReO3 and the description of the associated plasmonic properties of these NCs made this optical modulation feasible, which were hitherto not reported for the bulk material. We envisage that the synthetic protocol described here will facilitate further exploration of such applications and fundamental studies of these plasmonic NCs

Funding

NSF CHE- 1609656

NSF CBET-1704634

MRSEC DMR-1720595

The Welch Foundation (F-1848)

The Fulbright Program (IIE-15151071)

CBMM

History

Email Address of Submitting Author

sandeep.ghosh@utexas.edu

Institution

The University of Texas at Austin

Country

USA

ORCID For Submitting Author

0000-0002-1149-9199

Declaration of Conflict of Interest

No conflict of interest

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