Zhelin Liu

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.

Preparation and enhanced electrocatalytic activity of graphene supported palladium nanoparticles with multi-edges and corners

Herein, we reported a facile and green synthesis of palladium nanoparticles with a concave and convex surface formed by multi-edges and corners only involving palladium precursor and ascorbic acid. Ascorbic acid was employed as both reductant and structure-directing agent. The as-prepared palladium nanoparticles were then assembled on reduced graphene oxide. The morphology and chemical composition of the products were confirmed by several characterization techniques. The fast development of fuel cells inspired us to examine the electrocatalytic activity of the products towards methanol, ethanol and formic acid electrooxidation in alkaline medium comparing with that of the commercial one. The characterization and electrochemical results were carefully analyzed and discussed, showing the product can be applied as a well-performed electrocatalyst towards the electrooxidation of methanol, ethanol, and formic acid in alkaline media. The possible electron transfer route was proposed with the assistance of MedeA VASP calculation.

One-step synthesis of flower-shaped WO3 nanostructures for a high-sensitivity room-temperature NOx gas sensor

In this work, we report a one-step synthesis of spherical flower-shaped tungsten oxide (WO3) nanostructures by using polyethylene glycol (PEG) as a surfactant. The PEG played a crucial role in controlling the final morphology of the WO3 product. The structure and morphology of the product were characterized by carrying out XRD and SEM experiments. These characterizations indicated these three-dimensional flower-shaped nanostructures to be well crystallized, to have a uniform morphology with an average diameter of 3 μm, and to consist of many two-dimensional nanosheets. The flower-shaped WO3 particles exhibited excellent room-temperature NOx gas-sensing performance, including a sensitivity as high as 80%, a short response time of 4.5 s to 97 ppm NOx, and a low detection limit of 970 ppb. The excellent performance was due to the structure and morphology of the WO3 product.

Reduced graphene oxide-mediated synthesis of Mn3O4 nanomaterials for an asymmetric supercapacitor cell

Herein, Mn3O4/reduced graphene oxide composites are prepared via a facile solution-phase method for supercapacitor application. Transmission electron microscopy results reveal the uniform distribution of Mn3O4 nanoparticles on graphene layers. The morphology of the Mn3O4 nanomaterial is changed by introducing the reduced graphene oxide during the preparation process. An asymmetric supercapacitor cell based on the Mn3O4/reduced graphene oxide composite with the weight ratio of 1 : 1 exhibits relatively superior charge storage properties with higher specific capacitance and larger energy density compared with those of pure reduced graphene oxide or Mn3O4. More importantly, the long-term stability of the composite with more than 90.3% capacitance retention after 10 000 cycles can ensure that the product is widely applied in energy storage devices.

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.

Highly Active PdNi/RGO/Polyoxometalate Nanocomposite Electrocatalyst for Alcohol Oxidation

A PdNi/RGO/polyoxometalate nanocomposite has been successfully synthesized by a simple wet-chemical method. Characterizations such as transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, and X-ray photoelectron spectroscopy are employed to verify the morphology, structure, and elemental composition of the as-prepared nanocomposite. Inspired by the fast-developing fuel cells, the electrochemical catalytic performance of the nanocomposite toward methanol and ethanol oxidation in alkaline media is further tested. Notably, the nanocomposite exhibits excellent catalytic activity and long-term stability toward alcohol electrooxidation compared with the PdNi/RGO and commercial Pd/C catalyst. Furthermore, the electrochemical results reveal that the prepared nanocomposite is attractive as a promising electrocatalyst for direct alcohol fuel cells, in which the phosphotungstic acid plays a crucial role in enhancing the electrocatalytic activities of the catalyst.

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.