A hydrophilic hyperbranched polyester (poly (tetramethylol acetylenediurea (TA)-CO-succinyl chloride) (PTS)) was proposed to be used as an organic additive in aqueous ZnSO4 electrolyte to achieve a highly reversible zinc/manganese oxide battery. It is found that the zinc symmetric battery based on the 2.0 wt.% PTS/ZnSO4 electrolyte showed a long cycle stability of more than 2400 h at 1.0 mA·cm−2, which is much longer than that including the blank ZnSO4 electrolyte (140 h). Furthermore, the capacity retention of the Zn||MnO2 full cells employing the 2.0 wt.% PTS/ZnSO4 electrolyte remained 85% after 100 cycles at 0.2 A·g−1, which is much higher than 20% capacity retention of the cell containing the blank ZnSO4 electrolyte, and also greater than 59.6% capacity retention of the cell including the 10.0 wt.% TA/ZnSO4 electrolyte. By using 2.0 wt.% PTS/ZnSO4 electrolytes, the capacity retention of the Zn||MnO2 full cells even reached 65% after 2000 cycles at a higher current density of 1.0 A·g−1. It is further demonstrated that the PTS was firmly adsorbed on the zinc anode surface to form a protective layer.
The incorporation of mechanophores, motifs that transform mechanical stimulus into chemical reaction or optical variation, allows creating materials with stress-responsive properties. The most widely used mechanophore generally features a weak bond, but its cleavage is typical an irreversible process. Here, we showed that this problem can be solved by folding–unfolding of a molecular tweezer. We systematically studied the mechanochromic properties of polyurethanes with cyano-substituted oligo(p-phenylene) vinylene (COP) tweezer (DPU). As a control experiment, a class of polyurethanes containing only a single COP moiety (MPU) was also prepared. The DPU showed prominent mechanochromic properties, due to the intramolecular folding–unfolding of COP tweezer under mechanical stimulus. The process was efficient, reversible and optical detectable. However, due to the disability to form either intramolecular folding or intermolecular aggregation, the MPU sample was mechanical inert.
Hemostatic dressings with multiple functions are superior to current hemostatic dressings for use in the complex situation of emergency accidents. In particular, the existing dressings lack consideration for the prevention of hypothermic shock after massive hemorrhage. In this study, gelatin (GN) and oxidized pectin (OP) were used for Schiff base cross-linking, and then polyvinyl alcohol (PVA) solution mixed with hemostatic caffeic acid (CA) was introduced to obtain aerogel substrate material (CB) after lyophilization. Polydimethylsiloxane (PDMS) and silver nanowires (Ag NWs) were used to construct a hydrophobic layer, an antibacterial layer and an infrared reflective layer on both sides of CB to prepare a multifunctional aerogel wound dressing with heat preservation, antifouling, hemostasis and antibacterial properties (PDMS-Ag NW-CB). The results showed that the infrared transmittance of PDMS-Ag NW-CB is almost 0, so that thermal energy loss from the body is minimized. The contact angles with water and blood are 129° and 120°, respectively, which have the effect of antifouling. This dressing can absorb blood quickly within 10 min, adhere to and gather platelets, and achieve hemostasis. It has good antibacterial and biocompatibility. Therefore, PDMS-Ag NW-CB has great potential in application to emergency treatment.
Despite more than a decade of study, there are still significant obstacles to overcome before graphene can be successfully produced on a large scale for commercial use. Chemical oxidation of graphite to produce graphene oxide (GO), followed by a subsequent reduction process to synthesize reduced graphene oxide (rGO), is considered the most practical method for mass production. Microorganisms, which are abundant in nature and inexpensive, are one of the potential green reductants for rGO synthesis. However, there is no recent review discussing the reported microbial reduction of GO in detail. To address this, we present a comprehensive review on the reduction of GO by a range of microorganisms and compared their efficacies and reaction conditions. Also, presented were the mechanisms by which microorganisms reduce GO. We also reviewed the recent advancements in using microbially reduced GO as the anode and cathode material in the microbial fuel cell (MFC) and algal biophotovoltaics (BPV), as well as the challenges and future directions in microbial fuel cell research.
In the research for the safe and efficiently antibacterial cotton fabrics to minimize risk for human health, an organic–inorganic hybrid material of ZnO nanoparticles (NPs) and quaternary ammonium salt (QAS) was employed to modify cotton fabrics by a dipping–padding–drying method. The synergistic effects of ZnO NPs and QAS on the structure and antibacterial properties of cotton fabrics were studied in detail. Results displayed that the QAS and ZnO NPs were immobilized firmly in cotton fabric by the formation of chemical covalent bonds and silica gel structure. ZnO/QAS/cotton had a good inhibitory effect on the growth of E. coli and S. aureus, with superior antibacterial efficiency of >99.99%. ZnO/QAS/cotton preserved good mechanical property, water absorbability, and limpness. We also provided a detailed analysis of antibacterial mechanism for the hybrid materials. The contact mechanism and the Zn2+ release were considered as the main mechanisms for the ZnO/QAS/cotton, while the reactive oxygen species (ROS) generation only had a little contribution to the antibacterial activity. In short, the excellent integrated properties endowed the hybrid cotton fabrics as potential application in many fields, like healthcare, food packaging.
Processing biomaterials into porous scaffolds for bone tissue engineering is a critical and a key step in defining and controlling their physicochemical, mechanical, and biological properties. Biomaterials such as polymers are commonly processed into porous scaffolds using conventional processing techniques, e.g., salt leaching. However, these traditional techniques have shown unavoidable limitations and several shortcomings. For instance, tissue-engineered porous scaffolds with a complex three-dimensional (3D) geometric architecture mimicking the complexity of the extracellular matrix of native tissues and with the ability to fit into irregular tissue defects cannot be produced using the conventional processing techniques. 3D printing has recently emerged as an advanced processing technology that enables the processing of biomaterials into 3D porous scaffolds with highly complex architectures and tunable shapes to precisely fit into irregular and complex tissue defects. 3D printing provides computer-based layer-by-layer additive manufacturing processes of highly precise and complex 3D structures with well-defined porosity and controlled mechanical properties in a highly reproducible manner. Furthermore, 3D printing technology provides an accurate patient-specific tissue defect model and enables the fabrication of a patient-specific tissue-engineered porous scaffold with pre-customized properties.
The catalytic conversion of biomass platform chemicals using abundant non-noble metal nanocatalysts is a challenging topic. Here, high-density cobalt oxide nanoparticles loaded on biomass-derived porous N-doped carbon (NC) was fabricated by a tandem hydrothermal pyrolysis and mild nitrate decomposition process, which is a green and cheap preparation method. The Co3O4 nanoparticles with the average size of 12 nm were uniformly distributed on the porous NC. The nanocomposites also possessed large surface area, high N content, good dispersibility in isopropanol, and furfural absorbability. Due to these characteristics, the novel cobalt nanocatalyst exhibited high catalytic activity for producing furfuryl alcohol, yielding 98.7% of the conversion and 97.1% of the selectivity at 160 °C for 6 h under 1 bar H2. The control experiments implied that both direct hydrogenation and transfer hydrogenation pathways co-existed in the hydrogenation reaction. The excellent catalytic activity of Co3O4@NC was attributed to the cooperative effects of porous NC and Co3O4 nanoparticles. This approach provides a new idea to design effective high-density non-noble metal oxide nanocatalysts for hydrogenation reactions, which can make full use of sustainable natural biomass.
Developing high-activity and low-cost catalysts is the key to eliminate the limitation of sluggish anodic oxygen evolution reaction (OER) during electrocatalytic overall water splitting. Herein, Ni‒Fe/black phosphorous (BP) composites are synthesized using a simple three-electrode system, where exfoliation of bulky BP and synthesis of NiFe composites are simultaneously achieved. Under light illumination, the optimized Ni‒Fe/BP composite exhibits excellent photoelectrocatalytic OER performance (e.g., the overpotential is 58 mV lower than a commercial RuO2 electrocatalyst at a current density of 10 mA·cm−2). The electron transfer on this composite is proved to follow a Ni‒BP‒Fe pathway. The electronic structure of this Ni‒Fe/BP composite is effectively regulated, leading to optimized adsorption strength of the intermediate OH* and improved intrinsic activity for the OER. Together with active sites on the support, this Ni‒Fe/BP composite possesses abundant electrochemical active sites and a bug surface area for the OER. The introduction of light further accelerates the electrocatalytic OER. This work provides a novel and facile method to synthesize high-performance metal/BP composites as well as the approaches to reveal their OER mechanisms.
In order to provide a biomimetic natural extracellular matrix microenvironment with excellent mechanical capacity for tissue regeneration, a novel porous hybrid glycidyl methacrylate-modified silk fibroin/poly(L-lactic acid-co-ε-caprolactone)–polyethylene glycol diacrylate (SFMA/P(LLA-CL)–PEGDA) hybrid three-dimensional (3D) nanofibrous scaffolds was successfully fabricated through the combination of 3D nanofibrous platforms and divinyl PEGDA based photocrosslinking, and then further improved water resistance by ethanol vapor post-treatment. Scanning electron microscopy and micro-computed tomography results demonstrated significant PEGDA hydrogel-like matrices bonded nanofibers, which formed a 3D structure similar to that of “steel bar (nanofibers)‒cement (PEGDA)”, with proper pore size, high porosity, and high pore connectivity density. Meanwhile, the hybrid 3D nanofibrous scaffolds showed outstanding swelling properties as well as improved compressive and tensile properties. Furthermore, these hybrid 3D nanofibrous scaffolds could provide a biocompatible microenvironment, capable of inducing the material‒cell hybrid and regulating human umbilical vein endothelial cells proliferation. They thus present significant potential in tissue regeneration.
As a new type of luminescent material, carbon dots (CDs) have attracted increased attention for their superior optical properties in recent years. However, solid-state fluorescent CDs, especially with red emission, are still a major challenge. Here, CDs with solid-state red emission were synthesized by co-doping of N and B using the one-step microwave method. The CD powder exhibits excitation-independent solid-state red fluorescence without any dispersion matrices, with optimum solid-state fluorescence wavelength of 623 nm. The hydrogen bonding interaction in CDs is helpful for solid-state fluorescence of CDs. The IG/ID value of CDs reaches up to 3.49, suggesting their very high graphitization degree, which is responsible for their red emission. In addition, CDs show the concentration-induced multicolor emission, which is attributed to the decreased energy gap in the high concentrated CD solution. To exploit their concentration-dependent emission, CDs with changing ratio in matrices are applied as a color-converting layer on ultraviolet chip to fabricate multicolor light-emitting diodes with light coordinates of (0.33, 0.38), (0.41, 0.48), (0.49, 0.44), and (0.67, 0.33), which belong to green, yellow, orange, and red light, respectively.
Sintering resistant noble metal nanoparticles are critical to the development of advanced catalysts with high activity and stability. Herein, we reported the construction of highly dispersed Pd nanoparticles loaded at the inner wall of ZrO2 hollow spheres (Pd@HS-ZrO2), which shows improved activity and thermal stability over references in the Pd-ZrO2 (catalyst-support) system. Even after 800 °C high temperature calcination, the Pd nanoparticles and ZrO2 hollow spheres did not undergo morphological changes. The Pd@HS-ZrO2 manifests batter catalytic activity and thermal stability than the counterpart Pd/ZrO2 catalysts. In comparison to Pd/ZrO2-800, Pd@ZrO2-800 exhibits a 25°C reduction in the temperature required for complete conversion of CO. The enhanced catalytic activity and thermal stability of Pd@HS-ZrO2 can be attributed to the nanoconfinement effect offered by the 10 nm wall thickness of the ZrO2 hollow spheres, which suppresses the coarsening of the Pd nanoparticles (active center for catalysis).
