Conspectus The discovery of materials capable of storing magnetic information at the level of single molecules and even single atoms has fueled renewed interest in the slow magnetic relaxation ...properties of single-molecule magnets (SMMs). The lanthanide elements, especially dysprosium, continue to play a pivotal role in the development of potential nanoscale applications of SMMs, including, for example, in molecular spintronics and quantum computing. Aside from their fundamentally fascinating physics, the realization of functional materials based on SMMs requires significant scientific and technical challenges to be overcome. In particular, extremely low temperatures are needed to observe slow magnetic relaxation, and while many SMMs possess a measurable energy barrier to reversal of the magnetization (U eff), very few such materials display the important properties of magnetic hysteresis with remanence and coercivity. Werner-type coordination chemistry has been the dominant method used in the synthesis of lanthanide SMMs, and most of our knowledge and understanding of these materials is built on the many important contributions based on this approach. In contrast, lanthanide organometallic chemistry and lanthanide magnetochemistry have effectively evolved along separate lines, hence our goal was to promote a new direction in single-molecule magnetism by uniting the nonclassical organometallic synthetic approach with the traditionally distinct field of molecular magnetism. Over the last several years, our work on SMMs has focused on obtaining a detailed understanding of why magnetic materials based on the dysprosium metallocene cation building block {Cp2Dy}+ display slow magnetic relaxation. Specifically, we aspired to control the SMM properties using novel coordination chemistry in a way that hinges on key considerations, such as the strength and the symmetry of the crystal field. In establishing that the two cyclopentadienyl ligands combine to provide a strongly axial crystal field, we were able to propose a robust magneto-structural correlation for understanding the properties of dysprosium metallocene SMMs. In doing so, a blueprint was established that allows U eff and the magnetic blocking temperature (T B) to be improved in a well-defined way. Although experimental discoveries with SMMs occur more rapidly than quantitative theory can (currently) process and explain, a clear message emanating from the literature is that a combination of the two approaches is most effective. In this Account, we summarize the main findings from our own work on dysprosium metallocene SMMs, and consider them in the light of related experimental studies and theoretical interpretations of related materials reported by other protagonists. In doing so, we aim to contribute to the nascent and healthy debate on the nature of spin dynamics in SMMs and allied molecular nanomagnets, which will be crucial for the further advancement of this vibrant research field.
Ultralight ceramic aerogels with the property combination of recoverable compressibility and excellent high-temperature stability are attractive for use in harsh environments. However, conventional ...ceramic aerogels are usually constructed by oxide ceramic nanoparticles, and their practical applications have always been limited by the brittle nature of ceramics and volume shrinkage at high temperature. Silicon carbide (SiC) nanowire offers the integrated properties of elasticity and flexibility of one-dimensional (1D) nanomaterials and superior high-temperature thermal and chemical stability of SiC ceramics, which makes it a promising building block for compressible ceramic nanowire aerogels (NWAs). Here, we report the fabrication and properties of a highly porous three-dimensional (3D) SiC NWA assembled by a large number of interweaving 3C-SiC nanowires of 20–50 nm diameter and tens to hundreds of micrometers in length. The SiC NWA possesses ultralow density (∼5 mg cm–3), excellent mechanical properties of large recoverable compression strain (>70%) and fatigue resistance, refractory property, oxidation and high-temperature resistance, and thermal insulating property (0.026 W m–1 K–1 at room temperature in N2). When used as absorbents, the SiC NWAs exhibit an adsorption selectivity of low-viscosity organic solvents with high absorption capacity (130–237 g g–1). The successful fabrication of such an attractive material may provide promising perspectives to the design and fabrication of other compressible and multifunctional ceramic NWAs.
Hypersaline wastewater is difficult to treat due to the inhibition of salt stress on microbes’ viability and metabolic capabilities. Haloarchaea, native microorganisms that thrive in hypersaline ...habitats, overcome this key obstacle naturally. This review provides a comprehensive overview of the metabolic versatility of Haloarchaea in hypersaline wastewater treatment, including carbon, nitrogen, phosphorus, sulfur, and heavy metal metabolism. It also analyzes factors affecting pollutant removal and addresses metabolic mechanisms. Additionally, haloarchaea microbial characteristics and strategies to cope with salt stress are highlighted. Finally, the biotechnological potential of biomolecules produced from haloarchaea is investigated. To get better insight into the potential of haloarchaea, a deeper investigation of basic metabolism and more in-depth studies of their genomics and applications in actual wastewater are also necessary.
Haloarchaea are excellent candidates to treat hypersaline wastewater because they show an extensive metabolic versatility of carbon, nitrogen, phosphorus, sulfur, and heavy metal.The ‘salt-in’ strategy, mainly the accumulation of K+ and expulsion of Na+, is used by haloarchaea to cope with salt stress.Haloarchaea have special features and biomolecules, such as haloarchaeal enzymes, gas vesicles, and poly-β-hydroxyalkanoates, that make them worth exploring for their biotechnological and industrial potential.The discovery of polyextremophilic (halophilic, thermophilic, and alkaliphilic) haloarchaea promotes their real-world applications in wastewater treatment under multiple stresses.
Perfluorinated alkyl substances, such as perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), are toxic materials that are known to globally contaminate water, air, and soil resources. ...Strategies for the simultaneous detection and removal of these compounds are desired to address this emerging health and environmental issue. Herein, we develop a type of guanidinocalix5arene that can selectively and strongly bind to PFOS and PFOA, which we use to demonstrate the sensitive and quantitative detection of these compounds in contaminated water through a fluorescent indicator displacement assay. Moreover, by co-assembling iron oxide nanoparticle with the amphiphilic guanidinocalix5arene, we are able to use simple magnetic absorption and filtration to efficiently remove PFOS and PFOA from contaminated water. This supramolecular approach that uses both molecular recognition and self-assembly of macrocyclic amphiphiles is promising for the detection and remediation of water pollution.
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•Tetrahedral chalcogenides considered as the derivatives of cubic or hexagonal ZnS.•Tetrahedral chalcogenides are potential NLO, photocatalytic, and PV materials.•Hitherto no review ...for tetrahedral chalcogenides with light-related applications.•Structures and light-related applications of tetrahedral chalcogenides discussed.•Several future directions about tetrahedral chalcogenides analyzed.
There are a large number of metal chalcogenides crystallized in the wurtzite or zinc blende-derived structures, in which all of the anions or cations are fourfold-surrounded by their neighboring counter ions. These compounds can be defined as tetrahedral chalcogenides. According to valence electrons’ configuration obeying valence electron rules or not, they can be classified into two types, normal or defect tetrahedral chalcogenides. There is a closely structural relationship between them. As all the atoms have the tetrahedral-coordination styles, structure disorders of occupancies or sites can be easily happened to them. So, there are also many alloys or solid-solutions members belonging to tetrahedral chalcogenides. In view of their special structure features, rich chemical compositions, and tunable optical band gaps, they are ones of the most promising second-order nonlinear optical (NLO), photocatalytic, photovoltaic (PV), and thermoelectric candidate materials. In fact, most of these chalcogenides can be applied in more than one of the aforementioned fields.
To date, there are several review works on part of these chalcogenides, including typical I-III-VI2, I2-II-IV-VI4, and diamond-like chalcogenides. However, hitherto there is not a systematical summary about chalcogenides with tetrahedral structures. Intrigued by their flourishing developments, it is very necessary to summarize them, focusing on their structural chemistry and versatile applications. To compact this review, only several application fields related with utilization of lights are discussed, including second-order NLO, photocatalytic, and PV applications.
Fault diagnosis is critical to ensure the safety and reliable operation of rotating machinery. Most methods used in fault diagnosis of rotating machinery extract a few feature values from vibration ...signals for fault diagnosis, which is a dimensionality reduction from the original signal and may omit some important fault messages in the original signal. Thus, a novel diagnosis method is proposed involving the use of a convolutional neural network (CNN) to directly classify the continuous wavelet transform scalogram (CWTS), which is a time-frequency domain transform of the original signal and can contain most of the information of the vibration signals. In this method, CWTS is formed by discomposing vibration signals of rotating machinery in different scales using wavelet transform. Then the CNN is trained to diagnose faults, with CWTS as the input. A series of experiments is conducted on the rotor experiment platform using this method. The results indicate that the proposed method can diagnose the faults accurately. To verify the universality of this method, the trained CNN was also used to perform fault diagnosis for another piece of rotor equipment, and a good result was achieved.
Reduction of the uranium(III) metallocene (η5‐C5iPr5)2UI (1) with potassium graphite produces the “second‐generation” uranocene (η5‐C5iPr5)2U (2), which contains uranium in the formal divalent ...oxidation state. The geometry of 2 is that of a perfectly linear bis(cyclopentadienyl) sandwich complex, with the ground‐state valence electron configuration of uranium(II) revealed by electronic spectroscopy and density functional theory to be 5f3 6d1. Appreciable covalent contributions to the metal‐ligand bonds were determined from a computational study of 2, including participation from the uranium 5f and 6d orbitals. Whereas three unpaired electrons in 2 occupy orbitals with essentially pure 5f character, the fourth electron resides in an orbital defined by strong 7s‐6dz2
mixing.
A new generation: Reduction of the uranium(III) metallocene (η5‐C5iPr5)2UI with potassium graphite produces the “second‐generation” uranocene (η5‐C5iPr5)2U, which contains uranium in the formal divalent oxidation state. The geometry of (η5‐C5iPr5)2U is that of a perfectly linear bis(cyclopentadienyl) sandwich complex.
Although phase transition materials (PTMs) under external stimuli are of great research interest duo to their rich potential applications, it is still challenging to explore multi‐responsive PTMs. ...Herein, two different phases of organic–inorganic hybrid copper‐based halides, α‐ and β‐Gua3Cu2I5 (Gua+=CN3H6+), were synthesized by solvent evaporation method, which they crystalize in the noncentrosymmetric space group Fdd2 with zero‐dimensional structure and centrosymmetric space group C2/c with one‐dimensional metal‐halogen framework, respectively. Interestingly, it is firstly demonstrated that Gua3Cu2I5 simultaneously possesses reversible PL conversion and NLO switching properties in response to thermal stimulus. Strikingly, apart from heat, its structural phase transition can also be triggered by crystalline‐phase‐recognition (CPR) and mechanical force. These new findings may pave a path for future exploration of PTMs with multiple physical properties.
A multi‐stimuli responsive luminescent material has been developed that not only exhibits reversible photoluminescence conversion and nonlinear optical switching in response to thermal stimulus, but also displays peculiar crystal‐phase‐recognition induced domino‐type single‐crystal‐to‐single‐crystal phase transition and mechanical force induced phase transition under concomitant emission‐color change.
This review summarizes the recent progress the emerging area of photochemical reaction initiated by Electron-donor–acceptor (EDA) complex in synthetic organic chemistry. Recent developments in the ...photochemical carbon–carbon and carbon–heteroatom bond formation using expensive transition-metal catalysts, toxic reagents, photoinduced bond dissociation are well known. Although the physicochemical properties of EDA complexes have been enormously studied in applied and materials chemistry but their use in synthetic chemistry remains unexplored. Great importance has given to develop an environmentally benign technology in order to improve the processes of radical generation. The radical reaction via EDA complexes process attracted much attention and achieved many advances in organic synthetic filed owing to avoiding the use of expensive transition-metal catalysts, toxic reagents, as well as explosive oxidants. We believe that this review will update researchers focused on searching new photochemical reaction via EDA mechanism and will encourage further growth in this field.
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•This review aims to describe representative synthetic applications via EDA process.•EDA process provides a valuable method to construct C-X bond under mild conditions.•EDA process is remarkable for the possibilities to design new photocatalysis system.•EDA complex-mediated organic synthesis is still at their early stage.
This review summarizes the recent progress the emerging area of photochemical reaction initiated by Electron-donor-acceptor (EDA) complex in synthetic organic chemistry. Recent developments in the photochemical carbon-carbon and carbon-heteroatom bond formation using expensive transition-metal catalysts, toxic reagents, photoinduced bond dissociation are well known. Although the physicochemical properties of EDA complexes have been enormously studied in applied and materials chemistry but their use in synthetic chemistry remains unexplored. Great importance has given to develop an environmentally benign technology in order to improve the processes of radical generation. The radical reaction via EDA complexes process attracted much attention and achieved many advances in organic synthetic filed owing to avoiding the use of expensive transition-metal catalysts, toxic reagents, as well as explosive oxidants. We believe that this review will update researchers focused on searching new photochemical reaction via EDA mechanism and will encourage further growth in this field.
The synthesis, structure and magnetic properties of the indigo-bridged dilanthanide complexes {(η
-Cp*)
Ln}
(μ-ind)
with Ln = Gd or Dy and n = 0, 1 or 2 are described. The gadolinium complexes with n ...= 0 and 2 show typically weak exchange coupling, whereas the complex bridged by the radical ind
ligand shows an unusually large coupling constant of J = -11 cm
(-2J formalism). The dysprosium complexes with n = 0 and 1 are single-molecule magnets in zero applied field, whereas the complex with n = 2 does not show slow magnetic relaxation.
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