Ultrasmall SnFe2O4 nanoparticles anchored on N-doped carbon nanofibers for ultralight and high-performance microwave absorption.

One-dimensional (1D) N-doped carbon nanofibers decorated with ultrafine (∼4.5 nm) SnFe2O4 nanoparticles (denoted as SFO/N-CNFs) are successfully synthesized by a combination of electrospinning and solvothermal process, and their microwave absorption (MA) properties are reported for the first time. With only 5 wt% filler loading in a silicone rubber matrix, the optimum reflection loss (RL) could reach -46.5 dB and the qualified frequency bandwidth (RL < -10 dB) can be capable of 4.8 GHz at 1.6 mm, exhibiting better comprehensive absorption performance relative to other analogous absorbers. The lightweight and highly efficient MA of SFO/N-CNFs is largely ascribed to the improved impedance matching and satisfactory attenuation ability caused by the synergistic effect between the ultrasmall-sized SFO nanoparticles (NPs) and 1D N-CNF matrix. This work not only offers a novel and promising high-performance microwave absorber, but also offers a general approach to designing and fabricating ultrasmall transition metal oxide nanoparticle decorated carbon-based composite nanostructures for multifunctional applications.

Fe2P nanoparticle-decorated carbon nanofiber composite towards lightweight and highly efficient microwave absorption.

An Fe2P nanoparticle (Fe2P NP)-decorated carbon nanofiber (represented as Fe2P@CNF) composite was in situ prepared by electrospinning and subsequent high-temperature treatment. Benefitting from the synergy effect between Fe2P NPs and CNFs, as well as improved interface polarization and impedance matching, the Fe2P@CNF composite exhibits excellent microwave absorption performance relative to pure CNFs, in which the Fe2P@CNF composite with a fill loading of only 10 wt% possesses a minimum reflection loss (RL) of -49.2 dB at 3.0 mm and a maximum effective absorption bandwidth of 6.0 GHz at 2.2 mm. Therefore, this work provides a promising approach for the design and synthesis of an Fe2P@CNF composite with high-performance microwave absorption.

Enhanced electrochemical performances based on ZnSnO3 microcubes functionalized in-doped carbon nanofibers as free-standing anode materials.

The binary composite, ZnSnO3 microcubes (ZSO MC) homogeneously parceled in an N-doped carbon nanofiber membrane (ZSO@CNFM), was synthesized via a mild hydrothermal, electrospinning and carbonization process as a flexible lithium-ion battery (LIB) anode material. The unique carbon-coating layer architecture of ZSO@CNFM not only plays a crucial role in alleviating the volume change of ZSO MC during lithium ion insertion/extraction processes, but also constructs a three-dimensional (3D) transport network with the help of interconnected carbon nanofibers (CNFs) to ensure the structural integrity of the material and promote the electrochemical reaction kinetics. Due to its good flexibility characteristics, the as-prepared ZSO@CNFM can be directly adopted as an anode material for LIBs without the use of copper foil, conductive carbon black and any binder. Electrochemical surveying results manifest that the optimal ZSO@CNFM electrode displays excellent cycling stability (582.6 mA h g-1 after 100 lithiation/delithiation cycles at 100 mA g-1), high coulombic efficiency (CE, 99.6% at 100th cycles), and superior rate performance (349.5 mA h g-1 at 2 A g-1). The good electrochemical properties can be ascribed to the synergistic effect of the high theoretical specific capacity of ZSO MC, favourable stability of the carbon substrate, the open structure of ZSO@CNFM and the 3D continuous highly conductive framework for rapid electron/ion transfer.

Outstanding fluoride removal from aqueous solution by a La-based adsorbent.

A La-based adsorbent was prepared with La(NO3)3·6H2O, 2-methylimidazole and DMF via amide-hydrolysis and used for fluoride decontamination from aqueous water. The obtained adsorbent was lanthanum methanoate (La(COOH)3). The effects of pH value, initial F- concentration and interfering ions on defluoridation properties of as-prepared La(COOH)3 were assessed through batch adsorption tests. The adsorption kinetics, isotherm models and thermodynamics were employed to verify the order, nature and feasibility of La(COOH)3 towards fluoride removal. The results imply that La(COOH)3 is preferable for defluoridation over a wide pH range of 2 to 9 without interference. Simultaneously, the defluoridation process of La(HCOO)3 accords to the pseudo-second order model and Langmuir isotherm, revealing chemical adsorption is the main control step. The maximum fluoride capture capacities of La(COOH)3 at 30, 40 and 50 °C are 245.02, 260.40 and 268.99 mg g-1, respectively. The mechanism for defluoridation by La(COOH)3 was revealed by PXRD and XPS. To summarize, the as-synthesized La based adsorbent could serve as a promising adsorbent for defluoridation from complex fluoride-rich water.

Nickel nanoparticle decorated N-doped carbon nanofibers for light weight and high-efficiency microwave absorption.

Microwave absorbers with light weight and excellent microwave absorption performance are urgently needed in the microwave absorption field, which is still a challenge. Herein, N-doped carbon nanofibers decorated with nickel nanoparticles (Ni@CNFs) were synthesized by a facile electrospinning method combined with a two-step heat treatment, in which Ni nanoparticles are uniformly dispersed in carbon nanofibers. Benefitting from the special nanoarchitecture (including Ni nanoparticles encapsulated with graphitic carbon layers and carbon nanotube protrusions anchored on CNFs), three-dimensional conductive networks, the synergistic effect between suitable impedance matching and satisfactory electromagnetic (EM) attenuation ability, a superb comprehensive microwave absorption (MA) property is achieved for the optimal Ni@CNF sample with a rather low filler loading of 5 wt%. The optimal reflection loss (RL) reaches -66.3 dB at a small thickness of 3.1 mm and the maximum effective absorption bandwidth (EAB, RL < -10.0 dB) as wide as 4.56 GHz is obtained at 2.0 mm. This study demonstrates that the carefully designed Ni@CNF composites are superior to many previously reported magnetic carbon-based hybrid absorbers and can be applied as promising candidates for light weight and high-efficiency EM wave absorbers.

A novel three-dimensional Fe3SnC/C hybrid nanofiber absorber for lightweight and highly-efficient microwave absorption.

3D Fe3SnC/C hybrid nanofibers are proposed as a novel high-performance microwave absorber. At only 20 wt% filler loading, the optimal reflection loss reaches -119.2 dB at 17.1 GHz and the effective absorption bandwidth is 7.4 GHz with a thickness of 2.3 mm, outperforming most of the reported absorbers.

Research Progress on Skid Resistance of Basic Oxygen Furnace (BOF) Slag Asphalt Mixtures.

In order to ensure the safety of traffic, asphalt pavement is commonly required to utilize aggregates with excellent anti-abrasion property. This results in the lack of high-quality aggregates. The incorporation of solid waste in the aggregates is regarded as a high potential alternative for solving this problem. Since its material properties, such as rough surface, high Polished Stone Value (PSV) and the excellent adhesion property of asphalt, Basic Oxygen Furnace (BOF) slag can effectively improve the skid resistance of asphalt mixtures. First, the material properties of BOF slag are reviewed in this study. Then, the skid resistance of asphalt mixtures and aggregates are commendably evaluated by the Polished Stone Value test, Wehner/Schulze Tester, Aachen Polishing Machine, British Pendulum Test and Sand Patch test. The physical and mechanical properties of BOF slag play a key role in asphalt mixtures. This review found that the skid resistance mechanism of the BOF slag asphalt mixture is governed by factors such as BOF slag properties, incorporation methods and gradation types. Finally, the economic and environmental benefits of BOF slag asphalt mixtures were discussed. In addition, the function of gas catalysis and the melting of ice and snow can be added to the BOF slag asphalt mixture for a cleaner development in engineering. Furthermore, the existing problems, research directions and corresponding measures in this field are directed towards more durable and functional asphalt pavement construction.

Wide-Range Band-Gap Tuning and High Electrical Conductivity in La- and Pb-Doped SrSnO3 Epitaxial Films.

Perovskite oxide SrSnO3 has attracted considerable attentions recently due to its high carrier mobility and high transparency. Here, we experimentally and theoretically investigated the effects of La and Pb doping on the microstructure, band gaps, and electrical properties of SrSnO3 epitaxial thin films. X-ray diffraction analysis showed that the in-plane lattice constants of Pb-doped SrSnO3 (SrSn1-xPbxO3, x = 0-1, SSPO) films increased from 4.053 to 4.178 Å with the increase in Pb doping content. High-resolution transmission electron microscopy images revealed that SSPO films were coherently grown on LaAlO3(001) substrates. The optical band-gap values were considerably decreased gradually from 4.43 to 2.16 eV with Pb doping content while maintaining high optical transmittance in the visible wavelength range. Density functional theory calculations showed that the narrowing of band gap was attributed to a finite overlap between Pb 6s and Sn 5s orbitals around the bottom of the conduction band. As doping with 5% La in SSPO films, the electrical conductivity was improved greatly, and transport properties were investigated through temperature-dependent resistivity and Hall measurements. A lowest room-temperature resistivity of 0.5 mΩ cm and a maximum mobility of 39.9 cm2/Vs were observed in 5% La in the SSPO film at x = 1. Such wide-range tuning of the band gaps and excellent electrical properties of La- and Pb-doped SrSnO3 epitaxial thin films may provide promising applications in optoelectronic devices.

Ultrafine MoO2 nanoparticles encapsulated in a hierarchically porous carbon nanofiber film as a high-performance binder-free anode in lithium ion batteries.

Flexible free-standing hierarchically porous carbon nanofibers embedded with ultrafine (∼3.5 nm) MoO2 nanoparticles (denoted as MoO2@HPCNFs) have been synthesized by electrospinning and subsequent heat treatment. When evaluated as a binder-free anode in Li-ion batteries, the as-obtained MoO2@HPCNFs film exhibits excellent capacity retention with high reversible capacity (≥1055 mA h g-1 at 100 mA g-1) and good rate capability (425 mA h g-1 at 2000 mA g-1), which is much superior to most of the previously reported MoO2-based materials. The synergistic effect of uniformly dispersed ultrasmall MoO2 nanoparticles and a three-dimensionally hierarchical porous conductive network constructed by HPCNFs effectively improve the utilization rate of active materials, enhance the transport of both electrons and Li+ ions, facilitate the electrolyte penetration, and promote the Li+ storage kinetics and stability, thus leading to a greatly enhanced electrochemical performance.

Giant circular dichroism and its reversal in solid and inverse plasmonic gammadion-shaped structures.

Chiral plasmonic structures have been shown to possess large circular dichroism (CD) responses. Here, we investigate the CD responses in a solid and inverse metallic structure composed of a stacked right-twisted gammadion metallic nanoparticle and a left-twisted gammadion nanoaperture array, where a giant circular dichroism is achieved. In addition, the sign of the CD responses can be reversed through the changes of the geometric parameters. Further analysis reveals that the Fabry-Perot (F-P) resonance of cross-polarization conversion of electric field governs the change of the CD. It can be envisioned that our findings will allow further tuning and manipulation of the CD responses for tailored circular polarized light-matter interaction.

A contrastive analysis of laser heating between the human and guinea pig cochlea by numerical simulations.

BACKGROUND: The photo-thermal effect has been hypothesised to be one of the most possible biophysical mechanisms for laser-cochlea stimulation. However, there is a lack of studies to date for direct assessing laser heating in humans due to the large body of evidence required to demonstrate safety and efficacy. Instead, the majority focus on animals like the guinea pig, from which a number of valuable results have been gained. However, in light of the increasing need to improve laser safety, it has became necessary to find out whether studies on animals can shed light on safe laser parameters in the human cochlea. Hence, we conducted this contrastive analysis of laser heating between the human and guinea pig cochlea with the aim of assisting further investigations in this field. METHODS: In this work, a 3D symmetrical model was adopted to simplify the spiraled cochlea. With attention focused on the effect of heat conduction, the time-dependent heat equation was solved using finite element method with the COMSOL Script. In the simulations, cochleae with different sizes and various boundary thermal conditions were utilized. RESULTS: Laser heating in both cochleae has a similar trend. In the first stage, or at the beginning of the laser heating, both cochleae increased their temperatures rapidly. In the second stage in which the laser heating reached a quasi-steady stage, the peak temperatures began to rise slowly as more laser pulses were applied. However, three differences of the laser heating were observed. The first is regarding the temperature rise. The results show that laser heating in guinea pig is higher than that in human under the same laser parameters. The second difference is the fluctuation of temperature rise at the center of the modiolus. There is a larger fluctuation of temperature rise in the guinea pig cochlea, compared with that in the human cochlea. The third one is the time for reaching a steady thermal state. The results show that the guinea pig cochlea takes longer time to reach a steady thermal state than the human cochlea. Those differences are mainly attributed to the distinctive thermal boundaries and the various sizes of the two cochleae. CONCLUSIONS: This study finds that the laser heating in the guinea pig cochlea is higher than that in the human cochlea under the condition of the same laser parameters. However, laser stimulation still displays a high spatial selectivity in both cochleae despite the effects of heat conduction. The results indicate that experimental studies on the guinea pig could appropriately be an alternative model for the sake of laser safety.

[Progress and challenges in optical cochlear implant].

Optical cochlear implant has been occuring as a new cochlear implant which utilizes laser pulses to stimulate hearing. Compared to electronic cochlear implant, it has demonstrated higher spatial selectivity and less radiation scattering, which could lead to higher fidelity cochlear prostheses. At present, most investigations have focused on experiments in vivo. Although a lot of exciting results have been obtained, the mechanisms of laser stimulation is still open. In this paper, a brief review on the recent new findings of optical cochlear implant is given, and possible mechanisms are discussed. In the end, new experimental proposals are suggested which could help to explore the mechanisms of laser-cochlea stimulation.

Effects of heat conduction on the spatial selectivity of infrared stimulation in the cochlea.

BACKGROUND: It has been reported that one of the main mechanisms that induces the activation of the cochlea through infrared laser light is the photothermal effect. The temperature in the spiral ganglion cells increases as a result of photon absorption. However, heat conduction can induce an increase in the temperature within the cochlea and change the spatial selectivity of activation. METHODS: We analyzed the effects of heat conduction on the increase in temperature within the cochlea using a 3D model that simplifies the spiraled cochlea as a rotational symmetric structure . The model is solved using the finite element method. RESULTS: Taken as an example, the cochlea is stimulated by laser pulses at eight sites in its first turn. The temperature rise in time domain and spatial domain is simulated for different laser pulse energies and repetition rates. The results demonstrate that the temperature in the cochlea increases as the laser pulse energy and repetition rate increase. Additionally, the zone affected by the laser is enlarged because of the heat conduction in the surrounding structures. As a result, more auditory neurons can be stimulated than the expected. CONCLUSIONS: The heat conduction affects the laser spatial selectivity however, by adjusting the stimulation schemes of the laser pulse-trains, such as laser repetition rate and laser power, the laser selectivity can be optimized.

Hg(II)-activated emission "turn-on" chemosensors excited by up-conversion nanocrystals: synthesis, characterization and sensing performance.

In this paper, two emission "turn-on" chemosensors for Hg(II) sensing were designed and synthesized. Up-conversion NaYF4 nanocrystals were prepared and used as the excitation host for both chemosensors. Spectral analysis suggested that there should be an efficient energy transfer between the host and the chemosensors, which was then confirmed by excited state lifetime analysis. Then two sensing systems using this up-conversion host and the two chemosensors were constructed, their sensing performance for Hg(II) ions was then studied. It was found that the probe emission intensity increased with increasing Hg(II) concentrations, showing an emission "turn-on" effect. Good selectivity and linear response were observed from both sensing systems.

Optical cochlear implant: evaluation of insertion forces of optical fibres in a cochlear model and of traumata in human temporal bones.

Optical stimulation for hearing restoration is developing as an alternative therapy to electrical stimulation. For a more frequency-specific activation of the auditory system, light-guiding fibres need to be inserted into the coiled cochlea. To enable insertion with minimal trauma, glass fibres embedded in silicone were used as models. Thus, glass fibres of varying core/cladding diameter with and without silicon coating (single as well as in bundles) were inserted into a human scala tympani (ST) model. Insertion cochlear model force measurements were performed, and the thinner glass fibres that showed low insertion forces in the model were inserted into cadaveric human temporal bones. Silicone-coated glass fibres with different core/cladding diameters and bundle sizes could be inserted up to a maximum depth of 20 mm. Fibres with a core/cladding diameter of 50/55 µm break during insertion deeper than 7-15 mm into the ST model, whereas thinner fibres (20/25 µm) could be inserted in the model without breakage and in human temporal bones without causing trauma to the inner ear structures. The insertion forces of silicone-coated glass fibres are comparable to those measured with conventional cochlear implant (CI) electrodes. As demonstrated in human temporal bones, a minimal traumatic implantation of an optical CI may be considered feasible.

Enhanced rotation of the polarization of a light beam transmitted through a silver film with an array of perforated S-shaped holes.

In this Letter, we realized an enhanced optical rotation of the zero-order transmitted light through a silver film with an array of perforated S-shaped holes. Different from the previous studies, this effect results from the contribution of both the localized surface plasmons and surface plasmon polaritons (SPPs). The rotation angle can be modulated with the thickness due to the phase retardation of the SPPs when tunneling to the emitted surface. With a sample thickness 245 nm, a near-complete cross-polarization conversion (90° optical rotation) can be achieved, representing a major advance in performance compared to the previously reported planar chiral structures.

A novel experimental method for the local mechanical testing of human coronal dentin.

OBJECTIVES: The small volume of human dentin available for sample preparation and the local variations in its microstructure present a real challenge in the determination of their mechanical properties. The main purpose of the present study was to develop a new procedure for the preparation and mechanical testing of small-scale specimens of biomaterials such as dentin, so as to probe local mechanical properties as a function of microstructure. METHODS: Ultra short laser pulses were used to mill a block of dentin into an array of 16 microm size dentin pillars. These could then be individually tested in compression with an instrumented nanoindenter fitted with a 30 microm wide flat punch. RESULTS: The laser-based pillar preparation procedure proved effective and reliable. Data was produced for the mechanical properties of a first set of dry dentin micro-pillars. SIGNIFICANCE: This novel experimental approach enables the preparation and compression of micron-scale samples with well-defined microstructure. For dentin, this means samples containing a relatively small number of well-defined parallel tubules, with a distinct orientation relative to the applied load. The ability to isolate the separate effects of microstructural parameters on the mechanical properties is of major significance for future substantiation of theoretical models.

Green laser light activates the inner ear.

The hearing performance with conventional hearing aids and cochlear implants is dramatically reduced in noisy environments and for sounds more complex than speech (e. g. music), partially due to the lack of localized sensorineural activation across different frequency regions with these devices. Laser light can be focused in a controlled manner and may provide more localized activation of the inner ear, the cochlea. We sought to assess whether visible light with parameters that could induce an optoacoustic effect (532 nm, 10-ns pulses) would activate the cochlea. Auditory brainstem responses (ABRs) were recorded preoperatively in anesthetized guinea pigs to confirm normal hearing. After opening the bulla, a 50-microm core-diameter optical fiber was positioned in the round window niche and directed toward the basilar membrane. Optically induced ABRs (OABRs), similar in shape to those of acoustic stimulation, were elicited with single pulses. The OABR peaks increased with energy level (0.6 to 23 microJ/pulse) and remained consistent even after 30 minutes of continuous stimulation at 13 microJ, indicating minimal or no stimulation-induced damage within the cochlea. Our findings demonstrate that visible light can effectively and reliably activate the cochlea without any apparent damage. Further studies are in progress to investigate the frequency-specific nature and mechanism of green light cochlear activation.

Floating tip nanolithography.

We demonstrate noncontact, high quality surface modification of soft and hard materials with spatial resolution of approximately 20 nm. The nanowriting is based on the interaction between the surface and the tip of a standard atomic force microscope illuminated by a focused femtosecond laser beam and hovering (at ambient conditions) 1-4 nanometers above the surface without touching it. Field enhancement at the tip-sample gap or high tip temperature are identified as the causes of material ablation.