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This communication reports the metachromasy or the changes in shapes and positions of the absorption spectra of an anionic cyanine dye merocyanine 540 abbreviated as MC540, in aqueous solutions and in LB films when electrostatically interacted with a well-known cationic surfactant cetyltrimethylammonium bromide abbreviated as CTAB. Critical Micellar Concentration of CTAB affected largely on the dissociation of MC540 molecular aggregates in the CTAB-MC540 complex LB films. Spectroscopic studies of these LB films showed only monomeric absorption band and intense fluorescence band. This complex LB film can act as efficient fluorescence probe for several biological systems. [ABSTRACT FROM AUTHOR]

Polymeric carbon nitride in graphitic form (g-C 3 N 4 ) is an emerging visible light active photocatalyst. In this work, phosphate-modified polymeric carbon nitride (PCN) was synthesized by thermal condensation of melamine in the presence of ammonium dihydrogen phosphate (ADP). The addition of PCN to methylene blue (MB) solution showed the color intensification. The hypsochromic shift in the absorption spectrum of MB is due to metachromasy, a phenomenon in which aggregation of dye molecules occurs over the surface of a material. The polymerization of melamine into carbon nitride and MB trimerization depend on the amount of ADP and nature of phosphate species, respectively. [ABSTRACT FROM AUTHOR]

This communication reports the effect of building matrices and nano clay platelets on the aggregation pattern of a water soluble cationic fluorescent dye Crystal Violet (CV) in Langmuir-Blodgett (LB) Films. When stearic acid (SA) was used as a building matrix, pressure induced changes in metachromasy was observed in the SA-CV complex LB films with a characteristic J-band formed at the longer wavelength side. On the other hand, clay incorporated hybrid LB films showed high degree of control over H-dimeric band. Isotherm characteristics, Brewster Angle Microscopic (BAM) images, UV–vis absorption and fluorescence characteristic studies were employed to investigate this result. [ABSTRACT FROM AUTHOR]