The synthesis of carbon nanotube based composites with conducting, semiconducting, and insulating coatings and their optical limiting properties

Multiwalled carbon nanotubes (MWCNTs) were individually coated with conducting, semiconducting, and insulating materials. The coatings used were crystalline Au nanoparticles, TiO2 nanoclusters, and amorphous SiO2 nanoshells, respectively. The synthesis strategy involves a combination of self-assembly and the sol–gel technique. The synthesized nanostructures were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction. We investigated the nonlinear optical and optical limiting properties using an open-aperture Z-scan technique and fluence-dependent transmittance measurements. Compared to the pristine MWCNTs, those with Au-, TiO2-, and SiO2-coatings demonstrate superior, equivalent, and inferior nonlinear optical and optical limiting properties, respectively.