Photocontrollable water permeation on the micro/nanoscale hierarchical structured ZnO mesh films

Most research of responsive surfaces mainly focus on the wettability transition on different solid substrate surfaces, but the dynamic properties of the micro/nanostructure-enhanced responsive wettability on microscale pore arrays are lacking and still remain a challenge. Here we report the photocontrollable water permeation on micro/nanoscale hierarchical structured ZnO-coated stainless steel mesh films. Especially, for aligned ZnO nanorod array-coated stainless steel mesh film, the film shows good water permeability under irradiation, while it is impermeable to water after dark storage. A detailed investigation indicates that the special nanostructure and the appropriate size of the microscale mesh pores play a crucial role in the excellent controllability over water permeation. The excellent controllability of water permeation on this film is promising in various important applications such as filtration, microreactor, and micro/nano fluidic devices. This work may provide interesting insight into the design of novel functional devices that are relevant to surface wettability.     

Fracture toughness and surface morphology of micro/nano sized fibrils-modified epoxy resin

Two kinds of micro/nano sized fibrils based on cellulose (MFC) and polyvinyl alcohol (PVA) were used as reinforcer for epoxy resin (EP) with different contents in the range from 0 to 0.3 wt %. PVA nanofibers with diameter about 40–80 nm were fabricated by electrospinning technique. The analysis of mechanical properties showed that by both adding MFC and PVA to EP the fracture toughness was increased. The SEM results showed that micro/nano sized fibers dispersed throughout epoxy resin, prevented and changed the path of crack growth.     

Non-equilibrium electrokinetic micro/nano fluidic mixer

We propose a new type of micro/nano fluidic mixer based on non-equilibrium electrokinetics and demonstrate its mixing performance. We fabricate the device with two-step reactive ion etching, one for nanochannels and one for microchannels. Mixing is achieved by strong vortex structures formed near the micro/nano channel interface. We expect the proposed device to be beneficial in the development of micro total analysis systems, since it is simple in its design with minimal fabrication complications.     

Dielectrophoresis for manipulation of micro/nano particles in microfluidic systems

Dielectrophoretic (DEP) force is exerted when a neutral particle is polarized in a non-uniform electric field, and depends on the dielectric properties of the particle and the suspending medium. The integration of DEP and microfluidic systems offers numerous applications for the separation, trapping, assembling, transportation, and characterization of micro/nano particles. This article reviews the applications of DEP forces in microfluidic systems. It presents the theory of dielectrophoresis, different configurations, and the applications of such systems for particle manipulation and device fabrication.     

Photoluminescence investigations of ZnO micro/nanostructures

Zinc oxide (ZnO) is probably one of the most researched wide bandgap semiconductors in the last decades due to its unique characteristics in terms of low production cost, high availability, bioinertness, and especially its interesting optical properties. Although this semiconductor is considered an ‘old’ material and is known to possess such unique properties for more than three decades, the interest was renewed because of the advances in nanotechnology and the possibility to be produced in a vast number of nanostructures with tunable properties. An adequate knowledge of the nanomaterials’ optical response is mandatory for assessing and optimizing their functionalities towards different applications. Although the photoluminescence properties of ZnO bulk materials have been known from several decades, quite a number of open questions remains, namely regarding the nature of defects responsible for the broad luminescence bands frequently observed in the visible spectral region. With the effects of reducing the dimensionality of the material to the nanoscale, changes may arise in the luminescence outcome due to the role of the surface/interface characteristics. Indeed, the surface phenomena can strongly affect the nanostructure properties and can be used to tailor them, consequently having a profound influence on the performance of the devices where the nanostructures are employed. Hence, in this article, an overview of the fundamental properties of ZnO, with emphasis on the main optical recombination mechanisms, both in bulk and at the nanoscale, is provided to disclose some of the current knowledge in this subject. In addition, some examples of the myriad of applications where this semiconductor has been exploited are also discussed.     

Hierarchical micro/nano porous silicon Li-ion battery anodes

A wet-chemical etching method is reported for the scale-up preparation of carbon-coated hierarchical micro/nano porous silicon powders as a Li-ion battery anode, which shows no capacity fading at 1500 mA h g(-1) in 50 charge/discharge cycles.     

Structural,optical and photoelectron spectroscopic studies of nano/micro ZnO:Cd rods synthesized via sol-gel route

Thin films of cadmium doped zinc oxide rod like microstructure have been synthesized by a very simple sol-gel dip coating technique. Sols were prepared from hydrated zinc oxide precursor and 2-methoxyethanol solvent with monoethanolamine as a sol stabilizer. XRD pattern confirmed the hexagonal wurtzite structure of the deposited ZnO films. Surface morphologies of the films have been studied by a scanning electron microscope and an atomic force microscope, which confirmed that the films are composed of densely packed randomly oriented nano/submicron rods with diameter in the range 300–400 nm having various lengths. We proposed a possible growth mechanism for this rodlike structure. X-ray photoelectron spectroscopic study was used to determine the binding energies and the Zn 2p3/2, Cd 3d5 and O 1s peaks in the XPS spectra were located at 1021.08 eV, 404.6 eV and 529.8 eV respectively, which confirmed the Cd doping in ZnO. Cadmium content in the film was estimated both from energy dispersive X-ray analysis and XPS measurement. Band gap energy determined from optical transmittance spectra systematically varied from 3.28 eV to 3.15 eV for 0% to 5.6% of Cd doping. Urbach parameter determined from the band tail of the transmittance spectra showed that it increased with doping percentage and this parameter for a fixed cadmium doping level decreased with increase of temperature.     

Hierarchical structured CoP nanosheets/carbon nanofibers bifunctional eletrocatalyst for high-efficient overall water splitting

The design of efficient,stable,and economical electrocatalysts for oxygen and hydrogen evolution reaction(OER and HER)is a major challenge for overall water splitting.Herein,a hierarchical structured CoP/carbon nanofibers(CNFs)composite was successfully synthesized and its potential application as a high-efficiency bifunctional electrocatalyst for overall splitting water was evaluated.The synergetic effect of two-dimensional(2D)CoP nanosheets and on e-dimensi on al(1D)CNFs endowed the CoP/CNFs composites with abundant active sites and rapid electron and mass transport pathways,and thereby significantly improved the electrocatalytic performances.The optimized CoP/CNFs delivered a current density of 10 mA cm^-2 at low overpotential of 325 mV for OER and 225 mV for HER.In the overall water splitting,CoP/CNFs achieved a low potential of 1.65 V at 10 mA cm^-2.The facile strategy provided in the present work can facilitate the design and development of multifunctional non-noble metal catalysts for energy applications.     

Size effect on thermodynamic parameters for the peanut-like CaMoO4 micro/nano reaction systems

Peanut-like CaMoO₄ micro/nano structures with three different sizes were harvested by a simple reverse-microemulsion method at room temperature. Employing synthesized micro/nano CaMoO₄ and HCl as reaction systems, thermodynamic parameters such as standard molar enthalpy of reaction Δ_r H _m ^θ , standard molar Gibbs free energy of activation Δ _r ^≠ G _m ^θ , standard molar enthalpy of activation Δ _r ^≠ H _m ^θ , and standard molar entropy of activation Δ _r ^≠ S _m ^θ were successfully acquired for the first time by in situ microcalorimetry. Furthermore, change regularities of the thermodynamic parameters for the micro/nano reaction systems were obtained and discussed. It demonstrated that size effect has significant influence on thermodynamic parameters of micro/nano material reaction systems.     

纳米氧化锌及负载沸石的抗菌性能研究

霉变是引起饲料变质的主要因素.目前已知污染饲料的产毒霉菌约100多种,可产生200多种霉菌毒素,其中,黄曲霉菌产生的有毒代谢物黄曲霉毒素（AFT）已成为世界很多地区的主要问题.实践证明,最有效的办法之一是在饲料中添加防霉物质即防霉剂.丙酸盐对于霉菌、酵母菌及细菌具有广泛的抗菌作用,尤其是对黄曲霉等抑制作用比山梨酸钾和苯甲酸钠盐都要强得多,生产成本又较低.因此,早在五、六十年代就已被大多数发达国家作为最重要、最广泛的食品防腐剂使用.但是丙酸受热损失大,不适合制粒,挥发快,防霉持续期比较短,易受钙盐中和而造成活力损失.丙酸腐蚀性强,有刺激性气味,也影响饲料适口性,而且饲料需要在一定的酸性条件下才能发挥防霉的功效[1].由此可见,丙酸类防霉剂有着很多的缺陷,亟待更替.     

Enantioseparation/Recognition based on nano techniques/materials

Enantiomers show different behaviors in interaction with the chiral environment. Due to their identical chemical structure and their wide application in various industries, such as agriculture, medicine, pesticide, food, and so forth, their separation is of great importance. Today, the term “nano” is frequently encountered in all fields. Technology and measuring devices are moving towards miniaturization, and the usage of nanomaterials in all sectors is expanding substantially. Given that scientists have recently attempted to apply miniaturized techniques known as nano-liquid chromatography/capillary-liquid chromatography, which were originally accomplished in 1988, as well as the widespread usage of nanomaterials for chiral resolution (back in 1989), this comprehensive study was developed. Searching the terms “nano” and “enantiomer separation” on scientific websites such as Scopus, Google Scholar, and Web of Science yields articles that either use miniaturized instruments or apply nanomaterials as chiral selectors with a variety of chemical and electrochemical detection techniques, which are discussed in this article.     

银基微纳米半导体光催化应用研究进展

综述了银基微纳米半导体光催化应用研究进展.指出银基微纳米半导体在可见光辐照下表现出良好的光催化性能(光催化降解有机物或光解水制氢制氧),目前的研究主要集中在简单的含银化合物、含银的异质结构、含银的多金属氧化物和含银的固溶体这几类;并从光催化原理和能隙调节手段入手阐述了决定其光催化性能的因素.     

Green synthesis of graphene nanosheets/ZnO composites and electrochemical properties

A green and facile approach was demonstrated to prepare graphene nanosheets/ZnO (GNS/ZnO) composites for supercapacitor materials. Glucose, as a reducing agent, and exfoliated graphite oxide (GO), as precursor, were used to synthesize GNS, then ZnO directly grew onto conducting graphene nanosheets as electrode materials. The small ZnO particles successfully anchored onto graphene sheets as spacers to keep the neighboring sheets separate. The electrochemical performances of these electrodes were analyzed by cyclic voltammetry, electrochemical impedance spectrometry and chronopotentiometry. Results showed that the GNS/ZnO composites displayed superior capacitive performance with large capacitance (62.2 F/g), excellent cyclic performance, and maximum power density (8.1 kW/kg) as compared with pure graphene electrodes. Our investigation highlight the importance of anchoring of small ZnO particles on graphene sheets for maximum utilization of electrochemically active ZnO and graphene for energy storage application in supercapacitors.     

Hierarchical micro/nano structures of carbon composites as anodes for microbial fuel cells

We demonstrate the utility of hierarchical micro/nano structures of electrically conductive carbon composites as anodes for microbial fuel cells (MFCs). To construct the hierarchical structures, carbon nanotubes (CNTs) were directly grown on micro-porous graphite felts at high densities. Using the CNT-modified felts as anodes, power outputs from MFCs were increased ～7 fold compared to those with bare graphite-felt anodes. We also show that this power improvement is sustainable even in MFCs operated with naturally occurring microbial communities. These results suggest the wide utility of the hierarchical micro/nano structures of conductive carbon composites for bio-electrochemical processes.     

Facile fabrication of superhydrophobic surface from micro/nanostructure metal alkanethiolate based films

A series of superhydrophobic surfaces with micro/nanostructure have been successfully achieved by a simple process via the reaction between metal (such as Cd and Zn) salts and alkanethiolates.     

Heterostructures of NiFe LDH hierarchically assembled on MoS2 nanosheets as high-efficiency electrocatalysts for overall water splitting

Typically, rational interfacial engineering can effectively modify the adsorption energy of active hydrogen molecules to improve water splitting efficiency. NiFe layered double hydroxide (NiFe LDH) composite, an efficient oxygen evolution reaction (OER) catalyst, suffers from slow hydrogen evolution reaction (HER) kinetics, restricting its application for overall water splitting. Herein, we construct the hierarchical MoS₂/NiFe LDH nanosheets with a heterogeneous interface used for HER and OER. Benefiting the hierarchical heterogeneous interface optimized hydrogen Gibbs free energy, tens of exposed active sites, rapid mass- and charge-transfer processes, the MoS₂/NiFe LDH displays a highly efficient synergistic electrocatalytic effect. The MoS₂/NiFe LDH electrode in 1 mol/L KOH exhibits excellent HER activity, only 98 mV overpotential at 10 mA/cm². Significantly, when it assembled as anode and cathode for overall water splitting, only 1.61 V cell voltage was required to achieve 10 mA/cm² with excellent durability (50 h).     

Amorphous porous sulfides nanosheets with hydrophilic/aerophobic surface for high-current-density water splitting

The rational construction of electrocatalysts with desired features is significant but challenging for superior water splitting at high current density. Herein, amorphous CoNiS nanosheets are synthesized on nickel foam (NF) through a facile structure evolution strategy and present advanced performance at high current densities in water splitting. The high catalytic activity can be attributed to the sufficient active sites exposed by the flexible amorphous configuration. Moreover, the hydrophilicity and aerophobicity of a-CoNiS/NF promote surface wettability of the self-supporting electrode and avoid the aggregation of bubbles, which expedites the diffusion of electrolyte and facilitates the mass transfer. As a result, the optimized electrode demonstrates low overpotentials of 289 and 434 mV at 500 mA/cm² under alkaline conditions for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Impressively, an electrolytic water splitting cell assembled by bifunctional a-CoNiS/NF operates with a low cell voltage of 1.46 V@10 mA/cm² and reaches 1.79 V at 500 mA/cm². The strategy sheds light on a competitive platform for the reasonable design of non-precious-metal electrocatalysts under high current density.     

Size effect on thermodynamic properties of CaMoO4 micro/nano materials and reaction systems

CaMoO₄ micro/nano hollow spheres with three different sizes were prepared via a reverse-microemulsion route at room temperature. Through designing a novel thermochemical cycle, the relationship between thermodynamic properties of nano CaMoO₄ and bulk CaMoO₄ was built. Combined with in situ microcalorimetry, change regularities for the thermodynamic properties of the prepared CaMoO₄ micro/nano materials and reaction systems were obtained. The results reveal that size effect has significant influence on thermodynamic properties of micro/nano materials and reaction systems. Along with the size decreasing, the standard molar enthalpy, standard molar Gibbs free energy and standard molar entropy of reaction of micro/nano reaction systems decreased, but the standard molar enthalpy of formation, standard molar Gibbs free energy of formation and standard molar entropy of micro/nano materials increased.