title: Direct observation of narrow mid-infrared plasmon linewidths of single metal oxide nanocrystals.
abstract: Infrared-responsive doped metal oxide nanocrystals are an emerging class of plasmonic materials whose localized surface plasmon resonances (LSPR) can be resonant with molecular vibrations. This presents a distinctive opportunity to manipulate light-matter interactions to redirect chemical or spectroscopic outcomes through the strong local electric fields they generate. Here we report a technique for measuring single nanocrystal absorption spectra of doped metal oxide nanocrystals, revealing significant spectral inhomogeneity in their mid-infrared LSPRs. Our analysis suggests dopant incorporation is heterogeneous beyond expectation based on a statistical distribution of dopants. The broad ensemble linewidths typically observed in these materials result primarily from sample heterogeneity and not from strong electronic damping associated with lossy plasmonic materials. In fact, single nanocrystal spectra reveal linewidths as narrow as 600 cm(-1) in aluminium-doped zinc oxide, a value less than half the ensemble linewidth and markedly less than homogeneous linewidths of gold nanospheres.
authors.affiliation: Department of Chemistry, University of California, Berkeley, California 94720, USA.|McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street, Austin, Texas 78712, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Johns
authors.affiliation: Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Hans A
authors.initials: HA
authors.lastname: Bechtel
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street, Austin, Texas 78712, USA.|Department of Materials Science and Engineering, University of California, Berkeley, California 94720, USA.
authors.forename: Evan L
authors.initials: EL
authors.lastname: Runnerstrom
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street, Austin, Texas 78712, USA.
authors.forename: Ankit
authors.initials: A
authors.lastname: Agrawal
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street, Austin, Texas 78712, USA.|Graduate Program in Applied Science and Technology, University of California, Berkeley, California 94720, USA.
authors.forename: Sebastien D
authors.initials: SD
authors.lastname: Lounis
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street, Austin, Texas 78712, USA.
authors.forename: Delia J
authors.initials: DJ
authors.lastname: Milliron