Interfacial interactions of hard polyelectrolyte-stabilized luminescent colloids with substrates

• Tb(III) complexes at molecular and colloidal organization levels are compared.
• Interfacial complex formation with substrates differs from that in solution.
• Precipitated Tb(III) complexes form hard templates of polyelectrolyte-coated colloids.
• The colloids exhibit high stability of luminescence at pH 3–9.
• Luminescent response of Tb(III) colloids on substrates results from interfacial complex formation.

The present work introduces an origin of sensing function of polyelectrolyte-coated colloids based on Tb(III) complexes with calix[4]resorcinarene cavitand bearing four 1,3-diketone groups at the upper rim. The Tb(III)-centered luminescence of the colloids remains unchanged at pH 3–9, although the Tb(III) complexes are highly pH-dependent in DMF solutions. Both colloidal and luminescent properties of the colloids are stable within one month at least, which reveals stability of complex-based hard nanotemplates and soft polyelectrolyte deposition. The chelating substrates (catechol, tetracycline and fluoroquinolone derivatives) induce quick and reproducible luminescent response of the complex-based colloids without any detectable changes of their colloidal properties. The ternary complex formation at the interface of the colloids is the reason for their luminescent response on the substrates in aqueous solutions. Both the insolubility of the Tb(III)-containing cores and the shielding and/or buffer effect of the polyelectrolyte coating affect the interfacial complex formation, which results in more selective luminescent response of the colloids on the tetracycline and fluoroquinolone antibiotics in comparison with the complexes in solutions.

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