Chi Yao

Direct Imaging the Upconversion Nanocrystal Core/Shell Structure at the Subnanometer Level: Shell Thickness Dependence in Upconverting Optical Properties

Lanthanide-doped upconversion nanoparticles have shown considerable promise in solid-state lasers, three-dimensional flat-panel displays, and solar cells and especially biological labeling and imaging. It has been demonstrated extensively that the epitaxial coating of upconversion (UC) core crystals with a lattice-matched shell can passivate the core and enhance the overall upconversion emission intensity of the materials. However, there are few papers that report a precise link between the shell thickness of core/shell nanoparticles and their optical properties. This is mainly because rare earth fluoride upconversion core/shell structures have only been inferred from indirect measurements to date. Herein, a reproducible method to grow a hexagonal NaGdF(4) shell on NaYF(4):Yb,Er nanocrystals with monolayer control thickness is demonstrated for the first time. On the basis of the cryo-transmission electron microscopy, rigorous electron energy loss spectroscopy, and high-angle annular dark-field investigations on the core/shell structure under a low operation temperature (96 K), direct imaging the NaYF(4):Yb,Er@NaGdF(4) nanocrystal core/shell structure at the subnanometer level was realized for the first time. Furthermore, a strong linear link between the NaGdF(4) shell thickness and the optical response of the hexagonal NaYF(4):Yb,Er@NaGdF(4) core/shell nanocrystals has been established. During the epitaxial growth of the NaGdF(4) shell layer by layer, surface defects of the nanocrystals can be gradually passivated by the homogeneous shell deposition process, which results in the obvious enhancement in overall UC emission intensity and lifetime and is more resistant to quenching by water molecules.

Nd3+ Sensitized Up/Down Converting Dual-Mode Nanomaterials for Efficient In-vitro and In-vivo Bioimaging Excited at 800 nm

Core/shell1/shell2/shell3 structured NaGdF4:Nd/NaYF4/NaGdF4:Nd,Yb,Er/NaYF4 nanocrystals were well designed and synthesized, each of the parts assume respective role and work together to achieve dual-mode upconverting (UC) and downconverting (DC) luminescence upon the low heat effect 800-nm excitation. Nd3+, Yb3+, Er3+ tri-doped NaGdF4:Nd,Yb,Er UC layer [NIR (800 nm)-to-Visible (540 nm)] with a constitutional efficient 800 nm excitable property were achieved for the in-vitro bioimaging with low auto-fluorescence and photo-damage effects. Moreover, typical NIR (800 nm)-to-NIR (860–895 nm) DC luminescence of Nd3+ has also been realized with this designed nanostructure. Due to the low heat effect, high penetration depth of the excitation and the high efficiency of the DC luminescence, the in-vivo high contrast DC imaging of a whole body nude mouse was achieved. We believe that such dual-mode luminescence NCs will open the door to engineering the excitation and emission wavelengths of NCs and will provide a new tool for a wide variety of applications in the fields of bioanalysis and biomedical.

NIR‐Triggered Release of Caged Nitric Oxide using Upconverting Nanostructured Materials

In this manuscript, a novel strategy for the therapeutic delivery of nitric oxide to physiological targets is described. Nitric oxide (NO) is a key vasodilator in mammalian cardiovascular systems and has been shown to sensitize tissue to γ -radiation. However, photochemical NO precursors that can be activated by these near-infrared (NIR) wavelengths are extremely limited. Herein, we have addressed this issue by utilizing the known NIR to visible upconversion properties of lanthanide cations doped NaYF 4 nanocrystals. This result is a potential game changer in multiphoton excitation based therapeutic delivery of NO and other small molecule bioregulators. The bioregulatory molecule nitric oxide (NO) plays important roles in cancer biology and has been implicated in both tumor growth and suppression. [ 1 ] Furthermore, NO is a γ -radiation sensitizer that can enhance selective killing of neoplastic tissues. For these reasons, there is considerable interest in developing methods for NO delivery to specifi c physiological targets. In this context, several laboratories have explored photoactivated NO delivery to specifi c tissues upon demand. [ 2‐7 ] A key advantage of photochemical triggering

Single-band upconversion nanoprobes for multiplexed simultaneous in situ molecular mapping of cancer biomarkers

The identification of potential diagnostic markers and target molecules among the plethora of tumour oncoproteins for cancer diagnosis requires facile technology that is capable of quantitatively analysing multiple biomarkers in tumour cells and tissues. Diagnostic and prognostic classifications of human tumours are currently based on the western blotting and single-colour immunohistochemical methods that are not suitable for multiplexed detection. Herein, we report a general and novel method to prepare single-band upconversion nanoparticles with different colours. The expression levels of three biomarkers in breast cancer cells were determined using single-band upconversion nanoparticles, western blotting and immunohistochemical technologies with excellent correlation. Significantly, the application of antibody-conjugated single-band upconversion nanoparticle molecular profiling technology can achieve the multiplexed simultaneous in situ biodetection of biomarkers in breast cancer cells and tissue specimens and produce more accurate results for the simultaneous quantification of proteins present at low levels compared with classical immunohistochemical technology.

Interface tension-induced synthesis of monodispersed mesoporous carbon hemispheres.

Here we report a novel interface tension-induced shrinkage approach to realize the synthesis of monodispersed asymmetrical mesoporous carbon nanohemispheres. We demonstrate that the products exhibit very uniform hemispherical morphology (130 × 60 nm) and are full of ordered mesopores, endowing them high surface areas and uniform pore sizes. These monodispersed mesoporous carbon hemispheres display excellent dispersibility in water for a long period without any aggregation. Moreover, a brand new feature of the mesoporous carbon materials has been observed for the first time: these monodispersed mesoporous carbon hemispheres show excellent thermal generation property under a NIR irradiation.

Near‐Infrared‐Triggered Azobenzene‐Liposome/Upconversion Nanoparticle Hybrid Vesicles for Remotely Controlled Drug Delivery to Overcome Cancer Multidrug Resistance

Overcoming multidrug resistance is achieved by developing a novel drugdelivery-system paradigm based on azobenzene liposome and phosphatidylcholine-modified upconversion nanoparticle (UCNP) hybrid vesicles for controlled drug release using a nearinfrared (NIR) laser. Upon 980 nm light irradiation, the reversible photoisomerization of the azobenzene derivatives by simultaneous UV and visible light emitted from the UCNPs makes it possible to realize NIR-triggered release of the chemotherapeutic drug doxorubicin.

One‐Step Hydrothermal Synthesis of Carboxyl‐Functionalized Upconversion Phosphors for Bioapplications

In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials.

Mesoporous TiO2 Mesocrystals: Remarkable Defects-Induced Crystallite-Interface Reactivity and Their in Situ Conversion to Single Crystals.

Oriented self-assembly between inorganic nanocrystals and surfactants is emerging as a route for obtaining new mesocrystalline semiconductors. However, the actual synthesis of mesoporous semiconductor mesocrystals with abundant surface sites is extremely difficult, and the corresponding new physical and chemical properties arising from such an intrinsic porous mesocrystalline nature, which is of fundamental importance for designing high-efficiency nanostructured devices, have been rarely explored and poorly understood. Herein, we report a simple evaporation-driven oriented assembly method to grow unprecedented olive-shaped mesoporous TiO2 mesocrystals (FDU-19) self-organized by ultrathin flake-like anatase nanocrystals (∼8 nm in thickness). The mesoporous mesocrystals FDU-19 exhibit an ultrahigh surface area (∼189 m2/g), large internal pore volume (0.56 cm3/g), and abundant defects (oxygen vacancies or unsaturated Ti3+ sites), inducing remarkable crystallite-interface reactivity. It is found that the mesocrystals FDU-19 can be easily fused in situ into mesoporous anatase single crystals (SC-FDU-19) by annealing in air. More significantly, by annealing in a vacuum (∼4.0 × 10–5 Pa), the mesocrystals experience an abrupt three-dimensional to two-dimensional structural transformation to form ultrathin anatase single-crystal nanosheets (NS-FDU-19, ∼8 nm in thickness) dominated by nearly 90% exposed reactive (001) facets. The balance between attraction and electrostatic repulsion is proposed to determine the resulting geometry and dimensionality. Dye-sensitized solar cells based on FDU-19 and SC-FDU-19 samples show ultrahigh photoconversion efficiencies of up to 11.6% and 11.3%, respectively, which are largely attributed to their intrinsic single-crystal nature as well as high porosity. This work gives new understanding of physical and chemical properties of mesoporous semiconductor mesocrystals and opens up a new pathway for designing various single-crystal semiconductors with desired mesostructures for applications in catalysis, sensors, drug delivery, optical devices, etc.

Highly biocompatible zwitterionic phospholipids coated upconversion nanoparticles for efficient bioimaging.

The potential of upconversion nanoparticles (UCNPs) in various biomedical applications, including immunoassays, biomedical imaging, and molecular sensing, requires their surface derivatized to be hydrophilic and biocompatible. Here, a new family of compact zwitterionic ligand systems composed with functional phospholipids was designed and used for the surface modification of UCNPs. The zwitterionic UCNPs are hydrophilic, compact, and easily functionalized. It was proved that zwitterionic phospholipids could provide UCNPs with not only extended pH and salt stability but also little nonspecific interactions to positively and negatively charged proteins, low nonspecific adhesion in live-cell imaging process. Most notably, the efficient in vivo tumor imaging performance and long blood circulation half-life suggests the excellent biocompatibility for in vivo imaging of the zwitterionic UCNPs.

Orthogonal near-infrared upconversion co-regulated site-specific O2 delivery and photodynamic therapy for hypoxia tumor by using red blood cell microcarriers

Pre-existing hypoxia in tumors can result in an inadequate oxygen supply during photodynamic therapy (PDT), which in turn hampers photodynamic efficacy. To overcome this problem, we developed an orthogonal near-infrared upconversion controlled red blood cell (RBC) microcarriers to selectively deliver O2 in hypoxia area. Moreover, this RBC microcarriers are able to overcome a series of complex biological barriers which include transporting across the inflamed endothelium, evading mononuclear phagocyte system, reducing reticuloendothelial system uptake. Based on these abilities, RBC microcarriers have efficient tumors accumulation and are capable of delivery a large amount of O2 for PDT under near-infrared (NIR) irradiation to realize effective solid tumor eradication.