Changeable Active Sites by Pr Doping CuSA-TiO2 Photocatalyst for Excellent Hydrogen Production.

Photocatalytic water splitting for clean hydrogen production has been a very attractive research field for decades. However, the insightful understanding of the actual active sites and their impact on catalytic performance is still ambiguous. Herein, a Pr-doped TiO2-supported Cu single atom (SA) photocatalyst is successfully synthesized (noted as Cu/Pr-TiO2). It is found that Pr dopants passivate the formation of oxygen vacancies, promoting the density of photogenerated electrons on the CuSAs, and optimizing the electronic structure and H* adsorption behavior on the CuSA active sites. The photocatalytic hydrogen evolution rate of the obtained Cu/Pr-TiO2 catalyst reaches 32.88 mmol g-1 h-1, 2.3 times higher than the Cu/TiO2. Innovatively, the excellent catalytic activity and performance is attributed to the active sites change from O atoms to CuSAs after Pr doping is found. This work provides new insight for understanding the accurate roles of single atoms in photocatalytic water splitting.

(±)-Hypernumqulins A-H: Eight pairs of unexpected [2+2] cycloaddition sesquiterpenoid alkaloid with 6/6/6/4/10 ring system from Hypericum monogynum L.

(±)-Hypernumqulins A-H (1-8), eight pairs of enantiomeric quinoline alkaloids fused with an isopentenyl and a germacrane-type sesquiterpenoid, featuring an unprecedented skeleton with 6/6/6/4/10 ring system, were isolated from Hypericum monogynum L. under the guidance of molecular networking strategy. Their structures including absolute configuration were elucidated by NMR spectroscopy analysis, X-ray crystallography and quantum chemical calculation. The proposed [2+2] cycloaddition may play a key biogenic step in building the unexpected skeleton. Most of the isolates exhibited cytotoxicity with IC50 values ranging from 2.82 ± 0.03 to 45.25 ± 1.26 µM against MCF-7, A549 or SGC7901 cells. Furthermore, compounds (±)-1 and (-)-1 could induce apoptosis by upregulating the protein expression level of Bax and downregulating of Bcl-2 in MCF-7 cells. These findings provided the first example of germacrane sesquiterpene quinoline alkaloids, and supported the possibilities for the development of new anti-tumor agents.

Porphyrin-based covalent organic framework as oxidase mimic for highly sensitive colorimetric detection of pesticides.

A covalent organic framework-based strategy was designed for label-free colorimetric detection of pesticides. Covalent organic framework-based nanoenzyme with excellent oxidase-like catalytic activity was synthesized. Unlike other artificial enzymes, porphyrin-based covalent organic framework (p-COF) as the oxidase mimic showed highly catalytic chromogenic activity and good affinity toward TMB without the presence of H2O2, which can be used as substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Based on the fact that the pesticide-aptamer complex can inhibit the oxidase activity of p-COF and reduced the absorbance at 650 nm in UV-Vis spectrum, a label-free and facile colorimetric detection of pesticides was designed and fabricated. Under the optimized conditions, the COF-based colorimetric probe for pesticide detection displayed high sensitivity and selectivity. Taking fipronil for example the limit of detection was 2.7 ng/mL and the linear range was 5 -500,000 ng/mL. The strategy was successfully applied to the detection of pesticides with good recovery , which was in accordance with that of HPLC-MS/MS. The COF-based colorimetric detection was free of complicated modification H2O2, which guaranteed the accuracy and reliability of measurements. The COF-based sensing strategy is a potential candidate for the sensitive detection of pesticides of interests.

Rational Modulation of Single Atom Coordination Microenvironments in a BCN Monolayer for Multifunctional Electrocatalysis.

Single-atom (SA) catalysts (SACs) have demonstrated outstanding catalytic performances toward plenty of relevant electrochemical reactions. Nevertheless, controlling the coordination microenvironment of catalytically active SAs to further enhance their catalytic oerformences has remained elusive up to now. Herein, a systematic investigation of 20 transition metal atoms that are coordinated with 20 different microenvironments in a boroncarbon-nitride monolayer (BCN) is conducted using high-throughput density functional theory calculations. The experimentally synthesized ternary BCN monolayer contains carbon, nitrogen, and boron atoms in its 2D network, thus providing a lot of new coordination environments than those of the current Cx Ny nanoplatforms. By exploring the structural/electrochemical stability, catalytic activity, selectivity, and electronic properties of 400 (20 × 20) TM-BCN moieties, it is discovered that specific SA coordination environments can achieve superior stability and selectivity for different electrocatalytic reactions. Moreover, a universal descriptor to accelerate the experimental process toward the synthesis of BCN-SACs is reported. These findings not only provide useful guidance for the synthesis of efficient multifunctional BCN-SACs but also will immediately benefit researchers by levering up their understanding of the mechanistic effects of SA coordination microenvironments on electrocatalytic reactions.

Interface Engineering Induced Electron Redistribution at PtNs /NiTe-Ns Interfaces for Promoting pH-Universal and Chloride-Tolerant Hydrogen Evolution Reaction.

Exploring highly efficient hydrogen evolution reaction (HER) electrocatalysts for large-scale water electrolysis in the full potential of hydrogen (pH) range is highly desirable, but it remains a significant challenge. Herein, a simple pathway is proposed to synthesize a hybrid electrocatalyst by decorating small metallic platinum (Pt) nanosheets on a large nickel telluride nanosheet (termed as PtNs /NiTe-Ns). The as-prepared PtNs /NiTe-Ns catalyst only requires overpotentials of 72, 162, and 65 mV to reach a high current density of 200 mA cm-2 in alkaline, neutral and acidic conditions, respectively. Theoretical calculations reveal that the combination of metallic Pt and NiTe-Ns subtly modulates the electronic redistribution at their interface, improves the charge-transfer kinetics, and enhances the performance of Ni active sites. The synergy between the Pt site and activated Ni site near the interface in PtNs /NiTe-Ns promotes the sluggish water-dissociation kinetics and optimizes the subsequent oxyhydrogen/hydrogen intermediates (OH*/H*) adsorption, accelerating the HER process. Additionally, the superhydrophilicity and superaerophobicity of PtNs /NiTe-Ns facilitate the mass transfer process and ensure the rapid desorption of generated bubbles, significantly enhancing overall alkaline water/saline water/seawater electrolysis catalytic activity and stability.

A promising and highly sensitive electrochemical platform for the detection of fentanyl and alfentanil in human serum.

A novel electrochemical method has been developed, based on a covalent organic framework (COF) and reduced graphene oxide (rGO), to detect fentanyl and alfentanil. COF nanomaterials with chrysanthemum morphology obtained by solvothermal reaction contain rich active sites for electrochemical catalytic reaction, thus improving the detection performance of the designed sensor. Reduced graphene oxide improves the sensor's sensitivity due to enhanced electron transfer. Under optimized experimental conditions, the fabricated electrode presents a linear range of 0.02 to 7.26 µM for alfentanil and 0.1 to 6.54 µM for fentanyl, with detection limits of 6.7 nM and 33 nM, respectively. In addition, the sensor possesses excellent selectivity, outstanding reproducibility, and acceptable stability. The proposed sensor is feasible for the reliable monitoring of fentanyl and alfentanil in human serum samples, with acceptable reliability and high potential in real-world applications. Finally, the electrochemical characteristic fingerprint of fentanyl is investigated by studying the electrochemical behavior of alfentanil and fentanyl on the electrode surface.

Dissipation and Dietary Risk Assessment of Prochloraz in Strawberries under Greenhouse Conditions.

Prochloraz and its metabolites in strawberries have not been determined until now. Meanwhile, few reports in the literature have concerned the dissipation behavior and risk assessment of prochloraz and its metabolites in strawberries under greenhouse conditions in Beijing. A method for the determination of prochloraz and its metabolites in strawberries was developed using QuEChERS in combination with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Prochloraz and its metabolites recovered from strawberries were present in concentrations of 73.06% to 116.01%, their RSDs ranged from 1.12% to 9.17%, and their limits of detection ranged from 0.1 to 1 µg kg-1. Then, a study was conducted on the dissipation of prochloraz in strawberries under greenhouse conditions. The dissipation of prochloraz in strawberries followed the first-order kinetic equation, and its half-life was 8.06 days. The health risk associated with prochloraz in strawberries was evaluated using the target hazard quotient (THQ) method and EFSA PRIMo model. The results showed that the THQ values, %ARfD values, and %ADI values were less than 1. These results indicate that no health concerns of prochloraz are associated with the consumption of the studied strawberries. The government can use the results of this study to support the establishment of a maximum residue level for prochloraz in strawberries.

New Strategy and Excellent Fluorescence Property of Unique Core-Shell Structure Based on Liquid Metals/Metal Halides.

The further applications of liquid metals (LMs) are limited by their common shortcoming of silver-white physical appearance, which deviates from the impose stringent requirements for color and aesthetics. Herein, a concept is proposed for constructing fluorescent core-shell structures based on the components and properties of LMs, and metal halides. The metal halides endow LMs with polychromatic and stable fluorescence characteristics. As a proof-of-concept, LMs-Al obtained by mixing of LMs with aluminum (Al) is reported. The surface of LMs-Al is transformed directly from Al to a multi-phase metal halide of K3 AlCl6 with double perovskites structure, via redox reactions with KCl + HCl solution in a natural environment. The formation of core-shell structure from the K3 AlCl6 and LMs is achieved, and the shell with different phases can emit a cyan light by the superimposition of the polychromatic spectrum. Furthermore, the LMs can be directly converted into a fluorescent shell without affecting their original features. In particular, the luminescence properties of shells can be regulated by the components in LMs. This study provides a new direction for research in spontaneous interfacial modification and fluorescent functionalization of LMs and promises potential applications, such as lighting and displays, anti-counterfeiting measures, sensing, and chameleon robots.

Electro-assisted Molecular Assembly Giving Atomic-Scale Catalytic Active-Site Detection.

The artificially accurate design of nonmetal electrocatalysts' active site has been a huge challenge because no pure active species with the specific structure could be strictly controlled by traditional synthetic methods. Species with a multiconfiguration in the catalyst hinder identification of the active site and the subsequent comprehension of the reaction mechanism. We have developed a novel electro-assisted molecular assembly strategy to obtain a pure pentagon ring on perfect graphene avoiding other reconstructed structures. More importantly, the active atom was confirmed by the subtle passivation process as the topmost carbon atom. Recognition of the carbon-defect electrocatalysis reaction mechanism was first downsized to the single-atom scale from the experimental perspective. It is expected that this innovative electro-assisted molecular assembly strategy could be extensively applied in the active structure-controlled synthesis of nonmetal electrocatalysts and verification of the exact active atom.

Silver nanoparticles embedded 2D g-C3N4nanosheets toward excellent photocatalytic hydrogen evolution under visible light.

Photocatalytic water splitting is considered to be a feasible method to replace traditional energy. However, most of the catalysts have unsatisfactory performance. In this work, we used a hydrothermal process to grow Ag nanoparticlesin situon g-C3N4nanosheets, and then a high performance catalyst (Ag-g-C3N4) under visible light was obtained. The Ag nanoparticles obtained by this process are amorphous and exhibit excellent catalytic activity. At the same time, the local plasmon resonance effect of Ag can effectively enhance the absorption intensity of visible light by the catalyst. The hydrogen production rate promote to 1035µmol g-1h-1after loaded 0.6 wt% of Ag under the visible light, which was 313 times higher than that of pure g-C3N4(3.3µmol g-1h-1). This hydrogen production rate is higher than most previously reported catalysts which loaded with Ag or Pt. The excellent activity of Ag-g-C3N4is benefited from the Ag nanoparticles and special interaction in each other. Through various analysis and characterization methods, it is shown that the synergy between Ag and g-C3N4can effectively promote the separation of carriers and the transfer of electrons. Our work proves that Ag-g-C3N4is a promising catalyst to make full use of solar energy.

Highly sensitive triethylamine gas sensor by Pt-loaded p-n heterojunction Co3O4/WO3.

Triethylamine (TEA) exists widely in production and life and is extremely volatile, which seriously endangers human health. It is required to develop high-performance TEA sensors to protect human health. We fabricated Pt-Co3O4/WO3based on our previous work, and the performance was tested against volatile organic compounds. Compared with the previous work, its operating temperature was greatly reduced from 240 °C to 180 °C. The response value of Pt-Co3O4/WO3was increased from 1101 to 1532 for 10 ppm TEA with good selectivity. These results show a significant step toward practical use of the Pt-Co3O4/WO3sensor.

A luminescent probe based on terbium-based metal-organic frameworks for organophosphorus pesticides detection.

Terbium-based metal-organic frameworks (Tb-MOF) prepared under mild conditions was utilized to construct a fluorescence probe for determination of organophosphorus pesticides (OPs) coupled with acetylcholinesterase (AChE), acetylcholine chloride (Ach), and choline oxidase (CHO). Since OPs have obvious inhibition on the activity of AChE in the Tb-MOF/ACh/CHO/AChE system, the detection of OPs was accomplished by restoring the fluorescence of Tb-MOF resulting from reduced production of H2O2. By taking chlorpyrifos (CPF) as a pesticide model, the method exhibits high sensitivity in the linear range 0.1-4.0 µg·L-1 with the limit of detection (LOD) of 0.04 µg·L-1 under optimum conditions (λex = 280 nm, λem = 544 nm). The Tb-MOF/ACh/CHO/AChE fluorescence system has high selectivity for CPF. The method was successfully applied to the detection of CPF in tap water and strawberry samples (recovery of 87.36-115.60% for tap water and 95.04-103.20% for strawberry). Free from complicated fabrication operation, the Tb-MOF-based system is rapid, simple, and stable, which provides a reference and new way for the design of OPs fluorescent probes in the future.

A Bidirectional Nanomodification Approach for Synthesizing Hierarchically Architected Mixed Oxide Electrodes for Oxygen Evolution.

Several transition-metal oxides and hydroxides based on earth-abundant elements, such as Fe, Ni, and Co, have emerged as a new generation of oxygen evolution reaction (OER) catalysts due to their low cost, favorable activity, and multifunctional behavior. However, the relatively complicated surface structuring methods, high Tafel slope, and low stability hinder their practical applications to replace the conventional Ir- and Ru-based catalysts. Herein, a strategy to construct hierarchically architected mixed oxides on conductive substrates (e.g., ITO and Ni foam) via a nanosheet (NS) deposition and subsequent bidirectional nanomodification approach, with metal salts in an aprotic polar solvent (e.g., acetone) as the primary modifying reactants is reported. This strategy is used to prepare NiO-based NSs with nanopores, nanobranches, or a combination of both, containing up to four transition metal elements. Record-low Tafel slope (22.3 mV·dec-1 , ≈lowest possible by computational predictions) and week-long continuous operation durability are achieved by FeMnNi-O NSs supported on Ni foams. Taken together, properly designed hierarchical mixed oxide electrodes may provide a cost-effective route to generating high, reliable, and stable OER catalytic activities, paving the way for both new electrocatalyst design and practical water-splitting devices.

Ultrasensitive ppb-level trimethylamine gas sensor based on p-n heterojunction of Co3O4/WO3.

Trace poisonous and harmful gases in the air have been harming and affecting people's health for a long time. At present, effective and accurate detection of ppb-level harmful gas is still a bottleneck to be overcome. Herein, we report a ppb-level triethylamine (TEA) gas sensor based on p-n heterojunction of Co3O4/WO3, which is prepared with ZIF-67 as the precursor and provides Co3O4deposited tungsten oxide flower-like structure. Due to the introduction of Co3O4and the 3D flower-like structure of WO3, the Co3O4/WO3-2 gas sensor shows excellent gas sensing performance (1101 for 10 ppm at 240 °C), superb selectivity, good long-term stability and linear response for TEA concentration. Moreover, the experimental results indicate that the Co3O4/WO3-2 gas sensor also possesses a good response to 50 ppb TEA, in fact, the theoretical limit of detection is 0.6 ppb. Co3O4not only improves the efficiency of electron separation/transport, but also accelerates the oxidation rate of TEA. This method of synthesizing p-n heterojunction with ZIF as the precursor provides a new idea and method for the preparation of low detection limit gas sensors.

Serum and urine ANGPTL8 expression levels are associated with hyperlipidemia and proteinuria in primary nephrotic syndrome.

BACKGROUND: This study aimed to investigate the expression characteristics of ANGPTL8 in patients with primary nephrotic syndrome and its possible correlation with hyperlipidemia and proteinuria. METHODS: ANGPTL8 levels were determined using an enzyme-linked immunosorbent assay in 133 subjects with PNS and 60 healthy controls. RESULTS: Compared with healthy controls, subjects with primary nephrotic syndrome had higher levels of serum and urine ANGPTL8 (P < 0.001). In primary nephrotic syndrome patients, serum ANGPTL8 was positively correlated with cholesterol (r = 0.209, P < 0.05) and triglycerides (r = 0.412, P < 0.001), while there was no correlation with 24 hUTP. Urine ANGPTL8 was positively correlated with high-density lipoprotein cholesterol (r = 0.181, P < 0.05) and was significantly negatively correlated with creatinine (r = - 0.323, P < 0.001), eGFR (r = - 0, P < 0.001) and 24 hUTP (r = - 0.268, P = 0.002). Interestingly, the urine ANGPTL8 concentrations in membranous nephropathy and mesangial proliferative glomerulonephritis pathological types were different. CONCLUSIONS: Serum and urine ANGPTL8 levels in primary nephrotic syndrome patients were correlated with blood lipid levels and proteinuria, respectively, suggesting that ANGPTL8 may play a role in the development of primary nephrotic syndrome hyperlipidemia and proteinuria.

Enhanced performance of an acetone gas sensor based on Ag-LaFeO3 molecular imprinted polymers and carbon nanotubes composite.

High performance acetone gas sensors were fabricated with molecular imprinted polymers of Ag-LaFeO3 (ALFOMMIPs) and multi walled carbon nanotubes (CNTs) composite using the microwave assisted sol-gel method. The crystalline structure, functional groups, grain size and surface appearance of the synthesized materials were analyzed via different characterization techniques and the gas responses of the samples were examined. The detailed acetone gas sensing tests and analysis revealed that the CNTs and ALFOMIPs nanocomposite (CNT/ALFOMIP) sample possessed a higher response than that of the ALFOMIPs sample. Where 0.75 wt% CNTs were added into the ALFOMIPs (0.75% CNT/ALFOMIP nanocomposite) sensor, an excellent gas sensing performance was exhibited. The response of this sensor was up to 59 for 5 ppm acetone vapors and the response and recovery times were 58 and 33 s at low working temperature of 86 °C, respectively. In addition, it had the best selectivity only to acetone vapors due to the use of the molecular imprinting technique.

Microwave-assisted synthesis of porous and hollow α-Fe2O3/LaFeO3 nanostructures for acetone gas sensing as well as photocatalytic degradation of methylene blue.

To address the urgent issues of hazardous gas detection and the prevention of environmental pollution, various functional materials for gas sensing and catalytic reduction have been studied. Specifically, the p-type perovskite LaFeO3 has been studied widely because of its promising physicochemical properties. However, there remains several problems to develop a controllable synthesis of LaFeO3-based p-n heterojunctions. In this work, α-Fe2O3 was further compounded with LaFeO3 to form a porous and hollow α-Fe2O3/LaFeO3 heterojunction to improve its gas-sensing performance and photocatalytic efficiency via a microwave-assisted hydrothermal method. While evaluated as sensors of acetone gas, the optimized sample exhibits excellent performance, including a high response (48.3), excellent selectivity, good reversibility, fast response, and recovery ability. Furthermore, it is an efficient catalyst for the degradation of methylene blue. This can be attributed to the enhancement effect of its larger specific surface area, fast diffusion, enhanced surface activities, and p-n heterojunction. Additionally, this work provides a rapid and rational synthesis strategy to produce metal oxides with both enhanced gas-sensing performance and improved photocatalytic properties.

Ultrasensitive xylene gas sensor based on flower-like SnO2/Co3O4 nanorods composites prepared by facile two-step synthesis method.

Xylene is a volatile organic compound which is harmful to the human health and requires precise detection. The detection of xylene by an oxide semiconductor gas sensor is an important research direction. In this work, Co3O4 decorated flower-like SnO2 nanorods (SnO2/Co3O4 NRs) were synthesized by a simple and effective two-step method. The SnO2/Co3O4 NRs show high xylene response (R g/R a = 47.8 for 100 ppm) and selectivity at the operating temperature of 280 °C, and exhibit high stability in continuous testing. The resulting SnO2/Co3O4 NRs nanocomposites show superior sensing performance towards xylene in comparison with pure SnO2 nanorods. The remarkable enhancement in the gas-sensing properties of SnO2/Co3O4 NRs are attributed to larger specific surface area and the formation of p-n heterojunction between Co3O4 and SnO2. These results demonstrate that particular nanostructures and synergistic effect of SnO2 and Co3O4 enable gas sensors to selectively detect xylene.

Magnetically controlled colorimetric aptasensor for chlorpyrifos based on copper-based metal-organic framework nanoparticles with peroxidase mimetic property.

The fabrication of a magnetically controlled colorimetric aptasensor for chlorpyrifos is reported. The aptasensor was fabricated by the attachment of the colorimetric labels onto the magnetic carrier due to the hybridization reaction between the complementary DNA and aptamer. Chlorpyrifos detection was realized by monitoring the color changes of the TMB/H2O2 solution before and after incubation of the aptasensor with chlorpyrifos via exposure to external magnetic force. The color change was monitored at 650 nm by UV-Vis spectrophotometer. Under the optimal conditions, this magnetically controlled Cu-MOF-based aptasensor showed a detection limit of 4.4 ng/mL with a linear range of 0-1250 ng/mL. The colorimetric aptasensor displayed high selectivity for chlorpyrifos toward other interfering pesticides. The aptasensor was successfully applied for the spiked test of chlorpyrifos in fruits and vegetable samples with good recovery, which were in agreement with data obtained by GC-MS analysis. This magnetically controlled Cu-MOF-based sensing strategy not only leads to development of efficient and facile phase separation, but also expands the MOF's target scope from H2O2 or glucose to pesticides. Graphical abstract.

Fluorescent aptasensing of chlorpyrifos based on the assembly of cationic conjugated polymer-aggregated gold nanoparticles and luminescent metal-organic frameworks.

This study reports on a fluorescent aptasensor of chlorpyrifos (CPF) based on terbium(iii) based on metal-organic frameworks (Tb-MOFs) and PDDA-aggregated-gold nanoparticles (AuNPs). The dispersed AuNPs quench the emissions of the Tb-MOF, while the PDDA-aggregated AuNPs have little effect. The aptamer interacts with PDDA via electrostatic interaction to prevent the aggregation of the AuNPs, which protects the AuNPs from PDDA-induced aggregation and the fluorescence of the Tb-MOF is quenched by FRET between the Tb-MOF and the dispersed AuNPs. Upon the addition of CPF, aptamers are exhausted to form a CPF-aptamer complex, and the following PDDA causes the aggregation of AuNPs, accompanied by weak quenching of the fluorescence of the Tb-MOF. This unlabelled strategy sensitively detects CPF at a concentration of 3.8 nM with a linear range of 5-600 nM. The assay is selective for CPF over other interfering compounds. The method was successfully applied to the determination of CPF in (spiked) tap water and vegetables and fruits samples, indicating its potential applications in enlarging the target scope of luminescent-MOF-based detection for environmental and agricultural samples.