Unraveling Different Reaction Characteristics of Alkoxy Radicals in a Co(II)-Activated Peracetic Acid System Based on Dynamic Analysis of Electron Distribution.

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) have shown broad application prospects in organic wastewater treatment. Alkoxy radicals including CH3COO• and CH3COOO• are primary reactive species in PAA-AOP systems; however, their reaction mechanism on attacking organic pollutants still remains controversial. In this study, a Co(II)/PAA homogeneous AOP system at neutral pH was constructed to generate these two alkoxy radicals, and their different reaction mechanisms with a typical emerging contaminant (sulfacetamide) were explored. Dynamic electron distribution analysis was applied to deeply reveal the radical-meditated reaction mechanism based on molecular orbital analysis. Results indicate that hydrogen atom abstraction is the most favorable route for both CH3COO• and CH3COOO• attacking sulfacetamide. However, both radicals cannot react with sulfacetamide via the radical adduct formation route. Interestingly, the single-electron transfer reaction is only favorable for CH3COO• due to its lower ESUMO. In comparison, CH3COOO• can react with sulfacetamide via a similar radical self-sacrificing bimolecular nucleophilic substitution (SN2) route owing to its high ESOMO and easy escape of unpaired electrons from n orbitals of O atoms in the peroxy bond. These findings can significantly improve the knowledge of reactivity of CH3COO• and CH3COOO• on attacking organic pollutants at the molecular orbital level.

Comparative transcriptome analysis of different tissues of Rheum tanguticum Maxim. ex Balf. (Polygonaceae) reveals putative genes involved in anthraquinone biosynthesis.

Rheum tanguticum is a perennial herb and an important medicinal plant, with anthraquinones as its main bioactive compounds. However, the specific pathway of anthraquinone biosynthesis in rhubarb is still unclear. The accumulation of anthraquinones in different tissues (root, leaf, stem and seed) of R. tanguticum revealed considerable variation, suggesting possible differences in metabolite biosynthetic pathways and accumulation among various tissues. To better illustrate the biosynthetic pathway of anthraquinones, we assembled transcriptome sequences from the root, leaf, stem and seed tissues yielding 157,564 transcripts and 88,142 unigenes. Putative functions could be assigned to 56,911 unigenes (64.57%) based on BLAST searches against annotation databases, including GO, KEGG, Swiss-Prot, NR, and Pfam. In addition, putative genes involved in the biosynthetic pathway of anthraquinone were identified. The expression profiles of nine unigenes involved in anthraquinone biosynthesis were verified in different tissues of R. tanguticum by qRT-PCR. Various transcription factors, including bHLH, MYB_related, and C2H2, were identified by searching unigenes against plantTFDB. This is the first transcriptome analysis of different tissues of R. tanguticum and can be utilized to describe the genes involved in the biosynthetic pathway of anthraquiones, understanding the molecular mechanism of active compounds in R. tanguticum.

A rapid self-healing hydrogel based on PVA and sodium alginate with conductive and cold-resistant properties.

Self-healing hydrogels as renewable materials have attracted significant attention recently. However, traditional self-healing hydrogels require a long time for self-healing and cannot be used at low temperatures. Besides, their poor biocompatibility limits the application of hydrogels. Herein, we have prepared a hydrogel composed of polyvinyl alcohol (PVA) and modified sodium alginate. Due to the dynamic recombination of borate bonds, these hydrogels show a strong self-healing ability, with the shortest self-healing time up to 15 seconds. Also, glycerin (GI) was added into the hydrogel to increase the cold resistance of the hydrogel. At -25 °C, the hydrogel still displayed good frost resistance and elasticity. NaCl and other inorganic salts were added to endow the hydrogel with good electrical conductivity. The hydrogel also had good skin-like properties and could activate the capacitive screen of an electronic device.

A Facile Strategy to Fabricate Nanoscale Zero-Valent Iron Decorated Graphene Oxide Composite for Dechloridation of Trichloroacetic Acid in Water.

In this study, nanoscale zero-valent iron decorated graphene oxide (NZVI/GO) composite was fabricated through a reduction process in the presence of sodium borohydride (NaBH4) solution. Subsequently, physicochemical properties of the NZVI/GO composites were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transformation infrared spectroscopy (FT-IR) and Raman spectra. Results indicated that Fe species existed in the form of Fe0, which uniformly dispersed on the surface of GO. Furthermore, the performance of NZVI/GO was evaluated by the degradation of tichloroacetic acid (TCAA). TCAA can be rapidly degraded by NZVI/GO. This paper provides a promising strategy to synthesize versatile catalyst which would be potentially applied in sewage treatment to degrade chlorinated organic compounds.

Synthesis of Magnetic CoFe2O4 Nanoparticles and Their Efficient Degradation of Diclofenac by Activating Persulfate via Formation of Sulfate Radicals.

In this study, magnetic CoFe2O4 nanoparticles were synthesized by hydrothermal method by using ferric nitrate and cobalt nitrate as raw materials. Subsequently, physicochemical properties of the resulting CoFe2O4 nanoparticles were systematically studied by scanning electron microscope, X-ray diffraction, N2 adsorption/desorption, Fourier transformation infrared spectroscopy and Vibration sample magnetometer measurement. Results indicated that CoFe2O4 nanoparticles with cubic spinel structure possessed an average diameter of 6.9 nm, specific surface area of 103.48 m2 · g-1, saturation magnetization of 54.65 A · m2(emu · g-1) and coercivity of 1.76×104 A · m-1. Furthermore, scavenging experiments revealed that sulfate radicals (.SO-4) was the main active species derived from persulfates, in which 72.3% of diclofenac could be degraded within 30 min treatment. This study provides a promising strategy to synthesize versatile catalyst which would be potentially applied in pharmaceutical wastewater purification.

Fabrication of Silver Decorated Graphene Oxide Composite for Photocatalytic Inactivation of Escherichia coli.

In this study, silver decorated graphene oxide (Ag/GO) composite was fabricated through a reduction process in the presence of potassium borohydride solution. Subsequently, physicochemical properties of the resulting Ag/GO composite were studied by scanning electron microscope, X-ray diffraction, Raman spectra, Fourier transformation infrared spectroscopy and UV-visible diffuse reflectance spectrum. Results indicated that Ag species existed in the form of Ag0, which greatly facilitated the visible light absorbance ability. Furthermore, the performance of Ag/GO was evaluated by PC inactiviation of Escherichia coli under Xenon lamp illumination. It was found that Ag/GO sample could kill the Escherichia coli within 60 min illumination by the non-selective attack of ⋅OH radicals. This study provides a novel and facile strategy to fabricate high-efficient catalyst to kill the bacteria in drinking water treatment.

Rapidly recoverable, anti-fatigue, super-tough double-network hydrogels reinforced by macromolecular microspheres.

In this study, a novel strategy was designed to prepare rapidly recoverable, anti-fatigue, super-tough double-network hydrogels by introducing macromolecular microspheres (MMs) as cross-linking centers for hydrophobic associations. MMs were prepared via emulsion polymerization using butyl acrylate (BA) as a main component and dicyclopentyl acrylate (DCPA) as a cross-linker. Then, a double-network (DN) hydrogel was prepared using gelatin as the first network and a copolymer of acrylamide and hexadecyl methacrylate stabilized by MMs as the second network. As a result, the DN hydrogels that were toughened by MMs exhibited an excellent fracture strength of 1.48 MPa and a fracture strain of 2100%. Moreover, the hydrogels exhibited rapid recoverability and fatigue resistance. Therefore, the strategy would open up a novel avenue for the toughening of DN hydrogels for biomedical applications.

Super-tough, ultra-stretchable and strongly compressive hydrogels with core-shell latex particles inducing efficient aggregation of hydrophobic chains.

Toughness, strechability and compressibility for hydrogels were ordinarily balanced for their use as mechanically responsive materials. For example, macromolecular microsphere composite hydrogels with chemical crosslinking exhibited excellent compression strength and strechability, but poor tensile stress. Here, a novel strategy for the preparation of a super-tough, ultra-stretchable and strongly compressive hydrogel was proposed by introducing core-shell latex particles (LPs) as crosslinking centers for inducing efficient aggregation of hydrophobic chains. The core-shell LPs always maintained a spherical shape due to the presence of a hard core even by an external force and the soft shell could interact with hydrophobic chains due to hydrophobic interactions. As a result, the hydrogels reinforced by core-shell LPs exhibited not only a high tensile strength of 1.8 MPa and dramatic elongation of over 20 times, but also an excellent compressive performance of 13.5 MPa at a strain of 90%. The Mullins effect was verified for the validity of core-shell LP-reinforced hydrogels by inducing aggregation of hydrophobic chains. The novel strategy strives to provide a better avenue for designing and developing a new generation of hydrophobic association tough hydrogels with excellent mechanical properties.

[Spectroscopy analysis of sulfonated poly (arylene ether ketone sulfone) on side chain for proton exchange membrane].

A series of poly (arylene ether ketone sulfone) s containing different amino content (Am-PAEKS) were prepared via direct polycondensation reactions, and then the sulfobutyl groups were grafted onto the Am-PAEKS by amidating reaction between the amide groups in Am-PAEKS and carboxylic acid groups in 4-(N-butane sulfonic) aminobenzoic acid. The structures of the compounds and the polymer were confirmed by FTIR and H-NMR. The new characteristic bands at 1 239 and 1 060 cm(-1) were assigned to O=S=O symmetric stretching vibration and asymmetric stretching vibration of the sulfonic groups in sulfonated poly (arylene ether ketone sulfone) on side chain (S-SPAEKS), and the structures of the polymers were further confirmed by 1H NMR spectra, and the proton peak at 1.64 ppm was assigned to the methyl in the middle of the pendant sulfonated aliphatic side chains, which show that the S-SPAEKS had been prepared successfully. In TGA curves we can observe two distinct weight loss steps, the first step was mainly attributed to the splitting-off of the sulfonic acid groups at 300 degrees C, and the second step was mainly attributed to the decomposition of the main chain of the S-SPAEKS at 450 degrees C. This series of SSPAEKS polymers exhibit excellent thermal properties by thermo gravimetric analysis, which can satisfy the basic requirements of proton exchange membrane (PEM) for fuel cells.

Different reaction mechanisms of SO4•- and •OH with organic compound interpreted at molecular orbital level in Co(II)/peroxymonosulfate catalytic activation system.

Hydroxyl radical (•OH) and sulfate radical (SO4•-) produced in advanced oxidation processes (AOPs) have been widely studied for organic contaminants degradation, however, the different radical characteristics and reaction mechanisms on organics degradation are still needed. In this study, a homogeneous Co(II)/peroxymonosulfate activation system was established for caffeine (CAF) degradation, and pH was controlled to regulate the radicals production. The different attack routes driven by SO4•- and •OH were deeply explored by transformation products (TPs) identification and theoretical calculations. Specifically, a method on dynamic electronic structure analysis of reactants (R), transition state (TS) and intermediates (IMs) during reaction was proposed, which was applied to elucidate the underlying mechanism of CAF oxidation by •OH and SO4•- at the molecular orbital level. In total, SO4•- is kinetically more likely to attack CAF than •OH due to its higher oxidation potential and electrophilicity index. Single electron transfer reaction (SET) is only favorable for SO4•-due to its higher electron affinity than •OH, while only •OH can react with CAF via hydrogen atom abstraction (HAA) route. Radical adduct formation (RAF) is the most favorable route for both •OH and SO4•- attack according to both kinetics and thermodynamics results. These findings can significantly promote the understanding on the degradation mechanism of organic pollutants driven by •OH and SO4•- in AOPs.

Insights into performance and mechanism of ZnO/CuCo2O4 composite as heterogeneous photoactivator of peroxymonosulfate for enrofloxacin degradation.

In this study, we designed a plain strategy for fabrication of the novel composite ZnO/CuCo2O4 and applied it as catalyst for peroxymonosulfate (PMS) activation to decompose enrofloxacin (ENR) under simulated sunlight. Compared to ZnO and CuCo2O4 alone, the ZnO/CuCo2O4 composite could significantly activate PMS under simulated sunlight, resulting in the generation of more active radicals for ENR degradation. Thus, 89.2 % of ENR could be decomposed over 10 min at natural pH. Furthermore, the influences of the experimental factors, including the catalyst dose, PMS concentration, and initial pH, on ENR degradation were evaluated. Subsequent active radical trapping experiments indicated that sulfate, superoxide, and hydroxyl radicals together with holes (h+) were involved in the degradation of ENR. Notably, the ZnO/CuCo2O4 composite exhibited good stability. Only 10 % decrease in ENR degradation efficiency was observed after four runs. Finally, several reasonable ENR degradation pathways were proposed, and the mechanism of PMS activation was elucidated. This study provides a novel strategy by integrating state-of-the-art material science and advanced oxidation technology for wastewater treatment and environmental remediation.

[Spectroscopy analysis application on proton exchange membrane with 1,3,4-oxadiazole].

A series of novel Sulfonted poly(arylene ether sulfone)s (SPAES) containing 1,3,4-oxadiazole are prepared via direct polycondensation reactions to precisely control the degree of sulfonation. The structures of these compounds were confirmed by FTIR, H-NMR and TGA. The characteristic peaks of transmittances spectra of C=N were found at 1 603 cm(-1) and by H-NMR further confirm the structures, which has been successful introducing the oxadiazole ring. In each TGA curve can observe two distinct weight loss steps, which the one at 300 degrees C and the second at 450 degrees C were mainly attributed to the splitting-off of sulfonic acid groups and decomposition of the main chain of the SPAES. The TGA exhibit excellent thermal properties may be satisfied with the basic requirements of proton exchange membrane (PEM) for fuel cells.

The Potential Roles of Unique Leaf Structure for the Adaptation of Rheum tanguticum Maxim. ex Balf. in Qinghai-Tibetan Plateau.

Leaves are essential plant organs with numerous variations in shape and size. The leaf size is generally smaller in plants that thrive in areas of higher elevation and lower annual mean temperature. The Qinghai-Tibetan Plateau is situated at an altitude of >4000 m with relatively low annual average temperatures. Most plant species found on the Qinghai-Tibetan Plateau have small leaves, with Rheum tanguticum Maxim. ex Balf. being an exception. Here, we show that the large leaves of R. tanguticum with a unique three-dimensional (3D) shape are potentially an ideal solution for thermoregulation with little energy consumption. With the increase in age, the shape of R. tanguticum leaves changed from a small oval plane to a large palmatipartite 3D shape. Therefore, R. tanguticum is a highly heteroblastic species. The leaf shape change during the transition from the juvenile to the adult phase of the development in R. tanguticum is a striking example of the manifestation of plant phenotypic plasticity. The temperature variation in different parts of the leaf was a distinct character of leaves of over-5-year-old plants. The temperature of single-plane leaves under strong solar radiation could accumulate heat rapidly and resulted in temperatures much higher than the ambient temperature. However, leaves of over-5-year-old plants could lower leaf temperature by avoiding direct exposure to solar radiation and promoting local airflow to prevent serious tissue damage by sunburn. Furthermore, the net photosynthesis rate was correlated with the heterogeneity of the leaf surface temperature. Our results demonstrate that the robust 3D shape of the leaf is a strategy that R. tanguticum has developed evolutionarily to adapt to the strong solar radiation and low temperature on the Qinghai-Tibetan Plateau.

Poly (lactic acid) blends with excellent low temperature toughness: A comparative study on poly (lactic acid) blends with different toughening agents.

Poly (lactic acid) (PLA) blends with different toughening agents were prepared by melt compounding, and the effects of toughening agents on the toughness of PLA, especially the low-temperature toughness, were investigated. All blends were immiscible systems, but the rheological Cole-Cole diagram showed that the blends had certain compatibility, and the interfacial bonding of PLA/Ethylene/butyl methacrylate/Glycidyl Methacrylate Terpolymer (GEBMA) blend was the best. With addition of the toughening agents, all blends showed improvement of the tensile and impact toughness both at room temperature and low temperature. GEBMA was the best toughening agent, the elongation at break and impact strength at room temperature and low temperature were greatly improved. The elongation at break, tensile strength and impact strength of PLA blend with 20 wt% GEBMA at -20 °C was 55.8 MPa, 195.9% and 18.8 kJ/m2, respectively, which showed the reinforcement and super ductility at low temperature. However, the toughening effect of Poly (propylene carbonate) polyurethane (PPCU) at low temperature was poor. The Tg and interfacial bonding were the main factors affecting the toughness of the blends, especially at low temperature. The lower the Tg and the better the interfacial bonding, the better the toughness of the blends.

Complete chloroplast genome of Saussurea inversa (Asteraceae) and phylogenetic analysis.

Saussurea inversa Raab-Straube is a small perennial and polycarpic herb that is distributed on the rocky slopes of the Qinghai-Tibetan plateau (QTP) at an altitude of 3700-5400 meters. It has a chloroplast genome structure similar to that of other species of Saussurea. It is 152,102 bp in size, including a large single-copy (LSC) region of 83,450 bp, a small single-copy (SSC) region of 18,286 bp and a pair of inverted repeats (IRs) of 25,183 bp. The chloroplast genome of S. inversa encodes 113 genes, containing 80 protein-coding genes (PCGs), 29 tRNA and four rRNA genes. Phylogenetic analysis shows that S. inversa is clustered with S. pseudosimpsoniana and S. laniceps.

Preparation and properties of poly(L-lactic acid) blends with excellent low-temperature toughness by blending acrylic ester based impact resistance agent.

Poly(L-lactic acid) (PLLA) blends with excellent low-temperature toughness and strength were prepared by melt compounding with acrylic ester based impact resistance agent (AEIR). The morphology, thermal properties, mechanical properties and biodegradability of the blends were investigated. Morphology observations revealed the blend was immiscible but had good compatibility with the dispersed phase size of about 200-300 nm. With the addition of AEIR, dramatic improvement in toughness of PLLA was achieved in a wide temperature range, especially at low temperatures the tensile strength was effectively remained. For the blend with 20 wt% AEIR, the tensile strength, elongation at break and impact strength were 51.6 MPa, 72% and 77.1 KJ/m2 at -20 °C, respectively, much greater than that reported. The calculated Tg of AEIR was lower than the test temperatures, and the brittle-tough transition occurred. The PLLA matrix demonstrated obvious shear yielding which induced energy dissipation and therefore lead to excellent toughness of the blends. Moreover, the biodegradation of PLLA was enhanced after blends preparation.

Construction of Bi2O3/CuNiFe LDHs composite and its enhanced photocatalytic degradation of lomefloxacin with persulfate under simulated sunlight.

Advanced oxidation methods based on photocatalysis and sulfate radicals have attached most interest towards contaminant degradation. However, there are a lack of coupling two methods in the field of pollutant degradation. In the present study, a new Bi2O3/CuNiFe LDHs composite was fabricated and it could efficiently activate persulfate (PS) for lomefloxacin (LOM) decomposition under simulated sunlight, in which 84.6% of LOM (10 mg·L-1) was degraded over 40 min with 0.4 g·L-1 of Bi2O3/CuNiFe LDHs composite and 0.74 mM of PS at natural pH. In addition, the Bi2O3/CuNiFe LDHs composite possessed good reusability and stability at least four runs. Moreover, active radical scavenging experiments indicated that hydroxyl radicals (HO·), sulfate radicals (SO4·-), superoxide radicals (O2·-) and hole (h+) were the main radicals under LOM degradation process. Subsequently, the possible degradation intermediates were determined and the decomposition pathways were put forward. At the same time, activated sludge inhibition experiments were performed to assess the variation of toxicity of LOM and its degradation intermediates during oxidation. Finally, possible reaction mechanism of Bi2O3/CuNiFe LDHs composite for PS activation under simulated sunlight was proposed.

The complete chloroplast genome of Saussurea medusa (Asteraceae), a rare subnival plant in Qinghai-Tibetan Plateau.

Saussurea medusa Maxim. is a subnival plant of Asteraceae with abundant medicinal and ecological value. Until now, few studies have been conducted on S. medusa, especially in phylogenetic relationships and species identification. The S. medusa cp genome had a typical quadripartite structure with a conserved genome arrangement. It was 152,500 bp in size, consisting of a large single copy (LSC) region of 83,553 bp and a small single copy (SSC) region of 18,545 bp, separated by a pair of inverted repeats (IRs) of 25,201 bp. It contained 113 unique genes, including 80 protein-coding genes (PCGs), 29 tRNA and four rRNA genes. The overall GC content was 37.67%. Moreover, a phylogenetic analysis, based on 48 complete cp genomes using Maximum Likelihood (ML) method, indicated that S. medusa was relatively closed to S. pseudoleucoma and was well-clustered within genus Saussurea.

Synthesis of silver phosphate/graphene oxide composite and its enhanced visible light photocatalytic mechanism and degradation pathways of tetrabromobisphenol A.

In the present study, silver phosphate/graphene oxide (Ag3PO4/GO) composite was synthesized by ultrasound-precipitation processes. Afterwards, physicochemical properties of the resulting samples were studied through scanning electron microscope, transmission electron microscope, X-ray diffraction, N2 adsorption/desorption, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, surface photovoltage spectroscopy and photoelectrochemical measurements. Results indicated that spherical Ag3PO4 displayed an average diameter of 150 nm and body-centered cubic crystal phase, which was integrated with GO. In addition, the visible light absorbance, charge separation efficiency and lifetime of Ag3PO4 were significantly improved by integration with GO. In addition, Ag3PO4/GO composite was applied to decompose tetrabromosphenol A (TBBPA) in water body. It was found that TBBPA could be completely decomposed within 60 min illumination. Furthermore, several scavenger experiments were conducted to distinguish the contribution of reactive species to the photoctalytic efficiency. Moreover, the enhanced visible light mechanism of Ag3PO4/GO was proposed and discussed. Eventually, several PC decomposition pathways of TBBPA were identified including directly debromination and oxidation, and subsequently further oxidation and hydroxylation processes.

Initiator Systems Effect on Particle Coagulation and Particle Size Distribution in One-Step Emulsion Polymerization of Styrene.

Particle coagulation is a facile approach to produce large-scale polymer latex particles. This approach has been widely used in academic and industrial research owing to its higher polymerization rate and one-step polymerization process. Our work was motivated to control the extent (or time) of particle coagulation. Depending on reaction parameters, particle coagulation is also able to produce narrowly dispersed latex particles. In this study, a series of experiments were performed to investigate the role of the initiator system in determining particle coagulation and particle size distribution. Under the optimal initiation conditions, such as cationic initiator systems or higher reaction temperature, the time of particle coagulation would be advanced to particle nucleation period, leading to the narrowly dispersed polymer latex particles. By using a combination of the Smoluchowski equation and the electrostatic stability theory, the relationship between the particle size distribution and particle coagulation was established: the earlier the particle coagulation, the narrower the particle size distribution, while the larger the extent of particle coagulation, the larger the average particle size. Combined with the results of previous studies, a systematic method controlling the particle size distribution in the presence of particle coagulation was developed.