Imaging Infrared Plasmon Hybridization in Doped Semiconductor Nanocrystal Dimers.

Carrier-doped semiconductor nanocrystals (NCs) offer strong plasmonic responses at frequencies beyond those accessible by conventional plasmonic nanoparticles. Like their noble metal analogues, these emerging materials can harness free space radiation and confine it to the nanoscale but at resonance frequencies that are natively infrared and spectrally tunable by carrier concentration. In this work we combine monochromated STEM-EELS and theoretical modeling to investigate the capability of colloidal indium tin oxide (ITO) NC pairs to form hybridized plasmon modes, providing an additional route to influence the IR plasmon spectrum. These results demonstrate that ITO NCs may have greater coupling strength than expected, emphasizing their potential for near-field enhancement and resonant energy transfer in the IR region.

Electron Beam Infrared Nano-Ellipsometry of Individual Indium Tin Oxide Nanocrystals.

Leveraging recent advances in electron energy monochromation and aberration correction, we record the spatially resolved infrared plasmon spectrum of individual tin-doped indium oxide nanocrystals using electron energy-loss spectroscopy (EELS). Both surface and bulk plasmon responses are measured as a function of tin doping concentration from 1-10 atomic percent. These results are compared to theoretical models, which elucidate the spectral detuning of the same surface plasmon resonance feature when measured from aloof and penetrating probe geometries. We additionally demonstrate a unique approach to retrieving the fundamental dielectric parameters of individual semiconductor nanocrystals via EELS. This method, devoid from ensemble averaging, illustrates the potential for electron-beam ellipsometry measurements on materials that cannot be prepared in bulk form or as thin films.

Direct Observation of Infrared Plasmonic Fano Antiresonances by a Nanoscale Electron Probe.

In this Letter, we exploit recent breakthroughs in monochromated aberration-corrected scanning transmission electron microscopy (STEM) to resolve infrared plasmonic Fano antiresonances in individual nanofabricated disk-rod dimers. Using a combination of electron energy-loss spectroscopy and theoretical modeling, we investigate and characterize a subspace of the weak coupling regime between quasidiscrete and quasicontinuum localized surface plasmon resonances where infrared plasmonic Fano antiresonances appear. This work illustrates the capability of STEM instrumentation to experimentally observe nanoscale plasmonic responses that were previously the domain only of higher-resolution infrared spectroscopies.

Combinatorial Thin Film Sputtering Au xAl1- x Alloys: Correlating Composition and Structure with Optical Properties.

The Au-Al alloy system was investigated via a combinatorial thin film sputtering method for its potential as a plasmonic material. Au xAl1- x combinatorial libraries were cosputtered from Au and Al elemental targets and the composition, phase, and dielectric function of a ∼350 nm film was determined using energy dispersive spectroscopy (EDS), grazing incidence X-ray diffraction (GIXRD), and spectroscopic ellipsometry, respectively. The phase evolution and optical properties were analyzed after annealing various compositions under a vacuum. The phases present matched the expected phases based on the published Al-Au binary phase diagram at all compositions. Interestingly, the mixed phase Al-AuAl2 region showed the most optical tunability, where a maximum in the real part of the dielectric function progressively shifted to higher energy for increasing gold concentration. For almost pure AuAl2, the imaginary component is largely reduced in the visible range and is comparable to that of pure Al in the UV region. A 20-nm-thick film with composition Au0.74Al0.26 was studied using a (scanning) transmission electron microscope with an in situ laser heating system. The structures of the as-deposited and laser annealed films were determined using selected area diffraction and the bulk plasmon of AuAl2 and Al realized with electron energy loss spectroscopy. Last, the Au-rich solid solution region was investigated as a surface enhanced Raman spectroscopy (SERS) substrate using the benezenethiol (BT) molecule. Good SERS intensity was maintained up to 30% Al addition where enhancements of 105 to 107 were still observed.

Differences in physical activity among youth with and without intellectual disability.

INTRODUCTION: Very little is known about physical activity (PA) and PA patterns measured with objective methods among children with intellectual disability (ID). PURPOSE: This study aimed to investigate PA and PA patterns among Icelandic school children with mild-to-severe ID. METHODS: A sample of 91 children with ID and a randomly selected age- and sex-matched group of 93 typically developed individuals (TDI) took part in the study. Basic anthropometric measurements were attained, and PA was assessed with ActiGraph accelerometers for 7-10 consecutive days. A questionnaire was used to collect data on PA behavior. RESULTS: Although children with ID were 40% less physically active and spent 9% more time sedentary than their TDI peers, there was interaction between group and sex (P < 0.05). TDI boys were more active and less sedentary than TDI girls (P < 0.05), but no sex differences were found among children with ID on any PA variable. In addition, there was no difference between workday PA and weekend PA among children with ID. Only 16% of children with ID walked or biked to school, whereas the proportion was 74% among TDI children (P < 0.001). Similarly, a lower fraction (33%) of children with ID took part in 2 h·wk or more in sports compared with TDI children (76%, P < 0.001). No children with ID met the recommendation of 60 min of daily moderate-to-vigorous PA, whereas 40% of the TDI children met the recommendation. CONCLUSIONS: PA of children with ID is considerably lower than that among their TDI peers, and there seem to be no sex differences in PA and PA patterns among children with ID. The fact that no children with ID met the recommended daily MVPA calls for special PA measures in this group.