Fogging occurs when moisture condensation takes the form of accumulated droplets with diameters larger than 190 nm or half of the shortest wavelength (380 nm) of visible light. This problem may be effectively addressed by changing the affinity of a material’s surface for water, which can be accomplished via two approaches: i) the superhydrophilic approach, with a water contact angle (CA) less than 5°, and ii) the superhydrophobic approach, with a water CA greater than 150°, and extremely low CA hysteresis. To date, all techniques reported belong to the former category, as they are intended for applications in optical transparent coatings. A well-known example is the use of photocatalytic TiO2 nanoparticle coatings that become superhydrophilic under UV irradiation. Very recently, a capillary effect was skillfully adopted to achieve superhydrophilic properties by constructing 3D nanoporous structures from layer-by-layer assembled nanoparticles. The key to these two “wet”-style antifogging strategies is for micrometer-sized fog drops to rapidly spread into a uniform thin film, which can prevent light scattering and reflection from nucleated droplets. Optical transparency is not an intrinsic property of antifogging coatings even though recently developed antifogging coatings are almost transparent, and the transparency could be achieved by further tuning the nanoparticle size and film thickness. To our knowledge, the antifogging coatings may also be applied to many fields that do not require optical transparency, including, for example, paints for inhibiting swelling and peeling issues and metal surfaces for preventing corrosion. These types of issues, which are caused by adsorption of moisture, are hard to solve by the superhydrophilic approach because of its inherently “wet” nature. Thus, a “dry”-style antifogging strategy, which consists of a novel superhydrophobic technique that can prevent moisture or microscale fog drops from nucleating on a surface, is desired. Recent bionic researches have revealed that the self-cleaning ability of lotus leaves and the striking ability of a water-strider’s legs to walk on water can be attributed to the ideal superhydrophobicity of their surfaces, induced by special microand nanostructures. To date, the biomimetic fabrication of superhydrophobic microand/or nanostructures has attracted considerable interest, and these types of materials can be used for such applications as self-cleaning coatings and stain-resistant textiles. Although a superhydrophobic technique inspired by lotus leaves is expected to be able to solve such fogging problems because the water droplets can not remain on the surface, there are no reports of such antifogging coatings. Very recently, researchers from General Motors have reported that the surfaces of lotus leaves become wet with moisture because the size of the fog drops are at the microscale—so small that they can be easily trapped in the interspaces among micropapillae. Thus, lotuslike surface microstructures are unsuitable for superhydrophobic antifogging coatings, and a new inspiration from nature is desired for solving this problem. In this communication, we report a novel, biological, superhydrophobic antifogging strategy. It was found that the compound eyes of the mosquito C. pipiens possess ideal superhydrophobic properties that provide an effective protective mechanism for maintaining clear vision in a humid habitat. Our research indicates that this unique property is attributed to the smart design of elaborate microand nanostructures: hexagonally non-close-packed (ncp) nipples at the nanoscale prevent microscale fog drops from condensing on the ommatidia surface, and hexagonally close-packed (hcp) ommatidia at the microscale could efficiently prevent fog drops from being trapped in the voids between the ommatidia. We also fabricated artificial compound eyes by using soft lithography and investigated the effects of microand nanostructures on the surface hydrophobicity. These findings could be used to develop novel superhydrophobic antifogging coatings in the near future. It is known that mosquitoes possess excellent vision, which they exploit to locate various resources such as mates, hosts, and resting sites in a watery and dim habitat. To better understand such remarkable abilities, we first investigated the interaction between moisture and the eye surface. An ultrasonic humidifier was used to regulate the relative humidity of the atmosphere and mimic a mist composed of numerous tiny water droplets with diameters less than 10 lm. As the fog was C O M M U N IC A IO N

The dry-style antifogging properties of mosquito compound eyes and artificial analogues prepared by soft lithography: a superhydrophobic state with high adhesive force

Review on the criteria anticipated for the fabrication of highly efficient ZnO-based visible-light-driven photocatalysts

In recent years, nanocrystals of metal sulfide materials have attracted scientific research interest for renewable energy applications due to the abundant choice of materials with easily tunable electronic, optical, physical and chemical properties. Metal sulfides are semiconducting compounds where sulfur is an anion associated with a metal cation; and the metal ions may be in mono-, bi- or multi-form. The diverse range of available metal sulfide materials offers a unique platform to construct a large number of potential materials that demonstrate exotic chemical, physical and electronic phenomena and novel functional properties and applications. To fully exploit the potential of these fascinating materials, scalable methods for the preparation of low-cost metal sulfides, heterostructures, and hybrids of high quality must be developed. This comprehensive review indicates approaches for the controlled fabrication of metal sulfides and subsequently delivers an overview of recent progress in tuning the chemical, physical, optical and nano- and micro-structural properties of metal sulfide nanocrystals using a range of material fabrication methods. For hydrogen energy production, three major approaches are discussed in detail: electrocatalytic hydrogen generation, powder photocatalytic hydrogen generation and photoelectrochemical water splitting. A variety of strategies such as structural tuning, composition control, doping, hybrid structures, heterostructures, defect control, temperature effects and porosity effects on metal sulfide nanocrystals are discussed and how they are exploited to enhance performance and develop future energy materials. From this literature survey, energy conversion currently relies on a limited range of metal sulfides and their composites, and several metal sulfides are immature in terms of their dissolution, photocorrosion and long-term durability in electrolytes during water splitting. Future research directions for innovative metal sulfides should be closely allied to energy and environmental issues, along with their advanced characterization, and developing new classes of metal sulfide materials with well-defined fabrication methods.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

Inorganic semiconductor nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating the size and dimensionality dependence of their properties for potential applications. The use of such nanostructures with tailored geometries as building blocks is also expected to play crucial roles in future nanodevices. Since the discovery of carbon nanotubes much attention has been paid to exploring the usage of inorganic semiconductor nanostructures as field-emitters due to their low work functions, high aspect ratios and mechanical stabilities, and high electrical and thermal conductivities. This article provides a comprehensive review of the state-of-the-art research activities in the field. It mainly focuses on the most widely studied inorganic nanostructures, such as ZnO, ZnS, Si, WO3, AlN, SiC, and their field-emission properties. We begin with a survey of inorganic semiconductor nanostructures and the field-emission principle, and then discuss the recent progresses on several kinds of important nanostructures and their field-emission characteristics in detail and overview some additional inorganic semiconducting nanomaterials in short. Finally, we conclude this review with some perspectives and outlook on the future developments in this area.

Inorganic semiconductor nanostructures and their field-emission applications

Isolated atoms featuring unique reactivity are at the heart of enzymatic and homogeneous catalysts. In contrast, although the concept has long existed, single-atom heterogeneous catalysts (SACs) have only recently gained prominence. Host materials have similar functions to ligands in homogeneous catalysts, determining the stability, local environment, and electronic properties of isolated atoms and thus providing a platform for tailoring heterogeneous catalysts for targeted applications. Within just a decade, we have witnessed many examples of SACs both disrupting diverse fields of heterogeneous catalysis with their distinctive reactivity and substantially enriching our understanding of molecular processes on surfaces. To date, the term SAC mostly refers to late transition metal-based systems, but numerous examples exist in which isolated atoms of other elements play key catalytic roles. This review provides a compositional encyclopedia of SACs, celebrating the 10th anniversary of the introduction of this term. By defining single-atom catalysis in the broadest sense, we explore the full elemental diversity, joining different areas across the whole periodic table, and discussing historical milestones and recent developments. In particular, we examine the coordination structures and associated properties accessed through distinct single-atom-host combinations and relate them to their main applications in thermo-, electro-, and photocatalysis, revealing trends in element-specific evolution, host design, and uses. Finally, we highlight frontiers in the field, including multimetallic SACs, atom proximity control, and possible applications for multistep and cascade reactions, identifying challenges, and propose directions for future development in this flourishing field.

Single-Atom Catalysts across the Periodic Table.

Fabrication of nanostructured CuO films by electrodeposition and their photocatalytic properties

Controllable fabrication of CuO nanostructure by hydrothermal method and its properties

In order to achieve high performance in visible-light photocatalysis, V4+ and Ce3+ self-doped BiVO4/CeO2 heterostructured nanocomposites with high surface areas were prepared using the templating approach employing mesoporous silica MCM-41 as the hard template. X-ray photoelectron spectroscopy (XPS) spectra have demonstrated the presence of plentiful V4+ and Ce3+ species in the nanocomposites accompanied by the formation of oxygen vacancies. The presence of V4+ species is further identified by the electron spin resonance (ESR) spectrum. Furthermore, the BiVO4 and CeO2 could be affecting each other by arousing the structural changes in the formed nanocomposites. The V4+ and Ce3+ self-doped 0.4BiVO4/0.6CeO2 nanocomposite with the surface area as large as 78.35 m2/g exhibits the highest photocatalytic activity for the rhodamine B (RhB) and methyl orange (MO) degradation and photoelectrochemical performances. The enhanced photocatalytic mechanism is systematically studied via UV–vis diffuse reflectance spectr...

In Situ Synthesis of V4+ and Ce3+ Self-Doped BiVO4/CeO2 Heterostructured Nanocomposites with High Surface Areas and Enhanced Visible-Light Photocatalytic Activity

Controllable preparation, growth mechanism and the properties research of TiO2 nanotube arrays

The combination of biomimetic nanochannels and nanostructures provided a new idea for bioanalytical purposes. In this paper, we reported a self-assembled system based on the integration of anodic aluminum oxide (AAO) membranes and CuO method to fabricate CuO nanostructures in the confined area of AAO membranes. Furthermore, we investigated morphologies of the self-assembly systems by field emission scanning electron microscopy (FESEM) and characterized the type and content of microelements by energy dispersive spectrometer. Transmembrane ion current through nanochannels was tested by an electrochemical workstation, and optical properties of the self-assembly systems were characterized by ultraviolet–visible spectrophotometer. We could conclude from the results that the morphology and distribution status of CuO nanostructures are controllable, while ionic current through nanochannels and optical properties of self-assembled systems could be regulated by changing experimental parameters such as electrodeposition time, electrodeposition voltage or annealing temperature. On this base, we utilized the synergistic effect of nanochannels and nanostructures to enhance the sensitivity of biological molecules response. This study not only prepared CuO nanostructures in biomimetic nanochannels controllably, but also provided a novel application paradigm for nanochannels-nanostructures self-assembled system, which could be used for biological analysis and detection.

Yongqian Wang

Papers

Fabrication of nanostructured CuO films by electrodeposition and their photocatalytic properties

Controllable fabrication of CuO nanostructure by hydrothermal method and its properties

In Situ Synthesis of V4+ and Ce3+ Self-Doped BiVO4/CeO2 Heterostructured Nanocomposites with High Surface Areas and Enhanced Visible-Light Photocatalytic Activity

Controllable preparation, growth mechanism and the properties research of TiO2 nanotube arrays

Nanostructures confined self-assembled in biomimetic nanochannels for enhancing the sensitivity of biological molecules response