Rare Earth Organic Matter/Polymer Composite Fiber Fluorescence Properties Sensitized By Noble Metal

Due to the specific "antenna effect," rare-earth (RE) complexes with a wide range of excitation wavelengths, high fluorescence intensity and purity, high quantum efficiency (QE) have been applied in biomedical field like fluorescence probes, immunoassays, and photodynamic therapy of cancer etc. The electrospinning device is simple and low cost, and that the electrostatic spinning fibers are with controllable shape, small diameter, large surface area, good mechanical properties and high porosity. RE organic matter/polymer composite fibers prepared by electrospinning not only have excellent fluorescence properties, but also have good processability, heat stability and mechanical properties. The localized surface plasmon resonance (LSPR) effect of the noble metal nanoparticles can effectively enhance the fluorescence properties of the RE. In this paper, electrospinning was adopted to introduce noble metal nanoparticles and RE organic matter, to prepare the noble metal sensitized RE organic mater/polymer composite fibers. Different structures, uniform and stable RE organic matter fluorescence reinforcing fibers were obtained by the design of the electrostatic spinning nozzle, and research on the noble metal nanoparticles fluorescence enhancement effect on the rare earth organic matter, deeply study the fluorescence enhancement mechanism. The main contents are as follows:(1) The uniaxial electrostatic spinning apparatus was adopted to introduce silver nanoparticles (Ag-NPs) and RE organic matter Tb(acac)3phen into poly-L-lactic acid (PLLA) to prepare Ag-NPs /Tb(acac)3phen/PLLA fluorescence enhanced fibers. The research was to explore the best preparation process, in order to prepare better shaping and uniformly dispersed nanofibers. The molar ratio of Ag-NPs and Tb(acac)3phen was changed to research the fluorescence enhancement effect and reinforcing mechanism of Ag-NPs. The results showed that the fiber morphology is good, having a diameter of 200-550 nm, Tb(acac)3phen uniformly dispersed in the PLLA fibers. The addition of Ag-NPs result in the change of the chemical environment of Tb3+ in the fibers. The localized surface plasmon resonance (LSPR) effect of Ag-NPs enhanced the electromagnetic field around, so as to enhance the radiative decay rate of the neighboring Tb(acac)3phen, bringing about the reinforced fluorescence intensity of Ag-NPs/Tb(acac)3phen/PLLA fibers. When the molar ratio of Ag/Tb in the composite fiber is less than 4, the addition of Ag-NPs increase the quantum efficiency and the fluorescence lifetime of Tb3+ in the fiber.(2) The coaxial electrospinning device was adopted and double structure with isolation of Ag-NPs and Tb(acac)3phen was designed, bio-based polyvinylpyrrolidone (PVP) and PLLA spinning substrate was selected to prepare Tb(acac)3phen/PLLA//Ag-NPs/PVP core-sheath fluorescence enhanced fibers. The effect of the molar ratio of Ag-NPs and Tb(acac)3phen, the positions of inner and outer in the fibers on fluorescence properties of Tb(acac)3phen was researched, and the fluorescence enhancement mechanism of LSPR effect of Ag-NPs was studied in-depth. The results showed that the nanofibers produced significant core-sheath structure, with an outer diameter of 580 nm and an inner diameter of 270 nm. Tb(acac)3phen and Ag-NPs uniformly dispersed in the fibrous layer. Based on the LSPR effect of Ag-NPs, compared with the core-sheath nanofibers without Ag-NPs the fluorescence intensity nanofibers increased by 69%, quantum efficiency increased by 53% and fluorescence lifetime extended by 4% at molar ratio of Ag/Tb=1.(3) Coaxial electrospinning apparatus was adopted and the reduced nano gold (Au-NPs) was used to prepare Tb(acac)3phen/PLLA//Au-NPs/PVP core-sheath fluorescence enhanced fibers, to explore the best preparation process. The effect of different particle size of Au-NPs and the molar ratio with Tb(acac)3phen on the Tb(acac)3phen fluorescence properties was studied. The results showed that, the morphology of the Au-NPs was gotten with the reduction temperature of 60 and 80℃; the particle size substantially did not change within 2min of the reduction time, and with prolonged stirring time, Au-NPs particle size increases; The morphology of Au-NPs was better corresponding to a molar ratio of Au/Tb=2. With the addition of Au-NPs and the increase of the contents,the fiber diameter decreases. TEM showed a significant fiber sheath structure, and that Au-NPs and Tb(acac)3phen uniformly dispersed in the sheath and core of the fibers. Fluorescence spectra show that when the particle size of Au-NPs with diameter of about 65 nm, the fluorescence enhancement of Tb(acac) 3phen is the strongest. The effect of the fluorescence enhancement of Tb(acac)3phen/PLLA//Au-NPs/PVP core-sheath nanofibers appears the strongest at the molar ratio of Au/Tb= 4:1.