SCHEDULED MAINTENANCE
Linear and non-linear optical properties of the different Langmuir–Blodgett phases of CnH2n+1–Q3CNQ
Abstract
(Z)-α-cyano-β-(N-hexadecylquinolin-4-ylium)-4-styryldicyanomethanide, C16H33–Q3CNQ, has two Langmuir–Blodgett (LB) phases that differ in thickness, tilt angle and second-order susceptibility. For phase I, I=2.2 nm layer–1, ϕ= 8° and χzzz(2)= 18O pm V–1 at 1.064 µm, whereas for phase II, I= 1.6 nm layer–1, ϕ= 24° and χzzz(2)= 100 pm V–1. The susceptibility of phase I is the highest so far reported for an LB multilayer; the structure is non-centrosymmetric (Z-type) and, as predicted by theory, the second-harmonic intensity varies as I2ω(N)=I2ω(1)N2 as N increases from 1 to 200 layers. In contrast, C10H21–Q3CNQ has a low susceptibility χzzz(2)= 6 pm V–1 and neutron reflectivity studies have indicated an antiparallel alignment of chromophores at the air/water interface.
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