| Upconversion materials doped with lanthanide elements in the host crystal lattice absorb long-wavelength excitation light and emit short-wavelength light as anti-stokes luminescence.In recent years,upconversion nanoparticles(UCNPs)have attracted the attention of many researchers in the fields of information display,optical equipment,response devices,biomedical and so on.Photonic crystals(PCs)are spatially periodic structures of materials with different dielectric constants and have bright structural colors.Optical coding materials based on upconversion nanoparticles and photonic crystals have broad application prospects in the field of optics due to their multiple response modes of upconversion fluorescence and structure colors.The construction of optical coding materials with various response characteristics is also a research topic in the field of functional materials.In the current research,the realization of multiple response modes is still a problem that needs to be solved in order to improve the luminescence intensity of upconversion nanoparticles.The unique structural color of photonic crystals can be combined with upconversion nanoparticles to broaden the applications in optical coding and response mode.At the same time,due to the optical properties of spiropyran molecules,the design ideas of upconversion composites will be expanded in the responsiveness and coding dimensions.In this study,from the perspective of the regulation upconversion nanoparticles on the optical properties,through a combination of different structure of photonic crystals structural color and spiropyran molecular response characteristics,we designed composites structure based on upconversion nanoparticles and photonic crystals,studied the optical regulation behavior and response modes,and explored the potential application of programmable information password,multiple response information display and multi-mode information coding.The main researchs are as follows:1.Construction and optical coding behaviors of multi-mode luminescent enhanced composites:We combined upconversion nanoparticles and photonic crystals to design the luminescence enhanced composites,and fabricated multimode optical coding patterns through utilizing the optical properties of both materials respectively.We prepared UCNPs with different luminescence and the composite materials can be quickly obtained by spin-coating the UCNPs on the surface of the PCs.Due to the Bragg reflection of the photonic band gaps,the upconversion luminescent enhancement effect was observed in the fluorescence spectra of the composites,indicating that the upconversion luminescence can be regulated by the photonic band gap.Through theoretical calculation,it is proved that PCs can enhance the emission of luminescent ions by non-resonant enhancement of the excitation source.We fabricated upconversion luminescent lattices based on the surface of the photonic crystals by dropping and endowed with the meaning of the Morse code so that it can have more information in different modes.In addition,the cipher table pattern was further obtained according to the structural color of the PCs and the luminescence of the UCNPs.The results reveal great potential applications in the field of optical display and multi-mode information coding.2.Construction of multicolor Janus microbeads optical arrays and research on magnetic-optical response characteristics:A facile method to fabricate Janus microbeads based on photonic crystals and upconversion nanoparticles was designed.The Janus microbeads can be reversed under magnetic response and generate upconversion fluorescence under near-infrared light.Three kinds of core-shell upconversion nanoparticles were prepared by the solvothermal method and were mixed with Fe3O4 nanoparticles and different sizes of p(StMMA-AA)colloidal spheres.The Janus microbeads are assembled according to the hydrophilic property of the mixture and the hydrophobic property of PDMS substrates.The upper parts of the Janus microbeads are photonic crystals assembled with colloidal spheres,and the other parts are Fe3O4.Meanwhile,UCNPs are distributed inside the Janus microbeads.Furthermore,the Janus microbeads were prepared into different lattice patterns using special templates.In the lattice patterns,the structural colors of Janus microbeads can be displayed and disappeared by magnetic field inversion,and under external NIR irradiation,Janus microbeads can generate upconversion fluorescence to achieve multiple color display.The Janus microbeads were also applied to both sides of the bank card,and various reading information methods were designed according to different response modes,which have important applications in pattern display,response materials,and information coding.3.Construction of spiropyran-modified upconversion nanocomposite and research on optical regulating behaviors:An efficient approach for achieving obvious fluorescence with tunable color via spiropyran-modified upconversion nanocomposite is reported.The surface of the upconversion nanoparticles was coated with silica shell,and then the silylated spiropyran molecules were grafted onto the surface of the shell.Spiropyran is introduced to produce red fluorescence under UV light.and in the NIR light,upconversion nanoparticles generate green fluorescence,so when the two light irradiation nanocomposites at the same time,the superposition of two independent fluorescence will produce yellow fluorescence observed by the eye.Besides,by adjusting the NIR excitation light power,the yellow fluorescence can be real-time dynamically regulated,and the regulation effect can be illustrated from the CIE chromaticity coordinate.The nanocomposite is configured into inks that can be printed or sprayed into diverse coded patterns which emitted various fluorescence under different lights like a chameleon.These patterns reveal the great potential of upconversion nanocomposite in programmable coding,and responsive nanomaterials. |
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