Science China Materials最新文献

Black phosphorus (BP) has been regarded as a promising two-dimensional semiconductor due to its excellent properties including high carrier mobility and widely tunable direct bandgap. Despite extensive interest as well as research progress, the preparation of large-size and high-quality BP single crystal in high throughput still remains challenging. Here, a facile growth of centimeter-sized BP single crystal flakes with dozens of throughput per batch is achieved by using bidirectional vapor transport (BVT) method. High crystal quality is confirmed by structural and spectrum characterizations, with an X-ray diffraction rocking curve peak half-height width of only 0.02°. The as-grown BP single crystal flake with smooth cleavage plane can be easily exfoliated into large scale nanosheets. Field-effect transistors fabricated based on the BP by such approach show excellent performance including reliable carrier mobility up to 1150 cm² V⁻¹ s⁻¹ and on/off current ratio of ~10⁶ at 15 K. This approach is also applicable to various doped-BP, such as As-BP, Se-BP, Te-BP, etc. The ability to grow centimeter-sized BP single crystal flakes in high yield will accelerate the research and applications of BP-based electronics and optoelectronics.

High-temperature stability of organic field-effect transistors (OFETs) is critical to ensure its long-term reliable operation under various environmental conditions. The molecular packing of donor-acceptor (D-A) conjugated polymers is closely related to the electrical performance stability in OFETs. Herein, we choose poly[[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)] as a modal system to reveal the relationship between the molecular stacking and electrical stability in high-temperature environment. The results demonstrate that the films with D-A moieties in alternate stacking have better electrical thermal stability compared to normal donor-donor (D-D) stacking. The D-A stacking configuration alternates donor and acceptor units along the out-of-plane direction, while the D-D stacking involves D-D and A-A stacking separately. The structural transition from D-D to D-A is captured at a treated temperature range of 225–250°C. Owing to the tighter packing arrangement along the π-π and lamellar directions, the electron mobility of the D-A stacked films reaches up to 0.23 cm²/V·s, a 50% increase as compared to the D-D stacking films. Furthermore, the D-A stacked films indicate superior electrical performance stability with mobility retaining 100% at 250°C during high-temperature cycling tests. This result highlights that the manipulation of conjugated polymer closely stacked structures can significantly enhance the thermal stability and durability of semiconductor devices.

Surface modification using biomaterials is crucial for constructing bioactive interfaces that can control cell behavior, regulate biological processes, and interact with specific biomolecules. Tannic acid (TA), a naturally derived polyphenol, is of particular interest due to its ability to complex ions, facilitating the fabrication of coordination networks through self-assembly of TA and metal ions, known as metal-phenolic networks (MPNs). These MPNs can form stable, yet dynamic structures that can be further engineered or tailored for specific therapeutic needs. Synthetic TA-based MPN complexes have been constructed to modify diverse biointerfaces due to their unique physiochemical properties, including universal adhesion, pH responsiveness, controllable size and stiffness, ease of preparation, and excellent biocompatibility, which are highly advantageous for various biological applications, particularly in cell therapy. This review explores the synthesis, properties, and applications of TA-based MPNs in the context of therapeutic cells, including bacteria, yeast, and mammalian cells. Key aspects such as biocompatibility, biodegradability, the ability to modulate cellular environments, and clinical translation are discussed, highlighting the potential of TA-based MPNs to advance cell therapy.

For luminescent materials, negative thermal quenching (NTQ), characterized by an increase in the luminescent intensity with temperature, has a large potential in lighting and display technologies. However, leveraging NTQ in metal halide perovskites is challenging, and the mechanism is not well understood. Herein, by utilizing low-temperature photoluminescence, persistent luminescence and thermoluminescence, the origins of NTQ in CsPbBr₃ microspheres are systematically studied, which pertain to the liberation of carriers from shallow trap states. Experimental and theoretical investigations reveal that the energy of these shallow defect states is approximately 0.135 eV beneath the conduction band. A rapid thermal treatment increases the density of these shallow traps and amplifies the NTQ effect, resulting in an enhancement of room-temperature photoluminescence by more than 60% compared to that at 150 K. The process also reduces the threshold for amplified spontaneous emission to about 45 W/cm². Our findings not only provide a deeper understanding of the NTQ phenomenon in CsPbBr₃ microspheres but also open new avenues for enhancing the performance of perovskite optoelectronic devices through energy state regulation.

The study of high-performance multifunctional electromagnetic materials is one of the inevitable challenges in the field of electromagnetic wave (EMW) absorption. In order to improve the attenuation ability of EMW and broaden the frequency range of absorbing materials, rational design of material structure and interface is an important way to optimize the effective absorption bandwidth (EAB). Therefore, enhanced-interface and strongly polarized CuS/Ti₃C₂T_X composites were successfully synthesized by in-situ etching, sacrificial template and freeze-drying techniques. Its EMW absorption performance was improved by optimizing the hybridization ratio and loading content. The maximum reflection loss of CuS@Ti₃C₂T_X (mass ratio = 5:5) is −54.6 dB and the maximum EAB covering the major of Ku band is 4.72 GHz due to the interface polarization, multiple scattering and dipole polarization. In addition, the electromagnetic interference shielding performance of CuS@Ti₃C₂T_X (mass ratio = 3:7) is up to 23.9 dB. A new heterodimensional structure was developed by the spherical structure and lamellar, which realizes the broadband EMW absorption and electromagnetic protection.

Water loss rate is crucial in evaluating the efficiency of atmospheric water harvesting (AWH) materials. However, most moisture-absorbing salts and gels have fixed heat transfer rates, limiting the development of high-performance AWH materials. Herein, an anisotropic PEG/CS/MF nanocomposite (APCM) with adjustable thermal transfer efficiency is presented. APCM was synthesized using polyethylene glycol (PEG), melamine foam (MF), and chitosan (CS) solution through a freeze orientation method. The resulting material exhibits a stable oriented laminated structure formed by hydrogen bonding between PEG, CS, and MF. This unique structure imparts excellent mechanical properties. APCM’s large lamellar gaps and pore diameters enable rapid absorption of atmospheric water molecules at low temperatures without leakage (61.79 kg m⁻³). The compressible nature of APCM allows for efficient heat transfer at high temperatures, and the release of 80% of absorbed water within 15 min. In a proof-of-concept demonstration using a custom-built AWH device, each cubic meter of APCM achieved three AWH cycles within 24 h, producing over 185 kg of water. Therefore, this innovative design offers a promising solution for enhancing the efficiency of AWH, potentially addressing water scarcity issues in various regions.

The advancement in grazing incidence X-ray scattering (GIWAXS) techniques at synchrotron radiation facilities has significantly deepened our understanding of semiconducting polymers. However, investigation of ultrathin polymer films under tensile conditions poses challenge, primarily due to limitations associated with the lack of suitable sample preparation methods and new stretching devices. This study addresses these limitations by designing and developing an in-situ temperature-controllable stretching sample stage, which enables real-time structural measurements of ultrathin polymer films at Beijing Synchrotron Radiation Facility. In particular, we report, for the first time, in-situ GIWAXS results of representative semiconducting polymer thin films under variable-temperature stretching. This research has overcome the limitations imposed by sample constraints, thus facilitating the achievement of valuable insights into the behavior of ultrathin polymer films under tensile conditions. Distinct changes in the molecular ordering and packing within the polymer thin films as a result of increasing applied strain and temperature have been uncovered. This study promotes future developments in the field, thus enabling the design and optimization of intrinsically stretchable electronic devices and other technologically relevant applications.

Quasi-two dimensional (2D) perovskites have emerged as a promising class of materials due to their remarkable photoluminescence efficiency, which stems from their exceptionally high exciton binding energies. The spatial confinement of excitons within smaller grain sizes could enhance the formation of biexcitons leading to higher radiative recombination efficiency. However, the synthesis of high-quality quasi-2D perovskite thin films with controllable grain sizes remains a challenging task. In this study, we present a facile method for achieving quasi-2D perovskite thin films with controllable grain sizes ranging from 500 to 900 nm. This is accomplished by intermediate phase engineering during the film fabrication process. Our results demonstrate that quasi-2D perovskite films with smaller grain sizes exhibit more efficient bound exciton generation and a reduced stimulated emission threshold down to 15.89 µJ cm⁻². Furthermore, femtosecond transient absorption measurements reveal that the decay time of bound excitons is shorter in quasi-2D perovskites with smaller grain sizes compared to that of those with larger grains at the same pump density, which is 230.5 ps. This observation suggests a more efficient exciton recombination process in the smaller grain size regime. Our findings would offer a promising approach for the development of efficient bound exciton lasers.

The development of highly efficient and low-cost photocatalysts for degradation of organic pollutants become an effective approach for environmental remediation. However, the practical application of traditional powder catalyst in photocatalytic technology is limited due to its low recycling capacity, agglomeration and secondary pollution risk. Herein, a floating Fe-doped TiO₂ and hydrogel (FTH) composite was synthesized for the photodegradation of Rhodamine B via a facile impregnation method. The photodegradation results show that the FTH composite exhibits a higher photocatalytic efficiency with degradation percentage (95.6%) compared with pure TiO₂ (41.2%). The enhanced photocatalytic performance is attributed to its excellent flotation performance, providing a large number of active sites for pollutant degradation, contact with O₂ and photons at the air/water interface. Remarkably, the adsorbed Rhodamine B in FTH can still be removed by exposing to light in the air alone, demonstrating strong recovery ability of the FIH composite catalyst. The floatable hydrogel nanocomposites offer a promising solution for scalable solar-drive degradation of water pollutants, paving the way for sustainable water treatment technologies.