Controllable Synthesis,Properties,and Biological Application Of Multi-functional Rare-earth Fluoride/Bi₂S₃ Nanomaterials

Inrecentyears,rare-earthupconversionluminescentnanomaterials served as new fluorescent nanoprobes have achieved great attention.Upconversion nanomaterials possess sharp emission lines,low toxicity,long luminescence lifetime,high chemical and optical stability characteristic due to the unique UC luminescent mechanism“anti-Stokes”.Compared with visible emission,near-infrared（NIR）emission has lots of advantages,such as no photodamage to living organisms,deeper light-penetration depth,lower background fluorescence,higher imaging sensitivity,etc.Therefore,upconversion nanomaterials with NIR-to-NIR emission are more suitable for bioimaging nanoprobes.However,although optical imaging based on upconversion namomaterials could provide tissues even cellular information with high sensitivity,the penetration depth and spatial resolution are limited.Fortunately,computed tomography（CT）and magnetic resonance（MR）imaging possess deeper light-penetration depth and high spatial resolution feature,respectively.Thus,developing nanostructure integrating optical,CT and MRI imaging in a nanoplatform could improve accuracy and precision of disease diagnosis and even tumor detection.In addition,photothermal therapy（PTT）as a minimally invasive therapeutic methodology,compared with chemotherapies,radiotherapies and surgery,PTT has advantages of rapid,efficiency,minimally invasive and small side effects in killing cancer.Therefore,this paper is aimed at constructing controllable phase and morphology of multi-functional rare-earth fluoride for multi-modal imaging and tumor detection;constructing hydrophilic Bi₂S₃ nanomaterials served as photothermal agents to treat cancer.The main research contents are as following:（1）Mn²⁺/Gd³⁺doped optical/magnetic bifunction NaYbF₄upconversion nanomaterials were successfully synthesized via a hydrothermal route.The results revealed that the phase and morphology of NaYbF₄ upconversion nanomaterials could be controlled by doping Gd³⁺.And high concentration of Gd³⁺favors the formation of pure hexagonal phase and small-sized nanocrystals.Doping Gd³⁺into this host can introduce an additional paramagnetic property,leading to form optical/magnetic bifunction nanocrystals.Moreover,based on upconversion emission spectrum,these upconversion nanomaterials present high-performance NIR-to-NIR emission.Thus,these optical/magnetic bifunction NaYb F₄ upconversion nanomaterials with excellent NIR-to-NIR emission can be used as nanoprobes for multi-modal imaging,providing a new way for preparing multi-modal imaging nanoprobes.（2）A HCl-treated route was performed to covert the hydrophobic NaYbF₄ nanocrystals to hydriphilc ones.The results of in vivo upconversion optical bioimaging indicated that Mn²⁺/Gd³⁺doped Na YbF₄upconversion nanomaterials can be served as optimal nanoprobes.The results of in vivo real-time tracking based on NaYbF₄:Tm³⁺/Gd³⁺upconversion nanomaterials revealed the nanocrystals were mainly accumulated in liver and spleen.And,the main excretion mechanism of our designed nanocrystals in vivo is demonstrated.Additionally,NaYbF₄:Tm³⁺/Gd³⁺upconversion nanomaterials can be effectively applied for small tumor（as small as 5 mm in diameter）detection by optical/magnetic resonance imaging.Therefore,optical/magnetic bifunction NaYbF₄upconversion nanomaterials with high-performance NIR-to-NIR emission pave the way for high-sensitive disease diagnosis and small malignant tumor detection.（3）Hydrophilic Bi₂S₃ nanomaterials were synthesized by a one-pot hydrothermal method.The photothermal conversion efficiency of Bi₂S₃nanocrystals were studied under 808 nm laser excitation.The results indicated that Bi₂S₃ nanocrystals possessed high photothermal conversion efficiency and could be used as photothermal agents for cancer treatment.Therefore,the synthesized Bi₂S₃ nanocrystals as photothermal agents have potential application for cancer therapy.