These terms are included in the entropy contribution, and are an important component of the interfacial energy. Solely considering the difference in the interaction energy of atoms at the interface and that of atoms in the bulk due to the difference in the number and the types of neighbouring atoms is inadequate for complex systems with water, salts, and surfactants, because it neglects the degrees of freedom of molecules (vibrations, conformations and orientation), as well as the potential enrichment of some molecules at interfaces as respect as to the bulk. The energy term here is actually the interfacial free energy which is comprised of enthalpic and entropic contributions. IFT is defined either as the energy required to create a unit of interfacial area or the interfacial free energy of two immiscible fluids. temperature, nature and concentration of surface-active compounds. 9–19 However, to fully understand, predict, and manipulate IFT using surfactants more experimental and theoretical work needs to be conducted due to the complex interplay of many different factors e.g. 8ĭue to scientific interest and industrial importance, many studies have been conducted to understand the relation between molecular structure and performance for various surfactants. ![]() 4 One of the most prominent applications is oil production, 5–7 in which case low water/oil IFT is required to lower the capillary force, allowing oil to detach from the rock surfaces. 2,3 In the oil and gas industry, controlling IFT is crucial in many areas. These products require emulsifiers (surface active agents) to reduce the IFT and assist emulsion formation and stabilization. 1 Many food products are emulsions and/or dispersions, for example milk, mayonnaise, and chocolate pastes and syrups. Usually, high performance formulations are those that can induce low surface/interfacial tension, which help in removing stains, fats, and oils from clothing. For example, surface and interfacial tension determine the quality and the efficiency of detergent formulations. 1 Introduction Surface and interfacial tension (IFT) are fundamental concepts, which affect our everyday life and play important roles in many chemical processes and industrial applications. Our results shed light on some of the factors that control IFT and could have important practical implications in industrial applications such as the design of cosmetics, food products, and detergents. ![]() with flexible and/or unsaturated tails) reduce the water/oil IFT more effectively than surfactants which yield highly ordered interfacial films. Our results suggest that surfactants that yield more disordered interfacial films ( e.g. We find that, in addition to reducing direct contact between the two fluids, surfactants serve to increase the disorder at the interface (related to interfacial entropy) and consequently reduce the water/oil IFT, especially when surfactants are present at high surface density. In this study, we present the results from molecular dynamics simulations revealing the specific role surfactants play in IFT. However, the IFT is controlled by an interplay of factors such as temperature and molecular structure of surface-active compounds, which make it difficult to predict IFT as those conditions change. Numerous attempts have been made to relate changes in IFT arising from such compounds to the specific nature of the interface. When low IFT is desired, surface active compounds (e.g. ![]() We conclude by suggesting that in addition to optical spectroscopies, validating the functional role of coherences would require simultaneous mapping of correlated electron motion and atomically resolved nuclear structure.The interfacial tension (IFT) of a fluid–fluid interface plays an important role in a wide range of applications and processes. This includes revisiting the insights from the seminal work on the theory of ET and time-resolved measurements on coherent dynamics to explore the role of coherences in ET reactions. We will discuss how the interplay of basic parameters governing ET reactions-like electronic coupling, interactions with the environment, and intramolecular high-frequency quantum vibrations-impact coherences. A primary motive of this Perspective is to work out how to think about "coherence" in ET reactions. The prevalence of such coherence effects holds a promise to increase the efficiency and robustness of transport even in the face of energetic or structural disorder. The past decade has seen tremendous advances in the possible role of quantum coherent effects in the light-initiated energy and ET processes in chemical, biological, and materials systems. Photoinduced electron transfer (ET) is a cornerstone of energy transduction from light to chemistry.
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