Magnetically dependent photoluminescence of tetracene nanoparticles

Tetracene nanocrystals prepared by the reprecipitation method are investigated using magnetophotoluminescence, steady-state optical absorption and emission spectroscopies. The steady-state absorption spectra indicate that the tetracene nanoparticles possess a crystalline structure. The magnetic field dependence of photoluminescence for tetracene nanoparticles has a range almost 40 times smaller than that for tetracene macrocrystals. This result is interpreted within the framework of a theoretical model based on the solution of the diffusion equation for a restricted spherical volume. The calculations show that this decrease in magnetic field dependences of photoluminescence can be sensitive to the size of tetracene crystals. According to the theoretical model, the triplet-triplet annihilation rate increases in nanostructured tetracene.