Control of Optical Limiting of Carbon Nanotube Dispersions by Changing Solvent Parameters

Nonlinear optical and optical limiting properties of a range of single-walled carbon nanotube dispersions prepared in N-methyl-2-pyrrolidinone (NMP) were studied using the open aperture Z-scan technique at 532 nm. As the appropriate thermodynamic properties of the solvents are much more important than the bundle size of nanotubes for improving the optical limiting performance, the solvent parameters were controlled by either changing the temperature of the dispersions or blending a secondary solvent. While the optical limiting performance can be varied freely by increasing or decreasing the temperature from room temperature to 100 degrees C, the reduction of temperature below the freezing point of NMP and then down as far as -80 degrees C has little influence on the limiting. performance. As a result of adding a small amount of organic solvent into the NMP dispersions, the nonlinear optical responses were enhanced significantly clue to the reduction of surface tension and other parameters. By contrast, the addition of water leads to a decrease in the optical limiting response. Nanotube dispersions in water/surfactant exhibit a similar limiting performance to the nanotubes in NMP. Our results reveal that the optical limiting performance of the nanotube dispersions can be engineered by adjusting the solvent properties. Because the carbon nanotube dispersions are typical of the thermally induced light scattering dominated optical limiting materials, we believe the conclusions tit not only the nanotubes but also other nanomaterials with the similar limiting mechanism.