Studies On Design,fabrication And Application Of Smart Luminescent Materials Based On Upconversion Nanoparticels

Rare-earth elements whose luminescence originates from f-f electron transitions in the 4fn shell can act as an ideal luminous center;thus they often possess many optical and magnetic properties.For instance,the emission wavelengths are minimally disturbed by the ligand field and surrounding matrix,resulting in sharp line-like emission bands.Second,the emissions cover a wide range from ultraviolet to visible.Third,the lifetimes are relatively longer than other organic dyes.Among various luminescent materials that based on rare-earth elements,the upconversion nanoparticels(UCNPs)as a kind of specific nanomaterials have gained more attention and have been ultilized in many fields such as photoelectric materials,fluorescent labeling,detection of metal ions,drug delivery,bioimaging and cancer therapy.Given that UCNPs can convert the near-infrared irradiation(NIR)to short-wavelength emissions through two-photon or multi-photon process,they possess many advantages compared with organic dyes and quantum dots.Firstly,the excitation wavelength locates at NIR region,which can not only avoid the background interference but also have a deep tissue penetration as well as a little damage to normal cells.Secondly,large anti-Stokes shifts,no photobleaching,low toxicity and stable properties.Thirdly,the emission wavelength can overlap from the ultraviolet to visible light region according to the different host/activator combinations,the amount of doped lanthanide ions,the controlled crystallite size,phase,and associated defect state,thus benefitting other materials(e.g.,Au NPs,carbon dots,fluorescence dyes,photosensitizers,graphene,and graphene oxide)to absorb these emissions and make use of the fluorescence resonance energy transfer(FRET)process.However,reports about the self-assembly of UCNPs and the fabrication of multifunctional materials based on UCNPs are few.Base on this,in our work,we mainly focus on the designing,fabrication and applications in cancer therpy of these smart nanomaterials that synthesized based on UCNPs.The results demonstrate that these multifunctional materials can be used in biological system.The dissertation is mainly divided into following three chapters:Chapter 1: A brief introduction of the concept and application of upconversion nanoparticles and the fabricated nanomaterials based on upconversion nanoparticles.Chapter 2: Self-Assembled Upconversion Nanoparticle Clusters for NIR-controlled Drug Release and Synergistic TherapyThe present study reports the fabrication of three-dimensional(3D)upconversion nanoclusters(EBSUCNPs)obtained via an emulsion-based bottom-up self-assembly of NaGdF4:Yb/Er@NaGd F4 nanoparticles(UCNPs).Then EBSUCNPs were coated with a thin mesoporous amino-functionalized Si O2 shell and further conjugated with the gold nanoparticles to give the novel EBSUCNPs@Si O2@Au material.Finally,EBSUCNPs@Si O2@Au was applied as a biocompatible and efficient drug carrier for doxorubicin(DOX),thus giving rise to a multifunctional EBSUCNPs@Si O2-DOX@Au nanocomposite.Interestingly,when under NIR irradiation,a rapid DOX release was achieved owing to the thermal effect of the Au NPs after absorbing the green light from the upconversion nanoclusters based on FRET effect.Thus,a near infrared(NIR)-controlled “on-off” pattern of drug release behavior can be achieved.Moreover,compared with a single therapy method,the assembled nanocomposites exhibit a good synergistic therapy against cancer cells that combines chemotherapy with photothermal therapy.Therefore,this novel multifunctional 3D cluster architecture can be used in biomedical field after modification and may pave a new way in other application areas of UCNPs clusters.Chapter 3: Core-Shell Metal-Organic Framework Based Smart Nanocomposite for Efficient NIR/H2O2-Triggered Photodynamic TherapyFabrication of nanomaterials usually possesses multifunctional properties coming from the respective components and has presented an extensive trend in many fields of applications.In our work,a smart nanoreactor UCNPs/MB@ZIF-8 has been successfully synthesized by co-encapsulation of UCNPs and MB in ZIF-8 by one-pot process.After modification with polyvinylpyrrolidone and(3-aminopropyl)triethoxysilane,catalase was covalently grafted to give UCNPs/MB@ZIF-8@catalase.This nanocomposite was ultilized for efficient photodynamic therapy(PDT)against hypoxic tumours.ZIF-8 here play three roles: act as a nanocontainer to protect the photosensitizer MB;provide a stable environment for the efficient photophysical process between UCNPs and MB;adsorb oxygen molecules produced by the catalysis of hydrogen peroxide(H2O2).In conclusion,our work not only provides an encouraging alternative to expand the application of ZIF-8,but also can improve the existing drawbacks in PDT by combining the advantages of ZIF-8 and UCNPs/MB by one-pot encapsulated process.