Layer-by-layer self-assembled multilayer films of sulfonated-β-cyclodextrin and its reversible adsorption of methyl orange

Multilayer film based on photosensitive p-diphenyl diazonium salt (biPh-N²⁺) and sulfonated-β-cyclodextrin (S-β-CD) were fabricated by layer-by-layer self-assembly. The ionic bonds formed between diazonium salt and sulfonic acid ion in the multilayer film converted to covalent bonds and formed stable ultra-thin film when the diazonium groups decomposed under UV light irradiation. Meanwhile, the concentration of S-β-CD aqueous solution can influence the self-assembled multilayer films, while the pH value (pH=3∼9) had little effect on the self-assembled process except the strong alkaline solution (pH=11). Moreover, based on the electrostatic interactions of S-β-CD and MO to form a host-guest complexation, the multilayer film of (biPh-N²⁺/S-β-CD)₁₂ can absorb methyl orange (MO), and which can release reversibly in ethanol.