Quli Fan

Lanthanide-doped NaxScF3+ x nanocrystals : crystal structure evolution and multicolor tuning

Rare-earth-based nanomaterials have recently drawn considerable attention because of their unique energy upconversion (UC) capabilities. However, studies of Sc(3+)-based nanomaterials are still absent. Herein we report the synthesis and fine control of Na(x)ScF(3+x) nanocrystals by tuning of the ratio of oleic acid (OA, polar surfactant) to 1-octadecene (OD, nonpolar solvent). When the OA:OD ratio was increased from low (3:17) to high (3:7), the nanocrystals changed from pure monoclinic phase (Na(3)ScF(6)) to pure hexagonal phase (NaScF(4)) via a transition stage at an intermediate OA:OD ratio (3:9) where a mixture of nanocrystals in monoclinic and hexagonal phases was obtained and the coexistence of the two phases inside individual nanocrystals was also observed. More significantly, because of the small radius of Sc(3+), Na(x)ScF(3+x):Yb/Er nanocrystals show different UC emission from that of NaYF(4):Yb/Er nanocrystals, which broadens the applications of rare-earth-based nanomaterials ranging from optical communications to disease diagnosis.

Preparation of MoS2-Polyvinylpyrrolidone Nanocomposites for Flexible Nonvolatile Rewritable Memory Devices with Reduced Graphene Oxide Electrodes

A facile method for exfoliation and dispersion of molybdenum disulfide (MoS2) with the aid of polyvinylpyrrolidone (PVP) is proposed. The resultant PVP-coated MoS2 nanosheets, i.e., MoS2-PVP nanocomposites, are well dispersed in the low-boiling ethanol solvent, facilitating their thin film preparation and the device fabrication by solution processing technique. As a proof of concept, a flexible memory diode with the configuration of reduced graphene oxide (rGO)/MoS2-PVP/Al exhibited a typical bistable electrical switching and nonvolatile rewritable memory effect with the function of flash. These experimental results prove that the electrical transition is due to the charge trapping and detrapping behavior of MoS2 in the PVP dielectric material. This study paves a way of employing two-dimensional nanomaterials as both functional materials and conducting electrodes for the future flexible data storage.

Recent Developments in Top‐Emitting Organic Light‐Emitting Diodes

Organic light-emitting diodes (OLEDs) have rapidly progressed in recent years due to their unique characteristics and potential applications in flat panel displays. Significant advancements in top-emitting OLEDs have driven the development of large-size screens and microdisplays with high resolution and large aperture ratio. After a brief introduction to the architecture and types of top-emitting OLEDs, the microcavity theory typically used in top-emitting OLEDs is described in detail here. Then, methods for producing and understanding monochromatic (red, green, and blue) and white top-emitting OLEDs are summarized and discussed. Finally, the status of display development based on top-emitting OLEDs is briefly addressed.

Bulk Heterojunction Polymer Memory Devices with Reduced Graphene Oxide as Electrodes

A unique device structure with a configuration of reduced graphene oxide (rGO) /P3HT:PCBM/Al has been designed for the polymer nonvolatile memory device. The current-voltage (I-V) characteristics of the fabricated device showed the electrical bistability with a write-once-read-many-times (WORM) memory effect. The memory device exhibits a high ON/OFF ratio (10(4)-10(5)) and low switching threshold voltage (0.5-1.2 V), which are dependent on the sheet resistance of rGO electrode. Our experimental results confirm that the carrier transport mechanisms in the OFF and ON states are dominated by the thermionic emission current and ohmic current, respectively. The polarization of PCBM domains and the localized internal electrical field formed among the adjacent domains are proposed to explain the electrical transition of the memory device.

Transferring Biomarker into Molecular Probe: Melanin Nanoparticle as a Naturally Active Platform for Multimodality Imaging

Developing multifunctional and easily prepared nanoplatforms with integrated different modalities is highly challenging for molecular imaging. Here, we report the successful transfer of an important molecular target, melanin, into a novel multimodality imaging nanoplatform. Melanin is abundantly expressed in melanotic melanomas and thus has been actively studied as a target for melanoma imaging. In our work, the multifunctional biopolymer nanoplatform based on ultrasmall (<10 nm) water-soluble melanin nanoparticle (MNP) was developed and showed unique photoacoustic property and natural binding ability with metal ions (for example, 64Cu2+, Fe3+). Therefore, MNP can serve not only as a photoacoustic contrast agent, but also as a nanoplatform for positron emission tomography (PET) and magnetic resonance imaging (MRI). Traditional passive nanoplatforms require complicated and time-consuming processes for prebuilding reporting moieties or chemical modifications using active groups to integrate different contrast properties into one entity. In comparison, utilizing functional biomarker melanin can greatly simplify the building process. We further conjugated αvβ3 integrins, cyclic c(RGDfC) peptide, to MNPs to allow for U87MG tumor accumulation due to its targeting property combined with the enhanced permeability and retention (EPR) effect. The multimodal properties of MNPs demonstrate the high potential of endogenous materials with multifunctions as nanoplatforms for molecular theranostics and clinical translation.

The synthesis of shape-controlled MnO2/graphene composites via a facile one-step hydrothermal method and their application in supercapacitors

Novel MnO2 petal nanosheet and nanorod/graphene composites are successfully fabricated by a facile one-step hydrothermal method through changing the content of the Mn source. The formation mechanism of different morphologies of MnO2/graphene composites have been studied. The structure of the MnO2/graphene is “sandwich”-like, with MnO2 petal nanosheets and nanorods homogeneously anchored on each side of the graphene. Furthermore, the MnO2/graphene composites with different shapes can be used for supercapacitor electrode materials. The experimental results show that the MnO2 petal nanosheet/graphene composite has better capacitance performance than that of the MnO2 nanorod/graphene composite. The MnO2 petal nanosheet/graphene composite shows excellent specific capacitance as high as 516.8 F g−1 at a scan rate of 1 mV s−1 in 1 M Na2SO4 electrolyte and good long-term cycle stability, indicating its potential application to act as a promising electrode material for high-performance supercapacitors. This study provides a facile and in situ method to prepare metal oxide/graphene composite materials and a novel scaffold to construct other metal oxides with graphene for energy storage.

Perylene-diimide-based nanoparticles as highly efficient photoacoustic agents for deep brain tumor imaging in living mice

In order to promote preclinical and clinical applications of photoacoustic imaging, novel photoacoustic contrast agents are highly desired for molecular imaging of diseases, especially for deep tumor imaging. Here, perylene-3,4,9,10-tetracarboxylic diiimide-based near-infrared-absorptive organic nanoparticles are reported as an efficient agent for photoacoustic imaging of deep brain tumors in living mice with enhanced permeability and retention effect.

Efficient 9-alkylphenyl-9-pyrenylfluorene substituted pyrene derivatives with improved hole injection for blue light-emitting diodes

Two efficient blue-light-emitting materials with stable diarylfluorene and hole-transporting pyrene groups, 9-alkoxyphenyl-9-pyrenylfluorene substituted pyrenes (EHOP1 and EHOP2), have been synthesized by Suzuki coupling reaction and have been fully characterized. They have extreme thermal stability in nitrogen with onset decomposition temperature over 430 °C. They are amorphous materials with Tg of 103 and 191 °C for EHOP1 and EHOP2, respectively. They show stable bright blue emission in the solid state. Due to the non-conjugated pyrene groups at C9 of the fluorene moieties, the absorption spectra of the two compounds showed some characteristic peaks and they showed improved hole-injection ability than conjugated fluorene derivatives. A preliminary simple three-layer blue light-emitting diode, i.e. ITO/TCTA (8 nm)/EHOP1 (30 nm)/BCP (45 nm)/Mg:Ag, was obtained without the need for a hole-injection layer, with high luminance of 11620 cd m−2, turn-on voltage of 4.0 V and current efficiency of 3.04 cd A−1. Furthermore, the device still had a considerable efficiency of 1.74 cd A−1, when the luminescence reaches its maximum.

Synthesis, Structure, and Optoelectronic Properties of Phosphafluorene Copolymers

Copolymers of phosphafluorenes are obtained through Suzuki copolymerization. The phosphorus-containing copolymers show unique optical, electrochemical, and optoelectronic properties. Blue and white electroluminescence can be observed, depending on the modifications of the phosphorus atoms. It is the first time that conjugated polymers containing phosphafluorene have been prepared and used in PLEDs. Phosphafluorenes are new building blocks for conjugated oligomers and polymers.

DNA biosensors based on water-soluble conjugated polymers.

Conjugated polymers (CPs) with large, delocalised molecular structures exhibit unique optical and electrochemical characteristics that can be used as excellent sensing elements. Recently, research on chemical and biological sensors that use water-soluble CPs as transducers has generated intense interest. Two main sensing mechanisms are used for the detection of DNA-related events, such as hybridisation, mismatch, single nucleotide polymorphism (SNP), SNP genotyping, conformational changes, and cleavage of the nucleic acids. One mechanism takes advantage of the fluorescence resonance energy transfer (FRET) between CPs and a chromophore label on the nucleic acid probes in which a series of cationic polyfluorene, polythiophene and polyarylene derivatives are frequently used. The other mechanism relies on the conformational effects of CPs, which is induced by combination of the specific targets in which cationic polythiophene derivatives are often used. The electron transfer property of CPs are always used to design high sensitive electrochemical DNA biosensors. Here we review recent progress in the development of optical and electrochemical DNA biosensors based on water-soluble CPs.