Shili Gai

Functionalized mesoporous silica materials for controlled drug delivery

In the past decade, non-invasive and biocompatible mesoporous silica materials as efficient drug delivery systems have attracted special attention. Great progress in structure control and functionalization (magnetism and luminescence) design has been achieved for biotechnological and biomedical applications. This review highlights the most recent research progress on silica-based controlled drug delivery systems, including: (i) pure mesoporous silica sustained-release systems, (ii) magnetism and/or luminescence functionalized mesoporous silica systems which integrate targeting and tracking abilities of drug molecules, and (iii) stimuli-responsive controlled release systems which are able to respond to environmental changes, such as pH, redox potential, temperature, photoirradiation, and biomolecules. Although encouraging and potential developments have been achieved, design and mass production of novel multifunctional carriers, some practical biological application, such as biodistribution, the acute and chronic toxicities, long-term stability, circulation properties and targeting efficacy in vivo are still challenging.

Recent Progress in Rare Earth Micro/Nanocrystals: Soft Chemical Synthesis, Luminescent Properties, and Biomedical Applications

Synthesis, Luminescent Properties, and Biomedical Applications Shili Gai,†,‡ Chunxia Li,† Piaoping Yang,*,‡ and Jun Lin*,† †State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China ‡Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin, 150001, P. R. China

A Yolk-like Multifunctional Platform for Multimodal Imaging and Synergistic Therapy Triggered by a Single Near-Infrared Light

To integrate photodynamic therapy (PDT) with photothermal therapy (PTT) and chemotherapy for enhanced antitumor efficiency, we developed a mild and rational route to synthesize novel multifunctional GdOF:Ln@SiO2 (Ln = 10%Yb/1%Er/4%Mn) mesoporous capsules using strong up-conversion luminescent (UCL) GdOF:Ln as cores and mesoporous silica layer as shells, followed by modification with varied functional groups onto the framework. It was found that due to the codoped Yb/Er/Mn in GdOF, the markedly enhanced red emission can efficiently transfer energy to the conjugated PDT agent (ZnPc) which produces high singlet oxygen, and the incorporated carbon dots outside the shell can generate obvious thermal effect under 980 nm laser irradiation and also prevent the premature leaking of ZnPc. Simultaneously, the as-produced thermal effect can obviously enhance the doxorubicin (DOX) release, which greatly improves the chemotherapy, resulting in a synergistic therapeutic effect. The system exhibits drastically enhanced therapeutic efficiency against tumor growth, as demonstrated both in vitro and in vivo. Especially, the doped rare earth ions in the host endow the material with excellent UCL imaging, magnetic resonance imaging (MRI), and computed tomography (CT) imaging properties, thus realizing the target of multimodal imaging guided multiple therapies.

A sandwich-type three-dimensional layered double hydroxide nanosheet array/graphene composite: fabrication and high supercapacitor performance

In this study, we have developed, for the first time, a facile in situ growth process to prepare a hierarchical three-dimensional (3D) composite composed of graphene layers with layered double hydroxide (LDH) nanosheet arrays grown on both sides. The fabrication process involves coating AlOOH colloids onto the graphene surfaces and the subsequent in situ growth of layered NiAl–LDH nanosheet arrays on the surfaces of graphene sheets via a hydrothermal process. It is found that the NiAl–LDH nanosheet arrays grow perpendicularly and uniformly on both sides of the graphene sheets, constructing a hierarchical 3D nanocomposite with an interesting sandwich structure. This uniquely structured composite has a large specific surface area (184.7 m2 g−1) and typical mesoporous characteristics, which are favorable for achieving high pseudocapacitance performance. Our results reveal that the composite has a specific capacitance of 1329 F g−1 at a current density of 3.57 A g−1, and the specific capacitance still remains as high as 851 F g−1 even when the current density is increased to 17.86 A g−1. The specific capacitance remains at 91% (823 F g−1) after 500 cycles at 15.30 A g−1 compared with 74% for pure Ni/Al–LDH. The in situ growth method may pave a way to design and fabricate diverse LDH/graphene composites with interesting structures for potential application in supercapacitors and other fields.

Tunable multicolor and bright white emission of one-dimensional NaLuF4:Yb3+,Ln3+ (Ln = Er, Tm, Ho, Er/Tm, Tm/Ho) microstructures

Well-defined one-dimensional NaLuF4:Yb3+,Er3+/Tm3+/Ho3+ microtubes and microrods were successfully prepared by a surfactant-free molten salt method for the first time. It is found that with the prolonged time, the phase of NaLuF4 transforms from cubic to hexagonal, while the morphology changes from nanoparticles to microtubes then to microrods. Moreover, upon 980 nm laser diode (LD) excitation, white up-conversion (UC) light was successfully achieved by properly tuning the sensitizer (Yb3+) concentration in the host matrix. The relative emission intensities of different emission colors in Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+ doped β-NaLuF4 can be precisely adjusted in a broad range by tuning the Yb3+ doping concentration. Consequently, effective UC emissions with multicolors and a strong white light can be realized in β-NaLuF4:Yb3+/Er3+/Tm3+, and β-NaLuF4:Yb3+/Tm3+/Ho3+ structures by the appropriate control of the emission intensity balance for the three blue, green, and red basic colors. UC mechanisms in the co-doping and tri-doping β-NaLuF4 samples were analyzed in detail based on the emission spectra and the plot of luminescence intensity to pump power. The as-obtained abundant luminescence colors in a much wide region contribute themselves great potential applications in various fields. Furthermore, the paper also provides an effective and facile approach to gain a desired color by manipulating the sensitizer concentration.

Highly Emissive Dye-Sensitized Upconversion Nanostructure for Dual-Photosensitizer Photodynamic Therapy and Bioimaging

Rare-earth-based upconversion nanotechnology has recently shown great promise for photodynamic therapy (PDT). However, the NIR-induced PDT is greatly restricted by overheating issues on normal bodies and low yields of reactive oxygen species (ROS, 1O2). Here, IR-808-sensitized upconversion nanoparticles (NaGdF4:Yb,Er@NaGdF4:Nd,Yb) were combined with mesoporous silica, which has Ce6 (red-light-excited photosensitizer) and MC540 (green-light-excited photosensitizer) loaded inside through covalent bond and electrostatic interaction, respectively. When irradiated by tissue-penetrable 808 nm light, the IR-808 greatly absorb 808 nm photons and then emit a broadband peak which overlaps perfectly with the absorption of Nd3+ and Yb3+. Thereafter, the Nd3+/Yb3+ incorporated shell synergistically captures the emitted NIR photons to illuminate NaGdF4:Yb,Er zone and then radiate ultrabright green and red emissions. The visible emissions simultaneously activate the dual-photosensitizer to produce a large amount of ROS and, importantly, low heating effects. The in vitro and in vivo experiments indicate that the dual-photosensitizer nanostructure has trimodal (UCL/CT/MRI) imaging functions and high anticancer effectiveness, suggesting its potential clinical application as an imaging-guided PDT technique.

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.

Fabrication and electrochemical performance of 3D hierarchical β-Ni(OH)2 hollow microspheres wrapped in reduced graphene oxide

A novel structured reduced graphene oxide/Ni(OH)2 (rGO/Ni(OH)2) hybrid composite with enhanced electrochemical performance was prepared by wrapping β-Ni(OH)2 hollow microspheres in rGO sheets via a facile solvothermal route, using poly(L-lysine) (PLL) as reductant and ethylene glycol (EG) as coupling agent. The structural, morphological and electrochemical properties of the composite were well examined. The results show that single-crystalline β-Ni(OH)2 hollow microspheres are enveloped in rGO sheets after thermal treatment in the hybrid composite, which exhibits a high specific capacitance of 1551.8 F g−1 at a current density of 2.67 A g−1 and a capacity retention of 102% after 2000 cycles. Notably, in comparison with pure β-Ni(OH)2 hollow microspheres and the simple mixture (mixture of rGO and Ni(OH)2 spheres), the rGO/β-Ni(OH)2 composite exhibited superior electrochemical properties, which may be due to the wrapped electrically conducting graphene sheets and the unique three-dimensional (3D) structure of the composite. The rational design, interesting structure and the ideal electrochemical performance of this graphene-based composite suggest its potential applications in high energy storage systems.

Hydrothermal synthesis and luminescent properties of YVO4:Ln3+ (Ln = Eu, Dy, and Sm) microspheres

Rare-earth ions (Eu(3+), Dy(3+), Sm(3+)) doped YVO(4) microspheres with uniform morphologies were successfully prepared via a simple hydrothermal route using N,N-dimethylformamide (DMF) as the solvent and polyvinylpyrrolidone (PVP) as protective agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, and the kinetic decays were employed to examine the resulting phase formation, particle morphology and luminescent properties. The XRD results reveal that all the doped samples are of high crystallization which are assigned to the pure tetragonal phase of YVO(4). Additionally, the DMF/H(2)O volume ratio and the concentration of PVP both have obvious effects on the morphologies and sizes of the as-synthesized products. The sample prepared at 180 degrees C for 24 h with the DMF/H(2)O volume ratio of 3/1 and 0.4 g/L PVP concentration exhibits uniformly spherical shape with the diameter of 1-2 microm. Upon excitation by ultraviolet radiation or low-voltage electron beams excitation, the YVO(4):Ln(3+) (Ln=Eu, Dy, and Sm) samples show strong light emissions with different colors from the doped Ln(3+) ions. These phosphors exhibit potential applications in the fields of fluorescent lamps and light emitting diodes (LEDs).

Uniform Hollow Lu2O3:Ln (Ln = Eu3+, Tb3+) Spheres: Facile Synthesis and Luminescent Properties

Uniform hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) phosphors have been successfully prepared via a urea-assisted homogeneous precipitation method using carbon spheres as templates, followed by a subsequent calcination process. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformed infrared (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, kinetic decays, quantum yields (QY), and UV-visible diffuse reflectance spectra were employed to characterize the samples. The results show that hollow Lu(2)O(3):Ln spheres can be indexed to cubic Gd(2)O(3) phase with high purity. The as-prepared hollow Lu(2)O(3):Ln phosphors are confirmed to be uniform in shape and size with diameter of about 300 nm and shell thickness of approximate 20 nm. The possible formation mechanism of evolution from the carbon spheres to the amorphous precursor and to the final hollow Lu(2)O(3):Ln microspheres has been proposed. Upon ultraviolet (UV) and low-voltage electron beams excitation, the hollow Lu(2)O(3):Ln (Ln = Eu(3+), Tb(3+)) spheres exhibit bright red (Eu(3+), (5)D(0)-(7)F(2)) and green (Tb(3+), (5)D(4)-(7)F(5)) luminescence, which may find potential applications in the fields of color display and biomedicine.