Research progress of yolk-shell structured nanoparticles and their application in catalysis.

Yolk-shell nanoparticles (YSNs) have attracted a broad interest in the field of catalysis due to their unique structure and properties. The hollow structure of YSNs brings high porosity and specific surface areas which is conducive to the catalytic reactions. The flexible tailorability and functionality of both the cores and shells allow a rational design of the catalyst and may have synergistic effect which will improve the catalytic performance. Herein, an overview of the research progress with respect to the synthesis and catalytic applications of YSNs is provided. The major strategies for the synthesis of YSNs are presented, including hard template method, soft template method, ship-in-a-bottle method, galvanic replacement method, Kirkendall diffusion method as well as the Ostwald ripening method. Moreover, we discuss in detail the recent progress of YSNs in catalytic applications including chemical catalysis, photocatalysis and electrocatalysis. Finally, the future research and development of YSNs are prospected.

Amphiphilic ligand in situ assembly of uranyl active sites and selective interactions of molybdenum disulfide.

Removal of radioactive uranyl ions (UO22+) from water by effective adsorbents is highly desired but remains a challenge. UO22+ are easily combined with H2O, and the polarization of H2O affects the complexation between UO22+ and the adsorbent. Thus, it is necessary to reconstruct the UO22+ active site to improve the adsorption capacity. Herein ，an amphiphilic ligand, namely N, N-dimethyl-9-decenamide (NND), is successfully prepared. NND replace H2O in [UO2(H2O)5]2+ by hydrogen bonding, thereby enhancing the adsorption capacity of MoS2 particles in the reconstituted UO22+ active sites. The predicted maximum adsorption capacity increased from 50.7 to 500.7 mg g- 1 (by a factor of 9.87) with the presence of NND, which is higher than other functional group-modified MoS2 adsorbents. Furthermore, NND and MoS2 can retain UO22+ uptake under extreme conditions including high acid-base and gamma irradiation. Theoretical Calculations of NND through H bonding produces an increased amount of charge transfer and a reduced adsorption energy between UO22+ and MoS2, which weakens the polarization effect of H2O. The findings showed that NND appeared to be a promising amphiphilic to improve the adsorption efficiency of UO22+ from water.

Selection and Validation of Reference Genes for RT-qPCR Analysis in Tibetan Medicinal Plant Saussurea Laniceps Callus under Abiotic Stresses and Hormone Treatments.

Real-time quantitative PCR (RT-qPCR) is an important technique for studying gene expression analysis, but accurate and reliable results depend on the use of a stable reference gene. This study proposes to test the expression stability of candidate reference genes in the callus of Saussurea laniceps, a unique Tibetan medicinal plant. Based on the S. laniceps callus transcriptome, eleven candidate reference genes, including TUA2, TUB3, TUB8, TIF3B1, TIF3H1, ELF5A, PP2AA2, UEV1D, UBL5, UBC36, and SKIP1), were validated for RT-qPCR normalization in the callus under abiotic stress (salt, cold, and UV) and hormone treatments (abscisic acid, MeJA, and salicylic acid). The stability of the candidate genes was evaluated in all the samples of S. laniceps. Comprehensive analysis of all samples showed that the best reference genes were UBC36 and UBL5. ELF5A and TIF3B1 were ranked as the most stable genes in the sample sets under abiotic stress. For hormone stimulation, UBC36 and TIF3H1 genes had the best stability. This study provides useful guidelines and a starting point for reference gene selection for expression analysis using RT-qPCR techniques in S. laniceps.

[Spatio-Temporal Distribution and Risk Assessment of Heavy Metals in Middle and Lower Reaches of Le'an River].

The Le'an River is a main tributary of the Poyang Lake, which is the largest freshwater lake in China. The aim of this study is to research the distribution and potential ecological risks of heavy metals in the middle and lower reaches of the Le'an River, which is contaminated by nearby copper mines. Sediment and water samples were collected from 12 stations during the dry, wet, and normal season in 2016, respectively. The geo-accumulation index and potential ecological risk index were used to determine general pollution characteristics of trace metals in sediments. Results suggested that sediments in the Le'an River were considerably polluted by Cd, Pb, Cu, and Zn. Sediment concentrations of heavy metals showed significant spatial variations. The concentrations of heavy metals such as Cu, Zn, and Cd in water are higher in the dry season than in the normal and wet seasons. The distribution of heavy metals along the river is influenced by hydraulic conditions. The flow velocities in wet and normal seasons are positively correlated with the concentrations of heavy metals such as Cd, Pb, Cu, and Cr. There are seasonal differences in the distribution characteristics of heavy metals in surface sediments. In the dry season, the concentration of heavy metals in sediments is the highest in the middle reaches of rivers near mining areas, while during the wet and normal season, it reaches the highest value in the lower reach near the estuary. Except for Cd, whose major form of heavy metal in the sediment is in an exchanging state, the other heavy metals occur mainly in stable states. The assessment of the geo-accumulation index showed significant Cu, Cd, and Cr pollution. Among the heavy metals investigated, Cd was likely to result in more harmful effects.

[Thermal desorption sampling-gas chromatography-tandem mass spectrometry with a carbonyl-iron powder composite silica monolithic column for enrichment and determination of pyrethroid pesticide residues in tea samples].

Long-term exposure to pyrethroid insecticides is detrimental to the nervous system, reproductive system, and immune system in humans. Therefore, enrichment detection of pyrethroid pesticides is imperative. In this study, a novel carbonyl-iron powder composite silica monolithic column was first prepared for the enrichment of pyrethroid pesticide residues in tea samples. Then, the target analytes were thermally desorbed and online-injected into a gas chromatography-tandem mass spectrometry (GC-MS/MS) system. In the present method, hydroxy-terminated polydimethylsiloxane (PDMS) was covalently bonded to the surface of the SiO2 network and subsequently bonded with the carbonyl-iron powder. After the target analytes were adsorbed and concentrated in the PDMS spots, high-frequency induction heating was used for GC-MS/MS sampling. Under the optimal conditions, the detection limits of the pyrethroid pesticide residues were 3.8 to 7.5 µg/kg, and the relative standard deviation was 3.2% to 6.8% (n=6). The extraction recovery ranged from 97.7% to 110.5%, and the correlation coefficient was ≥ 0.9960. In addition, the enrichment factor could reach 1000 times. PDMS materials show excellent adsorption properties for non-polar solutes. In our experiment, carbonyl iron powder-bonded monolithic columns were prepared on the basis of stir bar sorptive extraction (SBSE). Carbonyl iron powder magnetic particles were evenly implanted into the inorganic-organic hybrid cassia material for realizing rapid and uniform desorption upon electromagnetic induction heating. Under the premise of perfectly integrating the technical advantages of SBSE and solid-phase microextraction (SPME), the electromagnetic induction characteristics of carbonyl iron powder can be exploited for thermal desorption and directly combined with GC-MS to facilitate online analysis and solvent-free elution. Compared with the conventional SPME method, the proposed method has the advantages of high enrichment factor, large adsorption capacity of the column, reusability, high degree of automation, and good universality. This method has high significance for sample preparation and for the extraction of pesticide residues in complex matrices.

Electrospun Sesbania Gum-Based Polymeric N-Halamines for Antibacterial Applications.

Microorganism pollution induced by pathogens has become a serious concern in recent years. In response, research on antibacterial N-halamines has made impressive progress in developing ways to combat this pollution. While synthetic polymer-based N-halamines have been widely developed and in some cases even commercialized, N-halamines based on naturally occurring polymers remain underexplored. In this contribution, we report for the first time on a strategy for developing sesbania gum (SG)-based polymeric N-halamines by a four-step approach Using SG as the initial polymer, we obtained SG-based polymeric N-halamines (abbreviated as cSG-PAN nanofibers) via a step-by-step controllable synthesis process. With the assistance of advanced techniques, the as-synthesized cSG-PAN nanofibers were systematically characterized in terms of their chemical composition and morphology. In a series of antibacterial and cytotoxicity evaluations, the as-obtained cSG-PAN nanofibers displayed good antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as low cytotoxicity towards A549 cells. We believe this study offers a guide for developing naturally occurring polymer-based antibacterial N-halamines that have great potential for antibacterial applications.

Sesbania Gum-Supported Hydrophilic Electrospun Fibers Containing Nanosilver with Superior Antibacterial Activity.

In this contribution, we report for the first time on a new strategy for developing sesbania gum-supported hydrophilic fibers containing nanosilver using electrospinning (SG-Ag/PAN electrospun fibers), which gives the fibers superior antibacterial activity. Employing a series of advanced technologies-scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV-visible absorption spectroscopy, X-ray photoelectron spectroscopy, and contact angle testing-we characterized the as-synthesized SG-Ag/PAN electrospun fibers in terms of morphology, size, surface state, chemical composition, and hydrophilicity. By adjusting the synthesis conditions, in particular the feed ratio of sesbania gum (SG) and polyacrylonitrile (PAN) to Ag nanoparticles (NPs), we regulated the morphology and size of the as-electrospun fibers. The fibers' antibacterial properties were examined using the colony-counting method with two model bacteria: Escherichia coli (a Gram-negative bacterium) and Staphylococcus aureus (a Gram-positive bacterium). Interestingly, compared to Ag/PAN and SG-PAN electrospun fibers, the final SG-Ag/PAN showed enhanced antibacterial activity towards both of the model bacteria due to the combination of antibacterial Ag NPs and hydrophilic SG, which enabled the fibers to have sufficient contact with the bacteria. We believe this strategy has great potential for applications in antibacterial-related fields.

[Determination of 39 veterinary drug residues in Procambarusclarkii by ultra-high performance liquid chromatography-quadrupole-time of flight mass spectrometry].

An ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS) method was developed for determination of 39 veterinary drugs in Procambarusclarkii. Samples were extracted with acidified acetonitrile and purified with enhanced matrix removal-lipid (EMR-Lipid) adsorbent and graphitized multi-walled carbon nanotubes (GMWNTs). Extracts were analyzed by UHPLC-Q-TOF-MS. Target compounds were screened according to accurate mass, isotopic ratio, and retention time, and confirmed by library search. Target analytes were quantified using the chromatographic peak area of each compound. For each of the drugs of interest, calibration curves were linear in their respective ranges with correlation coefficients greater than 0.99. The limits of quantification (LOQs) were 3-15 µg/kg. The recoveries for target compounds spiked in Procambarusclarkii ranged from 62.4% to 105.8%, with relative standard deviations (RSDs) ranging from 2.5% to 13.5%. This method is simple, rapid, accurate, and suitable for simultaneous determination of 39 veterinary drugs, including sulfonamides, quinolones, and triphenylmethane, extracted from Procambarusclarkii.

[Rapid determination of 204 pesticide residues in tea by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry].

An analytical method was established for the simultaneous determination of 204 pesticide residues in tea by ultra performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS). The samples were extracted with acetonitrile, and cleaned-up by solid phase extraction (SPE) with a Carb-PSA cartridge, eluted with acetonitrile-toluene (3:1, v/v), determined by UPLC-Q-TOF/MS and quantified by external standard method. A data base of the accurate mass numbers and a library which contains the 204 pesticides were established. The automatic retrieval of detection results was carried on according to the characteristics of the compound, such as accurate mass, retention time, isotopic ratio, and so on. Based on the above results, the qualitative identifications of the 204 pesticides were accomplished without the contrast of standard substances. The results indicated that this method can be used to determine the 204 pesticides in tea. At the three spiked levels of 10, 20, 50 µg/kg, mean recoveries for the 204 pesticides in tea were between 68. 1% and 117. 2%, with the relative standard deviations (RSDs) ranging from 3.1% to 18.9%. The limits of quantification for the 204 pesticides were lower than 10 µg/kg. The method has been applied to four positive samples, and the results generally accord with the detection results by the method of GB/T 23205-2008. This method has the characteristics of high efficiency, as well as high sensitivity and accuracy, which can meet the requirement of the determination of the 204 pesticides in tea.

[Simultaneous determination of clopidol, sulfonamide and quinolone residues in chickens by ultra performance liquid chromatography-tandem mass spectrometry].

An analytical method for the simultaneous determination of clopidol, sulfadiazine, sulfamethazine, sulfametoxydiazine, sulfamethoxypyridazine, norfloxacin, ofloxacin, ciprofloxacin, enrofloxacin in chickens by ultra performance liquid chromatography coupled with tandem quadrupole mass spectrometry (UPLC-MS/MS) in positive ion mode with multiple reaction monitoring (MRM) has been developed and validated. The samples were homogenized and extracted with acetonitrile. After defatted with high speed frozen centrifugation, the supernatant solution was evaporated and the residue was dissolved with the mobile phase and defatted with n-hexane. It was then analyzed with UPLC-MS/MS. The limit of detection of this method was 0.1 microg/kg, and the limit of quantification was 0.5 microg/kg. The average recoveries (spiked at the levels of 0.5, 1.0, 2.0 microg/kg) ranged from 81.5% to 97.6%, with the relative standard deviations between 2.1% and 8.9%. The results demonstrated that the method is simple, accurate and suitable for the identification and quantification of these drug residues in chickens.