Two-photon enhancement in organic nanorods

The nonlinear optical response in one-dimensional organic nanorods of N,N-dimethy1-4-4((4-(trifluoro-methylsulfonyl)phenyi)ethynyl)aniline (DMFSPA) was investigated to probe the long-range interactions in the nanocrystals on the microscopic level. Differences in the linear and nonlinear optical properties are shown for two different morphologies of these organic crystals as well as for the chromophore in solution. The optimized nanocrystalline suspension had more than an order of magnitude increase in the two-photon excited fluorescence when compared to the solution phase of DMFSPA at similar chromophore densities. The one and two-photon properties of the nanocrystals and bulk crystals are compared by near-field scanning optical multiscope imaging. The images also provide insights into the formation of the nanorods during initial crystallization, changes in the optical response of the system with time, and the viability of these and similar nanomaterials for consideration in solid-state organic device applications. In addition to providing an imaging regime by which to assess this and other solid-state nanocrystalline organics, our investigation provides a simple and elegant method for enhancing the nonlinear optical response of organic materials by transition to nanoscale morphologies, without the need for additional chemical modification or synthesis.