Efficient solar‐to‐hydrogen (STH) energy conversion under ambient conditions (room temperature and atmospheric pressure) is important for pursuing scalable solar hydrogen generation. Modification of ...polymeric carbon nitride (PCN) by conjugated polymers has attracted great attention for improving photocatalytic hydrogen evolution (PHE) performance. However, the limited interfacial junction between PCN and conjugated polymers leads to a low density of free charges, resulting in unsatisfactory PHE activity. Herein, three donor‐π‐acceptor‐structured organic molecules (OMs) with different electron‐donating units (amino, N,N‐diethyl and triphenylamine) and same electron‐accepting unit (benzothiadiazole) are designed to modify PCN to enlarge the interfacial junction. The optimized PHE performance under AM 1.5G simulated sunlight and ambient conditions can maintain as high as 4.63 mmol h−1 g−1 (the highest record among all the reported PCN‐based photocatalysts to the best of the authors knowledge). The improved performance can be partially attributed to the strong visible light harvesting capability of OMs. Specifically, the triphenylamine unit in the formed type II molecule heterojunctions (MHJ) enables efficient charge separation at the interfacial junction, which prolongs the photogenerated electron lifetime for PHE. The designed MHJ photocatalysts show outstanding PHE performance under ambient conditions, which is highly promising for scalable STH conversion.
Type II molecule heterojunctions (MHJ) with large interfacial junctions are obtained by integrating donor‐π‐acceptor‐structured organic molecules with polymeric carbon nitride (PCN). This MHJ delivers superior photocatalytic hydrogen evolution (PHE) performance (4.63 mmol h−1 g−1) under ambient conditions, which is the highest among all reported PCN‐based photocatalysts. The outstanding PHE performance under ambient conditions of the MHJ makes it promising for scalable solar‐to‐hydrogen conversion.
Crystalline carbon nitride (CCN), derived from amorphous polymeric CN, is considered as a new generation of metal‐free photocatalyst because of its high crystallinity. In order to further promote the ...photocatalytic performance of CCN, p‐type MnO nanoparticles are in situ synthesized and merged with n‐type CCN through a one‐pot process to form p–n heterojunction. The formed interfacial electric field between the semiconductors with different work functions efficiently breaks the coulomb interaction between MnO and CCN. The prepared catalysts exhibit drastically increased photocatalytic hydrogen evolution (PHE) activity integrated with oxidation of alkyl and aryl alcohols under irradiation of visible light. In the aqueous solution of benzyl alcohol (BzOH), the hydrogen generation rate over MnO/CCN (39.58 µmol h−1) is nearly 7 times and 37 times that of pure CCN (5.76 µmol h−1) and CN (1.06 µmol h−1), respectively, combining with oxidation of BzOH to benzaldehyde. This work proposes an avenue for in situ construction of a novel 2D material‐based S‐scheme heterojunction and extends its application in solar energy conservation and utilization.
A S‐scheme of MnO‐CCN p–n heterojunction is successfully fabricated by one‐pot calcination process and exhibits high photocatalytic performance in simultaneous utilization of photoexcited electrons for hydrogen evolution and holes for alcohols oxidation.
The sigma (σ)‐hole effect has emerged as a promising tool to construct novel architectures endowed with new properties. A simple yet effective strategy for the generation of monofluoromethyl radicals ...is a continuing challenge within the synthetic community. Fluoromethylphosphonium salts are easily available, air‐ and thermally stable, as well as simple‐to‐handle. Herein, we report the ability of the σ‐hole effect to facilitate the visible‐light‐triggered photolysis of phosphonium iodide salts, a charge‐transfer complex, selectively giving fluoromethyl radicals. The usefulness and versatility of this new protocol are demonstrated through the mono‐, di‐, and trifluoromethylation of a variety of alkenes.
Simple and selective synthesis of fluoromethylated alkenes, heterocycles, enamines and heteroarenes by using the readily available and bench‐stable fluoromethylphosphonium iodide salts is described. Key to this privileged transformation is the formation of a photoactive charge‐transfer complex involving the σ‐hole effect of phosphonium salts.
Recently, very high-energy photons above 100 GeV were reported to be detected from GRB 190114C and GRB 180720B at, respectively, 100-1000 s and 10 hr after the burst. We model the available broadband ...data of both GRBs with the synchrotron plus synchrotron self-Compton (SSC) emission of the afterglow shocks. We find that the sub-TeV emission of GRB 180720B can be interpreted as the SSC emission from afterglow shocks expanding in a constant-density circumburst medium. The SSC emission of GRB 190114C dominates over the synchrotron component from GeV energies at ∼100 s, which can explain the possible hard spectrum of the GeV emission at this time. The extrapolated flux of this SSC component to sub-TeV energies can explain the high-significance detection of GRB 190114C by the MAGIC telescope. The parameter values (such as the circumburst density and shock microphysical parameters) in the modeling are not unusual for both gamma-ray bursts, implying that the detection of sub-TeV photons from these two bursts should be attributed to their large burst energies and low redshifts.
Additive manufacturing (AM), nowadays commonly known as 3D printing, is a revolutionary materials processing technology, particularly suitable for the production of low-volume parts with high shape ...complexities and often with multiple functions. As such, it holds great promise for the fabrication of patient-specific implants. In recent years, remarkable progress has been made in implementing AM in the bio-fabrication field. This paper presents an overview on the state-of-the-art AM technology for bone tissue engineering (BTE) scaffolds, with a particular focus on the AM scaffolds made of metallic biomaterials. It starts with a brief description of architecture design strategies to meet the biological and mechanical property requirements of scaffolds. Then, it summarizes the working principles, advantages and limitations of each of AM methods suitable for creating porous structures and manufacturing scaffolds from powdered materials. It elaborates on the finite-element (FE) analysis applied to predict the mechanical behavior of AM scaffolds, as well as the effect of the architectural design of porous structure on its mechanical properties. The review ends up with the authors' view on the current challenges and further research directions.
Artificial “ionic skin” is of great interest for mimicking the functionality of human skin, such as subtle pressure sensing. However, the development of ionic skin is hindered by the strict ...requirements of device integration and the need for devices with satisfactory performance. Here, a dual‐material printing strategy for ionic skin fabrication to eliminate signal drift and performance degradation during long‐term use is proposed, while endowing the ionic skins with high sensitivity by 3D printing of ionic hydrogel electrodes with microstructures. The ionic skins are fabricated by alternative digital light processing 3D printing of two photocurable precursors: hydrogel and water‐dilutable polyurethane acrylate (WPUA), in which the ionically conductive hydrogel layers serve as soft, transparent electrodes and the electrically insulated WPUA as flexible, transparent dielectric layers. This novel dual‐material printing strategy enables strong chemical bonding between the hydrogel and the WPUA, endowing the device with designed characteristics. The resulting device has high sensitivity, minimal hysteresis, a response time in the millisecond range, and excellent repetition durability for pressure sensing. The results demonstrate the potential of the dual‐material 3D printing strategy as a pathway to realize highly stable and high‐performance ionic skin fabrication to monitor human physiological signals and human–machine interactions.
A dual‐material printing strategy is proposed for ionic skin fabrication to eliminate signal drift and performance degradation during long‐term use, while endowing the ionic skins with high sensitivity, by 3D printing ionic hydrogel electrodes with microstructures.
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