Fabrication and Photoluminescence of Hybrid Organized Molecular Films of a Series of Gemini Amphiphiles and Europium(III)-Containing Polyoxometalate

摘要

Organic/inorganic hybrid monolayers,consisting of an oval decatungstoeuropate (EuW_(10)) with photoluminescence and a series of gemini-type amphiphiles with various lengths of the flexible hydrophobic spacers,were formed through electrostatic interaction at the air/water interface.The ultrathin hybrid multilayer films could be fabricated through the horizontal transfer of the monolayers onto the solid substrates.The characteristic absorption band of EuWio in the UV spectra of the hybrid films showed a slight red shift in comparison with that in solution,indicating the ordered arrangement of EuW_(10) in the hybrid films.FT-IR spectra of the hybrid films presented characteristic bands of EuW_(10),indicating that the structure of the cluster was kept in the films.X-ray diffraction measurements of the films revealed that the well-defined layer structures were formed in these multilayer films and the EuW_(10) cluster ions were orientated with their short axis parallel to the film surface.Typical photoluminescence of the ~5D_0 -> ~7F_2 and ~5D_0 -> ~7F_1 transitions of EuW_(10) was observed in the hybrid films.Interestingly,the relative intensity of the two emission bands varied with the spacer length of the gemini amphiphiles in the films.A size matching between EuW_(10) and the gemini amphiphile with a hexamethylene spacer was observed,which showed the lowest ratio of the emission intensity of ~5D_0 -> ~7F_2 to that of ~5D_0->~7F_1.Circular nanoparticles were observed in the AFM images for all these hybrid films.In addition,the size of the formed nanoparticles showed a dependence on the spacer length.