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To enhance microwave loss abilities, constructing composites with one-dimensional (1D) structure is an excellent scheme. In this work, a high-efficiency microwave absorber of MnO nanograins decorated vanadium nitride/carbon nanofibers (MnO-VN/C NFs) was successfully prepared for the first time via co-electrospinning technology and subsequent nitriding treatment. Studying in detail the specific relationship between nitriding time and the morphology of the as-prepared NFs, the precipitations of MnO nanoparticles with tailored structures were attached on the surface of VN/C NFs to optimize their electromagnetic parameters. When the nitriding time was 2.0 h at 600 °C, the MnO-VN/C NFs displayed good microwave absorption performances: the minimum reflection loss (RL) value was -63.2 dB at 8.8 GHz, and the bandwidth of RL-10 dB was up to 6.4 GHz from 11.6 to 18 GHz at the thickness of 2.8 mm. Meanwhile, the absorption bandwidth (RL-10 dB) could cover the whole X and Ku band by adjusting the thickness, respectively. The outstanding performances could be attributed to the good impedance matching and various loss pathways including conductive loss and interfacial and dipole polarizations. In these regards, MnO-VN/C NFs are likely to be utilized as a high-efficiency microwave absorber. And the strategy in this work can provide great help to design other 1D structural microwave absorbers with a broader absorbing band.

Mesoporous alumina modified by silica (MA-S) with good thermal stability was prepared by a self-assembly method. The morphology and microstructure of as-prepared samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and so on. Though adding 5 wt% SiO2 in Al2O3 framework, the MA-S exhibited high thermal stability and large specific surface area (87 m2 g−1) at 1200 °C. The results indicated that SiO2 can suppress the phase transformation from γ-Al2O3 to α-Al2O3 and postpone the crystallization temperature at same time. Therefore, the as-prepared materials possess a great potential for application at high temperature.

CO2-monitoring plays an important role in medicine, environmental sciences, and food industries. Here, a new CO2-responsive hydrogel film was fabricated from branched polyethyleneimine (BPEI) and partially oxidized dextran (PO-Dex) via layer-by-layer (LBL) assembly, based on the in situ Schiff base reaction between the two polymers. The swelling behaviours of the films were studied using Fabry-Perot fringes on their reflection spectra. Like ordinary hydrogels, the BPEI/PO-Dex films swell in water. In addition, they swell to a larger degree when CO2 is introduced, due to the reaction between CO2 and the amino groups in BPEI. The CO2-induced swelling can be reported by the shift of the Fabry-Perot fringes on their reflection spectra; therefore, the BPEI/PO-Dex film can be used as an optical sensor for dissolved CO2. In the new sensor, the BPEI/PO-Dex film acts as a CO2-sensing material and Fabry-Perot cavity simultaneously. The introduction of ordered structure is no longer required. The response of the sensor to CO2 is linear and reversible. Unlike other hydrogel-based sensors that suffer from a slow response, the new sensor can respond to CO2 quickly, making it applicable for real-time, continuous monitoring of CO2 levels in solution.

Unsaturated metal species (UMS) confined in nanomaterials play important roles for electron transfer in a wide range of catalytic reactions. However, the limited fabrication methods of UMS restrict their wider catalytic applications. Here, we report on the synergy of unsaturated Zn and Cu dopants confined in carbon dots (ZnCu-CDs) to produce enhanced electron transfer and photooxidation processes in the doped CDs. The Zn/Cu species chelate with the carbon matrix mainly through Cu–O(N)–Zn–O(N)–Cu complexes. Within this structure, Cu2+ acts as a mild oxidizer that facilely increases the unsaturated Zn content and also precisely tunes the unsaturated Zn valence state to Znd+, where d is between 1 and 2, instead of Zn0. With the help of UMS, electron-transfer pathways are produced, enhancing both the electron-donating (7.0 times) and -accepting (5.3 times) abilities relative to conventional CDs. Because of these synergistic effects, the photocatalytic efficiency of CDs in photooxidation reactions is shown to ...

Herein, N-doped carbon coated vanadium nitride nanowires (VN@NC NWs) with inner porous structure were synthesized by coating a thin layer of a carbon precursor of polydopamine (PDA) on ultralong V2O5 NWs followed by nitridation. The amorphous carbon coating could ensure the one-dimensional (1D) structure, as well as produce the inner pores during nitriding progress. The formational 1D porous architecture, high-crystallized VN nanoparticles and homogeneous N-doped carbon coating synergistically improved the materials' impedance match and thus enhanced their microwave absorption performances. The minimum reflection loss (RLmin) of the optimal samples/paraffin hybrid with 20 wt% was −60.2 dB with an effective absorption bandwidth (EAB, RL

The three-dimensional graphene microspheres with well-defined shape and size were prepared successfully by a novel approach, i.e., a combination of microfluidic device and freeze-drying. In the synthetic process, a pragmatic and facile device has been designed for the controllable generation of uniform-sized droplets. Followed by freeze-drying, highly porous spherical graphene microballs were obtained for further research. It is worth noting that the size of the droplets can also be controlled by adjusting the flow rate ratio of each phase. Afterward, the morphology, structure and character of the three-dimensional graphene particles are characterized by scanning electron microscope, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Due to their highly porous structure, the as-prepared 3D graphene microspheres were employed as adsorbent. The adsorption capacity of acid orange 7 and Pb(II) was about 71.9 and 147.7 mg g−1, respectively. The results showed that the porous 3D graphene microspheres as adsorbent possessed excellent adsorption ability for organic and inorganic contaminants in this work, showing their potential applications in environmental pollutant treatment.

A novel quinone-modified metal-organic frameworks NH2-MIL-101(Fe) was synthesized using a simple chemical method under mild condition. The introduced 2-anthraquinone sulfonate (AQS) can be covalently modified with NH2-MIL-101(Fe) and acts as a redox mediator to enhance the degradation of bisphenol A (BPA) via persulfate activation. The obtained AQS-NH-MIL-101(Fe) was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectra, cyclic voltammetry and electrochemical impedance spectroscopy. AQS-NH-MIL-101(Fe) exhibited better catalytic performance compared with NH2-MIL-101(Fe) and NH2-MIL-101(Fe) with free AQS (NH2-MIL-101(Fe)/AQS). That is, AQS-NH-MIL-101(Fe) was proved to be the most effective in that more than 97.7% of BPA was removed. The degradation rate constants (k) of AQS-NH-MIL-101(Fe) was 9-fold higher than that of NH2-MIL-101(Fe) and 7-fold higher than NH2-MIL-101(Fe)/AQS, indicating that AQS is a great electron-transfer mediator when modified with NH2-MIL-101(Fe). Based on the above results, the possible mechanism of catalytic reaction has been investigated in view of the trapping experiments. In addition, the AQS-NH-MIL-101(Fe) catalyst exhibited excellent stability and can be used several times without significant deterioration in performance.

Self-propelled metal–organic framework (MOF)-based Janus micromotors that propel autonomously in hydrogen peroxide and display effective remediation of contaminated water is presented in this work. The novel Janus micromotors rely on the asymmetric deposition of a catalytically active Ag patch on the surface of MOF composite microspheres. The active Ag sites are used for the splitting of H2O2 to form oxygen bubbles. As a result, these Janus micromotors can reach a high speed of over 310 μm s−1 due to effective bubble propulsion, which is comparable to common Pt-based micromotors. By coupling the high catalytic capacity of MOFs with their autonomous propulsion, the MOF-based micromotors are shown to play a dominant role in the effective removal of organic pollutants. In addition, scanning electronic microscopy, Fourier-transform infrared spectroscopy and energy dispersive X-ray spectroscopy are performed to verify their morphology and composition. Based on the obtained results, a potential mechanism of the motion and the high catalytic activity is also proposed. It is expected that these energy saving micromotors with catalytic activity should be unprecedentedly spread in real applications.

Many abundant and inexpensive materials are being developed for the synthesis of carbon dots. However, the structures of most raw materials are complicated, which inevitably bring difficulties for the optimization of their photocatalytic ability, especially for the electron transfer properties. Herein, petroleum coke was selected as raw material to prepare carbon dots (CDs). The types and contents of the functional groups C O and/or S O) on CDs surface were finely tuned by facile chemical oxidation, enhancing both of the electron-accepting (11.9 and 3.5 times) and electron-donating abilities (1.7 and 1.4 times). The photocatalytic efficiency of the optimized carbon dots (C-120) in the photooxidation of 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate (1,4-DHP) is 6.6 times higher than that of CDs with few functionalized groups. The present study demonstrates a feasible and effective strategy to solve the poor electron transfer difficulty of CDs and also helps to understand the regulating strategies and mechanisms of surface structure.

The outstanding visible light response of carbon nitride has aroused intense expectations regarding its photocatalysis, but it is impeded by the inevitable defects. Here, we report on a facile melamine-based defect-remedying strategy and resultant carbon nitride high-performance photocatalysts (R-C3N4). Melamine with amino groups and a triazine structure was selected as a “little patch” to passivate and remedy various defects inside carbon nitride. Such a remedying effect has been comprehensively proven by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) analyses, and the ninhydrin test. In addition, their effects on photocatalysis were also individually confirmed by chemical methods, including cyano reduction reactions and deamination reactions. Furthermore, melamine remediation can result in g-C3N4/mpg-C3N4 junctions, which also favors electron transfer and charge s...

Fe-based metal–organic frameworks (MOFs) including MIL-101(Fe), MIL-100(Fe), MIL-53(Fe), and MIL-88B(Fe) prepared via a facile solvothermal process were introduced as both adsorbents and catalysts to generate powerful radicals from persulfate for acid orange 7 (AO7) removal in aqueous solution. Various catalysts were described and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray photoelectron spectra. Because of the high specific surface area of the materials, we studied the adsorption isotherms of the four MILs by the fitting of Langmuir adsorption isotherm. Meanwhile, the catalytic activities in persulfate oxidation system were investigated. The results showed that the sequence of the materials ability in the combination of adsorption and degradation was MIL-101(Fe) > MIL-100(Fe) > MIL-53(Fe) > MIL-88B(Fe), which had a close connection with the activity of metal ion in active site of the catalysts and their different cages in size. Moreover, the reactive species in MILs/persulfate system were identified as sulfate radicals and hydroxyl radicals. The reaction mechanism for persulfate activation over MILs was also studied.

Photooxidation plays an important role in organic synthesis. However, deep oxidation and degradation could reduce the product selectivity and the final yield, which is a crucial issue in the photooxidation reactions. Polymeric carbon nitride (C3N4) shows great potentials in the photocatalysis, but most improved methods make C3N4 show strong oxidation ability, which limits their applications in the selective oxidation synthesis. In order to overcome the limits and enhance the photooxidation efficiency, terephthalic acid was used to change the monomer structure of carbon nitride (P-CN). The physical and electrochemical properties of P-CN were studied with TEM, SEM, XRD, XPS, BET, NMR, ESR and theoretical calculations. The conduction band (CB) position of P-CN is reduced while the valance band (VB) is almost unchanged, which benefits for enhancing visible light response, and preventing the deep oxidation or degradation. At the same time, the structure defects (unreacted amino in the copolymerization process of g-C3N4) are reduced. As a result of these enhanced properties, the photocatalytic efficiency of P-CN in the photooxidation reaction of 1,4-dihydro-2,6-dimethylpyridine-3,5-dicarboxylate (1,4-DHP) is improved 17-fold compared with g-C3N4. More importantly, the pure product could be obtained by simple filtration without any purification, and there is no obvious deep oxidation or degradation.

High-throughput and low-cost methods for the fabrication of 2D patterned structures are highly desirable. Herein we proposed a new colloidal lithography method using 2D microgel colloidal crystal (CC) as template. Unlike the previously developed methods in which the microgel spheres act as lithography mask, herein they act as nanoreactors to convert a precursor into the target product. As an example, highly ordered 2D CC of poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-AA)) microgel was prepared on charge-reversible silicon wafer. The template was first treated with trimethylchlorosilane (TMCS) and then loaded with Fe(NO3)3. Finally the polymer was removed and Fe(NO3)3 was converted in situ to Fe2O3 by calcination, and an ordered Fe2O3 array was obtained. The composition left after calcination was confirmed to be Fe2O3 by XPS. TMCS treatment was demonstrated to be necessary to obtain arrays of discrete patches, instead of continuous film. 0.2 mM Fe(NO3)3 solution was found to be optimal for Fe(NO3)3 loading. A calcination temperature of 600 °C was high enough to remove the polymeric materials and convert Fe(NO3)3 to Fe2O3. The method not only allows constructing ordered structures in a simple and cost-efficient way, but also adjusting the parameters of the pattern by adjusting the parameters of the template.

Combination of three-dimensional (3D) nanoarchitectures and good electrical conductive performance is charming for the application of graphene-based composite. Herein, 3D lamellar composite of vanadium nitride nanowires encapsulated in reduced graphene oxide (VN NWs-rGO), in which interconnected VN NWs as skeletons with a porous structure were encapsulated in N-doped rGO nanosheets to form the lamellar structure, was synthesized by combination of freeze-casting and nitridation techniques. The as-prepared lamellar composite exhibited excellent EM wave absorbing properties: the min reflection loss (RL) value of the VN NWs-rGO/paraffin hybrid with a filler loading of 15 wt% was −41.5 dB at a thickness of 1.5 mm, with an effective absorption bandwidth (EAB, RL

The ongoing expansion of mushroom industries has generated enormous spent mushroom substrate with the potential for production of valuable chemicals. This study aimed to investigate ultrasound‐assisted extraction (UAE) of fungal sterols from spent shiitake (Lentinula edodes) substrate (SSS) by response surface methodology. The results showed that three variables, including ultrasonic power, extraction time, and liquid–solid ratio, had considerable influence on the extraction efficiency of total fungal sterols with liquid–solid ratio being highly significant for the process. The optimal UAE conditions included liquid–solid ratio 22 mL/g, ultrasonic power 432 W, and extraction time 16 min for the maximum recovery of fungal sterols (151.62 mg ergosterol equivalents/100 g dry weight) from SSS. Further GC‐MS analysis indicated that the extracts yielded under the optimal conditions contained ergosterol, ergosta‐7,22‐dienol, and β‐sitosterol, in which ergosterol was the most abundant mycosterol. The extracts also showed a comparable antitumor effect against three cancer cell lines. PRACTICAL APPLICATIONS: Spent mushroom substrate, a major by‐product of mushroom industries, remains a big challenge for the profitability of mushroom industries. Our results indicated that spent shiitake substrate can be valorized by UAE for production of fungal sterols.