Eco-friendly photothermal hydrogel evaporator for efficient solar-driven water purification.

The field of solar vapor generation has developed rapidly in recent years, but achieving the goals of a high evaporation rate, eco-friendliness and rapid preparation with low-cost raw materials is still a challenge. In this work, a type of photothermal hydrogel evaporator was prepared by blending eco-friendly poly(vinyl alcohol), agarose, Fe3+ and tannic acid (TA) together, in which the tannic acid-ferric ion (TA*Fe3+) complexes served as photothermal materials and effective gelators. The results indicate that the TA*Fe3+ complex exhibits excellent gelatinization ability and light-absorption performance, which leads to a compressive stress of 0.98 MPa at 80% strain and up to 85% light absorption ratio in the photothermal hydrogel. For interfacial evaporation, a high rate of 1.897 ± 0.11 kg·m-2·h-1 corresponding to an energy efficiency of 89.7 ± 2.73% under 1 sun irradiation is achieved. Moreover, the hydrogel evaporator exhibits high stability in a 12-hour test and a 20-cycle test without a decline in evaporation performance. The outdoor testing results show that the hydrogel evaporator can achieve an evaporation rate of > 0.70 kg/m2 and effectively purify wastewater treatment and seawater desalination.

Intramolecular-Catalyzed Vitrimers with White-Light Emission for Light-Emitting Diode Encapsulation.

Currently available encapsulating materials for white light-emitting diodes (WLEDs) have certain limitations, such as the toxicity of phosphors and the non-recyclable nature of the encapsulating materials. In this study, relatively promising encapsulating materials with two significant advantages are developed. First, the chips can be directly encapsulated without phosphors using luminescent encapsulating materials. Second, the encapsulating materials can be reprocessed for recycling via intramolecular catalysis. To this end, blue-light-emitting vitrimers (BEVs) are prepared by the reaction of epoxy resin with amines and are found to exhibit strong blue emission and fast stress relaxation via internal catalysis. To obtain white-light emission, a well-designed yellow component, perylenetetracarboxylic dianhydride, is grafted into the BEVs to generate white-light-emitting vitrimers (WEVs). A rare synergy of blue- and yellow-light emission affords white-light emission. When the WEV is used as an encapsulating adhesive for 365 nm LED chips without inorganic phosphors, stable white light with CIE coordinates (0.30, 0.32) is successfully achieved, indicating a promising future for WLED encapsulation.

Rapid Fabrication of Porous Photothermal Hydrogel Coating for Efficient Solar-Driven Water Purification.

Cost management and scalable fabrication without sacrificing the purification performance are two critical issues that should be addressed before the practical commercial application of solar-driven evaporators. To address this challenge, we report a porous photothermal hydrogel coating prepared by mixing the raw materials of sawdust (SD), carbon nanotubes (CNTs), and poly(vinyl alcohol) (PVA), which was applied to undergo a blading-drying-rehydration process to prepare the evaporator. In the coating, the crystallized PVA gives the coating a solid skeleton and the sawdust endows the coating with a loose structure to sufficiently enhance the water transportation capacity. As a result, the evaporator coated with the hydrogel coating displays a high water transport rate and efficient evaporation performance along with excellent mechanical properties and stability. Water migrates vertically upward 5 cm within 4 minutes. The compressive stress of the rehydrated hydrogel coating reaches as high as 14.28 MPa under 80% strain. The water evaporation rate of the hydrogel coating-based evaporator reaches 1.833 kg m-2 h-1 corresponding to an energy efficiency of 83.29% under 1 sun irradiation. What is more, the hydrogel coating retains its excellent evaporation performance and stability after immersion in acid or alkali solution, ultrasound treatment, and long-time immersion in water. Under outdoor conditions, the water evaporation rate of the hydrogel coating-based evaporator is about 5.69 times higher than that of pure water. This study proposes a rapid, cost-effective, and scalable strategy for preparing a high-performance photothermal hydrogel coating that will find sustainable and practical application in solar-driven water purification.

Laser-treated wood for high-efficiency solar thermal steam generation.

Solar-driven water vaporization is considered one of the most sustainable ways to solve water scarcity. The design of highly efficient solar absorber systems has received extensive attention. Here, we report a novel light absorption material for water evaporation using laser-treated wood. The obtained laser-treated wood possesses interconnected 3D porous networks formed by the random construction of carbon arrays and a hydrophilic surface due to the oxygen implantation by laser treatment. When under 1 sun solar-simulated light irradiation (1 kW m-2), the surface temperatures of dry and water-saturated wood reach 59.5 °C and 40.4 °C, respectively, indicating good heat localization. As a result, the laser-treated wood under 1 sun illumination shows high solar to vapor efficiencies of 93.1% and 92.6% for pure water and seawater, respectively, which are higher than that of most wood-based reported photo-thermal conversion materials. Therefore, the fabricated laser-treated wood may pave the way for harvesting solar energy to produce clean water at low cost.

Mechanically Robust and Reprocessable Acrylate Vitrimers with Hydrogen-Bond-Integrated Networks for Photo-3D Printing.

Reprocessable acrylate vitrimer needs to enhance its strength to expand the application in photo-three-dimensional (photo-3D) printing. However, the methods for improving mechanical properties by the addition of nanofillers or a multifunctional resin into acrylate vitrimers are inappropriate for photo-3D printing due to the low curing speed of photopolymerization induced by weakening light transmittance or reduction of dimensional accuracy caused by large shrinkage. At present, we demonstrate a new strategy for developing a kind of mechanically robust and reprocessable 3D printing thermosets by combining hydrogen bonds and exchangeable ß-hydroxyl esters into acrylate vitrimers. To realize this purpose, diacrylate prepolymer containing ß-hydroxyl esters was first synthesized from glycidyl methacrylate and suberic acid. Then, the resin formulations for 3D printing comprising the synthesized diacrylate prepolymer together with acrylamide generate exchanged ß-hydroxyl ester and pendent amide in cross-linked networks. Here, hydrogen bonds resulting from the amide group as sacrificial bonds dissipate vast mechanical energy under an external load. With the inclusion of 20 wt % acrylamide, the average tensile strength and Young's modulus are up to 40.1 and 871 MPa, which increased by about 4.4 and 3.85 times, respectively. The network rearrangement of cross-linked vitrimers can be achieved through the dynamic ester exchange reactions with gradual disappearance of hydrogen bonds at elevated temperatures, imparting reprocessability into the printed structures. Various photo-3D printing or UV irradiation shapes were successfully produced, and these dissolved in ethylene glycol could be remolded again.

Nanoscaled gold and silver: Simultaneous removal and transformation to functional materials.

Based on an "acid-assisted cool welding" technology which was realized by virtue of the freezing process in the presence of acid, nanoscaled gold (Au) and silver (Ag) from wastewater could be removed very facilely and efficiently. The technology was independence of the freezing temperature, size as well as shape of those nanoscaled units. Besides, some functional materials like porous nanostructures with highly and stably catalytic activity could be also obtained during the removal. Our research not only provided a new method to remove nanoscaled Ag or Au from wastewater, but also built up a unique route to transform those nano-units into functional materials simultaneously.

Hierarchically porous Pd nanospheres: facile synthesis and their application in HCOOH electrooxidation.

With the help of rhodamine B base (RBB), novel Pd nanospheres were synthesized by a facile one-step approach. Owing to their hierarchically porous characteristics, these nanospheres exhibited highly catalytic activity for HCOOH electrooxidation (∼1.84 times and 1.67 times higher than those of a commercial Pd/C catalyst for mass and specific activity, respectively).

Synthesis of Mesoporous Carbons from Rice Husk for Supercapacitors with High Energy Density in Ionic Liquid Electrolytes.

High-performance mesoporous carbons (MCs) for supercapacitors were made from rice husk by one-step microwave-assisted ZnCl2 activation. The microstructures of MCs as-made were characterized by field emission scanning electron microscopy and transmission electron microscopy. The pore structure parameters of MCs were obtained by N2 adsorption technique. The electrochemical properties of MC electrodes were studied by constant current charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy in different electrolytes. The results showed that the specific surface area of MC4 made at the ZnCl2/rice husk mass of 4:1 reached 1737 m2 g(-1). The specific capacitance and energy density of the electrodes fabricated from the mixture of MC4 and microporous carbon increased with the mass percentage of MC4, reaching 157 F g(-1) and 84 Wh kg(-1) at 0.05 A g(-1), and showed good cycle stability in 1-butyl-3-methylimidazolium hexafluorophosphate electrolyte. Compared to the often-used aqueous and organic electrolytes, MC4 capacitor exhibited extremely high energy density in ionic liquid electrolyte, remaining at 28 Wh kg(-1) at 1684 W kg(-1). This work paves a new way to produce cost-effective MCs from biomass for supercapacitors with extremely high energy density in ionic liquid electrolytes.

Perylenetetracarboxylic-metal assemblies and anisotropic charge transport in a Cu(II) assembly.

Structural diversity and uniformity of nanomaterials are usually prerequisites for many practical applications involving the oriented fabrication of various devices with full control over their desired physiochemical properties. Particularly in the optoelectronic field, ordered assembly inside cells is required not only for obtaining attractive configurations but also for playing an important role in the characteristics of photoconduction and conductivity. Here, we present a synergetic self-assembly driven by coordination and intermolecular interactions for the construction of organic-inorganic hybrids with multi-morphologies and tunable physical properties. 3,4,9,10-Perylenetetracarboxylic dianhydride was treated with base to produce various assemblies by coordination with metal ions, showing morphologies of nanowires, nanosheets, nanoribbons and nanorods. The organic π-spacer affords an extension in different directions through the suitable incorporation of metal ions with different coordination modes for the formation of metal-ligand complexes. Interestingly, the obtained nanorods were twisted rods with obvious screw threads on the rod wall, supporting the synergetic self-assembly. Then, anisotropic mobility measurements of the obtained Cu(2+)-ligand assembly were carried out to show the importance of the size- and shape-confined synthesis of the hybrids. By presenting a series of ordered metal-ligand complex superstructures driven by synergetic self-assembly, this work is expected to pave the way for future anisotropic measurements of complex assemblies.

The photoirradiation induced p-n junction in naphthylamine-based organic photovoltaic cells.

The bulk heterojunction (BHJ) plays an indispensable role in organic photovoltaics, and thus has been investigated extensively in recent years. While a p-n heterojunction is usually fabricated using two different donor and acceptor materials such as poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM), it is really rare that such a BHJ is constructed by a single entity. Here, we presented a photoirradiation-induced p-n heterojunction in naphthylamine-based organic photovoltaic cells, where naphthylamine as a typical p-type semiconductor could be oxidized under photoirradiation and transformed into a new semiconductor with the n-type character. The p-n heterojunction was realized using both the remaining naphthylamine and its oxidative product, giving rise to the performance improvement in organic photovoltaic devices. The experimental results show that the power conversion efficiency (PCE) of the devices could be achieved up to 1.79% and 0.43% in solution and thin film processes, respectively. Importantly, this technology using naphthylamine does not require classic P3HT and PCBM to realize the p-n heterojunction, thereby simplifying the device fabrication process. The present approach opens up a promising route for the development of novel materials applicable to the p-n heterojunction.

Nanoporous gold film: fabrication and role as a catalytic reactor.

Nanoporous gold (NPG) is attractive due to its high catalytic activity. From an applied and economical point of view, fabricating thin NPG films is recognized to be an ideal approach. Herein, we report an interesting finding that a thin NPG film with a thickness of 90 nm can be prepared on various substrates conveniently by using seed-mediated growth. The film has a nanoporous character with 30-60 nm and 10-30 nm of ligament and pore size, respectively. The high cost-efficiency, adjustable substrates, easy and convenient operation make this film reactor a good candidate for catalyzing both oxidative and hydrogenation reactions.

Compact large area and high-quality Au film with a hierarchical structure and its application in SERS.

We have described a novel and facile strategy for fabricating a compact large area and high-quality Au film with a hierarchical structure (HS) by using a polyaniline slice as a reductant. The unique morphology of the as-prepared Au HS film, which is controlled by the concentration of AuCl4(-), results in enhanced Raman signals toward probe molecules such as 4-aminothiophenol (4-ATP), 2-naphthalenethiol (2-NAT) and 4-mercaptobenzoic acid (4-MBA). The employed approach may shed some light on simultaneously fabricating and immobilizing unique Au micro/nanostructures.

Preparation and properties of nanometer titanium dioxide/silk fibroin blend membrane.

A novel nanometer titanium dioxide (nanoTD)/silk fibroin (SF) blend membrane was prepared and characterized by AFM, FTIR, DSC, and XRD. The strength, solubility and thermal properties and the antibacterial activity of the blend membrane were then investigated. The results show that at a nanoTD/SF weight ratio of 0.1%, nanoTD particles were evenly dispersed in the blend membrane. The blend membrane exhibited a crystalline 2theta XRD peak at 21.1 degrees and the decomposition temperature was 28.72 degrees C higher than for a pure SF membrane. The results show that the blend membrane had higher crystallinity and better antibacterial activity and strength than a pure SF membrane, whereas its solubility was lower.