Dongliang Tian

Photo-induced water–oil separation based on switchable superhydrophobicity–superhydrophilicity and underwater superoleophobicity of the aligned ZnO nanorod array-coated mesh films

Stimulus-responsive surface wettability, especially photoresponsive surface wettability, has been intensively studied. Meanwhile, multifunctional surfaces, especially for the treatment of oil contaminated water, have aroused worldwide attention. Recently, pH-responsive surfaces with controllable oil–water separation have also been reported. However, photoresponsive water–oil separation is still a challenge. Here we report photo-induced water–oil separation based on the switchable superhydrophobicity–superhydrophilicity and underwater superoleophobicity of aligned ZnO nanorod array-coated mesh films, which shows excellent controllability and high separation efficiency of different types of water–oil mixtures in an oil–water–solid three-phase system. The underwater superoleophobicity of the aligned ZnO nanorod array-coated stainless steel mesh film can effectively prevent the mesh film from being polluted by oils. This work is promising in photo-induced water–oil mixture treatments such as water-removal from a micro-reaction system and controllable filtration, and may also provide interesting insight into the design of novel functional devices based on controllable surface wettability.

Underwater Self-Cleaning Scaly Fabric Membrane for Oily Water Separation

Oily wastewater is always a threat to biological and human safety, and it is a worldwide challenge to solve the problem of disposing of it. The development of interface science brings hope of solving this serious problem, however. Inspired by the capacity for capturing water of natural fabrics and by the underwater superoleophobic self-cleaning property of fish scales, a strategy is proposed to design and fabricate micro/nanoscale hierarchical-structured fabric membranes with superhydrophilicity and underwater superoleophobicity, by coating scaly titanium oxide nanostructures onto fabric microstructures, which can separate oil/water mixtures efficiently. The microstructures of the fabrics are beneficial for achieving high water-holding capacity of the membranes. More importantly, the special scaly titanium oxide nanostructures are critical for achieving the desired superwetting property toward water of the membranes, which means that air bubbles cannot exist on them in water and there is ultralow underwater-oil adhesion. The cooperative effects of the microscale and nanoscale structures result in the formation of a stable oil/water/solid triphase interface with a robust underwater superoleophobic self-cleaning property. Furthermore, the fabrics are common, commercially cheap, and environmentally friendly materials with flexible but robust mechanical properties, which make the fabric membranes a good candidate for oil/water separation even under strong water flow. This work would also be helpful for developing new underwater superoleophobic self-cleaning materials and related devices.

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.

Optical waveguides based on single-crystalline organic micro-tiles.

Surface waveguides are an important topic because of their ability to transmit sub-wavelength information, [ 1 ] that is, details with dimensions less than the wavelength of visible light, which holds promise for utilization in faster and more compact optoelectronic communications and sensors. [ 2 ] Great effort has been put into optical waveguides based on onedimensional (1D) inorganic nanostructures. For example, Lieber’s group [ 3 , 4 ] and Yang and coworkers [ 5 , 6 ] have demonstrated that crystalline wireand ribbon-like nanomaterials of inorganic semiconductors can successfully serve as waveguides for light with wavelengths less than that of visible light. Then, Redmond and coworkers reported the waveguiding property of conjugated polymer nanowires. [ 7 ] Very recently, optical waveguides based on 1D structures of small organic molecules have been realized using nanowires, nanoribbons, and nanofi bers. [ 8–14 ] However, optical waveguides based on small organic molecules with 2D structures are still in their infancy. [ 15 ] They are expected to display waveguiding behavior different from that of 1D materials owing to their different microstructures. Furthermore, it should be of great scientifi c interest to extend the relevant research from solid 1D nanorods/wires/ tubes to 2D micro-tiles, because the 2D tile structures are more suitable for the application of controlling directional waveguides. Here, we report the preparation of 2D crystalline microstructures, that is, micro-tiles, from hexaphenylsiloles (HPSs), small organic compounds, by self-assembly. Characterization of single micro-tiles indicates that the 2D HPS microstructures can serve as active optical waveguides that allow locally excited photoluminescence to propagate along the abscissa of the 2D structures and out-couple at the ridge tips. The unique 2D optical waveguiding phenomenon of HPS micro-tiles might be useful

Fast Responsive and Controllable Liquid Transport on a Magnetic Fluid/Nanoarray Composite Interface

Controllable liquid transport on surface is expected to occur by manipulating the gradient of surface tension/Laplace pressure and external stimuli, which has been intensively studied on solid or liquid interface. However, it still faces challenges of slow response rate, and uncontrollable transport speed and direction. Here, we demonstrate fast responsive and controllable liquid transport on a smart magnetic fluid/nanoarray interface, i.e., a composite interface, via modulation of an external magnetic field. The wettability of the composite interface to water instantaneously responds to gradient magnetic field due to the magnetically driven composite interface gradient roughness transition that takes place within a millisecond, which is at least 1 order of magnitude faster than that of other responsive surfaces. A water droplet can follow the motion of the gradient composite interface structure as it responds to the gradient magnetic field motion. Moreover, the water droplet transport direction can be controlled by modulating the motion direction of the gradient magnetic field. The composite interface can be used as a pump for the transport of immiscible liquids and other objects in the microchannel, which suggests a way to design smart interface materials and microfluidic devices.

Fish gill inspired crossflow for efficient and continuous collection of spilled oil

Developing an effective system to clean up large-scale oil spills is of great significance due to their contribution to severe environmental pollution and destruction. Superwetting membranes have been widely studied for oil/water separation. The separation, however, adopts a gravity-driven approach that is inefficient and discontinuous due to quick fouling of the membrane by oil. Herein, inspired by the crossflow filtration behavior in fish gills, we propose a crossflow approach via a hydrophilic, tilted gradient membrane for spilled oil collection. In crossflow collection, as the oil/water flows parallel to the hydrophilic membrane surface, water is gradually filtered through the pores, while oil is repelled, transported, and finally collected for storage. Owing to the selective gating behavior of the water-sealed gradient membrane, the large pores at the bottom with high water flux favor fast water filtration, while the small pores at the top with strong oil repellency allow easy oil transportation. In addition, the gradient membrane exhibits excellent antifouling properties due to the protection of the water layer. Therefore, this bioinspired crossflow approach enables highly efficient and continuous spilled oil collection, which is very promising for the cleanup of large-scale oil spills.

Optoelectrowettability conversion on superhydrophobic CdS QDs sensitized TiO2 nanotubes

This work demonstrates the process of building optoelectrically cooperative surface wetting in smart and precise way. The superhydrophobic photosensitive film is constructed with TiO(2) nanotube arrays. Compared with conventional organic dyes, CdS quantum dots (QDs) as sensitizer layer are modified on TiO(2) nanotubes surface to improve photosensitivity of the composited surface in visible light region, which offer the benefit for designing and fabricating solid state hetero-junction devices. ITO glass is introduced as top electrode to apply electrical and optical stimuli and the patterned wetting is instantly obtained with masking light through ITO. The optoelectrically cooperative wettability conversion occurred on superhydrophobic TiO(2) nanotube surface at critical voltage of 12 V, which was decreased by 18 V comparing with only using electric stimulus. This study provides potential applications for TiO(2) nanotube arrays to the associated research of liquid reprography, location-controlled microfluidic device and lab-on-chip.

External-Field-Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

External-field-responsive liquid transport has received extensive research interest owing to its important applications in microfluidic devices, biological medical, liquid printing, separation, and so forth. To realize different levels of liquid transport on surfaces, the balance of the dynamic competing processes of gradient wetting and dewetting should be controlled to achieve good directionality, confined range, and selectivity of liquid wetting. Here, the recent progress in external-field-induced gradient wetting is summarized for controllable liquid transport from movement on the surface to penetration into the surface, particularly for liquid motion on, patterned wetting into, and permeation through films on superwetting surfaces with external field cooperation (e.g., light, electric fields, magnetic fields, temperature, pH, gas, solvent, and their combinations). The selected topics of external-field-induced liquid transport on the different levels of surfaces include directional liquid motion on the surface based on the wettability gradient under an external field, partial entry of a liquid into the surface to achieve patterned surface wettability for printing, and liquid-selective permeation of the film for separation. The future prospects of external-field-responsive liquid transport are also discussed.

Patterned liquid permeation through the TiO2 nanotube array coated Ti mesh by photoelectric cooperation for liquid printing

The surface wettability response has been intensively studied under external stimulus, and the cooperation of different stimuli seems a trend for more effective surface wetting. Despite much progress in this field, the patterning of controllable surface wettability is still a challenge, which is a very important issue for printing techniques. Here, we have developed an approach for the photoelectric cooperative wetting induced liquid permeation through a TiO2 nanotube array coated Ti mesh. The patterned liquid permeation can be realized by patterned light illumination under a voltage which is lower than the electrowetting induced permeation threshold voltage. The permeation process and mechanism are discussed in detail. The results indicate that the microscale movement of a liquid can be controlled precisely by the surface micro/nano hierarchical structure of the device, with a low adhesion and responsive voltage. Therefore, this work is important in the research and application of liquid printing, moreover, it provides a new approach to develop and apply novel devices such as micro/nanofluidic systems, microreactors and micro-nanoelectronic technologies.

Morphology-controlled self-assembled nanostructures of a porphyrin derivative and their photoelectrochemical properties

We have shown that various porphyrin-containing nanostructures can be facilely synthesized by varying the assembly solvent or the temperature in the oil medium, which effectively modulates the evaporation rate and assembly rate of the porphyrin molecules. A dichloromethane solution of 5-(4-(ethylcarboxypropoxy)phenyl)-10,15,20-tri(naphthyl) porphyrin Zn (CTNP–Zn) was injected into a volume of poor solvent and subsequently mixed with a microinjector. The mixture was cast onto the ITO substrate and then left undisturbed to stabilize the nanostructure under different temperature. After the solvent evaporation, diverse CTNP–Zn based nanostructures, including ring-shaped, honey-comb structured, rice-shaped, hollow spherical, urn-shaped, etc., were successfully assembled depending on the solvent composition or the evaporation temperature. The nanostructures have been characterized by electronic absorption, scanning electron microscopy (SEM) and photoelectric conversion techniques. The internal structures of the nanostructures are described by XRD. It is of great significance for the further extending the applications in optic devices.