Monolayers and Langmuir–Blodgett films of luminescent 1,3,5-triazine derivatives containing naphthalene or anthracene chromophores

Monolayer behaviors and Langmuir–Blodgett (LB) films of three luminescent aryl triazines, 2,4,6-tri(naphthalen-1-yl)-1,3,5-triazine (TN1Ta), 2,4,6-tri(naphthalen-2-yl)-1,3,5-triazine (TN2Ta), and 2,4,6-tri(anthracen-9-yl)-1,3,5-triazine (TATa) have been investigated. Surface pressure-area isotherms indicated that pure aryl triazines were difficult to form stable monolayers, while their mixtures with arachidic acid (AA) could be stabilized at the air–water interface. The mixed LB films of triazine-AA were deposited on substrate surfaces and analyzed by using UV–vis and infrared absorption spectra, X-ray photoelectron spectra, as well as scanning electron microscopy. Morphologies of the LB films and molecular aggregates were closely dependent on the structure of triazines and the surface pressures of deposition. Under UV radiation, TN1Ta and TN2Ta emitted at 410–460 nm while TATa emitted at 500–510 nm, with the emission lifetime falling into the range of 0.29 to 10.8 ns. Compared with those in solutions, the emissions of aryl triazines were red shifted in the LB films, especially for the TN1Ta-AA and TN2Ta-AA, which was attributed to the closely packed arrangement for the molecules in the LB films.