Improving the mismatch between light and nanoscale objects with gold bowtie nanoantennas

Metallic bowtie nanoantennas should provide optical fields that are confined to spatial scales far below the diffraction limit. To improve the mismatch between optical wavelengths and nanoscale objects, we have lithographically fabricated Au bowties with lengths approximately 75 nm and gaps of tens of nm. Using two-photon-excited photoluminescence of Au, the local intensity enhancement factor relative to that for the incident diffraction-limited beam has been experimentally determined for the first time. Enhancements >10(3) occur for 20 nm gap bowties, in good agreement with theoretical simulations.     

Soliton-induced waveguides in an organic photorefractive glass

We demonstrate optical waveguiding of a probe beam at 980 nm by a soliton beam at 780 nm in an organic photorefractive monolithic glass. Both planar and circular waveguides induced by one- and two-dimensional spatial solitons formed as a result of orientationally enhanced photorefractive nonlinearity are produced in the organic glass. Possibilities for increasing the speed of waveguide formation are discussed.     

Calculation of Electronic Structure of Zinc-Blende CdS

The linear-muffin-tin orbital method is used to study the electronic-energy-band structure of zinc-blende CdS. Incorporating the 4d states of Cd into the valence band gives substantially the main-valenceband width, and yields valenceband features in agreement with the experiment. The calculated equilibrium lattice constant is in accord with the measured result. The fundamental band gap is found to be direct at T point and the value is about 1.21 eV. The band structure calculation shows that the present results are in good agreement with experiments and other calculations.     

无机物离子对CuS微晶形态结构的有效调控

以CuCl2·3H2O,Cu（CH3COO）2·H2O和CuSO4·5H2O作为铜源,并向反应体系中引入少量NaCl或NaNO3,通过乙二醇溶剂中的溶剂热反应,合成了形貌各异的CuS微晶．结合XRD和SEM表征,初步探讨了阴离子Cl-、CH3COO-、SO4^2-和阳离子Na’对CuS微晶生长过程的影响．结果表明,Na＋对CuS微晶的生长过程没有显著影响,而Cl、CH3COO-、SO4^2-由于在{1012}晶面上选择性吸附能力的差异,显著影响CuS微晶的形貌．本研究为进一步有效调控CuS微晶的形貌及性能奠定了基础．     

Superresolution imaging of targeted proteins in fixed and living cells using photoactivatable organic fluorophores

Superresolution imaging techniques based on sequential imaging of sparse subsets of single molecules require fluorophores whose emission can be photoactivated or photoswitched. Because typical organic fluorophores can emit significantly more photons than average fluorescent proteins, organic fluorophores have a potential advantage in super-resolution imaging schemes, but targeting to specific cellular proteins must be provided. We report the design and application of HaloTag-based target-specific azido DCDHFs, a class of photoactivatable push-pull fluorogens which produce bright fluorescent labels suitable for single-molecule superresolution imaging in live bacterial and fixed mammalian cells.     

Cryogenic Correlative Single‐Particle Photoluminescence Spectroscopy and Electron Tomography for Investigation of Nanomaterials

Cryogenic single‐particle photoluminescence (PL) spectroscopy has been used with great success to directly observe the heterogeneous photophysical states present in a population of luminescent particles. Cryogenic electron tomography provides complementary nanometer scale structural information to PL spectroscopy, but the two techniques have not been correlated due to technical challenges. Here, we present a method for correlating single‐particle information from these two powerful microscopy modalities. We simultaneously observe PL brightness, emission spectrum, and in‐plane excitation dipole orientation of CdSSe/ZnS quantum dots suspended in vitreous ice. Stable and fluctuating emitters were observed, as well as a surprising splitting of the PL spectrum into two bands with an average energy separation of 80 meV. In some cases, the onset of the splitting corresponded to changes in the in‐plane excitation dipole orientation. These dynamics were assigned to structures of individual quantum dots and the excitation dipoles were visualized in the context of structural features.     

Interferometry of a single nanoparticle using the Gouy phase of a focused laser beam

We provide a quantitative explanation of the mechanism of the far-field intensity modulation induced by a nanoparticle in a focused Gaussian laser beam, as was demonstrated in several recent direct detection studies. Most approaches take advantage of interference between the incident light and the scattered light from a nanoparticle to facilitate a linear dependence of the signal on the nanoparticle volume. The phase relation between the incoming field and the scattered field by the nanoparticle is elucidated by the concept of Gouy phase. This phase relation is used to analyze the far-field signal-to-noise ratio as a function of exact nanoparticle position with respect to the beam focus. The calculation suggests that a purely dispersive nanoparticle should be displaced from the Gaussian beam focus to generate a far-field intensity change.     

Self-trapping of light in an organic photorefractive glass

We report the first observation, to our knowledge, of self-trapping of light as well as optically induced focusing-to-defocusing switching in an organic photorefractive glass, owing to the orientationally enhanced photorefractive nonlinearity of the material.