
TY  - JOUR
A1  - Ashwell, Geoffrey J. 
A1  - Williamson, Patricia C. 
A1  - Bahra, Gurmit S. 
A1  - Brown, Christopher R. 
T1  - 2,4-Bis[4-(dihexadecylamino)-2-hydroxyphenyl]-squaraine: Second-Harmonic Generation from Langmuir&#8211;Blodgett Monolayers of a Centro-symmetric Dye in which the Chromophores are Isolated from the Substrate
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1998
VL  - 52
IS  - 1
SP  - 37
EP  - 42
KW  - 
UR  - https://doi.org/10.1071/C98114 
N2  - 2,4-Bis&#91;4-(dihexadecylamino)-2-hydroxyphenyl&#93;squaraine is vertically oriented in the Langmuir&#8211;Blodgett film and the chromophore layer is separated from the glass substrate by the hydrophobic dihexadecylamino groups. The Langmuir&#8211;Blodgett monolayer exhibits moderately strong second-harmonic generation (SHG) with an effective susceptibility of c. 10 pm V-1 at 1064 nm and an intensity, relative to the mean SHG from films of the extensively studied hemicyanine dye (E)-4-&#91;2-(4-dimethylaminophenyl)ethenyl&#93;-N-docosylpyridinium bromide, of c. 0&#183;3. The SHG cannot arise from the polarization of the dye by the underlying substrate because the conjugated donor-(acceptor)-donor moiety is separated by a 2 nm thick hydrophobic barrier. Instead, the non-linear optical behaviour is attributed to a non-centrosymmetric aggregate structure. 
ER  -

