Separators play a pivotal role in the electrochemical performance and safety of lithium-ion batteries (LIBs). The commercial microporous polyolefin-based separators often suffer from inferior electrolyte wettability, low thermal stability, and severe safety concerns. Herein, a novel kind of highly flexible and porous separator based on hydroxyapatite nanowires (HAP NWs) with excellent thermal stability, fire resistance, and superior electrolyte wettability is reported. A hierarchical cross-linked network structure forms between HAP NWs and cellulose fibers (CFs) via hybridization, which endows the separator with high flexibility and robust mechanical strength. The high thermal stability of HAP NW networks enables the separator to preserve its structural integrity at temperatures as high as 700 °C, and the fire-resistant property of HAP NWs ensures high safety of the battery. In particular, benefiting from its unique composition and highly porous structure, the as-prepared HAP/CF separator exhibits near zero contact angle with the liquid electrolyte and high electrolyte uptake of 253%, indicating superior electrolyte wettability compared with the commercial polyolefin separator. The as-prepared HAP/CF separator has unique advantages of superior electrolyte wettability, mechanical robustness, high thermal stability, and fire resistance, thus, is promising as a new kind of separator for advanced LIBs with enhanced performance and high safety.

Flexible, High-Wettability and Fire-Resistant Separators Based on Hydroxyapatite Nanowires for Advanced Lithium-Ion Batteries.

Recent progress in the preparation, properties and applications of superhydrophobic nano-based coatings and surfaces: A review

Solar-steam generation is one of the most promising technologies to mitigate the issue of clean water shortage using sustainable solar energy. Photothermal aerogels, especially the three-dimensional (3D) graphene-based aerogels, have shown unique merits for solar-steam generation, such as lightweight, high flexibility, and superior evaporation rate and energy efficiency. However, 3D aerogels require much more raw materials of graphene, which limits their large-scale applications. In this study, 3D photothermal aerogels composed of reduced graphene oxide (RGO) nanosheets, rice-straw-derived cellulose fibers, and sodium alginate (SA) are prepared for solar-steam generation. The use of rice straw fibers as skeletal support significantly reduces the need for the more expensive RGO by 43.5%, turning the rice straw biomass waste into value-added materials. The integration of rice straw fibers and RGO significantly enhances the flexibility and mechanical stability of the obtained photothermal RGO-SA-cellulose aerogel. The photothermal aerogel shows a strong broad-band light absorption of 96-97%. During solar-steam generation, the 3D photothermal aerogel effectively decreases the radiation and convection energy loss while enhancing energy harvesting from the environment, leading to an extremely high evaporation rate of 2.25 kg m-2 h-1, corresponding to an energy conversion efficiency of 88.9% under 1.0 sun irradiation. The salinity of clean water collected during the evaporation of real seawater is only 0.37 ppm. The materials are environmentally friendly and cost-effective, showing great potential for real-world desalination applications.

Graphene and Rice-Straw-Fiber-Based 3D Photothermal Aerogels for Highly Efficient Solar Evaporation.

The nanozymes are a kind of synthetic nanomaterials with enzyme-like properties. Metal–organic frameworks (MOFs) are an important class of inorganic–organic hybrid crystals. Their unique composition, structural diversity and size tailorability enable them to be promising for the construction of novel nanozymes. This review intends to summarize the recent advance for the construction of MOFs-based nanozymes and their primary applications in chemical sensing and biosensing. Based on their synthetical strategies, the MOFs-based nanozymes are categorized into four classes: pristine MOFs, MOFs with chemical modification, MOFs-based composites and MOF derivatives. In each categorization, the design and enzyme mimetic activity are discussed. Moreover, the analytical applications of these nanozymes are covered, such as the detection of H2O2, small biomolecules releasing H2O2, reductive small biomolecules, biomacromolecules, heavy metal ions, toxic metabolite of fungi, antibiotics, and so on. Finally, a summary and future perspective on the applications of MOFs-based nanozymes are briefly discussed.

Recent advances in the construction and analytical applications of metal-organic frameworks-based nanozymes

The emerging solar desalination technology is considered as one of the most promising strategies to ensure water security. However, with the proceeding of solar desalination, salt crystallization on the surface of solar evaporators caused by increasing salinity of seawater will result in a decrease in the evaporation rate. Thus, it is still challenging to fabricate solar evaporators with superior salt resistance. In this work, elastic ceramic-based nanofibrous aerogels with a cellular architecture are fabricated by the combination of electrospinning and fiber freeze-shaping technologies, which are composed of vertically aligned vessels and porous vessel walls. Under the action of convection and diffusion promoted by this unique cellular architecture, the aerogels exhibit a superior salt-resistance without any salt crystals on the surface of aerogels even in 20% brine and under 6-sun irradiation. Moreover, by virtue of the synergistic effect of the promising structure and light absorbance of carbon nanotubes, aerogels possess a high light absorbance of up to 98% and excellent evaporation performance achieving 1.50 kg m-2 h-1 under 1-sun irradiation. This work may provide a fascinating avenue for the desalination of seawater in a salt-resistance and efficient manner.

Cellular Structured CNTs@SiO2 Nanofibrous Aerogels with Vertically Aligned Vessels for Salt-Resistant Solar Desalination.

Wallpaper with multiple functions, such as fire resistance and an automatic alarm in fire disasters, will be attractive for the interior decoration of houses. Herein, we report a smart fire alarm wallpaper prepared using fire-resistant inorganic paper based on ultralong hydroxyapatite nanowires (HNs) and graphene oxide (GO) thermosensitive sensors. At room temperature, the GO thermosensitive sensor is in a state of electrical insulation; however, it becomes electrically conductive at high temperatures. In a fire disaster, high temperature will rapidly remove the oxygen-containing groups of GO, leading to the transformation process of GO from an electrically insulated state into an electrically conductive one. In this way, the alarm lamp and alarm buzzer connected with the GO thermosensitive sensor will send out the alerts to people immediately for taking emergency actions. After the surface modification with polydopamine of GO (PGO), the sensitivity and flame retardancy of the GO thermosensitive sensor ar...

Fire Alarm Wallpaper Based on Fire-Resistant Hydroxyapatite Nanowire Inorganic Paper and Graphene Oxide Thermosensitive Sensor.

Efficient utilization of abundant solar energy for clean water generation is considered a sustainable and environment friendly approach to mitigate the global water crisis. For this purpose, this study reports a flexible fire-resistant photothermal paper by combining carbon nanotubes (CNTs) and fire-resistant inorganic paper based on ultralong hydroxyapatite nanowires (HNs) for efficient solar energy-driven water steam generation and water purification. Benefiting from the structural characteristics of the HN/CNT photothermal paper, the black CNT surface layer exhibits a high light absorbability and photothermal conversion capability, the HN-based inorganic paper acts as a thermal insulator with a high temperature stability, low thermal conductivity, and interconnected porous structure. By combining these advantages, high water evaporation efficiencies of 83.2% at 1 kW m-2 and 92.8% at 10 kW m-2 are achieved. In addition, the HN/CNT photothermal paper has a stable water evaporation capability during recycling and long-time usage. The promising potential of the HN/CNT photothermal paper for efficient production of drinkable water from both actual seawater and simulative wastewater samples containing heavy metal ions, dyes, and bacteria is also demonstrated. The highly flexible HN/CNT photothermal paper is promising for application in highly efficient solar energy-driven seawater desalination and wastewater purification.

Flexible Fire-Resistant Photothermal Paper Comprising Ultralong Hydroxyapatite Nanowires and Carbon Nanotubes for Solar Energy-Driven Water Purification.

Traditional paper made from plant cellulose fibers is easily destroyed by either liquid or fire. In addition, the paper making industry consumes a large amount of natural trees and thus causes serious environmental problems including excessive deforestation and pollution. In consideration of the intrinsic flammability of organics and minimizing the effects on the environment and creatures, biocompatible ultralong hydroxyapatite nanowires are an ideal building material for inorganic fire-resistant paper. Herein, a new kind of free-standing, highly flexible, superhydrophobic, and fire-resistant layered inorganic paper has been successfully prepared using ultralong hydroxyapatite nanowires as building blocks after the surface modification with sodium oleate. During the vacuum filtration, ultralong hydroxyapatite nanowires assemble into self-roughened setalike microfibers, avoiding the tedious fabrication process to construct the hierarchical structure; the self-roughened microfibers further form the inorgani...

Highly Flexible Superhydrophobic and Fire-Resistant Layered Inorganic Paper.

Fine particulate matter (PM) air pollution has been attracting much attention due to its great threat to human health. Herein, we report a new kind of air filter paper with high removal efficiencies for PM2.5 and PM10 prepared using ultralong hydroxyapatite (HAP) nanowires and cotton (CT) fibers as building blocks through a simple vacuum filtration process. Flexible and biocompatible ultralong HAP nanowires with lengths over 200 μm and diameters of approximately 20 nm are employed for significant improvement of the air filtration performance of commercial CT fibers. The ultralong HAP nanowires intertwine with CT fibers and form the highly porous HAP/CT air filter paper. In addition, by optimizing the proportion of HAP and CT, the as-prepared HAP/CT air filter paper exhibits high removal efficiencies of over 95% for PM2.5 and PM10; more importantly, it shows a lower pressure drop and a smaller thickness than a commercial breathing mask. Moreover, the fabrication of a large-sized HAP/CT air filter paper with desirable properties through a commercial sheet former is demonstrated. As a proof-of-concept, a homemade breathing mask is fabricated by imbedding the HAP/CT air filter paper into a commercial breathing mask. Furthermore, benefiting from the unique characteristics of ultralong HAP nanowires, other functions such as antibacterial activity can be achieved by the immobilization of silver nanoparticles as the representative bactericide, enabling the fabrication of multifunctional air filter paper. The experimental results suggest that the ultralong HAP nanowire-based air filter paper is promising for various applications in the environmental field.

Flexible hydroxyapatite ultralong nanowire-based paper for highly efficient and multifunctional air filtration

Inorganic aerogels have been attracting great interest owing to their distinctive structures and properties. However, the practical applications of inorganic aerogels are greatly restricted by their high brittleness and high fabrication cost. Herein, inspired by the cancellous bone, we have developed a novel kind of hydroxyapatite (HAP) nanowire-based inorganic aerogel with excellent elasticity, which is highly porous (porosity ≈ 99.7%), ultralight (density 8.54 mg/cm3, which is about 0.854% of water density), and highly adiabatic (thermal conductivity 0.0387 W/m·K). Significantly, the as-prepared HAP nanowire aerogel can be used as the highly efficient air filter with high PM2.5 filtration efficiency. In addition, the HAP nanowire aerogel is also an ideal candidate for continuous oil-water separation, which can be used as a smart switch to separate oil from water continuously. Compared with organic aerogels, the as-prepared HAP nanowire aerogel is biocompatible, environmentally friendly, and low-cost. Moreover, the synthetic method reported in this work can be scaled up for large-scale production of HAP nanowires, free from the use of organic solvents. Therefore, the as-prepared new kind of HAP nanowire aerogel is promising for the applications in various fields.

Zhi-Chao Xiong

Papers

Fire Alarm Wallpaper Based on Fire-Resistant Hydroxyapatite Nanowire Inorganic Paper and Graphene Oxide Thermosensitive Sensor.

Flexible Fire-Resistant Photothermal Paper Comprising Ultralong Hydroxyapatite Nanowires and Carbon Nanotubes for Solar Energy-Driven Water Purification.

Highly Flexible Superhydrophobic and Fire-Resistant Layered Inorganic Paper.

Flexible hydroxyapatite ultralong nanowire-based paper for highly efficient and multifunctional air filtration

Bioinspired Ultralight Inorganic Aerogel for Highly Efficient Air Filtration and Oil-Water Separation.