Effect of nano clay Laponite on stability of SHG active J-aggregate of a thiacyanine dye onto LB films

Abstract We have investigated the stability of Second Harmonic Generation (SHG) active J-aggregate of a thiacyanine dye N, N′-dioctadecylthiacyanine perchlorate (TC18) in Langmuir-Blodgett (LB) films in presence and absence of a synthetic clay mineral Laponite. Surface pressure vs area per molecule isotherm was taken to observe the monolayer stability and UV–vis absorption, deconvolution of the absorption spectra, Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) etc. have been employed to investigate the stability. It has been observed that pure TC18 J-aggregates degrades with irradiation of light, passage of time as well as post heat treatment of the TC18 J-aggregated LB films. However, in case of TC18 – Laponite hybrid films the decrease in J-aggregate is minimal. Interestingly, it was observed that the relative humidity plays a major role in the reconstruction of the J-aggregate in the treated film and thereby stabilizes the J-aggregate. Both pure TC18 and TC18 – Laponite hybrid LB monolayer films are found to be SHG active. In case of TC18 – Laponite hybrid film SHG signal shows better stability.