Intercalation of nitroanilines into kaolinite and second harmonic generation

Kaolinite intercalates ortho- and para-nitroanilines (oNA and pNA) between the layers whereas meta-nitroaniline (mNA) is not intercalated, para-Nitroaniline takes a monolayer arrangement with the long axis inclined to the layers of kaolinite. oNA molecules also take a monolayer arrangement though the orientation is not well ordered. Kaolinite-pNA and -oNA intercalation compounds exhibit second harmonic generation, which is evaluated quantitatively by the second-harmonic wave generated with evanescent wave (SHEW) method. This indicates noncentrosymmetric arrangements of pNA and oNA, and such orientations are induced by the asymmetric environment of the interlayer region of kaolinite.