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•A novel layer-by-layer in situ culture (LBLC) method was developed.•Bacterial cellulose/graphene/polyaniline nanocomposites were made by LBLC and polymerization.•The as-prepared ...nanocomposites are mechanically strong and highly flexible.•The as-prepared nanocomposites show excellent gravimetric capacitance and cycling stability.
Rational structure, mechanical robustness, high conductivity, and favorable flexibility are important requirements for superior electrodes, which should not only possess high capacitance but also have freestanding structure without collector to improve the overall performance of supercapacitors. Herein, we demonstrate the fabrication of three-dimensional (3D) porous graphene-containing nanocomposites with highly dispersed graphene (GE) nanosheets in a 3D matrix of bacterial cellulose (BC) by a novel layer-by-layer in situ culture (LBLC) method. The BC/GE nanocomposites are then deposited with polyaniline (PANI), leading to the formation of BC/GE/PANI nanocomposites. Mechanical tests demonstrate excellent robustness and flexibility of the as-prepared BC/GE/PANI nanocomposites, which are used as electrodes directly without any nickel foam or stainless steel wire. The BC/GE/PANI electrode with an optimal GE content has a specific capacitance of 645 F g−1 at a current density of 1 A g−1, which is 2.5 times higher than that of BC/PANI and superior to most previously reported PANI-based electrodes. In addition, the symmetric supercapacitor assembled with BC/GE/PANI demonstrates a high energy density of 14.2 Wh kg−1 at a power density of 200 W kg−1. The excellent electrochemical performance of this BC/GE/PANI electrode is due to its unique 3D porous structure with the uniform distribution of GE nanosheets in the BC matrix and even PANI on BC nanofibers and GE nanosheets, which makes it very promising for diverse flexible energy storage devices. The methodology presented in this work can be extended to the preparation of other BC-based nanocomposite electrodes.
Magnetic carbon nitride composites were synthesized via a solvothermal reaction and developed as an effective adsorbent for magnetic solid-phase extraction of trace hydroxylated polycyclic aromatic ...hydrocarbons (OH-PAHs) from urine samples prior to their determination by HPLC. The sorbent was characterized by Fourier transform infrared spectrometry, X-ray diffractometry, scanning electron microscopy, vibrating sample magnetometry and solvent stability experiments. The adsorption of hydroxy-PAHs is better by a factor or 20 to 49 compared to bare Fe
3
O
4
and comparable that of a commercial C
18
sorbent. The adsorbent amount, adsorption time and eluting solvent and volume were optimized. The complete extraction for the OH-PAHs at a level of 40 ng·mL
−1
and by using 4 mg sorbent is completed within 3 min. With an enzymatic hydrolyzed urine sample loading volume of 2 mL, enhancement factors in the range of 9–10, and a limit of detection (at
S
/
N
= 3) of 0.08 ng·mL
−1
were achieved. The method showed a linear response in the 0.25–250 ng·mL
−1
hydroxy-PAH concentration range, and intra-day and inter-day precisions are 1.5–7.7% and 2.2–8.7%, respectively. The recovery from spiked urine samples ranged from 90.1% to 102%. The sorbent was stable over 10 successive cycles of extraction/desorption of urine sample without significant loss of extraction efficiency. The method was successfully applied for the determination of OH-PAHs in urine samples of smoking volunteers.
Graphical abstract
Schematic presentation of the preparation of graphitic carbon nitride (g-C
3
N
4
)/magnetite (Fe
3
O
4
) using a solvothermal reaction, and application for magnetic solid-phase extraction of three trace hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) in urine samples of smoking volunteers.
Nano-hydroxyapatite samples with different morphologies were successfully prepared by chemical precipitation method using polyethylene glycol (PEG) as a template. The phase composition, ...micro-morphology and surface functional groups of the nano-hydroxyapatite samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM), respectively. The results reveal that the mirco-morphology of hydroxyapatite can be effectively controlled by adjusting pH values in the preparation. Moreover, the growth mechanism of HAp with different morphologies was also discussed.
•HAp with different morphology was obtained by chemical precipitation method.•HAp morphology can be simply controlled by changing pH value.•PEG inhibited the c-column growth of HAp and thus formed laminated morphology.•Solution environment influenced reaction mode and then changed HAp growth pattern.
In this work, graphitic carbon nitride (g-C3N4) supporting finely dispersed Au nanoparticles is developed as a simple and efficient photocatalyst for H2O2 production under visible light irradiation. ...Au nanoparticle cocatalyst remarkably enhances photocatalytic activity of C3N4 for H2O2 production. Due to the inert nature to catalyze the decomposition of H2O2, Au/C3N4 also exhibits stable H2O2 evolution rate. It is of great interest that the maximal H2O2 production activity is reached at the loading amount of Au as low as 0.01%, revealing the great catalytic efficacy of highly dispersed Au cocatalyst during the photocatalytic H2O2 synthesis and the possibility to produce concentrated H2O2 using C3N4 with extremely low Au loading amount. The in situ electron spin resonance studies reveal that the H2O2 is produced through direct 2e− oxygen reduction over Au/C3N4 photocatalyst.
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•Au/C3N4 is a highly active photocatalyst for H2O2 production under visible light.•The optimum loading amount of finely dispersed Au cocatalyst is as low as 0.01%.•H2O2 is formed over Au/C3N4 through direct 2-electron oxygen reduction.•Au/C3N4 is almost inactive for photocatalytic H2O2 decomposition.
In this study, Au-nanoparticle-supported crystalline ZnO (Au/ZnO) is found to be a simple and efficient photocatalyst for direct H2O2 synthesis in an aerated aqueous solution. Compared with widely ...studied Au-nanoparticle-supported anatase TiO2 photocatalyst, Au/ZnO shows almost one order of magnitude higher activity in H2O2 production. The site-specific deposition of smaller Au nanococatalyst on ZnO delivers best photocatalytic performance and the H2O2 production is relatively stable with a rate more than 1.5 mmol L−1 h−1. The electron spin resonance studies reveal that the H2O2 is produced through direct 2e− oxygen reduction over the optimized Au/ZnO photocatalyst.
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•Au/ZnO is much more active than Au/TiO2 for photocatalytic H2O2 production.•Au/ZnO is less active than Au/TiO2 for photocatalytic H2O2 decomposition.•H2O2 is favorably formed over Au/ZnO through direct 2-electron oxygen reduction.•H2O2 formation is influenced by the particle size and deposition site of Au on ZnO.
In this work, doxorubicin (DOX) was intercalated into layered nanohydroxyapatite (LHAp). The drug loaded LHAp (DOX@LHAp) was then mixed with poly(lactic-co-glycolic acid) (PLGA) and electrospun to ...yield DOX@LHAp/PLGA composite scaffolds. As control, needle-like nanohydroxyapatite (nHAp) was also used to make an DOX@nHAp/PLGA composite scaffold and bare DOX was used to fabricate DOX/PLGA scaffold. The morphology, release behavior of DOX, and capability to inhibit cancer cells were assessed. The addition of DOX-loaded nHAp to PLGA causes a slight decrease in the average fiber diameter of DOX@LHAp/PLGA as compared to PLGA. The in vitro drug release tests reveal a much faster release of DOX from DOX/PLGA than DOX@LHAp/PLGA. Moreover, DOX@LHAp/PLGA displays a more sustainable release over DOX@nHAp/PLGA due to the storage of DOX in the gallery of LHAp, which is further proved by their cancer cell inhibition results. We believe that the DOX@LHAp/PLGA scaffold has potential as an implantable drug delivery system.
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•Doxorubicin (DOX) was intercalated into layered nanohydroxyapatite (LHAp).•The DOX@LHAp was mixed with PLGA and electrospun into DOX@LHAp/PLGA scaffold.•The DOX@LHAp/PLGA scaffold displayed much more sustainable release over DOX@PLGA.
In this work, Au-modified F-TiO2 is developed as a simple and efficient photocatalyst for H2O2 production under ultraviolet light. The Au/F-TiO2 photocatalyst avoids the necessity of adding fluoride ...into the reaction medium for enhancing H2O2 synthesis, as in a pure TiO2 reaction system. The F− modification inhibits the H2O2 decomposition through the formation of the ≡Ti–F complex. Au is an active cocatalyst for photocatalytic H2O2 production. We compared the activity of TiO2 with F− modification and without F− modification in the presence of Au, and found that the H2O2 production rate over Au/F-TiO2 reaches four times that of Au/TiO2. In situ electron spin resonance studies have shown that H2O2 is produced by stepwise single-electron oxygen reduction on the Au/F-TiO2 photocatalyst.
In this work, an Au modified Bi2O3-TiO2 (Au/Bi2O3-TiO2) hybrid is developed as a simple and effective photocatalyst for the production of H2O2. The modification of Bi2O3 improves the charge ...separation of photocatalyst and significantly enhances the photocatalytic activity of Au/TiO2 for H2O2 production. In-situ electron spin resonance studies shows stepwise single-electron oxygen reduction reaction (ORR) on the Au/Bi2O3-TiO2 photocatalyst for the production of H2O2. This work demonstrates the importance of heterojunction structure photocatalyst for improved performance of TiO2 in order to produce concentrated H2O2.
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•Au/Bi2O3-TiO2 hybrid is designed as an active photocatalyst for H2O2 production.•The Bi2O3-TiO2 heterojunction promotes charge separation of photoexcited charge carriers.•H2O2 is formed by stepwise single-electron oxygen reduction on Au/Bi2O3-TiO2 photocatalyst.
Compared to the Haber–Bosch (H–B) process for ammonia synthesis with massive emission of greenhouse CO2 and necessary harsh reaction conditions, the electrocatalytic NO3− reduction (NO3RR) for ...ammonia synthesis under ambient temperature and pressure driven by renewable electricity has attracted great attention. NO3RR is also a promising route to construct nitrogen cycles utilizing NOx produced from industrial and agricultural operations. Cu‐based catalyst is one of the most promising platforms for this reaction. This perspective shows the latest understanding and research advances on the NO3RR by Cu‐based electrocatalysts. Through a deep analysis on the rate‐limiting step of NO3RR, the strategies of overcoming the deactivation and enhancing the performance of Cu‐based catalysts are discussed. The great significance of synergistic NOx and H activation in promoting the key kinetic step of electrocatalytic NO3RR by single‐atom, oxide, bimetallic of Cu on the catalytic reaction site construction with tunable adsorption of N‐containing intermediate and active H is stressed. Also, future challenges and perspectives toward coupling reaction of nitrate reduction catalyzed by Cu‐based catalysts are proposed. This perspective can move forward the future research on electrocatalytic NO3RR to ammonia synthesis over advanced Cu‐based electrocatalysts.
A perspective for overcoming deactivation on the catalytic reaction site construction with tunable adsorption of N‐containing intermediate and active H is offered to move forward the future research on electrocatalytic NO3RR to ammonia synthesis over advanced Cu‐based electrocatalysts.
A series of carbon nitride (CN) materials represented by graphitic carbon nitride (g‐C3N4) have been widely used in bioimaging, biosensing, and other fields in recent years due to their nontoxicity, ...low cost, and high luminescent quantum efficiency. What is more attractive is that the luminescent properties such as wavelength and intensity can be regulated by controlling the structure at the molecular level. Hence, it is time to summarize the related research on CN structural evolution and make a prospect on future developments. In this review, we first summarize the research history and multiple structural evolution of CN. Then, the progress of improving the luminescence performance of CN through structural evolution was discussed. Significantly, the relationship between CN structure evolution and energy conversion in the forms of photoluminescence, chemiluminescence, and electrochemiluminescence was reviewed. Finally, key challenges and opportunities such as nanoscale dispersion strategy, luminous efficiency improving methods, standardization evaluation, and macroscopic preparation of CN are highlighted.
Schematic diagram for the structural evolution of carbon nitride and its luminescent energy conversion
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