Preparation And Performance Study Of Photochromic Nanomaterials And Photochromic Fluorescent Materialsbased On Naphthopyran

Naphthopyrans(NPs) as an important photochromic system is well known due to breadth of generated color, remarkable photoresponse, good thermal reversibility and resistance to photochemical fatigue and fine control over fading kinetics. These optical properties made NPs have potential advantages in the commercial application such as optical data storage, molecular switches and light-actuated nanovalves.In this thesis, we designed and synthesized a series of naphthopyran derivatives, and fabricated electrospun nanofiber mats and chemosensor based on naphthopyrans. In addition, the solution-dependence and piezochromic performance were studied. The structural properties of NPs were characterized by 1H NMR, MS, IR and crystal structure. Light-responsive properties of the NPs were characterized by UV-Vis and Fluorescence Spectra. The main contents of this dissertation are as following:1. High stable merocyanines of naphthopyrans based on polyvinylpyrrolidone(PVP) nanofibers had been developed by electrospinning the mixtures of PVP and naphthopyran derivatives. The surface morphology of nanofibers was characterized by scanning electron microscopy(SEM). The results indicate the electrospun fibers were oriented randomly and disorderly. The UV-Vis absorption spectra displayed great photochromic performance in the polymeric fibers, solution and film. And polymeric fibers containing naphthopyrans presented high-degree stable merocyanine forms. The internal features of the electrospun fibers were characterized by Fourier transform infrared spectroscopy(FT-IR). The one-dimensional structure of fiber and the hydrogen bonding between PVP and MC structures of naphthopyran were responsible for the high-degree stability. The absorption intensities of the highest stable MC form retained 77% compared with the initial intensity after fading of three days.2. A novel naphthopyran derivative bearing a rhodamine 6G unit as a chemosensor(R6GNP) has been designed and synthesized successfully and characterized by single crystal X-ray diffraction, nuclear magnetic resonance and mass spectrometry. The light-responsive properties of R6 GNP were characterized by UV-Vis and Fluorescence spectra. The absorption spectra exhibited excellent phtochromism with reversibly color change upon alternating ultraviolet irradiation and thermal bleaching. The results of UV-Vis and fluorescence spectra indicated R6 GNP was sensitive to common trivalent metal ions, such as Fe3+, Cr3+, Ga3+, In3+ and Al3+. Furthermore, optical and colorimetric sensing properties of R6 GNP for C u2+ were investigated by the naked eye and UV-Vis absorption spectra under the UV light. The system provided potential applications in fluorescence sensor, photoprinting, as well as in UV strength sensors for “naked eye” detection of UV radiation pollution.3. We prepared a new naphthopyran-carbazole dye(Cz NP) via direct combination of NP and carbazole as fluorescent moiety and discussed the crystal structure and optical properties. The photochromic properties of Cz NP in different solutions were investigated via UV-vis. The results suggested that Cz NP displayed remarkable photochromism with obvious spectra change in CH2 C l2, fast fading rate and good fatigue resistance. However, C z NP showed quite different photophysical behaviors in DMF and DMSO solution. The absorbance of the solutions increased to maximum then decreased under continuous UV irradiation. C z NP still had photochromic ability and occupied excellent fatigue resistance during the process. The results of fluorescence spectra proved that the fluorescent emission of the open- form C z NP can be enhanced by DMF under UV irradiation. The enhanced fluorescence can be quenched by the addition of triethylamine(TEA). The polarity of the solvent was the dominating factor to affect the fluorescence of C z NP under the UV light irradiation. C z NP also exhibited piezochromic performance under pressure.