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Sarfus

Surface-enhanced ellipsometric contrast microscopy, commercially known as Sarfus[1] is a nanodetection technique (an optical nanoscopy technique to make nanostructures visible) based on the association of an upright or inverted optical microscope in crossed polarization configuration and specific supporting plates called surfs on which the sample is deposited for observation.[2]

3D Sarfus image of a DNA biochip.

Sarfus visualization relies on precise control of the reflection properties of polarized light on a surface, enhancing the axial sensitivity of an optical microscope by approximately two orders of magnitude without reducing its lateral resolution.[2] This method increases the sensitivity of standard optical microscopes to a point that it becomes possible to directly visualize thin films (down to 0.3 micrometers) and isolated nano-objects in real-time, be it in air or in water.

Principles

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Observation with standard optical microscope between cross polarizers of Langmuir-Blodgett layers (bilayer thickness: 5.4 nm) on silicon wafer and on surf
 
Light polarization after reflection on a surf (0) and on nanoscale sample on a surf (1).

A 2006 study on polarized light coherence led to the development of new supports (the surfs) having contrast amplification properties for standard optical microscopy in cross polarizers mode.[3] Made of optical layers on an opaque or transparent substrate, these supports do not modify the light polarization after reflection even if the numerical aperture of the incident source is significant. This property is modified when a sample is present on a surf; a non-null light component is then detected after the analyzer, rendering the sample visible.

The performance of these supports is evaluated by measuring the contrast (C) of the sample defined as: C = (I1-I0)/(I0+I1) where I0 and I1 represent the intensities reflected by the bare surf and by the analyzed sample on the surf, respectively. For a one nanometer-film thickness, the surfs display a contrast 200 times higher than on silicon wafer.

This high contrast increase allows the visualization with standard optical microscope of films with thicknesses down to 0.3 nm, as well as nano-objects (down to 2 nm diameter) and this, without any kind of sample labeling (neither fluorescence, nor radioactive marker). An illustration of the contrast enhance is given hereafter with the observation in optical microscopy between cross polarizers of a Langmuir-Blodgett structure on a silicon wafer and on a surf.

In addition to visualization, recent developments have allowed accessing to the thickness measurement of the analyzed sample. A colorimetric correspondence is carried out between a calibration standard made of nano-steps and the analyzed sample. Indeed, due to optical interference, a correlation exists between RGB (red, green, blue) parameters of the sample and its optical thickness. This leads to 3D-representation of the analyzed samples, the measurement of profile sections, roughness and other topological measurements.

Experimental setup

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Samples to be characterized are deposited by techniques such as dip-coating, spin coating, deposit pipette, or evaporation, on a surf instead of the traditional microscope slide. The support is then placed on the microscope stage.[4]

Synergy with existing Equipments

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Sarfus visualization can be integrated into existing analysis equipment, such as atomic force microscopy (AFM) and Raman spectroscopy, to add new functionalities such as optical imaging, thickness measurement, kinetics analysis, and sample pre-localization, which can save time and consumables (e.g., AFM tips).[5]

Applications

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Sarfus images of nanostructures: 1. Copolymer film microstructuration (73 nm), 2. Carbon nanotube bundles, 3. Lipid vesicles in aqueous solutions, 4. Nanopatterning of gold dots (50 nm3).

Life sciences

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Thin films and surface treatment

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Nanomaterials

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Advantages

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Optical microscopy has several advantages compared to the usual techniques of nanocharacterization. It is easy-to-use and directly visualizes the sample. The analysis in real-time allows kinetic studies (real-time crystallization, dewetting, etc.). The broad choice of magnification (2.5 to 100x) allows fields of view from several mm2 to a few tens μm2. Observations can be performed in controlled atmosphere and temperature.

References

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  1. ^ Montgomery, Paul C.; Leong-Hoi, Audrey (2015-09-29). "Emerging optical nanoscopy techniques". Nanotechnology, Science and Applications. 8: 31–44. doi:10.2147/NSA.S50042. PMC 4599210. PMID 26491270.
  2. ^ a b Jones-Bey, Hassaun A. (2006-12-01). "MICROSCOPY: Differential-polarization technique enables precise 3-D nanoimaging". Laser Focus World. Retrieved 2024-11-05.
  3. ^ Ausserré D; Valignat MP (2006). "Wide-field optical imaging of surface nanostructures". Nano Letters. 6 (7): 1384–1388. Bibcode:2006NanoL...6.1384A. doi:10.1021/nl060353h. PMID 16834416.
  4. ^ Sarfus - AmproX
  5. ^ "Sarfus".
  6. ^ Souplet V, Desmet R, Melnyk O (2007). "Imaging of protein layers with an optical microscope for the characterization of peptide microarrays". J. Pept. Sci. 13 (7): 451–457. doi:10.1002/psc.866. PMID 17559066. S2CID 26078821.
  7. ^ Carion O, Souplet V, Olivier C, Maillet C, Médard N, El-Mahdi O, Durand JO, Melnyk O (2007). "Chemical Micropatterning of Polycarbonate for Site-Specific Peptide Immobilization and Biomolecular Interactions". ChemBioChem. 8 (3): 315–322. doi:10.1002/cbic.200600504. PMID 17226879. S2CID 1770479.
  8. ^ Monot J, Petit M, Lane SM, Guisle I, Léger J, Tellier C, Talham DR, Bujoli B (2008). "Towards zirconium phosphonate-based microarrays for probing DNA-protein interactions: critical influence of the location of the probe anchoring groups". J. Am. Chem. Soc. 130 (19): 6243–6251. doi:10.1021/ja711427q. PMID 18407629.
  9. ^ Yunus S, de Crombrugghe de Looringhe C, Poleunis C, Delcorte A (2007). "Diffusion of oligomers from polydimethylsiloxane stamps in microcontact printing: Surface analysis and possible application". Surf. Interf. Anal. 39 (12–13): 922–925. doi:10.1002/sia.2623. S2CID 93335242.
  10. ^ Burghardt S, Hirsch A, Médard N, Abou-Kachfhe R, Ausserré D, Valignat MP, Gallani JL (2005). "Preparation of highly stable organic steps with a fullerene-based molecule". Langmuir. 21 (16): 7540–7544. doi:10.1021/la051297n. PMID 16042492.
  11. ^ Pauliac-Vaujour E, Stannard A, Martin CP, Blunt MO, Notingher I, Moriarty PJ, Vancea I, Thiele U (2008). "Fingering instabilities in dewetting nanofluids" (PDF). Phys. Rev. Lett. 100 (17): 176102. Bibcode:2008PhRvL.100q6102P. doi:10.1103/PhysRevLett.100.176102. PMID 18518311. S2CID 8047821.
  12. ^ Valles C, Drummond C, Saadaoui H, Furtado CA, He M, Roubeau O, Ortolani L, Monthioux M, Penicaud A (2008). "Solutions of Negatively Charged Graphene Sheets and Ribbons". J. Am. Chem. Soc. 130 (47): 15802–15804. doi:10.1021/ja808001a. PMID 18975900.
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