Two-Photon Photolysis of 2-Nitrobenzaldehyde Monitored by Fluorescent-Labeled Nanocapsules

Abstract

In this paper, we report, for the first time, experimental evidence of multiphoton photolysis of a caged proton compound, 2-nitrobenzaldehyde (o-NBA), using a new sensor system that utilizes fluorescent-labeled nanocapsules, i.e., a fluorescent nanostructured shell of micrometric size and nanometric thickness. The photolabile compound undergoes one-photon absorption in the UV range (200−380 nm), and the mechanism that leads to proton release is based on the well-known 2-nitrobenzyl photochemistry, which has been used for many photoactivatable-caged compounds. Because the use of UV excitation can cause biological damage, we changed our focus to multiphoton absorption−uncaging processes. The induced pH decrease was monitored by imaging changes in the pH-dependent emission of fluorescein isothiocyanate that was embedded in a nanostructured system (so-called “nanocapsules”). The nanocapsules with covalently bound dyes allow improved stability in fluorescence monitoring. Moreover, an original image processing ...