Single‐atom catalysts (SACs) have attracted significant attention due to their superior catalytic activity and selectivity. However, the nature of active sites of SACs under realistic reaction ...conditions is ambiguous. In this work, high loading Pt single atoms on graphitic carbon nitride (g‐C3N4)‐derived N‐doped carbon nanosheets (Pt1/NCNS) is achieved through atomic layer deposition. Operando X‐ray absorption spectroscopy (XAS) is performed on Pt single atoms and nanoparticles (NPs) in both the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). The operando results indicate that the total unoccupied density of states of Pt 5d orbitals of Pt1 atoms is higher than that of Pt NPs under HER condition, and that a stable Pt oxide is formed during ORR on Pt1/NCNS, which may suppress the adsorption and activation of O2. This work unveils the nature of Pt single atoms under realistic HER and ORR conditions, providing a deeper understanding for designing advanced SACs.
Operando X‐ray absorption spectroscopy (XAS) unveils the nature of Pt single atoms under realistic reactions. The total unoccupied density of states of Pt 5d orbitals on Pt1 atoms is higher than that of Pt nanoparticles in a hydrogen evolution reaction, while a stable Pt oxide is formed during an oxygen reduction reaction.
Increased glycolysis is considered as a hallmark of cancer. Yet, cancer cell metabolic reprograming during therapeutic resistance development is under-studied. Here, through high-throughput ...stimulated Raman scattering imaging and single cell analysis, we find that cisplatin-resistant cells exhibit increased fatty acids (FA) uptake, accompanied by decreased glucose uptake and lipogenesis, indicating reprogramming from glucose to FA dependent anabolic and energy metabolism. A metabolic index incorporating glucose derived anabolism and FA uptake correlates linearly to the level of cisplatin resistance in ovarian cancer (OC) cell lines and primary cells. The increased FA uptake facilitates cancer cell survival under cisplatin-induced oxidative stress by enhancing beta-oxidation. Consequently, blocking beta-oxidation by a small molecule inhibitor combined with cisplatin or carboplatin synergistically suppresses OC proliferation in vitro and growth of patient-derived xenografts in vivo. Collectively, these findings support a rapid detection method of cisplatin-resistance at single cell level and a strategy for treating cisplatin-resistant tumors.
•Core–shell magnetic molecularly imprinted polymers nanoparticles for Rhodamine B were prepared.•The Fe3O4@MIPs were characterized using SEM, FT-IR, VSM.•Selectivity of imprinted polymers was studied ...by the binding of Rhodamine B and Rhodamine 6G.•Accessibility/fast adsorption rate/high adsorption capacity/significant selectivity.•Solid-phase extraction and determination of illegal add Rhodamine B in foods.
Core–shell magnetic molecularly imprinted polymers (MIPs) nanoparticles (NPs), in which a Rhodamine B-imprinted layer was coated on Fe3O4 NPs. were synthesized. First, Fe3O4 NPs were prepared by a coprecipitation method. Then, amino-modified Fe3O4 NPs (Fe3O4@SiO2-NH2) was prepared. Finally, the MIPs were coated on the Fe3O4@SiO2-NH2 surface by the copolymerization with functional monomer, acrylamide, using a cross-linking agent, ethylene glycol dimethacrylate; an initiator, azobisisobutyronitrile and a template molecule, Rhodamine B. The Fe3O4@MIPs were characterized using a scanning electron microscope, Fourier transform infrared spectrometer, vibrating sample magnetometer, and re-binding experiments. The Fe3O4@MIPs showed a fast adsorption equilibrium, a highly improved imprinting capacity, and significant selectivity; they could be used as a solid-phase extraction material and detect illegal addition Rhodamine B in food. A method was developed for the selective isolation and enrichment of Rhodamine B in food samples with recoveries in the range 78.47–101.6% and the relative standard deviation was <2%.
Achieving an efficient and stable oxygen evolution reaction (OER) in an acidic or neutral medium is of paramount importance for hydrogen production via proton exchange membrane water electrolysis ...(PEM-WE). Supported iridium-based nanoparticles (NPs) are the state-of-the-art OER catalysts for PEM-WE, but the nonhomogeneous dispersion of these NPs on the support together with their nonuniform sizes usually leads to catalyst migration and agglomeration under strongly corrosive and oxidative OER conditions, eventually causing the loss of active surface area and/or catalytic species and thereby the degradation of OER performance. Here, we design a catalyst comprising surface atomic-step enriched ruthenium–iridium (RuIr) nanocrystals homogeneously dispersed on a metal organic framework (MOF) derived carbon support (RuIr@CoNC), which shows outstanding catalytic performance for OER with high mass activities of 2041, 970 and 205 A gRuIr –1 at an overpotential of 300 mV and can sustain continuous OER electrolysis up to 40, 45, and 90 h at 10 mA cm–2 with minimal degradation in 0.5 M H2SO4 (pH = 0.3), 0.05 M H2SO4 (pH = 1), and PBS (pH = 7.2) electrolytes, respectively. Comprehensive experimental studies and density functional theory (DFT) calculations reveal that the good performance of RuIr@CoNC can be attributed, on one hand, to the presence of abundant atomic steps that maximize the exposure of catalytically active sites and lower the limiting potential of the rate-determining step of OER and, on the other hand, to the strong interaction between RuIr nanocrystals and the CoNC support that endows homogeneous dispersion and firm immobilization of RuIr catalysts on CoNC. The RuIr@CoNC catalysts also show outstanding performance in a single-cell PEM electrolyzer, and their large-quantity synthesis is demonstrated.
This paper introduces a novel five-level nested neutral point piloted (NNPP) converter and analyzes the operating principle of five-level NNPP converter. This paper presents a novel space vector ...pulse width modulation (SVPWM) algorithm based on gh coordinate for five-level NNPP converter. First, the common-mode voltage is reduced by choosing the appropriate redundant switching states. After that, the floating-capacitor voltage balance control strategy is presented. The appropriate switch combinations of each phase are determined by the control requirements of floating-capacitor voltages respectively and the hardware mapping method of the switching states is presented. Furthermore, the neutral-point voltage balance control strategy is presented. In order to balance the dc-link capacitor voltages, the seven-segment switching sequence is selected according to the control requirements of dc-link capacitor voltages and the neutral-point voltage regulatory factor is introduced to regulate the durations of the redundant switching states in a switching cycle. Finally, the validity of the novel SVPWM algorithm with decoupling control strategies of floating-capacitor voltages and dc-link capacitor voltages is verified by the experimental results of five-level NNPP converter under steady-state and dynamic conditions.
The photoanodes with heterojunction behavior could enable the development of solar energy conversion, but their performance largely suffers from the poor charge separation and transport process ...through the multiple interfacial energy levels involved. The question is how to efficiently manipulate these energy levels. Taking the n-Si Schottky photoanode as a prototype, the undesired donor-like interfacial defects and its adverse effects on charge transfer in n-Si/ITO photoanode are well recognized and diminished through the treatment on electronic energy level. The obtained n-Si/TiO x /ITO Schottky junction exhibits a highly efficient charge transport and a barrier height of 0.95 eV, which is close to the theoretical optimum for n-Si/ITO Schottky contact. Then, the holes extraction can be further facilitated through the variation of surface energy level, with the NiOOH coated ITO layer. This is confirmed by a 115% increase in surface photovoltage of the photoanodes. Eventually, an unprecedentedly low onset potential of 0.9 V (vs RHE) is realized for water oxidation among n-Si photoanodes. For the water oxidation reaction, the n-Si/TiO x /ITO/NiOOH photoanode presents a charge separation efficiency up to 100% and an injection efficiency greater than 90% at a wide voltage range. This work identifies the important role of interfacial energetics played in photoelectrochemical conversion.
Resistive switching processes in HfO2
are studied by electron holography and in situ energy‐filtered imaging. The results show that oxygen vacancies are gradually generated in the oxide layer under ...ramped electrical bias, and finally form several conductive channels connecting the two electrodes. It also shows that the switching process occurs at the top interface of the hafnia layer.
Display omitted
•Multidimensional links and spatiotemporal variations in LCA remain unresolved.•Multidimensional, dynamic, and spatialized LCA studies are reviewed.•A new idea of fully coupling BD ...and LCA is proposed, discussed, and prospected.•The BigLCA framework and technical architecture are recommended.•The introduction of BD may render LCA towards scientific decision-making.
Life cycle assessment (LCA) is a method that focuses on measuring indicators and making decisions in the environmental dimension. However, its isolation from economic, social, and other dimensions is difficult to identify the interconnections and interactions between multidimensions; its global and static perspectives fail to capture details of spatiotemporal variations effectively. These challenges limit the application of LCA for actual complex systems with multidimensional interweaving and high spatiotemporal heterogeneity. This necessitates an approach that can well quantify multidimensional links and spatiotemporal variations to close the gap. To this end, we reviewed approximately 150 papers recorded in Web of Science and Scopus databases to present the progress in the integration of LCA with different dimensions, and the development of dynamic and spatialized LCAs, as well as identify key challenges. Based on the literature review, we introduced the implications of big data (BD) for LCA to explore a theory for the coupling of BD and LCA. We specifically proposed a universal methodological framework of big life cycle analysis (BigLCA), including four practices: (1) building a spatiotemporal reference system to represent the study object, (2) developing a spatiotemporal inventory analysis scheme based on a modified multi-flow and multi-node model to calculate and integrate massive data, (3) introducing and combining a multi-layer indicator system and system dynamics model to quantify multidimensional indicators and identify their links, and (4) providing spatiotemporal contribution analysis and iterative sensitivity analysis schemes for scientific interpretation. The approach and framework can facilitate the understanding and discussions of the use of BD in LCA, which provides a new approach to improve the accuracy of indicator measurement and the effectiveness and applicability of decision-making.
Cellulose nanocrystals (CNCs) have been blended into polylactic acid (PLA) to improve the polymer's properties. The dispersion of CNC in the matrix has a strong influence on the properties of the ...nanocomposites. In this study, PLA and CNC were compounded by a reactive extrusion process using dicarbonyl peroxide (DCP) as the free radical initiator. Isothermal and non-isothermal crystallization kinetics of the resulting nanocomposites were investigated to understand the effect of PLA-D-CNC on the crystallization of the materials. Nuclear magnetic resonance and Fourier transform infrared spectroscopy analyses confirmed the grafting of PLA onto CNC via reactive extrusion. The Avrami and Tobin model studies showed that the reactive extrusion product PLA-D-CNC exhibited much higher crystallization rates compared to neat PLA, PLA/CNC (without DCP), and PLA/DCP. The maximum crystallization rate temperature of PLA, PLA/CNC, and PLA/DCP was increased from ~100 to ~110degreesC for PLA-D-CNC. The results showed that CNC promoted PLA nucleation and crystallization at high temperatures under the action of DCP. Specifically, the maximum crystallization rate of PLA-D-CNC was 46 times higher than that of neat PLA. PLA-D-CNC showed a two-stage crystallization process, while the other three samples exhibited mostly single-stage processes. The much-enhanced crystallization of PLA-D-CNC was ascribed to the improved interaction between PLA and PLA-D-CNC and the homogeneous dispersion of CNC.
