Reversible wettability of a chemical vapor deposition prepared ZnO film between superhydrophobicity and superhydrophilicity

A superhydrophobic ZnO thin film was fabricated by the Au-catalyzed chemical vapor deposition method. The surface of the film exhibits hierarchical structure with nanostructures on sub-microstructures. The water contact angle (CA) was 164.3 degrees, turning into a superhydrophilic one (CA < 5 degrees) after UV illumination, which can be recovered through being placed in the dark or being heated. The film was attached tightly to the substrate, showing good stability and durability. The surface structures were characterized by scanning electron microscopy and atomic force microscopy.     

Bio-inspired fabrication of well-oriented ZnO nanorod arrays film and its superhydrophobicity and superhydrophilicity

A highly oriented ZnO nanorod array film was fabricated on glass substrate by combinations of Sol–Gel and hydrothermal. The film exhibits perfect superhydrophobicity with a contact angle of 155° and a glide angle of 4° after being surface modified by fluoroalkylsilane, which is similar with wings’ property and structures of large yellow spots mosquitoes. Interestingly, the ZnO nanorods film were converted from superhydrophobicity into superhydrophilicity under ultraviolet light for 2 h due to the decomposition of fluoroalkyl chain of fluoroalkylsilane and the photosensitivity of ZnO surface. The transition mechanisms of wettability are discussed on the basis of correlated theories.     

Cell adhesive spectra along surface wettability gradient from superhydrophilicity to superhydrophobicity

Surface wettability is important to design biointerfaces and functional biomaterials in various biological applications. However, to date, it remains some confusions about how cells would response to the surfaces with different wettabilities. Herein, we systematically explore the adhesive spectra of cells to the surface with wettability gradient from superhydrophilicity to superhydrophobicity, clarifying the effect of wettability on cell adhesion. We envision that this study may provide valuable information for the design of biomedical implants with controllable cell adhesion, such as neural interface devices and flexible implant.     

Strain-controlled switching of hierarchically wrinkled surfaces between superhydrophobicity and superhydrophilicity

Recent years have witnessed intense interest in multifunctional surfaces that can be designed to switch between different functional states with various external stimuli including electric field, light, pH value, and mechanical strain. The present paper is aimed to explore whether and how a surface can be designed to switch between superhydrophobicity and superhydrophilicity by an applied strain. Based on well-established theories of structure buckling and solid-liquid contact, we show that this objective may be achieved through a hierarchically wrinkled surface. We derive general recursive relations for the apparent contact angle at different levels of the hierarchical surface and investigate the thermodynamic stability of different contact states. Our study may provide useful guidelines for the development of multifunctional surfaces for many technological applications.     

Dye-sensitized solar cells based on a single-crystalline TiO2 nanorod film

Highly crystalline TiO2 nanorods with lengths of 100-300 nm and diameters of 20-30 nm have been synthesized by a hydrothermal process in a cetyltrimethylammonium bromide surfactant solution. The microstructure measured by X-ray diffraction and high-resolution transmission electron microscopy was a pure highly crystalline anatase phase with a long nanorod shape. The addition of a triblock copolymer poly(ethylene oxide)100-poly(propylene oxide) 65-poly(ethylene oxide)100 (F127) decreased the length of the nanorods and kept the rod shape of the particles even after sintering at high temperatures. The rod shape kept under high calcination temperatures contributed to the achievement of the high conversion efficiency of light-to-electricity as discussed in the paper. A high conversion efficiency of light-to-electricity of 7.29% was obtained with the TiO2 single-crystalline anatase nanorod cell.     

Achievement of highly conductive p-type transparent NdCuOS film with Cu deficiency and effective doping

Future advanced invisible or transparent electronics necessitate the need to overcome the well-known challenge in achieving high-performance p-type transparent semiconducting oxides (TSOs). Here, we report our success in achieving an outstanding p-type TSO thin film NdCuOS, which is the best performing p-type TSO reported to date based on the figure of merit (FoM) according to the best of our knowledge. In this work, we designed a novel chemical solution method to prepare the highly performing NdCuOS films with different doping elements. Our success in using a chemical solution method to grow semiconducting NdCuOS demonstrates that highly conductive oxychalcogenide films are possible to be prepared by a solution method. Such a solution method is facile, economically efficient, and scalable. Among our NdCuOS films with different dopants, we find that Mg-doped NdCuOS film demonstrates a very high p-type conductivity of 52.1 S cm^?1 and optical transmittance of 54.3% with a huge FoM value of 1706 μS. This surpassed all the other p-type films reported so far in terms of FoM. Strong photoluminescence peaks at 3.0 eV are observed for our films, indicating their great potential applications for UV or blue light LED and other devices. The science behind such a successful achievement of high-performance p-type NdCuOS film is analyzed and discussed. A transparent p-n diode with very low leakage current (9.12  μA at ?3 V) and turn-on voltage (1.1 V) is successfully fabricated, and it demonstrates a good device performance.     

A thin-layer spectroelectrochemical study of 3,3'''',5,5''''-tetramethylbenzidine at SnO_2:F film optically transparent electrode

3,3',5,5'-tetramethylbenzidine (TMB) is a sensi-tive commonly-used substrate of the spectrophotomet-ric enzyme-linked immunosorbent assay (ELISA) as well as the electrochemical enzyme-linked immuno-assay[1,2]. It is more stable and of lower reagent blank than another sensitive commonly-used substrate, o-phenylenediamine. TMB is also the substrate of the most ELISA kits for clinical examination. The TMB- H2O2-horseradish peroxidase (HRP) voltammetric en-zyme immunoassay system has very…     

A thin-layer spectroelectrochemical study of 3,3′,5,5′-tetramethylbenzidine at SnO2:F film optically transparent electrode

Science China Chemistry - The electrooxidation of 3,3′, 5,5′-tetramethylbenzidine (TMB) is dependent on the pH value of Britton-Robinson (B-R) buffer solution. In this work, the...     

Hierarchical assembly of SnO2 nanorod arrays on alpha-Fe2O3 nanotubes: a case of interfacial lattice compatibility

SnO2 nanorod arrays were hierarchically assembled onto the surface of alpha-Fe2O3 nanotubes via a facile solution method. Determined by the hexagonal geometrical nature of the alpha-Fe2O3 nanotubes, the heterostructures were of 6-fold symmetry. HRTEM characterizations demonstrated that the lattice mismatch at the interface was an important factor in determining the growth direction of the secondary nanorod arrays.     

Electrochemical wettability control on conductive TiO2 nanotube surfaces modified with a ferrocene redox system

This work reports on an electrochemical system which allows the control of surface wettability properties by voltage induced changes in contact angle (Θ) of ΔΘ  50°. For this we used conductive TiO₂ nanotubular layers that were modified with ferrocene coupled to the TiO₂ surface via triethoxysilane. To enhance the hydrophobic character of the nanotubular TiO₂ surface, also mixed organic monolayers namely perfluorotriethoxysilane, were explored. Formation of the ferrocene and mixed organic monolayer was confirmed by X-ray-photoelectron-spectroscopy (XPS). Contact angle combined with electrochemical measurements show that ferrocene in these monolayers can successfully be switched from Fe²⁺ to Fe³⁺ and that this change in the redox state considerably alters the wetting properties. Using a conductive nanotube substrate allows us to amplify this change by a factor of more than 10, and thus this surface can be used to trigger significant wetting alterations.     

Effects of nanorod structure and conformation of fatty acid self-assembled layers on superhydrophobicity of zinc oxide surface

Superhydrophobic surfaces have been prepared from nanostructured zinc oxide layers by a treatment with fatty acid molecules. The layers are electrochemically deposited from an oxygenated aqueous zinc chloride solution. The effects of the layer's structure, from a dense film to that of a nanorod array, as well as that of the properties of the fatty acid molecules based on C18 chains are described. A contact angle (CA) as high as 167 degrees is obtained with the nanorod structure and the linear saturated molecule (stearic acid). Lower values are found with molecules having an unsaturated bond on C9, in particular with a cis conformation (140 degrees ). These results, supplemented by infrared spectroscopy, indicate an enhancement of the sensitivity to the properties of the fatty acid molecules (conformation, flexibility, saturated or not) when moving from the flat surface to the nanostructured surface. This is attributed to a specific influence of the structure of the tops of the rods and lateral wall properties on the adsorption and organization of the molecules. CA measurements show a very good stability of the surface in time if stored in an environment protected from UV radiations.     

A transparent and photo-patternable superhydrophobic film

A transparent superhydrophobic TiO2 film, prepared by spin-coating a TiO2 slurry on a glass substrate and modifying the resultant TiO2 film with fluoroalkylsilane molecules, was patterned by illumination with ultraviolet light through a photomask, producing a superhydrophobic/superhydrophilic surface micropattern with very small superhydrophilic areas, which we were able to selectively fill with alginate hydrogel.     

Structural and electrochemical properties of a porous nanostructured SnO2 film electrode for lithium-ion batteries

A B₂O₃-doped SnO₂ thin film was prepared by a novel experimental procedure combining the electrodeposition and the hydrothermal treatment, and its structure and electrochemical properties were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and galvanostatic charge–discharge tests. It was found that the as-prepared modified SnO₂ film shows a porous network structure with large specific surface area and high crystallinity. The results of electrochemical tests showed that the modified SnO₂ electrode presents the largest reversible capacity of 676 mAh g^?1 at the fourth cycle, close to the theoretical capacity of SnO₂ (790 mAh g^?1); and it still delivers a reversible Li storage capacity of 524 mAh g^?1 after 50 cycles. The reasons that the modified SnO₂ film electrode shows excellent electrochemical properties were also discussed.     

Electrodeposition of SnO2 nanocrystalline thin film using butyl-rhodamine B as a structure-directing agent

<正>Porous SnO_2 nanocrystalline thin films were successfully electrodeposited from an oxygen-saturated acid aqueous solution of SnCl_2 containing different concentrations of butyl-rhodamine B(BRhB) at 70℃.BRhB with substitute of amidocyanogen can be dissolved in the acid deposition solution,where HCl was added to suppress hydrolysis of SnCl_2.So it was used as a structure-directing agent to promote the crystal growth of SnO_2.The formed porous morphology and tetragonal rutile crystalline structure of the electrodeposited thin films were controlled by the addition of BRhB with different amounts.