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Scanning Near-Field Optical Microscopy (SNOM)

Techniques

  1. Gerd Kaupp

Published Online: 15 MAR 2012

DOI: 10.1002/9780470661345.smc045

Supramolecular Chemistry: From Molecules to Nanomaterials

Supramolecular Chemistry: From Molecules to Nanomaterials

How to Cite

Kaupp, G. 2012. Scanning Near-Field Optical Microscopy (SNOM). Supramolecular Chemistry: From Molecules to Nanomaterials. .

Author Information

  1. University of Oldenburg, Oldenburg, Germany

Publication History

  1. Published Online: 15 MAR 2012

Abstract

The successful artifact-free scanning near-field optical microscopy (SNOM) for rough surfaces with the versatile apertureless internal reflection in the shear-force gap technique is reviewed and compared with the difficulties associated with apertureless scattering and aperture SNOM techniques. The most economical technique requires sharp, economically self-pulled, tapered waveguide tips and is enabled by a unique reflection enhancement in the shear-force gap that depends linearly on the damping settings. Owing to numerous factors that determine the enhancement, strong chemical contrasts are obtained even between similar materials on composite materials. Unlike aperture SNOM, the contrast in an internal-reflection SNOM is precisely at the site of the chemical interface and the optical resolution is below 10 nm, which is equal to or better than the simultaneous AFM resolution at tip radii of about 10 nm. This enables efficient local spectroscopy (fluorescence, Raman, SERS), industrial (dental alloys, textile dyeing, nanoparticle dyes, sustainable chemical production, etc.), and medicinal applications (organelles, cancer prediagnosis, etc.), and helps in the elucidation of supramolecular mechanisms, all at the nanometric level. SNOM analyses of waste-free supramolecular gas–solid and solid–solid reactions secure far-reaching anisotropic molecular migrations within crystals, and also in solid-state photoreactions. Such mechanistic foundation was not possible with previous “topochemistry” hypotheses, which impeded the maturing of the unparalleled sustainable supramolecular productions, by forbidding these migrations.

Keywords:

  • apertureless and aperture SNOM performances;
  • artifact-free SNOM on rough surfaces;
  • chemical contrast;
  • enhanced internal reflection effect;
  • industrial and medicinal applications;
  • local spectroscopy;
  • nanoparticles;
  • optical resolution below 10 nm;
  • shear-force gap;
  • supramolecular mechanisms