Tianmei Zeng

PEGylated NaLuF4: Yb/Er upconversion nanophosphors for in vivo synergistic fluorescence/X-ray bioimaging and long-lasting, real-time tracking

Simultaneous in vivo luminescence and X-ray bioimaging in a tissue or animal integrates the advantages of each single-modal imaging technology, and will find widespread application in biological and clinical fields. However, synergistic dual-modal bioimaging that utilizes a new generation of upconversion nanoprobes is still limited. In addition, investigations concentrated on in vivo biodistribution of these nanoprobes may contribute to diagnosis and treatment, but long-term in vivo tracking based on these nanoprobes is rarely reported. In this work, water-soluble NaLuF4: Yb/Er nanophosphors were prepared through modified one-pot simultaneous synthesis and surface modification method. Owing to the outstanding upconverting emissions and large X-ray absorption coefficient/K-edge value of Lu and doped Yb ions, the obtained nanoprobes were successfully used as luminescent nanoprobes and X-ray contrast agents for in vivo synergistic upconversion luminescence and X-ray bioimaging. The in vivo biodistribution of these nanoprobes were observed, and the results based on long-term tracking reveal that the as-prepared nanoprobes first aggregated in the lung of the mouse, transferred to the liver, and finally moved to the spleen.

Multi-functional NaErF4:Yb nanorods: enhanced red upconversion emission, in vitro cell, in vivo X-ray, and T2-weighted magnetic resonance imaging

In this paper, multi-functional hexagonal phase NaErF4:Yb nanorods were synthesized by a facile hydrothermal method. The upconversion luminescence (UCL) intensity and red to green ratio of the multi-functional NaErF4 nanorods can be improved by Yb(3+) doping. More importantly, owing to the decreased distance of Er and Yb, the significant enhancement of red UCL can be obtained, which is different to the usual green UCL of Yb/Er doped NaYF4 host. In addition, the intensity of UCL is strongest when the Yb(3+)-doped concentration reached 30%. The in vitro cell imaging and localized UCL spectra taken from HeLa cells revealed that these NaErF4: 30% Yb(3+) nanorods are ideal nanoprobes with absence of autofluorescence for optical bioimaging. Moreover, these nanorods possess large X-ray absorption ions (Er(3+) and doped Yb(3+)), and were successfully used as contrast agents for in vivo X-ray bioimaging for the first time. In addition to the excellent UCL and X-ray absorption properties, these nanorods present significant paramagnetic properties and can be used as T2-weighted magnetic resonance imaging (MRI) agents. Therefore, these enhanced red UCL NaErF4 nanocrystals with excellent paramagnetic properties and X-ray absorption properties can be used as promising multi-modal nanoprobes for optical bioimaging, MRI, computed X-ray tomography (CT), and may have potential applications in bioseparation.

Urchin-like Ce/Tb co-doped GdPO4 hollow spheres for in vivo luminescence/X-ray bioimaging and drug delivery

In this paper, we report a self-sacrificing route for fabrication of the Ce/Tb co-doped GdPO4 hollow spheres under hydrothermal conditions using the Gd(OH)CO3:Ce/Tb precursor as a template and NH4H2PO4 as a phosphorus source. The X-ray diffraction (XRD) patterns show the amorphous crystal nature of the precursor and pure hexagonal phase of the hollow spheres. The microstructures of the as-prepared precursor and hollow spheres were characterized by transmission electron microscopy (TEM) and scanning TEM (STEM) assays. The results reveal the urchin-like morphology of the solid precursor and hollow spheres. Bright green emissions of the spheres have been detected using an ultraviolet (UV) lamp at 288 nm and the calculated CIE coordinates are (0.289, 0.491). The energy transfer mechanism of Ce and Tb ions in the GdPO4 host has been investigated. The quantum efficiency of the hollow spheres was measured to be 61% and the lifetime calculated as 6.94 ms. In addition, the magnetic mass susceptibilities and magnetization of the spheres are found to be 6.39 × 10-5 emu gOe-1 and 1.27 emu g-1 at 20 kOe, respectively. Owing to their excellent downshift luminescence properties, the as-prepared GdPO4:Ce/Tb hollow spheres have been successfully applied in in vivo luminescence and X-ray bioimaging for the first time. Moreover, three-dimensional (3D) in vivo X-ray bioimaging of the mouse can provide the accurate location from multiple directions. The high contrast ratio makes the spheres a promising X-ray contrast agent. Due to the hollow structure, these GdPO4:Ce/Tb hollow spheres were also used as drug delivery systems for doxorubicin (DOX) loading and release. The drug loading efficiency was measured to be 17% at a pH value of 7.4, and the pH-dependent drug release was studied. 47% of the loaded DOX was released within 10 h when pH = 5, while there was only 30% during the same time at pH = 7.4 and it took nearly 48 h to reach a comparable level. The different release nature gives these spheres a promising application in targeted therapy of tumors.

Sub-10 nm BaLaF5:Mn/Yb/Er nanoprobes for dual-modal synergistic in vivo upconversion luminescence and X-ray bioimaging

Small-sized BaLaF5:Mn/Yb/Er upconversion nanoparticles (UCNPs) were successfully synthesized for dual-modal X-ray and upconversion (UC) luminescence bioimaging by a simple solvothermal method. The size, shape, and UC luminescence intensity of the as-prepared UCNPs can be readily modified by changing the contents of Mn2+. The size of BaLaF5 UCNPs doped with Mn2+ decreased largely compared with Mn-free UCNPs. When increasing the content of Mn2+ from 5% to 20%, the size of UCNPs was gradually increased from 6.5 nm to 9.7 nm. The as-prepared BaLaF5 UCNPs doped with 20% Mn2+ present intense UC luminescence. The in vitro UC luminescence imaging of HeLa cells and localized spectra detected from HeLa cells and the background based on these BaLaF5:Mn/Yb/Er (20/20/2%) UCNPs indicate that this sample can serve as an ideal bioprobe with the absence of autofluorescence under the excitation of 980 nm laser. Moreover, an obvious UC signal was observed in in vivo UC bioimaging, demonstrating that these BaLaF5:Mn/Yb/Er (20/20/2%) UCNPs can also be used as bioprobes for whole body optical bioimaging. In addition, owing to the high X-ray mass absorption coefficients of Ba2+, La3+ and the doped Yb3+, the simultaneous X-ray and UC in vivo bioimaging of a nude mouse further demonstrate that the as-prepared UCNPs can be successfully used as dual-modal bioprobes. Ex vivo UC bioimaging revealed that these UCNPs gathered at the lung of a mouse at the initial time, demonstrating that this sample was suitable for the detection of the lung diseases. In addition, the cytotoxicity test showed that the UCNPs possessed little toxicity. Therefore, the small-sized BaLaF5:Yb/Er/Mn UCNPs are ideal nanoprobes for dual-modal UC luminescence/X-ray bioimaging with non-autofluorescence, and enhanced detection of the lung diseases.

Controllable multicolor output, white luminescence and cathodoluminescence properties of high quality NaCeF4:Ln3+ (Ln3+ = Eu3+, Dy3+, Tb3+) nanorods

Herein, a series of hexagonal phase lanthanide (Ln3+, Ln3+ = Eu3+, Dy3+, Tb3+) doped NaCeF4 nanorods (NRs) with uniform morphology and monodispersity have been successfully synthesized via a typical hydrothermal method using oleic acid as the capping agent. The crystal phase and microstructure of the obtained NRs were analyzed by X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM). The down conversion (DC) luminescence properties and mechanisms of the as-prepared NaCeF4:Ln3+ NRs have been discussed in detail. The as-prepared samples show the characteristic f–f transition of Ln3+ (Ln3+ = Eu3+, Dy3+, Tb3+). The decay time and quantum yield of these obtained NRs are also studied. Moreover, tunable multicolor, especially white emissions, can be successfully achieved via varying the doping ions and doping concentration. By increasing the content of Eu3+, the emission colors vary from light green to white and finally to light red under the excitation of 395 nm. The calculated CIE coordinates of the obtained white emissions are (0.33, 0.31), which are very close to the standard white light located at (0.33, 0.33). This is the first time to demonstrate that white light emission is achieved via only singly-doping Eu3+ into the NaCeF4 system. In addition, the multicolor output changes from yellowish-green to yellow under the excitation at 261 nm, which was also obtained by only tuning the doped content of Dy3+ in the NaCeF4 host. As for Tb3+, bright yellowish green emissions were obtained under excitation at 261 nm. Moreover, the cathodoluminescence (CL) spectra demonstrate that these NRs can emerge as ideal nanophosphors under electron beam excitation. Therefore, the as-prepared NaCeF4:Ln3+ NRs with tunable multicolor output and bright white emissions might be applied in field-emission devices, multicolor displays and solid state lasers.

Synthesis and Downconversion Emission Property of : Nanosheets and Nanotubes

Ytterbium oxide (Yb2O3) nanocrystals with different Eu3+ (1%, 2%, 5%, and 10%) doped concentrations were synthesized by a facile hydrothermal method, subsequently by calcination at 700°C. The crystal phase, size, and morphology of prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the as-prepared Yb2O3 nanocrystals with sheet- and tube-like shape have cubic phase structure. The Eu3+ doped Yb2O3 nanocrystals were revealed to have good down conversion (DC) property and intensity of the DC luminescence can be modified by Eu3+ contents. In our experiment the 1% Eu3+ doped Yb2O3 nanocrystals showed the strongest DC luminescence among the obtained Yb2O3 nanocrystals.

Synthesis, Tunable Multicolor Output, and High Pure Red Upconversion Emission of Lanthanide-Doped Lu2O3 Nanosheets

Yb3+ and Ln3+ (Ln = Er, Ho) codoped Lu2O3 square nanocubic sheets were successfully synthesized via a facile hydrothermal method followed by a subsequent dehydration process. The crystal phase, morphology, and composition of hydroxide precursors and target oxides were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscope (EDS). Results present the as-prepared Lu2O3 crystallized in cubic phase, and the monodispersed square nanosheets were maintained both in hydroxide and oxides. Moreover, under 980 nm laser diode (LD) excitation, multicolor output from red to yellow was realized by codoped different lanthanide ions in Lu2O3. It is noteworthy that high pure strong red upconversion emission with red to green ratio of 443.3 of Er-containing nanocrystals was obtained, which is beneficial for in vivo optical bioimaging.