Piaoping Yang

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

Bioactive, luminescent and mesoporous europium-doped hydroxyapatite as a drug carrier

Bioactive, luminescent and mesoporous europium-doped hydroxyapatite (Eu:HAp) was successfully prepared through a simple one-step route using cationic surfactant as template. The obtained multifunctional hydroxyapatite was performed as a drug delivery carrier to investigate the drug storage/release properties using ibuprofen (IBU) as a model drug. The structural, morphological, textural and optical properties were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, and photoluminescence (PL) spectra, respectively. The results reveal that the multifunctional hydroxyapatites exhibit the typical ordered characteristics of the hexagonal mesostructure, and have rod-like morphology with the particle size of 20-40 nm in width and 100-200 nm in length. The drug storage/release test indicates that the luminescent HAp shows much similar drug loading amount and cumulative release rate to those of pure HAp. Interestingly, the IBU-loaded samples still show red luminescence of Eu(3+) ((5)D(0)-(7)F(1),(2)) under UV irradiation, and the emission intensities of Eu(3+) in the drug carrier system vary with the released amount of IBU, thus making the drug release be easily tracked and monitored by the change of the luminescence intensity.

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.

Charge-Convertible Carbon Dots for Imaging-Guided Drug Delivery with Enhanced in Vivo Cancer Therapeutic Efficiency

Carbon dots (CDs) are remarkable nanocarriers due to their promising optical and biocompatible capabilities. However, their practical applicability in cancer therapeutics is limited by their insensitive surface properties to complicated tumor microenvironment in vivo. Herein, a tumor extracellular microenvironment-responsive drug nanocarrier based on cisplatin(IV) prodrug-loaded charge-convertible CDs (CDs-Pt(IV)@PEG-(PAH/DMMA)) was developed for imaging-guided drug delivery. An anionic polymer with dimethylmaleic acid (PEG-(PAH/DMMA)) on the fabricated CDs-Pt(IV)@PEG-(PAH/DMMA) could undergo intriguing charge conversion to a cationic polymer in mildly acidic tumor extracellular microenvironment (pH ∼ 6.8), leading to strong electrostatic repulsion and release of positive CDs-Pt(IV). Importantly, positively charged nanocarrier displays high affinity to negatively charged cancer cell membrane, which results in enhanced internalization and effective activation of cisplatin(IV) prodrug in the reductive cytosol. The in vitro experimental results confirmed that this promising charge-convertible nanocarrier possesses better therapeutic efficiency under tumor extracellular microenvironment than normal physiological condition and noncharge-convertible nanocarrier. The in vivo experiments further demonstrated high tumor-inhibition efficacy and low side effects of the charge-convertible CDs, proving its capability as a smart drug nanocarrier with enhanced therapeutic effects. The present work provides a strategy to promote potential clinical application of CDs in the cancer treatment.

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.

Three-dimensional hierarchical MoS2 nanoflake array/carbon cloth as high-performance flexible lithium-ion battery anodes

Flexible lithium-ion batteries are the key to powering a new generation of flexible electronics such as roll-up displays, smart electronics, and wearable devices. Here we report, for the first time, one-step hydrothermal synthesis of a three-dimensional (3D) hierarchical MoS2 nanoflake array/carbon cloth which shows potential for improving the performance of flexible lithium-ion batteries. Structural characterizations show that the 3D hierarchical MoS2 nanoflake array/carbon cloth has a similar ordered woven structure to the bare carbon cloth. Each carbon microfiber is covered with many highly ordered 3D MoS2 nanoflake arrays, and a typical MoS2 nanoflake, with expanded spacing of the (002) crystal plane, has a uniform width of about 400 nm and a thickness of less than 15 nm. The flexible 3D MoS2 nanoflake array/carbon cloth as a flexible lithium-ion battery anode has a high reversible capacity of 3.0–3.5 mA h cm−2 at a current density of 0.15 mA cm−2 and outstanding discharging/charging rate stability. Moreover, a fabricated full battery, with commercial LiCoO2 powder and the hierarchical architectures as electrodes, exhibits high flexibility and good electrochemical performance, and can light a commercial red LED even after 50 cycles of bending the full battery.

Uniform Colloidal Alkaline Earth Metal Fluoride Nanocrystals: Nonhydrolytic Synthesis and Luminescence Properties

In this paper, we present a facile and general synthetic route to high-quality alkaline earth metal fluoride (AEF2, AE = Ca, Sr, Ba) nanocrystals and CaF2:Tb(3+) nanocrystals based on the thermal decomposition of corresponding trifluoroacetate precursors in hot oleylamine. X-ray diffraction, transmission electron microscopy, thermogravimetric and differential thermal analysis, Fourier transform infrared spectra, photoluminescence spectra, and kinetic decays were employed to characterize the samples. The use of single-source precursors plays an important role in the formation of high-quality AEF 2 nanocrystals, and the formation process is demonstrated in detail. The obtained AEF2 nanocrystals are nearly monodisperse in size and highly crystalline, and they can be well dispersed in nonpolar solvents to form stable and clear colloidal solutions, which all display purple emissions under ultraviolet excitation due to the numerous surface defects of nanocrystals with large surface/volume ratios. Furthermore, we demonstrate the feasibility of introducing Tb(3+) ions into the CaF2 host via this method, which shows strong green emission corresponding to the characteristic (5)D4-(7)F(J) (J = 3, 4, 5, 6) emission of Tb(3+) ions, which can be potentially used as labels for biological molecules.

Multicolor Tuning of Manganese-Doped ZnS Colloidal Nanocrystals

In this paper, we report a facile route which is based on tuning doping concentration of Mn(2+) ions in ZnS nanocrystals, to achieve deliberate color modulation from blue to orange-yellow under single-wavelength excitation. X-ray diffraction (XRD), transmission electron microscopy (TEM), as well as photoluminescence (PL) spectra were employed to characterize the obtained samples. In this process, the relative emission intensities of both ZnS host (blue) and Mn(2+) dopant (orange-yellow) are sensitive to the Mn(2+) doping concentration, due to the energy transfer from ZnS host to Mn(2+) dopant. As a result of fine-tuning of these two emission components, white emission can be realized for Mn(2+)-doped ZnS nanocrystals. Furthermore, the as-synthesized doped nanocrystals possess extremely narrow size distribution and can be readily transferred into aqueous solution for the next potential applications.

Shape-Controllable Synthesis and Morphology-Dependent Luminescence Properties of GaOOH:Dy3+ and β-Ga2O3:Dy3+

Dy(3+)-doped gallium oxide hydroxides (GaOOH:Dy(3+)) with various morphologies (submicrospindles, submicroellipsoids, 3D hierarchical microspheres) were synthesized by a facile soft-chemical method. After annealing at 1000 degrees C, the GaOOH:Dy(3+) precursor was easily converted to beta-Ga(2)O(3):Dy(3+) phosphors which kept their original morphologies. The as-prepared GaOOH:Dy(3+) and beta-Ga(2)O(3):Dy(3+) products were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), low- to high-resolution transmission electron microscopy (TEM), selected area electron diffraction (SAED), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, and quantum yield (QY). With an increase in pH from 4 to 9, the morphology of GaOOH:Dy(3+) varied from submicrospindles to 3D hierarchical microspheres of self-assembled nanoparticles. A possible mechanism for the formation of various morphologies of GaOOH:Dy(3+) and beta-Ga(2)O(3):Dy(3+) was proposed. Under ultraviolet and low-voltage electron beam excitation, the pure beta-Ga(2)O(3) samples exhibit a blue emission with a maximum at 438 nm originating from the GaO(6) groups, while the beta-Ga(2)O(3):Dy(3+) samples show the characteristic emission of Dy(3+) corresponding to (4)F(9/2) --> (6)H(15/2, 13/2) transitions due to an efficient energy transfer from beta-Ga(2)O(3) to Dy(3+). A simple model was proposed to explain the energy transfer process and luminescence mechanism. Furthermore, the dependence of luminescence intensity on the morphology has been investigated in detail. Under 257 nm UV and electron beam excitation, the beta-Ga(2)O(3):Dy(3+) phosphor with a submicroellipsoid shape shows the highest relative emission intensity and quantum yield compared with other morphologies, and the obtained phosphors have potential applications in the areas of fluorescent lamps and field emission displays (FEDs).