Cell-free synthetic biology emerges as a powerful and flexible enabling technology that can engineer biological parts and systems for life science applications without using living cells. It provides ...simpler and faster engineering solutions with an unprecedented freedom of design in an open environment than cell system. This review focuses on recent developments of cell-free synthetic biology on biological engineering fields at molecular and cellular levels, including protein engineering, metabolic engineering, and artificial cell engineering. In cell-free protein engineering, the direct control of reaction conditions in cell-free system allows for easy synthesis of complex proteins, toxic proteins, membrane proteins, and novel proteins with unnatural amino acids. Cell-free systems offer the ability to design metabolic pathways towards the production of desired products. Buildup of artificial cells based on cell-free systems will improve our understanding of life and use them for environmental and biomedical applications.
Spider silk is one of the most robust natural materials, which has extremely high strength in combination with great toughness and good elasticity. Inspired by spider silk but beyond it, a healable ...and recyclable supramolecular elastomer, possessing superhigh true stress at break (1.21 GPa) and ultrahigh toughness (390.2 MJ m−3), which are, respectively, comparable to and ≈2.4 times higher than those of typical spider silk, is developed. The elastomer has the highest tensile strength (ultimate engineering stress, 75.6 MPa) ever recorded for polymeric elastomers, rendering it the strongest and toughest healable elastomer thus far. The hyper‐robust elastomer exhibits superb crack tolerance with unprecedentedly high fracture energy (215.2 kJ m−2) that even exceeds that of metals and alloys, and superhigh elastic restorability allowing dimensional recovery from elongation over 12 times. These extraordinary mechanical performances mainly originate from the meticulously engineered hydrogen‐bonding segments, consisting of multiple acylsemicarbazide and urethane moieties linked with flexible alicyclic hexatomic spacers. Such hydrogen‐bonding segments, incorporated between extensible polymer chains, aggregate to form geometrically confined hydrogen‐bond arrays resembling those in spider silk. The hydrogen‐bond arrays act as firm but reversible crosslinks and sacrificial bonds for enormous energy dissipation, conferring exceptional mechanical robustness, healability, and recyclability on the elastomer.
Healable and recyclable elastomers with superhigh strength (tensile strength ≈ 75.6 MPa, true stress at break ≈ 1.21 GPa) and ultrahigh toughness (≈390.2 MJ m−3) are reported. The elastomer has unprecedented crack tolerance with fracture energy of 215.2 kJ m−2 that even exceeds that of metals and alloys. The elastomer exhibits superhigh elastic restorability allowing dimensional recovery from elongation over 12 times.
Transition metal oxides (TMOs)‐based anode materials of high theoretical capacities have been intensively studied for lithium‐ion storage. However, their poor high‐rate capability and cycling ...stability remain to be effectively resolved. Herein, a novel ion exchange (IE)‐assisted indirect carbon coating strategy is proposed to realize high performance freestanding TMO‐based anodes for flexible lithium‐ion batteries (FLIBs). This approach effectively avoids the possible side reaction of oxide reduction, enhances degrees of graphitization of the carbon coating, and preserves advantageous nanostructure of the starting template, leading to enhanced electrical conductivities, alleviated volume variation induced structural instability, fast lithium‐ion diffusion pathways and enhanced electron transfer kinetics. As a proof of concept, IE‐prepared carbon coated NiO nanosheet arrays with excellent structural and electrochemical stability are developed as freestanding anodes for LIBs and FLIBs, which exhibit outstanding electrochemical performances superior to most state‐of‐the‐art NiO‐based anodes reported in recent years. The product anode delivers a high areal capacity (3.08 mAh cm−2 at 0.25 mA cm−2), outstanding high‐rate capability (1.78 mAh cm−2 at 8 mA cm−2) and excellent cycling stability (over 300 cycles). Further pouch cell tests confirm the excellent flexibility of the freestanding electrode against mechanical deformation with well‐maintained electrochemical performance under folding.
An ion exchange‐assisted fabrication of carbon‐coated transition metal oxides (TMOs) strategy is developed for construction of carbon coated TMOs based flexible anodes. The developed synthetic route simultaneously achieves excellent graphitization of the carbon coating and bypasses the harmful reduction of TMOs at high temperatures. The robust carbon coating alleviates the Li+ insertion induced volume fluctuation, securing the excellent cycling stability of the electrodes.
Nitrogen‐doped carbon materials (N‐Cmat) are emerging as low‐cost metal‐free electrocatalysts for the electrochemical CO2 reduction reaction (CO2RR), although the activities are still unsatisfactory ...and the genuine active site is still under debate. We demonstrate that the CO2RR to CO preferentially takes place on pyridinic N rather than pyrrolic N using phthalocyanine (Pc) and porphyrin with well‐defined N‐Cmat configurations as molecular model catalysts. Systematic experiments and theoretic calculations further reveal that the CO2RR performance on pyridinic N can be significantly boosted by electronic modulation from in‐situ‐generated metallic Co nanoparticles. By introducing Co nanoparticles, Co@Pc/C can achieve a Faradaic efficiency of 84 % and CO current density of 28 mA cm−2 at −0.9 V, which are 18 and 47 times higher than Pc/C without Co, respectively. These findings provide new insights into the CO2RR on N‐Cmat, which may guide the exploration of cost‐effective electrocatalysts for efficient CO2 reduction.
Nitrogen‐doped carbon catalysts are presented for application in the electrochemical CO2 reduction reaction (CO2RR). Molecular probes were designed to clarify the genuine catalytically active sites. CO2RR takes place preferentially on pyridinic rather than pyrrolic nitrogen, and metallic cobalt nanoparticles enhance the CO2RR on pyridinic nitrogen significantly.
A newly designed water‐stable NH2‐MIL‐88B(Fe2Ni)‐metal–organic framework (MOF), in situ grown on the surface of a highly conducting 3D macroporous nickel foam (NF), termed NFN‐MOF/NF, is demonstrated ...to be a highly efficient bifunctional electrocatalyst for overall water splitting with ultrastability at high current densities. The NFN‐MOF/NF achieves ultralow overpotentials of 240 and 87 mV at current density of 10 mA cm−2 for the oxygen evolution reaction and hydrogen evolution reaction, respectively, in 1 m KOH. For the overall water splitting, it requires only an ultralow cell voltage of 1.56 V to reach the current density of 10 mA cm−2, outperforming the pairing of Pt/C on NF as the cathode and IrO2 on NF as the anode at the same catalyst loading. The stability of the NFN‐MOF/NF catalyst is also outstanding, exhibiting only a minor chronopotentiometric decay of 7.8% at 500 mA cm−2 after 30 h. The success of the present NFN‐MOF/NF catalyst is attributed to the abundant active centers, the bimetallic clusters {Fe2Ni(µ3‐O)(COO)6(H2O)3}, in the MOF, the positive coupling effect between Ni and Fe metal ions in the MOF, and synergistic effect between the MOF and NF.
A metal–organic framework (MOF) based composite electrocatalyst is developed, not only retaining the unique advantageous properties but also removing the detrimental disadvantage of MOFs. The newly designed water‐stable NH2‐MIL‐88B(Fe2Ni)‐MOF, in situ grown on the surface of a highly conducting 3D macroporous nickel foam, is demonstrated to be a highly efficient bifunctional electrocatalyst for overall water splitting with ultrastability at high current densities.
Quercetin is a bioactive compound that is widely used in botanical medicine and traditional Chinese medicine due to its potent antioxidant activity. In recent years, antioxidant activities of ...quercetin have been studied extensively, including its effects on glutathione (GSH), enzymatic activity, signal transduction pathways, and reactive oxygen species (ROS) caused by environmental and toxicological factors. Chemical studies on quercetin have mainly focused on the antioxidant activity of its metal ion complexes and complex ions. In this review, we highlight the recent advances in the antioxidant activities, chemical research, and medicinal application of quercetin.
Majorana bound states often occur at the end of a 1D topological superconductor. Validated by a new bulk invariant and an intuitive edge argument, we show the emergence of one Majorana Kramers pair ...at each corner of a square-shaped 2D topological insulator proximitized by an s_{±}-wave (e.g., Fe-based) superconductor. We obtain a phase diagram that addresses the relaxation of crystal symmetry and edge orientation. We propose two experimental realizations in candidate materials. Our scheme offers a higher-order and higher-temperature route for exploring non-Abelian quasiparticles.
Practical electrochemical water splitting requires cost‐effective electrodes capable of steadily working at high output, leading to the challenges for efficient and stable electrodes for the oxygen ...evolution reaction (OER). Herein, by simply using conductive FeS microsheet arrays vertically pre‐grown on iron foam (FeS/IF) as both substrate and source to in situ form vertically aligned NiFe(OH)x nanosheets arrays, a hierarchical electrode with a nano/micro sheet‐on‐sheet structure (NiFe(OH)x/FeS/IF) can be readily achieved to meet the requirements. Such hierarchical electrode architecture with a superhydrophilic surface also allows for prompt gas release even at high output. As a result, NiFe(OH)x/FeS/IF exhibits superior OER activity with an overpotential of 245 mV at 50 mA cm−2 and can steadily output 1000 mA cm−2 at a low overpotential of 332 mV. The water‐alkali electrolyzer using NiFe(OH)x/FeS/IF as the anode can deliver 10 mA cm−2 at 1.50 V and steadily operate at 300 mA cm−2 with a small cell voltage for 70 h. Furthermore, a solar‐driven electrolyzer using the developed electrode demonstrates an exceptionally high solar‐to‐hydrogen efficiency of 18.6%. Such performance together with low‐cost Fe‐based materials and facile mass production suggest the present strategy may open up opportunities for rationally designing hierarchical electrocatalysts for practical water splitting or diverse applications.
A 3D hierarchical NiFe(OH)x/FeS/IF electrode with a nano/micro sheet‐on‐sheet structure exhibits superior oxygen evolution reaction activity and durability with a low overpotential of 261 mV at 100 mA cm−2 and 332 mV at 1000 mA cm−2. The water‐alkali electrolyzer, using it as an anode, achieves stable overall water splitting at 300 mA cm−2 with a small cell voltage.
Motivated by recent experiments probing anomalous surface states of Dirac semimetals (DSMs) Na₃Bi and Cd₃As₂, we raise the question posed in the title. We find that, in marked contrast to Weyl ...semimetals, the gapless surface states of DSMs are not topologically protected in general, except on time-reversal-invariant planes of surface Brillouin zone. We first demonstrate this finding in a minimal four-band model with a pair of Dirac nodes at k = (0,0, ± Q), where gapless states on the side surfaces are protected only near kz
= 0. We then validate our conclusions about the absence of a topological invariant protecting double Fermi arcs in DSMs, using a K-theory analysis for space groups of Na₃Bi and Cd₃As₂. Generically, the arcs deform into a Fermi pocket, similar to the surface states of a topological insulator, and this pocket can merge into the projection of bulk Dirac Fermi surfaces as the chemical potential is varied. We make sharp predictions for the doping dependence of the surface states of a DSM that can be tested by angle-resolved photoemission spectroscopy and quantum oscillation experiments.
Lithium metal (LM) is a promising anode material for next generation lithium ion based electrochemical energy storage devices. Critical issues of unstable solid electrolyte interphases (SEIs) and ...dendrite growth however still impede its practical applications. Herein, a composite gel polymer electrolyte (GPE), formed through in situ polymerization of pentaerythritol tetraacrylate with fumed silica fillers, is developed to achieve high performance lithium metal batteries (LMBs). As evidenced theoretically and experimentally, the presence of SiO2 not only accelerates Li+ transport but also regulates Li+ solvation sheath structures, thus facilitating fast kinetics and formation of stable LiF‐rich interphase and achieving uniform Li depositions to suppress Li dendrite growth. The composite GPE‐based Li||Cu half‐cells and Li||Li symmetrical cells display high Coulombic efficiency (CE) of 90.3% after 450 cycles and maintain stability over 960 h at 3 mA cm−2 and 3 mAh cm−2, respectively. In addition, Li||LiFePO4 full‐cells with a LM anode of limited Li supply of 4 mAh cm−2 achieve capacity retention of 68.5% after 700 cycles at 0.5 C (1 C = 170 mA g−1). Especially, when further applied in anode‐free LMBs, the carbon cloth||LiFePO4 full‐cell exhibits excellent cycling stability with an average CE of 99.94% and capacity retention of 90.3% at the 160th cycle at 0.5 C.
A composite gel electrolyte, composed of a liquid electrolyte trapped in a polymer pentaerythritol tetraacrylate‐SiO2 matrix, formed in situ in the cell, is developed for high performance lithium metal batteries (LMBs). The introduction of the inorganic filler, SiO2, promotes Li+ transport and formation of Li+ solvation sheath structures of anionic aggregate domination and thus stable inorganic‐rich solid electrolyte interphase and cathode electrolyte interphase, leading to much improved electrochemical performances of the LMB.
PDF
