Hybrid silica–polyelectrolyte films as optical sensing materials for tetracycline antibiotics

• Silica–polyelectrolyte hybrid films modified with Eu(III) are worked out.
• Their morphology and sorption capacity are function of silica sol composition.
• Sensor element for detection of Tc based on Eu-sensitized fluorescence is obtained.
• The fluorescence doubled in the presence of citrate ion.

Optical sensor element for the determination of tetracycline (Tc) based on europium-sensitized luminescence of the SiO2–polyelectrolyte (PE)–Eu(III) hybrid film was worked out. The morphology of the hybrid films and their adsorption capacity towards Tc were function of PE and non-ionic surfactants content in silica coating solution. The presence of a mixture of Tween 20 and triblock copolymer Pluronic F-127 in a molar ratio Tween 20:Pluronic F-127 = 35:2.5 in silica sol resulted in the formation of films with uniform and ordered mesoporous structure. The use of polyvinyl- and polystyrene sulfonic acids during sol–gel synthesis greatly increased Tc adsorption within the hybrid films. SiO2–PE–Eu(III) films were used for Tc determination in milk with a linear response range in 0.6–10 μmol L−1and LOD 0.3 μmol L−1 of Tc. The sensitivity and selectivity of determination increased in the presence of citrate ions in solution.

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