Tunable optical limiting in silver nanoparticle-naphthophenanthridine hybrids

Incorporation of functional nanoparticles into liquid crystals has emerged as a promising approach to create liquid crystal nanocomposites with superior opto-electronic properties. The properties of self-assembled supramolecular structures change remarkably upon the dispersion of a minute amount of metal nanoparticles in them. The effect of dispersing alkyl thiol-functionalized silver nanoparticles (Ag NP) in Naphthophenanthridine discotic liquid crystals on the nonlinear optical (NLO) properties is discussed in this work. Discotic liquid crystals (DLC) are synthesized via N-annulation of hexabutoxytriphenylene-1-amine with heptanaldehyde through the Pictet–Spengler reaction. A uniform dispersion of about 1–3 wt% Ag NPs in the columnar matrix enhances the nonlinear optical absorption, when measured under excitation by nanosecond laser pulses at 532 nm. By changing the amount of Ag NP loading, the nonlinear response of the hybrid can be tuned. These results indicate that the Ag-DLC hybrids are potential candidates for applications in NLO devices such as tunable optical limiters.