Direct observation of narrow mid-infrared plasmon linewidths of single metal oxide nanocrystals

• Published in: Nature communications Vol. 7; no. 1; p. 11583
• Main Authors: Johns, Robert W., Bechtel, Hans A., Runnerstrom, Evan L., Agrawal, Ankit, Lounis, Sebastien D., Milliron, Delia J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 13-05-2016; Nature Publishing Group; Nature Portfolio
• Subjects: 639/301/357; 639/766/400; Absorption spectra; Aluminum; Crystals; Damping; Dopants; Electric fields; Gold; Heterogeneity; Humanities and Social Sciences; Infrared analysis; Inhomogeneity; MATERIALS SCIENCE; Metal oxides; Metals; multidisciplinary; Nanocrystals; nanoscale materials; Nanospheres; optical physics; Organic chemistry; Science; Science (multidisciplinary); Vibrations; Zinc; Zinc oxide
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms11583

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.
Establishing the cause of inhomogeneous broadening would help to produce narrow ensemble localized surface plasmon resonance peaks, favourable for sensing applications. Here, Johns
et al
. use near field optics for enhancing signal contrast, enabling the measurement of mid-infrared spectra of single nanocrystals.