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The large-scale application of nanozymes remains a significant challenge owing to their unsatisfactory catalytic performances. Featuring a unique electronic structure and coordination environment, single-atom nanozymes provide great opportunities to vividly mimic the specific metal catalytic center of natural enzymes and achieve superior enzyme-like activity. In this study, the spin state engineering of Fe single-atom nanozymes (FeNC) is employed to enhance their peroxidase-like activity. Pd nanoclusters (Pd

Graphite carbon nitride (g-C3N4) is a significant non-metal photocatalyst, but still challenging for photocatalytic degradation of pollutants because of its poor visible light utilization, easy recombination of photo-generated carriers and low surface reactive reaction sites. In this paper, perylene diimide (PDI), an electron-deficient building block for constructing n-type organic semiconductors, was introduced into the framework of g-C3N4 (PDI-g-C3N4) to build polymer with donor–acceptor structure for energy band amelioration, achieving the most expanded visible light response up to date. Besides, a large dihedral angle (90°) induced by PDI moiety in PDI-g-C3N4 changes the molecular aggregation behavior according to calculations, which is advantageous to increase surface area for the reactive site exposure. The most promising functional photocatalyst PDI-g-C3N4/MIL is constructed by in-situ generation of NH2-MIL-53(Fe) on the surface of PDI-g-C3N4 to further facilitate the separation and transfer of interfacial photo-induced carriers. Through a finely adjusting ratio of PDI-g-C3N4 in heterojunction, the target material of PDI-g-C3N4/MIL exhibits superior activity for the photodegradation of organic pollutants in the presence of H2O2 and visible light illumination, providing potential direction in practical application for wastewater treatment.

Rational design and construction of electrochemical sensing platforms with high sensitivity and selectivity is one of the challenges in practical application. Although single-atom catalysts (SACs) have attracted extensive attention, atomically dispersed metal catalysts (ADCs) with multi-atom sites can further compensate for the deficiencies of SACs, which have gradually been a research hotspot in recent years. Herein, atomically dispersed Ru

With the goal of improving the removal of anionic contaminants, copper oxide (CuO)-modified biochar (BC) nanocomposites were successfully prepared through simply ball milling CuO particles with BC. The physicochemical properties of the fabricated CuO/BC nanocomposites were systematically characterized by a series of techniques; their adsorption performances were assessed, and the main adsorption mechanism was revealed. X-ray powder diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses of the nanocomposites showed the strong interaction between CuO and BC and confirmed the success of the ball-milling syntheses. Because of strong electrostatic attraction between the embedded CuO nanoparticles and reactive red (RR120), the composited adsorbents exhibited excellent RR120 removal. The 10%-CuO/BC nanocomposite achieved the best RR120 removal efficiency (46%), which is much higher than that of pristine BC (20%). In addition, the adsorption was insensitive to the change of solution initial pH (4-10). The 10%-CuO/BC also showed fast adsorption kinetics (equilibrium time < 3 h) and extremely high adsorption capacity (Langmuir maximum capacity of 1399 mg g-1) to RR120 in aqueous solutions. Findings from this study demonstrate not only the strong feasibility of ball-milling synthesis of BC-based nanocomposites but also the promising potential of the CuO/BC nanocomposites to remove aqueous anionic contaminants.

Ceria (CeO2) with abundant oxygen defects, surface alkalinity, low cost effectiveness and admirable redox ability could be used in the photoreduction of CO2. However, little attention has been paid to the interaction of reactant CO2 molecules on CeO2–based photocatalysts. In this work, Cu2O nanoparticles were applied to the modification of the properties of Lewis acid/base, surface oxygen defect content and visible light adsorption of CeO2, and the adsorption/activation abilities of CO2 reactant on Cu2O/CeO2 and CeO2 photocatalysts were investigated in comparison. The photocatalytic performance showed that Cu2O/CeO2 had better activity than CeO2. And the loading of Cu2O resulted in more oxygen defects and Ce3+ species, which was helpful for available visible light adsorption and higher charge-separation efficiency. Furthermore, CO2-TPD, CO2-adsorption DRIFTS and in-situ ESR results demonstrated that the synergistic effects of Cu2O/CeO2 were beneficial for more generated carboxylate and CO2− radicals, instead of carbonate species which promoted CO2 reduction to CO.

As the secondary metabolites of cyanobacterial harmful algal blooms (Cyano-HABs), microcystins (MCs) were generated under various environmental and cellular conditions. The understanding of the causes of MCs generation is of great interest in the field of water treatment and environmental science. In this work, we studied how Microcystis aeruginosa (FACHB-905) cell densities affect the MCs synthetase genes (mcy) expression, microcystin-LR (MC-LR) and quorum sensing molecules (Acyl-homoserine lactones (AHLs)) production. An electrochemical sensor was developed here for sensitive and quantitative detection of MC-LR that cultured at different cell densities. The results showed that mcy expression and MC-LR concentration started to increase when the cell density reached ca. 22 × 106 cells/mL, and was significantly increased with increasing cell densities. Moreover, the up-regulation of AHLs with increasing cell densities revealed that MC-LR is quorum sensing-mediated. Our results undoubtedly confirmed that MC-LR was produced in a cell density-dependent way that mimics quorum sensing, and the minimum cell density (ca. 22 × 106 cells/mL) that was required to produce MC-LR was provided and offered a reference standard for the prevention and control of MCs pollution in the actual water environment.

Highlights Secondary-atom-doped strategy was proposed to synthesize single-atom electrocatalyst.The increase in both the density of active sites and their intrinsic activity was achieved simultaneously.The resultant single-atom catalyst shows outstanding ORR activity in acidic media. Electronic supplementary material The online version of this article (10.1007/s40820-020-00502-5) contains supplementary material, which is available to authorized users., Single-atom catalysts (SACs) with nitrogen-coordinated nonprecious metal sites have exhibited inimitable advantages in electrocatalysis. However, a large room for improving their activity and durability remains. Herein, we construct atomically dispersed Fe sites in N-doped carbon supports by secondary-atom-doped strategy. Upon the secondary doping, the density and coordination environment of active sites can be efficiently tuned, enabling the simultaneous improvement in the number and reactivity of the active site. Besides, structure optimizations in terms of the enlarged surface area and improved hydrophilicity can be achieved simultaneously. Due to the beneficial microstructure and abundant highly active FeN5 moieties resulting from the secondary doping, the resultant catalyst exhibits an admirable half-wave potential of 0.81 V versus 0.83 V for Pt/C and much better stability than Pt/C in acidic media. This work would offer a general strategy for the design and preparation of highly active SACs for electrochemical energy devices. Electronic supplementary material The online version of this article (10.1007/s40820-020-00502-5) contains supplementary material, which is available to authorized users.

A novel CeO2/TiO2-MoO3 (Ce/TM) catalyst was synthesized by using of Mo as a bulk dopant to boost the NH3-SCR performance of CeO2/TiO2 catalyst. It displayed 100% NO conversion at 200–350 °C under 60,000 mlg−1 h−1 and high tolerance to H2O and SO2 at 250 °C. Characterization results manifested that the doping of Mo not only resulted in more Bronsted acid and Lewis acid sites formed on the Ce/TM surface, but also increased the specific surface area and redox ability of the catalyst, all of which account for the enhanced NH3-SCR activity.

For photocatalytic CO2 reduction, directional charge-transfer channel and abundant active sites are of significance. Herein, we designed and fabricated phosphate modified octahedral CeO2 {111} surface coupling with g-C3N4 (P-CeO2/g-C3N4) for photocatalytic CO2 reduction, which had superior activity than others, i.e., P-CeO2, g-C3N4, CeO2/g-C3N4. The characterization results revealed the coordination environment of P species, as well as, the presence of hydrogen bond between phosphate and amino. Through the PO43− bridge, the interfacial electrons donated from g-C3N4 to CeO2, leading to the Z-scheme formation and fast photo-generated charge transfer. Furthermore, PO43− modification increased more oxygen-containing functional groups on surface, which acted as Lewis basic sites for CO2 reactant adsorption and activation. Therefore, under the synergistic interaction of charge-transfer channel and abundant active sites, P-CeO2/g-C3N4 is a potential photocatalyst for CO2 reduction.

The effects of carbon quantum dots (CQDs) on the dynamic properties of bovine serum albumin (BSA) were investigated using pendant drop profile analysis method. Moreover, the effects of CQDs on the competitive adsorption of BSA and dipalmitoyl phosphatidylcholine (DPPC) were examined. CQDs reduce the fluorescence intensity of BSA and cause a red shift in fluorescence emission. The quenching constant at pH 4.3 is almost twice as large as that of the value obtained at pH 6.0. A small amount of CQDs does not influence the dynamic surface adsorption properties of BSA molecules. As the CQD concentration increases, a gradual increase in adsorption rate of BSA molecules is observed. Moreover, the addition of CQDs results in a significant transition of kinetic dependencies of surface elasticity of BSA solution when the CQD concentration exceeds a critical value. The appearance of the maximum surface elasticity value is probably attributed to the formation of tails and loops. When the dynamic surface properties are dominated by BSA molecules, the effects of CQDs on the surface properties of BSA/DPPC mixture are similar to those of BSA alone. However, when the surface film mainly consists of DPPC, CQDs can obviously change the interfacial properties of DPPC monolayer.

As a green solvent-free process, ball milling has attracted considerable attention in fabricating nanocomposites. Herein, we synthesized novel Z-scheme heterojunction CeO2/g-C3N4 nanocomposites by simply direct ball milling CeO2 and g-C3N4 at three different mass ratios (3:7, 7:3, and 9:1). In comparison to individual CeO2 and g-C3N4, the ball-milled nanocomposites showed stronger UV light response, higher charge carrier separation efficiency, greater photodegradation potential, higher photocurrent intensity, and faster electron transfer, indicating much better photocatalytic activity. When used as photocatalysts to remove methylene blue (MB) under UV light irradiation, 70% CeO2/g-C3N4 exhibited the highest removal rate (90.1%), much better than that of CeO2 (6.2%) or g-C3N4 (45.7%). The synergistic interact between adsorption and photodegradation of the CeO2/g-C3N4 nanocomposites was simulated by kinetic models, and a strong positive correlation (r = 0.834 and rs = 0.777) between adsorption and photocatalysis was identified. The results indicate that adsorption can promote photodegradation by accelerating the kinetics, while photodegradation can regenerate adsorption sites. This work provides not only a facile synthesis of Z-scheme heterojunction photocatalysts but also a novel perspective for better understanding the synergy between adsorption and photocatalysis.

In this study, a novel HKUST-1-based nanocomposite was fabricated through a facile in-situ solvothermal method using amino-tethered SBA-15 (APTMS-SBA-15) as the matrix. Several characterizations had been applied to study the physicochemical properties of the hybrid material. The APTMS-SBA-15, acting as a structure-directing agent, could not only induce the nucleation of HKUST-1 directionally through the coordination effect between Cu2+ centers and amino groups, but also regulate the growth of the nanocrystals via the confinement effect of mesoporous structure. The HKUST-1 grains transformed from octahedron (10–15 μm) to hierarchical flower-like architecture assembled by lamellar crystals (100–200 nm in thickness). The smaller crystal sizes along with the extra ordered mesopores were conducive to reducing the intragranular mass transfer resistance and shortening the diffusion path of CO2 transport. Compared with pristine HKUST-1, the specific surface area, micropore volume and the amount of exposed metal sites increased simultaneously. Meanwhile, the retained amino could also contribute to polarized surfaces of the framework, thus enhancing the interaction towards CO2 molecules. The adsorption sites originating from HKUST-1 synergized with APTMS-SBA-15 to promote the effective capture of CO2. At 25 °C and 1.0 bar, the CO2 adsorption capacity and CO2/N2 (15%/85%) selectivity of the composite reached 4.93 mmol/g and 18.3, which were increased by 18.5% and 92.6% respectively than those of pure HKUST-1. These findings provided a promising strategy for oriented design and synthesis of MOF-based composites with high efficiency for various gas separation processes.

Developing efficient nonprecious metal electrocatalysts is urgently needed to promote the sluggish kinetics of oxygen evolution reaction (OER). Transition metals-based layered double hydroxides (LDH) have been considered as highly active OER catalysts, while low conductivity and limited active site exposures hinder their further applications. Herein, CoNi LDH/Ti3C2Tx MXene is facilely constructed by using Ti3C2Tx coated nickel foam as support to load CoNi LDH through electrodeposition. Surprisingly, a significant enhancement in OER activity of pristine CoNi LDH is achieved due to the metallic conductivity and hydrophilic and electronegative surface of Ti3C2Tx. Importantly, CoNi LDH/Ti3C2Tx displays prominent OER performance and stability in alkaline medium, which exhibits a low overpotential of 257.4 mV to reach current density of 100 mA/cm2 and a small Tafel slope of 68 mV/dec. The experimental and calculated results demonstrate electron transfer from CoNi LDH to Ti3C2Tx plays a significant role in boosting OER activity by lowering the binding strength of intermediates.

Interface engineering of electrocatalysts is a promising strategy to modulate their corresponding physicochemical properties. Compared with sulfides and selenides, the studies related to the interface engineering of the transition metal tellurides for oxygen evolution reaction (OER) remain scarce, regardless of their higher electrical conductivity and mass transport rate. Herein, a class of NiFe LDH/NiTe composites was successfully synthesized for enhancing the OER performance by partial chemical etching of nickel foam to prepare NiTe nanoarrays, and subsequently depositing NiFe LDH with a hydrothermal process. Based on experimental and calculated results, the NiFe LDH/NiTe composite is observed with a more intensive interface rather than a simple physical mixture, leading to enhanced charge transfer and improved reaction kinetics resulting from reduced binding strength of intermediates. Therefore, the resultant NiFe LDH/NiTe exhibits outstanding OER activity in alkaline solution with an overpotential of 228 mV at the current density of 50 mA/cm2.

In this paper, two cooperative guidance laws based on the encircled area around a target by multi-attacker are designed to deal with the problem of cooperative encirclement and simultaneous attack under condition of both known target acceleration and unknown target acceleration, which guarantees that the attackers hit the target from every prescribed angle and achieve the best effect. The acceleration components along the attacker-target line of sight in novel guidance laws can reduce the relative remaining distance between each of the attackers and the target at the same speed, thus completing simultaneous attack and avoiding the calculation of the remaining time. The components of the guidance laws perpendicular to the attacker-target line of sight can make the normal overload of relative motion zero, so that the trajectory will be smooth and the collision problem within the attacker can be avoided. Simulation results verified the practicability of the novel guidance laws.

The synergy between adsorption and photocatalysis has been well recognized in contaminant photodegradation; however, the governing mechanism is still not clear. The main objective of this work is to understand the kinetic processes of synergic adsorption-photocatalysis of graphitic carbon nitrate (g-C3N4), a visible light responsive photocatalyst with a planar graphitic-like structure, in organic contaminant removal. An anionic dye Reactive Red 120 (RR120), which has six sulphonate groups and a complex aromatic molecular structure, was selected as a model contaminant compound. A range of experiments were conducted to determine the kinetics of adsorption, photodegradation, and the integrated process. Various kinetic models were used to simulate and interpret the experimental data and thus to unveil the governing mechanisms. The integrated adsorption and photodegradation of the dye by g-C3N4 was mainly controlled by: 1) adsorption of dye onto g-C3N4 surface, 2) photodegradation of dye in bulk solution, and 3) photodegradation of adsorbed dye on g-C3N4 surface. Both experimental and modeling results showed that the adsorption kinetic rate (3.37 min−1) was faster than the photodegradation kinetic rates. In addition, the surface photodegradation kinetic rate of adsorbed dye (0.149 min−1) was faster than that in solution (0.005 min−1). Adsorption process thus can promote the photodegradation of contaminants by g-C3N4. On the other hand, photodegradation of dye-laden g-C3N4 regenerated its adsorption capacity for multiple times, suggesting photocatalysis process can also promote the adsorption of contaminates on g-C3N4.

The effects of cationic surfactants on the properties of Pickering emulsions stabilized by silica nanoparticles (nano-SiO2) were investigated. The zeta potential, three-phase contact angle (θ), and dynamic interfacial tension (DIT) were measured to analyze the interaction between hydrophilic nano-SiO2 and four different cationic surfactants (i.e., dodecyltrimethylammonium bromide [DTAB], bis-quaternary ammonium salts [BQAS-12], multiple quaternary ammonium salts [MQAS-12], and dimethyldioctadecylammonium bromide [DDAB-18]). All these surfactants can naturally improve the stability of Pickering emulsions induced by hydrophilic nano-SiO2. The nano-SiO2/MQAS-12 mixtures exhibited the best ability to stabilize the O/W emulsions, followed by nano-SiO2/BQAS-12 mixtures. The nano-SiO2/DDAB-18 mixtures can induce emulsion inversion from O/W to W/O. All emulsions exhibited excellent salt tolerance and acid-base resistance properties. Determining the zeta potential showed that nano-SiO2 had the highest negative charge at the pH of 9.5. Thus, the surfactant molecules can be adsorbed remarkably on the nano-SiO2 surface. Modification with different cationic surfactants can significantly increase the θ value of nano-SiO2, but the bilayers for DTAB-12, BQAS-12, and MQAS-12, except for DDAB-18, were adsorbed. DIT curves indicated that competitive adsorption of the surfactants occurred between the oil/water interface and nano-SiO2 surface. The competitive adsorption of MQAS-12 was stronger than those of BQAS-12 and DTAB-12. The nano-SiO2/DDAB-18 mixture had an apparent induction region and required a considerable amount of time to reach equilibrium. The modified nano-SiO2 was also not adsorbed in the oil/water interface spontaneously, which may be due to the large size of particles compared with small surfactant molecules.

The spontaneous recovery of function after injury in the adult central nervous system is limited due to the several proteins, such as Nogo-A that have repulsive or inhibitory effects on growing neuritis. The Chinese herbal medicine extraction Panax notoginseng saponins (PNS) injection has been widely used and effective in repairing the function of impaired nerves, but the mechanism of this herbal medicine is still poorly understood. This project evaluated the effect of Panax notoginseng saponins on neurological functional recovery and on the expression of Nogo-A, NgR and p75 at 7, 14 and 28 d after middle cerebral artery occlusion (MCAO) in rats and also oxygen-glucose deprivation/reperfusion (OGD/R) model on SH-SY5Y cells. We found that the expression of Nogo-A, NgR and p75 of rats receiving MCAO surgery increased on the 7th day, reached a peak on the 14th or 28th day and maintained high levels and Panax notoginseng saponins significantly decreased these expressions. This may be the mechanism of Panax notoginseng saponins that contributes to the recovery of nerve function, which plays an important role in brain protection after cerebral infarction.

The spontaneous recovery of function after injury in the adult central nervous system is limited due to the several proteins, such as Nogo-A that have repulsive or inhibitory effects on growing neuritis. The Chinese herbal medicine extraction Panax notoginseng saponins (PNS) injection has been widely used and effective in repairing the function of impaired nerves, but the mechanism of this herbal medicine is still poorly understood. This project evaluated the effect of Panax notoginseng saponins on neurological functional recovery and on the expression of Nogo-A, NgR and p75 at 7, 14 and 28 d after middle cerebral artery occlusion (MCAO) in rats and also oxygen-glucose deprivation/reperfusion (OGD/R) model on SH-SY5Y cells. We found that the expression of Nogo-A, NgR and p75 of rats receiving MCAO surgery increased on the 7th day, reached a peak on the 14th or 28th day and maintained high levels and Panax notoginseng saponins significantly decreased these expressions. This may be the mechanism of Panax notoginseng saponins that contributes to the recovery of nerve function, which plays an important role in brain protection after cerebral infarction.