J-aggregates in matrix stabilized two-dimensional azobenzene derivatives

A two-component film technique at the air–water interface has been used for fabricating matrix stabilized azobenzene J-aggregates. Langmuir monolayers of (E)-1-(3-chloro-4-(alkyloxy)phenyl)-2-phenyldiazene (C_nCD, n=8,10,12) have been prepared with stearic acid (STA) as the two-dimensional matrix. Miscibility studies at a molecular level, explored from the monolayer pressure–area isotherms revealed a phase separation of the C_nCD from the stearic acid matrix at a compression pressure of 10 mN/m. A 43-nm strong red shift in the 350 nm π–π^* absorption feature implied formation of highly ordered J-aggregates of C_nCDs in conformity with atomic force microscopy and micro-Raman spectral characteristics. While a one-component C_nCD failed to form a 2D monolayer, the STA supported C_nCD binary system crossed a mixed monolayer phase followed by compression, leading to the formation of matrix stabilized C_nCD J-aggregates.