FLUORESCENCE MAPPING AND PHOTOBLEACHING OF DYE-LABELED LATEX-PARTICLES DISPERSED IN POLY(VINYL ALCOHOL) MATRICES WITH A NEAR-FIELD OPTICAL MICROSCOPE

Polymer composite films consisting of fluorescent nanometric dye-label ed latex particles dispersed in poly(vinyl alcohol) matrices were imag ed with a near-field scanning optical microscope (NSOM). Films with a thickness of similar to 10 mu m and of similar to 25 nm containing lat ex particles with a diameter of 103 +/- 9 nm with low particle density were studied. During image acquisition with the NSOM the particles we re excited by an argon ion laser at the maximum or at the red edge of the excitation band at the excitation wavelength, lambda, of lambda = 458 nm or of lambda = 488 nm, respectively. Maximum fluorescence contr ast occurred in the first case. Fluorescence spots with FWHM diameters of <lambda/2 could be found. In the case of the similar to 10 mu m th ick films particles could only be imaged by mapping their fluorescence if they were located at the polymer-air interface. Subinterface parti cles could be detected as well. Additionally, photobleaching of a sing le fluorescent latex particle with a NSOM was performed, demonstrating a controlled photochemical reaction on a submicrometer length scale.