Showing papers by "Harbin Engineering University published in 2012"
TL;DR: In this paper, a high-voltage asymmetric supercapacitor is successfully fabricated using Ni(OH)2/graphene and porous graphene as the positive and negative electrodes, respectively.
Abstract: Hierarchical flowerlike nickel hydroxide decorated on graphene sheets has been prepared by a facile and cost-effective microwave-assisted method. In order to achieve high energy and power densities, a high-voltage asymmetric supercapacitor is successfully fabricated using Ni(OH)2/graphene and porous graphene as the positive and negative electrodes, respectively. Because of their unique structure, both of these materials exhibit excellent electrochemical performances. The optimized asymmetric supercapacitor could be cycled reversibly in the high-voltage region of 0–1.6 V and displays intriguing performances with a maximum specific capacitance of 218.4 F g−1 and high energy density of 77.8 Wh kg−1. Furthermore, the Ni(OH)2/graphene//porous graphene supercapacitor device exhibits an excellent long cycle life along with 94.3% specific capacitance retained after 3000 cycles. These fascinating performances can be attributed to the high capacitance and the positive synergistic effects of the two electrodes. The impressive results presented here may pave the way for promising applications in high energy density storage systems.
1,808 citations
TL;DR: This review highlights the most recent research progress on silica-based controlled drug delivery systems, including pure mesoporous silica sustained-release systems, magnetism and/or luminescence functionalized mesoporus silica systems which integrate targeting and tracking abilities of drug molecules.
Abstract: In the past decade, non-invasive and biocompatible mesoporous silica materials as efficient drug delivery systems have attracted special attention. Great progress in structure control and functionalization (magnetism and luminescence) design has been achieved for biotechnological and biomedical applications. This review highlights the most recent research progress on silica-based controlled drug delivery systems, including: (i) pure mesoporous silica sustained-release systems, (ii) magnetism and/or luminescence functionalized mesoporous silica systems which integrate targeting and tracking abilities of drug molecules, and (iii) stimuli-responsive controlled release systems which are able to respond to environmental changes, such as pH, redox potential, temperature, photoirradiation, and biomolecules. Although encouraging and potential developments have been achieved, design and mass production of novel multifunctional carriers, some practical biological application, such as biodistribution, the acute and chronic toxicities, long-term stability, circulation properties and targeting efficacy in vivo are still challenging.
1,233 citations
TL;DR: In this article, the maximum reflection loss reached −45.1 dB with a thickness of the absorber of only 2.5 mm, and the Debye relaxation processes in graphene/polyaniline nanorod arrays are improved compared to polyanilines nanorods.
Abstract: In the paper, we find that graphene has a strong dielectric loss, but exhibits very weak attenuation properties to electromagnetic waves due to its high conductivity. As polyaniline nanorods are perpendicularly grown on the surface of graphene by an in situ polymerization process, the electromagnetic absorption properties of the nanocomposite are significantly enhanced. The maximum reflection loss reaches −45.1 dB with a thickness of the absorber of only 2.5 mm. Theoretical simulation in terms of the Cole–Cole dispersion law shows that the Debye relaxation processes in graphene/polyaniline nanorod arrays are improved compared to polyaniline nanorods. The enhanced electromagnetic absorption properties are attributed to the unique structural characteristics and the charge transfer between graphene and polyaniline nanorods. Our results demonstrate that the deposition of other dielectric nanostructures on the surface of graphene sheets is an efficient way to fabricate lightweight materials for strong electromagnetic wave absorbents.
443 citations
01 Nov 2012
TL;DR: The main purpose of this survey is to extensively identify existing methods and characterize the literature in a manner that brings key challenges to attention.
Abstract: Modeling human behaviors and activity patterns for recognition or detection of special event has attracted significant research interest in recent years. Diverse methods that are abound for building intelligent vision systems aimed at scene understanding and making correct semantic inference from the observed dynamics of moving targets. Most applications are in surveillance, video content retrieval, and human-computer interfaces. This paper presents not only an update extending previous related surveys, but also a focus on contextual abnormal human behavior detection especially in video surveillance applications. The main purpose of this survey is to extensively identify existing methods and characterize the literature in a manner that brings key challenges to attention.
440 citations
TL;DR: In this article, a high-performance supercapacitor with high specific capacitance of 349 Fg−1 at 2mV−s−1 was obtained for the HCGS electrode in 6m KOH aqueous solution.
409 citations
TL;DR: The excellent electromagnetic absorption properties with lightweight and wide absorption frequency band are realized by the nanocomposites.
Abstract: This paper presents for the first time a successful synthesis of quaternary nanocomposites consisting of graphene, Fe3O4@Fe core/shell nanopariticles, and ZnO nanoparticles. Transmission electron microscopy measurements show that the diameter of the Fe3O4@Fe core/shell nanoparitcles is about 18 nm, the Fe3O4 shell’s thickness is about 5 nm, and the diameter of ZnO nanoparticles is in range of 2–10 nm. The measured electromagnetic parameters show that the absorption bandwidth with reflection loss less than −20 dB is up to 7.3 GHz, and in the band range more than 99% of electromagnetic wave energy is attenuated. Moreover, the addition amount of the nanocomposites in the matrix is only 20 wt %. Therefore, the excellent electromagnetic absorption properties with lightweight and wide absorption frequency band are realized by the nanocomposites.
340 citations
TL;DR: A hierarchical porous Ni(OH)2/graphene composite as a electrode material for supercapacitors displays ultrahigh specific capacitance, superior cycling performance, and excellent rate capability as mentioned in this paper.
Abstract: Hierarchical porous Ni(OH)2 nanoflakes anchored on graphene sheets has been fabricated by a facile chemical precipitation approach. The as-prepared Ni(OH)2/graphene composite as a electrode material for supercapacitors displays ultrahigh specific capacitance, superior cycling performance, and excellent rate capability. A maximum specific capacitance of 2194 F g−1 could be obtained at 2 mV s−1 in 6 M KOH aqueous solution. Meanwhile, the electrode exhibits excellent long cycle life along with 95.7% specific capacitance retained after 2000 cycle tests. Such composite is a highly promising candidate as electrode material for broad applications in energy conversion/storage systems.
257 citations
255 citations
TL;DR: In this paper, the etching of graphene sheets by MnO2 has been used to synthesize porous graphene nanosheets (PGNs) with a specific capacitance of 154 F g−1 at 500 mV−s−1 in 6M KOH.
252 citations
TL;DR: The present study may provide a promising alternative for complete dehalogenation of most HOCs and reductive detoxification of numerous toxicants.
Abstract: Most halogenated organic compounds (HOCs) are toxic and persistent, and their efficient destruction is currently a challenge. Here, we proposed a sulfite/UV (253.7 nm) process to eliminate HOCs. Monochloroacetic acid (MCAA) was selected as the target compound and was degraded rapidly in the sulfite/UV process. The degradation kinetics were accelerated proportionally to the increased sulfite concentration, while the significant enhancement by increasing pH only occurred in a pH range of 6.0–8.7. The degradation proceeded via a reductive dechlorination mechanism induced by hydrated electron (eaq–), and complete dechlorination was readily achieved with almost all the chlorine atoms in MCAA released as chloride ions. Mass balance (C and Cl) studies showed that acetate, succinate, sulfoacetate, and chloride ions were the major products, and a degradation pathway was proposed. The dual roles of pH were not only to regulate the S(IV) species distribution but also to control the interconversion between eaq– and H...
220 citations
TL;DR: In this article, the performance of nanostructured CuO on copper foam was investigated by cyclic voltammetry, galvanostatic charge/discharge measurements and electrochemical impedance spectroscopy.
01 Feb 2012
TL;DR: The results showed that Pb( II) and Cu(II) removal was strongly pH-dependent with an optimum pH value of 6.0, and the equilibrium time was 3.0 h.
Abstract: The adsorption of Pb(II) and Cu(II) from aqueous solution on magnetic porous ferrospinel MnFe(2)O(4) prepared by a sol-gel process was investigated. Single batch experiment was employed to test pH effect, sorption kinetics, and isotherm. The interaction mechanism and the regeneration were also explored. The results showed that Pb(II) and Cu(II) removal was strongly pH-dependent with an optimum pH value of 6.0, and the equilibrium time was 3.0 h. The adsorption process could be described by a pseudo-second-order model, and the initial sorption rates were 526.3 and 2631.5 μmol g(-1)min(-1) for Pb(II) and Cu(II) ions, respectively. The equilibrium data were corresponded well with Langmuir isotherm, and the maximum adsorption capacities were 333.3 and 952.4 μmol g(-1) for Pb(II) and Cu(II) ions, respectively. The adsorbed Pb(II) and Cu(II) ions were in the form of the complex with oxygen in carboxyl and hydroxyl groups binding on the surface of magnetic porous MnFe(2)O(4). The sorbent could be reused for five times with high removal efficiency.
TL;DR: In this article, the removal behaviors of Cu(II) and Pb(II)-Ions onto GNS/MnO 2 adsorbent were investigated under various conditions including contact time and initial metal concentrations, and surface interactions involved in the adsorption process and regeneration were also explored.
TL;DR: In this paper, a revised sliding mode control (SMC) law is proposed for robust tracking control of an underactuated surface vessel with parameter uncertainties. But the authors believe that their theory formulation involves essential flaws and propose a new revised SMC law under the same assumptions.
Abstract: This study concerns the robust tracking control problem for an underactuated surface vessel with parameter uncertainties. In recent work by McNinch and collegeaues, a sliding mode control (SMC) law is presented and experimentally implemented for trajectory tracking of an underactuated autonomous surface vessel. The authors believe, however, their theory formulation involves essential flaws. Motivated by the obtained result by McNinch and collegeaues, a new revised SMC law is proposed under the same assumptions. The control law is similarly developed by introducing a first-order sliding surface in terms of surge tracking errors and a second-order surface in terms of lateral motion tracking errors; however, the desired surge and sway velocities are presented as a new form to guarantee the convergence of position tracking errors. Simulation results are provided to validate their method.
TL;DR: In this paper, an acoustic absorbing foam material was produced from polyurethane (PU) with addition of water as a blowing agent and OR-501 as open pore cell agent.
TL;DR: In this article, a surfactant-free molten salt method for the first time was used to obtain one-dimensional NaLuF4:Yb3+,Er3+/Tm3++/Ho3+ microtubes and microrods.
Abstract: Well-defined one-dimensional NaLuF4:Yb3+,Er3+/Tm3+/Ho3+ microtubes and microrods were successfully prepared by a surfactant-free molten salt method for the first time. It is found that with the prolonged time, the phase of NaLuF4 transforms from cubic to hexagonal, while the morphology changes from nanoparticles to microtubes then to microrods. Moreover, upon 980 nm laser diode (LD) excitation, white up-conversion (UC) light was successfully achieved by properly tuning the sensitizer (Yb3+) concentration in the host matrix. The relative emission intensities of different emission colors in Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+ doped β-NaLuF4 can be precisely adjusted in a broad range by tuning the Yb3+ doping concentration. Consequently, effective UC emissions with multicolors and a strong white light can be realized in β-NaLuF4:Yb3+/Er3+/Tm3+, and β-NaLuF4:Yb3+/Tm3+/Ho3+ structures by the appropriate control of the emission intensity balance for the three blue, green, and red basic colors. UC mechanisms in the co-doping and tri-doping β-NaLuF4 samples were analyzed in detail based on the emission spectra and the plot of luminescence intensity to pump power. The as-obtained abundant luminescence colors in a much wide region contribute themselves great potential applications in various fields. Furthermore, the paper also provides an effective and facile approach to gain a desired color by manipulating the sensitizer concentration.
TL;DR: In this article, the effect of adsorption parameters such as pH value, adsorbent dose, shaking time, and temperature has been investigated and optimized for removing uranium(VI) ions from aqueous solutions.
TL;DR: In this article, a concentrated ammonia-assisted hydrothermal method was developed to obtain N-doped graphene sheets by simultaneous doping and reduction of graphene oxide (GO) sheets.
TL;DR: It is proposed that Ni( 2+) transferred electron from the surface to induce ozone decomposition in the catalytic process, the oxidation of lattice oxygen played an essential role in enhancing the reversion of Ni(3+) to Ni(2+), and the promotion of (*)OH reaction was a combined balance action of Ni (2+)/Ni( 3+) and O(2-)/O(2).
TL;DR: The results indicate the promise of using NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers as multi‐functional drug carriers for drug delivery and cell imaging.
Abstract: Up-conversion (UC) luminescent and porous NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers are prepared by electrospinning process. The biocompatibility test on L929 fibrolast cells reveals low cytotoxicity of the fibers. The obtained fibers can be used as anti-cancer drug delivery host carriers for investigation of the drug storage/release properties. Doxorubicin hydrochloride (DOX), a typical anticancer drug, is introduced into NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers (denoted as DOX-NaYF4:Yb3+, Er3+@SiO2). The release properties of the drug carrier system are examined and the in vitro cytotoxicity and cell uptake behavior of these NaYF4:Yb3+, Er3+@SiO2 for HeLa cells are evaluated. The release of DOX from NaYF4:Yb3+, Er3+@SiO2 exhibits sustained, pH-sensitive release patterns and the DOX-NaYF4:Yb3+, Er3+@SiO2 show similar cytotoxicity as the free DOX on HeLa cells. Confocal microscopy observations show that the composites can be effectively taken up by HeLa cells. Furthermore, the fibers show near-infrared UC luminescence and are successfully applied in bioimaging of HeLa cells. The results indicate the promise of using NaYF4:Yb3+, Er3+@SiO2 nanocomposite fibers as multi-functional drug carriers for drug delivery and cell imaging.
TL;DR: In this paper, a reduced graphene nanosheet/urchin-like manganese dioxide (GNS/MnO 2 ) composite for a supercapacitor electrode has been fabricated by a mild hydrothermal route.
TL;DR: In this paper, a nanostructured MnO 2 /GNS composite was used as an alternative cathode catalyst for oxygen reduction reaction in air-cathode microbial fuel cell (MFC).
TL;DR: In this article, an analysis of the intense blue upconversion emission at 476 and 488 nm in Tm 3+ /Yb 3+ codoped Y 2 O 3 under excitation power density of 86.7 W/cm 2 available from a diode laser emitting at 976-nm, has been undertaken.
TL;DR: Aiming at the chattering problem which is caused by sliding mode control item, a switch gain adjust method based on exponential function is proposed, which proves that the trajectory tracking error of the underwater robot control system is uniformly ultimately bounded through Lyapunov theory.
TL;DR: In this paper, the authors highlight the recent advances on the preparation, characteristics and application of one-dimensional (1D) luminescent materials (including rare earth based inorganic materials, rare earth-based composite materials and non rare earth materials) by an electrospinning process.
Abstract: This feature article highlights the recent advances on the preparation, characteristics and application of one-dimensional (1D) luminescent materials (including rare earth based inorganic materials, rare earth based composite materials and non rare earth materials) by an electrospinning process. Electrospinning is an effective method to prepare 1D polymer, composite and inorganic submicro- or nano-materials. The key strategy of the electrospinning method is to form an electrospinning solution with viscoelastic behavior similar to that of a conventional polymer solution. It utilizes an electrical force on the surface of an electrospinning solution to overcome the surface tension and produce a very thin charged jet. This jet moves straight for a certain distance, and then bends into looping and spiraling paths. During the elongation of the liquid jet, solvent evaporates and 1D hybrid materials accumulate on a grounded collector. Dispersing complexes or inorganic nanoparticles into polymer and inorganic matrices, composite luminescent materials viaelectrospinning combine both inorganic and organic characters. Annealing the inorganic/polymer hybrid precursors can yield various kinds of inorganic luminescent materials with fiber, wire, belt and tube-like morphologies, which have potential applications in fluorescent lamps and color displays. Furthermore, with the addition of some surfactants, it is possible to prepare 1D luminescent and porous multifunctional materials, which can act as potential drug carriers in the biomedical area.
TL;DR: In this paper, a facile microwave (MW) reflux method was used to obtain pure hexagonal NaYF4:Yb3+,Ln3+ (Ln 3+ = Er3+, Tm3+, Ho3+) crystals.
Abstract: Pure hexagonal NaYF4:Yb3+,Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) crystals were obtained for the first time through a facile microwave (MW) reflux method at relatively low temperature (160 °C) and atmospheric pressure within only 50 min. By controllably increasing the NH4F content in the ethylene glycol (EG) solvent, the phase of as-prepared NaYF4:Yb3+,Ln3+ gradually transforms from cubic to hexagonal. Correspondingly, the up-conversion (UC) emission intensities of hexagonal NaYF4:Yb3+,Ln3+ (Ln3+ = Er3+, Tm3+, Ho3+) are increased by 10–12 times compared to those of the cubic phase. A possible growth mechanism for the phase transformation under these MW conditions has been proposed. Moreover, for the first time, we introduced Bi3+ ion into β-NaYF4:20%Yb3+,2%Ln3+ crystals. As expected, the UC emission of β-NaYF4:Yb3+,Ln3+,Bi3+ are about 10–40 times higher than those of Bi3+ free samples. It is found that tri-doping of Bi3+ doesn't change the basic emission of Ln3+ ions. XRD results gives evidence that tri-doping of Bi3+ ions can tailor the local crystal field and dissociate the Yb3+ and Ln3+ ion clusters, which is the main reason for the UC enhancement. This designed MW reflux method for the synthesis of β-NaYF4:20%Yb3+,2%Ln3+ can be applied to prepare other rare earth fluorides. The markedly enhanced UC luminescence through Bi3+ doping also provides an effective way to gain very bright UC emission.
TL;DR: In this article, the removal of uranium ions from aqueous solution with a novel magnetic composite adsorbent, calcined magnetic layered double hydroxide/hydroxyapatite (CMLH), was reported.
TL;DR: The raw CM wires exhibited different phase transformation behavior and mechanical properties when compared with SE wires, attributing to the special heat treatment history of CM wires, suggesting greater flexibility of endodontic instruments manufactured with CM wires than similar instruments made of conventional SE wires.
TL;DR: The results imply that not only hollow nanostructures, but also a novel type of nanostructure can be fabricated by the present method for nanodevices.
Abstract: The paper describes for the first time the successful synthesis of Fe2O3/TiO2 tube-like nanostructures, in which TiO2 shell is of quasi-single crystalline characteristic and its thickness can be controlled through adjusting the added amount of aqueous Ti(SO4)2 solution. The characterization of samples obtained at different stages using transmission electron microscope indicates that the outer TiO2 shell is changed gradually from amorphous and polycrystalline phase into quasi-single crystal under thermal actions through the Ostwald ripening process, accompanying the corrosion of the central parts of Fe2O3 nanorods, and the formation of small particles separating each other, leading to the special core/shell nanorods. Furthermore, Fe2O3/TiO2 tube-like nanostructures can be transformed into Fe2TiO5 nanostructures after they are thermally treated at higher temperatures. Those nanostructures exhibit enhanced ethanol sensing properties with respect to the monocomponent. Our results imply that not only hollow na...
TL;DR: In this article, Fe-doped α-MoO3 micro-structures were fabricated by a hydrothermal method, in which the Fe doping amount was easily adjusted to be 0.3, 0.6,0.7 and 0.9% by only increasing the reaction time.
Abstract: Fe-doped α-MoO3 micro-structures were fabricated by a hydrothermal method, in which the Fe doping amount was easily adjusted to be 0.3, 0.6, 0.7 and 0.9 wt.% by only increasing the reaction time. X-ray diffraction and the energy dispersive spectroscopy analyses as well as the difference in the color between the doped and undoped samples provided the evidences for the Fe doping. It was also found that an appropriate Fe doping amount was beneficial to the improvement of H2S sensing performances. The enhanced gas sensing properties of the Fe-doped α-MoO3 sensors were attributed to the small size effect, catalytic effect of Fe dopants, surface reaction dynamics, and the increase in the resistance of the doped samples.