Role of microfibril angle in molecular deformation of cellulose fibrils in Pinus massoniana compression wood and opposite wood studied by in-situ WAXS.

Upon tensile stress, the spiral cellulose fibrils in wood cell walls rotate like springs with decreasing microfibril angle (MFA), and the cellulose molecules elongate in the chain direction. Compression wood with high MFA and opposite wood with low MFA were comparatively studied by in-situ tensile tests combined with synchrotron radiation WAXS in the present study. FTIR spectroscopy revealed that compression wood had a higher lignin content and fewer acetyl groups. For both types of wood, the lattice spacing d004 increased and the MFA decreased gradually with the increase of tensile stress. At stresses beyond the yield point, cellulose lattice strain depended linearly on macroscopic stress, while the MFA depended linearly on macroscopic strain. The deformation mechanisms of compression wood and opposite wood are not essentially different but differ in their deformation behavior. Specifically, the contribution ratio of lattice strain and cellulose fibril reorientation to macroscopic strain was 0.25 and 0.53 for compression wood, and 0.40 and 0.33 for opposite wood, respectively. Due to the geometric effects of MFA, a greater contribution of cellulose fibril reorientation to the macroscopic deformation was detected in compression wood than in opposite wood.

JUJUNCAO-Stem-Based Interfacial Solar-Driven Evaporator with Natural Two-Phase Composite Structures of Functional Partition and Inherent Ultralow Vaporization Enthalpy of Water for Stable and Efficient Steam Production.

The interfacial solar-driven evaporation has been deemed as an environmentally friendly approach for freshwater generation. Nevertheless, there is still a challenge to obtain solar evaporators with efficient vapor production from low-cost and renewable biomass through a simple preparation process. Herein, the JUJUNCAO stem was selected as the substrate material, and a kind of interfacial solar-driven evaporator with natural two-phase composite structures and inherent ultralow water vaporization enthalpy was constructed by a dip-coating process. The natural two-phase composite structures were utilized as independent functional partition: the low-tortuosity and hydrophilic vascular bundles served as hierarchical channels for rapid water transportation and continuous steam escape, and the honeycomb-like parenchyma cells were considered natural heat insulators for effective thermal management. Furthermore, the JUJUNCAO stem exhibited inherent ultralow water vaporization enthalpy which was only 1.15 kJ g-1. Benefiting from the natural two-phase composite structures of functional partition and inherent ultralow water vaporization enthalpy, the C-Js evaporator could achieve an evaporation rate of 2.77 kg m-2 h-1 with an efficiency of 85.6% under 1 sun illumination. Meanwhile, the C-Js exhibited a stable and ideal evaporation performance and metal ion rejection behavior in the actual brine desalination process. Owing to the cost-effective and simple pretreatment process, the C-Js evaporator has the potential for freshwater generation in undeveloped areas.

Adsorption characteristics and mechanism of ammonia nitrogen and phosphate from biogas slurry by Ca2+-modified soybean straw biochar.

The utilization of biogas slurry is critical for the sustainable development of animal husbandry. Biomass carbon adsorption is a feasible method for the recycling of nutrients from biogas slurry. However, research on the co-adsorption of ammonia nitrogen and phosphate is scarce. Herein, soybean straw was utilized as the raw material to prepare Ca2+-modified biochar (CaSSB), which was investigated for its ammonia nitrogen and phosphate adsorption mechanisms. Compared with natural biochar (SSB), CaSSB possesses a high H/C ratio, larger surface area, high porosity and various functional groups. Ca2+-modified soybean straw biochar exhibited excellent adsorption performance for NH4+-N (103.18 mg/g) and PO43--P (9.75 mg/g) at pH = 6, using an adsorbent dosage of 2 g/L. The experimental adsorption data of ammonia nitrogen by CaSSB corresponded to pseudo-second-order kinetics and the Langmuir isotherm model, suggesting that the adsorption process was homogeneous and that electrostatic attraction might be the primary adsorption mechanism. Meanwhile, the adsorption of phosphate conformed to pseudo-second-order kinetics and the Langmuir-Freundlich model, whose mechanism might be attributed to ligand exchange and chemical precipitation. These results reveal the potential of CaSSBs as a cost-effective, efficient adsorbent for the recovery of ammonium and phosphate from biogas slurry.

Why Do Bamboo Parenchyma Cells Show Higher Nanofibrillation Efficiency than Fibers: An Investigation on Their Hierarchical Cell Wall Structure.

The cell walls of parenchyma cells and fibers in bamboo are both highly lignified with secondary thickening. However, the former were found to have much higher nanofibrillation efficiency than fibers via both protocols of ultrasonication and high pressure homogenization. To elucidate the inherent mechanism, detailed comparisons of chemical composition, cell morphology, cell wall density, pore structures, and structural organization of cell wall polymers were performed on native and pretreated cell walls of both parenchyma cells and fibers. Chemical compositional analysis showed that fibers have much higher cellulose (49.8% to 35.5%) but lower xylan content (21.1% to 36.2%) than parenchyma, while their lignin contents were similar (24.9% vs 22.9%). Polarized FTIR further revealed clear differences in the structural organization of polymers between the two types of cells, with all the polymers of fibers being more orderly assembled than those of parenchyma cells. The compact arrangement of polymers in the fibers was also supported by the much higher cell wall density (1.52 vs 1.28 g/cm3) and lower porosity (0.007 vs 0.013 cc/g after chemical pretreatments), as compared to the parenchyma cells. The study provides evidence that the anatomical characteristics of huge cavity-wall ratio, higher cell wall porosity, and less ordered arrangement of cell wall matrix polymers (mainly lignin) in parenchyma cells contribute to their higher nanofibrillation efficiency compared to fibers.

A Comparative Investigation on Structural and Chemical Differences between the Pith and Rind of Sunflower Stalk and Their Influences on Nanofibrillation Efficiency.

The structure and chemical composition of cell walls play a vital role in the bioconversion and utilization of plants. In the present study, the cell wall structure and chemical composition of pith and rind from sunflower stalks were compared and correlated to their nanofibrillation efficiency with ultrasonic treatment. Mild chemical pretreatment using 1% or 4% NaOH without any bleaching process were applied prior to ultrasonication nanofibrillation. Significant structural and chemical differences were demonstrated between the pith and rind, with the former exhibiting a much lower lignin and hemicellulose contents, higher pectin, much looser cell structure and higher cell wall porosity than the latter. Alkaline treatment alone was sufficient to eliminate most of the hemicellulose and pectin from stalk pith, whereas only partial removal of hemicellulose and lignin was achieved for the woody rind part. After 30 min of ultrasonic treatment, the stalk pith exhibited fully defibrillated fibrils with a continuous and entangled micro/nanofibrillated network, whereas numerous micron-sized fiber and fragments remained for the rind. The results indicated that stalk pith is less recalcitrant and easier to be fibrillated with ultrasonication than rind, which must be correlated to their distinct differences in both structure and chemical composition.

Sunflower-Stalk-Based Solar-Driven Evaporator with a Confined 2D Water Channel and an Enclosed Thermal-Insulating Cellular Structure for Stable and Efficient Steam Generation.

Given the worsening freshwater scarcity around the world, the interfacial solar-driven steam generation for seawater desalination and wastewater treatment has attracted wide attention due to its rich energy resources, convenience, and environmental friendliness. However, challenges still remain for developing high-efficiency interfacial solar-driven steam generation devices from low-cost, readily available, and green material resources. Herein, taking advantage of the delicate composite structure of the sunflower stalk, a sunflower-stalk-based solar-driven evaporator with a confined two-dimensional (2D) water supply pathway and an enclosed thermal-insulating structure is reported. The pith of sunflower stalks is composed of well-arranged honeycomb-like parenchyma cells that endow sunflower stalks with low thermal conductivity comparable to that of synthetic plastic foam. The low-tortuosity vascular bundles in the skin can serve as a natural 2D water pathway for rapid water transportation. The benefit of these functions is that an evaporator based on a carbon-nanotube-coated sunflower stalk (C-Ss) achieves a high evaporation rate of 1.76 kg m-2 h-1 under 1 sun irradiation (1 kW m-2). The C-Ss also shows a highly stable evaporation performance, high ion rejection efficiency, and a self-cleaning ability during the actual seawater desalination process. With advantages of abundant resources, easy fabrication, and sustainability, this C-Ss-based evaporator provides a promising choice for freshwater production in developing regions.

Flexible Salt-Rejecting Photothermal Paper Based on Reduced Graphene Oxide and Hydroxyapatite Nanowires for High-Efficiency Solar Energy-Driven Vapor Generation and Stable Desalination.

Vapor generation using solar energy is emerging as an efficient technology for wastewater purification and seawater desalination to relieve global water crisis. However, salt deposition on the evaporation surface seriously impairs the long-term steady water evaporation performance. Herein, the flexible salt-rejecting photothermal paper comprising reduced graphene oxide (rGO) and ultralong hydroxyapatite nanowires (HNs) has been developed for high-performance solar energy-driven water evaporation and stable desalination of seawater. The rGO/HN photothermal paper has advantages such as the hierarchical porous structure, interconnected channels, high mechanical strength, high efficiencies of solar light absorption and photothermal conversion, fast water transportation, and good heat insulation and salt-rejecting properties. Furthermore, the hydrophilicity and hydrophobicity of the rGO/HN photothermal paper can be adjusted by regulating the thermal treatment time. The water evaporation rate and energy efficiency of the hydrophilic rGO/HN photothermal paper are 1.48 kg m-2 h-1 and 89.2%, respectively, under 1 sun illumination (1 kW m-2). The hydrophobic rGO/HN photothermal paper shows a long-time stable water evaporation and salt-rejecting performance in the process of seawater desalination. The flexible salt-rejecting rGO/HN photothermal paper can produce clean water from wastewater and seawater with high rejection rates of organic dyes, metal ions, and salt ions, and it is promising for applications in water purification and seawater desalination.

A salt-resistant Janus evaporator assembled from ultralong hydroxyapatite nanowires and nickel oxide for efficient and recyclable solar desalination.

Solar energy-driven interfacial water evaporation is a promising energy utilization technology in the field of seawater desalination and water purification. However, the accumulation of salt on the heating surface severely impairs the water evaporation performance and long-time stability. Herein, we demonstrate a new kind of photothermal paper comprising a high-temperature-resistant paper made from ultralong hydroxyapatite nanowires and glass fibers and black nickel oxide (NiO) nanoparticles for solar energy-driven desalination. Owing to the high photothermal conversion ability, fast water transportation in the air-laid paper, and good heat insulation, the hydrophilic HN/NiO photothermal paper can achieve efficient, stable and recyclable water evaporation performance. In addition, a Janus HN/NiO photothermal paper based on hydrophobic sodium oleate-modified ultralong hydroxyapatite nanowires has been developed, and it has a high water evaporation efficiency of 83.5% under 1 kW m-2 irradiation. In particular, with the bottom hydrophobic ultralong hydroxyapatite nanowire layer and water-transporting channels in the air-laid paper to facilitate salt exchange, the as-prepared Janus evaporator exhibits no salt accumulation on the surface, high performance and long-time stable desalination using simulated seawater (3.5 wt% NaCl). Furthermore, the Janus evaporator with the hydrophobic ultralong hydroxyapatite nanowire substrate can be extended to support other photothermal materials such as black titanium oxide (Ti2O3) and Ketjen black carbon. The as-prepared Janus HN/Ti2O3 and Janus HN/KB photothermal paper also exhibit salt-resistant desalination function. The as-prepared Janus salt-resistant photothermal paper with efficient, stable and recyclable merits has great potential in solar energy-driven desalination and water purification.

Light-Operated Dual-Mode Propulsion at the Liquid/Air Interface Using Flexible, Superhydrophobic, and Thermally Stable Photothermal Paper.

The direct transformation of external energy into mechanical work by the self-propelled motor inspires and promotes the development of miniaturized machines. Several strategies have been utilized to realize the self-driven motion, but in some cases multiple power sources are needed, and this would complicate the operation in diverse environments. In this regard, the dual-mode self-propelled system based on a single power source is highly desirable. In this work, single-light-actuated dual-mode propulsion at the liquid/air interface is realized by using flexible, superhydrophobic, and thermostable photothermal paper made from flexible ultralong hydroxyapatite nanowires, titanium sesquioxide (Ti2O3) particles, and poly(dimethylsiloxane) coating. The superhydrophobic surface enables the thermostable photothermal paper to float on the water surface spontaneously and significantly reduces the drag force. In the usual situation, the heat power produced by the photothermal effect is utilized to trigger the Marangoni propulsion. While the Marangoni effect is quenched in water containing the surfactant, the propulsion mode can be directly switched into the vapor-enabled propulsion mode by simply increasing the light power density. Particularly, the light-driven motion in a linear, curvilinear, or rotational manner can be realized by designing the self-propelled machines with appropriate shapes by using the processable photothermal paper. It is expected that the as-prepared dual-mode self-propelled, flexible, superhydrophobic, and thermostable photothermal paper-based devices have promising applications in various fields such as microrobots, biomedicine, and environmental monitoring.

Secret Paper with Vinegar as an Invisible Security Ink and Fire as a Decryption Key for Information Protection.

Security inks based on photoluminescent materials are mostly investigated for security applications, such as information encryption and decryption, anti-counterfeiting, and data storage. Although they are invisible to the naked eye under ambient light, they can be detected under ultraviolet or near-infrared light. Herein, a new kind of secret paper made from network-structured ultralong hydroxyapatite nanowires and cellulose fibers has been developed. White vinegar, a common cooking ingredient, is used as an invisible security ink. Covert information on the secret paper written with white vinegar is totally invisible under natural light, but it can be decrypted and clearly read after exposure to fire; the response time to fire is short (<10 s). The ways of writing on the secret paper are diverse by using various pens loaded with white vinegar.

Bioinspired Macroscopic Ribbon Fibers with a Nacre-Mimetic Architecture Based on Highly Ordered Alignment of Ultralong Hydroxyapatite Nanowires.

A variety of biological materials in natural organisms supply a rich source of structural design guidelines and inspirations for the construction of advanced structural materials with excellent mechanical properties. In this work, inspired by the natural nacre and human bone, a kind of flexible macroscopic ribbon fiber made from highly ordered alignment of ultralong hydroxyapatite (HAP) nanowires and sodium polyacrylate (PAAS) with a "brick-and-mortar" layered structure has been developed by a scalable and convenient wet-spinning method. The quasi-long-range orderly liquid crystal of one-dimensional ultralong hydroxyapatite nanowires is employed and spun into the continuous flexible macroscopic ribbon fiber. In this work, highly ordered ultralong HAP nanowires act as the hard "brick" and PAAS acts as the soft "mortar", and the nacre-mimetic layered architecture is obtained. The as-prepared flexible macroscopic HAP/PAAS ribbon fiber exhibits superior mechanical properties, and the maximum tensile strength and Young's modulus are as high as 203.58 ± 45.38 MPa and 24.56 ± 5.35 GPa, respectively. In addition, benefiting from the excellent flexibility and good knittability, the as-prepared macroscopic HAP/PAAS ribbon fiber can be woven into various flexible macroscopic architectures. Additionally, the as-prepared flexible macroscopic HAP/PAAS ribbon fiber can be further functionalized by incorporation of various functional components, such as magnetic and photoluminescent constituents. The as-prepared flexible macroscopic HAP/PAAS ribbon fiber has potential applications in various fields such as smart wearable devices, optical devices, magnetic devices, and biomedical engineering.

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

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.

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

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 are further improved, resulting in a low responsive temperature (126.9 °C), fast response (2 s), and sustained working time in the flame (at least 5 min). Compared with combustible commercial wallpaper, the smart fire alarm wallpaper based on HNs and GO (or PGO) is superior owing to excellent nonflammability and high-temperature resistance of HNs, which can protect the GO (or PGO) thermosensitive sensor from the flames. The smart fire alarm wallpaper can be processed into various shapes, dyed with different colors, and printed with the commercial printer and thus has promising applications in high-safety interior decoration of houses.

Low-Cost and Scaled-Up Production of Fluorine-Free, Substrate-Independent, Large-Area Superhydrophobic Coatings Based on Hydroxyapatite Nanowire Bundles.

To date, the scaled-up production and large-area applications of superhydrophobic coatings are limited because of complicated procedures, environmentally harmful fluorinated compounds, restrictive substrates, expensive equipment, and raw materials usually involved in the fabrication process. Herein, the facile, low-cost, and green production of superhydrophobic coatings based on hydroxyapatite nanowire bundles (HNBs) is reported. Hydrophobic HNBs are synthesised by using a one-step solvothermal method with oleic acid as the structure-directing and hydrophobic agent. During the reaction process, highly hydrophobic C-H groups of oleic acid molecules can be attached in situ to the surface of HNBs through the chelate interaction between Ca2+ ions and carboxylic groups. This facile synthetic method allows the scaled-up production of HNBs up to about 8 L, which is the largest production scale of superhydrophobic paint based on HNBs ever reported. In addition, the design of the 100 L reaction system is also shown. The HNBs can be coated on any substrate with an arbitrary shape by the spray-coating technique. The self-cleaning ability in air and oil, high-temperature stability, and excellent mechanical durability of the as-prepared superhydrophobic coatings are demonstrated. More importantly, the HNBs are coated on large-sized practical objects to form large-area superhydrophobic coatings.

Hydroxyapatite Nanowire-Based All-Weather Flexible Electrically Conductive Paper with Superhydrophobic and Flame-Retardant Properties.

How to survive under various harsh working conditions is a key challenge for flexible electronic devices because their performances are always susceptible to environments. Herein, we demonstrate the novel design and fabrication of a new kind of the all-weather flexible electrically conductive paper based on ultralong hydroxyapatite nanowires (HNs) with unique combination of the superhydrophobic surface, electrothermal effect, and flame retardancy. The superhydrophobic surface with water repellency stabilizes the electrically conductive performance of the paper in water. For example, the electrical current through the superhydrophobic paper onto which water droplets are deposited shows a little change (0.38%), and the electrical performance is steady as well even when the paper is immersed in water for 120 s (just 3.65% change). In addition, the intrinsic electrothermal effect of the electrically conductive paper can efficiently heat the paper to reach a high temperature, for example, 224.25 °C, within 10 s. The synergistic effect between the electrothermal effect and superhydrophobic surface accelerates the melting and removal of ice on the heated electrically conductive paper. Deicing efficiency of the heated superhydrophobic electrically conductive paper is ∼4.5 times that of the unheated superhydrophobic electrically conductive paper and ∼10.4 times that of the heated superhydrophilic paper. More importantly, benefiting from fire-resistant ultralong HNs, thermally stable Ketjen black, and Si-O backbone of poly(dimethylsiloxane), we demonstrate the stable and continuous service of the as-prepared electrically conductive paper in the flame for as long as 7 min. The electrical performance of the electrically conductive paper after flame treatment can maintain as high as 90.60% of the original value. The rational design of the electrically conductive paper with suitable building materials and structure demonstrated here will give an inspiration for the development of new kinds of all-weather flexible electronic devices that can work under harsh conditions.

Luminescent, Fire-Resistant, and Water-Proof Ultralong Hydroxyapatite Nanowire-Based Paper for Multimode Anticounterfeiting Applications.

Counterfeiting of valuable certificates, documents, and banknotes is a serious issue worldwide. As a result, the need for developing novel anticounterfeiting materials is greatly increasing. Herein, we report a new kind of ultralong hydroxyapatite nanowire (HAPNW)-based paper with luminescence, fire resistance, and waterproofness properties that may be exploited for anticounterfeiting applications. In this work, lanthanide-ion-doped HAPNWs (HAPNW:Ln3+) with lengths over 100 µm have been synthesized and used as a raw material to fabricating a free-standing luminescent, fire-resistant, water-proof paper through a simple vacuum filtration process. It is interesting to find that the luminescence intensity, structure, and morphology of HAPNW:Ln3+ highly depend on the experimental conditions. The as-prepared HAPNW:Ln3+ paper has a unique combination of properties, such as high flexibility, good processability, writing and printing abilities, luminescence, tunable emission color, waterproofness, and fire resistance. In addition, a well-designed pattern can be embedded in the paper that is invisible under ambient light but viewable as a luminescent color under ultraviolet light. Moreover, the HAPNW:Ln3+ paper can be well-preserved without any damage after being burned by fire or soaked in water. The unique combination of luminescence, fire resistance, and waterproofness properties and the nanowire structure of the as-prepared HAPNW:Ln3+ paper may be exploited toward developing a new kind of multimode anticounterfeiting technology for various high-level security antiforgery applications, such as in making forgery-proof documents, certificates, labels, and tags and in packaging.

Ultralong Hydroxyapatite Nanowires-Based Paper Co-Loaded with Silver Nanoparticles and Antibiotic for Long-Term Antibacterial Benefit.

Hydroxyapatite is a kind of biocompatible, environmentally friendly, and versatile inorganic biomaterial. Herein, the preparation of ultralong hydroxyapatite nanowires (HAPNWs)-based antibacterial paper co-loaded with silver nanoparticles (AgNPs) and antibiotic is reported. HAPNWs are used to prepare AgNPs in situ using an aqueous solution containing AgNO3 under the sunlight without added reducing agent at room temperature. Subsequently, ciprofloxacin (CIP) as an antibiotic is loaded on the HAPNWs@AgNPs. The resultant HAPNWs@AgNPs-CIP paper possesses several unique properties, including high flexibility, high Brunauer-Emmett-Teller (BET) specific surface area (47.9 m2 g-1), high drug loading capacity (447.4 mg g-1), good biocompatibility, sustained and pH-responsive drug release behavior (5.40-6.75% of Ag+ ions and 37.7-76.4% of CIP molecules at pH values of 7.4-4.5 at day 8, respectively), and reusable recycling. In the antibacterial tests against Escherichia coli and Staphylococcus aureus, the HAPNWs@AgNPs-CIP paper exhibits large diameters of inhibition zones and low minimum inhibitory concentrations (30 and 40 µg mL-1), revealing the high antibacterial activity. Besides, the consecutive agar diffusion tests (8 cycles), long-term stability tests (over 56 days), and continuous contamination tests (5 cycles) demonstrate the excellent recycling performance and long-term antibacterial activity of the HAPNWs@AgNPs-CIP paper. These results indicate a promising potential of the HAPNWs@AgNPs-CIP bactericidal paper for tackling public health issues related to bacterial infections.

Hydroxyapatite Nanowire@Magnesium Silicate Core-Shell Hierarchical Nanocomposite: Synthesis and Application in Bone Regeneration.

Multifunctional biomaterials that simultaneously combine high biocompatibility, biodegradability, and bioactivity are promising for applications in various biomedical fields such as bone defect repair and drug delivery. Herein, the synthesis of hydroxyapatite nanowire@magnesium silicate nanosheets (HANW@MS) core-shell porous hierarchical nanocomposites (nanobrushes) is reported. The morphology of the magnesium silicate (MS) shell can be controlled by simply varying the solvothermal temperature and the amount of Mg2+ ions. Compared with hydroxyapatite nanowires (HANWs), the HANW@MS core-shell porous hierarchical nanobrushes exhibit remarkably increased specific surface area and pore volume, endowing the HANW@MS core-shell porous hierarchical nanobrushes with high-performance drug loading and sustained release. Moreover, the porous scaffold of HANW@MS/chitosan (HANW@MS/CS) is prepared by incorporating the HANW@MS core-shell porous hierarchical nanobrushes into the chitosan (CS) matrix. The HANW@MS/CS porous scaffold not only promotes the attachment and growth of rat bone marrow derived mesenchymal stem cells (rBMSCs), but also induces the expression of osteogenic differentiation related genes and the vascular endothelial growth factor (VEGF) gene of rBMSCs. Furthermore, the HANW@MS/CS porous scaffold can obviously stimulate in vivo bone regeneration, owing to its high bioactive performance on the osteogenic differentiation of rBMSCs and in vivo angiogenesis. Since Ca, Mg, Si, and P elements are essential in human bone tissue, HANW@MS core-shell porous hierarchical nanobrushes with multifunctional properties are expected to be promising for various biomedical applications such as bone defect repair and drug delivery.

Inorganic Nanowires-Assembled Layered Paper as the Valve for Controlling Water Transportation.

Layered materials with open interlayer channels enable various applications such as tissue engineering, ionic and molecular sieving, and electrochemical devices. However, most reports focus on the two-dimensional nanosheets-assembled layered materials, whose interlayer spacing is limited at the nanometer scale. Herein, we demonstrate that one-dimensional inorganic nanowires are the ideal building blocks for the construction of layered materials with open interlayer channels as well, which has not aroused much attention before. It is found that the relatively long inorganic nanowires are capable of assembling into free-standing layered paper with open interlayer channels during the filtration process. The spacings of interlayer channels between adjacent layers are up to tens of micrometers, which are much larger than those of the two-dimensional nanosheets-assembled layered materials. But the closed interlayer channels are observed when the relatively short inorganic nanowires are used as building blocks. The mechanism based on the relationship between the structural variation and the nanowires used is proposed, including the surface charge amplified effect, surface charge superimposed effect, and pillarlike supporting effect. According to the proposed mechanism, we have successfully fabricated a series of layered paper sheets whose architectures (including interlayer channels of cross section and pores on the surface) show gradient changes. The as-prepared layered paper sheets are employed as the valves for controlling water transportation. Tunable water transportation is achieved by the synergistic effect between in-plane interlayer channels (horizontal transportation) from the open to the closed states, and through-layer pores (vertical transportation) without surface modification or intercalation of any guest species.