National Interuniversity Consortium of Materials Science and Technology

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles ("MISEV") guidelines for the field in 2014. We now update these "MISEV2014" guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points.

CP2K is an open source electronic structure and molecular dynamics software package to perform atomistic simulations of solid-state, liquid, molecular, and biological systems. It is especially aimed at massively parallel and linear-scaling electronic structure methods and state-of-the-art ab initio molecular dynamics simulations. Excellent performance for electronic structure calculations is achieved using novel algorithms implemented for modern high-performance computing systems. This review revisits the main capabilities of CP2K to perform efficient and accurate electronic structure simulations. The emphasis is put on density functional theory and multiple post-Hartree-Fock methods using the Gaussian and plane wave approach and its augmented all-electron extension.

Molecules comprising a large number of coupled paramagnetic centers are attracting much interest because they may show properties which are intermediate between those of simple paramagnets and classical bulk magnets and provide unambiguous evidence of quantum size effects in magnets. To date, two cluster families, usually referred to as Mn12 and Fe8, have been used to test theories. However, it is reasonable to predict that other classes of molecules will be discovered which have similar or superior properties. To do this it is necessary that synthetic chemists have a good understanding of the correlation between the structure and properties of the molecules, for this it is necessary that concepts such as quantum tunneling, quantum coherence, quantum oscillations are understood. The goal of this article is to review the fundamental concepts needed to understand quantum size effects in molecular magnets and to critically report what has been done in the field to date.

In the last years membrane processes for gas separation are gaining a larger acceptance in industry and in the market are competing with consolidated operations such as pressure swing absorption and cryogenic distillation. The key for new applications of membranes in challenging and harsh environments (e.g., petrochemistry) is the development of new tough, high performance materials. The modular nature of membrane operations is intrinsically fit for process intensification, and this versatility might be a decisive factor to impose membrane processes in most gas separation fields, in a similar way as today membranes represent the main technology for water treatment. This review highlights the most promising areas of research in gas separation, by considering the materials for membranes, the industrial applications of membrane gas separations, and finally the opportunities for the integration of membrane gas separation units in hybrid systems for the intensification of processes.

In the last two decades, plasmon resonance in gold nanoparticles (Au NPs) has been the subject of intense research efforts. Plasmon physics is intriguing and its precise modelling proved to be challenging. In fact, plasmons are highly responsive to a multitude of factors, either intrinsic to the Au NPs or from the environment, and recently the need emerged for the correction of standard electromagnetic approaches with quantum effects. Applications related to plasmon absorption and scattering in Au NPs are impressively numerous, ranging from sensing to photothermal effects to cell imaging. Also, plasmon-enhanced phenomena are highly interesting for multiple purposes, including, for instance, Raman spectroscopy of nearby analytes, catalysis, or sunlight energy conversion. In addition, plasmon excitation is involved in a series of advanced physical processes such as non-linear optics, optical trapping, magneto-plasmonics, and optical activity. Here, we provide the general overview of the field and the background for appropriate modelling of the physical phenomena. Then, we report on the current state of the art and most recent applications of plasmon resonance in Au NPs.

Through a combined use of experimental and theoretical approaches such as XRPD, EXAFS, IR, and UV−vis spectroscopies and ab initio periodic DFT calculations, we report a detailed characterization of structural, vibrational, and electronic properties of UiO-66 (Zr-BDC MOF) in its hydroxylated and dehydroxylated forms. The stability of the materials with respect to the most common solvents, acids, and bases is determined by combining XRPD and TGA/MS techniques. The structures of the two forms of UiO-66 are refined through an interactive XRPD/EXAFS approach and validated by ab initio calculations. Experimental and calculated IR spectra are reported and compared to enlighten the nature of vibrational modes upon dehydroxylation and to show the complete reversibility of the dehydration/hydration phenomenon. Experimental and calculated band gaps are also reported and compared. In this work, we show the necessity to combine, in a synergic way, different experimental techniques and periodic ab initio approaches to disclose and fully understand the nature of complex novel materials such as UiO-66 on structural, vibrational, and electronic grounds. The correct structure refinement could not be possible using one of these three approaches alone, in particular, XRPD data were unable to detect an important distortion of the Zr 6 O 6 units of the dehydrated material that was, however, foreseen in the ab initio calculations and measured in the EXAFS spectra.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMagnetism of Lanthanides in Molecular Materials with Transition-Metal Ions and Organic RadicalsCristiano Benelli and Dante GatteschiView Author Information Department of Chemistry, University of Florence, UdR INSTM, Polo Scientifico Universitario, I 50019 Sesto Fiorentino, Italy Cite this: Chem. Rev. 2002, 102, 6, 2369–2388Publication Date (Web):May 25, 2002Publication History Received30 January 2002Published online25 May 2002Published inissue 1 June 2002https://pubs.acs.org/doi/10.1021/cr010303rhttps://doi.org/10.1021/cr010303rresearch-articleACS PublicationsCopyright © 2002 American Chemical SocietyRequest reuse permissionsArticle Views7878Altmetric-Citations1478LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Ions,Ligands,Magnetic properties,Quantum mechanics,Reaction products Get e-Alerts

The high performance of ceria (CeO2) as an oxygen buffer and active support for noble metals in catalysis relies on an efficient supply of lattice oxygen at reaction sites governed by oxygen vacancy formation. We used high-resolution scanning tunneling microscopy and density functional calculations to unravel the local structure of surface and subsurface oxygen vacancies on the (111) surface. Electrons left behind by released oxygen localize on cerium ions. Clusters of more than two vacancies exclusively expose these reduced cerium ions, primarily by including subsurface vacancies, which therefore play a crucial role in the process of vacancy cluster formation. These results have implications for our understanding of oxidation processes on reducible rare-earth oxides.

Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support.

Presented in this paper is a deep investigation into the defect chemistry of UiO-66 when synthesized in the presence of monocarboxylic acid modulators under the most commonly employed conditions. We unequivocally demonstrate that missing cluster defects are the predominant defect and that their concentration (and thus the porosity and composition of the material) can be tuned to a remarkable extent by altering the concentration and/or acidity of the modulator. Finally, we attempt to rationalize these observations by speculating on the underlying solution chemistry.

Replacement of part of the fossil fuel consumption by renewable energy, in particular in the chemical industry, is a central strategy for resource and energy efficiency. This perspective will show that CO2 is the key molecule to proceed effectively in this direction. The routes, opportunities and barriers in increasing the share of renewable energy by using CO2 reaction and their impact on the chemical and energy value chains are discussed after introducing the general aspects of this topic evidencing the tight integration between the CO2 use and renewable energy insertion in the value chain of the process industry. The focus of this perspective article is on the catalytic aspects of the chemistries involved, with an analysis of the state-of-the-art, perspectives and targets to be developed. The reactions discussed are the production of short-chain olefins (ethylene, propylene) from CO2, and the conversion of carbon dioxide to syngas, formic acid, methanol and dimethyl ether, hydrocarbons via Fischer–Tropsch synthesis and methane. The relevance of availability, cost and environmental footprints of H2 production routes using renewable energies is addressed. The final part discusses the possible scenario for CO2 as an intermediary for the incorporation of renewable energy in the process industry, with a concise roadmap for catalysis needs and barriers to reach this goal.

In this tutorial review we discuss some basic aspects concerning the magnetic properties of rare-earth ions, which are currently the subject of a renovated interest in the field of molecular magnetism, after the discovery that slow relaxation of the magnetization at liquid nitrogen temperature can occur in mononuclear complexes of these ions. Focusing on Dy(III) derivatives a tutorial discussion is given of the relation of the crystal field parameters, which determine the anisotropy of these systems and consequently their interesting magnetic properties, with the geometry of the coordination sphere around the lanthanide centre and with the pattern of f orbitals. The problem of systems of low point symmetry is also addressed by showing how detailed single crystal investigation, coupled to more sophisticated calculation procedures, is an absolute necessity to obtain meaningful structure-property relationships in these systems.

There is a critical need for improved methane-oxidation catalysts to both reduce emissions of methane, a greenhouse gas, and improve the performance of gas turbines. However, materials that are currently available either have low activity below 400°C or are unstable at higher temperatures. Here, we describe a supramolecular approach in which single units composed of a palladium (Pd) core and a ceria (CeO(2)) shell are preorganized in solution and then homogeneously deposited onto a modified hydrophobic alumina. Electron microscopy and other structural methods revealed that the Pd cores remained isolated even after heating the catalyst to 850°C. Enhanced metal-support interactions led to exceptionally high methane oxidation, with complete conversion below 400°C and outstanding thermal stability under demanding conditions.

Surface-enhanced Raman scattering (SERS) has become a powerful tool in chemical, material and life sciences, owing to its intrinsic features (i.e., fingerprint recognition capabilities and high sensitivity) and to the technological advancements that have lowered the cost of the instruments and improved their sensitivity and user-friendliness. We provide an overview of the most significant aspects of SERS. First, the phenomena at the basis of the SERS amplification are described. Then, the measurement of the enhancement and the key factors that determine it (the materials, the hot spots, and the analyte-surface distance) are discussed. A section is dedicated to the analysis of the relevant factors for the choice of the excitation wavelength in a SERS experiment. Several types of substrates and fabrication methods are illustrated, along with some examples of the coupling of SERS with separation and capturing techniques. Finally, a representative selection of applications in the biomedical field, with direct and indirect protocols, is provided. We intentionally avoided using a highly technical language and, whenever possible, intuitive explanations of the involved phenomena are provided, in order to make this review suitable to scientists with different degrees of specialization in this field.

Polyhydroxyalkanoates (PHAs) are gaining increasing attention in the biodegradable polymer market due to their promising properties such as high biodegradability in different environments, not just in composting plants, and processing versatility. Indeed among biopolymers, these biogenic polyesters represent a potential sustainable replacement for fossil fuel-based thermoplastics. Most commercially available PHAs are obtained with pure microbial cultures grown on renewable feedstocks (i.e. glucose) under sterile conditions but recent research studies focus on the use of wastes as growth media. PHA can be extracted from the bacteria cell and then formulated and processed by extrusion for production of rigid and flexible plastic suitable not just for the most assessed medical applications but also considered for applications including packaging, moulded goods, paper coatings, non-woven fabrics, adhesives, films and performance additives. The present paper reviews the different classes of PHAs, their main properties, processing aspects, commercially available ones, as well as limitations and related improvements being researched, with specific focus on potential applications of PHAs in packaging.

This critical review presents an overview of the various classes of oxide materials exhibiting fast oxide-ion or proton conductivity for use as solid electrolytes in clean energy applications such as solid oxide fuel cells. Emphasis is placed on the relationship between structural and mechanistic features of the crystalline materials and their ion conduction properties. After describing well-established classes such as fluorite- and perovskite-based oxides, new materials and structure-types are presented. These include a variety of molybdate, gallate, apatite silicate/germanate and niobate systems, many of which contain flexible structural networks, and exhibit different defect properties and transport mechanisms to the conventional materials. It is concluded that the rich chemistry of these important systems provides diverse possibilities for developing superior ionic conductors for use as solid electrolytes in fuel cells and related applications. In most cases, a greater atomic-level understanding of the structures, defects and conduction mechanisms is achieved through a combination of experimental and computational techniques (217 references).

Metalorganic frameworks (MOFs) are a relatively newclass of crystalline porous materials. One family of these materials that has attracted considerable attention due to their high thermal, chemical, and mechanical stability is the zirconium based MOFs of the UiO family. The material with benzene-1,4-dicarboxylic acid (BDC) as linker is named UiO-66 and is considered to be the parent of the series, from which other members are derived via isoreticular synthesis. A multitude of synthetic procedures has been reported for UiO- 66, with the majority of groups utilizing their own strategies in favor of using one from the pool of pre-existing protocols. With the exception of two recent studies in which the effect of HCl and acetic acid were respectively investigated, there is a lack of understanding of how the product is affected by changes in synthesis parameters. It is especially important to attain such knowledge on UiO MOFs given that past studies have demonstrated there to be several ways in which a given UiO-66 sample may differ from the idealized, non-defective material of composition Zr6O4(OH)4(BDC)6. The most dramatic way that a sample may deviate from ideality is that it may have a significantly lower thermal stability than expected, an issue which has not been previously reported. Figure 1 (discussed in depth later) demonstrates the surprisingly wide variation in the thermal stabilities of three UiO-66 samples synthesized at different temperatures, highlighting how severely the material can be affected by alterations to the synthesis conditions.

CO2 methanation is a well-known reaction that is of interest as a capture and storage (CCS) process and as a renewable energy storage system based on a power-to-gas conversion process by substitute or synthetic natural gas (SNG) production. Integrating water electrolysis and CO2 methanation is a highly effective way to store energy produced by renewables sources. The conversion of electricity into methane takes place via two steps: hydrogen is produced by electrolysis and converted to methane by CO2 methanation. The effectiveness and efficiency of power-to-gas plants strongly depend on the CO2 methanation process. For this reason, research on CO2 methanation has intensified over the last 10 years. The rise of active, selective, and stable catalysts is the core of the CO2 methanation process. Novel, heterogeneous catalysts have been tested and tuned such that the CO2 methanation process increases their productivity. The present work aims to give a critical overview of CO2 methanation catalyst production and research carried out in the last 50 years. The fundamentals of reaction mechanism, catalyst deactivation, and catalyst promoters, as well as a discussion of current and future developments in CO2 methanation, are also included.

Due to their large chemically active surface and stability at high temperatures carbon nanotubes (CNTs) have been used as a support material for the dispersion and stabilization of metal and semiconductor nanoparticles (NPs). These hybrid materials have found several applications in catalysis, nanoelectronics, optics, nanobiotechnology, etc. Several ways have been described in the literature to immobilize NPs on CNTs and they can be divided into two main pathways: (a) the formation (and stabilization) of metal NPs directly on the carbon nanotube surface, and (b) the connection of chemically modified NPs to carbon nanotubes or to modified CNTs. A plethora of methods for the synthesis of different NPs have been very recently developed. This know-how is now available for the generation of a large variety of new hybrid products in combination with CNTs. A selection of representative examples of the synthesis, properties and applications of NP–CNTs is here reported and discussed.

Dielectrics represent a new frontier for surface-enhanced Raman scattering. They can serve as either a complement or an alternative to conventional, metal-based SERS, offering key advantages in terms of low invasiveness, reproducibility, versatility, and recyclability. In comparison to metals, dielectric systems and, in particular, semiconductors are characterized by a much greater variety of parameters and properties that can be tailored to achieve enhanced Raman scattering or related effects. Light-trapping and subwavelength-focusing capabilities, morphology-dependent resonances, control of band gap and stoichiometry, size-dependent plasmons and excitons, and charge transfer from semiconductors to molecules and vice versa are a few examples of the manifold opportunities associated with the use of semiconductors as SERS-active materials. This review provides a broad analysis of SERS with dielectrics, encompassing different optical phenomena at the basis of the Raman scattering enhancement and introducing future challenges for light harvesting, vibrational spectroscopy, imaging, and sensing.