Single-molecule optical absorption imaging by nanomechanical photothermal sensing

Absorption microscopy is a promising alternative to fluorescence microscopy for single-molecule imaging. So far, molecular absorption has been probed optically via the attenuation of a probing laser or via photothermal effects. The sensitivity of optical probing is not only restricted by background...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2018-10, Vol.115 (44), p.11150-11155
Main Authors: Chien, Miao-Hsuan, Brameshuber, Mario, Rossboth, Benedikt K., Schütz, Gerhard J., Schmid, Silvan
Format: Article
Language:English
Subjects:
Absorption
Attenuation
Background noise
Drum
Fluorescence
Fluorescence microscopy
Gold
Gold - chemistry
Heating
Irradiance
Laser beam heating
Lasers
Light
Localization
Microscopy
Microscopy - methods
Molecular absorption
Molecular physics
Nanoparticles
Nanoparticles - chemistry
Nanostructures - chemistry
Nanotechnology - methods
Optics and Photonics - methods
Physical Sciences
Resonant frequencies
Scanners
Scattering
Scattering, Radiation
Sensitivity
Sensors
Shot noise
Signal to noise ratio
Silicon Compounds - chemistry
Silicon nitride
Silicon substrates
Temperature
Temperature effects
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Summary:Absorption microscopy is a promising alternative to fluorescence microscopy for single-molecule imaging. So far, molecular absorption has been probed optically via the attenuation of a probing laser or via photothermal effects. The sensitivity of optical probing is not only restricted by background scattering but it is fundamentally limited by laser shot noise, which minimizes the achievable single-molecule signal-to-noise ratio. Here, we present nanomechanical photothermal microscopy, which overcomes the scattering and shot-noise limit by detecting the photothermal heating of the sample directly with a temperature-sensitive substrate. We use nanomechanical silicon nitride drums, whose resonant frequency detunes with local heating. Individual Au nanoparticles with diameters from 10 to 200 nm and single molecules (Atto 633) are scanned with a heating laser with a peak irradiance of 354 ± 45 μW/μm² using 50× long-working-distance objective. With a stress-optimized drum we reach a sensitivity of 16 fW/Hz1/2 at room temperature, resulting in a single-molecule signal-to-noise ratio of >70. The high sensitivity combined with the inherent wavelength independence of the nanomechanical sensor presents a competitive alternative to established tools for the analysis and localization of nonfluorescent single molecules and nanoparticles.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1804174115