Cross-linked multilayer films deposited onto silica microparticles with tunable selectivity for anionic dyes

Cross-linked multilayer thin films assembled using weak polyelectrolytes with specific functional groups are useful materials in solid phase extraction techniques. Herein, we report a facile strategy to modify silica microparticle surfaces for the separation of two anionic dyes [Congo red (CR) and Bromocresol green (BCG)]. Different multilayer films, consisting of poly(ethyleneimine) (PEI) and poly(vinyl amine) (PVAm), as weak polycations, and poly(acrylic acid) (PAA), as a weak polyanion, were deposited onto silica using a layer-by-layer technique. The amount of anionic dyes sorbed onto the composite surface depended on the nature of polycation, deposition conditions, number of polycation layers, cross-linker concentration and on the nature of dyes. The degree of crosslinking by glutaraldehyde (GA) of the composite microparticles strongly influenced the extraction of PAA chains from multilayer during strong basic treatment and subsequently, the sorbed amount of dye and selective desorption capacity of composite. Daisogel//(PEI/PAA)4.5 cross-linked with 1.00% GA, can be used succesfully as a solid support in sorption and selective desorption of two anionic dyes (BCG and CR) only by pH tuning.

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