Carbon based Y-type molecules for application in nonlinear optics

Inducing new nonlinear optical (NLO) properties while maintaining the thermal stability of carbon based nanomaterials broadens the application of carbon nanomaterials in opto-electronics. In the present work, polar azulene defects are introduced in Y-type carbon based molecules to induce polarity thus enhancing the second order NLO properties (for example, the static first hyperpolarizability of Y-type carbon based molecules with azulene defects reaches 4.18 × 10 −30 esu per heavy atom while that of p -nitroaniline is 2.97 × 10 −30 esu per heavy atom). The addition of an electron acceptor at the heptagon end modifies the π electron distribution of Y-type carbon based molecules and significantly enhances the static first hyperpolarizability from 1.73 × 10 −30 esu per heavy atom to 8.87 × 10 −30 esu per heavy atom, much larger than that of similarly synthesized NLO compounds. The cause of such enhancement by introduction of electron acceptors has been scrutinized. Introduction of polar azulenes and further functionalization significantly enhance the NLO properties of carbon based materials.