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Organic polyimides have received an ever-growing interest in lithium-ion batteries based on the reversible anion stabilization mechanism of redox-active carbonyl groups due to their high theoretical capacities, resource sustainability, and diverse chain structures. Herein, four linear polyimides with different chain structures were synthesized by a facile and green hydrothermal method. The chain structure-electrochemical performance relationship was explored by regulating active anhydride units and diamine linkers. The incorporation of flexible linkers between redox-active anhydrides results in the facile movement of polyimide chains and the formation of porous networks with abundant active sites. In contrast, rigid aromatic linkers with strong π–π conjugation tend to assemble into the orderly-stacked sheets, enabling the efficient electron transfer. When used as the battery cathode, 1,4,5,8-naphthalenetetracarboxylic dianhydride-based polyimide with a relatively flexible linker delivers the largest specific capacity. Such a polyimide also demonstrates the high cycling stability with a capacity retention up to 52% over 10000 cycles. In contrast, pyromellitic dianhydride-based polyimide with a benzene-enriched linker exhibits the lowest capacity and poor rate capability due to its densely-stacked sheets and limited exposure of active groups. The chain structure-dependent performance relationship of polyimides would offer new insights into the rational design of high-performance organic electrodes for the next-generation batteries.

A Gram-stain-positive, strictly aerobic and rod-shaped bacterium, designated as 3 H-10T, was isolated from a yellow water sample collected from the manufacturing process of strong flavor Chinese baijiu in Yibin region of Sichuan province (PR China). Oval endospores were formed at the subtermini of cells with swollen sporangia. The isolate was able to grow at temperatures of 20–45 °C (optimum growth at 37 °C), at pH 6.0–10.0 (optimum growth at pH 8.0) and in the presence of 0–2 % (w/v) NaCl (optimum growth with 0 % NaCl). Ribose was the major cell-wall sugar, and meso-diaminopimelic acid (meso-DAP) was the diagnostic amino acid. The main polar lipids of 3 H-10T included diphosphatidylglycerol (DPG), phosphatidylglycerol (PG) and phosphatidylethanolamine (PE). MK-7 was predominant menaquinone and iso-C15 : 0 (60.7 %) was the major fatty acid. Comparisons of 16S rRNA gene sequence indicated that 3 H-10T was most closely related to Bacillus mesophilus SA4T (96.30 %), Bacillus ginsengihumi Gsoil 114T (96.27 %) and Bacillus shackletonii LMG 18435T (96.27 %). The average nucleotide identity (ANI) values between strain 3 H-10T and the three type strains mentioned above were 69.56, 70.19 and 70.67 %, respectively. The genomic DNA G+C content was 35.4 mol%. On the basis of its phenotypic, chemotaxonomic and phylogenetic properties, strain 3 H-10T represents a novel species of the genus Bacillus , for which the name Bacillus aquiflavi sp. nov. is proposed. The type strain is Bacillus aquiflavi 3 H-10T (=CICC 24755T=JCM 33703T).

The past decade has witnessed substantial achievements on electrochemical energy storage in employing graphene-based composites; however, of which have been usually produced on a laboratory scale with a limited compatibility with future industrialization. Herein a facile, cheap, and scalable sonochemical method was developed to prepare MnO2/graphene composite electrodes for supercapacitors. Petal-like MnO2 arrays were densely grown on the surface of graphene oxide followed by annealing at 220 °C under an air atmosphere. The as-fabricated MnO2/graphene hierarchical composite electrodes deliver 292.9 and 156.1 F/g at 5 and 100 mV/s, respectively, showing higher specific capacitance and better rate capability compared to the MnO2 electrode. An excellent cyclability with a capacitance retention as high as 91.5% was also achieved for the composite electrodes after running 1000 cycles. Such excellent electrochemical performances are ascribed to the robust composite structure and synergetic contribution from petal-like MnO2 arrays and conductive graphene sheets.

Conventional inorganic electrode materials for lithium-ion batteries (LIBs) face inherent limitations in electrochemical performance, natural resources, environmental issues, mechanical robustness, and cost. Organic redox polymers have recently attracted considerable attention as potential low-cost alternative electrodes for green LIBs; however, they are often employed as cathode materials. Herein a simple one-pot solvothermal polymerization approach was developed to produce graphene/chemically crosslinked poly(methyl methacrylate) (Gr/c-PMMA) composites as robust anodes for high-performance LIBs. As control samples, linear PMMA and pure c-PMMA are also solvothermally polymerized without and with the addition of a crosslinker, respectively, in the absence of graphene oxide. Such thermoplastic PMMA-based materials as anodes for LIBs exhibit a pair of stable redox peaks at 0.79 and 1.02 V over a potential range of 0.01 to 2.5 V, due to their highly reversible lithiation/delithiation of the in situ generated 1,2-cyclopentanedione active units. The reversible capacities of PMMA, c-PMMA, and Gr/c-PMMA anodes are 97, 147, and 206 mA h g−1 at 20 mA g−1, respectively. After increasing to 400 mA g−1, the Gr/c-PMMA anode manifests a capacity retention of 82%, higher than those of c-PMMA (72%) and PMMA (38%) anodes. Moreover, Gr/c-PMMA delivers a high capacity of 159 mA h g−1 after 1000 cycles at 400 mA g−1. Notably, compared to PMMA, the better performance of c-PMMA can be attributable to the chemical crosslinking induced-formation of porous networks consisting of smaller nanoparticles (∼50 nm) for c-PMMA than those of PMMA (∼100 nm). The incorporation of uniformly dispersed graphene into c-PMMA enables the creation of 3D conductive networks with interconnected porous channels, thereby providing the efficient electrochemical activity of Gr/c-PMMA while retaining the structural integrity during cycling. This, in turn, results in a large specific capacity, a high rate capability, and a long-term cycling stability. These findings may provide new insights into the exploration of low-cost commercial plastics for rechargeable batteries as well as the possibility of other high added-value energy applications by capitalizing on recyclable plastics.

Metal compound/graphene composites have been dominantly fabricated by in-situ intercalation of metal-containing precursors into graphene or graphene oxide (GO) followed by chemical and/or thermal treatment. This process usually leads to the formation of 0D oxide nanoparticles/2D graphene composites with the limited improvements in the supercapacitor performance. Herein a facile two-step method was reported to fabricate 3D porous Ni(OH)2/graphene composite hydrogels (NiGH) by incorporating the pre-synthesized 1D Ni(OH)2 nanobelts into a GO suspension followed by the hydrothermal process. The resulted hydrogels show large specific surface area (370.6 m2/g) and can be directly used as the self-supported electrodes. The NiGH electrode exhibits the specific capacitance up to 1738.3 F/g at 10 mV/s and 1701.5 F/g at 1 A/g, retains 1385.0 F/g at 100 mV/s and 1152.0 F/g at 8 A/g, respectively. The capacitance and rate performance of NiGH are far superior to those of Ni(OH)2 (841.2 F/g at 10 mV/s; 592.5 F/g at 1.0 A/g), graphene hydrogel (207.5 F/g at 10 mV/s), and the control Ni(OH)2 nanoparticle/graphene composite powder (NiGP: 1045.8 F/g at 10 mV/s; 950.8 F/g at 1.0 A/g) prepared by the one-pot hydrothermal processing of Ni salt and GO. Meanwhile, the NiGH electrode also shows lower resistance and higher cycling stability (retaining 100.8% of initial capacitance over 5000 cycles at 5 A/g) as compared to Ni(OH)2, graphene hydrogel, and NiGP due to the efficient combination of pseudo-capacitive 1D Ni(OH)2 nanobelts and conductive 2D graphene sheets to create 3D architectures. Such a facile two-step protocol enables the superiority of ultrathin oxide nanobelts to fabricate 3D graphene-based composite hydrogels for high-performance supercapacitor electrodes.

Background Victimization as an inducing factor of depressive symptoms has been confirmed in previous studies. However, little is known about how and when it induces depressive symptoms in adolescents. Methods In total, 1174 Chinese adolescents were recruited to complete the Juvenile Victimization Questionnaire, Security Questionnaire, Positive Psychological Capital Questionnaire, and the Chinese version of the Center for Epidemiologic Studies Depression Scale. Results After controlling for gender and school type, the sense of security partially mediated the association between victimization and depressive symptoms. Moreover, direct association and the mediating effect of the sense of security were moderated by psychological capital. The moderating effect occurred in the second half of the mediating effect. Limitations Causal conclusions cannot be drawn based on cross-sectional research design. All measures were based on participant self-report. Conclusions The mediating model constructed in this study emphasized the important influence of stress, emotion, and psychological diathesis on adolescent depressive symptoms.

A cationic polymerization of 2-thiophenemethanol (ThM) and a sol–gel polycondensation of tetraethylorthosilicate (TEOS) were simultaneously catalyzed by trifluoroacetic acid in a single process step to produce poly(2-thiophenemethanol)/silica (PThM/SiO2) composites. S-Doped mesoporous carbon (S-MC) materials were then achieved by high-temperature carbonization of PThM/SiO2 under an inert atmosphere and subsequent etching off SiO2 in hydrofluoric acid. This in situ crafting process allows us to tailor the porosity of S-MC in the range of 6 to 30 nm. The specific surface area (278–650 m2 g−1) and pore volume (0.15–0.67 cm3 g−1) increase with increasing the feed ratio of TEOS to ThM. Both the specific surface area and pore volume of S-MC are also higher than those of the un-doped mesoporous carbon (MC) materials using furfuryl alcohol as the starting monomer. The S-MC electrodes thus show larger specific capacitance (Cs) values (252 F g−1 at 25 mV s−1 and 125 F g−1 at 0.5 A g−1) compared to the un-doped MC electrode (203 F g−1 at 25 mV s−1 and 110 F g−1 at 0.5 A g−1). The retention of initial Cs for S-MC is 66%, higher than 53% for MC after a 20-fold increase in the scan rate. After 1000 charge/discharge cycles, the Cs retention for S-MC is 97%, also higher than that of MC (93%). As expected, the S-MC electrodes exhibit larger Cs, higher rate performance, and better cycling stability, compared to the MC counterparts and those fabricated in the absence of TEOS by identical experimental processes. Excellent performance can be contributed to the mesoporous morphology in combination with active doping of rich S heteroatoms.

SnO

Practical applications of Li-S batteries require not only high specific capacities and long cycle lifetimes but also high rate performance. We report a rationally designed Li-S cathode, which consists of a freestanding composite thin film assembled from S nanoparticles, reduced graphene oxide (rGO), and a multifunctional additive poly(anthraquinonyl sulfide) (PAQS). The S nanoparticles provide a high initial specific capacity, and the layered and porous rGO structure provides electron and ion transport paths and restricts polysulfide shuttling. PAQS is not only a highly efficient sulfide trapping agent but also an excellent Li(+) conductor, which benefits the battery reaction kinetics at a high rate. The resulting cathode exhibits an initial specific capacity of 1255 mAh g(-1) with a decay rate as low as 0.046% per cycles over 1200 cycles. Importantly, it displays a reversible capacity of 615 mAh g(-1) when discharged at a high rate of 8 C (13.744 A g(-1)).

Multiwalled carbon nanotubes (MWNTs) have been successfully functionalized by free radical addition of 4,4′-azobis(4-cyanopentanol) in aqueous media to generate the terminal-hydroxyl-modified MWNTs (MWNT–OH), followed by surface-initiated in situ ring-opening polymerization of ɛ-caprolactone in 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) to obtain poly(ɛ-caprolactone)-grafted MWNTs (MWNT-g-PCL). Spectroscopic methods in conjunction with electron microscopy clearly revealed that hairy PCL chains were chemically attached to the surface of MWNTs to form core–shell nanostructures with the latter as core and the former as shell. With increasing polymerization time from 2 to 8 h, the amount of the grafted-PCL synthesized in BmimBF4 varies from 30.6 to 62.7 wt%, which is clearly higher than that (41.5 wt%) obtained in 1,2-dichlorobenzene under comparable conditions (8 h). The proposed methodology here uses water and room temperature ionic liquids (RTILs) as the reaction media and promises a green chemical process for functionalizing nanotubes.

Versatile functional groups were covalently attached to the surface of multiwalled carbon nanotubes (MWNTs) by one-step free radical addition of water-soluble azo initiators. The coverage density of functional groups is rationally controlled either by adjusting the feed ratio of azo initiators to MWNTs or by utilizing the starting chemicals of multifunctional groups. TEM observations in conjunction with solubility data imply that the functionalized-MWNTs have much better dispersibility and stability than pristine MWNTs in polar solvents. The attached carboxylic groups were then used as scaffolds to chelate Ag + ions affording Ag/MWNTs nanohybrids in the presence of NaBH 4 reductant. This shows that the reactive groups anchored on MWNTs can be further chemically functionalized. The proposed method might open many new opportunities for the development of high-performance nanomaterials containing CNTs.

Functionalization of multiwalled carbon nanotubes (MWNTs) with biodegradable supramolecular polypseudorotaxanes has been successfully performed by utilizing surface-initiated ring-opening polymerization of e-caprolactone (CL) to yield poly(e-caprolactone)-grafted MWNTs (MWNT-g-PCL), followed by forming inclusion complexes between grafted-PCL chains and α-cyclodextrins (α-CDs) to give α-CD-NTPCL hybrids. There are significant differences in the morphology and solubility of MWNTs before and after introduction of α-CD. Some protuberances are clearly observed for α-CD-NTPCL as compared with MWNT-g-PCL. Furthermore, the host–guest stoichiometry (monomeric unit of CL/α-CD molar ratio) for α-CD-NTPCL is much higher than that of polypseudorotaxanes consisted of linear PCL and α-CDs. This observation can be explained by a combination of several reasons including the steric hindrance of grafted-PCL, the competitive exclusion between adjacent PCL chains toward α-CD, and the addition order of α-CD as well as the host–guest feed ratio. The present methodology may open up a new opportunity toward the application of supramolecular chemistry for the chemical manipulation and processing of CNTs. Moreover, such novel supramolecular hybrids provide an entry to extend the applications of CNTs to medicine and biology fields through embedding the functional polymers and heterogeneous components.

Silica-coated multiwalled carbon nanotubes (MWCNTs) have been prepared by the sol–gel polymerization of tetraethoxysilane (TEOS) in the presence of the acid-oxidized MWCNTs at room temperature, followed by oxidizing the MWCNTs templates at high temperature in air to produce hollow silica nanotubes. The thickness and architectures of silica shell were well controlled by rationally adjusting the concentration of TEOS, and by adding cationic surfactant as a structure-directing agent. These results also give a clear answer to prove the fact that the structures of spherical silica particles can be fully “copied” to the coating shell and the wall of silica nanotubes when prepared by the same method as the synthesis of silica particles in the presence of templates.