title: Asymmetric dyes align inside carbon nanotubes to yield a large nonlinear optical response.
abstract: Asymmetric dye molecules have unusual optical and electronic properties. For instance, they show a strong second-order nonlinear optical (NLO) response that has attracted great interest for potential applications in electro-optic modulators for optical telecommunications and in wavelength conversion of lasers. However, the strong Coulombic interaction between the large dipole moments of these molecules favours a pairwise antiparallel alignment that cancels out the NLO response when incorporated into bulk materials. Here, we show that by including an elongated dipolar dye (p,p'-dimethylaminonitrostilbene, DANS, a prototypical asymmetric dye with a strong NLO response) inside single-walled carbon nanotubes (SWCNTs), an ideal head-to-tail alignment in which all electric dipoles point in the same sense is naturally created. We have applied this concept to synthesize solution-processible DANS-filled SWCNTs that show an extremely large total dipole moment and static hyperpolarizability (β0 = 9,800 × 10(-30) e.s.u.), resulting from the coherent alignment of arrays of ∼70 DANS molecules.
authors: Physics Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Sofie
authors: S
authors: Cambré
authors: Physics Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Jochen
authors: J
authors: Campo
authors: Physics Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Charlie
authors: C
authors: Beirnaert
authors: Physics Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Christof
authors: C
authors: Verlackt
authors: Laboratory of Adsorption and Catalysis, Chemistry Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Pegie
authors: P
authors: Cool
authors: Physics Department, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium.
authors: Wim
authors: 0000000235090945
authors: W
authors: Wenseleers