In this paper, we demonstrate the capability of aperture scanning near-field optical microscopy (SNOM) to attain topography-free sub-surface fluorescence imaging with sub-diffraction resolution on supramolecular aggregates of amphiphilic b-cyclodextrins (CDs) and porphyrins. The system is prepared by mixing CD covalently tagged with a dansyl fluorescent group (SC6CDDns) and CD targeted by receptor specific group (SC6CDGal). Static and Dynamic Light Scattering show that the formed nanoaggregate is constituted by both SC6CDDns and SC6CDGal species. The mixed nanoaggregates (MixCDDansGal) can encapsulate cationic porphyrins (H₂T₄) in solution as shown by batochromic shift of H₂T₄ Soret band in UV-Visible spectra. Solutions of MixCDDansGal/H₂T₄ at 10:1 molar ratio have been cast onto glass substrates, evaporated overnight and analysed by SNOM. We have imaged localized porphyrin aggregates, fluorescing at l_fluo ~ 660 nm, below the surface of mixed porphyrin-cyclodextrin micrometric vesicles, with 150 nm spatial resolution. Similarly, nano-bubbles have been localized below the surface of thin films of amphiphilic b-cyclodextrin, marked with dansyl fluorescent molecules (l_fluo> 500 nm). Both commercial and homemade optical fiber probes have been used. SNOM subsurface imaging opens up fascinating possibilities for chemical and structural analysis at the nanometer scale of nanocomposite materials, bio-recognition of carriers including drugs and specific receptor protein or single fluorescent molecules embedded under transparent membranes.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/12183 must be provided.

1. Study of the light depolarization induced by sharp dielectric and metallic tips and of its effects on the selection rules of polarized Tip-Enhanced Raman Scattering on crystals