Aggregation behaviour of Methyl Violet 2B in Laponite clay aqueous dispersion and layer-by-layer electrostatic self-assembled film

This communication reports the aggregation behavior of cationic organic dye Methyl Violet 2B (abbreviated as MV2B) with laponite clay in solution and layer-by-layer (LbL) self-assembled film deposited onto solid substrate via electrostatic adsorption. H-type dimer or aggregates of dye molecules formed both in mixed solution and LbL film as confirmed by UV-Vis absorption spectroscopic study. Dye molecules also shows metachromassy in dye/clay mixed solution. Aggregation of dye in LbL film depends on layer number and laponite clay concentration. DLS and AFM topographical analysis supports the formation of dye aggregates in laponite/dye mixed solution and LbL film respectively. pH-dependent loading and release of dye from LbL film is also studied. Density functional theoretical (DFT) study reveals the optimized geometrical structure, HOMO and LUMO energy levels of cationic MV2B and possibility of interaction with laponite clay. FTIR study also comprehend the interaction between dye and clay towards the formation of LbL film.