Methods for Molecular Nanoanalysis

Abstract

This contribution reviews methods based on scanning probe microscopy for molecular analysis and identification on a length scale of 20–200 nm. Aperture scanning near-field optical microscopy (SNOM) was initially developed in our group for chemical analysis and imaging using fluorescence and Raman spectroscopies, with a resolution beyond the optical diffraction limit. In recent years, tip-enhanced Raman spectroscopy was developed into an analytical tool capable of a spatial resolution less than 50 nm and, using the 'gap' mode of operation, the promise for single molecule sensitivity and even higher spatial resolution. Aperture SNOM with pulsed laser irradiation can be used for nanoscale laser ablation. With an interface to a very sensitive mass spectrometer, this provides a platform for nanoscale mass spectrometry using atmospheric pressure sampling. The preparation of fiber tips for aperture SNOM as well as metallized a FM tips and etched metal wires for aperture less SNOM applications is reviewed. Finally, applications for the chemical analysis of thin molecular films and of biological samples are presented.