Figure 5. Photochemical effects due to upconverted ultraviolet fluorescence.
(a) Self-assembly of a SIL by isotropic exposure of negative-tone photoresist with ultraviolet emission of a nanoparticle. (b) Reconstructed 3D atomic force microscopy (AFM) image of a self-assembled SIL. Lateral size of the image is 6.6×6.6 μm2. (c) Light microscope image of HeLa cells on the surface of Pr:YAG crystal exposed by a combination of 609+532 nm lasers. Most of the cells died (round shaped). (d) Image of the cells exposed by a combination of wavelengths 600+532 nm (no upconverted ultraviolet is produced). Most of the cells are alive. The same fraction of live cells is found in the unexposed region. Scale bars on (c,d) correspond to 50 μm.