Xinlu Wang

Novel construction technique, structure and photocatalysis of Y2O2CN2 nanofibers and nanobelts

Y2O3 nanofibers and nanobelts were fabricated by calcination of the respective electrospun PVP/Y(NO3)3 composite nanofibers and nanobelts. For the first time, Y2O2CN2 nanofibers and nanobelts were successfully prepared via cyanamidation of the respective Y2O3 nanofibers and nanobelts employing NH3 gas and using graphite boat as container at 950 °C. X-ray power diffraction (XRD) analysis reveals that Y2O2CN2 nanofibers and nanobelts are pure trigonal phase with the space group of Pm1. Scanning electron microscope (SEM) observation indicates that the diameter of Y2O2CN2 nanofibers is 167.59 ± 31.19 nm, and the thickness and width of Y2O2CN2 nanobelts are respectively 154 nm and 2.02 ± 0.84 μm under the 95% confidence level. Fourier transform infrared spectroscopy (FTIR) analysis manifests that the trigonal Y2O2CN2 nanofibers and nanobelts contain CN22− ions. Brunauer–Emmett–Teller surface area (BET) measurement shows the surface areas of the Y2O2CN2 nanofibers and nanobelts are 19.13 m2 g−1 and 15.92 m2 g−1, respectively. Y2O2CN2 nanostructures with different morphology exhibit high-efficiency photocatalytic capacity in photodegradation of rhodamine B (RhB) under the ultraviolet light irradiation, and the nanofibers have higher photocatalytic ability than nanobelts under the same experimental conditions. Furthermore, the nanofibers and nanobelts retain excellent photocatalytic stability after reused for four times. The photocatalytic mechanism and formation process of Y2O2CN2 nanofibers and nanobelts are also provided.

An In2O3 nanorod-decorated reduced graphene oxide composite as a high-response NOx gas sensor at room temperature

A novel composite room temperature gas sensor based on an In2O3 nanorod-decorated reduced graphene oxide composite (In2O3 NR/rGO composite) was successfully synthesized via a facile reflux method. In this synthesis, In3+ and urea were adsorbed on GO through electrostatic interactions in a water solution. The subsequent reflux treatment led to the transformation of the In(OH)3 nanorods coated on GO and also to the reduction of graphene oxide. We demonstrate that the composite can detect NOx gas with a response of 1.45, a fast response time of 25.0 s for 97.0 ppm NOx and a low detection limit of 970 ppb at room temperature. Compared with the pure In2O3 NRs, the composite has a faster response within 30.0 s over the whole range of NOx concentration. The enhanced sensing properties are attributed to the synergy of the superior conductivity of rGO and the nanostructure of the In2O3 NR/rGO composite. The present strategy for combining various hydroxide and nanoscale building blocks into integrated 3D structures will open new opportunities for designing and synthesizing multifunctional composites.

Electrospun Li2MnO3-modified Li1.2NixCo0.1Mn0.9-xO2 nanofibers: Synthesis and enhanced electrochemical performance for lithium-ion batteries

The Li2MnO3-modified Li1.2NixCo0.1Mn0.9-xO2 (x = 0.2, 0.45, 0.7) as cathode materials for lithium-ion batteries have been successfully synthesized by a simple electrospinning process. The structure, morphology and electrochemical performances of the resulting products are studied systematically. The as-prepared Li2MnO3-modified Li1.2NixCo0.1Mn0.9-xO2 (x = 0.2, 0.45, 0.7) with a diameter of 200-300 nm has an initial discharge capacity of 168.740 mAh·g−1, coulombic efficiency of 99.6% and a reversible capacity as high as 139.016 mAh·g−1 after 200 cycles at a current rate of 0.2 C. The excellent electrochemical performances of which are attributed to the stabilization of Li2MnO3 structure, the role of Li2MnO3 is contribute extra lithium to the reversible capacity and to facilitate Li+ transport through the structure.

In situ synthesis of homogeneous Ce2S3/MoS2 composites and their electrochemical performance for lithium ion batteries

Homogeneous Ce2S3/MoS2 composite have been fabricated via an in situ sulfurization method and their structure, morphology and electrochemical properties are researched systematically for the first time. Ce2S3/MoS2 composite present spherical secondary particles of 0.5–1 μm in diameter. The cycling performance and rate property of Ce2S3/MoS2 composite are better than those of Ce2S3 and MoS2 as anode materials for lithium ion batteries. Among them, Ce2S3/MoS2 composite (cationic ratio of Ce : Mo in 4 : 1) have an initial discharge capacity of 225.5 mA h g−1, a coulombic efficiency of 99.1% and a reversible capacity as high as 661.7 mA h g−1, a coulombic efficiency of 99.7% after 500 cycles at a current density of 100 mA g−1 and the highest discharge capacity of 285.6 mA h g−1 at a high current density of 1000 mA g−1, showing the best cycling performance and rate capability among the as-prepared Ce2S3/MoS2 composite. The reason is that the compositing between MoS2 and Ce2S3 can maintain the stability of the structure during the charge/discharge process and the existence of Ce2S3 enhances the electrical conductivity of Ce2S3/MoS2 composite and further improves the reversible capacities and rate performance of Ce2S3/MoS2 composite.

Assembly of 1D coaxial nanoribbons into 2D multicolor luminescence array membrane endowed with tunable anisotropic electrical conductivity and magnetism via electrospinning

A flexible 2D color-tunable coaxial nanoribbon array membrane with anisotropic electrical conductivity and magnetism assembled by 1D coaxial nanoribbons is obtained via coaxial electrospinning technology using a specially designed coaxial spinneret. Each coaxial nanoribbon in the array is composed of an Fe3O4 nanoparticle (NPs)/polymethyl methacrylate (PMMA) magnetic core and [Eu(TTA)3(TPPO)2 + Tb(TTA)3(TPPO)2]/polyaniline (PANI)/PMMA [TTA = 2-thenoyltrifluoroacetone radical, TPPO = tris(N,N-tetramethylene)phosphoric acid triamide] conductive photoluminescent shell, and the array membrane is formed by aligned coaxial nanoribbons. Tunable colors ranging from green to red can be achieved in the coaxial nanoribbon array membrane by modulating the mass ratio of Eu(TTA)3(TPPO)2, Tb(TTA)3(TPPO)2, PANI and Fe3O4 NPs. Additionally, other functions such as magnetism and anisotropic electrical conductivity are conveniently exhibited by the coaxial nanoribbon array membrane to realize multifunctionality. The ratio of the conductivity parallel and perpendicular to the length direction of the nanoribbons is as high as five due to the unique nanostructure of the array membrane. Also, the magnetic performance, electrical conductivity and electrically conductive anisotropy of the coaxial nanoribbon array membrane can be tuned by modulating the contents of PANI and Fe3O4 NPs. The coaxial nanoribbon array membrane exhibits a much better luminescent performance and electrically conductive anisotropy than its counterpart composite nanoribbon array membrane. Furthermore, the design philosophy and synthetic method for the flexible coaxial nanoribbon array membrane provide a new and facile strategy for the preparation of color-tunable 2D nanomaterials with multifunctionality.

Au-doped Li1.2Ni0.7Co0.1Mn0.2O2 electrospun nanofibers: synthesis and enhanced capacity retention performance for lithium-ion batteries

The Au-doped Li1.2Ni0.7Co0.1Mn0.2O2 (Au = 0%, 1%, 2%, 3%, 4%) nanofibers are successfully prepared by electrospinning technology. The impact of Au doping on the structure, morphology and electrochemical properties of samples is studied in detail. The X-ray diffraction patterns demonstrate that appropriate Au-doping does not significantly change the structure of Li1.2Ni0.7Co0.1Mn0.2O2. Scanning electron microscope images revealed the electrospun nanofibers have uniform particle size in the range of 300–400 nm. The optimum doping amount of Au is 2% in Li1.2Ni0.7Co0.1Mn0.2O2 to obtain high discharge capacity and excellent capacity retention. Electrochemical impedance spectroscopy test results elucidated that the LNCMA-2% cell has excellent Li+ electrical conductivity and lower charge transfer resistance. The results show that stable structure with good particle contact of the Au-doped cathode materials can enhance electrochemical properties, which can be interpreted as an important inhibition of phase transitions and increased charge transfer impedance during cycling.

Novel double anisotropic conductive flexible composite film endued with improved luminescence

Brand-new double anisotropic conductive flexible composite films (ACFs) were firstly put forward, devised and fabricated. The flexible array composite films were constructed via electrospinning using highly aligned Janus nanoribbons as conductive and constitutive units. The Janus nanoribbon consists of two parts, which are respectively conducting side and insulating-luminescent side. The Janus nanoribbons array composite film has two layers, and the two layers are combined tightly to form a top-to-bottom structure. In the composite film, the length direction of the Janus nanoribbons (namely conducting direction) in the two layers is perpendicular, so that a composite film with double electrically conductive anisotropy is achieved. In addition, by adjusting the content of PANI, conductive anisotropy of each layer of the composite film can be tuned, and the conductance in the conducting direction is about 108 times stronger than that in the insulating direction. The Janus nanoribbon array composite films also have tunable and improved luminescent properties, achieving bi-functionality of double anisotropically electrical conduction and luminescence. The proposed design concept and preparation technology will provide theoretical and technical support for the design and fabrication of novel multifunctional ACFs.

Novel flexible coaxial nanoribbons arrays to help achieve tuned and enhanced simultaneous multicolor luminescence–electricity–magnetism trifunctionality

Flexible color-tunable coaxial nanoribbons array endowed with electricity and magnetism is obtained via coaxial electrospinning. Every single coaxial nanoribbon is composed of Fe3O4 nanoparticles (NPs)/polyaniline(PANI)/polymethylmethacrylate (PMMA) conductive-magnetic bifunctional core and [Eu(TTA)3(TPPO)2+Tb(TTA)3(TPPO)2]/PMMA [TTA = 2-Thenoyltrifluoroacetone radical, TPPO = tris(N,N-tetramethylene)phosphoric acid triamide] insulative-photoluminescent shell. In the coaxial nanoribbons array, the fluorescent color is adjustable in the range of green–yellow–red via modulating the mass ratios of RE(TTA)3(TPPO)2, (RE = Eu, Tb), PANI and Fe3O4 NPs, and changing excitation wavelength. The coaxial nanoribbons array possesses more excellent luminescent performance than the counterpart composite nanoribbons array. For the core of coaxial nanoribbons, the highest electrical conductivity reaches 3.152 × 10−2 S cm−1. Magnetism and electricity of the coaxial nanoribbons array can be tuned. Design philosophy and fabrication method provide a novel and facile strategy toward other nanomaterials with multifunctionality.

Impact of pH on Morphology and Electrochemical Performance of LiFePO4 as Cathode for Lithium-ion Batteries

Lithium-ion battery cathode material LiFePO4 particles were synthesized by sol-gel method. The impact of pH value on morphology and electrochemical performance of LiFePO4 particles have been investigated. Results show that as pH value increased, the particle sizes of LiFePO4 are reduced, and its particle sizes distribution are narrowed. The LiFePO4 particles synthesized with a high pH value contains hierarchically organized pores, yielding a high discharge capacity of 129.02 mAh/g at 0.2 C and a stable capacity retention of 91.71% until 20 electrochemical cycles.