Naiqing Zhang

pH-Controllable On-Demand Oil/Water Separation on the Switchable Superhydrophobic/Superhydrophilic and Underwater Low-Adhesive Superoleophobic Copper Mesh Film

Recently, materials with controlled oil/water separation ability became a new research focus. Herein, we report a novel copper mesh film, which is superhydrophobic and superhydrophilic for nonalkaline water and alkaline water, respectively. Meanwhile, the film shows superoleophobicity in alkaline water. Using the film as a separating membrane, the oil/water separating process can be triggered on-demand by changing the water pH, which shows a good controllability. Moreover, it is found that the nanostructure and the appropriate pore size of the substrate are important for realization of a good separation effect. This paper offers a new insight into the application of surfaces with switchable wettability, and the film reported here has such a special ability that allows it to be used in other applications, such as sewage purification, filtration, and microfluidic device.

Mussel-inspired tailoring of membrane wettability for harsh water treatment

Novel hybrid coatings with excellent wettability are architecturally constructed on the surfaces of different types of separation membranes via simultaneous polymerization of mussel-inspired dopamine and hydrolysis of commercially available and low-cost silane through a highly efficient one-step approach. After coating with the designed hybrid coatings, the ultrafiltration (UF) membranes possess high hydrophilicity and excellent dry storage ability while the microfiltration (MF) membranes are endorsed with superhydrophilicity and underwater superoleophobicity. Such unique UF and MF membranes can be deployed for treating protein-rich water with drastically enhanced functions and separating oily water (oil-in-water emulsion) under atmospheric conditions with ultrahigh water flux and superior antifouling abilities. This versatile strategy to tailor membrane surface wettability paves the way for separation membranes to be used in harsh water environmental remediation and greatly stimulates the rapid development of mussel-inspired pDA based hybrid materials for advanced applications.

pH-induced reversible wetting transition between the underwater superoleophilicity and superoleophobicity.

Surfaces with controlled oil wettability in water have great potential for numerous underwater applications. In this work, we report a smart surface with pH-responsive oil wettability. The surface shows superoleophilicity in acidic water and superoleophobicity in basic water. Reversible transition between the two states can be achieved through alteration of the water pH. Such smart ability of the surface is due to the cooperation between the surface chemistry variation and hierarchical structures on the surface. Furthermore, we also extended this strategy to the copper mesh substrate and realized the selective oil/water separation on the as-prepared film. This paper reports a new surface with excellently controllable underwater oil wettability, and we believe such a surface has a lot of applications, for instance, microfluidic devices, bioadhesion, and antifouling materials.

Electrochemical preparation of porous MoO3 film with a high rate performance as anode for lithium ion batteries

A porous MoO3 film is prepared by electrodeposition on Ni foam substrates and exhibits a capacity of 650 mAh g−1 at a current density of 3 A g−1 as anodes for lithium ion batteries. Electrochemical measurements demonstrate that the outstanding rate performances are due to the improved Li+ diffusion kinetics.

Underwater Superoleophilic to Superoleophobic Wetting Control on the Nanostructured Copper Substrates

Surfaces with controlled underwater oil wettability would offer great promise in the design and fabrication of novel materials for advanced applications. Herein, we propose a new approach based on self-assembly of mixed thiols (containing both HS(CH2)9CH3 and HS(CH2)11OH) on nanostructured copper substrates for the fabrication of surfaces with controlled underwater oil wettability. By simply changing the concentration of HS(CH2)11OH in the solution, surfaces with controlled oil wettability from the underwater superoleophilicity to superoleophobicity can be achieved. The tunable effect can be due to the synergistic effect of the surface chemistry variation and the nanostructures on the surfaces. Noticeably, the amplified effect of the nanostructures can provide better control of the underwater oil wettability between the two extremes: superoleophilicity and superoleophobicity. Moreover, we also extended the strategy to the copper mesh substrates and realized the selective oil/water separation on the as-prepared copper mesh films. This report offers a flexible approach of fabricating surfaces with controlled oil wettability, which can be further applied to other ordinary materials, and open up new perspectives in manipulation of the surface oil wettability in water.

Designing heterogeneous chemical composition on hierarchical structured copper substrates for the fabrication of superhydrophobic surfaces with controlled adhesion.

Controlling water adhesion is important for superhydrophobic surfaces in many applications. Compared with numerous researches about the effect of microstructures on the surface adhesion, research relating to the influence of surface chemical composition on the surface adhesion is extremely rare. Herein, a new strategy for preparation of tunable adhesive superhydrophobic surfaces through designing heterogeneous chemical composition (hydrophobic/hydrophilic) on the rough substrate is reported, and the influence of surface chemical composition on the surface adhesion are examined. The surfaces were prepared through self-assembling of mixed thiol (containing both HS(CH2)9CH3 and HS(CH2)11OH) on the hierarchical structured copper substrates. By simply controlling the concentration of HS(CH2)11OH in the modified solution, tunable adhesive superhydrophobic surfaces can be obtained. The adhesive force of the surfaces can be increased from extreme low (about 8 μN) to very high (about 65 μN). The following two reasons can be used to explain the tunable effect: one is the number of hydrogen bond for the variation of surface chemical composition; and the other is the variation of contact area between the water droplet and surface because of the capillary effect that results from the combined effect of hydrophilic hydroxyl groups and microstructures on the surface. Noticeably, water droplets with different pH (2-12) have similar contact angles and adhesive forces on the surfaces, indicating that these surfaces are chemical resistant to acid and alkali. Moreover, the as-prepared surfaces were also used as the reaction substrates and applied in the droplet-based microreactor for the detection of vitamin C. This report provides a new method for preparation of superhydrophobic surfaces with tunable adhesion, which could not only help us further understand the principle for the fabrication of tunable adhesive superhydrophobic surfaces, but also potentially be used in many important applications, such as microfluidic devices and chemical microreactors.

Graphene Aerogels with Anchored Sub‐Micrometer Mulberry‐Like ZnO Particles for High‐Rate and Long‐Cycle Anode Materials in Lithium Ion Batteries

Graphene aerogels (GAs) anchoring hierarchical, mulberry-like ZnO particles are fabricated in situ using a one-step solvothermal reaction. The resulting composites can function as anodes in lithium ion batteries, where they exhibit a high capacity and cyclic stability. The reversible capacities obtained are 365, 320, and 230 mA h g-1 at current densities of 1, 2, and 10 A g-1 . Their high reversible capacity is 445 mA h g-1 at a current density of 1.6 A g-1 ; this value is maintained even after the 500th cycle, The excellent electrochemical performance is attributed to strong oxygen bridges between ZnO and graphene, where C-O-Zn linkages provide a good pathway for electron transport during charge/discharge cycles. Additionally, the hierarchical structure of the ZnO microballs suppresses stacking among the graphene layers, allowing the GAs to accelerate the transport of lithium ions. Furthermore, the GA framework enhances the electrical conductivity and buffer any volume expansion.

pH-Controllable Water Permeation through a Nanostructured Copper Mesh Film

Water permeation is an important issue in both fundamental research and industrial applications. In this work, we report a novel strategy to realize the controllable water permeation on the mixed thiol (containing both alkyl and carboxylic acid groups) modified nanostructured copper mesh films. For acidic and neutral water, the film is superhydrophobic, and the water cannot permeate the film because of the large negative capillary effect resulting from the nanostructures. For basic water, the film shows superhydrophilic property, and thus the water can permeate the film easily. The permeation process of water can be controlled just by simply altering the water pH. A detailed investigation indicates that nanostructures on the substrate and the appropriate size of the microscale mesh pores can enhance not only the static wettability but also the dynamic properties. The excellent controllability of water permeation is ascribed to the combined effect of the chemical variation of the carboxylic acid group and the microstructures on the substrate. This work may provide interesting insight into the new applications that are relevant to the surface wettability, such as filtration, microfluidic device, and some separation systems.

3D porous micro/nanostructured interconnected metal/metal oxide electrodes for high-rate lithium storage

In light of the micro/nanoporous structure concept and metal oxide-based anodes of lithium ion batteries (LIBs), a novel kind of three dimensional (3D) porous micro/nanostructured interconnected (PMNI) metal/metal oxide electrode was successfully fabricated via a facile H2 gas bubble dynamic template route. Firstly, 3D porous Ni (and Cu) was electrodeposited on the stainless steel sheet by the drastic cathodic deposition, partially thermally oxidized at a low temperature in air, and finally formed 3D PMNI Ni/NiO and Cu/Cu2O. Directly, as anodes of LIBs, 3D PMNI Ni/NiO and Cu/Cu2O exhibit a high-rate capability of 675.9 and 312.8 mA h g−1 at 20C rate, respectively. High-rate lithium storage properties may be ascribed to the fact that this kind of 3D PMNI metal/metal oxide electrode provides a stable 3D scaffold, highly conductive pathway and shorter ion diffusion length. Note that the H2 gas bubble dynamic template route in the present work is a low cost, facile one-step process of formation and elimination of the template, and offers flexibility in controllable thickness and pore diameters of 3D porous structures, assuring optimization to match the characteristic kinetics of other LIBs electrodes. The strategy may open up a new way to design and optimize 3D multifunctional architectured electrodes by using suitable micro and nano dimensional sub-components.

Regulating Underwater Oil Adhesion on Superoleophobic Copper Films through Assembling n-Alkanoic Acids

Controlling liquid adhesion on special wetting surface is significant in many practical applications. In this paper, an easy self-assembled monolayer technique was advanced to modify nanostructured copper substrates, and tunable adhesive underwater superoleophobic surfaces were prepared. The surface adhesion can be regulated by simply varying the chain length of the n-alkanoic acids, and the tunable adhesive properties can be ascribed to the combined action of surfaces nanostructures and related variation in surface chemistry. Meanwhile, the tunable ability is universal, and the oil-adhesion controllability is suitable to various oils including silicon oil, n-hexane, and chloroform. Finally, on the basis of the special tunable adhesive properties, some applications of our surfaces including droplet storage, transfer, mixing, and so on are also discussed. The paper offers a novel and simple method to prepare underwater superoleophobic surfaces with regulated adhesion, which can potentially be applied in numerous fields, for instance, biodetection, microreactors, and microfluidic devices.