Progress in advanced electrospun membranes for CO2 capture: Feedstock, design, and trend.

The emission of large amounts of carbon dioxide has caused serious environmental problems and hindered the construction of a green and low-carbon society. Efficient carbon dioxide capture has become an important means to slow down global climate warming and achieve effective utilization of carbon dioxide. Membranes synthesized by electrospinning technology are becoming promising carbon capture materials due to their unique characteristics. This review describes the features of membranes prepared from available raw materials and presents their application performances in carbon capture. The preparation methods of various types of membrane materials with excellent capture performance are summarized, and the effects of electrospinning parameters on electrospun fibers are systematically analyzed. Furthermore, recommendations and expectations for further development of electrospun membranes for carbon capture applications are given. These works provide important references for an in-depth understanding of the development status of electrospun membranes in the field of carbon capture and for expanding future research.

Strongly Compressed Few-Layered SnSe2 Films Grown on a SrTiO3 Substrate: The Coexistence of Charge Ordering and Enhanced Interfacial Superconductivity.

High pressure has been demonstrated to be a powerful approach of producing novel condensed-matter states, particularly in tuning the superconducting transition temperature (Tc) of the superconductivity in a clean fashion without involving the complexity of chemical doping. However, the challenge of high-pressure experiment hinders further in-depth research for underlying mechanisms. Here, we have successfully synthesized continuous layer-controllable SnSe2 films on SrTiO3 substrate using molecular beam epitaxy. By means of scanning tunneling microscopy/spectroscopy (STM/S) and Raman spectroscopy, we found that the strong compressive strain is intrinsically built in few-layers films, with a largest equivalent pressure up to 23 GPa in the monolayer. Upon this, unusual 2 × 2 charge ordering is induced at the occupied states in the monolayer, accompanied by prominent decrease in the density of states (DOS) near the Fermi energy (EF), resembling the gap states of CDW reported in transition metal dichalcogenide (TMD) materials. Subsequently, the coexistence of charge ordering and the interfacial superconductivity is observed in bilayer films as a result of releasing the compressive strain. In conjunction with spatially resolved spectroscopic study and first-principles calculation, we find that the enhanced interfacial superconductivity with an estimated Tc of 8.3 K is observed only in the 1 × 1 region. Such superconductivity can be ascribed to a combined effect of interfacial charge transfer and compressive strain, which leads to a considerable downshift of the conduction band minimum and an increase in the DOS at EF. Our results provide an attractive platform for further in-depth investigation of compression-induced charge ordering (monolayer) and the interplay between charge ordering and superconductivity (bilayer). Meanwhile, it has opened up a pathway to prepare strongly compressed two-dimensional materials by growing onto a SrTiO3 substrate, which is promising to induce superconductivity with a higher Tc.

Layer-Stacking, Defects, and Robust Superconductivity on the Mo-Terminated Surface of Ultrathin Mo2C Flakes Grown by CVD.

Materials can exhibit exotic properties when they approach the two-dimensional (2D) limit. Because of promising applications in catalysis and energy storage, 2D transition-metal carbides (TMCs) have attracted considerable attention in recent years. Among these TMCs, ultrathin crystalline α-Mo2C flakes have been fabricated by chemical vapor deposition on Cu/Mo bilayer foils, and their 2D superconducting property was revealed by transport measurements. Herein, we studied the ultrathin α-Mo2C flakes by atomic-resolved scanning tunneling microscopy/spectroscopy (STM/S). Strain-related structural modulation and the coexistence of different layer-stacking modes are observed on the Mo-terminated surface of α-Mo2C flakes as well as various lattice defects. Furthermore, an enhanced superconductivity with shorter correlation length was observed by STS technique, and such superconductivity is very robust despite the appearance of the defects. A mechanism of superconducting enhancement is proposed based on the strain-induced strong coupling and the increased disordering originated from lattice defects. Our results provide a comprehensive understanding of the correlations between atomic structure, defects, and enhanced superconductivity of this emerging 2D material.

Protonation enhanced superconductivity in PdTe2.

Electrochemical ionic liquid gating is an effective way to intercalate ions into layered materials and modulate the properties. Here we report an enhanced superconductivity in a topological superconductor candidate PdTe2through electrochemical gating procedure. The superconducting transition temperature was increased to approximately 3.2 K by ionic gating induced protonation at room temperature. Moreover, a further enhanced superconductivity of both superconducting transition temperature and superconducting volume fraction was observed after the gated samples were placed in a glove box for 2 months. This may be caused by the diffusion of protons in the gated single crystals, which is rarely reported in electrochemical ionic liquid gating experiments. Our results further the superconducting study of PdTe2and may reveal a common phenomenon in the electrochemical gating procedure.

Fully Depleted Self-Aligned Heterosandwiched Van Der Waals Photodetectors.

Room-temperature-operating highly sensitive mid-wavelength infrared (MWIR) photodetectors are utilized in a large number of important applications, including night vision, communications, and optical radar. Many previous studies have demonstrated uncooled MWIR photodetectors using 2D narrow-bandgap semiconductors. To date, most of these works have utilized atomically thin flakes, simple van der Waals (vdW) heterostructures, or atomically thin p-n junctions as absorbers, which have difficulty in meeting the requirements for state-of-the-art MWIR photodetectors with a blackbody response. Here, a fully depleted self-aligned MoS2 -BP-MoS2 vdW heterostructure sandwiched between two electrodes is reported. This new type of photodetector exhibits competitive performance, including a high blackbody peak photoresponsivity up to 0.77 A W-1 and low noise-equivalent power of 2.0 × 10-14  W Hz-1/2 , in the MWIR region. A peak specific detectivity of 8.61 × 1010  cm Hz1/2  W-1 under blackbody radiation is achieved at room temperature in the MWIR region. Importantly, the effective detection range of the device is twice that of state-of-the-art MWIR photodetectors. Furthermore, the device presents an ultrafast response of ≈4 µs both in the visible and short-wavelength infrared bands. These results provide an ideal platform for realizing broadband and highly sensitive room-temperature MWIR photodetectors.

Magnetic Doping Induced Superconductivity-to-Incommensurate Density Waves Transition in a 2D Ultrathin Cr-Doped Mo2C Crystal.

In the vicinity of a competing electronic order, superconductivity emerges within a superconducting dome in the phase diagram, which has been demonstrated in unconventional superconductors and transition-metal dichalcogenides (TMDs), suggesting a scenario where fluctuations or a partial melting of a parent order are essential for inducing superconductivity. Here, we present a contrary example, the two-dimensional (2D) superconductivity in transition-metal carbide can be readily turned into charge density wave (CDW) phases via dilute magnetic doping. Low temperature scanning tunneling microscopy/spectroscopy (STM/STS), transport measurements, and density functional theory (DFT) calculations were employed to investigate Cr-doped superconducting Mo2C crystals in the 2D limit. With ultralow Cr doping (2.7 atom %), the superconductivity of Mo2C is heavily suppressed. Strikingly, an incommensurate density wave (IDW) and a related partially opened gap are observed at a temperature above the superconducting regime. The wave vector of IDW agrees well with the calculated Fermi surface nesting vectors. By further increasing the Cr doping level to 9.4 atom %, a stronger IDW with a smaller periodicity and a larger partial gap appear concurrently. The resistance anomaly implies the onset of the CDW phase. Spatial-resolved and temperature-dependent spectroscopy reveals that such CDW phases exist only in a nonsuperconducting regime and could form long-range orders uniformly. The results provide the understanding for the interplay between charge ordered states and superconductivity in 2D transition-metal carbide.

Superhigh Uniform Magnetic Cr Substitution in a 2D Mo2 C Superconductor for a Macroscopic-Scale Kondo Effect.

Substitutional doping provides an effective strategy to tailor the properties of 2D materials, but it remains an open challenge to achieve tunable uniform doping, especially at high doping level. Here, uniform lattice substitution of a 2D Mo2 C superconductor by magnetic Cr atoms with controlled concentration up to ≈46.9 at% by chemical vapor deposition and a specifically designed Cu/Cr/Mo trilayer growth substrate is reported. The concentration of Cr atoms can be easily tuned by simply changing the thickness of the Cr layer, and the samples retain the original structure of 2D Mo2 C even at a very high Cr concentration. The controlled uniform Cr doping enables the tuning of the competition of the 2D superconductor and the Kondo effect across the whole sample. Transport measurements show that with increasing Cr concentration, the superconductivity of the 2D Cr-doped Mo2 C crystals disappears along with the emergence of the Kondo effect, and the Kondo temperature increases monotonously. Using scanning tunneling microscopy/spectroscopy, the mechanism of the doping level effect on the interplay and evolution between superconductivity and the Kondo effect is revealed. This work paves a new way for the synthesis of 2D materials with widely tunable doping levels, and provides new understandings on the interplay between superconductivity and magnetism in the 2D limit.

Nutrient distribution and structure affect the behavior and speciation of arsenic in coastal waters: A case study in southwestern coast of the Laizhou Bay, China.

The effects of nutrient distribution and structure on the behavior and speciation of dissolved inorganic arsenic (DIAs) in coastal waters were analyzed based on the data of 48 surface water samples collected in the southwestern coast of Laizhou Bay and its adjacent rivers (SWLZB). The concentration of DIAs in the SWLZB ranged from 0.016 to 0.099 µmol l-1 and generally decreased from west to south. The inshore waters exhibited higher DIAs level than the open ocean. The As5+/As3+ ratio was significantly positively correlated with the concentration of TDN, NO3-N, PO4-P, DSi, Chl-a and DO. The concentration of DIAs was strongly correlated with the concentration of PO4-P and DSi, suggesting that adsorption/desorption was an important process for regulating the total DIAs concentration. The results indicated that the distribution of nutrients might well be an important environmental factor affecting the speciation and behavior of DIAs in surface water of the SWLZB.

Epitaxial Growth of PbSe Few-Layers on SrTiO3: The Effect of Compressive Strain and Potential Two-Dimensional Topological Crystalline Insulator.

The freestanding PbSe monolayer has been predicted as a candidate of the two-dimensional topological crystalline insulator, which possesses the Dirac-cone-like edge states resided at the edge. Up to now, however, direct experimental evidence of topological PbSe monolayer has not yet been reported. Here, we report the epitaxial growth and scanning tunneling microscopy study of few-layers PbSe islands grown on SrTiO3 substrate. From the investigation of different thickness, we discover the release of compressive strain and the reduction of bandgap as the thickness becomes thick. Following detailed spectroscopic measurements, a signature of Dirac-like edge states is observed at the edge of seventh-layer PbSe. In conjunction with first-principle calculations, we find that compressive-strain-induced buckling adjusts the topological band inversion and eventually leads to a phase transition from nontrivial two-dimensional topological crystalline insulator to trivial insulator, which match well with our experimental observations. Therefore, both theoretical calculations and experimental observations reveal that the strain can effectively affect the property of epitaxial PbSe, meanwhile demonstrate seventh-layer PbSe as a potential candidate of 2D TCI.

Scanning tunneling microscopic observation of enhanced superconductivity in epitaxial Sn islands grown on SrTiO3 substrate.

Recent experimental and theoretical studies of single-layer FeSe film grown on SrTiO3 have revealed interface enhanced superconductivity, which opens up a pathway to promote the superconducting transition temperature. Here, to investigate the role of SrTiO3 substrate in epitaxial superconducting film, we grew a conventional superconductor ß-Sn (bulk Tc ∼ 3.72 K) onto SrTiO3 substrate by molecular beam epitaxy. By employing scanning tunneling microscope and spectroscopic measurements, an enhanced Tc of 8.2 K is found for epitaxial ß-Sn islands, deduced by fitting the temperature dependence of the gap values using the BCS formula. The observed interfacial charge injection and enhanced electron-phonon coupling are responsible for this Tc enhancement. Moreover, the critical field of 8.3 T exhibits a tremendous increase due to the suppression of the vortex formation. Therefore, the coexistence of enhanced superconductivity and high critical field of Sn islands demonstrates a feasible and effective route to improve the superconductivity by growing the islands of conventional superconductors on perovskite-type titanium oxide substrates.