
TY  - JOUR
A1  - Ashwell, G. J. 
A1  - Paxton, G. A. N. 
T1  - Multifunctional Properties of (<emph type="2">Z</emph>)-&#946;-(<emph type="2">N</emph>-Hexadecyl-4-quinolinium)-&#945;-cyano-4-styryldicyanomethanide: a Molecular Rectifier, Optically Non-Linear Dye, and Ammonia Sensor
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 2002
VL  - 55
IS  - 3
SP  - 199
EP  - 204
KW  - 
UR  - https://doi.org/10.1071/CH01182 
N2  - The zwitterionic dye, Z-&#946;-(N-hexadecyl-4-quinolinium)-&#945;-cyano-4-styryldicyanomethanide (C16H33-Q3CNQ), forms dimeric solution aggregates, which are probably centric, but adopt a non-centrosymmetric arrangement at the air/water interface. When spread from dilute solution, e.g. 3 &#215; 10-5 M in CH2Cl2, the resultant Langmuir-Blodgett (LB) films are purple, &#955;max 563 &#177; 3 nm. They have an optimum effective second-order non-linear optical susceptibility of 75 pm V-1 at 1.064 &#956;m and, when sandwiched between gold electrodes, exhibit asymmetric current-voltage curves, characteristic of molecular rectification. In contrast, when spread at slightly higher concentrations (e.g. 10-4 M), the resultant LB films are polymorphic and have absorption maxima at 563 and 670 nm, the latter being characteristic of the benzyl analogue (&#966;-CH2-Q3CNQ). Its films are turquoise, &#955;max 668 &#177; 3 nm, and both molecular rectification and second-harmonic generation are inhibited. Thus, the red-shifted charge-transfer band probably reflects an altered alignment whereby the molecules adopt a centric antiparallel arrangement within the monolayer. The zwitterionic films readily protonate, with bleaching, and may be used to sense ammonia at concentrations of ca. 1 ppm by monitoring changes in the surface plasmon resonance. 
ER  -

