Perfluorooctane sulfonate (PFOS) is an emergent contaminant of substantial environmental concerns, yet very limited information has been available on PFOS adsorption onto mineral surfaces. PFOS ...adsorption onto goethite and silica was investigated by batch adsorption experiments under various solution compositions. Adsorption onto silica was only marginally affected by pH, ionic strength, and calcium concentration, likely due to the dominance of non-electrostatic interactions. In contrast, PFOS uptake by goethite increased significantly at high H
+ and Ca
2+, which was likely due to enhanced electrostatic attraction between the negatively charged PFOS molecules and positively charged goethite surface. The effect of pH was less significant at high ionic strength, likely due to electrical double layer compression. PFOS uptake was reduced at higher ionic strength for a strongly positively charged goethite surface (pH 3), while it increased for a weakly charged surface (pH 7 and 9), which could be attributed to the competition between PFOS-surface electrostatic attraction and PFOS-PFOS electrostatic repulsion. A conceptual model that captures PFOS-surface and PFOS-PFOS electrostatic interactions as well as non-electrostatic interaction was also formulated to understand the effect of solution chemistry on PFOS adsorption onto goethite and silica surfaces.
The ability to directly monitor the states of electrons in modern field-effect devices-for example, imaging local changes in the electrical potential, Fermi level and band structure as a gate voltage ...is applied-could transform our understanding of the physics and function of a device. Here we show that micrometre-scale, angle-resolved photoemission spectroscopy
(microARPES) applied to two-dimensional van der Waals heterostructures
affords this ability. In two-terminal graphene devices, we observe a shift of the Fermi level across the Dirac point, with no detectable change in the dispersion, as a gate voltage is applied. In two-dimensional semiconductor devices, we see the conduction-band edge appear as electrons accumulate, thereby firmly establishing the energy and momentum of the edge. In the case of monolayer tungsten diselenide, we observe that the bandgap is renormalized downwards by several hundreds of millielectronvolts-approaching the exciton energy-as the electrostatic doping increases. Both optical spectroscopy and microARPES can be carried out on a single device, allowing definitive studies of the relationship between gate-controlled electronic and optical properties. The technique provides a powerful way to study not only fundamental semiconductor physics, but also intriguing phenomena such as topological transitions
and many-body spectral reconstructions under electrical control.
Graphically revealing interaction regions in a chemical system enables chemists to quickly recognize where significant interactions have formed. Reduced density gradient (RDG) has already been widely ...employed in literatures to visually exhibit weak interaction regions, in fact it also has the ability of revealing chemical bonding regions. Unfortunately, RDG cannot clearly show both types of the interactions at the same time. In this work, we propose a new real space function named interaction region indicator (IRI), which is a slight modification on RDG. We found IRI can reveal chemical bonding and weak interaction regions equally well, which brings great convenience in the study of various chemical systems as well as chemical reactions. IRI is also compared with atom‐in‐molecules (AIM) topology analysis of electron density, it is demonstrated that IRI has the ability to reveal additional interactions to provide chemists a more complete picture. In addition, we put forward a variant of IRI named IRI‐π, which is dedicated to reveal interactions of π electrons. It is found that IRI‐π can not only distinguish type of π interactions but also exhibit π‐interaction strength. IRI and IRI‐π have been efficiently implemented in our freely available Multiwfn wavefunction analysis code (http://sobereva.com/multiwfn), and are expected to become new useful members of computational chemists′ toolbox in studying chemical problems.
Finding IRI: Interaction region indicator (IRI) is a very simple function able to graphically reveal all kinds of interactions in a chemical system, and its variant IRI‐π is able to distinguish types and exhibit strengths of π‐interactions.
Studying the interactions of biopolymers like polysaccharides and proteins is quite important mainly due to the wide number of applications such as the stabilization and encapsulation of active ...compounds in complex systems. Complexation takes place when materials like proteins and polysaccharides are blended to promote the entrapment of active compounds. The interaction forces between the charged groups in the polymeric chains allow the miscibility of the components in the complex system. Understanding the interactions taking place between the polymers as well as between the wall material and the active compound is important when designing delivery systems. However, some features of the biopolymers like structure, functional groups, or electrical charge as well as extrinsic parameters like pH or ratios might affect the structure and the performance of the complex system when used in encapsulation applications. This work summarizes the recent progress of the polysaccharide/protein complexes for encapsulation and the influence of the pH on the structural modifications during the complexation process.
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•pH is an important parameter that determines the molecular assembly.•The molecular association is due to electrostatic and weaker interactions.•The entrapment can take place by overlaying, inclusion, or a mixed effect of molecules.
In this study, the alginate/chitosan composite aerogels based on electrostatic interactions and noncovalent crosslinking were fabricated using sol-gel method followed by freeze-drying process. The ...solution property results showed that with the addition of chitosan in alginate solution, a tighter network was induced by the more entangled molecular chains. The aerogel morphology observations showed that the pore diameter decreased with the increasing weight ratio of chitosan in the aerogels, but was even much lower after the crosslinking of excess alginate with calcium ions. After crosslinking, the aerogels presented the improved thermal stability and higher mechanical properties, as well as stronger antibacterial activities against Staphylococcus aureus and Escherichia coli. Therefore, the enhanced physical and antimicrobial properties of the alginate/chitosan aerogels may be achieved by modulation of electrostatic interactions and noncovalent crosslinking, suggesting the promising applications of these composite aerogels as active food packaging materials for antimicrobial purpose.
•A tighter network between chitosan and alginate was induced by electrostatic interactions.•The pore diameter of aerogels was much lower after noncovalent crosslinking with calcium ions.•Higher thermal stability, mechanical properties, and antibacterial activities were obtained.
Micellar photocatalysis allows for a simple and benign reaction set‐up using water as the solvent without the need for oxygen‐removing protocols. Blue light (456 nm) is absorbed by the photocatalyst ...and allows the 2+2 photocycloaddition to occur between α,β‐unsaturated carbonyl compounds and activated alkenes. The observed reactivity for α,β‐unsaturated aldehydes is completely turned on by the use of a micellar solution as opposed to organic solvents. More information can be found in the Research Article by L. Næsborg and co‐workers (DOI: 10.1002/chem.202300627).
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•The hydrothermal approach was used to synthesize G-C3N4/RGO/TiO2 nanohybrids.•Using vacuum filtration method nanohybrid materials are coated on PVDF nanofibers membrane.•The ...G-C3N4/RGO-TiO2 coated PVDF membrane displays good pure water flux and antifouling.•The hierarchical structure of G-C3N4/RGO-TiO2 influences the effective separation of dye and oil-water emulsion.
Hierarchical carbon hybrid materials have gained more attention in recent times especially in the separation of pollutants from wastewater. In this study, a novel ternary composite of graphitic carbon nitride (G-C3N4) decorated on reduced graphene oxide (RGO) with titanium dioxide (TiO2) nanohybrids was synthesized using hydrothermal approach to modify the electrospun PVDF membranes for the separation of oil and dye in wastewater. The characteristic functional groups of G-C3N4, RGO and TiO2 (G-C3N4,/RGO/TiO2) nanohybrids were confirmed by X-ray diffraction (XRD) and X-ray photon electron spectroscopy. Moreover, the prepared membranes were also studied using field emission scanning electron microscope and X-ray photoelectron spectroscopy. Interestingly, the PVDF modified membranes displayed excellent thermal stability with lower contact angle, increased surface roughness and surface charges. It was due to the tunable covalent π-π interfaces among G-C3N4 and RGO 2D hierarchical structured nanosheets. Besides due to the reasonable hierarchical structure formation of chemical and physical defense mechanism, the modified membranes exhibited outstanding antifouling performance and different oil water emulsion rejections. The pure water flux for GT-4 membrane was around 1261.2 ± 2 L/m2.h and exhibited high oil water removal efficiency above 95.4 ± 0.1% for different oils. The modified PVDF membranes also exhibited higher rejection rate of about 94.2 ± 0.5% for methylene blue dye removals. These studies confirm the formation of hydration layer and hierarchical structure for membranes which can be employed in oil water emulsion separation and dye rejection studies.
Artificial spin-ice systems are lithographically patterned arrangements of interacting magnetic nanostructures that were introduced as way of investigating the effects of geometric frustration in a ...controlled manner. This approach has enabled unconventional states of matter to be visualized directly in real space, and has triggered research at the frontier between nanomagnetism, statistical thermodynamics and condensed matter physics. Despite efforts to create an artificial realization of the square-ice model-a two-dimensional geometrically frustrated spin-ice system defined on a square lattice-no simple geometry based on arrays of nanomagnets has successfully captured the macroscopically degenerate ground-state manifold of the model. Instead, square lattices of nanomagnets are characterized by a magnetically ordered ground state that consists of local loop configurations with alternating chirality. Here we show that all of the characteristics of the square-ice model are observed in an artificial square-ice system that consists of two sublattices of nanomagnets that are vertically separated by a small distance. The spin configurations we image after demagnetizing our arrays reveal unambiguous signatures of a Coulomb phase and algebraic spin-spin correlations, which are characterized by the presence of 'pinch' points in the associated magnetic structure factor. Local excitations-the classical analogues of magnetic monopoles-are free to evolve in an extensively degenerate, divergence-free vacuum. We thus provide a protocol that could be used to investigate collective magnetic phenomena, including Coulomb phases and the physics of ice-like materials.
Spectral tuning , from green to red, of luciferin's electrochemiluminescence (ECL) is achieved by electrolyte engineering, demonstrating that this does not require a keto/enol isomerization of the ...light emitter. Visual mapping of luciferin's ECL enables a straightforward optical measurement of superoxide diffusivity, as described by Michelle L. Coote, Marco Garavelli, Simone Ciampi et al. in their Research Article (e202209670).
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•Emulsions stabilized by the single emulsifier are susceptible to instability.•Plant polysaccharides have good emulsifying and thickening properties.•Different plant polysaccharides ...have different mechanisms for improving emulsion stability.•The application of plant polysaccharides in emulsions is summarized.
Emulsion is considered to be an excellent system for delivering nutraceuticals, but instability limits the application of the emulsion. Adding stabilizers is an effective method to improve the stability of the emulsion. Due to safety concerns, stabilizers from natural resources are attracting more and more attentions in food industry. Plant polysaccharides are natural biopolymers which are widely distributed in the cells of plants. Many plant polysaccharides have been shown good emulsifying and thickening effects, therefore, they are widely used as stabilizers in emulsions. The application of plant polysaccharides in improving emulsion stability was reviewed in this paper. Firstly, the factors affecting the stability of the emulsion were elaborated in detail. On this basis, the methods of improving the stability of the emulsion were discussed. Furthermore, the effects of the plant polysaccharide structures on emulsion stability were explained, such as the molecular weight of the polysaccharide, the hydrophobic group of the polysaccharide, and the protein content of the polysaccharide. Additionally, the application of several common plant polysaccharides and their derivatives in emulsions were introduced. It is hoped that this review can provide sufficient theoretical basis for application of plant polysaccharides in emulsions in the future.
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