Fabrication And Properties Of Pyridine Pyrazolone And Composite Fluorescence Switch Materials

Organic photochromic fluorescent switch materials have attracted much attention for potential application in super-resolution fluorescence imaging,nondestructive reading and sensor due to the high sensitivity and selectivity.The pyrazolone photochromic materials are a kind of novel functional materials which exhibited good photochemical properties in the crystalline state but weak thermal stability,fatigue resistance and low emission contrast.Therefore,designing and synthesizing new fluorescent switch materials with high sensitivity,excellent thermal stability and fatigue resistance or composite fluorescent switch materials with high fluorescence contrast are becoming the key point to achieve the application in the field of information storage,fluorescent switches,biological imaging.Based on the previous research,a series of pyrazolone semicarbazones and thiosemicarbazones were designed and fabricated by introducing pyridine rings with different substituents.The photochemic properties and mechanisms of the compounds were studied.Several kinds of composite fluorescent switch materials were constructed by co-aggregating precipitation method,and the fluorescence switch capability were investigated in detail.The detail research are as follows:1.Nine pyrazolone photochromic compounds were synthesized by introducing three pyridine rings with different substituent groups at the 4-position of the pyrazolone ring.The structure and morphology of the target compounds were characterized by NMR,HRMS,X-ray diffraction.The photochemic properties of the compounds were investigated by UV-Vis absorption spectroscopy and fluorescence emission spectroscopy.It was found that seven compounds had photochromic properties,but with weak fluorescence control efficiency.Among them,the compound 1,3-diphenyl-4-(3-chloro-4-pyridylformyl)-5-hydroxypyrazole 4-phenyl-semicarbazoazone(DP3Cl4PyP-PSC)showed good reversibility and resistance fatigue.The compounds were coloring under ultraviolet light,then bleaching under visible irradiation or heating.The photochromic mechanism of the compounds were investigated by FTIR and X-ray photoelectron spectroscopy(XPS).The results showed that the photochromic behavior of the compounds was caused by the isomerization between enol-form and keto-form.The possible pathways of proton transfer for isomerization were deduced from DP3Cl4PyP-PSC single crystal structure,and the rationality was further explored by theoretical calculation.2.The DP3Cl4PyP-PSC nanoparticles were prepared by reprecipitation method.The effects of solvents and aging time on the morphology of aggregates were studied by scanning electron microscopy(SEM),and the photochemical properties of different morphologies were also redearched.It was found that the amorphous nano-sphere aggregates of DP3Cl4PyP-PSC did not have photochromic,while the crystalline one-dimensional nanorod aggregates showed similar photochromic properties to the original crystalline compounds,but weak fluorescence contrast as well.3.The photochromic composite fluorescent switch material of DP3Cl4PyP-PSC and different fluorescent dye system was prepared by co-aggregating precipitation method.Among them,the composite fluorescent switch material of DP3Cl4PyP-PSC/9,10-diphenylanthracene(DPA)has good fluorescence switch performance.The morphology and topography of the composite fluorescent switch material were characterized by XRD and SEM,the fluorescence modulation capability was researched by using fluorescence emission spectroscopy,and the optimal ratio of the composite fluorescent switch was determined at the same time.The results show that the best fluorescence modulation ratio of the composite material is about 79%,which is about 73% higher than that of the original compounds.The energy transfer mechanism was verified by fluorescence decay curves and the energy transfer efficiency was estimated at the optimum ratio.