Hybrid luminescent material based on an electrospinned polymer matrix with encapsulated AgInS2/ZnS quantum dots

Background and Objectives: Hybrid polymer materials containing luminescent nanoparticles are promising for creating, in particular, electroluminescent devices. Such materials are able to withstand significant mechanical deformations while maintaining high radiation conversion efficiency with both decreasing and increasing frequency. Among the extensive set of existing approaches for the production of hybrid polymer materials, the electrospinning method allows the use of a wide range of polymers, resulting in formation of disordered structure consisting of fine (hundreds of nanometers diameter) arbitrarily oriented fibers, which makes it possible to obtain a porous fibrous material with a large surface area. The electrospinning method is an effective tool for creating composite structures with nanoparticles encapsulated in polymer fibers that protect nanoparticles from environmental influences. The high porosity of nanofiber nonwovens allows them to be used as the basis for highly sensitive sensors for dangerous and toxic substances due to their large surface area. Materials and Methods: The pre-synthesized AgInS2/ZnS quantum dots were introduced into the spinning solution of polyacrylonitrile in dimethylformamide immediately before the electrospinning process. Quantum dots retained their luminescent properties and did not interact with the solvent. To carry out the electrospinning process, a high voltage (–53 kV) was applied between the grounded solution supply capillary and the collector using a stabilized power source. The sample spinning time was 30 minutes, and the feed rate of the spinning solution was 750 µl/h. The obtained hybrid luminescent material was experimentally studied using luminescence analysis. The effect of ciprofloxacin on the luminescent properties of the obtained material was studied by impregnating electroformed samples with aqueous solutions with different concentrations of the antibiotic. Results: It has been established that quantum dots are physically embedded in the polymer matrix, and not by chemical bonding. The presence of ciprofloxacin in the solution leads to quenching of the luminescence of quantum dots, but does not cause a shift in the luminescence maximum. This is significantly different from the interaction of quantum dots with ciprofloxacin directly in an aqueous solution, since in this case a bathochromic shift is observed. An explanation of quenching the luminescence of quantum dots based on the interaction of ciprofloxacin molecules with their shells is proposed. In course of AgInS2/ZnS quantum dots production, a coating of thioglycolic acid is applied to the surface of the dots to prevent aggregation in water. The protonated aminogroups of ciprofloxacin interact electrostatically with dissociated carboxylic groups of thioglycolic acid, which leads to a change in the quantum dots surface and causes quenching of AgInS2/ZnS luminescence. Conclusion: A hybrid luminescent material based on a non-woven nanofiber matrix with encapsulated luminescent AgInS2/ZnS quantum dots has been developed. The material can be useful as a sensor platform for the determination of bioactive substances. It is possible to confidently determine the fluoroquinolone antibiotic ciprofloxacin in aqueous solution up to its concentration of CM = 1 · 10–7 M by the developed material.