Current Opinion in Colloid & Interface Science最新文献

The primary objective of this review is to consolidate our current understanding of the factors controlling the foamability of surfactant solutions under hydrodynamic conditions realized in various laboratory tests. In particular, two regimes of foam generation are considered: at low surfactant concentrations where the coalescence between the bubbles plays a crucial role, and a high surfactant concentration range where the hydrodynamic conditions are much more important for the final outcome of foaming. The review discusses the role of surfactant concentration, dynamic surface coverage, and surface forces acting between film surfaces for the foam generated in the surfactant-poor regime. Additionally, the interplay between the hydrodynamic conditions and the viscosity of the formed foams in the surfactant-rich regime is also discussed.

Ordered porous materials (OPMs) are defined according to pore size, where ordered macropores (>50 nm) govern transport of fluids and mesopores (>2 nm, <50 nm) and micropores (<2 nm, IUPAC definitions) control molecular or ionic interactions. The growing importance of sustainable materials has incentivized the development of biobased OPMs (bioOPMs) with pore sizes ranging from 0.3 nm–9 nm and 1 μm–500 μm. Synthesizing bioOPMs typically involves aqueous solutions and suspensions which require a thorough understanding of biobased precursor-water interactions. Emerging approaches in templating based on liquid foams, breath-figure, and micelles are pivotal for achieving ordered assemblies, with solidity and consolidation occurring through water removal. This review describes recent advances in the design and utilization of bioOPMs, particularly those produced by water-based templating. It also highlights notable exceptions to water-based synthesis and identifies gaps in the science and technology of bioOPMs, offering perspectives on future developments in the field.

This paper reviews the literature on various natural and synthetic biosurfactants, which can facilitate the process of foam formation and stabilisation. Biosurfactants are an alternative to classical surfactants. For example, proteins, through their stabilising properties, can be used both in the food industry and in cosmetics, and this confirms their versatile properties and application in many areas of industry. Sugar-based foaming agents, on the other hand, are characterised by their ability to maintain high foam stability, and their natural origin and biodegradability are attractive substitutes for classical compounds of this type. This review aims to compare the effects of various compounds on the properties and stability of foams. Research on such materials will allow the development of innovative foaming technologies that minimise the negative environmental impacts of foaming compounds without losing the properties of the final product.

Predicting the behavior and fate of redox-sensitive trace elements (TEs; e.g. As, U, Cu, Cr) in natural systems is challenging. Colloids have been reported to control TEs speciation and catalyze TEs redox reactions in many aquatic environments. We hypothesize that the lack of accurate thermodynamic models that account for the role of colloids in TEs speciation explains our inability to predict their redox state distribution in the environment. The slow evolution of the colloidal compartment in response to the prevailing bio/hydro/pedo/climatological conditions need to be decoupled from the fast TEs redox reactions promoted by colloidal surfaces. Further progress is hampered by experimental and theoretical challenges associated with capturing the extreme physical and chemical heterogeneity of colloids, their metastable structures, and their dynamic transformation behavior.

Compared to conventional mesoporous silica nanoparticles (MSNs) with ordered porous structures, hierarchical MSNs (HMSNs) have attracted increasing research interests in biological fields, owing to their highly porous structures with multiple distinct interfaces, which create more possibilities to explore complex biological realms. However, due to the structural complexity, the controllable assembly of HMSNs with desired nanostructures and well-defined particle properties is challenging. Herein, we review the advances of engineering HMSNs via control over surfactant nanoarchitectonics and discuss the synthesis-guiding principles and formation mechanisms. Based on the structural features of HMSNs, the corresponding bio-applications (e.g., macromolecule encapsulation, drug release, biointerface adhesion, immune cell activation and stimuli-responsive target motion) are summarized, highlighting the importance of structure–activity relationship. Challenges and future perspectives are also proposed for characterizations and extended applications of HMSNs.

All personal and industrial cleaning sectors search for environmentally friendly methods to clean contaminated solid surfaces. Having relied for a long time on chemical and physico-chemical means with non-negligible environmental impact, these sectors are increasingly exploring the use of physical phenomena to improve cleaning efficiency. We summarise here recent progress in the area of cleaning methods that exploit the physical properties of liquid interfaces created by liquid menisci, bubbles, drops or foams. The high energy of these interfaces leads to a complex interplay between (1) interfacial forces, (2) viscous stresses created by flow fields under confinement, and (3) the capacity to adsorb solid and liquid contaminations. In appropriately designed cleaning processes, this interplay can reach an astounding efficiency, in many cases even with pure water, i.e. in the absence of any detergent. We will also show that whilst foams have always been assumed to be a mere side product of cleaning processes, recent research puts in evidence that they can actually be highly efficient cleaning agents, provided that their physical properties are properly chosen. We discuss a wide range of examples in which different interface-based cleaning methods have been investigated, including solid and liquid contaminations, or biological contaminations (bacteria, biofilms and biofouling).

Surfactants play an increasingly important role across diverse scientific and industrial domains. Gaining a deeper understanding of their molecular behavior at various interfaces is thus becoming ever more essential. Despite considerable advances in experimental techniques, challenges in capturing the detailed molecular-level behavior of surfactants at interfaces persist. In this work, we discuss the potential of combining various experimental methods with atomistic molecular dynamics (MD) simulations in studies of surfactant interfacial layers. MD simulations have emerged as a powerful tool that provides detailed insights into molecular structures and dynamic properties, some of which are inaccessible through experimental means alone. By re-examining existing MD simulation data and directly comparing them with experiments, we illustrate how MD simulations can be used to validate and support thermodynamic models and interpret spectroscopy and scattering data. While combining scattering experiments on Langmuir layers of insoluble surfactants with simulations seems to be well-established by now, we emphasize the growing capability of scattering techniques to also investigate the more disordered Gibbs layers of soluble surfactants. Here, MD simulations can now connect the pressure and adsorption isotherms with the equation of state. In light of the ongoing parallel developments of computational and experimental methods, their synergistic use can be expected to drive future progress in surfactant research.

Amphiphilic lipids are essential biomolecules, critical components in nature's functional materials, and crucial nutrients in food. Being sustainable, biocompatible, and biodegradable with versatile structural properties, they have great potential as functional building blocks for innovative food materials. They can tailor factors including texture, mouthfeel, appearance, and nutrient delivery. Their structural analysis from the angstrom to the micrometer range lies at the core of the functional material design and is fundamental for their further biological understanding.

We discuss recent advances in colloidal structure formation and challenges in characterizing structures and dynamics in lipid-based materials on the microstructural level. We provide examples of how lipid self-assemblies, particularly lyotropic liquid crystalline structures, can enhance food materials. The interdisciplinary development of this growing research field helps explore new functionalities for food applications.

In this paper, I delve into the physics of foams within the context of Enhanced Oil Recovery (EOR). Foams present a promising prospect for use in EOR, applicable to both conventional and non-conventional oil wells. A primary challenge faced by oil industry technologists is ensuring foam stability in porous media under harsh conditions of temperature, pressure, and salinity. To surmount these challenges, a profound understanding of the physicochemical mechanisms governing foam formation and stability at a microscopic level is required. In this article, I explore some fundamental aspects of foam physics that should be considered when developing foam systems for EOR. I conclude the paper by briefly discussing the use of machine learning in the design of foam-assisted EOR, and by highlighting the potential of smart foams in the oil industry.

Solid particles have been well known to stabilize foams/bubbles by adsorption at gas–liquid interfaces. Synthetic polymer particles are a particularly attractive stabilizer for the foams/bubbles, because their sizes, shapes, surface/bulk chemistries, hydrophilicity-hydrophobicity balance and softness can be tailored and modified by heterogeneous polymerization techniques, (co)polymerizations of functional monomers, polymer reactions and polymer processing. Additionally, a wide range of stimulus-responsive characteristics and film-forming nature of the polymer particles could inspire the design of functional and well-defined particle-stabilized foams/bubbles and materials based on them. This short review overviews aqueous foams/bubbles stabilized solely with synthetic polymer particles and material chemistry based on them, followed by discussions on research directions for the future.