Interlayer Charge Transfer Induced Electrical Behavior Transition in 1D AgI@sSWCNT van der Waals Heterostructures.

The emergence of one-dimensional van der Waals heterostructures (1D vdWHs) opens up potential fields with unique properties, but precise synthesis remains a challenge. The utilization of mixed conductive types of carbon nanotubes as templates has imposed restrictions on the investigation of the electrical behavior and interlayer interaction of 1D vdWHs. In this study, we efficiently encapsulated silver iodide in high-purity semiconducting single-walled carbon nanotubes (sSWCNTs), forming 1D AgI@sSWCNT vdWHs. We characterized the semiconductor-metal transition and increased the carrier concentration of individual AgI@sSWCNTs via sensitive dielectric force microscopy and confirmed the results through electrical device tests. The electrical behavior transition was attributed to an interlayer charge transfer, as demonstrated by Kelvin probe force microscopy. Furthermore, we showed that this method of synthesizing 1D heterostructures can be extended to other metal halides. This work opens the door for the further exploration of the electrical properties of 1D vdWHs.

Interfacial Electron Transfer in PbI2@Single-Walled Carbon Nanotube van der Waals Heterostructures for High-Stability Self-Powered Photodetectors.

Acquiring a deep insight into the electron transfer mechanism and applications of one-dimensional (1D) van der Waals heterostructures (vdWHs) has always been a significant challenge. Herein, through direct observation using aberration-corrected transmission electron microscopy (AC-TEM), we verify the stable formation of a high-quality 1D heterostructure composed of PbI2@single-walled carbon nanotubes (SWCNTs). The phenomenon of electron transfer between PbI2 and SWCNT is elucidated through spectroscopic investigations, including Raman and X-ray photoelectron spectroscopy (XPS). Electrochemical testing indicates the electron transfer and enduring stability of 1D PbI2 within SWCNTs. Moreover, leveraging the aforementioned electron transfer mechanism, we engineer self-powered photodetectors that exhibit exceptional photocurrent and a 3-order-of-magnitude switching ratio. Subsequently, we reveal its unique electron transfer behavior using Kelvin probe force microscopic (KPFM) tests. According to KPFM, the average surface potential of SWCNTs decreases by 80.6 mV after filling. Theoretical calculations illustrate a charge transfer of 0.02 e per unit cell. This work provides an effective strategy for the in-depth investigation and application of electron transfer in 1D vdWHs.

USP14 regulates heme metabolism and ovarian cancer invasion through BACH1 deubiquitination and stabilization.

The deubiquitinating enzyme USP14 has been established as a crucial regulator in various diseases, including tumors, neurodegenerative diseases, and metabolic diseases, through its ability to stabilize its substrate proteins. Our group has utilized proteomic techniques to identify new potential substrate proteins for USP14, however, the underlying signaling pathways regulated by USP14 remain largely unknown. Here, we demonstrate the key role of USP14 in both heme metabolism and tumor invasion by stabilizing the protein BACH1. The cellular oxidative stress response factor NRF2 regulates antioxidant protein expression through binding to the antioxidant response element (ARE). BACH1 can compete with NRF2 for ARE binding, leading to the inhibition of the expression of antioxidant genes, including HMOX-1. Activated NRF2 also inhibits the degradation of BACH1, promoting cancer cell invasion and metastasis. Our findings showed a positive correlation between USP14 expression and NRF2 expression in various cancer tissues from the TCGA database and normal tissues from the GTEx database. Furthermore, activated NRF2 was found to increase USP14 expression in ovarian cancer (OV) cells. The overexpression of USP14 was observed to inhibit HMOX1 expression, while USP14 knockdown had the opposite effect, suggesting a role for USP14 in regulating heme metabolism. The depletion of BACH1 or inhibition of heme oxygenase 1 (coded by HMOX-1) was also found to significantly impair USP14-dependent OV cell invasion. In conclusion, our results highlight the importance of the NRF2-USP14-BACH1 axis in regulating OV cell invasion and heme metabolism, providing evidence for its potential as a therapeutic target in related diseases.

A novel ribociclib derivative WXJ-103 exerts anti-breast cancer effect through CDK4/6.

The triple-negative breast cancer (TNBC) subtype is the most aggressive type of breast cancer with a low survival prognosis and high recurrence rate. There is currently no effective treatment to improve it. In this work, we explored the effect of a synthetic compound named WXJ-103 on several aspects of TNBC biology. The human breast cancer cell lines MDA-MB-231 and MCF-7 were used in the experiments, and the cell viability was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide method, and the cell migration and invasion abilities were detected by wound healing assay and Transwell invasion assay. Cell cycle and apoptosis experiments were analyzed by flow cytometry, and protein levels related to cyclin-dependent kinase (CDK) 4/6-cyclin D-Rb-E2F pathway were analyzed by western blotting. Then, in-vivo experiments were performed to determine the clinical significance and functional role of WXJ-103. The results show that WXJ-103 can inhibit the adhesion, proliferation, migration, and invasion of TNBC cells, and can arrest the cell cycle in G1 phase. The levels of CDK4/6-cyclin D-Rb-E2F pathway-related proteins such as CDK6 and pRb decreased in a dose-dependent manner. Therefore, the antitumor activity of WXJ-103 may depend on the inhibition of CDK4/6-cyclin D1-Rb-E2F pathway. This research shows that WXJ-103 may be a new promising antitumor drug, which can play an antitumor effect on TNBC and provide new ideas for the treatment of TNBC.

Synthesis and biological evaluation of novel aromatic amide derivatives as potential BCR-ABL inhibitors.

BCR-ABL1 kinase is a key driver of the pathophysiology of chronic myeloid leukemia (CML). Current treatments need to broaden the chemical diversity of BCR-ABL1 kinase inhibitors to overcome drug resistance. We designed and synthesized a series of aromatic amide derivatives based on several generations of BCR-ABL1 kinase inhibitors. Biological studies showed that compared with Imatinib, these compounds showed significant proliferation inhibitory activities of HL-60 and K562 in cell activity assay. Compounds 4g and 4j exhibited significant anti-tumor activity against the K562 cells with IC50 values of 6.03 ± 0.49 µM and 5.66 ± 2.06 µM respectively. Compounds 4g and 4j, as potential BCR-ABL1 inhibitors, inhibit the phosphorylation of ABL1 and CRKL in a dose-dependent manner. Therefore, compounds 4g and 4j can be used as a starting point for further optimization.

Increasing coverage of mono-layer graphene grown on hexagonal boron nitride.

Graphene sitting on hexagonal boron nitride (h-BN) always exhibits excellent electrical properties. And the properties of graphene onh-BN are often dominated by its domain size and boundaries. Chemical vapor deposition (CVD) is a promising approach to achieve large size graphene crystal. However, the CVD growth of graphene onh-BN still faces challenges in increasing coverage of monolayer graphene because of a weak control on nucleation and vertical growth. Here, an auxiliary source strategy is adapted to increase the nucleation density of graphene onh-BN and synthesis continuous graphene films. It is found that both silicon carbide and organic polymer e.g. methyl methacrylate can assist the nucleation of graphene, and then increases the coverage of graphene onh-BN. By optimizing the growth temperature, vertical accumulation of graphitic materials can be greatly suppressed. This work provides an effective approach for preparing continuous graphene film onh-BN, and may bring a new sight for the growth of high quality graphene.

Engineering the electronic structure of high performance FeCo bimetallic cathode catalysts for microbial fuel cell application in treating wastewater.

The development of high-performance, strong-durability and low-cost cathode catalysts toward oxygen reduction reaction (ORR) is of great significance for microbial fuel cells (MFCs). In this study, a series of bimetallic catalysts were synthesized by pyrolyzing a mixture of g-C3N4 and Fe, Co-tannic complex with various Fe/Co atomic ratios. The initial Fe/Co atomic ratio (3.5:0.5, 3:1, 2:2, 1:3) could regulate the electronic state, which effectively promoted the intrinsic electrocatalytic ORR activity. The alloy metal particles and metal-Nx sites presented on the catalyst surface. In addition, N-doped carbon interconnected network consisting of graphene-like and bamboo-like carbon nanotube structure derived from g-C3N4 provided more accessible active sites. The resultant Fe3Co1 catalyst calcined at 700 °C (Fe3Co1-700) exhibited high catalytic performance in neutral electrolyte with a half-wave potential of 0.661 V, exceeding that of the commercial Pt/C (0.6 V). As expected, the single chamber microbial fuel cell (SCMFC) with 1 mg/cm2 loading of Fe3Co1-700 catalyst as the cathode catalyst afforded a maximum power density of 1425 mW/m2, which was 10.5% higher than commercial Pt/C catalyst with the same loading (1290 mW/m2) and comparable to the Pt/C catalyst with 2.5 times higher loading ( 1430 mW/m2). Additionally, the Fe3Co1-700 also displayed better long-term stability over 1100 h than the Pt/C. This work provides an effective strategy for regulating the surface electronic state in the bimetallic electro-catalyst.

Iron/iron carbide coupled with S, N co-doped porous carbon as effective oxygen reduction reaction catalyst for microbial fuel cells.

As a novel energy device, microbial fuel cells (MFCs) have attracted much attention for their dual functions of electricity generation and sewage treatment. However, the sluggish oxygen reduction reaction (ORR) kinetic on the cathode have hindered the practical application of MFCs. In this work, metallic organic framework derived carbon framework co-doped by Fe, S, N tri-elements was used as alternative electrocatalyst to the conventional Pt/C cathode catalyst in pH-universal electrolytes. The amount of thiosemicarbazide from 0.3 to 3 g determined the surface chemical property, and therefore the ORR activity of FeSNC catalysts. The sulfur/nitrogen doping and Fe/Fe3C embedded in carbon shell was characterized by X-ray photoelectron spectroscopy and transmission electron microscopy. The synergy of iron salt and thiosemicarbazide contributed to the improvement of nitrogen and sulfur doping. Sulfur atoms were successfully doped into the carbon matrix and formed a certain amount of thiophene- and oxidized-sulfur. The optimal FeSNC-3 catalyst synthesized with 1.5 g of thiosemicarbazide exhibited the highest ORR activity with a positive half wave potential of 0.866 V in alkaline and 0.691 V (vs. Reversible Hydrogen Electrode) in neutral electrolyte, which both outperformed the commercial Pt/C catalyst. However, as the amount of thiosemicarbazide surpassed 1.5 g, the catalytic performance of FeSNC-4 was lowered, and this could be assigned to the decreased defects and low specific surface area. The excellent ORR performance in neutral medium urged FeSNC-3 as good cathode catalyst in single chambered MFC (SCMFC). It showed the highest maximum power density of 2126 ± 100 mW m-2, excellent output stability of 8.14% decline in 550 h, chemical oxygen demand removal of 90.7 ± 1.6% and coulombic efficiency of 12.5 ± 1.1%, all superior to those of benchmark SCMFC-Pt/C (1637 ± 35 mW m-2, 15.4%, 88.9 ± 0.9%, and 10.2 ± 1.1%). These outstanding results were associated to the large specific surface area and synergistic interaction of multiple active sites, like Fe/Fe3C, Fe-N4, pyridinic N, graphite N and thiophene-S.

Enabling Scalable Polymer Electrolyte with Synergetic Ion Conductive Channels via a Two Stage Rheology Tuning UV Polymerization Strategy.

Lithium metal batteries with polyethylene oxide (PEO) electrolytes are considered as one of the ideal candidates for next generation power sources. However, the low ambient operation capability and conventional solvent-based fabrication process of PEO limit their large-scale application. In this work, a comb-like quasi-solid polymer electrolyte (QPE) reinforced with polyethylene glycol terephthalate nonwoven is fabricated. Combining the density functional theory calculation analysis and polymer structure design, optimized and synergized ion conductive channels are established by copolymerization of tetrahydrofurfuryl acrylate and introduction of plasticizer tetramethyl urea. Additionally, a unique two-stage solventless UV polymerization strategy is utilized for rheology tuning and electrolyte fabrication. Compared with the conventional one-step UV process, this strategy is ideally suited for the roll-to-roll continuous coating fabrication process with environmental friendliness. The fabricated QPE exhibits high ionic conductivity of 0.40 mS cm-1 and Li+ transference number (t = 0.77) at room temperature. LiFePO4 //Li batteries are assembled to evaluate battery performance, which deliver excellent discharge capacity (144.9 mAh g-1 at 0.5 C) and cycling stability (with the retention rate 94.5% at 0.5 C after 200 cycles) at room temperature. The results demonstrate that it has high potential for solid-state lithium metal batteries.

Status of medication literacy and its related factors among undergraduate students in Shanxi Province, China: A cross-sectional study.

WHAT IS KNOWN AND OBJECTIVE: Medication safety problem has always been the focus of healthcare providers and public health community scholars. As the backbone of the future society, the mastery of college students' knowledge to use medicine will directly affect the level of medication literacy (ML) of the public in the future. The purpose of this study was to investigate the current ML of college students in Shanxi Province and to identify its related factors. METHODS: A cluster random sampling method was utilized to select 800 college students from 10 universities in Shanxi province as participants from 21 March to 10 April 2020. After quality control, 763 valid questionnaires were collected (effective rate 95.4%). This study applied the ML scale adapted from the 14-item health literacy scale (HLS-14) to estimate ML, which contains functional ML, communicative ML and critical ML dimensions to estimate the ML situation. Then, we used structural equation modelling (SEM) to test the hypothesized relationship among three dimensions of ML, self-evaluated health status and safety medication science popularization activities on campus. RESULTS AND DISCUSSION: The results showed that the reliability and validity of the ML scale were good. The average score of ML level of college students in Shanxi Province was 44 points, and the interquartile range was 40-48 points (full score is 65 points). The proportion of high ML level was estimated at as low as 26.7%. 73.1% participants had an average level, and only 1 participant (0.1%) had a low level of ML. Univariate analysis showed that the ML level was significantly influenced by gender, universities, field of study, academic performance and ethnic group (p < 0.05). SEM showed that functional ML (λ = 0.01) and communicative ML (λ = 0.75) had a direct positive association with critical ML. Meanwhile, the model also had a mediating effect. Functional ML had an indirect positive association with critical ML through the mediating effect of communicative ML (λ = 0.11). In addition, both self-evaluated health status and safety medication science popularization activities on campus had an indirect positive association with critical ML through the mediating effect of functional ML and communicative ML. WHAT IS NEW AND CONCLUSION: The study revealed that the ML of most college students in Shanxi Province was at the average level. Among them, medical college student (including pharmacy, nursing, public health, preventive medicine, basic medicine and clinical medicine students), the Han nationality students (the students of China's majority ethnic group), students of good self-evaluated health status, and students who were more exposed to safety medication science popularization activities had a relatively higher ML level. Moreover, it highlighted the importance of self-evaluated health status and safety medication science popularization activities on campus to ML.

Hydrophobically Associating Polymers Dissolved in Seawater for Enhanced Oil Recovery of Bohai Offshore Oilfields.

As compared to China's overall oil reserves, the reserve share of offshore oilfields is rather significant. However, offshore oilfield circumstances for enhanced oil recovery (EOR) include not just severe temperatures and salinity, but also restricted space on offshore platforms. This harsh oil production environment requires polymers with relatively strong salt resistance, solubility, thickening ability, rapid, superior injection capabilities, and anti-shearing ability. As a result, research into polymers with high viscosity and quick solubility is recognized as critical to meeting the criteria of polymer flooding in offshore oil reservoirs. For the above purposes, a novel hydrophobically associating polymer (HAP) was prepared to be used for polymer flooding of Bohai offshore oilfields. The synthetic procedure was free radical polymerization in aqueous solutions starting at 0 °C, using acrylamide (AM), acrylic acid (AA), 2-acrylamido-2-methylpropane sulfonic acid (AMPS), and poly(ethylene glycol) octadecyl methacrylate (POM) as comonomers. It was discovered that under ideal conditions, the molecular weight of HAP exceeds 2.1 × 107 g⋅mol-1. In a simulated reservoir environment, HAP has substantially greater solubility, thickening property, and salt resistance than conventional polyacrylamide (HPAM), with equivalent molecular weight. Finally, the injectivity and propagation of the two polymers in porous media were investigated. Compared with HPAM, which has a similar molecular weight, HAP solution with the concentration of 0.175% had a much better oil displacement effect in the porous medium, which can enhance oil recovery by 8.8%. These discoveries have the potential to pave the way for chemical EOR in offshore oilfields.

Tuning the Interlayer Interactions of 2D Covalent Organic Frameworks Enables an Ultrastable Platform for Anhydrous Proton Transport.

The development of effective, stable anhydrous proton-conductive materials is vital but challenging. Covalent organic frameworks (COFs) are promising platforms for ion and molecule conduction owing to their pre-designable structures and tailor-made functionalities. However, their poor chemical stability is due to weak interlayer interactions and intrinsic reversibility of linkages. Herein, we present a strategy for enhancing the interlayer interactions of two-dimensional COFs via importing planar, rigid triazine units into the center of C3 -symmetric monomers. The developed triazine-core-based COF (denoted as TPT-COF) possesses a well-defined crystalline structure, ordered nanochannels, and prominent porosity. The proton conductivity was ≈10 times those of non-triazinyl COFs, even reaching up to 1.27×10-2  S cm-1 at 160 °C. Furthermore, the TPT-COF exhibited structural ultrastability, making it an effective proton transport platform with remarkable conductivity and long-term durability.

Enhancement of Mass Transport for Oxygen Reduction Reaction Using Petal-Like Porous Fe-NC Nanosheet.

Nitrogen-coordinated single-atom catalysts (SACs) have emerged as a new frontier for accelerating oxygen reduction reaction (ORR) owing to the optimal atom efficiency and fascinating properties. However, augmenting the full exposure of active sites is a crucial challenge in terms of simultaneously pursuing high metal loading of SACs. Here, petal-like porous carbon nanosheets with densely accessible Fe-N4 moieties (FeNC-D) are constructed by combining the space-confinement of silica and the coordination of diethylenetriaminepentaacetic acid. The resulted FeNC-D catalyst possesses an enhanced mesoporosity and a balanced hydrophobicity/hydrophilicity, which can facilitate mass transport and advance the exposure of inaccessible Fe-N4 sites, resulting in efficient utilization of active sites. By virtue of the petal-like porous architecture with maximized active site density, FeNC-D demonstrates superior ORR performance in a broad pH range. Remarkably, when utilized as the air cathode in Zn-air battery (ZAB) and microbial fuel cell (MFC), the FeNC-D-based device displays a large power density (356 mW cm-2 for ZAB and 1041.3 mW m-2 for MFC) and possesses remarkable stability, substantially outperforming the commercial Pt/C catalyst.

Hollow nitrogen-doped carbon nanospheres as cathode catalysts to enhance oxygen reduction reaction in microbial fuel cells treating wastewater.

Hollow nanospheres play a pivotal role in the electro-catalytic oxygen reduction reaction (ORR), which is a crucial step in microbial fuel cell (MFC) device. Herein, the hollow nitrogen-doped carbon nanospheres (HNCNS) were synthesized with the sacrifice of silica coated carbon nanospheres (CNS@SiO2) as template. HNCNS remarkably enhanced the ORR activity compared to the solid carbon and solid silica spheres. By tuning calcination temperature (800-1100 °C), the surface chemistry properties of HNCNS were effectively regulated. The optimal HNCNS-1000 catalyst which was calcined at 1000 °C exhibited the highest ORR activity in neutral media with the onset potential of 0.255 V and half-wave potential of -0.006 V (vs. Ag/AgCl). Single chamber MFC (SCMFC) assembled with HNCNS-1000 cathode unveiled comparable activity to a conventional Pt/C reference. It showed the highest maximum power density of 1307 ± 26 mW/m2, excellent output stability of 5.8% decline within 680 h, chemical oxygen demand (COD) removal of 94.0 ± 0.3% and coulombic efficiency (CE) of 7.9 ± 0.9%. These excellent results were attributed to a cooperative effect of the optimized surface properties (e.g., structural defects, relative content of pyrrolic nitrogen and specific surface area) and the formation of hollow nanosphere structure. Furthermore, the positive linear relationship of the structural defects and pyrrolic nitrogen species with the maximum power generation in SCMFC were clearly elucidated. This study demonstrated that the cost effective HNCNS-1000 was a promising alternative to commercial Pt/C catalyst for practical application in MFCs treating wastewater. Our result revealed the effectiveness of MFC fabricated with HNCNS-1000 cathode catalyst in terms of power generation and wastewater treatment.

Effects of soil amendments on fractions and stability of soil organic matter in saline-alkaline paddy.

Soil amelioration is an effective practice to alleviate the adverse effects of soil salinization. However, increasing the fertility of salt-affected soils has been challenging, particularly in coastal saline-alkaline paddy soils. Here, we carried out a 45-day incubation experiment to evaluate the impacts of soil amendments on fractions and stability of soil organic matter (SOM) in a saline-alkaline paddy. The experiment simulates the flooding-draining practice and consists of CaCO3, gypsum and biochar amendments using different fertility soils. We measured dissolved organic carbon (DOC) and nitrogen (DON) in supernatant liquids, water-soluble cations, water extractable organic carbon (WEOC) and nitrogen (WEON), and microbial biomass carbon (MBC) and nitrogen (MBN) in soils after the incubation. Results showed that water soluble sodium (Na+) was significantly decreased under all amendments (by 17%-32%), except in high fertility soil. We found a significant decrease in DOC (by 36%-47%) under gypsum treatment, but in DON (by 18%-59%) under biochar treatment. However, there was no significant effect on DOC or DON under CaCO3 treatment. Gypsum treatment led to decreased WEOC content (by 0.067%-5.4%), but increased MBC (by 0.16%-44%) and MBN (by 8.3%-37%) in all soils. Biochar treatment caused a decrease in the ratios of WEOC to soil organic carbon (SOC) and WEON to total nitrogen (TN), and an increase in MBC:SOC and MBN:TN ratios. These results suggest that gypsum and biochar amendments can enhance SOM stability in the saline-alkaline paddy. However, SOM stability was not enhanced under CaCO3 treatment, probably due to the presence of a large amount of Na+ in these soils. Our study highlights that soil amelioration has different effects on soil carbon and nitrogen cycles in the saline-alkaline paddy soils, which is associated with water-logged condition.

Seasonality of soil respiration under gypsum and straw amendments in an arid saline-alkali soil.

Soil respiration (or CO2 production) is often determined by measuring CO2 efflux; however, there are differences between them in saline-alkali soils of arid land. The purpose of this study is to test a hypothesis that CO2 production exceeds efflux in arid saline-alkali soils under organic and gypsum amendments. We conducted a modeling study that was based on a two-year field experiment with four treatments: control, gypsum addition, wheat straw incorporation, and gypsum-straw combination. A diffusion model was forced by soil CO2, temperature and moisture that were continuously recorded at 0, 8 and 15 cm, and calibrated by measured CO2 efflux. We then applied the model to calculate CO2 production and efflux over 2014-2015, and found a strong and similar seasonality in both CO2 production and efflux under all treatments (i.e., highest in summer with one peak in 2014 and two peaks in 2015). Our results showed enhanced CO2 production and efflux over short period following rainfall. There were significantly exponential relationships between CO2 production/efflux and temperature. While straw incorporation significantly increased CO2 production and efflux, straw incorporation combined with gypsum amendment caused a decrease in CO2 production and efflux. CO2 production exceeded CO2 efflux mainly in the first half year, and annual difference was 33-130 g C m-2, with larger differences under gypsum amendment. Our study implies that a portion of respired CO2 is transformed into other forms and stored in saline-alkaline soils in arid land.

In Vitro and In Vivo Activity of 14-O-[(4,6-Diamino-pyrimidine-2-yl) thioacetyl] Mutilin against Methicillin-Resistant Staphylococcus aureus.

Staphylococcus aureus (S. aureus) is a major human pathogen that requires new antibiotics with unique mechanism. A new pleuromutilin derivative, 14-O-[(4,6-Diamino-pyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proved as a potent antibacterial agent using in vitro and in vivo assays. In the present study, DPTM was further in vitro evaluated against methicillin-resistant Staphylococcus aureus (MRSA) isolated from dairy farms and outperformed tiamulin fumarate, a pleuromutilin drug used for veterinary. Moreover, a murine skin wound model caused by MRSA infection was established, and the healing effect of DPTM was investigated. The results showed that DPTM could promote the healing of MRSA skin infection, reduce the bacterial burden of infected skin MRSA and decrease the secretion of IL-6 and TNF-α inflammatory cytokines in plasma. These results provided the basis for further in-depth drug targeted studies of DPTM as a novel antibacterial agent.

Weak localization in graphene sandwiched by aligned h-BN flakes.

Charge carriers in graphene exhibit distinct characteristics from those in other two-dimensional materials because of their chiral nature. Additionally, multiple Dirac cones that emerge in graphene superlattices have been regarded as an interesting point in condensed-matter physics in recent years. Here, we report an investigation of the magneto-conductance in graphene encapsulated on the top and bottom by aligned h-BN. The bottom h-BN is precisely aligned with graphene, while the top h-BN is rotated a very small angle relative to it. Such a heterostructure could spoil the commensurate state existing in precisely aligned graphene while the giant moiré superlattice remains. A clear signature of weak localization and weak anti-localization is observed at multiple Dirac cones. Both the weak (anti)localization and the universal conductance fluctuations exhibit strong dependencies on the carrier density, temperature and channel length. This artificial heterostructure allows one to explore quantum interference in graphene with a wide spectrum of electronic properties.

Enhancing oxygen reduction reaction in air-cathode microbial fuel cells treating wastewater with cobalt and nitrogen co-doped ordered mesoporous carbon as cathode catalysts.

The sluggish oxygen reduction reaction (ORR) on the cathode severely limits the energy conversion efficiency of microbial fuel cells (MFCs). In this study, cobalt and nitrogen co-doped ordered mesoporous carbon (Cox-N-OMC) was prepared by heat-treating a mixture of cobalt nitrate, melamine and ordered mesoporous carbon (OMC). The addition of cobalt nitrate remarkably improved the ORR reactivity, compared to the nitrogen-doped OMC catalyst. By optimizing the dosage of cobalt nitrate (x = 0.6, 0.8 and 1.0 g), the Co0.8-N-OMC catalyst displayed excellent ORR catalytic performances in neutral media with the onset potential of 0.79 V (vs. RHE), half-wave potential of 0.59 V and limiting current density of 5.43 mA/cm2, which was comparable to the commercial Pt/C catalyst (0.86 V, 0.60 V and 4.76 mA/cm2). The high activity of Co0.8-N-OMC catalyst was attributed to the high active surface area, higher total nitrogen amount, and higher relative distribution of graphitic nitrogen and pyrrolic nitrogen species. Furthermore, single chamber microbial fuel cell (SCMFC) with Co0.8-N-OMC cathode exhibited the highest power density of 389 ± 24 mW/m2, chemical oxygen demand (COD) removal of 81.1 ± 2.2% and coulombic efficiency (CE) of 17.2 ± 2.5%. On the other hand, in the Co1.0-N-OMC catalyst, increasing the cobalt dosage from 0.8 to 1.0 g resulted in more oxidized-N species, and the reduced power generation in SCMFC (360 ± 8 mW/m2). The power generated by these catalysts and results of electrochemical evaluation were strongly correlated with the total nitrogen contents on the catalyst surface. This study demonstrated the feasibility of optimizing the dosage of metal to enhance wastewater treatment capacity.

Enhancing oxygen reduction reaction by using metal-free nitrogen-doped carbon black as cathode catalysts in microbial fuel cells treating wastewater.

Microbial fuel cells (MFCs) is promising to combat environmental pollution by converting organic waste to electricity. One critical problem for practical application of MFCs treating wastewater is sluggish oxygen reduction reaction (ORR) on cathode. This study focused on developing novel metal-free cost-effective cathodic catalysts to enhance power generation of MFCs. Specifically, carbon powder (Vulcan XC-72R) was modified with acid treatment and pyrazinamide (as nitrogen precursor), and subsequently pyrolyzed at different temperatures. For CN-X (X = 700-1000 °C) materials, chemical compositions (the doping contents of nitrogen species, oxygen-containing groups, and sulfur-containing groups) were altered with pyrolysis temperature. Linear sweep voltammetry showed that CN-800 exhibited the highest ORR activity, with an onset potential of 0.215 V and a half-wave potential of -0.096 V (vs. Ag/AgCl). Electrochemical measurements clearly presented an enhancement of ORR activity by treating carbon powder with sulfuric acid and nitrogen doping, which was well correlated with voltage output in single chamber MFCs (SCMFCs). On the other hand, for the nitrogen-doped cathode catalysts, the best performance in SCMFCs was directly related with the amount of pyridinic nitrogen species and total nitrogen amount. The MFC operated with CN-800 exhibited a maximum power density of 371 ± 3 mW/m2 with the chemical oxygen demand (COD) removal of 77.2 ± 1.5% and coulombic efficiency (CE) of 8.6 ± 0.3%. Furthermore, the MFC with CN-800 exhibited an excellent stability over longer than 580 h of operation with 1.5% voltage reduction. CN-800 possessed comparable COD removal efficiency to conventional costly Pt/C, and exhibited distinct cost-effectiveness for MFC practical applications in wastewater treatment.