Effects of colloidal SiO2 and cyclodextrins on the aggregation of dyes in aqueous solutions

Phyllis Dan, Itamar Willner*, Nagaraj S. Dixit, Raymond A. Mackay

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Scopus citations

Abstract

Aggregation of two positively charged dyes, Methylene Blue, MB+ (1), and pinacyanol chloride, PC+, (2) is induced in aqueous SiO 2 colloids. In colloidal SiO2, MB+ aggregates into the dimeric form, and PC+ is aggregated into H-assemblies. The aggregation processes are a result of high local dye concentrations in the vicinity of the colloid owing to binding of the positively charged dyes to the negatively charged colloidal interface. De-aggregation of thionin, (3), is accomplished in water by the addition of cyclohexaamylose, α-CD, and cyclohepta-amylose, β-CD. Monomeric thionin binds to α-CD and β-CD (Kass. = 6.67 x 1O2 M-1 and 1.78 x 103 M-1, respectively). Conversion of thionin dimer into the monomeric form, upon addition of α-CD or β-CD, is attributed to association of the monomeric form to the hydrophobic cavity of CD. This conversion is accompanied by changes in the absorption and fluorescence spectra of the dye.

Original languageEnglish
Pages (from-to)455-459
Number of pages5
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number3
DOIs
StatePublished - 1984

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