Femtosecond pulse laser-induced self-organized nanostructures on the surface of ZnO crystal

This paper reports self-organized nanostructures observed on the surface of ZnO crystal after irradiation by a focused beam of a femtosecond Ti：sapphire laser with a repetition rate of 250kHz. For a linearly polarized femtosecond laser, the periodic nanograting structure on the ablation crater surface was promoted. The period of self-organization structures is about 180 nm. The grating orientation is adjusted by the laser polarization direction. A long range Bragglike grating is formed by moving the sample at a speed of 10μm/s. For a circularly polarized laser beam, uniform spherical nanoparticles were formed as a result of Coulomb explosion during the interaction of near-infrared laser with ZnO crystal.

Ambient-Condition Strategy for Production of Hollow Ga_(2)O_(3)@rGO Crystalline Nanostructures Toward Efficient Lithium Storage

Crystallineγ-Ga_(2)O_(3)@rGO core-shell nanostructures are synthesized in gram scale,which are accomplished by a facile sonochemical strategy under ambient condition.They are composed of uniformγ-Ga_(2)O_(3)nanospheres encapsulated by reduced graphene oxide(rGO)nanolayers,and their formation is mainly attributed to the existed opposite zeta potential between the Ga_(2)O_(3)and rGO.The as-constructed lithium-ion batteries(LIBs)based on as-fabricatedγ-Ga_(2)O_(3)@rGO nanostructures deliver an initial discharge capacity of 1000 mAh g^(-1)at 100 mA g^(-1)and reversible capacity of 600 mAh g^(-1)under 500 mA g^(-1)after 1000 cycles,respectively,which are remarkably higher than those of pristineγ-Ga_(2)O_(3)with a much reduced lifetime of 100 cycles and much lower capacity.Ex situ XRD and XPS analyses demonstrate that the reversible LIBs storage is dominant by a conversion reaction and alloying mechanism,where the discharged product of liquid metal Ga exhibits self-healing ability,thus preventing the destroy of electrodes.Additionally,the rGO shell could act robustly as conductive network of the electrode for significantly improved conductivity,endowing the efficient Li storage behaviors.This work might provide some insight on mass production of advanced electrode materials under mild condition for energy storage and conversion applications.

Mass-Based Environmental Factor and Energy Assessment of Microwave-Assisted Synthesized Transition Metal Nanostructures

This paper describes mass-based energy phase-space projection of microwave-assisted synthesis of transition metals (zinc oxide, palladium, silver, platinum, and gold) nanostructures. The projection uses process energy budget (measured in kJ) on the horizontal axes and process density (measured in kJg−1) on the vertical axes. These two axes allow both mass usage efficiency (Environmental-Factor) and energy efficiency to be evaluated for a range of microwave applicator and metal synthesis. The metrics are allied to the: second, sixth and eleventh principle of the twelve principle of Green Chemistry. This analytical approach to microwave synthesis (widely considered as a useful Green Chemistry energy source) allows a quantified dynamic environmental quotient to be given to renewable plant-based biomass associated with the reduction of the metal precursors. Thus allowing a degree of quantification of claimed “eco-friendly” and “sustainable” synthesis with regard to waste production and energy usage.

Equilibrium reconstruction method for self-organized plasmas on reversed field pinches with polarimeter-interferometer

In the reversed field pinch(RFP),plasmas exhibit various self-organized states.Among these,the three-dimensional(3D)helical state known as the“quasi-single-helical”(QSH)state enhances RFP confinement.However,accurately describing the equilibrium is challenging due to the presence of 3D structures,magnetic islands,and chaotic regions.It is difficult to obtain a balance between the available diagnostic and the real equilibrium structure.To address this issue,we introduce KTX3DFit,a new 3D equilibrium reconstruction code specifically designed for the Keda Torus eXperiment(KTX)RFP.KTX3DFit utilizes the stepped-pressure equilibrium code(SPEC)to compute 3D equilibria and uses polarimetric interferometer signals from experiments.KTX3DFit is able to reconstruct equilibria in various states,including axisymmetric,doubleaxis helical(DAx),and single-helical-axis(SHAx)states.Notably,this study marks the first integration of the SPEC code with internal magnetic field data for equilibrium reconstruction and could be used for other 3D configurations.

Triangular Au-Ag framework nanostructures prepared by multi-stage replacement and their spectral properties

Triangular Au-Ag framework nanostructures （TFN） were synthesized via a multi-step galvanic replacement reaction （MGRR） of single-crystalline triangular silver nanoplates in a chlorauric acid （HAuCl4） solution at room temperature. The morphological, compositional, and crystal structural changes involved with reaction steps were analyzed by using transmission electron microscopy（TEM）, energy-dispersive X-ray spectrometry （EDX）, and X-ray diffraction. TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. The in-plane dipolar surface plasmon resonance （SPR） absorption band of the Ag nanoplates locating initially at around 700 nm gradually redshifted to 1 100 nm via a multi-stage replacement manner after 7 stages. The adding amount of HAuCl4 per stage influenced the average redshift value per stage, thus enabled a fine tuning of the in-plane dipolar band. A proposed formation mechanism of the original Ag nanoplates developing pores while growing Au nanoparticles covering this underlying structure at more reaction steps was confirmed by exploiting surface-enhanced Raman scattering （SERS）.

Fabrication of Silicon Crystal-Facet-Dependent Nanostructures by Electron-Beam Lithography

Silicon crystal-facet-dependent nanostructures have been successfully fabricated on a （100）-oriented silicon-oninsulator wafer using electron-beam lithography and the silicon anisotropic wet etching technique. This technique takes advantage of the large difference in etching properties for different crystallographic planes in alkaline solution. The minimum size of the trapezoidal top for those Si nanostructures can be reduced to less than 10nm. Scanning electron microscopy （SEM） and atomic force microscopy （AFM） observations indicate that the etched nanostructures have controllable shapes and smooth surfaces.

Controllable Electrochemical Synthesis of Silver Dendritic Nanostructures and Their SERS Properties

Ag dendritic nanostructures were synthesized on fluorine-doped tin oxide covered glass sub- strates by the electrodeposition method. Results demonstrate that the size, diameter, crys- tallinity, and branch density of the Ag dendrites can be controlled by the applied potential, the surfactants and the concentration of AgNO3. Three kinds of typical silver dendrites were applied as substrates of the surface enhanced Raman scattering （SERS） and one of them was able to clearly detect rhodamine 6G concentrations up to 0.1 nmol/L. The differences of the SERS spectra at these Ag dendrites confirmed that the shapes and interparticle spacings have great effect on Raman enhancement, especially the interparticle spacings.

Controlled synthesis of one-dimensional Au-Ag porous nanostructures

The fabrication of a new type of one-dimensional Au-Ag porous nanotube（NPT） structure was presented based on a facile combination of nanocrystal growth and surface modification.Ag nanowires with various diameters were firstly served as the chemical plating templates via a polyol-process.Then,one-dimensional（1D） Au-Ag porous nanostructures with tailored structural features could be prepared by controlling the individual steps involved in this process,such as nanowire growth,surface modification,thermal diffusion,and dealloying.Structural characterizations reveal these Au-Ag porous nanotubes,non-porous nanotubes and porous nanowires possess novel nano-architectures with multimodal open porosity and excellent structural continuity and integrity,which make them particularly desirable as novel 1D nanocarriers for biomedical,drug delivery and sensing applications.

Fabrication and Photocatalysis of TiO2 Flower-like Nanostructures

TiO2 nanostructures were fabricated by a reaction of Ti foils in H2O2 solution at mild temperature, Porous TiO2 nanostructurcs, well adhered to Ti foil surfaces, were formed at 80 ℃ in 10 rain, and then flower- like and rod nanostructures formed in succession after a longer reaction time. Samples prepared at 80 ℃ for 4 h arc amorphous, and anatase-dominated crystal phase emerged in the sample prepared for as long as 10 h. Almost pure anatase phase were obtained in TiO2 nanostructures by annealing the samples at a temperature of 300 ℃. Photoeatalysis of the TiO2 nanostructures was characterized by the degradation of RhB dye molecules in an aqueous solution exposed to ultraviolet light. Results show a 7 cm^2 annealed TiO2 flower-like nanostrueture having the degradation rate of RhB as fast as 29.8 times that of the dye solution exposed to ultraviolet light alone.

Zinc Oxide Nanostructures for NO_2 Gas–Sensor Applications:A Review

Because of the interesting and multifunctional properties,recently,ZnO nanostructures are considered as excellent material for fabrication of highly sensitive and selective gas sensors.Thus,ZnO nanomaterials are widely used to fabricate efficient gas sensors for the detection of various hazardous and toxic gases.The presented review article is focusing on the recent developments of NO2gas sensors based on ZnO nanomaterials.The review presents the general introduction of some metal oxide nanomaterials for gas sensing application and finally focusing on the structure of ZnO and its gas sensing mechanisms.Basic gas sensing characteristics such as gas response,response time,recovery time,selectivity,detection limit,stability and recyclability,etc are also discussed in this article.Further,the utilization of various ZnO nanomaterials such as nanorods,nanowires,nano-micro flowers,quantum dots,thin films and nanosheets,etc for the fabrication of NO2gas sensors are also presented.Moreover,various factors such as NO2concentrations,annealing temperature,ZnO morphologies and particle sizes,relative humidity,operating temperatures which are affecting the NO2gas sensing properties are discussed in this review.Finally,the review article is concluded and future directions are presented.

Synthesis and applications of MOF-derived porous nanostructures

Metal organic frameworks(MOFs) represent a class of porous material which is formed by strong bonds between metal ions and organic linkers. By careful selection of constituents, MOFs can exhibit very high surface area, large pore volume, and excellent chemical stability.Research on synthesis, structures and properties of various MOFs has shown that they are promising materials for many applications, such as energy storage, gas storage, heterogeneous catalysis and sensing. Apart from direct use, MOFs have also been used as support substrates for nanomaterials or as sacrificial templates/precursors for preparation of various functional nanostructures. In this review, we aim to present the most recent development of MOFs as precursors for the preparation of various nanostructures and their potential applications in energy-related devices and processes. Specifically, this present survey intends to push the boundaries and covers the literatures from the year 2013 to early 2017,on supercapacitors, lithium ion batteries, electrocatalysts, photocatalyst, gas sensing, water treatment, solar cells, and carbon dioxide capture.Finally, an outlook in terms of future challenges and potential prospects towards industrial applications are also discussed.

Kinetic study of methane hydrate formation in the presence of carbon nanostructures

The effect of synthesized nanostructures,including graphene oxide,chemically reduced graphene oxide with sodium dodecyl sulfate(SDS),chemically reduced graphene oxide with polyvinylpyrrolidone,and multi-walled carbon nanotubes,on the kinetics of methane hydrate formation was investigated in this work.The experiments were carried out at a pressure of 4.5 MPa and a temperature of 0 ℃ in a batch reactor.By adding nanostructures,the induction time decreases,and the shortest induction time appeares at certain concentrations of reduced graphene oxide with SDS and graphene oxide,that is,at a concentration of 360 ppm for reduced graphene oxide with SDS and 180 ppm for graphene oxide,with a 98% decrease in induction time compared to that in pure water.Moreover,utilization of carbon nanostructures increases the amount and the rate of methane consumed during the hydrate formation process.Utilization of multi-walled carbon nanotubes with a concentration of 90 ppm showes the highest amount of methane consumption.The amount of methane consumption increases by 173% in comparison with that in pure water.The addition of carbon nanostructures does not change the storage capacity of methane hydrate in the hydrate formation process,while the percentage of water conversion to hydrate in the presence of carbon nanotubes increases considerably,the greatest value of which occurres at a 90 ppm concentration of carbon nanotubes,that is,a 253% increase in the presence of carbon nanotubes compared to that of pure water.

One-Dimensional (1D) ZnS Nanomaterials and Nanostructures

One-dimensional （1D） nanomaterials and nanostructures have received much attention due to their potential interest for understanding fundamental physical concepts and for applications in constructing nanoscale electric and optoelectronic devices. Zinc sulfide （ZnS） is an important semiconductor compound of Ⅱ-Ⅵ group, and the synthesis of 1D ZnS nanomaterials and nanostructures has been of growing interest owing to their promising application in nanoscale optoelectronic devices. This paper reviews the recent progress on 1D ZnS nanomaterials and nanostructures, including nanowires, nanowire arrays, nanorods, nanobelts or nanoribbons, nanocables, and hierarchical nanostructures etc. This article begins with a survey of various methods that have been developed for generating 1D nanomaterials and nanostructures, and then mainly focuses on structures, synthesis, characterization, formation mechanisms and optical property tuning, and luminescence mechanisms of 1D ZnS nanomaterials and nanostructures. Finally, this review concludes with personal views towards future research on 1D ZnS nanomaterials and nanostructures.

Morphology and Crystallinity-controlled Synthesis of Manganese Cobalt Oxide/Manganese Dioxides Hierarchical Nanostructures for High-Performance Supercapacitors

We demonstrate a novel preparative strategy for the well-controlled MnCo_2O_(4.5)@MnO_2 hierarchical nanostructures.Bothδ-MnO_2 nanosheets andα-MnO_2 nanorods can uniformly decorate the surface of MnCo_2O_(4.5)nanowires to form core-shell heterostructures.Detailed electrochemical characterization reveals that MnCo_2O_(4.5)@δ-MnO_2 pattern exhibits not only high specific capacitance of 357.5 F g^(-1)at a scan rate of 0.5 A g^(-1),but also good cycle stability(97%capacitance retention after 1000 cycles at a scan rate of 5 A g^(-1)),which make it have a promising application as a supercapacitor electrode material.

Recent Advances in Visible-Light-Driven Photoelectrochemical Water Splitting: Catalyst Nanostructures and Reaction Systems

Photoelectrochemical(PEC) water splitting using solar energy has attracted great attention for generation of renewable hydrogen with less carbon footprint, while there are enormous challenges that still remain for improving solar energy water splitting efficiency, due to limited light harvesting, energy loss associated to fast recombination of photogenerated charge carriers, as well as electrode degradation. This overview focuses on the recent development about catalyst nanomaterials and nanostructures in different PEC water splitting systems. As photoanode, Au nanoparticle-decorated TiO_2 nanowire electrodes exhibited enhanced photoactivity in both the UV and the visible regions due to surface plasmon resonance of Au and showed the largest photocurrent generation of up to 710 nm. Pt/Cd S/CGSe electrodes were developed as photocathode. With the role of p–n heterojunction, the photoelectrode showed high stability and evolved hydrogen continuously for more than 10 days. Further, in the Z-scheme system(Bi_2S_3/TNA as photoanode and Pt/Si PVC as photocathode at the same time), a self-bias(open-circuit voltage Voc= 0.766 V) was formed between two photoelectrodes, which could facilitate photogenerated charge transfers and enhance the photoelectrochemical performance, and which might provide new hints for PEC water splitting. Meanwhile, the existing problems and prospective solutions have also been reviewed.

Synthesis, Optical Properties and Photovoltaic Application of the SnS Quasi-one-dimensional Nanostructures

Low-toxicity single crystal Sn S nanowires had been successfully synthesized by the catalystassistant chemical vapor deposition. Au nanoparticles were applied on the ITO surface as the catalysis, using Sn S powder and S powder as forerunners. The structure, morphology and optical properties of the prepared Sn S nanowires were characterized. The experimental results show the as-synthesized nanowires are single crystalline with a preferential orientation. The synthesized Sn S nanowires show strong absorption in the visible and nearinfrared spectral region, and the direct energy band gap of Sn S nanowires is 1.46 e V.

Strongly coupled N-doped carbon/Fe3O4/N-doped carbon hierarchical micro/nanostructures for enhanced lithium storage performance

A strong interface coupling is of vital importance to develop metal oxide/carbon nanocomposite anodes for next-generation lithium ion batteries.Herein,a rational N-doped carb on riveting strategy is designed to boost the lithium storage performance of Fe3O4/N-doped carbon tubular structures.Poly pyrrole(PPy)has been used as the precursor for N-doped carbon.N-doped carbon-riveted Fe3O4/N-doped carbon(N-C@Fe3O4@N-C)nanocomposites were obtained by pyrolysis of PPy-coated FeOOH@PPy nanotubes in Ar atmosphere.When tested as an anode for LIBs,the N-C@Fe3O4@N-C displays a high reversible discharge capacity of 675.8 mA h g-1 after 100 cycles at a current density of 100 mA g-1 and very good rate capability(470 mA h g_1 at 2 A g-1),which significantly surpasses the performance of Fe3O4@N-C.TEM analysis reveals that after battery cycling the FeOx particles detached from the carbon fibers for Fe3O4@N-C,while for N-C@Fe3O4@N-C the FeOx particles were still trapped in the carbon matrix,thus preserving good electrical contact.Consequently,the superior performance of N-C@Fe3C)4@N-C is attributed to the synergistic effect between Fe3O4 and N-doped carbon combined with the unique structure properties of the nanocomposites.The strategy reported in this work is expected to be applicable for designing other electrode materials for LIBs.

Band structure engineering in metal halide perovskite nanostructures for optoelectronic applications

Metal halide perovskite nanostructures have emerged as low-dimensional semiconductors of great significance in many fields such as photovoltaics,photonics,and optoelectronics.Extensive efforts on the controlled synthesis of perovskite nanostructures have been made towards potential device applications.The engineering of their band structures holds great promise in the rational tuning of the electronic and optical properties of perovskite nanostructures,which is one of the keys to achieving efficient and multifunctional optoelectronic devices.In this article,we summarize recent advances in band structure engineering of perovskite nanostructures.A survey of bandgap engineering of nanostructured perovskites is firstly presented from the aspects of dimensionality tailoring,compositional substitution,phase segregation and transition,as well as strain and pressure stimuli.The strategies of electronic doping are then reviewed,including defect-induced self-doping,inorganic or organic molecules-based chemical doping,and modification by metal ions or nanostructures.Based on the bandgap engineering and electronic doping,discussions on engineering energy band alignments in perovskite nanostructures are provided for building high-performance perovskite p-n junctions and heterostructures.At last,we provide our perspectives in engineering band structures of perovskite nanostructures towards future low-energy optoelectronics technologies.

Morphology dependent photocatalytic activity of WO_3 nanostructures

The shape of nanostructure has important effects on their properties, therefore in this study, we have prepared and characterized three different morphologies of WO_3 nanostructures i.e. nanorod, nanosphere and nanoplate for surveying shape effect on their photocatalytic properties toward degradation of Rhodamine B （RhB） dye. Obtained results show that nanoplate WO_3 in comparison with others has the best photocat- alytic activity. According to SEM, and photocatalytic degradation results, the reason for this behavior is the sharp edges and corners of WO_3 nanoplates. Because of their low coordination number, atoms located in the edges and comers of the WO_3 nanoplates have more activity, adsorb more RhB and therefore give more photocatalytic activity to the WO_3 nanoplates. Using of different scavengers showed that hydroxyl radicals are mainly responsible for photocatalytic activity of WO_3 nanoplates and nangspheres but for WO_3 nanorods, superoxide radicals are the main photocatalytic degradation agents.

Titania Nanostructures for Dye-sensitized Solar Cells

Titania is one kind of important materials, which has been extensively investigated because of its unique electronic and optical properties. Research efforts have largely focused on the optimization of the dye,but recently the titania nanostructures electrode itself has attracted more attention. It has been shown that particle size, shape, crystallinity, surface morphology, and chemistry of the TiO_2 material are key parameters which should be controlled for optimized performance of the solar cell. Titania can be found in different shape of nanostructures including mesoporous, nanotube, nanowire, and nanorod structures. The present article reviews the structural, synthesis, electronic, and optical properties of TiO_2 nanostructures for dye sensitized solar cells.