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Due to the antioxidant properties of lignin, it has been demonstrated as an active substance for treating oxidation-related and inflammatory diseases. However, how the structural properties of lignin affect its biological activities is still ambiguous. In this study, Kraft lignin from wheat straw (KL-A) was used as the raw material to fractionate into three fractions (e.g., KL-B, KL-C, and KL-D) with different molecular weight by ultrafiltration, which possessed different physicochemical properties. The biocompatibility, in vivo and in vitro scavenging abilities for reactive oxygen species (ROS), and anti-apoptotic abilities of the lignin fractions were evaluated using SW1353 chondrocyte cell lines and were quantitatively fitted to their physicochemical properties. The results showed that lignin fractions with lower molecular weights, lower G/S ratios, and higher non-condensed phenolic OH contents endowed lignin with stronger ROS scavenging ability in vivo and in vitro, but was accompanied by increased cytotoxicity to cells. The half maximal inhibitory concentration (IC50) of KL-A, KL-B, KL-C, and KL-D were separately determined as 44.02, 33.43, 32.41, and 18.40 μg/mL. Furthermore, KL-D, with the lowest molecular weight and highest number of functional groups, showed the best antioxidant ability, while it performed poorly in inhibiting cellular apoptosis of chondrocytes. Compared to KL-D, KL-C with inverse structural properties, performed better in anti-apoptosis of SW1353 cells, which is the optimum lignin as promising active substances to be applied in the treatment of osteoarthritis in biomedical engineering.

Cryo-electron microscopy (cryo-EM) has emerged as a vital tool to reveal the native structure of beam-sensitive biomolecules and materials. Yet high-resolution cryo-EM analysis is still limited by the poorly controlled specimen preparation and urgently demands a robust supporting film material to prepare desirable samples. Here, we developed a bilayer Janus graphene membrane with the top-layer graphene being functionalized to interact with target molecules on the surface, while the bottom layer being kept intact to reinforce its mechanical steadiness. The ultraclean and atomically thin bilayer Janus membrane prepared by our protocol on one hand generates almost no extra noise and on the other hand reduces the specimen motion during cryo-EM imaging, thus allowing the atomic-resolution characterization of surface functional groups. Using such Janus membranes in cryo-EM specimen preparation, we were able to directly image the lithium dendrite and reconstruct macromolecules at near-atomic resolution. Our results demonstrate the bilayer Janus design as a promising supporting material for high-resolution cryo-EM and EM imaging.

Osteoporosis is the most common degenerative orthopedic disease in the elderly. Recently, the therapeutic methods for osteoporosis have shifted towards the regulation of local immunity in bone tissues, which could provide a suitable environment for the positive regulation of bone metabolism, promoting osteogenic differentiation and inhibiting osteoclast differentiation. Our previous work demonstrated that iron oxide nanoparticles (IONPs) could positively regulate bone metabolism in vitro. In this study, we further demonstrated that daily administration of IONPs relieved estrogen deficiency-induced osteoporosis via scavenging reactive oxygen species in vivo. Meanwhile, IONPs promoted the osteogenic differentiation of bone marrow mesenchymal stem cells and inhibited the osteoclast differentiation of monocytes from IONPs treated mice. Besides, alendronate, a clinically used anti-osteoporosis bisphosphate, was employed to precisely deliver the IONPs to the bone tissues and played a synergically therapeutic role. Eventually, we verified the bone targeting ability, therapeutic efficiency, and biocompatibility of the novel bone target iron oxides in ovariectomy-induced osteoporotic mice. By applying BTNPs, the OVX-induced osteoporosis was significantly revised in mice models via the positive regulation of bone metabolism.

Due to its low molecular weight and abundant functional groups, water-soluble lignin (WSL) is considered as a more potent antioxidant than traditional industrial lignin in biofields. However, few studies have been conducted to evaluate its intracellular and endogenous reactive oxygen species (ROS)-scavenging ability, especially for the intervention of ROS-related disease in vivo. In this work, WSL in bamboo autohydrolysate (WSL-BM) and wheat stalk autohydrolysate (WSL-WS) were isolated and characterized to comparably analyze their bioactivities. The composition analysis and NMR characterization showed that both WSL-BM and WSL-WS contained relatively similar components and substructures, but WSL-BM contained higher contents of phenolic OH groups. Both WSL samples exhibited excellent biocompatibility with the concentration below 50 μg/mL, while WSL-BM exhibited superior ROS-scavenging ability and ROS-related ulcerative colitis treatment potential at same concentration. In addition, WSL-BM also showed better performance in ameliorating inflammation and oxidative stress in RAW 264.7 cells and colitis mice by activating Nrf2 and suppressing NFκB signaling, resulting in an overall improvement in both macroscopic and histological parameters. Overall, these results implied that WSL from gramineous biomass can be used as a novel anti-inflammatory and antioxidative agent in the biomedical field.

Lignin–carbohydrate complexes (LCCs) have shown antioxidant ability to scavenge the individual free radicals in vitro, while little work has been carried out to show if the LCCs can efficiently scavenge the intracellular and endogenous reactive oxygen species (ROS), which are the multiple radicals derived from the reduction of molecular oxygen during the metabolism process. In this work, carbohydrate-rich LCCs from bamboo (LCCs–B-B) and poplar (LCCs–B-P) were isolated according to the classical method, and their antioxidant activities were evaluated by scavenging intracellular ROS in RAW 264.7 cells in vitro and endogenous ROS in zebrafish in vivo. Results from composition analysis show that both LCC preparations possess similar contents of carbohydrate (52.2% and 51.2%) and lignin (44.1% and 47.8%). However, NMR analysis revealed that the LCCs–B-B contain 16.1/100C9 LCCs linkages, higher than that in LCCs–B-P (12.3/100C9). Antioxidant assays indicated that LCCs–B-B exhibited better antioxidant activities...

Contamination commonly observed on the graphene surface is detrimental to its excellent properties and strongly hinders its application. It is still a great challenge to produce large-area clean graphene film in a low-cost manner. Herein, we demonstrate a facile and scalable chemical vapor deposition approach to synthesize meter-sized samples of superclean graphene with an average cleanness of 99 %, relying on the weak oxidizing ability of CO to etch away the intrinsic contamination, i.e., amorphous carbon. Remarkably, the elimination of amorphous carbon enables a significant reduction of polymer residues in the transfer of graphene films and the fabrication of graphene-based devices and promises strongly enhanced electrical and optical properties of graphene. The facile synthesis of large-area superclean graphene would open the pathway for both fundamental research and industrial applications of graphene, where a clean surface is highly needed.

Hydrogels, consisting of hydrophilic polymers, can be used as films, scaffolds, nanoparticles and drug carriers. They are one of the hot research topics in material science and tissue engineering and are widely used in the field of biomedical and biological sciences. Researchers are seeking for a type of material that is similar to human tissues and can partially replace human tissues or organs. The hydrogel has brought possibility to solve this problem. It has good biocompatibility and biodegradability. After entering the body, it does not cause immune and toxic reactions. The degradation time can be controlled, and the degradation products are nontoxic and nonimmunogenic; the final metabolites can be excreted outside the body. Owing to the lack of blood vessels and poor migration ability of chondrocytes, the self-healing ability of damaged cartilage is limited. Tissue engineering has brought a new direction for the regeneration of cartilage. Drug carriers and scaffolds made of hydrogels are widely used in cartilage tissue engineering. The present review introduces the natural hydrogels, which are often used for cartilage tissue engineering with respect to synthesis, modification and application methods. The translational potential of this article: This review introduces the natural hydrogels that are often used in cartilage tissue engineering with respect to synthesis, modification and application methods. Furthermore, the essential concepts and recent discoveries were demonstrated to illustrate the achievable goals and the current limitations. In addition, we propose the putative challenges and directions for the use of natural hydrogels in cartilage regeneration. Keywords: Alginate, Chitosan, Collagen, Gelatin, Hyaluronan, Natural hydrogel

Although single-particle cryogenic electron microscopy (cryo-EM) has been applied extensively for elucidating many crucial biological mechanisms at the molecular level, this technique still faces critical challenges, the major one of which is to prepare the high-quality cryo-EM specimen. Aiming to achieve a more reproducible and efficient cryo-EM specimen preparation, novel supporting films including graphene-based two-dimensional materials have been explored in recent years. Here we report a robust and simple method to fabricate EM grids coated with single- or few-layer reduced graphene oxide (RGO) membrane in large batch for high-resolution cryo-EM structural determination. The RGO membrane has decreased interlayer space and enhanced electrical conductivity in comparison to regular graphene oxide (GO) membrane. Moreover, we found that the RGO supporting film exhibited nice particle-absorption ability, thus avoiding the air-water interface problem. More importantly, we found that the RGO supporting film is particularly useful in cryo-EM reconstruction of sub-100 kDa biomolecules at near-atomic resolution, as exemplified by the study of RBD-ACE2 complex and other small protein molecules. We envision that the RGO membranes can be used as a robust graphene-based supporting film in cryo-EM specimen preparation.

Yibo Zhang,1,2,* Yawen Li,3,* Wei Liao,4,* Wenzao Peng,5 Jianghui Qin,2 Dongyang Chen,2 Liming Zheng,2 Wenjin Yan,2 Lan Li,2 Zhirui Guo,3 Peng Wang,2,6 Qing Jiang1,2 1Nanjing Drum Tower Hospital Clinical College of Nanjing Medical University, Nanjing, 210008, People’s Republic of China; 2State Key Laboratory of Pharmaceutical Biotechnology, Department of Sports Medicine and Adult Reconstructive Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, 210008, People’s Republic of China; 3Lab Center, The Second Affiliated Hospital of Nanjing Medical University, Nanjing, 210029, People’s Republic of China; 4Children’s Hospital of Nanjing Medical University, Nanjing, 210008, People’s Republic of China; 5Jiangsu Key Laboratory of Oral Diseases, Department of Periodontics, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing, People’s Republic of China; 6State Key Laboratory of Bioelectronics, Jiangsu Key Laboratory for Biomaterials and Devices, School of Biological Science and Medical Engineering, Southeast University, Nanjing, 210009, People’s Republic of China*These authors contributed equally to this workCorrespondence: Zhirui GuoThe Second Affiliated Hospital, Nanjing Medical University, Jiangsu, 210029, People’s Republic of ChinaEmail zhiruiguo@njmu.edu.cnQing JiangState Key Laboratory of Pharmaceutical Biotechnology, Department of Sports Medicine and Adult Reconstructive Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, No. 321 Zhongshan Road, Nanjing, 210008, People’s Republic of ChinaEmail qingj@nju.edu.cnObjective: Gold nanorods (AuNRs) show great potential for versatile biomedical applications, such as stem cell therapy and bone tissue engineering. However, as an indispensable shape-directing agent for the growth of AuNRs, cetyltrimethylammonium bromide (CTAB) is not optimal for biological studies because it forms a cytotoxic bilayer on the AuNR surface, which interferes with the interactions with biological cells.Methods: Citrate-stabilized AuNRs with various aspect-ratios (Cit-NRI, Cit-NRII, and Cit-NRIII) were prepared by the combination of end-selective etching and poly(sodium 4-styrenesulfonate)-assisted ligand exchange method. Their effects on osteogenic differentiation of the pre-osteoblastic cell line (MC3T3-E1), rat bone marrow mesenchymal stem cells (rBMSCs), and human periodontal ligament progenitor cells (PDLPs) have been investigated. Potential signaling pathway of citrate-stabilized AuNRs-induced osteogenic effects was also investigated.Results: The experimental results showed that citrate-stabilized AuNRs have superior biocompatibility and undergo aspect-ratio-dependent osteogenic differentiation via expression of osteogenic marker genes, alkaline phosphatase (ALP) activity and formation of mineralized nodule. Furthermore, Wnt/β-catenin signaling pathway might provide a potential explanation for the citrate-stabilized AuNRs-mediated osteogenic differentiation.Conclusion: These findings revealed that citrate-stabilized AuNRs with great biocompatibility could regulate the osteogenic differentiation of multiple cell types through Wnt/β-catenin signaling pathway, which promote innovative AuNRs in the field of tissue engineering and other biomedical applications.Keywords: citrate-stabilized, gold nanorods, osteogenic differentiation, multiple cells, Wnt/β-catenin signaling pathway

Lignin-carbohydrate complexes (LCC) arebiomacromolecules that can be obtained from different biomass. Even some works have shown the LCC can efficiently scavenge the intracellular and endogenous reactive oxygen species (ROS), while little work has been carried out to investigate the potential application of LCC for ROS-related treatment in biological filed, especially for the treatment of periprosthetic osteolysis in vivo. In this work, Lignin-rich (LCC-A) and carbohydrate-rich (LCC-B) fractions in wheat straw are isolated and used as the ROS scavenger to promote osteoblast differentiation and inhibit osteoclast differentiation. The chemical composition and structures are characterized by high performance anion exchange chromatography (HPAEC) and nuclear magnetic resonance (NMR) technologies (quantitative 13C NMR and 2D-HSQC NMR), respectively. The results showed LCC-A possesses higher in vitro ROS-scavenging ability than LCC-B (89.8% vs 57.8%) and to inhibit osteoclast differentiation, whereas LCC-B more significantly activates cellular antioxidant activities via the KEAP1-NRF2-ARE pathway (218.5% vs 438.0% in the level of HO-1), thus promoting osteoblast differentiation in an inflammatory environment. Moreover, the therapeutic administration of LCC-A and LCC-B for Ti-particle-induced osteolytic murine calvariae showed both of them positively regulate and restore the bone metabolism, while preventing calvaria impairment. Hence, LCC from wheat straw exhibits efficient bone protective effects, suggesting it may be used as the promising ROS scavenger for clinical treatment of periprosthetic osteolysis.

Lignin-carbohydrate complex (LCC) is the biological macromolecule that has been demonstrated to exert multiple biological functions, including antioxidant, anti-inflammation and anti-tumorigenesis, which support its broad application in the bioengineering field. However, it remains elusive the involvements of LCC in human neurological disorders, especially those with the overproduction of reactive oxygen species (ROS), such as spinocerebellar ataxias (SCAs). In this study, we found a previously undetermined anti-protein aggregation activity of LCC. Initially, two individual LCC preparations and carbohydrate-free lignin were isolated from the water-extracted waste residues of Chionanthus retusus (C. retusus) tender leaves. The chemical compositional analysis revealed that lignin (61.5%) is the predominant constituent in the lignin-rich LCC (LCC-L-CR), whereas the carbohydrate-rich LCC (LCC-C-CR) is mainly composed of carbohydrate (60.9%) with the xylan as the major constituent (42.1%). The NMR structural characterization showed that LCC-L-CR preparation is enriched in benzyl ether linkage, while phenyl glycoside is the predominant type of linkage in LCC-C-CR. Both LCC and lignin preparations showed antioxidant activities as exemplified by their abilities to scavenge free radicals in cultured mammalian cells and ROS in zebrafish. We further demonstrated a pronounced capability of LCC-L-CR in inhibiting the aggregation of expanded Ataxin-3, disease protein of SCA type 3, in human neuronal cells. Taken together, our study highlights the antioxidant and novel anti-protein aggregation activities of the C. retusus tender leaves-derived LCC.

The fast development of high-resolution electron microscopy (EM) demands a background-noise-free substrate to support the specimens, where atomically thin graphene membranes can serve as an ideal candidate. Yet the preparation of robust and ultraclean graphene EM grids remains challenging. Here we present a polymer- and transfer-free direct-etching method for batch fabrication of robust ultraclean graphene grids through membrane tension modulation. Loading samples on such graphene grids enables the detection of single metal atoms and atomic-resolution imaging of the iron core of ferritin molecules at both room- and cryo-temperature. The same kind of hydrophilic graphene grid allows the formation of ultrathin vitrified ice layer embedded most protein particles at the graphene-water interface, which facilitates cryo-EM 3D reconstruction of archaea 20S proteasomes at a record high resolution of ~2.36 Å. Our results demonstrate the significant improvements in image quality using the graphene grids and expand the scope of EM imaging., High-resolution electron microscopy requires robust and noise-free substrates to support the specimens. Here, the authors present a polymer- and transfer-free direct-etching method for fabrication of graphene grids with ultraclean surfaces and demonstrate cryo-EM at record high resolution.

The technique of micro-laser-induced breakdown spectroscopy (μLIBS) usually refers to analyzing the surface of the sample using a compact focused laser beam in the optical microscope range. Compared to conventional laser-induced breakdown spectroscopy (LIBS), it can provide more abundant form, structure, and content information on a smaller, less sample condition. Hence, the application field is very wide. In this paper, the basic status of μLIBS in the selection of laser source and the structure of optical path system is introduced, and its application in metal, semiconductor, animal and plant fields is reviewed. The existing problems and potential development direction is pointed out.

Dust deposition on photovoltaic (PV) modules is related to environmental and weather conditions and results in a reduction in power generation efficiency over time. The effects of films on the transmittance can be obtained by testing sample glasses coated with silicon and fluorine super-hydrophobic films with a spectrophotometer. Red soil particles with a diameter of 25 μm were selected to simulate the process of natural dust deposition on PV module samples, and an incubator of constant temperature and humidity was used to simulate the condensation process. PV module samples were irradiated by a solar simulator after the aforementioned simulation process, and the effects of different amounts of sediment in unit areas on the photovoltaic properties and spectral characteristics were determined. The experimental results indicate that the influence of dust on the power generation efficiency of PV modules coated with fluorine super-hydrophobic film is smaller than that for PV modules coated with silicon super-hydrophobic film and that the super-hydrophobic films can not only greatly reduce the dust accumulation on the surface of PV modules but also increase the generating efficiency.

Flexible/foldable energy storage devices with high gravimetric energy density are highly desired due to the development of wearable electronic equipment. In this work, highly flexible/foldable MnO-based lithium-ion battery anode composed of MnO nanoparticles encapsulated in carbon nanofibers (MnO nanoparticles@CNFs) are fabricated by hydrothermal, electrospinning and subsequently thermal treatment. The freestanding, foldable carbon nanofibers membrane with sufficient void space in carbon nanofibers and containing over 50 wt % of MnO can be directly used as a freestanding anode for LIBs. This hybrid membrane electrode exhibites remarkable reversible capacity (773 mA h g-1 at 0.2 A g−1 after 100 cycles). It also shows outstanding rate capability (407 mA h g-1 at 2 A g−1) and robust long cycling stability with specific capacity (400 mA h g-1 at 1 A g−1 after 500 cycles). This work proposes a simple, low-cost and environmental friendly method for preparing free-standing and binder-free composite membrane electrodes with sufficient buffer space, high loading and remarkable electrochemical properties used in lithium ion batteries.

Gas shales contain a variety of clay-rich materials with multifarious pore networks. Clay-hosted porosity is an essential component and considered to play a crucial role in establishing the original hydrocarbon molecules in place and transport characteristics of the shale gas reservoir. To better understand the petrophysical basis of gas storage and migration mechanisms, we aim to visualize and quantify the nature of the clay-hosted pore networks and across micrometer and nanometer length scales. Core and outcrop samples are provided of various clay-rich shales (Qiongzhusi, Longmaxi, Wufeng, and Shihezi Formation), which are characterized using a synergistic multi-scale multi-dimensional workflow by FIBSEM, TEM, and X-ray micro-tomography (mCT). Clay-hosted pores are observed in three significant modes of occurrence depending on imaging of pores at the 2D-FIBSEM/TEM level. The first pore type is found between clay domains in clay matrix as interparticle pore, with pore size smaller than 1 μm, and includes six subtypes: type a, type b, type c, type d, type e, and type f. The second associated with the admixture belongs to inter-aggregate pore that can be further sub-divided into three classes: type g (organic-clay), type h (pyrite-clay), and type I (organic-pyrite-clay), with pore size above 50 up to 500 nm. The third associated with the clay nanoplatelets is intraparticle pore. The upper pore-size range of such pores is generally less than 1 nm, with most pores being less than 0.4 nm. Using 3D-mCT and 3D-FIBSEM, the data sets were reconstructed, clay structures were segmented and visualized, revealing the well-connected clay-hosted pore networks within the heterogeneous clay matrix and quantitatively computing pore size, pore volume, and porosity at micrometer and nanometer scales. These visual results highlight the significance of clay-hosted pore networks in shale gas reservoirs because they are the dominant controls on the petrophysical properties. The application of this workflow to worldwide clay-rich shale deposits will allow essential insights into estimating porosity and permeability of shale formations and provide insight to the storage and transport of hydrocarbon molecules from shale matrix to predict total gas resources.

A new hierarchical MnO x -based nanorods consisting of interconnected MnO 2 nanosheets grown on carbon-coated MnO nanorod, resembling a unique triple-co-axial heterostructure of MnO 2 @C@MnO, is successfully designed and prepared by a simple and controllable approach involving subsequent hydrothermal reaction, polydopamine-derived carbon coating and chemical deposition processes. Owing to its unique well-designed architecture with the structural characteristics including interconnected MnO 2 nanosheets external wall, self-supported MnO nanorod core, and a high conductivity carbon interlayer sandwiched between them, each component play a critical role for the stable application of this MnO x -based nanocomposite anode toward high-performance lithium-ion batteries. The triple-co-axial MnO 2 @C@MnO nanocomposite shows excellent lithium-storage capabilities with the high reversible specific capacity of 919.2 mA h g −1 at 200 mA g −1 after 100 cycles, good rate performance (387.9 mA h g −1 at 2 A g −1 ) and an outstanding specific capacity (1243.2 mA h g −1 ) at the rate of 1 A g −1 after long-term cycles (900 cycles), making it a promising anode material for high-performance lithium-ion batteries.

Air flooding can be successfully applied in a low-temperature reservoir due to the existence of ferrous ions in formation water. However, few published papers can be found about the mechanism of oxidation of crude oil on condition with Fe2+ at a low temperature, by far. Therefore, in order to reveal the mechanism, some static oxidation experiments are carried out at 30°C in this paper. On condition with Fe2+, the rate of oxygen consumption is increased by 2.3 times as that on condition without Fe2+, and the concentration of O2 in the air is decreased to 7.5% after oxidation. According to the results of the changes in the compositions of the air and the crude oil, not only can Fe2+ accelerate the rate of the oxidation but can also affect the pathway of the oxidation. The experimental results can provide a basis for how to further improve the development effect of air flooding in Ganguyi oilfield and safely make use of air flooding in other low-temperature reservoirs.

Magnesium (Mg) alloys have been promised for biomedical implants in orthopedic field, however, the fast corrosion rate and mode challenge their clinical application. To push Mg alloys materials into practice, a composite coating with biodegradable and high compatible components to improve anticorrosion property of an Mg alloy (i.e., AZ31) is designed and fabricated. The inner layer is micro-nano structured Mg(OH)2 through hydrothermal treatment. Then stearic acid (SA) is introduced to modify Mg(OH)2 for better reducing the gap below a surface-degradation polymer layer of poly(1,3-trimethylene carbonate). Benefited by the SA modification effect, this sandwiched coating avoids corrosive medium penetration via enhancing the adhesion strength at the interface between outer and inner layers. Both in vitro and in vivo tests indicate that the composite coating modified AZ31 perform a better anticorrosion behavior and biocompatibility compared to bare AZ31. Strikingly, a 1.7-fold improvement in volume of newly formed bone is observed surrounding the composite coating modified implant after 12 week implantation. The sandwiched biocompatible coating strategy paves a hopeful way for future translational application of Mg alloys orthopedic materials in clinics.

Graphene exhibits properties of atomic thickness, high transparency, and high carrier mobility, which is highly desirable for a flexible transparent conductive material. However, the electronic properties of large-area chemical vapor deposition grown graphene film suffer from insulated polymer contaminations introduced by the transfer process and the easily cracked nature. Here, we report a preparation method of a transfer-medium-free large-area nanofiber-reinforced graphene (a-PAN/G) film simply by annealing the electrostatically spun polyacrylonitrile (PAN) nanofibers on the graphene film. The film could be free-standing on water and suspended in air with high transparency and enhanced electrical and mechanical properties compared to that of a monolayer graphene film. The flexible transparent a-PAN/G films were demonstrated as active materials for sensitive pressure sensors. The obtained pressure sensors demonstrate high sensitivity (44.5 kPa-1 within 1.2 kPa), low operating voltage (0.01-0.5 V), and excellent stability for 5500 loading-unloading cycles, revealing promising potential applications in wearable electronics.

Conformance control by using the polymer gel is an important stimulation technique of heterogeneous oil reservoirs. After operation of the conformance control, the water channeling of heterogeneous oil reservoirs can be plugged, which can force the follow-up injected water to divert into the area with high oil saturation. Thus, under the action of water injection pressure, the polymer gel is deformed. Because this is a long-term process, the ability to resist the long-term deformation and resist damage of polymer gel is important for the long-term plugging effect. However, there are few reports on the effect of long-term rheological characteristics of the polymer gel on its plugging ability. Therefore, it is of great significance to study the rheological characteristics of the polymer gel under the long-term action of a stress, which can be used to accurately predict the effective period of plugging the water channeling. In this paper, taking the Hook body and the viscous pot as the basic elements, and considering the Maxwell model and the Kelvin model as the basic models, a combined viscoelastic mechanical model of the polymer gel is established, which can be used to simulate the creep deformation of polymer gel. At the rheological damage stage of the polymer gel, the strain is increased exponentially and the mechanical parameters is decayed exponentially with time. By introducing the damage variable, based on the stress - time equivalence principle of polymer materials, the time of creep fracture of the polymer gel can be accurately calculated. Since then, the polymer gel is started to break obviously and lost its ability for plugging. This study can provide an important guidance to optimizing the scheme of conformance control and predicting the validity period.

The influence of the molecular weight (Mw) of hydrolyzed polyacrylamide (HPAM) on the cross-linking reaction of HPAM/Cr3+ and the transportation of HPAM/Cr3+ in microfractures is systematically studied using viscometry, ultraviolet–visible absorption spectrophotometry, and displacement experiment with a visual microfractured model. The results show that a high-Mw HPAM is advantageous to the intramolecular cross-linking reaction of the HPAM/Cr3+ system but disadvantageous to the transportation of the HPAM/Cr3+ system in microfractures. At the intramolecular cross-linking stage, the injection pressure of the HPAM/Cr3+ system in microfractures is almost equal to that of the HPAM solution, which undergoes no change with the degree of the cross-linking reaction. The higher the HPAM Mw, the earlier the intramolecular cross-linking ends (thus, the intermolecular cross-linking reaction of HPAM/Cr3+ occurs earlier, which leads to an earlier increase in the injection pressure of the HPAM/Cr3+ system). Moreover, the...

Carbon-encapsulated nickel nanoparticles (Ni@C) with soft magnetic nickel nanoparticle core and dielectric carbon shell were synthesized by a modified arc-discharge method. The calculated reflection loss (RL) of Ni@C/paraffin composites and the measured RL of Ni@C/silicone coatings were studied at thicknesses of 1–3 mm and Ni@C contents of 40–60 wt%. Ni@C nanoparticles show good microwave absorption properties in 2–18 GHz. The minimum calculated RL is −39.82 dB with 60 wt% Ni@C at 3 mm, and the calculated RL

In the micro-laser-induced breakdown spectroscopy field, when the laser ablated crater on the surface of the sample is less than 10 μm, it is difficult to detect the plasma emission line because of short lifetime of excited plasma, and simultaneous quantitative analysis of multiple elements is rarely reported. In this paper, a picosecond LIBS micro-area analysis scheme is proposed. Compared with the femtosecond laser micro-area analysis system, this scheme is more mature and reliable, and is more beneficial to engineering applications. In addition, in this study, the effect of the number of laser pulses on the crater morphology was studied. It was observed that a certain crater depth would have an enhancement effect on the signal, and by controlling the laser energy, a crater less than the diffraction limit was obtained. Moreover, a multielement simultaneous analysis on a set of molybdenum-copper stainless steel samples containing 40%-70% iron was performed when the ablated crater had an outer diameter of approximately 5 μm and an inner diameter of approximately 3 μm. By accumulating spectral intensity, background removal, and abnormal point processing, the calibration results for the eight elements of Mn, Cr, Ni, Cu, Ti, V, Nb and Al were not less than 0.95 using the basic calibration method. Among them, the calibration results for Ni, Cu, V, Nb, Al elements are all higher than 0.99 and the detection limits of the obtained elements range from 0.04% to 1.8%.

Some porphyry Mo deposits with relatively reduced ore assemblages, characterized by high reduced gases (e.g. CH4) and a lack of magnetite and hematite, are generally considered as the reduced porphyry Mo deposits. Nevertheless, the role of oxygen fugacity (fO2) in controlling Mo enrichment and precipitation of molybdenite in such reduced porphyry Mo deposits is poorly understood. The Suyunhe reduced porphyry Mo deposit with a Mo metal reserve of 0.57Mt at an average grade of 0.05–0.09%, located in the West Junggar terrane in Xinjiang, is associated with Early Permian granitic rocks, which emplaced into the volcano-sedimentary sequences of the Middle Devonian Barluk Formation. In this study, we report that the variation of magmatic fO2, the possible mechanism of Mo enrichment, and the contributions of the reduced gases or matter to molybdenite precipitation. Results indicate that the primitive magma is still oxidized with fO2 > NNO (Ni–NiO oxygen buffer), but it is then reduced due to contamination by the reduced sequences. Furthermore, the decreasing magmatic fO2 does not significantly prevent the enrichment of Mo metals during magmatic evolution. By contrast, the evolved parental magma, characterized by highly differentiated and fluorite-rich, is responsible for improving Mo concentration of melts. Most of reduced gases are derived from decomposition of organic matter occurring in the reduced volcanic sedimentary rocks of Barluk Formation. More importantly, these reduced gases (e.g. CH4) play a role in molybdenite precipitation, which may effectively improve the efficiency of metal precipitation.

Contamination is a major concern in surface and interface technologies. Given that graphene is a 2D monolayer material with an extremely large surface area, surface contamination may seriously degrade its intrinsic properties and strongly hinder its applicability in surface and interfacial regions. However, large-scale and facile treatment methods for producing clean graphene films that preserve its excellent properties have not yet been achieved. Herein, an efficient postgrowth treatment method for selectively removing surface contamination to achieve a large-area superclean graphene surface is reported. The as-obtained superclean graphene, with surface cleanness exceeding 99%, can be transferred to dielectric substrates with significantly reduced polymer residues, yielding ultrahigh carrier mobility of 500 000 cm2 V-1 s-1 and low contact resistance of 118 Ω µm. The successful removal of contamination is enabled by the strong adhesive force of the activated-carbon-based lint roller on graphene contaminants.

Heterostructures based on graphene and other 2D atomic crystals exhibit fascinating properties and intriguing potential in flexible optoelectronics, where graphene films function as transparent electrodes and other building blocks are used as photoactive materials. However, large-scale production of such heterostructures with superior performance is still in early stages. Herein, for the first time, the preparation of a submeter-sized, vertically stacked heterojunction of lead iodide (PbI2 )/graphene on a flexible polyethylene terephthalate (PET) film by vapor deposition of PbI2 on graphene/PET substrate at a temperature lower than 200 °C is demonstrated. This film is subsequently used to fabricate bendable graphene/PbI2 /graphene sandwiched photodetectors, which exhibit high responsivity (45 A W-1 cm-2 ), fast response (35 µs rise, 20 µs decay), and high-resolution imaging capability (1 µm). This study may pave a facile pathway for scalable production of high-performance flexible devices.

Corrugation is a ubiquitous phenomenon for graphene grown on metal substrates by chemical vapor deposition, which greatly affects the electrical, mechanical, and chemical properties. Recent years have witnessed great progress in controlled growth of large graphene single crystals; however, the issue of surface roughness is far from being addressed. Here, the corrugation at the interface of copper (Cu) and graphene, including Cu step bunches (CuSB) and graphene wrinkles, are investigated and ascribed to the anisotropic strain relaxation. It is found that the corrugation is strongly dependent on Cu crystallographic orientations, specifically, the packed density and anisotropic atomic configuration. Dense Cu step bunches are prone to form on loose packed faces due to the instability of surface dynamics. On an anisotropic Cu crystal surface, Cu step bunches and graphene wrinkles are formed in two perpendicular directions to release the anisotropic interfacial stress, as revealed by morphology imaging and vibrational analysis. Cu(111) is a suitable crystal face for growth of ultraflat graphene with roughness as low as 0.20 nm. It is believed the findings will contribute to clarifying the interplay between graphene and Cu crystal faces, and reducing surface roughness of graphene by engineering the crystallographic orientation of Cu substrates.

Composite TiO2/acid leached serpentine tailings (AST) were synthesized through the hydrolysis–deposition method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and surface area measurement (BET). The XRD analysis showed that TiO2 coated on the surface of acid leached serpentine tailings was mixed crystal phases of rutile and anatase, the grain size of which is 10–30 nm. SEM, TEM, and EDS analysis exhibited that nano-TiO2 particles were deposited on the surface and internal cavities of acid leaching serpentine tailings. The XPS and FT-IR analysis demonstrated that the coating process of TiO2 on AST was a physical adsorption process. The large specific surface area, porous structure, and plentiful surface hydroxyl group of TiO2/AST composite resulted in the high adsorption capacity of Cr(VI). The experimental results demonstrated that initial concentration of Cr(VI), the amount of the catalyst, and pH greatly influenced the removal efficiency of Cr(VI). The removal kinetics of Cr(VI) at a relative low initial concentration was fitted well with Langmuir–Hinshelwood kinetics model with R2 value of about unity. The as-prepared composites exhibited strong adsorption and photocatalytic capacity for the removal of Cr(VI), and the possible photocatalytic reduction mechanism was studied. The photodecomposition of Cr(VI) was as high as 95% within 2 h, and the reusability of the photocatalysis was proven.

In this paper, a kind of modified cellulose as a raw material of a water-based gel is studied systematically. Its migration performance is good and its solution is Newtonian fluid in porous medium. And more importantly, a water-based gel is synthesized with modified cellulose, acrylamide, N,N′-methylene-bisacrylamide and persulphate. An appropriate formula of a gel is 0.8 wt% modified cellulose, 2 wt% acrylamide, 0.1 wt% cross-linking agent and 0.05 wt% initiator. The initial viscosity of this gelling solution is 72 mPa s and the gelation time is 15 h at 70 °C. After gelation, it is a strong gel and the elasticity is more outstanding than the viscosity. Its applied range in formation environment is the temperature of 60–90 °C, the salinity of 0–100 g/L and the pH value of 6–9. The experimental results show that the gel system can be better applied to conformance control of the heterogeneity reservoir.