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.
We report a series of heterobimetallic Pt/Zn and Pt/Ca complexes to study the effect of proximity of a dicationic base metal on the organometallic Pt species. Varying degrees of Pt⋅⋅⋅Zn and Zn ...interaction with the bridging Me group are achieved, showcasing snapshots of a hypothetical process of retrotransmetalation from Pt to Zn. In contrast, only weak interactions were observed for Ca with a Pt‐bound Me group. Activation of H2, B−H and Si−H bonds leads to the formation of hydride‐bridged Pt−H−Zn complexes, which is not observed in the absence of Zn, pointing out the importance of metal‐metal cooperation. Reactivity of PtMe2/M2+ with terminal acetylene, water and methanol is also studied, leading to facile protonation of one of the Me groups at the Pt center only when Zn is present. This study sheds light on various ways in which the presence of a 2+ metal cation significantly affects the reactivity of a common organoplatinum complex.
Pt/Zn and Pt/Ca dimethyl complexes feature various degrees of metal‐metal and metal‐Me interactions and show Pt/Zn cooperative activation of H2, B−H and Si−H bonds, observed only when Zn is in close proximity to Pt, as well as facile protonolysis by water, MeOH and C−H bond of terminal acetylene.
Trace metals are essential for the growth of anaerobic microorganisms, however, in practice they are often added to anaerobic digesters in excessive amounts, which can lead to inhibition. The concept ...of bioavailability of metals in anaerobic digestion has been poorly understood in the past, and a lack of deep understanding of the relationship between trace metal speciation and bioavailability can result in ineffective metal dosing strategies for anaerobic digesters. Sequential extraction schemes are useful for fractionating trace metals into their different forms, and metal sulfides can serve as a store and source for trace metals during anaerobic digestion, while natural/synthetic chelating agents (soluble microbial products-SMPs, extracellular polysaccharides-EPS, and EDTA/NTA) are capable of controlling trace metal bioavailability. Nevertheless, more work is needed to: investigate the speciation and bioavailability of Ca, Mg, Mn, W, and Se; compare the bioavailability of different forms of trace metals e.g. carbonates, sulfides, phosphates to different anaerobic trophic groups; determine what factors influence metal sulfide dissolution; investigate whether chelating agents can increase trace metal bioavailability; develop and adapt specialized analytical techniques, and; determine how trace metal dynamics change in an anaerobic membrane bioreactor (AnMBR).
There is a great interest in portable gas sensing technologies to provide real-time monitoring of indoor and outdoor air quality as well as the human health diagnostics. One-dimensional metal oxide ...nanowires have demonstrated improved properties compared to the conventional thick film gas sensors. Furthermore, two-dimensional semiconductor nanomaterials have shown great promise for the development of high performance functional devices owing to their unique physical, chemical and electrical characteristics. Hence, they become one of the most investigated structures for the fabrication of detection systems. Herein, we present an overview of the synthesis and sensing properties of metal oxide nanowires and two-dimensional semiconductor nanostructures such as metal-organic frameworks, graphene and transition metal dichalcogenides. We discuss the current achievements and issues in the preparation of pure, doped and composite materials comprising metal oxide nanowires and two-dimensional semiconductors. Then, we discuss the advances in gas sensing performances of the aforementioned materials considering their morphology, compositions and structure. Afterward, we provide a brief summary along with the opportunities and challenges for future fabrication of high performance and small size gas sensing devices.
Trace metal metabolism in plants Andresen, Elisa; Peiter, Edgar; Küpper, Hendrik
Journal of experimental botany,
02/2018, Volume:
69, Issue:
5
Journal Article
Peer reviewed
Open access
This review provides a comprehensive overview of the field of metal metabolism in plants, including uptake, transport inside the plant, metabolic use, deficiency, and toxicity of essential trace ...metals.
Abstract
Many trace metals are essential micronutrients, but also potent toxins. Due to natural and anthropogenic causes, vastly different trace metal concentrations occur in various habitats, ranging from deficient to toxic levels. Therefore, one focus of plant research is on the response to trace metals in terms of uptake, transport, sequestration, speciation, physiological use, deficiency, toxicity, and detoxification. In this review, we cover most of these aspects for the essential micronutrients copper, iron, manganese, molybdenum, nickel, and zinc to provide a broader overview than found in other recent reviews, to cross-link aspects of knowledge in this very active research field that are often seen in a separated way. For example, individual processes of metal usage, deficiency, or toxicity often were not mechanistically interconnected. Therefore, this review also aims to stimulate the communication of researchers following different approaches, such as gene expression analysis, biochemistry, or biophysics of metalloproteins. Furthermore, we highlight recent insights, emphasizing data obtained under physiologically and environmentally relevant conditions.
A molten lithium infusion strategy has been proposed to prepare stable Li‐metal anodes to overcome the serious issues associated with dendrite formation and infinite volume change during cycling of ...lithium‐metal batteries. Stable host materials with superior wettability of molten Li are the prerequisite. Here, it is demonstrated that a series of strong oxidizing metal oxides, including MnO2, Co3O4, and SnO2, show superior lithiophilicity due to their high chemical reactivity with Li. Composite lithium‐metal anodes fabricated via melt infusion of lithium into graphene foams decorated by these metal oxide nanoflake arrays successfully control the formation and growth of Li dendrites and alleviate volume change during cycling. A resulting Li‐Mn/graphene composite anode demonstrates a super‐long and stable lifetime for repeated Li plating/stripping of 800 cycles at 1 mA cm−2 without voltage fluctuation, which is eight times longer than the normal lifespan of a bare Li foil under the same conditions. Furthermore, excellent rate capability and cyclability are realized in full‐cell batteries with Li‐Mn/graphene composite anodes and LiCoO2 cathodes. These results show a major advancement in developing a stable Li anode for lithium‐metal batteries.
A series of metal oxide nanoflakes are explored as new lithiophilic materials for ultra‐stable anodes of lithium‐metal batteries. By minimizing the volume change of Li metal and dendrite formation, the composite Li anode exhibits a super‐long and stable lifetime for over 800 cycles.
The book gives a synthetic presentation of the research performed in the field of sheet metal forming simulation during more than twenty years by the members of three teams: the Research Centre on ...Sheet Metal Forming - CERTETA (Technical University of Cluj-Napoca, Romania), AUTOFORM software-house company from Zürich, Switzerland and VOLVO automotive company from Sweden.The first chapter reminds some fundamental topics of the theory of plasticity. A more extended chapter is devoted to the presentation of the phenomenological yield criteria, emphasizing the formulations proposed by the CERTETA team (BBC models). The sheet metal formability is discussed in a separate chapter. After presenting the methods used for the formability assessment, the discussion focuses on the forming limit curves. In this context, the authors emphasize their contributions to the mathematical modeling of forming limit curves. The aspects related to the implementation of the constitutive models in finite-element codes are discussed in the last chapter of the book. The performances of the models are proved by the numerical simulation of various sheet metal forming processes: hydroforming, deep-drawing and forming of the complex parts. The book is useful for the students, doctoral fellows, researchers and engineers who are mainly interested in the mechanical modeling and numerical simulation of sheet metal forming processes.Modeling and numerical simulation of sheet metal forming processes.
Single-atom catalysts make exceptionally efficient use of expensive noble metals and can bring out unique properties. However, applications are usually compromised by limited catalyst stability, ...which is due to sintering. Although sintering can be suppressed by anchoring the metal atoms to oxide supports, strong metal-oxygen interactions often leave too few metal sites available for reactant binding and catalysis, and when exposed to reducing conditions at sufficiently high temperatures, even oxide-anchored single-atom catalysts eventually sinter4,8,9. Here we show that the beneficial effects of anchoring can be enhanced by confining the atomically dispersed metal atoms on oxide nanoclusters or 'nanoglues', which themselves are dispersed and immobilized on a robust, high-surface-area support. We demonstrate the strategy by grafting isolated and defective CeOx nanoglue islands onto high-surface-area SiO2; the nanoglue islands then each host on average one Pt atom. We find that the Pt atoms remain dispersed under both oxidizing and reducing environments at high temperatures, and that the activated catalyst exhibits markedly increased activity for CO oxidation. We attribute the improved stability under reducing conditions to the support structure and the much stronger affinity of Pt atoms for CeOx than for SiO2, which ensures the Pt atoms can move but remain confined to their respective nanoglue islands. The strategy of using functional nanoglues to confine atomically dispersed metals and simultaneously enhance their reactivity is general, and we anticipate that it will take single-atom catalysts a step closer to practical applications.
Mixed‐metal metal–organic frameworks (MM‐MOFs) can be considered to be those MOFs having two different metals anywhere in the structure. Herein we summarize the various strategies for the preparation ...of MM‐MOFs and some of their applications in adsorption, gas separation, and catalysis. It is shown that compared to homometallic MOFs, MM‐MOFs bring about the opportunity to take advantage of the complexity and the synergism derived from the presence of different metal ions in the structure of MOFs. This is reflected in a superior performance and even stability of MM‐MOFs respect to related single‐metal MOFs. Emphasis is made on the use of MM‐MOFs as catalysts for tandem reactions.
Mix and miss‐match: This Minireview summarizes the recent developments on the synthesis of mixed‐metal metal–organic frameworks (MM‐MOFs). Such multivariate MOFs represent a higher degree of complexity than homometallic MOFs, frequently showing advantages over simple MOFs with respect to their properties and applications, particularly in heterogeneous catalysis.
With the rapid development of nanotechnology, new nanomaterials with enormous potentials continue to emerge, especially metal nanomaterials. Metal nanomaterials possess the characteristics of metals ...and nanomaterials, so they are widely used in many fields. But at the same time, whether the use or release of metal nan4omaterials into the environment is toxic to human beings and animals has now attained widespread attention at home and abroad. Currently, it is an indisputable fact that cancer ranks among the top causes of death among residents worldwide. The properties of causing DNA damage and mutations possessed by these metal nanomaterials make them unpredictable influences in the body, subsequently leading to genotoxicity and carcinogenicity. Due to the increasing evidence of their roles in carcinogenicity, this article reviews the toxicological and carcinogenic effects of metal nanomaterials, including nano‐metal elements (nickel nanoparticles, silver nanoparticles, and cobalt nanoparticles) and nano‐metal oxides (titanium dioxide nanoparticles, silica nanoparticles, zinc oxide nanoparticles, and alumina nanoparticles). This article provides a reference for the researchers and policymakers to use metal nanomaterials rationally in modern industries and biomedicine.
Metal nanomaterials may cause serious adverse reactions to humans and animals, especially carcinogenicity. This article reviews the properties, applications and general toxicity and carcinogenic effects of metal nanomaterials. It is recommended to evaluate the potential toxicity and carcinogenicity of metal nanoparticles and control their use.
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