Design, Preparation And Properties Of Phosphorescent Materials With Dual Model NIR Long Persistent Phosphorescence

Due to the unique mechanism of photoelectron storage and release, long persistent phosphors(LPPs) play a pivotal role in daily life, and areas of photochemistry, photonics and materials science etc. LPPs have been considered to be the most prominent candidates for the applications in in vivo bio-imaging, since their emission lifetime is sufficiently long to permit late time-gated imaging. In recent years, the chemical compositions, synthetic methods and characterizations of the LPPs have achieved great developments. However, in the field of functional application, there are still some unavoidable problems:(1) almost all the LPPs suffer from a dramatic decrease in luminescence intensity after incorporation into the tissue, which limits the application of the persistent luminescent materials on bio-imaging;(2) the bio-application of the LPPs mainly focus in bio-imaging, it is necessary to develop multifunctional LPPs, to set up an advanced imaging-guided therapy system.To solve these two problems, we propose dual mode(multi-functional) NIR long persistent phosphors. By adding proper ions into the LPPs, we effectively fabricate dual mode(multi-functional) NIR long persistent phosphors, improved the performance of the LPPs. The research results in the dissertation can be summarized as follows:1. We design and successfully fabricate an effective bifunctional LaAlO3: Mn4+, Tm3+, Yb3+ phosphor which exhibits interesting characteristics of near-infrared long persistent phosphorescence(730 nm) and NIR-to-NIR up-conversion luminescence(980 â†' 800 nm). The LaAlO3: Mn4+, Tm3+, Yb3+ phosphor exhibits long persistent luminescence at 730 nm due to the incorporation of Mn4+. The up-conversion spectra show that the LaAlO3: Mn4+, Tm3+, Yb3+ exhibits NIR emission at 800 nm under the excitation of 980 nm laser, and its luminescent intensity changes with the power of laser. The addition of Tm3+ and Yb3+ is beneficial to improve the persistent duration due to the increase of deep trap content.2. We design and successfully fabricate an effective bifunctional La3Ga5GeO14: Cr3+, Nd3+(LGGCN) phosphor which exhibits interesting characteristics of near-infrared long persistent phosphorescence and NIR-to-NIR Stokes luminescence. The LGGCN exhibits long persistent luminescence at 700 nm due to the incorporation of Cr3+. Notably, the results of thermo-luminescence curves and electron spin resonance spectra show that the addition of Nd3+ is beneficial to improve the persistent duration due to the increase of deep trap content. Meanwhile, LGGCN has NIR emission under the 808 nm excitation, taking the advantage of the appropriate energy level characteristic of Nd3+. Moreover, the NIR-to-NIR Stokes luminescence shows high reproducibility and stability for repetitions.3. We design and successfully fabricate an effective multi-modal long persistent phosphor Zn3Ga2SnO8: Cr3+, Gd3+, Nd3+ with NIR long persistent phosphorescence, magnetism and photo-thermal effect. Zn3Ga2SnO8: Cr3+, Gd3+, Nd3+ exhibits long persistent luminescence at 700 nm due to the 2Eâ†' 4A2 transition of octahedral coordinated trivalent chromium. The unique seven unpaired electrons configuration of Gd3+ ions gives the materials contained these ions possibilities to be powerful magnetic media. Meanwhile, Nd3+ ions can strongly absorb the energy of 808 nm laser and convert the absorbed energy to localized heat for the photo-thermal ablation of tumor cells.These kind of dual mode(multi-functional) NIR long persistent phosphors open a new perspective of advanced optical imaging with high resolution and weak light disturbance for factually assessing the structural and functional processes in cells, tissues and other complex systems. Moreover, it is expected to set up an advanced imaging-guided therapy system featuring a high resolution for bio-imaging and low side effect for the photo-thermal ablation of tumors.