Xiyan Li

Green synthesis of Pt/CeO2/graphene hybrid nanomaterials with remarkably enhanced electrocatalytic properties

We developed a facile strategy for clean synthesis of Pt/CeO(2)/graphene nanomaterials with remarkably enhanced catalytic properties. The graphene oxide (GO) could be used as an oxidant to oxidize Ce(3+) into CeO(2) NPs, and l-lysine was used as a linker to realize the in situ growth of Pt NPs around CeO(2) NPs dispersed on graphene.

Selectively Deposited Noble Metal Nanoparticles on Fe3O4/Graphene Composites: Stable, Recyclable, and Magnetically Separable Catalysts

A simple, efficient, and general approach was developed to selectively deposit noble metal (Pt, Pd, or PtPd) nanoparticles 3-5 nm in size on magnetite/graphene composites. The biomolecule L-lysine with two kinds of functional groups (NH(2) and COOH) played the key role of connecter between noble metals and Fe(3)O(4)/graphene composites. These composites were characterized by TEM, XRD, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the noble metals are mostly dispersed on the magnetite surfaces of the composites. The as-obtained composites are ideal recyclable catalysts for liquid-phase reactions owing to their stability and efficient magnetic separation. Among these catalysts, the PtPd-based composites exhibited the highest activity and resistance to poisoning during the catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH(4). Such hybrid catalysts obtained by this simple, efficient method are expected to find use in industrial applications, where separation and recycling are critically required to reduce cost and waste production.

Hierarchically structured Fe3O4 microspheres: morphology control and their application in wastewater treatment

Novel three-dimensional (3D) flower-like Fe3O4 microspheres were synthesized by a facile precursor-templated conversion method. The precursor was prepared by an ultrasound-assisted hydrothermal method without the help of any surfactant. The possible formation mechanism of the precursor was proposed, and it was found that the synthetic parameters for the precursor such as the time of ultrasonic pretreatment and NH4Ac concentration are crucial for the formation of the flower-like hierarchical precursor structure. The flower-like Fe3O4 microspheres obtained by calcining the precursor in N2 exhibit superparamagnetic behaviour and show relative high saturation magnetization at room temperature. Furthermore, the as-obtained product, with high BET surface area, has been used as an absorbent in wastewater treatment and exhibit a strong capability to remove organic pollutants.

Bi2Te3 nanoplates and nanoflowers: Synthesized by hydrothermal process and their enhanced thermoelectric properties

Bi2Te3 nanoplates with a thickness of 15–20 nm and self-assembled flower-like nanostructures using previous nanoplates as building blocks have been fabricated through a low-cost hydrothermal method with ethylenediamine tetraacetic acid (EDTA) as an additive. The structures and morphologies of the samples were characterized viaX-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometry (FT-IR) and transmission electron microscope (TEM) measurements. The growth mechanisms have been proposed based on the experimental results. The nanoplates and flower-like Bi2Te3 nanocrystals (NCs) with no residual additives were consolidated by high pressure to an n-type nanostructured bulk material with preserved crystal grain sizes. Moreover, self-assembly NCs show higher thermoelectric properties than the nanoplates. The power factors and thermoelectric figure of merit (ZT) of chemically synthesized flower-like Bi2Te3 NCs were improved up to 8.6 μW cm−1K−2 and 0.7, respectively, which possess the potential to design new materials and devices for thermoelectric applications.

Direct hydrothermal synthesis of single-crystalline triangular Fe3O4 nanoprisms

Single-crystalline Fe3O4 triangular nanoprisms (TNPs) were fabricated by a facile hydrothermal route in the presence of 1,3-propanediamine (PDA). It was found that the EG to PDA volume ratio played an important role in the formation of the TNP structures and greatly affected the morphology of the magnetites.

Rhombic dodecahedral Fe3O4: ionic liquid-modulated and microwave-assisted synthesis and their magnetic properties

Rhombic dodecahedral (RD) Fe3O4 nanocrystals (NCs) were for the first time prepared via a rapid and facile microwave-assisted route in the presence of ionic liquids (ILs). The reaction could be finished within 15 min at temperatures as low as 90 °C. A proper amount of ILs played a key role in the synthesis of pure RD Fe3O4 NCs. In addition, the HMT-to-phenol molar ratio was also crucial for the growth of the RD Fe3O4 NCs. The phase structures, morphologies, and sizes of as-prepared products were investigated in detail by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM). The magnetic study reveals that the TB of the RD Fe3O4 NCs is found to be at 120 K, and the saturation magnetization is 86 emu g−1 at room temperature.

Hydrothermal synthesis and upconversion photoluminescence properties of lanthanide doped YF3 sub-microflowers

Yttrium fluoride sub-microflowers were synthesized by facile hydrothermal route without using any expensive or environmental unfriendly agents. The influences of various hydrothermal parameters on the final products were investigated. It was found that the concentration of NH3·H2O had a significant effect on the morphology change of YF3 sub-microcrystals. The growth mechanism of the as-obtained YF3 sub-microflowers was proposed. The multicolor upconversion (UC) photoluminescence (PL) was successfully realized in Yb3+/Tm3+, Yb3+/Ho3+ and Yb3+/Er3+ doped YF3 sub-microflowers when excited by 980 nm laser diode (LD). The pumping power dependence of the fluorescent intensity is investigated to understand the fundamental UC mechanism.

Multifunctional nanostructures based on porous silica covered Fe3O4@CeO2–Pt composites: a thermally stable and magnetically-recyclable catalyst system

A facile surface protected silica shell etching method for fabricating multifunctional Fe3O4@CeO2-Pt@mSiO2 composites is reported. These multifunctional materials possess large magnetization, open mesopores, and a stably confined but exposed catalytically active component. The unique structures showed high thermal stability, magnetic recyclability and catalytic activity in catalytic reactions.

Theoretical study on phosphorescence efficiency and color tuning from orange to blue-green of Ir(III) complexes based on substituted 2-phenylimidazo[1,2-a]pyridine ligand

The geometrical structures, phosphorescence quantum yields, and electroluminescence (EL) efficiency of six iridium(III) complexes containing 2‐phenylimidazo[1,2‐a]pyridine ligand are investigated by density functional theory (DFT), which show a wide color tuning of photoluminescence from orange (λem = 550 nm) to blue‐green (λem = 490 nm). The calculated results shed some light on the reasons of the remarkably manipulated excited‐state and EL properties through substitution effect. The Mulliken charge calculation reveals that attached CF3 groups on phenyl and imidazo[1,2‐a]pyridine (impy) moieties (4) can make both of them as electron‐deficient region, which will lead to the contraction of the whole coordination sphere and strengthen the metal–ligand interaction. While attaching two CF3 groups on phenyl ring can make it more electron‐deficient, which will induce electron transferring from acac and impy fragment to phenyl ring, and also result in the contracted structure. The largest metal‐to‐ligand charge transfer (3MLCT) character and the smaller S1–T1 energy gap (ΔES1−T1) value increase the emission quantum yields of 4 and 6 than other complexes. For EL efficiency, because of the similar highest occupied molecular orbital (HOMO) levels of 4 and 6 to that of holes injection material poly(N‐vinylcarbazole) (PVK) and the larger dipole moments, majority hole will be accumulated on the HOMO of 4 and 6. Combination with the lower lowest unoccupied molecular orbital energy levels compared with PVK, the recombination zones of 4 and 6 can be well confined within emitting material layer (EML) and lead to the higher EL efficiency.

Facile Synthesis and Thermoelectric Properties of Self‐assembled Bi2Te3 One‐Dimensional Nanorod Bundles

Self-assembled Bi(2)Te(3) one-dimensional nanorod bundles have been fabricated by a low-cost and facile solvothermal method with ethylene diamine tetraacetic acid as an additive. The phase structures and morphologies of the samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectrometry, and transmission electron microscope measurements. The growth mechanisms have been proposed based on the experimental results. The full thermoelectric properties of the nanorod bundles have been characterized and show a large improvement in the thermal conductivity attributed to phonon scattering of the nanostructures and then enhance the thermoelectric figure of merit. This work is promising for the realization of new types of highly efficient thermoelectric semiconductors by this method.