2,4-Bis[4-(dihexadecylamino)-2-hydroxyphenyl]-squaraine: Second-Harmonic Generation from Langmuir - Blodgett Monolayers of a Centro-symmetric Dye in which the Chromophores are Isolated from the Substrate

1999 ◽  
Vol 52 (1) ◽  
pp. 37 ◽  
Author(s):  
Geoffrey J. Ashwell ◽  
Patricia C. Williamson ◽  
Gurmit S. Bahra ◽  
Christopher R. Brown

2,4-Bis[4-(dihexadecylamino)-2-hydroxyphenyl]squaraine is vertically oriented in the Langmuir–Blodgett film and the chromophore layer is separated from the glass substrate by the hydrophobic dihexadecylamino groups. The Langmuir–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-[2-(4-dimethylaminophenyl)ethenyl]-N-docosylpyridinium bromide, of c. 0·3. 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.

1992 ◽  
Vol 96 (7) ◽  
pp. 2801-2804 ◽  
Author(s):  
Michael A. Carpenter ◽  
Craig S. Willand ◽  
Thomas L. Penner ◽  
David J. Williams ◽  
Shaul Mukamel

1994 ◽  
Vol 98 (48) ◽  
pp. 12459-12461 ◽  
Author(s):  
L. B. Gan ◽  
D. J. Zhou ◽  
C. P. Luo ◽  
C. H. Huang ◽  
T. K. Li ◽  
...  

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