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"Chemical bonds"
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Every molecule tells a story
\"Preface Everything that exists is made of atoms, and most of those substances contain groups of two or more of these bonded together to form molecules. Chemistry is the science of molecules. From cooking to medicine, from engineering to art, it is everywhere\"-- Provided by publisher.
Book
The Chemical Bond
This is the perfect complement to \"Chemical Bonding - Across the Periodic Table\" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemical models and faster computers.
eBook
The nature of the mechanical bond : from molecules to machines
\"The story is told by THE inventor-pioneer-master in the field and is accompanied by amazing illustrations...[it] will become an absolute reference and a best seller in chemistry!\" -- Alberto Credi \"...the great opus on the mechanical bond.A most impressive undertaking!\" -- Jean-Marie Lehn Congratulations to co-author J.
eBook
Stabilizing Buried Interface via Synergistic Effect of Fluorine and Sulfonyl Functional Groups Toward Efficient and Stable Perovskite Solar Cells
HighlightsAn effective buried interface stabilization strategy based on synergistic effect of fluorine and sulfonyl functional groups is proposed.The correlations between molecular structures, defect passivation, interfacial energy band alignment, perovskite crystallization and device performance are established.The device with KFSI achieves an impressive efficiency of 24.17%.The interfacial defects and energy barrier are main reasons for interfacial nonradiative recombination. In addition, poor perovskite crystallization and incomplete conversion of PbI2 to perovskite restrict further enhancement of the photovoltaic performance of the devices using sequential deposition. Herein, a buried interface stabilization strategy that relies on the synergy of fluorine (F) and sulfonyl (S=O) functional groups is proposed. A series of potassium salts containing halide and non-halogen anions are employed to modify SnO2/perovskite buried interface. Multiple chemical bonds including hydrogen bond, coordination bond and ionic bond are realized, which strengthens interfacial contact and defect passivation effect. The chemical interaction between modification molecules and perovskite along with SnO2 heightens incessantly as the number of S=O and F augments. The chemical interaction strength between modifiers and perovskite as well as SnO2 gradually increases with the increase in the number of S=O and F. The defect passivation effect is positively correlated with the chemical interaction strength. The crystallization kinetics is regulated through the compromise between chemical interaction strength and wettability of substrates. Compared with Cl−, all non-halogen anions perform better in crystallization optimization, energy band regulation and defect passivation. The device with potassium bis (fluorosulfonyl) imide achieves a tempting efficiency of 24.17%.
Journal Article
Shedding light on the role of interfacial chemical bond in heterojunction photocatalysis
Faced with the growing consumption of fossil fuels and the consequent energy/ecological crisis, photocatalysis has become a realistic option to develop new energy source and realize the carbon neutrality. Heterojunction photocatalysts constructed by multiple semiconductors with staggered band structure can spatially separate redox reaction sites to realize synergistic oxidation and reduction reactions, and have captured broad interest. However, the undesigned heterojunctions still encounter some headache difficulties, that is the poor interfacial contact, which will block carrier mobility, thus result in inefficient and instable catalysts. Recently, researchers have been focusing on constructing chemical bonds (especially covalent bonding) between different semiconductors to induce the formation of intimate and stable interface contact. Herein, this review article presents the state-of-the-art progress on interfacial chemical bonds (ICB) in heterojunction photocatalysts and clarifies the function mechanism for enhancing photocatalysis. Given that the formation of ICB strongly depends on the surface characteristics of semiconductors, we clarify the formation mechanism and put forward rational design strategies. More importantly, the current photocatalytic applications of ICB are reviewed to have a deep understanding of structure—activity related mechanisms. Finally, our brief outlooks on the current challenges and future development trends of ICB for next-generation photocatalysts are pointed out to create brand-new strategies for optimizing photocatalytic properties and accelerate the practical applications of ICB with high-performance.
Journal Article
Chemical bonding at surfaces and interfaces
Molecular surface science has made enormous progress in the past 30 years.The development can be characterized by a revolution in fundamental knowledge obtained from simple model systems and by an explosion in the number of experimental techniques.
eBook
The Basics of Covalent Bonding in Terms of Energy and Dynamics
We address the paradoxical fact that the concept of a covalent bond, a cornerstone of chemistry which is well resolved computationally by the methods of quantum chemistry, is still the subject of debate, disagreement, and ignorance with respect to its physical origin. Our aim here is to unify two seemingly different explanations: one in terms of energy, the other dynamics. We summarize the mechanistic bonding models and the debate over the last 100 years, with specific applications to the simplest molecules: H2+ and H2. In particular, we focus on the bonding analysis of Hellmann (1933) that was brought into modern form by Ruedenberg (from 1962 on). We and many others have helped verify the validity of the Hellmann–Ruedenberg proposal that a decrease in kinetic energy associated with interatomic delocalization of electron motion is the key to covalent bonding but contrary views, confusion or lack of understanding still abound. In order to resolve this impasse we show that quantum mechanics affords us a complementary dynamical perspective on the bonding mechanism, which agrees with that of Hellmann and Ruedenberg, while providing a direct and unifying view of atomic reactivity, molecule formation and the basic role of the kinetic energy, as well as the important but secondary role of electrostatics, in covalent bonding.
Journal Article
On Structural Rearrangements Near the Glass Transition Temperature in Amorphous Silica
The formation of clusters was analyzed in a topologically disordered network of bonds of amorphous silica (SiO2) based on the Angell model of broken bonds termed configurons. It was shown that a fractal-dimensional configuron phase was formed in the amorphous silica above the glass transition temperature Tg. The glass transition was described in terms of the concepts of configuron percolation theory (CPT) using the Kantor-Webman theorem, which states that the rigidity threshold of an elastic percolating network is identical to the percolation threshold. The account of configuron phase formation above Tg showed that (i) the glass transition was similar in nature to the second-order phase transformations within the Ehrenfest classification and that (ii) although being reversible, it occurred differently when heating through the glass–liquid transition to that when cooling down in the liquid phase via vitrification. In contrast to typical second-order transformations, such as the formation of ferromagnetic or superconducting phases when the more ordered phase is located below the transition threshold, the configuron phase was located above it.
Journal Article
Probing the Nature of Chemical Bonds by Atomic Force Microscopy
The nature of the chemical bond is important in all natural sciences, ranging from biology to chemistry, physics and materials science. The atomic force microscope (AFM) allows to put a single chemical bond on the test bench, probing its strength and angular dependence. We review experimental AFM data, covering precise studies of van-der-Waals-, covalent-, ionic-, metallic- and hydrogen bonds as well as bonds between artificial and natural atoms. Further, we discuss some of the density functional theory calculations that are related to the experimental studies of the chemical bonds. A description of frequency modulation AFM, the most precise AFM method, discusses some of the experimental challenges in measuring bonding forces. In frequency modulation AFM, forces between the tip of an oscillating cantilever change its frequency. Initially, cantilevers were made mainly from silicon. Most of the high precision measurements of bonding strengths by AFM became possible with a technology transfer from the quartz watch technology to AFM by using quartz-based cantilevers (“qPlus force sensors”), briefly described here.
Journal Article