Nanostructured cation disordered Li₂FeTiO₄/graphene composite as high capacity cathode for lithium-ion batteries

<p>Nanostructured Li₂FeTiO₄/graphene composite with a cation disordered rock salt structure (Fm-3 m) has been synthesised via a solgel process using graphene oxide (GO) as a template. The as-prepared Li₂FeTiO₄ nanoparticles with a particle size of 20–50 nm are uniformly distributed on the graphene substrate. The Li₂FeTiO₄/graphene cathode shows phase transformations of Fe²⁺/Fe³⁺ and Fe³⁺/Fe⁴⁺ in a wide potential range from 1.5 to 5.0 V and possesses a high discharge capacity of 218.6 mAh g⁻¹ (equivalent to 1.4 Li per formula unit). A reversible capacity of 176.9 mAh g⁻¹ is maintained after 50 cycles. High capacity retention rate at 1C after 200 cycles is obtained. The Li₂FeTiO₄/graphene should be of great interest as a potential cathode material for high-performance lithium-ion batteries.</p

Dynamic Assembly of DNA Nanostructures in Cancer Cells Enables the Coupling of Autophagy Activating and Real-Time Tracking

Developing dynamic nanostructures for in situ regulation of biological processes inside living cells is of great importance in biomedical research. Herein we report the cascaded assembly of Y-shaped branched DNA nanostructure (YDN) during intracellular autophagy. YDN contains one arm with semi-i-motif sequence and Cy3-BHQ2, and another arm with an apurinic/apyrimidinic (AP) site and Cy5-BHQ3. Upon uptake by cancer cells, intermolecular i-motif structures are formed in response to lysosomal H+, causing the formation of YDN-dimer and the recovery of Cy3 fluorescence; when escapes occur from the lysosome to the cytoplasm, the YDN-dimer responds to the overexpressed APE1, leading to the assembly of YDN into the DNA network and the fluorescence recovery of Cy5. Simultaneously, the cascaded assembly activates autophagy, and thus the process of assembly of YDN and autophagy flux can be spatiotemporally coupled. This work illustrates the potential of DNA nanostructures for the in situ regulation of intracellular dynamic events with spatiotemporal control

Successive Layer-by-Layer Strategy for Multi-Shell Epitaxial Growth: Shell Thickness and Doping Position Dependence in Upconverting Optical Properties

One pot successive layer-by-layer (SLBL) strategy is introduced to fabricate the core/shell upconversion nanoparticles (NPs) for the first time by using high boiling-point Re-OA (rare-earth chlorides dissolved in oleic acid at 140 °C) and Na-TFA-OA (sodium trifluoroacetate dissolved in oleic acid at room temperature) as shell precursor solutions. This protocol is flexible to deposit uniform multishell on both hexagonal (β) and cubic (α) phase cores by successive introducing of the shell precursor solutions. Shell thickness of the obtained NPs with narrow size distribution (σ < 10%) can be well controlled from 1 monolayer (∼0.36 nm) to more than 20 monolayers (∼8 nm) by simply tuning the amounts of the shell precursors. Furthermore, the tunable doping positions (core doping and shell doping) can also be achieved by adjusting the species and addition sequence of the shell precursors. As a result of the high quality uniform shell and advanced core/shell structures, the optical properties of the obtained core/shell NPs could be improved in upconversion luminescence efficiency (up to 0.51 ± 0.08%), stability (more resistant to quenching by water) and multicolor luminescence emission

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

Three-Dimensional Graphene/Single-Walled Carbon Nanotube Aerogel Anchored with SnO₂ Nanoparticles for High Performance Lithium Storage

A unique 3D graphene-single walled carbon nanotube (G-SWNT) aerogel anchored with SnO₂ nanoparticles (SnO₂@G-SWCNT) is fabricated by the hydrothermal self-assembly process. The influences of mass ratio of SWCNT to graphene on structure and electrochemical properties of SnO₂@G-SWCNT are investigated systematically. The SnO₂@G-SWCNT composites show excellent electrochemical performance in Li-ion batteries; for instance, at a current density of 100 mA g^–1, a specific capacity of 758 mAh g^–1 was obtained for the SnO₂@G-SWCNT with 50% SWCNT in G-SWCNT and the Coulombic efficiency is close to 100% after 200 cycles; even at current density of 1 A g^–1, it can still maintain a stable specific capacity of 537 mAh g^–1 after 300 cycles. It is believed that the 3D G-SWNT architecture provides a flexible conductive matrix for loading the SnO₂, facilitating the electronic and ionic transportation and mitigating the volume variation of the SnO₂ during lithiation/delithiation. This work also provides a facile and reasonable strategy to solve the pulverization and agglomeration problem of other transition metal oxides as electrode materials

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 NaGdF₄ shell on NaYF₄: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 NaYF₄:Yb,Er@NaGdF₄ nanocrystal core/shell structure at the subnanometer level was realized for the first time. Furthermore, a strong linear link between the NaGdF₄ shell thickness and the optical response of the hexagonal NaYF₄:Yb,Er@NaGdF₄ core/shell nanocrystals has been established. During the epitaxial growth of the NaGdF₄ 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

Facile Peptides Functionalization of Lanthanide-Based Nanocrystals through Phosphorylation Tethering for Efficient <i>in Vivo</i> NIR-to-NIR Bioimaging

Peptide modification of nanoparticles is a challenging task for bioapplications. Here, we show that noncovalent surface engineering based on ligand exchange of peptides for lanthanide based upconversion and downconversion near-infrared (NIR) luminescent nanoparticles can be efficiently realized by modifying the hydroxyl functional group of a side grafted serine of peptides into a phosphate group (phosphorylation). By using the phosphorylated peptide with the arginine-glycine-aspartic acid (RGD) targeting motifs as typical examples, the modification allows improving the selectivity, sensitivity, and signal-to-noise ratio for the cancer targeting and bioimaging and reducing the toxicity derived from nonspecific interactions of nanoparticles with cells. The <i>in vivo</i> NIR bioimaging signal could even be detected at low injection amounts down to 20 μg per animal

Spatially Confined Fabrication of Core–Shell Gold Nanocages@Mesoporous Silica for Near-Infrared Controlled Photothermal Drug Release

In this work, we have successfully developed a novel multifunctional near-infrared (NIR)-stimulus controlled drug release system based on gold nanocages as photothermal cores, mesoporous silica shells as supporters to increase the anticancer drug loading and thermally responsive poly­(<i>N</i>-isopropylacrylamide) (PNIPAM) as NIR-stimuli gatekeepers (Au-nanocage@mSiO₂@ PNIPAM). The unique Au-nanocage@mSiO₂ nanocarrier was elaborately fabricated by utilizing yolk-shell Ag-nanocube@mSiO₂ nanostructure as a template by means of spatially confined galvanic replacement. The Au nanocage cores can effectively absorb and convert light to heat upon irradiation with a NIR laser, resulting in the collapse of the PNIPAM shell covering the exterior of mesoporous silica, and exposes the pores of mesoporous silica shell, realizing the triggered release of entrapped DOX drugs. The in vitro studies have clearly demonstrated the feasibility and advantage of the novel nanocarriers for remote-controlled drug release systems

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

Intracellular and <i>in Vivo</i> Cyanide Mapping via Surface Plasmon Spectroscopy of Single Au–Ag Nanoboxes

Cyanide is extremely toxic to organisms but difficult to detect in living biological specimens. Here, we report a new CN^– sensing platform based on unmodified Au–Ag alloy nanoboxes that etch in the presence of this analyte, yielding a shift in plasmon frequency that correlates with the analyte concentration. Significantly, when combined with dark field microscopy, these particle probes can be used to measure CN^– concentrations in HeLa cells and <i>in vivo</i> in Zebra fish embryos. The limit of detection (LOD) of the novel method is 1 nM (below the acceptable limit defined by the World Health Organization), and finite-difference time-domain (FDTD) calculations are used to understand the CN^– induced spectral shifts