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Tribology and sustainability
\"This book brings a vision of promoting greener, cleaner, and eco-friendly environment highlighting sustainable solutions in tribology via development of self-lubricating materials, green additives in lubricants, natural fiber reinforced materials and biomimetic approaches. Backed by supporting schematic diagrams, data tables and illustrations for easy understanding, it focusses on the recent advancements in tribology and sustainability. Global sustainability and regional requirements are addressed through chapters on natural composites, green lubricants, biomedical and wind energy systems with a dedicated chapter on Global Sustainability Scenario. Features: Highlights sustainability via new tribological approaches and how such methods are essential. Covers theoretical aspects of various tribological topics concerning mechanical and material designs for energy-efficient systems. Includes practical global sustainability based on the regional requirement of tribological research and sustainable impact. Reviews tribology of green lubricants, green additives, and lightweight materials. Discusses topics related to biomimetics and bio-tribology. This book aims at researchers, professionals and graduate students in Tribology, Surface Engineering, Mechanical Design, Materials Engineering, including Mechanical, Aerospace, Chemical and Environmental Engineering\"-- Provided by publisher.
Book
Capturing dynamic ligand-to-metal charge transfer with a long-lived cationic intermediate for anionic redox
Reversible anionic redox reactions represent a transformational change for creating advanced high-energy-density positive-electrode materials for lithium-ion batteries. The activation mechanism of these reactions is frequently linked to ligand-to-metal charge transfer (LMCT) processes, which have not been fully validated experimentally due to the lack of suitable model materials. Here we show that the activation of anionic redox in cation-disordered rock-salt Li
1.17
Ti
0.58
Ni
0.25
O
2
involves a long-lived intermediate Ni
3+/4+
species, which can fully evolve to Ni
2+
during relaxation. Combining electrochemical analysis and spectroscopic techniques, we quantitatively identified that the reduction of this Ni
3+/4+
species goes through a dynamic LMCT process (Ni
3+/4+
–O
2−
→ Ni
2+
–O
n
−
). Our findings provide experimental validation of previous theoretical hypotheses and help to rationalize several peculiarities associated with anionic redox, such as cationic–anionic redox inversion and voltage hysteresis. This work also provides additional guidance for designing high-capacity electrodes by screening appropriate cationic species for mediating LMCT.
Understanding reversible anionic redox reactions is key to designing high-energy-density cathodes for lithium-ion batteries. Anionic redox activation in cation-disordered rock-salt Li
1.17
Ti
0.58
Ni
0.25
O
2
is shown to involve intermediate Ni
3+/4+
species that can evolve to Ni
2+
during relaxation.
Journal Article
Body care chemistry
Chemistry is a big part of our lives. It is thanks to chemistry that we have medicines to treat illness, fuel to power vehicles, clothes to wear, and food to eat. Also thanks to chemistry we have products to look after our bodies, including soap, toothpaste, and shampoo.
Book
Charge transfer driven by ultrafast spin transition in a CoFe Prussian blue analogue
Photoinduced charge-transfer is an important process in nature and technology and is responsible for the emergence of exotic functionalities, such as magnetic order for cyanide-bridged bimetallic coordination networks. Despite its broad interest and intensive developments in chemistry and material sciences, the atomic-scale description of the initial photoinduced process, which couples intermetallic charge-transfer and spin transition, has been debated for decades; it has been beyond reach due to its extreme speed. Here we study this process in a prototype cyanide-bridged CoFe system by femtosecond X-ray and optical absorption spectroscopies, enabling the disentanglement of ultrafast electronic and structural dynamics. Our results demonstrate that it is the spin transition that occurs first on the Co site within ~50 fs, and it is this that drives the subsequent Fe-to-Co charge-transfer within ~200 fs. This study represents a step towards understanding and controlling charge-transfer-based functions using light.Cyanide-bridged CoFe coordination networks exhibit photomagnetism because of coupled charge-transfer and spin transition. Now, femtosecond X-ray and optical absorption spectroscopies have enabled the electronic and structural dynamics of this light-induced process to be disentangled and show that it is the spin transition on the cobalt atom, occurring within ~50 fs, that induces the Fe-to-Co charge-transfer within ~200 fs.
Journal Article
Partial breaking of the Coulombic ordering of ionic liquids confined in carbon nanopores
Ionic liquids are composed of equal quantities of positive and negative ions. In the bulk, electrical neutrality occurs in these liquids due to Coulombic ordering, in which ion shells of alternating charge form around a central ion. Their structure under confinement is far less well understood. This hinders the widespread application of ionic liquids in technological applications. Here we use scattering experiments to resolve the structure of a widely used ionic liquid (EMI–TFSI) when it is confined inside nanoporous carbons. We show that Coulombic ordering reduces when the pores can accommodate only a single layer of ions. Instead, equally charged ion pairs are formed due to the induction of an electric potential of opposite sign in the carbon pore walls. This non-Coulombic ordering is further enhanced in the presence of an applied external electric potential. This finding opens the door for the design of better materials for electrochemical applications.
The structure of ionic liquids under confinement is not well understood and hinders their widespread use for applications. Convincing evidence of partial breaking of Coulombic ordering of ions confined in subnanometre carbon pores is now provided.
Journal Article
Synthesis and Characterization of Nanofunctionalized Gelatin Methacrylate Hydrogels
Given the importance of the extracellular medium during tissue formation, it was wise to develop an artificial structure that mimics the extracellular matrix while having improved physico-chemical properties. That is why the choice was focused on gelatin methacryloyl (GelMA), an inexpensive biocompatible hydrogel. Physicochemical and mechanical properties were improved by the incorporation of nanoparticles developed from two innovative fabrication processes: High shear fluid and low frequencies/high frequencies ultrasounds. Both rapeseed nanoliposomes and nanodroplets were successfully incorporated in the GelMA networks during the photo polymerization process. The impact on polymer microstructure was investigated by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and enzymatic degradation investigations. Mechanical stability and viscoelastic tests were conducted to demonstrate the beneficial effect of the functionalization on GelMA hydrogels. Adding nanoparticles to GelMA improved the surface properties (porosity), tuned swelling, and degradability properties. In addition, we observed that nanoemulsion didn’t change significantly the mechanical properties to shear and compression solicitations, whereas nanoliposome addition decreased Young’s modulus under compression solicitations. Thus, these ways of functionalization allow controlling the design of the material by choosing the type of nanoparticle (nanoliposome or nanoemulsion) in function of the application.
Journal Article
The physical chemistry of materials : energy and environmental applications
\"In recent years, the area dealing with the physical chemistry of materials has become an emerging discipline in materials science that emphasizes the study of materials for chemical, sustainable energy, and pollution abatement applications. Written by an active researcher in this field, Physical Chemistry of Materials: Energy and Environmental Applications presents methods for synthesizing and characterizing adsorbents, ion exchangers, ionic conductors, heterogeneous catalysts, and permeable porous and dense materials. It also discusses their properties and applications. The book explores various examples of these important materials, including perovskites, zeolites, mesoporous molecular sieves, silica, alumina, active carbons, carbon nanotubes, titanium dioxide, magnesium oxide, clays, pillared clays, hydrotalcites, alkali metal titanates, titanium silicates, polymers, and coordination polymers. It shows how the materials are used in adsorption, ion conduction, ion exchange, gas separation, membrane reactors, catalysts, catalysts supports, sensors, pollution abatement, detergency, animal nourishment, agriculture, and sustainable energy applications. Rising pollution levels and the need for sustainable energy have necessitated new ways of using certain materials to combat these problems. Focusing on this emerging discipline, Physical Chemistry of Materials describes the methods of syntheses and characterization of adsorbents, ion exchangers, ionic conductors, catalysts, and permeable materials. It tackles key issues in materials science and physical chemistry.\" -- Back cover.
Book
Regio- and diastereoselective intermolecular 2+2 cycloadditions photocatalysed by quantum dots
Light-driven [2+2] cycloaddition is the most direct strategy to build tetrasubstituted cyclobutanes, core components of many lead compounds for drug development. Significant advances in the chemoselectivity and enantioselectivity of [2+2] photocycloadditions have been made, but exceptional and tunable diastereoselectivity and regioselectivity (head-to-head versus head-to-tail adducts) is required for the synthesis of bioactive molecules. Here we show that colloidal quantum dots serve as visible-light chromophores, photocatalysts and reusable scaffolds for homo- and hetero-intermolecular [2+2] photocycloadditions of 4-vinylbenzoic acid derivatives, including aryl-conjugated alkenes, with up to 98% switchable regioselectivity and 98% diastereoselectivity for the previously minor
syn
-cyclobutane products. Transient absorption spectroscopy confirms that our system demonstrates catalysis triggered by triplet–triplet energy transfer from the quantum dot. The precisely controlled triplet energy levels of the quantum dot photocatalysts facilitate efficient and selective heterocoupling, a major challenge in direct cyclobutane synthesis.
Tuning the selectivity for [2+2] photocycloadditions remains challenging. Now, triplet–triplet energy transfer from CdSe quantum dots enables the homo- and heterocouplings of 4-vinylbenzoic acid derivatives via [2+2] photocycloaddition. Preorganization of substrates on the quantum dots reverses intrinsic stereoelectronic preferences to yield cyclobutane products with unprecedented diastereo- and regioselectivity.
Journal Article