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Orientation of Organic Nanocrystals Grown in Sol–Gel Matrices under a High Magnetic Field
Author(s) -
Sanz N.,
Wang I.,
Zaccaro J.,
Beaug E.,
Baldeck P.L.,
Ibanez A.
Publication year - 2002
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/1616-3028(20020517)12:5<352::aid-adfm352>3.0.co;2-8
Subject(s) - materials science , orientation (vector space) , nanocrystal , magnetic field , field (mathematics) , nanotechnology , geometry , physics , quantum mechanics , mathematics , pure mathematics
In order to obtain new optical properties, such as quadratic nonlinear optical or electro‐optical properties, we have undertaken the orientation control of organic nanocrystals during their growth in the pore of sol–gel matrices by applying a high magnetic field, H , of 16 T. H favors the dye aggregation and improves the crystalline quality of nanocrystals by reducing the orientation freedom of molecules and clusters through their diamagnetic susceptibility. When H is not applied, the NPP ( N ‐(4‐nitrophenyl)‐( L )‐prolinol) nanocrystals generate a weak second harmonic generation (SHG) intensity due to self‐oriented domains of nanocrystals induced by dipole–dipole interactions. In the case of 3‐methyl‐4‐nitropyridine‐1‐oxide (POM), which exhibits a very weak dipolar moment, no SHG signal can be detected. When H is applied, the SHG intensity of NPP nanocrystals increases significantly due to the reduction of their orientational freedom and the increase of dipole–dipole interactions, thus improving the formation of oriented domains of nanocrystals.