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Understanding the effects of salinity on bitumen-calcite interactions
No full textRecovery of heavy oil from carbonate oil ores is always a challenge by water-flooding process which is highly dependent on the water chemistry. Herein, experimental tests (by atomic force microscopy (AFM), quartz crystal microbalance with dissipation (QCM-D)) and molecular dynamic (MD) simulation have been conducted to understand the exact role of salinity (cations and anions) in influencing the bitumen-CaCO3 interactions. It is found that the addition of K+ and Ca2+ cations (up to 10 mM) into the solution would decrease the repulsive force strength (range from 20 nm to less than 5 nm), and even converts the repulsion force into adhesion force. However, the SO42- anions are observed to be able to strengthen the bitumen-CaCO3 repulsion force. This is different from that for processing quartz oil sands. In QCM-D measurement, additional ions inhibit the bitumen calcite adsorption behavior but the effect is influenced by the ionic types and strength. Based on the zeta potential measurement and MD simulation, it is found that the Ca2+ cations are more preferred to adsorb on both the CaCO3 surface and bitumen. The adsorbed Ca2+ cations perform as ion bridges linking the oil and CaCO3 surface. Therefore, the accumulation of Ca2+ cations in the solution will deteriorate the oil recovery from carbonate oil reservoirs. However, SO42- anions are more inclined to only adsorb on the CaCO3 surface and prevent the adsorption between bitumen and calcite surface. Therefore, rejecting Ca2+ or increasing SO42- in the low salt water would be helpful for the EOR of carbonate oil reservoir
Construction of compressible Polymer/MXene composite foams for high-performance absorption-dominated electromagnetic shielding with ultra-low reflectivity
No full textThe conductive polymer composite (CPC) foams are always accompanied with obvious reflection of EM waves during electromagnetic interference (EMI) shielding, and the significant reduction of EM reflection via structural design of CPC foams to minimize the secondary EMI pollution is deemed very important. Herein, for preparing designable MXene-based CPC foams with high-efficiency EMI-shielding performance and ultra-low reflectivity, novel MXene-decorated polymer foam beads (MPFBs) were fabricated to serve as building blocks by the assistance of polyaniline (PANI), and CPC foams were constructed by assembling MPFBs into 3D accumulation with MXene networks followed by the encapsulation of polydimethylsiloxane (PDMS), which presented superb EMI SE of similar to 23.5-39.8 dB with only similar to 0.0225-0.0449 vol% MXene (plus similar to 0.02 vol% PANI), along with low R coefficient of similar to 0.20-0.31. By further employing the asymmetric gradient configuration, ultra-low R coefficient of similar to 0.05 was obtained with effective EMI SE of similar to 23 dB at total MXene content of only similar to 0.0225 vol%, which is the lowest R values for effective EMI shields ever reported. In addition, because of their remarkable compressibility, convenient SE regulation of PDMS/MPFB composite foams by mechanical compression was demonstrated, showing a function to switch between inefficient shielding of SE 20 dB. (C) 2020 Elsevier Ltd. All rights reserved
Zr-MOFs loaded on polyurethane foam by polydopamine for enhanced dye adsorption
No full textZirconium-based metal-organic frameworks (Zr-MOFs) have attracted widespread attention due to their high specific surface area, high porosity, abundant metal active sites and excellent hydrothermal stability. However, Zr-MOFs materials are mostly powdery in nature and thus difficult to separate from aqueous media, which limits their application in wastewater treatment. In this study, PDA/Zr-MOFs/PU foam was constructed by growing Zr-MOFs nanoparticles on a dopamine-modified polyurethane foam substrate by in-situ hydrothermal synthesis as an adsorbent for removing dyes from wastewater. The results demonstrated that the polydopamine coating improves the dispersion of the Zr-MOFs nanoparticles on the substrate and enhances the interaction between the Zr-MOFs nanoparticles and the PU foam substrate. As a result, compared with Zr-MOFs/PU foam, the prepared PDA/ZrMOFs/PU foam exhibits higher adsorption capacity for crystal violet (CV) (63.38 mg/g) and rhodamine B (RB) (67.73 mg/g), with maximum adsorption efficiencies of CV and RB of 98.4% (pH=11) and 93.5% (pH=7), respectively, at a concentration of 10 mg/L. The PDA/Zr-MOFs/PU foam can simultaneously remove CV and RB from the mixed solution. Moreover, the PDA/ZrMOFs/PU foam still exhibits high stability and reusability after five cycles. (C) 2020 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
An intelligent T-1-T-2 switchable MRI contrast agent for the non-invasive identification of vulnerable atherosclerotic plaques dagger
No full textUnlike stable atherosclerotic plaques, vulnerable plaques are very likely to cause serious cardio-cerebrovascular diseases. Meanwhile, how to non-invasively identify vulnerable plaques at early stages has been an urgent but challenging problem in clinical practices. Here, we propose a macrophage-targeted and in situ stimuli-triggered T-1-T-2 switchable magnetic resonance imaging (MRI) nanoprobe for the non-invasive diagnosis of vulnerable plaques. Precisely, single-dispersed iron oxide nanoparticles (IONPs) modified with hyaluronic acid (HA), denoted as IONP-HP, show macrophage targetability and T-1 MRI enhancement (r(2)/r(1) = 3.415). Triggered by the low pH environment of macrophage lysosomes, the single-dispersed IONP-HP transforms into a cluster analogue, which exhibits T-2 MRI enhancement (r(2)/r(1) = 13.326). Furthermore, an in vivo switch of T-1-T-2 enhancement modes shows that the vulnerable plaques exhibit strong T-1 enhancement after intravenous administration of the nanoprobe, followed by a switch to T-2 enhancement after 9 h. In contrast, stable plaques show only slight T-1 enhancement but without T-2 enhancement. It is therefore imperative that the intelligent and novel nanoplatform proposed in this study achieves a substantial non-invasive diagnosis of vulnerable plaques by means of a facile but effective T-1-T-2 switchable process, which will significantly contribute to the application of materials science in solving clinical problems
Mimicking Neurotransmitter Activity and Realizing Algebraic Arithmetic on Flexible Protein-Gated Oxide Neuromorphic Transistors
No full textRecently, flexible neuromorphic devices have attracted extensive attention for the construction of perception cognitive systems with the ultimate objective to achieve robust computation, efficient learning, and adaptability to evolutionary changes. In particular, the design of flexible neuromorphic devices with data processing and arithmetic capabilities is highly desirable for wearable cognitive platforms. Here, an albumen-based protein-gated flexible indium tin oxide (ITO) ionotronic neuromorphic transistor was proposed. First, the transistor demonstrates excellent mechanical robustness against bending stress. Moreover, spikeduration-dependent synaptic plasticity and spike-amplitude-dependent synaptic plasticity behaviors are not affected by bending stress. With the unique protonic gating behaviors, neurotransmission processes in biological synapses are emulated, exhibiting three characteristics in neurotransmitter release, including quantal release, stochastic release, and excitatory or inhibitory release. In addition, three types of spike-timing-dependent plasticity learning rules are mimicked on the ITO ionotronic neuromorphic transistor. Most interestingly, algebraic arithmetic operations, including addition, subtraction, multiplication, and division, are implemented on the protein gated neuromorphic transistor for the first time. The present work would open a promising biorealistic avenue to the scientific community to control and design wearable green cognitive platforms, with potential applications including but not limited to intelligent humanoid robots and replacement neuroprosthetics
Highly Efficient Ir-CoOx Hybrid Nanostructures for the Selective Hydrogenation of Furfural to Furfuryl Alcohol
No full textDecoration of noble metals with transition-metal oxides has been intensively studied for heterogeneous catalysis. However, controllable syntheses of metal-metal oxide heterostructures are difficult, and elucidation of such interfaces is still challenging. In this work, supported IrCo alloy nanoparticles are transformed into supported Ir-CoOx close-contact nanostructures by in situ calcination and following selective reduction. Relative to Ir/Al2O3, Ir-CoOx/Al2O3 shows greatly enhanced activities for the hydrogenation of furfural derivatives to the corresponding furfuryl alcohol derivatives with more than 99% selectivity and demonstrates significantly improved activities and selectivity for hydrogenations of alpha,beta-unsaturated aldehydes to alpha,beta-unsaturated alcohols. The modification of Ir surfaces with CoOx prevents Ir nanoparticles from growing, achieving high thermal and catalytic stabilities. Theoretic calculation suggests that the better catalytic performance of Ir-CoOx/Al2O3 is ascribed to the Ir-CoOx interaction, which promotes the absorption of furfural as well as desorption of furfuryl alcohol, resulting in enhanced catalytic activities
A High Performance Copolyester with Locked Biodegradability: Solid Stability and Controlled Degradation Enabled by Acid-Labile Acetal
No full textThe gradual degradation of polyester in daily use causes unpredictable failure and restricts its reliable applications. The realization of excellent stability in use and controlled degradation in a specific environment is highly appreciated but still remains challengeable. Here, we demonstrate a new solution via introducing acetal units into poly(butylene succinate): locking the biodegradation of copolyesters by rigid Spiro diacetal, which could be unlocked in strong acidic circumstances. In detail, a series of poly(butylene succinate-co-spirocyclic succinate) (PBSS) copolyesters containing different contents of spiroglycol (SPG) were prepared and characterized. Among them PBSS65 behaved as an excellent candidate for future application, which possessed a high elastic modulus (1.87 GPa) and tensile strength (46 MPa) and moderate elongation at break (252%). It kept stable after melt processing and pH 0-14 soaking, showing solid reliability in daily use. Its biodegradation was locked by the steric hindrance effect of SPG units. Only after treatment in acetone/H2O mixed acidic solution could the biodegradation be triggered. Moreover, it was found that the prolongation of the acid treatment time could accelerate the biodegradation process. The controlled degradation mechanism was proposed to be consisted of acid cleavage of SPG unit and enzymatic degradation of ester group
High Efficiency Green-Emitting LuAG:Ce Ceramic Phosphors for Laser Diode Lighting
No full textLu3Al5O12:Ce3+ (LuAG:Ce3+) ceramic phosphors (CPs) are regarded as the most promising green color converter and play a key role in high quality white light in the next-generation laser diode (LD) lighting. High efficient LuAG:Ce3+ CPs are still urgent for high luminous efficacy (LE) LD lighting devices. By designing the Ba2+-Si4+ pair to keep charge balance and annealing in air to remove oxygen vacancy defects, the luminescent properties of LuAG:Ce CPs are greatly enhanced. The LE is promoted to 216.9 lm W-1, which is the best performance of LuAG:Ce in LD lighting so far. Strategies for optimizing LuAG:Ce3+ CPs are detailed. It is believed that this work makes a big step and the proposed strategies will inspire more researchers to approach high performance of Al-based garnet CPs and accelerate the development of LD lighting
Ionic liquid-induced graphitization of biochar: N/P dual-doped carbon nanosheets for high-performance lithium/sodium storage
No full textBiomass-derived graphitic carbon is becoming an attractive material for anodes in lithium-ion and sodium-ion batteries (LIBs and SIBs) owing to its sustainability. The graphitization of biochar by heating above 2600 degrees C not only requires high energy consumption but also removes heteroatoms that are conducive to electrochemical energy storage. In this study, graphitic carbon nanosheets with N/P-dual doping are facilely synthesized by one-step carbonization of pine sawdust at 800/ 1000/1200 degrees C that is priorly dissolved in 1-butyl-3-methyl-imidazolium ([Bmim]H2PO4) and used as anodes of LIBs/SIBs, respectively. [Bmim]H2PO4 simultaneously promotes the graphitization and porosities of the biochar as carbonization temperature increases in addition to providing N/Pdual doping. Used as anodes of LIBs, IWC-1200 demonstrates excellent rate performance and cyclic stability, delivering 385 mAh g(-1) at 1 Ag-1 throughout 1000 cycles. For sodium storage, IWC-1000 exhibits stable capacities of 217 mAh g(-1) at 0.1 A g(-1) and 101 mAh g(-1) at 1 Ag-1. The electrochemical performances benefit from the graphitized structure with N/P-dual doping, leading to redox pseudocapacitance for lithium/sodium storage. DFT calculations suggest that pyridinic N strongly attracts both Li and Na while P atoms inside the graphitic structure significantly increase the interlayer spacing. [GRAPHICS]
Intertwined Carbon Nanotubes and Ag Nanowires Constructed by Simple Solution Blending as Sensitive and Stable Chloramphenicol Sensors
No full textChloramphenicol (CAP) is a harmful compound associated with human hematopathy and neuritis, which was widely used as a broad-spectrum antibacterial agent in agriculture and aquaculture. Therefore, it is significant to detect CAP in aquatic environments. In this work, carbon nanotubes/silver nanowires (CNTs/AgNWs) composite electrodes were fabricated as the CAP sensor. Distinguished from in situ growing or chemical bonding noble metal nanomaterials on carbon, this CNTs/AgNWs composite was formed by simple solution blending. It was demonstrated that CNTs and AgNWs both contributed to the redox reaction of CAP in dynamics, and AgNWs was beneficial in thermodynamics as well. The proposed electrochemical sensor displayed a low detection limit of up to 0.08 mu M and broad linear range of 0.1-100 mu M for CAP. In addition, the CNTs/AgNWs electrodes exhibited good performance characteristics of repeatability and reproducibility, and proved suitable for CAP analysis in real water samples