Na Niu

Preparation and Up-Conversion Luminescence of Hollow La2O3:Ln (Ln = Yb/Er, Yb/Ho) Microspheres

Hollow La(2)O(3):Ln (Ln = Yb/Er, Yb/Ho) microspheres with up-conversion (UC) luminescence properties were successfully synthesized via a facile sacrificial template method by employing carbon spheres as hard templates followed by a subsequent heating process. The structure, morphology, formation process, and fluorescent properties are well investigated by various techniques. The results indicate that the hollow La(2)O(3):Ln microspheres can be well indexed to the hexagonal La(2)O(3) phase. The hollow La(2)O(3):Ln microspheres with uniform diameter of about 270 nm maintain the spherical morphology and good dispersion of the carbon spheres template. The shell of the hollow microspheres consists of numerous nanocrystals with the thickness of approximately 40 nm. Moreover, the possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow La(2)O(3):Ln microspheres has also been proposed. The Yb/Er and Yb/Ho codoped La(2)O(3) hollow spheres exhibit bright up-conversion luminescence with different colors derived from different activators under the 980 nm NIR laser excitation. Furthermore, the doping concentration of the Yb(3+) is optimized under fixed concentration of Er(3+)/Ho(3+). This material may find potential applications in drug delivery, hydrogen and Li ion storage, and luminescent displays based on the uniform hollow structure, dimension, and UC luminescence properties.

Up-Conversion Nanoparticle Assembled Mesoporous Silica Composites: Synthesis, Plasmon-Enhanced Luminescence, and Near-Infrared Light Triggered Drug Release

A facile process for the preparation of multifunctional nanospheres combining several advantages of mesoporous channels, up-conversion (UC) luminescence, and photothermal responses into one single entity is reported. First, Gd2O3:Yb/Er assembled mesoporous silica with 2D hexagonal (MCM-41) and 3D cubic (MCM-48) network have been prepared via a one-step procedure. Then, gold nanocrystals with diameter of 5 nm are integrated with the amino group functionalized nanocomposites. Upon 980 nm near infrared (NIR) laser irradiation, a wavelength-dependent enhancement of the UC intensities is observed due to the surface plasmon resonance (SPR) effect of attached gold nanoparticles. These composites have good biocompatibility and sustained anticancer drug (doxorubicin, DOX) release properties, making it a promising candidate for drug delivery. Particularly, under 980 nm NIR laser irradiation, the green UC emission overlaps the SPR band of gold nanocrystals, which causes a photothermal effect of gold nanocrystals and induces a rapid DOX release from the Au hybrid materials. This DOX loaded multifunctional system has an obvious cytotoxic effect and photothermally killing enhanced effect on SKOV3 ovarian cancer cells. The endocytosis process was also demonstrated through confocal laser scanning microscope (CLSM) images. Such novel multifunctional anticancer drug delivery systems, which combine hyperthermia with the chemotherapeutic drugs by synergistic effect, should be of high potential in cancer therapy.

Highly Uniform Hollow GdF3 Spheres: Controllable Synthesis, Tuned Luminescence, and Drug-Release Properties

In this paper, uniform hollow mesoporous GdF3 micro/nanospheres were successfully prepared by a facile two-step synthesis route without using any surfactant, catalyst, and further calcination process. The precursor Gd(OH)CO3 spheres are prepared by a coprecipitation process. After that, uniform and size-tunable GdF3 hollow spheres were easily coprecipitated with NaBF4 at the sacrifice of the precursor with low temperature and short reaction time. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, N2 adsorption/desorption, and up-conversion (UC) photoluminescence spectra were used to characterize the as-obtained products. It is found that the initial pH value and NaBF4/Gd(3+) molar ratios play important roles in the structures, sizes, and phases of the hollow products. The growth mechanism of the hollow spheres has been systematically investigated based on the Kirkendall effect. Under 980 nm IR laser excitation, UC luminescence of the as-prepared Yb(3+)/Er(3+)-codoped GdF3 hollow spheres can be changed by a simple adjustment of the concentration of the Yb(3+) ion. Enhanced red emission is obtained by introducing Li(+) ions in GdF3:Yb(3+)/Er(3+). Furthermore, a doxorubicin release experiment and a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide cytotoxicity assay reveal that the product has potential application in drug delivery and targeted cancer therapy.

Natural‐Product‐Derived Carbon Dots: From Natural Products to Functional Materials

Nature provides an almost limitless supply of sources that inspire scientists to develop new materials with novel applications and less of an environmental impact. Recently, much attention has been focused on preparing natural-product-derived carbon dots (NCDs), because natural products have several advantages. First, natural products are renewable and have good biocompatibility. Second, natural products contain heteroatoms, which facilitate the fabrication of heteroatom-doped NCDs without the addition of an external heteroatom source. Finally, some natural products can be used to prepare NCDs in ways that are very green and simple relative to traditional methods for the preparation of carbon dots from man-made carbon sources. NCDs have shown tremendous potential in many fields, including biosensing, bioimaging, optoelectronics, and photocatalysis. This Review addresses recent progress in the synthesis, properties, and applications of NCDs. The challenges and future direction of research on NCD-based materials in this booming field are also discussed.

Preparation of Carbon Dots for Cellular Imaging by the Molecular Aggregation of Cellulolytic Enzyme Lignin

Carbon dots, which are less than 10 nm in diameter, have been widely investigated because of their unique luminescence properties and potential for use in bioimaging. In the present work, natural carbon dots (L-CDs) were obtained by molecular aggregation, using ethanol-extracted cellulolytic enzyme lignin. The whole process for the preparation of L-CDs was green and simple to operate and did not use toxic chemical reagents or harsh conditions. The newly prepared L-CDs emitted multicolor photoluminescence following one- and two-photon excitation. The L-CDs also showed good cellular biocompatibility, which is crucial for biological applications. One- and two-photon cell-imaging studies demonstrated the potential of L-CDs for bioimaging.

A Versatile Near Infrared Light Triggered Dual-Photosensitizer for Synchronous Bioimaging and Photodynamic Therapy

Photodynamic therapy (PDT) based on Tm3+-activated up-conversion nanoparticles (UCNPs) can effectively eliminate tumor cells by triggering inorganic photosensitizers to generate cytotoxic reactive oxygen species (ROS) upon tissue penetrating near-infrared (NIR) light irradiation. However, the partial use of the emitted lights from UCNPs greatly hinders their application. Here we develop a novel dual-photosensitizer nanoplatform by coating mesoporous graphitic-phase carbon nitride (g-C3N4) layer on UCNPs core, followed by attaching ultrasmall Au25 nanoclusters and PEG molecules (named as UCNPs@g-C3N4-Au25-PEG). The ultraviolet-visible (UV-vis) light and the intensive near infrared (NIR) emission from UCNPs can activate g-C3N4 and excite Au25 nanoclusters to produce ROS, respectively, and thus realize the simultaneous activation of two kinds of photosensitizers for enhanced the efficiency of PDT mediated by a single NIR light excitation. A markedly higher PDT efficacy for the dual-photosensitizer system than any single modality has been verified by the enhanced ROS production and in vitro and in vivo results. By combining the inherent multi-imaging properties (up-conversion, CT, and MRI) of UCNPs, an imaging guided therapeutic platform has been built. As the first report of dual-inorganic-photosensitizer PDT agent, our developed system may be of high potential in future NIR light induced PDT application.

A new drug carrier with oxygen generation function for modulating tumor hypoxia microenvironment in cancer chemotherapy

Hypoxia is the main characteristic of tumor microenvironment, and the one of the key factors that cause the drug resistance of cancer cells for chemotherapy. Anticancer drug such as DOX cannot react with sufficient oxygen to produce reactive oxygen species (ROS) in hypoxic environment, which affects the therapeutic efficiency of the drug. In this work, we constructed a multi-functional nano-carrier (named as FeSiAuO) containing Fe3O4, mesoporous SiO2 and Au2O3 with magnetic, large surface ratio and light induced oxygen production properties. The Au2O3 may decompose into oxygen (O2) and Au under the light irradiation to improve the oxygen concentration of the microenvironment of cancer cells, which increases the sensitivity of cancer cells to drug (DOX), reduces the drug resistance, and effectively exerts the anticancer effect of DOX. Meanwhile, the release of the as-loaded DOX molecule from the porous of SiO2 will be also promoted under light irradiation in diverse pH conditions. With the helping of the magnet effect of the Fe3O4, the DOX can be also targeted delivered to the tumor site under the magnetic field. All of above results were thoroughly examined by the cell and small animal assays, which demonstrate that the FeSiAuO can be served as the multifunctional drug nano-carrier to achieve the targeted high-efficient cancer therapy.

Seeking value from biomass materials: preparation of coffee bean shell-derived fluorescent carbon dots via molecular aggregation for antioxidation and bioimaging applications

Bifunctional carbon dots have shown a large amount of potential in bioimaging and antioxidation applications. However, the hydrothermal method for the preparation of bifunctional carbon dots requires a high energy input and an expensive setup. Moreover, this method breaks down sensitive compounds in the raw materials and could decrease the antioxidation ability of the resulting carbon dots. Here, phenolic extracts of coffee bean shells were used to prepare carbon dots via a cheap, energy-saving, mild molecular aggregation method. The as-prepared carbon dots were characterized by TEM, HPLC, XPS and Raman spectroscopy. The carbon dots had a diameter ranging from 1 to 5 nm and mainly contained three kinds of phenolic compounds including 3,4,5-trihydroxybenzoic acid, 3,4-dihydroxybenzaldehyde and 3,4-dihydroxybenzoic acid. The carbon dots demonstrated a strong antioxidation capacity, which was comparable to the commercially available butylated hydroxytoluene. The EC50 of the carbon dots was 110 μg mL−1. The carbon dots had a pH-/excitation-dependent fluorescence. The as-prepared carbon dots also showed anti-bleaching fluorescence, which was better than that of the commercially available 4′,6-diamidino-2-phenylindole. Based on this finding, the excellent biocompatibility of carbon dots enabled them to be successfully used for banana storage and imaging both cancer cell nuclei and tumors in vivo.