Background-Free 3D Nanometric Localization and Sub-nm Asymmetry Detection of Single Plasmonic Nanoparticles by Four-Wave Mixing Interferometry with Optical Vortices
Single particle tracking using optical microscopy is a powerful technique with many applications in biology and material sciences. Despite significant advances, localising objects with nanometric position precision in a scattering environment remains challenging. Applied methods to achieve contrast are dominantly fluorescence based, with fundamental limits in the emitted photon fluxes arising from the excited-state lifetime as well as photobleaching.
These data show a conceptually new way of localising a single nano-object in a scattering environment with position precision at the nanoscale in three-dimensions at high speed, using the vectorial nature of tightly focused light. The method exploits the strong optical absorption and scattering resonance of a single gold nanoparticle, which is detected in a nonlinear way using a sequence of short optical pulses generating resonant four-wave mixing (FWM). This provides a highly sensitive and specific particle detection which does not rely on fluorescence readout, and is completely background-free even in highly scattering environments. By exploiting the optical vortex field pattern in the focus of a high numerical aperture objective, the data show conceptually and experimentally, that is possible to reach a photon shot-noise limited position localization precision of better than 20nm in plane and 1nm axially (an impressive value for axial localisation), with single gold nanoparticles in the 15-30 nm radius range, and single-point acquisition in the 1ms time scale.
The data sets consists of optical microscopy images, electron microscopy images and numerical data.
Optical microscopy images consists of two group: Experimental data and numerical calculations. Experimental data show images of single gold nanoparticles in 3 conditions: i) inside fixed HeLa cells, ii) attached onto a glass surface and surrounded by an index matching liquid (oil), iii) encaged in an agarose gel. Images are acquired using FWM simultaneously with reflectance microscopy. For nanoparticles in cells, differential interference contrast microscopy images are also shown. Numerical images show calculations of the optical signal from single gold nanoparticles in ii) and iii) using the same conditions as in the experiments.
Electron microscopy images show single gold nanoparticles of various sizes (from 5nm to 30nm radius), drop cast onto an appropriate support for transmission electron microscopy.
Numerical data consist of:
1) Calculated and measured values of the FWM field amplitude and phases as a function of the particle position coordinates (using spherical coordinates). The data set are an ascii file with X and Y columns. X is one of the particle coordinates (radial, axial, angular) and Y is the FWM amplitude or phase.
2) Calculated and measured values of the FWM field amplitude and phases as a function of the particle ellipticity and orientation parameters. The data set are an ascii file with X and Y columns. X is one of the particle parameters (ellipticity, orientation angle) and Y is the FWM amplitude or phase.
3) Measured FWM amplitude as a function of delay time between exciting pulses and power. The data set are an ascii file with X and Y columns. X is the delay time or the input power, and Y is the FWM amplitude.
4) Calculated and measured histograms of the occurrence of the amplitude ratio between co- and cross-circularly polarised FWM fields, relative to an input circularly polarised probe field.
5) Experimental particle positions over time. The data set are an ascii file with X and Y columns. X is time and Y is the particle position.
Research results based upon these data are published at http://doi.org/10.1103/PhysRevX.7.041022
Funding
Shedding new light on cells with coherent multiphoton nanoscopy
Engineering and Physical Sciences Research Council
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