Structure, photoactivity, and antimicrobial properties of phloxine B / poly(caprolactone) nanocomposite thin films

Many applications of polymeric materials require chemical surface treatments. One possibility is the formation of a thin nanocomposite layer without changes in the polymer matrix. In this work, poly(caprolactone) was prepared with a thin nanocomposite layer composed of organoclay and photoactive dye, phloxine B (PhB). The principle of modification was the fusion of a thin layer of organoclay with a polymer matrix by the intercalation of polymer chains into the organoclay layer. The surface properties and composition of the thin layer of the nanocomposite were described using electron microscopy, measurements of water contact angles, X-ray diffraction, as well as X-ray photoelectron, UV–vis, and infrared spectroscopies. These methods revealed the effectiveness of polymer intercalation, confirmed the hydrophobic properties of the layer, the thickness of the composite at the level of several μm, the surface composition, and homogeneous distribution of PhB. The main outcomes were photoactive and antimicrobial properties of the films. The effects of various factors such as surfactant and dye concentrations and presence of polymer on photophysical properties were evaluated. PhB retained luminescence in all prepared materials to be highest at the lowest dye concentration and gradually decreased with increasing dye concentration. This trend was also confirmed by measurements of time-resolved fluorescence and quantum yields. In terms of antimicrobial activity, only the composite with the highest concentration of PhB exhibited a significant reduction in S. aureus biofilm growth. A more significant reduction was achieved using green light irradiation (about 3% of the growth in the control). The influence of other factors and potential applications will be the subjects of further studies.