Single atom catalysts (SACs) with the maximized metal atom efficiency have sparked great attention. However, it is challenging to obtain SACs with high metal loading, high catalytic activity, and ...good stability. Herein, we demonstrate a new strategy to develop a highly active and stable Ag single atom in carbon nitride (Ag‐N2C2/CN) catalyst with a unique coordination. The Ag atomic dispersion and Ag‐N2C2 configuration have been identified by aberration‐correction high‐angle‐annular‐dark‐field scanning transmission electron microscopy (AC‐HAADF‐STEM) and extended X‐ray absorption. Experiments and DFT calculations further verify that Ag‐N2C2 can reduce the H2 evolution barrier, expand the light absorption range, and improve the charge transfer of CN. As a result, the Ag‐N2C2/CN catalyst exhibits much better H2 evolution activity than the N‐coordinated Ag single atom in CN (Ag‐N4/CN), and is even superior to the Pt nanoparticle‐loaded CN (PtNP/CN). This work provides a new idea for the design and synthesis of SACs with novel configurations and excellent catalytic activity and durability.
A new Ag single atom in carbon nitride (Ag‐N2C2/CN) photocatalyst with Ag‐N2C2 configuration is developed. It affords fast charge transfer, high Ag loading, and good stability. Noteworthily, the Ag‐N2C2/CN exhibits much better hydrogen evolution activity than Ag‐N4/CN, and even superior to the platinum‐loaded CN.
Compared to efficient green and near‐infrared light‐emitting diodes (LEDs), less progress has been made on deep‐blue perovskite LEDs. They suffer from inefficient domain various number of PbX6− ...layers (n) control, resulting in a series of unfavorable issues such as unstable color, multipeak profile, and poor fluorescence yield. Here, a strategy involving a delicate spacer modulation for quasi‐2D perovskite films via an introduction of aromatic polyamine molecules into the perovskite precursor is reported. With low‐dimensional component engineering, the n1 domain, which shows nonradiative recombination and retarded exciton transfer, is significantly suppressed. Also, the n3 domain, which represents the population of emission species, is remarkably increased. The optimized quasi‐2D perovskite film presents blue emission from the n3 domain (peak at 465 nm) with a photoluminescence quantum yield (PLQY) as high as 77%. It enables the corresponding perovskite LEDs to deliver stable deep‐blue emission (CIE (0.145, 0.05)) with an external quantum efficiency (EQE) of 2.6%. The findings in this work provide further understanding on the structural and emission properties of quasi‐2D perovskites, which pave a new route to design deep‐blue‐emissive perovskite materials.
A quasi‐two‐dimensional perovskite film with stable domain distribution is prepared based on a new spacer. The film containing pure bromide perovskite exhibits enhanced deep‐blue fluorescence with quantum yield of 77% by low‐dimensional component engineering. As a result, the corresponding light‐emitting diodes deliver stable deep‐blue emission with a peak external quantum efficiency of 2.6%.
Conspectus Lanthanide-doped upconversion nanoparticles (UCNPs) are a special class of luminescent nanomaterials that convert multiwavelength near-infrared (NIR) excitation into tunable emissions ...spanning the deep ultraviolet (UV) to NIR regions. In addition to large anti-Stokes shift, UCNPs also feature a sharp emission bandwidth, long excited-state lifetime, as well as high resistance to optical blinking and photobleaching. Therefore, UCNPs have been identified as promising candidates to solve many challenging problems in fields ranging from biological imaging and therapeutics to photovoltaics and photonics. Nevertheless, the progress of utilizing an upconversion process is being hindered by the limited emission intensity, principally due to low oscillator strength in these nanoparticles. UCNPs essentially resemble the optical characteristics of their bulk counterparts, which take advantage of electronic transition within the 4f configuration of the lanthanide dopants to realize photon energy conversions. In general, a high dopant concentration promotes upconversion luminescence by providing a high density of optical centers to collect and to sustain the energy of the excitation light. However, an increase in dopant concentration induces self-quenching processes that offset the emission gain and may eventually result in attenuation of the overall emission intensity. This phenomenon known as concentration quenching represents a major obstacle to constructing bright UCNPs. In recent years, advances in nanoparticle research have led to the emergence of several strategies for mitigating energy loss at elevated dopant concentrations. In consequence, doping high levels of lanthanide ions in UCNPs has become a viable solution to boosting the emission intensity of photon upconversion. On account of extensive energy exchange interaction in heavily doped UCNPs, the spectrum tunability of photon upconversion is also greatly enhanced. These advances have largely expanded the scope of upconversion research. To provide guidelines for enhancing upconversion through heavy doping, we attempt to review recent advances in the understanding and control of concentration quenching in UCNPs. With significant advancements made in the chemical synthesis, we are now able to exquisitely control the doping of lanthanide ions in various nanoparticles of well-defined size, morphology, and core–shell structure. We show that, by confining energy transfer in nanostructured host materials in conjunction with innovative excitation schemes, concentration quenching of upconversion luminescence is largely alleviated. As a result, unusually high dopant concentrations can be used to construct UCNPs displaying high brightness and large anti-Stokes shift. We demonstrate that the development of heavily doped UCNPs enables advanced bioimaging and photonic applications that can hardly be fulfilled by conventional UCNPs comprising low concentrations of lanthanide dopants.
Polyethylene glycol (PEG) is a flexible, hydrophilic simple polymer that is physically attached to peptides, proteins, nucleic acids, liposomes, and nanoparticles to reduce renal clearance, block ...antibody and protein binding sites, and enhance the half-life and efficacy of therapeutic molecules. Some naïve individuals have pre-existing antibodies that can bind to PEG, and some PEG-modified compounds induce additional antibodies against PEG, which can adversely impact drug efficacy and safety. Here we provide a framework to better understand PEG immunogenicity and how antibodies against PEG affect pegylated drug and nanoparticles. Analysis of published studies reveals rules for predicting accelerated blood clearance of pegylated medicine and therapeutic liposomes. Experimental studies of anti-PEG antibody binding to different forms, sizes, and immobilization states of PEG are also provided. The widespread use of SARS-CoV-2 RNA vaccines that incorporate PEG in lipid nanoparticles make understanding possible effects of anti-PEG antibodies on pegylated medicines even more critical.
•The effect of sodium triphosphate on the thermodynamic property and setting time for magnesium phosphate were studied.•The exothermic and mechanical properties for MPC prepared with different types ...of phosphate salts were investigated.•Hydration products for MPC system are analyzed by using X-ray diffraction and scanning electron microscopy.
Magnesium phosphate cement (MPC) was prepared with dead burned magnesia oxide and phosphate salts, such as ammonium dihydrogen phosphate (NH4H2PO4) and potassium dihydrogen phosphate (KH2PO4). The properties of MPC prepared with varied phosphate salts were of much difference. In this paper the exothermia kinetics, mechanical properties and phase compositions of MPC prepared by mixing MgO with either ammonium dihydrogen phosphate or potassium dihydrogen phosphate, or a combination of both were studied. Besides, the effects of sodium triphosphate (Na5P3O10) on the microstructure and mechanical properties of MPC were also investigated. The results revealed that MPC prepared with ammonium dihydrogen phosphate exhibited substantially higher early strength and hydration temperature than that of magnesium potassium phosphate, while the later demonstrated better strength development. The strength of MPC prepared with equivalent mixture of ammonium dihydrogen phosphate and potassium dihydrogen phosphate was higher than that of MPC containing magnesium ammonium phosphate or magnesium potassium phosphate only. Moreover, the testing presented that the addition of sodium triphosphate improved the mechanical properties of MPC significantly. It also prolongs the setting time. Finally, the reaction products and their micro-morphology of MPC paste were examined and analyzed by X-ray diffraction (XRD) and Scanning Electronic Microscopic (SEM).
Identifying influential nodes in very large-scale directed networks is a big challenge relevant to disparate applications, such as accelerating information propagation, controlling rumors and ...diseases, designing search engines, and understanding hierarchical organization of social and biological networks. Known methods range from node centralities, such as degree, closeness and betweenness, to diffusion-based processes, like PageRank and LeaderRank. Some of these methods already take into account the influences of a node's neighbors but do not directly make use of the interactions among it's neighbors. Local clustering is known to have negative impacts on the information spreading. We further show empirically that it also plays a negative role in generating local connections. Inspired by these facts, we propose a local ranking algorithm named ClusterRank, which takes into account not only the number of neighbors and the neighbors' influences, but also the clustering coefficient. Subject to the susceptible-infected-recovered (SIR) spreading model with constant infectivity, experimental results on two directed networks, a social network extracted from delicious.com and a large-scale short-message communication network, demonstrate that the ClusterRank outperforms some benchmark algorithms such as PageRank and LeaderRank. Furthermore, ClusterRank can also be applied to undirected networks where the superiority of ClusterRank is significant compared with degree centrality and k-core decomposition. In addition, ClusterRank, only making use of local information, is much more efficient than global methods: It takes only 191 seconds for a network with about Formula: see text nodes, more than 15 times faster than PageRank.
In recent years, the rapid development of modern society is calling for advanced energy storage to meet the growing demands of energy supply and generation. As one of the most promising energy ...storage systems, secondary batteries are attracting much attention. The electrolyte is an important part of the secondary battery, and its composition is closely related to the electrochemical performance of the secondary batteries. Lithium‐ion battery electrolyte is mainly composed of solvents, additives, and lithium salts, which are prepared according to specific proportions under certain conditions and according to the needs of characteristics. This review analyzes the advantages and current problems of the liquid electrolytes in lithium‐ion batteries (LIBs) from the mechanism of action and failure mechanism, summarizes the research progress of solvents, lithium salts, and additives, analyzes the future trends and requirements of lithium‐ion battery electrolytes, and points out the emerging opportunities in advanced lithium‐ion battery electrolytes development.
This review analyzes the advantages and current problems of the liquid electrolytes in lithium‐ion batteries from the mechanism of action and failure mechanism, summarizes the research progress of solvents, lithium salts, and additives, analyzes the future trends and requirements of lithium‐ion battery electrolytes, and points out the emerging opportunities in advanced lithium‐ion battery electrolytes development.
InP quantum dots (QDs) are typical III–V group semiconductor nanocrystals that feature large excitonic Bohr radius and high carrier mobility. The merits of InP QDs include large absorption ...coefficient, broad color tunability, and low toxicity, which render them promising alternatives to classic Cd/Pb‐based QDs for applications in practical settings. Over the past two decades, the advances in wet‐chemistry methods have enabled the synthesis of small‐sized colloidal InP QDs with the assistance of organic ligands. By proper selection of synthetic protocols and precursor materials coupled with surface passivation, the QYs of InP QDs are pushed to near unity with modest color purity. The state‐of‐the‐art InP QDs with appealing optical and electronic properties have excelled in many applications with the potential for commercialization. This work focuses on the recent development of wet‐chemistry protocols and various precursor materials for the synthesis and surface modification of InP QDs. Current methods for constructing light‐emitting diodes using novel InP‐based QDs are also summarized.
InP nanocrystals are promising alternatives to classic Cd/Pb‐based quantum dots (QDs) for applications in practical settings owing to the low toxicity and high emission efficiency. This work focuses on the recent advances in the synthesis and surface modification of InP QDs as well as their applications in light‐emitting diodes.
•A high content of fly ash up to 60% is incorporated into the magnesium phosphate cement system.•The effects of fly ash on the properties of the MPC system are studied.•The effect of the casting ...temperature on the setting time of the MPC system is studied.•Hydration products of the MPC system for various curing ages are yielded.
Magnesium phosphate cement (MPC) was prepared with dead burned magnesia oxide (MgO), potassium di-hydrogen phosphate (KH2PO4) and some retarders in a given proportion used in the same manner as Portland cement. Factors such as the w/c ratio, casting temperature and fly ash contents that affect the properties of MPC were studied in this paper. The experimental results demonstrate that the setting time was significantly affected by the w/c ratio and casting temperature. Adding fly ash can increase the setting time and flowability of fresh MPC paste. The compressive strengths of MPC paste prepared using various w/c ratios were measured at ages of 3h, 1d, 7d and 28d. The 3-, 7- and 28-day compressive strengths of MPC mortar prepared using various fly ash contents were also measured. The compressive strength of MPC paste decreased with an increasing w/c ratio, and the aged compressive strengths of MPC mortar increased with increasing fly ash content. The results also indicate that adding fly ash can improve the water resistance and dry shrinkage of MPC mortar. Finally, the hydrate products were analyzed using XRD and SEM.
•Application of nano-SiO2 to cement-solidified dredged sludge (CDS) can significantly improve its strength development.•Roles of cement, nano-SiO2, humic acid, lime and curing age on the ...solidification effect were evaluated.•Using lime together with cement for solidifying dredged sludge containing humic acid had advantages over using cement alone.•The nano-SiO2 content of 1.0% was considered the most cost-effective for improving the strength development of CDS.
The disposal of dredged sludge (DS) poses an increasingly difficult problem for sediment dredging engineering. This study investigated the strength development of solidifying DS containing humic acid (HA) with cement, lime and nano-SiO2 (NS). A range of unconfined compressive strength (UCS) and pH tests were conducted to explore the roles of cement, NS, HA, lime and curing age on the solidification effect of DS. Furthermore, microstructures and crystalline phases of typical mixes were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests. The results showed that the addition of NS can significantly improve the strength development of cement-solidified dredged sludge (CDS). The 60-day UCS of CDS with 1.0% NS was more than twice that without NS, concurrently, the addition of NS also reduced the pH of CDS. The HA seriously affected the strength development of CDS, and the influence threshold value of HA content was in the range of 4.5–5.0%. Using lime together with cement for solidifying DS containing HA had advantages over using cement alone, and the optimum mass ratio of lime to cement is 6:9. The optimum NS content of 1.0% was determined to be the most cost-effective for improving the strength development of CDS. The microstructure and mineralogy analysis confirmed that adding NS to CDS can effectively accelerate the hydration reaction and produce more calcium silicate hydrate (CSH), leading to a significant improvement in the strength of CDS.
PDF
