An in-depth look at the exquisite metal sculpture of the
Roman baroque Roman baroque sculpture is usually thought
of in terms of large-scale statues in marble and bronze, tombs, or
portrait busts. ...Smaller bronze statuettes are often overlooked, and
the extensive production of sculptural silver-much of which is now
lost but can be studied from drawings-is frequently omitted from
the histories of art. In this book, Jennifer Montagu enriches our
understanding of the sculpture of the period by investigating the
bronzes that adorn the great tabernacles of Roman churches; gilded
silver, both secular and ecclesiastical; elaborately embossed
display dishes; and the production of medals. Concentrating on
selected pieces by such master sculptors as Bernini and leading
metal-workers such as Giovanni Giardini, Montagu examines the often
tortuous relationship between patrons and artists and elucidates
the relationship between those who provided the drawings or models
and the craftsmen who executed the finished sculptures.
The utilization of polymer/metal organic framework (MOF) nanocomposites in various biomedical applications has been widely studied due to their unique properties that arise from MOFs or hybrid ...composite systems. This review focuses on the types of polymer/MOF nanocomposites used in drug delivery and imaging applications. Initially, a comprehensive introduction to the synthesis and structure of MOFs and bio-MOFs is presented. Subsequently, the properties and the performance of polymer/MOF nanocomposites used in these applications are examined, in relation to the approach applied for their synthesis: (i) non-covalent attachment, (ii) covalent attachment, (iii) polymer coordination to metal ions, (iv) MOF encapsulation in polymers, and (v) other strategies. A critical comparison and discussion of the effectiveness of polymer/MOF nanocomposites regarding their synthesis methods and their structural characteristics is presented.
Investigations of two-dimensional transition-metal chalcogenides (TMCs) have recently revealed interesting physical phenomena, including the quantum spin Hall effect
, valley polarization
and ...two-dimensional superconductivity
, suggesting potential applications for functional devices
. However, of the numerous compounds available, only a handful, such as Mo- and W-based TMCs, have been synthesized, typically via sulfurization
, selenization
and tellurization
of metals and metal compounds. Many TMCs are difficult to produce because of the high melting points of their metal and metal oxide precursors. Molten-salt-assisted methods have been used to produce ceramic powders at relatively low temperature
and this approach
was recently employed to facilitate the growth of monolayer WS
and WSe
. Here we demonstrate that molten-salt-assisted chemical vapour deposition can be broadly applied for the synthesis of a wide variety of two-dimensional (atomically thin) TMCs. We synthesized 47 compounds, including 32 binary compounds (based on the transition metals Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re, Pt, Pd and Fe), 13 alloys (including 11 ternary, one quaternary and one quinary), and two heterostructured compounds. We elaborate how the salt decreases the melting point of the reactants and facilitates the formation of intermediate products, increasing the overall reaction rate. Most of the synthesized materials in our library are useful, as supported by evidence of superconductivity in our monolayer NbSe
and MoTe
samples
and of high mobilities in MoS
and ReS
. Although the quality of some of the materials still requires development, our work opens up opportunities for studying the properties and potential application of a wide variety of two-dimensional TMCs.
Dual‐metal‐atom‐center catalysts (DACs) are a novel frontier in oxygen electrocatalysis, boasting functional and electronic synergies between contiguous metal centers and higher catalytic activities ...than single‐atom‐center catalysts. However, the definition and catalytic mechanism of DACs configurations remain unclear. Here, a “pre‐constrained metal twins” strategy is proposed to prepare contiguous FeN4 and CoN4 DACs with homogeneous conformations embedded in a N‐doped graphitic carbon (FeCo‐DACs/NC). A programmable phthalocyanines dimer is used as a structural moiety to anchor the bimetallic sites (containing Co and Fe) in a metal–organic framework (MOF) to achieve delocalized dispersion before pyrolysis. The resultant FeCo‐DACs/NC exhibits excellent electrochemical performance in oxygen electrocatalysis and rechargeable Zn–air batteries. Theoretical calculations demonstrate that the synergetic interaction of adjacent metals optimizes the d‐band center position of metal centers and balances the free energy of the *O intermediate, thereby improving the oxygen electrocatalytic activity. This work opens up an avenue for the rational design of DACs with tailored electronic structures and uniform geometric configurations.
A “pre‐constrained metal twin” strategy is presented for the first time to prepare dual‐metal‐atom‐center catalysts (FeCo‐DACs/NC) with continuous FeN4 and CoN4. The FeCo‐DACs/NC delivers excellent catalytic activity in oxygen evolution reaction, oxygen reduction reaction, and Zn–air batteries. The synergistic effect between the two metals optimizes the free energy of the oxygen intermediate state, resulting in improved performance.
Certain five heavy metals viz. arsenic (As), cadmium (Cd), chromium (Cr)(VI), mercury (Hg), and lead (Pb) are non-threshold toxins and can exert toxic effects at very low concentrations. These heavy ...metals are known as most problematic heavy metals and as toxic heavy metals (THMs). Several industrial activities and some natural processes are responsible for their high contamination in the environment. In recent years, high concentrations of heavy metals in different natural systems including atmosphere, pedosphere, hydrosphere, and biosphere have become a global issue. These THMs have severe deteriorating effects on various microorganisms, plants, and animals. Human exposure to the THMs may evoke serious health injuries and impairments in the body, and even certain extremities can cause death. In all these perspectives, this review provides a comprehensive account of the relative impact of the THMs As, Cd, Cr(VI), Hg, and Pb on our total environment.
Oxygen evolution reaction (OER) is expected to be of great importance for the future energy conversion and storage in form of hydrogen by water electrolysis. Besides the traditional noble‐metal or ...transition metal oxide‐based catalysts, carbonaceous electrocatalysts are of great interest due to their huge structural and compositional variety and unrestricted abundance. This review provides a summary of recent advances in the field of carbon‐based OER catalysts ranging from “pure” or unintentionally doped carbon allotropes over heteroatom‐doped carbonaceous materials and carbon/transition metal compounds to metal oxide composites where the role of carbon is mainly assigned to be a conductive support. Furthermore, the review discusses the recent developments in the field of ordered carbon framework structures (metal organic framework and covalent organic framework structures) that potentially allow a rational design of heteroatom‐doped 3D porous structures with defined composition and spatial arrangement of doping atoms to deepen the understanding on the OER mechanism on carbonaceous structures in the future. Besides introducing the structural and compositional origin of electrochemical activity, the review discusses the mechanism of the catalytic activity of carbonaceous materials, their stability under OER conditions, and potential synergistic effects in combination with metal (or metal oxide) co‐catalysts.
Advanced carbonaceous oxygen evolution reaction catalysts for water‐splitting applications rely on synthesis procedures enabling formation of nanosized 3D, defect‐rich, and heteroatom‐doped carbon structures and inorganic particle‐containing hybrid materials. Parameters affecting the electrocatalytic activity include defect engineering, heteroatom doping, and hybrid composite formation as well as the formation of framework structures defined by molecular building blocks.
Metal–gas batteries draw a lot of attention due to their superiorities in high energy density and stable performance. However, the sluggish electrochemical reactions and associated side reactions in ...metal–gas batteries require suitable catalysts, which possess high catalytic activity and selectivity. Although precious metal catalysts show a higher catalytic activity, high cost of the precious metal catalysts hinders their commercial applications. In contrast, nonprecious metal catalysts complement the weakness of cost, and the gap in activity can be made up by increasing the amount of the nonprecious metal active centers. Herein, recent work on carbon‐based nonprecious metal catalysts for metal–gas batteries is summarized. This review starts with introducing the advantages of carbon‐based nonprecious metal catalysts, followed by a discussion of the synthetic strategy of carbon‐based nonprecious metal catalysts and classification of active sites, and finally a summary of present metal–gas batteries with the carbon‐based nonprecious metal catalysts is presented. The challenges and opportunities for carbon‐based nonprecious metal catalysts in metal–gas batteries are also explored.
This article summarizes the recent carbon‐based nonprecious metal catalysts for metal–gas batteries. The synthesis method of carbon‐based nonprecious metal catalysts and category of active sites are discussed for helping the cognition of the catalytic mechanism and property. In addition, the challenges and opportunities for carbon‐based nonprecious metal catalysts in metal–gas batteries are presented.
The most adverse outcome of increasing industrialization is contamination of the ecosystem with heavy metals. Toxic heavy metals possess a deleterious effect on all forms of biota; however, they ...affect the microbial system directly. These heavy metals form complexes with the microbial system by forming covalent and ionic bonds and affecting them at the cellular level and biochemical and molecular levels, ultimately leading to mutation affecting the microbial population. Microbes, in turn, have developed efficient resistance mechanisms to cope with metal toxicity. This review focuses on the vital tolerance mechanisms employed by the fungus to resist the toxicity caused by heavy metals. The tolerance mechanisms have been basically categorized into biosorption, bioaccumulation, biotransformation, and efflux of metal ions. The mechanisms of tolerance to some toxic metals as copper, arsenic, zinc, cadmium, and nickel have been discussed. The article summarizes and provides a detailed illustration of the tolerance means with specific examples in each case. Exposure of metals to fungal cells leads to a response that may lead to the formation of metal nanoparticles to overcome the toxicity by immobilization in less toxic forms. Therefore, fungal-mediated green synthesis of metal nanoparticles, their mechanism of synthesis, and applications have also been discussed. An understanding of how fungus resists metal toxicity can provide insights into the development of adaption techniques and methodologies for detoxification and removal of metals from the environment.
•Review focuses on mechanisms used by fungus to resist the toxicity by heavy metals.•Mechanisms:biosorption, bioaccumulation, biotransformation, and efflux of metal ions.•Interaction with toxic metals-copper, arsenic, zinc, cadmium, nickel is discussed.•Exposure of metals to fungal cells leads formation of metal nanoparticles.•Fungal-mediated metal nanoparticles synthesis-mechanism-applications discussed.
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