Base-Mediated Tandem [3 + 2] Cycloaddition/Ring Openning Reaction of Arylhydrazonoyl Chlorides with Arylnitroso Compounds for Synthesis of Substituted Diazene Oxides.

A base-mediated tandem [3 + 2] cycloaddition/ring opening reaction of nitrilimines generated from arylhydrazonoyl chlorides with arylnitroso compounds has been developed. This protocol provides a novel and rapid approach for the synthesis of substituted azoxy compounds under mild conditions with moderate to good yields and a broad substrate scope.

Coupling ZnIn2S4 Nanosheets with MoS2 Hollow Nanospheres as Visible-Light-Active Bifunctional Photocatalysts for Enhancing H2 Evolution and RhB Degradation.

In this study, Mo-glycerate was used as a precursor to create MoS2 hollow nanospheres (HNS), which were then used for the first time to modify ZnIn2S4 nanosheets to create MoS2 HNS/ZnIn2S4 photocatalysts. The findings demonstrate that MoS2 HNS/ZnIn2S4 heterojunctions exhibited remarkably boosted photocatalytic properties and excellent reusability for both RhB degradation and H2 evolution without the use of Pt as a co-catalyst. Among the heterojunctions, the RhB degradation and H2 evolution efficiencies of the optimized MoS2 HNS/ZnIn2S4-3 wt % composite were almost 5 and 34 times higher than those of ZnIn2S4, respectively. The excellent performance of MoS2 HNS/ZnIn2S4-3 wt % might be attributed to the expansion of the visible-light response range and the accelerated separation efficiency of photo-induced carriers, according to the findings of the optical property tests. Based on the established band gap position and characterization results, a potential mechanism for appealing photocatalytic activity over MoS2 HNS/ZnIn2S4 heterojunctions was also postulated.

Are paediatric clinical practice guidelines trustworthy?

AIM: To assess the methodological and reporting quality of paediatric clinical practice guidelines (CPGs) in National Guideline Clearinghouse (NGC) using the Appraisal of Guidelines for Research and Evaluation (AGREE) II instrument and Reporting Items for Practice Guidelines in Healthcare (RIGHT) standard. METHODS: We identified all published CPGs through the NGC, and search records were screened in duplicate for inclusion. Two researchers evaluated the methodological and reporting quality of paediatric CPGs using the AGREE II instrument and RIGHT standard. STATA version 12.0 and SPSS version 22.0 software were used to analyse the related data. RESULTS: A total of 50 paediatric CPGs were included. The scores for all six domains by AGREE II instrument were presented as follows: scope and purpose (85.6 ± 9.59), stakeholder involvement (69.15 ± 19.32), rigour of development (73.19 ± 17.18), clarity of presentation (78.51 ± 14.36), applicability (54.61 ± 22.63) and editorial independence (68.42 ± 13.06). In the seven domains of the RIGHT standard, the reporting rate of the recommendation domain was the lowest (52.86%).The highest reporting rate was the other information domain, which was 68%.There was a high correlation between reporting the completeness of CPGs using the AGREE II instrument and RIGHT standard (r = 0.77, P < 0.001). CONCLUSIONS: The paediatric CPGs from NGC have good quality. There was a high correlation in the completeness of reporting for paediatric CPGs using the AGREE II instrument and RIGHT standard. It could be concluded that the CPGs of good methodological quality have good reporting quality. Maybe the researcher should effectively combine the AGREE II instrument and RIGHT standard in the development process of CPGs.

A hybrid material prepared by controlled growth of a covalent organic framework on amino-modified MIL-68 for pipette tip solid-phase extraction of sulfonamides prior to their determination by HPLC.

A hybrid material was synthesized by growing a covalent organic framework (COF) in-situ on the surface of functionalized metal organic framework (MOF). Specifically, the amino-modified MOF (type MIL-68) was obtained by reacting indium(III) nitrate and 2-aminoterephthalic acid. Subsequently, it was reacted with tris(4-formylphenyl)amine and tris(4-aminophenyl)amine to obtain the final hybrid COF. This material overcomes the disadvantage of MOF concerning poor stability in aqueous solution and it combines the advantages of MOF and COF. This MOF@COF hybrid material is shown to be a viable adsorbent for the extraction of sulfonamides by pipette tip solid-phase extraction). Following elution with acetonitrile, the sulfonamides were quantified by high performance liquid chromatography using variable wavelength detection (HPLC-VWD). The structure and morphology of the material was characterized by various techniques. Extraction parameters such as amount of adsorbent, sampling rate, sample pH, elution solvent and sample volume were investigated. Under the optimum conditions, the sulfonamides tested (sulfadimethoxine sulfamethoxazole, sulfamonomethoxine, sulfamethazine, sulfamerazine and sulfadiazine) can be determined over a wide linear range (10-2000 ng·mL-1), with low limits of detection (1 ng·mL-1) and high precision (RSD <5.2%). The method was applied the determination of sulfonamide residues in (spiked) environmental water, milk and meat samples and gave recoveries in the range from 68.9-103.8%, with RSDs of <6.6%. The packed pipette tip column exhibits excellent stability, reproducibility and high adsorption capacity. Graphical abstract A hybrid sorbent was prepared by controlled growth of a covalent organic framework on amino-modified MIL-68 and packed into a pipette tip for sulfonamide extraction. The sensitivity was dramatically increased after optimized extraction, with limit of detection as low as 1 ng·mL-1.

Synergized Multimodal Therapy for Safe and Effective Reversal of Cancer Multidrug Resistance Based on Low-Level Photothermal and Photodynamic Effects.

Despite the therapeutic usefulness of near-infrared irradiation (NIR)-induced potent photothermal effects (PTE) and photodynamic effects (PDE), they inevitably damage normal tissues, often posing threat to life when treating tumors adjacent to key organs or major blood vessels. In this study, the frequently overlooked, "weak" PTE and PDE (no killing capability) are employed to synergize chemotherapy against multidrug resistance (MDR) without impairing normal tissues. An NIR-responsive nanosystem, gold (Au)-nanodot-decorated hollow carbon nanospheres coated with hyaluronic acid, is synthesized as a doxorubicin (DOX) carrier with excellent photothermal and photodynamic properties. Upon low-level infrared irradiation, the mild heat of weak PTE moderately boosts DOX unloading, meanwhile the weak PDE moderately disturbs the P-glycoprotein function for retaining intracellular DOX by impairing mitochondrial ATP production. These two "moderate" alterations are quantitatively and functionally sufficient to augment the efficacy of chemotherapy in reversing MDR without damaging neighboring tissue. Thus, this work creates a gold-dot-decorated nanocarbon spheres based nanosystem for trimodal therapy, reveals the therapeutic value of the frequently ignored weak PTE/PDE, and demonstrates that synergizing with chemotherapy to overcome drug resistance does not necessarily require potent PTE/PDE.

Space debris detection in optical image sequences.

We present a high-accuracy, low false-alarm rate, and low computational-cost methodology for removing stars and noise and detecting space debris with low signal-to-noise ratio (SNR) in optical image sequences. First, time-index filtering and bright star intensity enhancement are implemented to remove stars and noise effectively. Then, a multistage quasi-hypothesis-testing method is proposed to detect the pieces of space debris with continuous and discontinuous trajectories. For this purpose, a time-index image is defined and generated. Experimental results show that the proposed method can detect space debris effectively without any false alarms. When the SNR is higher than or equal to 1.5, the detection probability can reach 100%, and when the SNR is as low as 1.3, 1.2, and 1, it can still achieve 99%, 97%, and 85% detection probabilities, respectively. Additionally, two large sets of image sequences are tested to show that the proposed method performs stably and effectively.

Active metals decorated NiCo2O4 yolk-shell nanospheres as nanoreactors for catalytic reduction of nitroarenes and azo dyes.

Transition-metal oxides (TMOs) have received a great deal of research attention and have been widely used in a variety of fields. However, conventional TMOs do not possess high specific surface area, sufficient active site on their surfaces, and limited their applications in catalysis. This study presents a two-step method for synthesizing active metal (M) decorated NiCo2O4 (M/NiCo2O4, M = Pd or Cu) nanospheres with yolk-shell nanostructures. Taking advantage of the unique morphology and the combination of dual active components (i.e., active NiCo2O4 substrate and decorated active metal), the as-prepared M/NiCo2O4 yolk-shell nanospheres can be employed as nanoreactors in the organic reactions. In catalyzing the reduction of a representative nitroarene (i.e., 4-NP) by NaBH4, the Pd/NiCo2O4 nanoreactors exhibit a superior catalytic efficiency to their counterparts (Cu/NiCo2O4 and NiCo2O4). The turnover frequency is much higher than that of various TMOs supported nanocatalysts have been reported over the past five years. Furthermore, the Pd/NiCo2O4 nanoreactors show excellent stability and common applicability of the reduction of various substituted nitrobenzenes and azo dyes. This work provides new rational design concept and preparation strategy for efficient nanoreactors with dual active components and sheds light on the practical application of chemical reactions.

A Graphene Composite Film Based Wearable Far-Infrared Therapy Apparatus (GRAFT) for Effective Prevention of Postoperative Peritoneal Adhesion.

Postoperative peritoneal adhesion (PPA) is the most frequent complication after abdominal surgery. Current anti-adhesion strategies largely rely on the use of physical separating barriers creating an interface blocking peritoneal adhesion, which cannot reduce inflammation and suffers from limited anti-adhesion efficacy with unwanted side effects. Here, by exploiting the alternative activated macrophages to alleviate inflammation in adhesion development, a flexible graphene-composite-film (F-GCF) generating far-infrared (FIR) irradiation that effectively modulates the macrophage phenotype toward the anti-inflammatory M2 type, resulting in reduced PPA formation, is designed. The anti-adhesion effect of the FIR generated by F-GCF is determined in the rat abdominal wall abrasion-cecum defect models, which exhibit reduced incidence and area of PPA by 67.0% and 92.1% after FIR treatment without skin damage, significantly superior to the clinically used chitosan hydrogel. Notably, within peritoneal macrophages, FIR reduces inflammation reaction and promotes tissue plasminogen activator (t-PA) level via the polarization of peritoneal macrophages through upregulating Nr4a2 expression. To facilitate clinical use, a wirelessly controlled, wearable, F-GCF-based FIR therapy apparatus (GRAFT) is further developed and its remarkable anti-adhesion ability in the porcine PPA model is revealed. Collectively, the physical, biochemical, and in vivo preclinical data provide compelling evidence demonstrating the clinical-translational value of FIR in PPA prevention.

Performance Regulation of Single-Atom Catalyst by Modulating the Microenvironment of Metal Sites.

Metal-based catalysts, encompassing both homogeneous and heterogeneous types, play a vital role in the modern chemical industry. Heterogeneous metal-based catalysts usually possess more varied catalytically active centers than homogeneous catalysts, making it challenging to regulate their catalytic performance. In contrast, homogeneous catalysts have defined active-site structures, and their performance can be easily adjusted by modifying the ligand. These characteristics lead to remarkable conceptual and technical differences between homogeneous and heterogeneous catalysts. As a recently emerging class of catalytic material, single-atom catalysts (SACs) have become one of the most active new frontiers in the catalysis field and show great potential to bridge homogeneous and heterogeneous catalytic processes. This review documents a brief introduction to SACs and their role in a range of reactions involving single-atom catalysis. To fully understand process-structure-property relationships of single-atom catalysis in chemical reactions, active sites or coordination structure and performance regulation strategies (e.g., tuning chemical and physical environment of single atoms) of SACs are comprehensively summarized. Furthermore, we discuss the application limitations, development trends and future challenges of single-atom catalysis and present a perspective on further constructing a highly efficient (e.g., activity, selectivity and stability), single-atom catalytic system for a broader scope of reactions.

Parallel Multistage Wide Neural Network.

Deep learning networks have achieved great success in many areas, such as in large-scale image processing. They usually need large computing resources and time and process easy and hard samples inefficiently in the same way. Another undesirable problem is that the network generally needs to be retrained to learn new incoming data. Efforts have been made to reduce the computing resources and realize incremental learning by adjusting architectures, such as scalable effort classifiers, multi-grained cascade forest (gcForest), conditional deep learning (CDL), tree CNN, decision tree structure with knowledge transfer (ERDK), forest of decision trees with radial basis function (RBF) networks, and knowledge transfer (FDRK). In this article, a parallel multistage wide neural network (PMWNN) is presented. It is composed of multiple stages to classify different parts of data. First, a wide radial basis function (WRBF) network is designed to learn features efficiently in the wide direction. It can work on both vector and image instances and can be trained in one epoch using subsampling and least squares (LS). Second, successive stages of WRBF networks are combined to make up the PMWNN. Each stage focuses on the misclassified samples of the previous stage. It can stop growing at an early stage, and a stage can be added incrementally when new training data are acquired. Finally, the stages of the PMWNN can be tested in parallel, thus speeding up the testing process. To sum up, the proposed PMWNN network has the advantages of: 1) optimized computing resources; 2) incremental learning; and 3) parallel testing with stages. The experimental results with the MNIST data, a number of large hyperspectral remote sensing data, and different types of data in different application areas, including many image and nonimage datasets, show that the WRBF and PMWNN can work well on both image and nonimage data and have very competitive accuracy compared to learning models, such as stacked autoencoders, deep belief nets, support vector machine (SVM), multilayer perceptron (MLP), LeNet-5, RBF network, recently proposed CDL, broad learning, gcForest, ERDK, and FDRK.

Probing the Activity Enhancement of Carbocatalyst with the Anchoring of Atomic Metal.

Enhanced catalysis for organic transformation is essential for the synthesis of high-value compounds. Atomic metal species recently emerged as highly effective catalysts for organic reactions with high activity and metal utilization. However, developing efficient atomic catalysts is always an attractive and challenging topic in the modern chemical industry. In this work, we report the preparation and activity enhancement of nitrogen- and sulfur-codoped holey graphene (NSHG) with the anchoring of atomic metal Pd. When employed as the catalyst for nitroarenes reduction reactions, the resultant Pd/NSHG composite exhibits remarkably high catalytic activity due to the co-existence of dual-active components (i.e., catalytically active NSHG support and homogeneous dispersion of atomic metal Pd). In the catalytic 4-nitrophenol (4-NP) reduction reaction, the efficiency (turnover frequency) is 3.99 × 10-2 mmol 4-NP/(mg cat.·min), which is better than that of metal-free nitrogen-doped holey graphene (NHG) (2.3 × 10-3 mmol 4-NP/(mg cat.·min)) and NSHG carbocatalyst (3.8 × 10-3 mmol 4-NP/(mg cat.·min)), the conventional Pd/C and other reported metal-based catalysts. This work provides a rational design strategy for the atomic metal catalysts loaded on active doped graphene support. The resultant Pd/NSHG dual-active component catalyst (DACC) is also anticipated to bring great application potentials for a broad range of organic fields, such as organic synthesis, environment treatment, energy storage and conversion.

Facile Construction of 2D/2D ZnIn2S4-Based Bifunctional Photocatalysts for H2 Production and Simultaneous Degradation of Rhodamine B and Tetracycline.

A two-dimensional/two-dimensional (2D/2D) TiO2/ZnIn2S4 photocatalyst was reasonably proposed and constructed by a two-step oil bath-hydrothermal method. TiO2 nanosheets uniformly grown on the surface of ZnIn2S4 nanosheets and a synergetic effect between the TiO2 and ZnIn2S4 could highly contribute to improving the specific surface area and hydrophilicity of ZnIn2S4 as well as accelerating the separation and transfer of photon-generated e--h+ pairs, and thus enhancing the visible-light photocatalytic degradation and H2 evolution performance of ZnIn2S4. Rhodamine B (RhB) and tetracycline (TC) were simultaneously selected as the target pollutants for degradation in the work. The optimum photocatalytic RhB and TC degradation properties of TiO2/ZnIn2S4-10 wt% were almost 3.11- and 8.61-fold higher than that of pure ZnIn2S4, separately, while the highest photocatalytic hydrogen evolution rate was also observed in the presence of TiO2/ZnIn2S4-10wt% and 4.28-fold higher than that of ZnIn2S4. Moreover, the possible photocatalytic mechanisms for enhanced visible-light photocatalytic degradation and H2 evolution were investigated and proposed in detail. Our research results open an easy pathway for developing efficient bifunctional photocatalysts.

In situ fabrication of a novel CdS/ZnIn2S4/g-C3N4 ternary heterojunction with enhanced visible-light photocatalytic performance.

In this study, a novel g-C3N4-based ternary heterojunction was rationally designed and constructed by the in situ growth of ZnIn2S4 nanosheets and CdS nanoparticles onto the g-C3N4 nanosheets using a facile two-step oil-bath method. Through optimizing the proportion of ZnIn2S4 and CdS component, g-C3N4 nanosheets coupled with ZnIn2S4 nanosheets and CdS nanoparticles (denoted as CdS/ZnIn2S4/g-C3N4) exhibited obviously higher photocatalytic properties for RhB removal than the single-component and dual-component systems. Among the as-obtained ternary photocatalysts, it was found that the ternary CdS/ZnIn2S4/g-C3N4-0.2 photocatalyst displayed the optimum photocatalytic property (96%) within a short time (30 min), which was almost 27.42 and 1.17 times higher than that of pure g-C3N4 and binary ZnIn2S4/g-C3N4-0.7 composite. The excellent activity of the ternary CdS/ZnIn2S4/g-C3N4 heterostructure is assigned to the synergetic effects of CdS nanoparticles, ZnIn2S4 nanosheets and g-C3N4 nanosheets, which not only broaden the visible-light absorption range, but also improve the charge mobility and separation rate, thus boosting the visible-light-driven photocatalytic property of g-C3N4.

Porous biochar-supported MnFe2O4 magnetic nanocomposite as an excellent adsorbent for simultaneous and effective removal of organic/inorganic arsenic from water.

To solve the problem of organic and inorganic arsenic species contamination in drinking water and/or wastewater, porous biochar-supported MnFe2O4 magnetic nanocomposite (BC-MF) was successfully fabricated and used as an excellent adsorbent for simultaneous removal of p-ASA and As(V) from water environment. This obtained BC-MF displayed remarkable adsorption performance for both p-ASA and As(V) removal at acidic and neutral pH (3-7), and di-anionic and mono-anionic species of p-ASA and As(V) facilitated the adsorption process. Specifically, BC-MF exceeded some reported adsorbents, and the adsorption capacities of p-ASA and As(V) were approximately 105 and 90 mg/g at a 10 µg/L equilibrium concentration. Satisfactory adsorption behavior including adsorption isotherms, competitive ions, humic acid (HA), and regeneration/reusability property in single and binary systems demonstrated the BC-MF can improve the potential application for arsenic-containing wastewater remediation. Proposed adsorption mechanism indicated that electrostatic interaction and surface complexation were involved the p-ASA and As(V) immobilization, whereas hydrogen bonding and π-π interactions may also contribute to the p-ASA removal. Additionally, the prominent sequestration p-ASA and As(V) performance in different water matrix and fixed-bed column studies indicated that BC-MF was a promising nanocomposite for simultaneously removal of organic and inorganic arsenic species in practical wastewater treatment.

Probing Activity Enhancement of Photothermal Catalyst under Near-Infrared Irradiation.

Exploring highly efficient catalysts with excellent photothermal conversion and further unveiling their catalytic mechanism are of significant importance for photothermal catalysis technologies, but there remain grand challenges to these activities. Herein, we fabricate a nest-like photothermal nanocatalyst with Pd decorated on a N-doped carbon functionalized Bi2S3 nanosphere (Bi2S3@NC@Pd). Given its well-dispersed ultrafine Pd nanoparticles and the excellent photothermal heating ability of support material, the Bi2S3@NC@Pd composite exhibits a superior activity and photothermal conversion property to commercial Pd/C catalyst for hydrogenation of organic dyes upon exposure to near-infrared (NIR) light irradiation. In addition, the photothermal effect (temperature rise) and activity enhancement of the heterogeneous catalysis system are further probed by comparing the reaction rate with and without the NIR light irradiation. Furthermore, the catalytic behaviors of the Bi2S3@NC@Pd catalyst under conventional and photothermal heating are investigated at the same reaction temperature. This work not only improves our fundamental understanding of the catalytic behavior in heterogeneous liquid-solid reaction systems under near-infrared irradiation but also may promote the design of catalysts with photothermally promoted activity.

3D nitrogen-doped carbon nanofoam arrays embedded with PdCu alloy nanoparticles: Assembling on flexible microelectrode for electrochemical detection in cancer cells.

In this work, we developed a novel and facile strategy for the synthesis of a highly active and stable electrocatalyst based on PdCu alloy nanoparticles (PdCu-ANPs) embedded in 3D nitrogen-doped carbon (NC) nanofoam arrays (NFAs), which were assembled on flexible carbon fiber (CF) microelectrode for in situ sensitive electrochemical detection of biomarker H2O2 in cancer cells. Our results showed that NC-NFAs support possessed a unique hierarchically porous architecture by integrating the macrospores in arrays scaffold within mesopores in individual NC nanofoam, which offered exceptionally large surface area for embedding high-density PdCu-ANPs in it as well as facilitated the mass transfer and molecular diffusion during the electrochemical reaction. Taking the advantages of the unique structural merit of NC-NFAs support and excellent electrocatalyitc properties of PdCu-ANPs that embedded in it, the resultant PdCu-ANPs/NC-NFAs modified CF microelectrode exhibited good electrochemical sensing performances towards H2O2 including a wide linear range from 2.0 µM to 3.44 mM, a low detection limit of 500 nM, as well as good reproducibility, stability and anti-interference ability. When used in real-time in situ tracking H2O2 secreted from different types of human colorectal cancer cells, i.e., HCT116, HT29, SW48 and LoVo, it can distinguish the types of cancer cells by measuring the number of extracellular H2O2 molecules released per cell, which demonstrates its great promise in cancer diagnose and management.

Comparison in enantioseparation performance of chiral stationary phases prepared from chitosans of different sources and molecular weights.

The aim of the present study was to compare the enantioseparation performance of chiral stationary phases (CSPs) which were derived from chitosans of different sources and molecular weights. Therefore, chitosans of shrimp and crab shells were prepared. The viscosity-average molecular weights of the chitosans both prepared from shrimp and crab shells were 2.8 × 105 and 1.4 × 105. The chitosans were isobutyrylated yielding isopropylcarbonyl chitosans which were then derivatized with 4-methylphenyl isocyanate to provide chitosan 3,6-bis(4-methylphenylcarbamate)-2-(isobutyrylamide)s. The chitosan 3,6-bis(4-methylphenylcarbamate)-2-(isobutyrylamide)s were used as chiral selectors (CSs) with which the corresponding CSPs were prepared. With the same chiral analytes and under the same mobile phase conditions, the enantioseparation capability of the CSPs was evaluated by high-performance liquid chromatography. In two CSs prepared from the same source, the one with higher molecular weight showed better enantioseparation capability; in two CSs prepared with the chitosans of the same molecular weight, the one derived from shrimp shell exhibited better performance. With regard to the two shrimp chitosan CSs, most of chiral analytes interacted more strongly with the one with lower molecular weight, and an opposite trend was found for the two crab chitosan CSs. Based on the results observed in the present study and in previous work, we believe that the influence of molecular weight on CSP enantioseparation performance is related to the substituent introduced in the CS molecule.

An evidence map of clinical practice guideline recommendations and quality on diabetic retinopathy.

To present an evidence map for explicating research trends and gaps, we systematically review clinical practice guidelines (CPGs) on diabetic retinopathy (DR) and assess the quality of CPGs and consistency of recommendations. A literature search was performed in PubMed, Embase, Web of Science, CPG databases, and website of diabetes society to include the CPGs. The basic information, methodological quality, and reporting quality of CPGs, recommendations for DR were exacted by the Excel 2013. Methodological and reporting quality of DR CPGs were evaluated by AGREE II instrument and RIGHT checklist. The bubble plot format of evidence map was made by Excel 2013. Nineteen CPGs proved eligible, which included eight DR CPGs and 11 comprehensive diabetic CPGs. The identified CPGs were of mixed quality and they scored poorly in the rigor of development, applicability domains by AGREE II. Field two (background) had the highest reporting rate (86.31%) and field five (review and quality assurance) obtained the lowest reporting rate (31.58%) among the seven domains of RIGHT checklist. According to the recommendations of CPGs, there were three inconsistencies in the screening of DR, and CPGs recommendations for treatment were consistent on the whole. At the same time, recommendations for laser therapy were not accurate. Some recommendations were not specific and clear in some DR CPGs. This evidence map could collect and evaluate the characteristics of published CPGs, add to our knowledge and promote the development of trustworthy CPGs for DR.

Fabrication of porphyrin-based magnetic covalent organic framework for effective extraction and enrichment of sulfonamides.

The dehydration reaction of tetraamino porphyrin and 4,4'-biphenyldicarboxaldehyde was performed for the synthesis of a novel covalent organic framework (COF), which was decorated on magnetic Fe3O4 to obtain core-shell structured Fe3O4@COFs nanospheres for the first time, for effective extraction and enrichment of sulfonamides (SAs). The morphology and structure of the synthesized nanospheres were characterized through various methods. The extraction conditions for six SAs including sulfadiazine, sulfamerazine, sulfamethazine, sulfamonomethoxine, sulfamethoxazole, sulfadimethoxine were systematically optimized. Fe3O4@COFs nanospheres were evaluated for magnetic solid-phase extraction. By coupling with high-performance liquid chromatography, a facile and sensitive method was established for the quantitation analysis of six SAs. The method showed good linearity ranging from 1 to 500 ng mL-1 with R2 > 0.99, high sensitivity with LODs in the range of 0.2-1 ng mL-1, and high precision with RSDs≤6.3%. This method was further applied into determination of SAs in environmental water and food samples, with recoveries in the range of 65.3%-107.3% and RSDs≤6.7%. These successful applications suggest that the core-shell structured Fe3O4@COFs nanospheres could be used as a potential adsorbent for efficient extraction and analysis of trace SAs.

Structure screening and performance restoration of chiral separation materials based on chitosan derivatives.

In order to screen chiral selector structure and find structure-property relationship, ten chitosan 3,6-bis(phenylcarbamate)-2-(cyclopropylformamide)s were synthesized from which corresponding chiral stationary phases were prepared. Enantioseparation capability and mobile phase tolerability of the chiral stationary phases were evaluated. The chiral selectors with 3-chloro-4-methylphenyl, 4-chlorophenyl, 3-chlorophenyl, 3,5-dichlorophenyl and 4-trifluoromethoxyphenyl groups demonstrated powerful enantioseparation capability. Enantioseparation capability was found to be dependent on a match between the substituent at C2 and the one attached to phenyl group at C3/C6 of glucose unit in the chitosan derivatives. Moreover, the tolerability tests revealed that the developed chiral stationary phases were highly tolerable to pure ethyl acetate, pure acetone and n-hexane/tetrahydrofuran of various ratios. In addition, n-hexane/tetrahydrofuran was found to be a modifier to adjust suprastructure of the chitosan derivatives, resulting in an improvement or restoration in enantioseparation. This observation implies n-hexane/tetrahydrofuran may make a damaged chiral selector restore its enantioseparation capability.