Investigation of Fluorescence Dynamics of BODIPY Embedded in Porous Silicon and Monitoring Formation of a SiO2 Layer via a Confocal FLIM-Based NSET Method

The decay dynamics of BODIPY dye molecules embedded in porous silicon nanostructures produced by electrochemical etching of a silicon wafer in an HF solution are investigated using a confocal fluorescence lifetime imaging technique. Time-resolved experiments show that there is an efficient energy-transfer mechanism between BODIPY and porous silicon. It is observed that such an energy-transfer efficiency strongly depends on the thickness of the silicon dioxide layer covering the porous silicon. Silicon nanostructures are oxidized over time in air. As oxidation increases, the energy-transfer rate decreases. This change in energy-transfer rate seems to obey the NSET mechanism, which allows us to obtain a three-dimensional topographic map of the developed oxide layer on the rough and complicated surface of a porous silicon nanostructure.