Junmin Xue

Synthesis of porous hollow Fe3O4 beads and their applications in lithium ion batteries

Porous hollow Fe3O4 beads constructed with rod-shaped Fe3O4 nanoparticles were synthesized via a facile solvothermal route. The formation mechanism of the obtained Fe3O4 beads was proposed on the basis of oriented assembly and Ostwald ripening. The as-prepared Fe3O4 beads had promising applications as lithium ion battery anodes, which showed a reversible specific capacity of 500 mAh g−1 after 50 cycles at 100 mA g−1. After being decorated with a carbon coating layer, the Fe3O4/C composite beads showed an enhanced capacity of 700 mAh g−1 after 50 cycles at 100 mA g−1. Such a satisfactory electrochemical performance was due to several factors of the Fe3O4/C composite beads including high theoretical capacity of Fe3O4, nanosized active Fe3O4 particles, hollow porous structure that mitigated the volume change problem, and carbon coating layer that enhanced both the electronic conductivity and structure integrity.

Synthesis and characterization of AgInS2–ZnS heterodimers with tunable photoluminescence

AgInS2–ZnS nanoparticles with well-defined heterodimer structures were synthesized using a hot injection method. The emission spectra of the obtained heterodimers under UV excitation could be tuned by controlling the diffusion of Zn in AgInS2. The ZnS component in the heterodimers played an important role in improving quantum yield. The obtained heterodimers demonstrated two photon fluorescence properties. The cell imaging applications of the obtained heterodimers excited by either UV or infrared were demonstrated.

Synthesis of CuInS2–ZnS alloyed nanocubes with high luminescence

CuInS(2)-ZnS alloyed nanocubes with high luminescence were synthesized through a solution-based diffusion method.

Ordered mesoporous carbon nanoparticles with well-controlled morphologies from sphere to rod via a soft-template route

A facile soft-template method is used to synthesize highly ordered mesoporous carbon nanoparticles (MCNs) with well-controlled morphology from spherical to rod-like structures. Low-molecular-weight phenolic resol is used as carbon-yielding component and triblock copolymer Pluronic F127 as pore-forming component. The morphology of nanoparticles could be tuned by well controlling the concentration of F127. The results show that rod-shaped and worm-like mesoporous carbon nanoparticles can be obtained when the concentration of F127 is set at ~12 wt.% and 9 wt.%, respectively. The spherical nanoparticles are obtained when the concentration is reduced to 6 wt.%, and their size can be adjusted by further decreasing the F127 concentration. Moreover, the highly ordered mesostructure can be readily turned from 2D hexagonal (p6m) to 3D caged cubic (Im ̅3m) along with the tuning of morphologies from rod-shaped to spherical. The as-obtained MCNs exhibit large surface area (~1385 m(2)/g), high pore volume (~0.919 cm(3)/g), highly ordered mesostructure, and continuous electron transport framework. Hence, the obtained mesoporous carbon materials show excellent capacitance (~142 F/g at loading current density of 0.5A/g) in the application of supercapacitors.

Role of carbon coating in improving electrochemical performance of Li-rich Li(Li0.2Mn0.54Ni0.13Co0.13)O2 cathode

Li-rich Li(Li0.2Mn0.54Ni0.13Co0.13)O2 cathode coated with carbon layer has been prepared by a hydrothermal approach followed by a post annealing process. The cathode after surface modification exhibits both enhanced cyclability and improved rate capability compared with the pristine one without coating. The carbon coating process causes a phase transformation from Li2MnO3-like domain to cubic-spinel domain with Fdm symmetry at surface regions of particles. As a consequence, the valence state of Mn on the surface accordingly varies. Such transformed surface spinels, as well as the wrapped carbon layers as a result of this coating strategy are believed to be responsible for the enhanced electrochemical performance.

Synthesis of AIZS@SiO2 core–shell nanoparticles for cellular imaging applications

I–III–VI2 semiconductor nanoparticles such as AgInS2 have been developed for cell imaging applications in recent years. However, there are few published works reporting the phase transfer (from hydrophobic to hydrophilic) of the AgInS2 nanoparticles for biomedical application purposes. In this work, we report the successful silica coating for the as-synthesized Zn-doped AgInS2 (AIZS) nanoparticlesvia a templated coating route. The silica shell thickness of the obtained AIZS@SiO2 core–shell nanoparticles could be well controlled within 10–20 nm and their overall size was less than 50 nm. As compared to the AIZS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB), the obtained AIZS@SiO2 nanoparticles showed much improved photoluminescence (PL) stability in water. The obtained core–shell nanoparticles were further conjugated with the PEG functional group, and the resultant PEGylated nanoparticles showed excellent colloidal stability in various media such as water, phosphate buffered saline (PBS) and bovine calf serum (BCS). The cellular imaging application of the obtained AIZS@SiO2 nanoparticles was also demonstrated successfully.

Synthesis of poly(acrylic acid) (PAA) modified Pluronic P123 copolymers for pH-stimulated release of doxorubicin.

Pluronic P123 was chain-extended at their terminal groups using atom transfer radical polymerization to form poly(acrylic acid) (PAA) tails and obtain the PAA-b-P123-b-PAA (P123-PAA) copolymer. The incorporation of PAA had the effect of increasing the carriers drug loading capacity of an anti-cancer drug, Doxorubicin (DOX), and also allowed for pH-controlled release of the drug. Drug release assays showed that up to 60% of DOX cargo could be retained in the DOX/P123-PAA complex for 3 days at normal physiological pH (7.4). This was then followed by a secondary burst release of DOX when the environment became more acidic (pH 5). Therefore, it was possible that the more acidic physiological environment of tumor sites could be used to trigger an accelerated release of DOX from the drug carriers. The material was demonstrated for potential application in the delivery of cationic drugs for cancer treatment.

Synthesis and properties of Au–Fe3O4 heterostructured nanoparticles

Au-Fe(3)O(4) composite nanoparticles have received much research interest due to their promising biomedical applications. In this work, Au-Fe(3)O(4) composites with well-defined dimer-like nanostructure were synthesized via thermal decomposition route. The surfactant 1,2-hexandicandiol has proved to be critical for the formation of the Au-Fe(3)O(4) hetero-dimers. The hetero-dimers production yield could be significantly improved to be 90% when the 1,2-hexandicandiol concentration was optimized at 0.6 M. The obtained Au-Fe(3)O(4) hetero-dimers possess dual-functionalities of plasmon resonance and magnetization. Moreover, the Fe(3)O(4) domain of the hetero-dimers can be tuned readily by adjusting the molar ratio between Fe and Au sources. Furthermore, it was demonstrated that these Au-Fe(3)O(4) hetero-dimers could be further developed into star-like Au-Fe(3)O(4) nanoparticles which showed plasmon absorption at NIR region.