Bulk Stability Research Articles

Semitransparent Organic Photovoltaic Devices: Interface/Bulk Properties and Stability Issues

In the present work, an insight on the morpho/structural properties of semitransparent organic devices for buildings’ integrated photovoltaics is presented, and issues related to interface and bulk stability are addressed. The organic photovoltaic (OPV) cells under investigation are characterized by a blend of PM6:Y6 as a photo-active layer, a ZnO ETL (electron transporting layer), a HTL (hole transporting layer) of HTL-X and a transparent electrode composed by Ag nanowires (AgNWs). The devices’ active nanomaterials, processed as thin films, and their mutual nanoscale interfaces are investigated by a combination of in situ Energy Dispersive X-ray Reflectometry (EDXR) and ex situ Atomic Force Microscopy (AFM), X-ray Diffraction (XRD) and micro-Raman spectroscopy. In order to discriminate among diverse concomitant aging pathways potentially occurring upon working conditions, the effects of different stress factors were investigated: light and temperature. Evidence is gained of an essential structural stability, although an increased roughness at the ZnO/PM6:Y6 interface is deduced by EDXR measurements. On the contrary, an overall stability of the system subjected to thermal stress in the dark was observed, which is a clear indication of the photo-induced origin of the observed degradation phenomenon. Micro-Raman spectroscopy brings light on the origin of such effect, evidencing a photo-oxidation process of the active material in the device, using hygroscopic organic HTL, during continuous illumination in ambient moisture conditions. The process may be also triggered by a photocatalytic role of the ZnO layer. Therefore, an alternative configuration is proposed, where the hygroscopic HTL-X is replaced by the inorganic compound MoOx. The results show that such alternative configuration is stable under light stress (solar simulator), suggesting that the use of Molybdenum Oxide, limiting the photo-oxidation of the bulk PM6:Y6 active material, can prevent the cell from degradation.

Energy-efficient NO2 sensors based on two-dimensional layered 2H-WS2 nanosheets

Layered transition metal dichalcogenides (TMDCs) are considered among the next-generation materials for gas sensing. Here, we report exfoliated 2 H-WS2 nanosheets for the fabrication of highly performing NO2 sensors. Thermal annealing at several temperatures was performed to investigate the oxidation of WS2. The long-term stability of 2 H-WS2 bulk was verified. Using droplet variation method, three batches of conductometric sensors from 2 H-WS2 dispersions were fabricated on electrical transducers, namely two layers (2 L), five layers (5 L) and ten layers (10 L) WS2 nanosheets. These sensors were tested towards low NO2 concentrations at different temperatures (Room Temperature (20 ℃), 50 ℃ and 100 ℃) and relative humidity (RH) levels (20%, 40%, 60%, 80% and 90% RH). 2 L-WS2 based sensor showed the highest response at room temperature (RT). Excellent repeatability (4 cycles) towards 1 ppm NO2 and long-term stability (more than two months) were achieved. Full selectivity towards NO2 (1 ppm) at RT was observed over NH3 (15 ppm), H2S (15 ppm), ethanol (30 ppm) and acetone (30 ppm). Our results confirm that low-power consumption devices with high sensitivity (even at high RH), long-term stability and excellent selectivity towards NO2 were fabricated using 2 H-WS2 nanosheets.

Density functional theory-based modeling of the half-metallic g-C3N4/CoN4 heterojunction for photocatalytic water splitting reaction.

Using density functional theory (DFT), we have investigated the structural, optical, electronic and magnetic properties of a graphitic carbon nitride (g-C3N4) and CoN4 composite to explore the effect of the heterojunction on the photocatalytic performance of g-C3N4. The structure of g-C3N4 is modified while complexing with CoN4 and the corresponding stabilization is confirmed through adhesion energy calculation. The phonon spectra analysis furthermore guaranteed the lattice-dynamic stability of the CoN4 bulk and the CoN4 slab. Pristine g-C3N4 is a wide band gap semiconductor, which becomes half metallic upon CoN4 inclusion. The metallicity in the g-C3N4/CoN4 composite originates from the spin down channel, keeping the spin up channel in a semiconducting state. The charge density analysis and work function calculation suggest a substantial amount of charge transfer from g-C3N4 to the CoN4 unit in the g-C3N4/CoN4 heterojunction. The model heterojunction of the g-C3N4/CoN4 composite can enhance the utilization ratio of visible light for the g-C3N4 photocatalyst. In g-C3N4/CoN4, the valence band maximum (VBM) has a more positive potential compared to O2/H2O (+1.23 V) on the normal hydrogen electrode (NHE) scale. However, the conduction band minimum (CBM) displays a more negative potential compared to H+/H2 (0 V) on the NHE scale. The details of the band structure, density of states and band edge position determining calculations confirm that the g-C3N4/CoN4 composite forms a type 1 heterojunction, making it a suitable photocatalyst for water splitting reaction. The practical application of the g-C3N4/CoN4 heterostructure as a photocatalyst was substantiated in the presence of polar solvent (water) by calculating the band gap, charge transfer interaction and charge density difference. There is a significant decrease of charge transfer and thereby charge density difference in the g-C3N4/CoN4 heterojunction in the presence of water; however, it still holds potential for use as a photocatalyst for water splitting reaction. The state-of-the-art theoretical modeling of the g-C3N4/CoN4 heterojunction is the first theoretical study incorporating the CoN4 crystal.

Rational design of nanoscale stabilized oxide catalysts for OER with OC22.

The efficiency of H2 production via water electrolysis is limited by the sluggish oxygen evolution reaction (OER). As such, significant emphasis has been placed upon improving the rate of OER through the anode catalyst. More recently, the Open Catalyst 2022 (OC22) framework has provided a large dataset of density functional theory (DFT) calculations for OER intermediates on the surfaces of oxides. When coupled with state-of-the-art graph neural network models, total energy predictions can be achieved with a mean absolute error as low as 0.22 eV. In this work, we interpolated a database of the total energy predictions for all slabs and OER surface intermediates for 4119 oxide materials in the original OC22 dataset using pre-trained models from the OC22 framework. This database includes all terminations of all facets up to a maximum Miller index of 1. To demonstrate the full utility of this database, we constructed a flexible screening framework to identify viable candidate anode catalysts for OER under varying reaction conditions for bulk, surface, and nanoscale Pourbaix stability as well as material cost, overpotential, and metastability. From our assessment, we were able to identify 122 and 68 viable candidates for OER under the bulk and nanoscale regime, respectively.

Why alloying with noble metals does not decrease the oxidation of platinum: a DFT-based ab initio thermo-dynamics study.

Despite its well-known nobility, even platinum is subject to corrosion under the harsh conditions that many technical applications require. Based on the assumption that the platinum loss is mainly caused by the formation of volatile PtO2, alloying is a promising strategy to reduce it. This investigation explores the bulk stability of Pt-Au, Pt-Ir, Pt-Re, Pt-W, Pt-Ag, Pt-Rh, Pt-Cu, Pt-Ni and Pt-Co, as well as their oxides, utilizing density functional theory, as well as ab initio and literature thermodynamic data. The alloy model combines special-quasi random structures with thermodynamic properties interpolated from the constituting metals, which are complemented by the configuration entropy. The results suggest that reducing platinum oxidation by alloying decreases the overall nobility of the alloy, since platinum- and oxygen affinity of the alloying metal are related to each other. Despite this limitation, copper was identified as a promising candidate for stabilizing the platinum catalyst in the Ostwald process.

Co-intercalation strategy for simultaneously boosting two-electron conversion and bulk stabilization of Mn-based cathodes in aqueous zinc-ion batteries

The proposed cathode, achieved by a cost-effective and scalable coating process, highlights the potential of simultaneously promoting surface reactivity while ensuring bulk stability for efficient high mass loading cathodes in zinc-ion batteries.

Simultaneously promoting the surface/bulk structural stability of Fe/Mn-based layered cathode for sodium ion batteries

Layered sodium iron manganese oxide cathodes have attracted great interest owing to their high specific capacity and cost-effective metal resources, while the detrimental phase transitions and surface structural degradation severely limit their commercial applications. In this work, the bulk and surface structure stability of a P2-Na0.67Fe0.5Mn0.5O2 cathode can be synergically enhanced by a one-step Li/Nb co-doping strategy. Structural characterizations reveal that Li doping promotes the formation of P2/O3 biphasic structure and makes the unfavorable P2-OP4 phase transition convert into a smooth solid-solution reaction. Nb doping enhances the mobility of sodium ions and forms strong Nb-O bonds, thereby enhancing the stability of the TMO2 layer structure. In particular, the Nb element induces the surface reorganization of an atomic-scale NaNbO3 coating layer, which could effectively prevent the dissolution of metals and surface side reactions. The synergistic mechanism of enhanced electrochemical performance is proved by multiple characterizations during cycling. As a result, the as-prepared Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 exhibits improved capacity retention of 85.4 % than raw material (45.7 %) after 100 cycles at 0.5C (1C = 174 mA g−1) within 2.0–4.0 V. This co-regulating strategy provides a promising approach to designing highly stable sodium-ion battery cathodes. Furthermore, a full cell of Na0.67Li0.1Fe0.5Mn0.38Nb0.02O2 with hard carbon displays excellent cycling stability (85.1 % capacity retention after 100 cycles), making its commercial operation possible. This synergistic strategy of biphasic structure and surface reorganization is a critical route to accelerate the application of layer oxide cathodes.

Dirac solitons and topological edge states in the β-Fermi-Pasta-Ulam-Tsingou dimer lattice.

We consider a dimer lattice of the Fermi-Pasta-Ulam-Tsingou (FPUT) type, where alternating linear couplings have a controllably small difference and the cubic nonlinearity (β-FPUT) is the same for all interaction pairs. We use a weakly nonlinear formal reduction within the lattice band gap to obtain a continuum, nonlinear Dirac-type system. We derive the Dirac soliton profiles and the model's conservation laws analytically. We then examine the cases of the semi-infinite and the finite domains and illustrate how the soliton solutions of the bulk problem can be glued to the boundaries for different types of boundary conditions. We thus explain the existence of various kinds of nonlinear edge states in the system, of which only one leads to the standard topological edge states observed in the linear limit. We finally examine the stability of bulk and edge states and verify them through direct numerical simulations, in which we observe a solitonlike wave setting into motion due to the instability.

A Comparative Study of Fourier Transform Near-Infrared Spectroscopy and Physicochemical Methods in Wheat Quality Analysis

Near-infrared spectroscopy is a non-invasive, rapid, and efficient analytical method widely employed in agricultural quality assessment. This study aims to explore the potential of Fourier transform near-infrared (FT-NIR) spectroscopy in the analysis of wheat quality in comparison to traditional physicochemical methods. Key quality parameters such as protein content, bulk density, dough extensibility, development and stability time, wet gluten, and extension area were considered. To compare the similarities between the two methods in an irregular manner and to make the trials more representative, randomized combinations of different samples were made by planting different wheat genotypes in different locations. In wheat protein determination (r = 0.92, p < 0.001), the correlation between protein determinations was very high and highly statistically significant. This indicates that the Fourier transform near-infrared (FT-NIR) assay is highly consistent and accurate with the physicochemical method for protein determination. In the quality indices of bulk density (r = 0.46, p < 0.05), dough extensibility (r = 0.46, p < 0.05), development time (r = 0.37, p < 0.05), stability time (r = 0.49, p < 0.01), wet gluten (r = 0.54, p < 0.01), and dough extension area (r = 0.63, p < 0.001), there was a positive correlation between the two assays. Although the correlation was lower compared to the protein assay, it was still statistically significant. This suggests that the FT-NIR assay also has some accuracy in these indices, although there may be some differences from the physicochemical method. Through comparative analysis, we found that in wheat quality assessment, FT-NIR showed a strong correlation and was highly significant in the determination of wheat protein content; in the determination of the extension area, although highly significant, the correlation coefficient was not high, and there was a positive correlation between the two, and a lower correlation was shown in the bulk density, dough extensibility, and development time. These results indicate that FT-NIR can assess the wheat protein content quality indicator. However, its ability to accurately assess wheat quality indicators such as density, dough extensibility, development and stability time, wet gluten, and dough extensibility needs further investigation.

Stratification and temporal evolution of mixing regimes in diurnally heated river flows

Direct numerical simulations of stratified open channel flows subject to a varying surface heat flux are performed. The influence of the diurnal heating time on the spatial and temporal variation of mixing in the flow and the characteristics of the mean flow state are examined. The control parameters are the bulk stability parameter lambda_{B}, defined through the ratio of the channel height delta and a bulk Obukhov length scale mathscr{L}_{B}, and the diurnal time scale hat{t}, defined as the ratio of the heating time to an eddy turnover time. The Prandtl number Pr and Reynolds number Re_{tau} have values of 1 and 400. Simulations are performed over hat{t} = 1 to 24 and lambda_{B} = 0.6 to 26. Two key flow features are used to classify the flow regimes observed, namely the laminar layer depth (LLD) and stratified layer depth (SLD) where the LLD is defined as the depth from the free surface when the buoyancy Reynolds number Re_{B} approx 7 and the SLD is the depth from the free surface when the turbulent Froude number Fr approx 1. This study attempts to characterise how these length scales vary across the diel cycle. The LLD is a viscous length scale and a regime map of a viscous parameter, the bulk Obhukov Reynolds number Re_mathscr{L}, and hat{t} is presented to classify the LLD behaviour. A regime map of lambda _{B} and hat{t} is presented to classify the behaviour of the SLD. Three classifications for each layer depth behaviour within a diel cycle form the basis of the regime maps for this paper: a neutral flow where the LLD or SLD does not exist (denoted by NL and NS), a stratified flow where the LLD or SLD are diurnally varying (denoted as DL and DS) and a persistent layer of the LLD or SLD (denoted as PL and PS). The transition between the NL to DL is hat{t} propto Re_{mathscr{L}}^{4.5}, DL to PL is hat{t} propto Re_{mathscr{L}}^{- 0.5}, NS to DS is hat{t} propto lambda _{B}^{0} and DS to PS is hat{t} propto lambda _{B}^{1}. The regime maps may be used as a predictive tool to determine when suppressed mixing regimes occur in rivers. At each flow depth, the flow sweeps though a range of mixing states across the diel cycle. The local mixing efficiency are briefly assessed and found to scale well with the instantaneous Fr number according to the regimes proposed by Garanaik and Venayagamoorthy (J. Fluid Mech., vol. 867, 2019, pp. 323-333).

Fabrication and Characterization of Novel Food-Grade Bigels Based on Interfacial and Bulk Stabilization.

Novel food-grade bigels were fabricated using zein nanoparticles for interfacial stabilization and non-surfactant gelators (beeswax and tapioca) for bulk stabilization. The present study demonstrated the importance of interfacial stability for biphasic gels and sheds light on the roles of the gelation mechanism and the oil/water ratio of a bigel on its microstructure, physical properties, and digestion behaviors. The results indicated that it is not an easy task to realize homogenization and subsequent gelation in beeswax-tapioca biphasic systems, as no amphiphilic components existed. However, applying the binding of zein nanoparticles at the oil-water interface allowed us to produce a homogeneous and stable bigel (oil fraction reach 40%), which exhibited enhanced structural and functional properties. Oleogel structures play a crucial role in determining the deformation response of bigel systems. As the oil content increased, the mechanical strength and elastic properties of bigels were enhanced. In the meantime, clear bigel-type transitions were observed. In addition, the fabricated bigels were shown to be beneficial for delayed digestion, and the lowest degree of lipolysis could be found in bigel with 50% oleogel.

One‐Step Sintering Synthesis Achieving Multiple Structure Modulations for High‐Voltage LiCoO2

AbstractThe structure instability issues of the highly delithiated LiCoO2 have significantly hindered its high‐voltage applications (≥4.55 V vs Li/Li+). Herein, for the first time, multiple modifications of Li0.9Mg0.05CoO2 (L0.9M0.05CO) via a simple one‐step sintering synthesis are reported. A combination of the bulk Li/Co antisites, a Mg‐pillar enriched surface, and a thin MgO coating layer is achieved to maintain both the bulk and surface structural stability of L0.9M0.05CO upon cycling at an upper cut‐off voltage of 4.6 V. The bulk Li/Co antisites are discovered to enhance the H1‐3 phase evolution reversibility, the Mg pillars that substitute the Li sites effectively reinforces the surface structure, and the thin MgO coating layer can effectively prevent the cathode from severe side reactions. Benefiting from the reduced but reversible H1‐3 phase transition and the reinforced surface structure, L0.9M0.05CO shows an excellent cycle stability. This work provides a new structure modulation route for developing high‐voltage LiCoO2 cathodes.

Lignin-Based Hydrogel Reinforced Dry Water as Inhibitor for Coal Spontaneous Combustion

ABSTRACT Dry water is a green fire extinguisher agent with good cooling and fluidity that is composed of hydrophobic silica and tiny liquid droplets. However, the structure of dry water is unstable and easily broken during production, transportation and storage. In this study, a lignin-based hydrogel was employed as the core material and hydrophobic silica as the wall material to develop a hydrogel reinforced dry water suitable for preventing coal spontaneous combustion. The bulk density, fluidity, stability and particle size distribution of the synthesized hydrogel reinforced dry water were all measured. Compared to traditional dry water, the lignin-based hydrogel reinforced dry water had a better angle of repose and outflow velocity, measuring 19.53° and 9.40 mL/s, respectively. Additionally, the bulk density and water retention in an open environment were 2.6% and 5.2% higher than traditional dry water, respectively. The particle size distribution of the lignin-based hydrogel reinforced dry water is likewise more uniform. Thermal analysis was used to examine the effect of the reinforced dry water on coal oxidation. The results showed that the reinforced dry water reduced the mass increase caused on by oxygen adsorption, hence inhibiting coal oxygen chemisorption. Further investigation revealed that addition of reinforced dry water improved the inhibitory performance of coal spontaneous combustion by decreasing coal oxidation heat release by 4.2% and 11.2%, respectively, in comparison to raw PING and YZ coal, and by increasing coal oxidation activation energy, with maximum increases of 23 and 265 kJ/mol for PING and YZ, respectively.

Oleofoams stabilized by monoacylglycerides: Impact of chain length and concentration

Oleofoams are plant oil based whipped systems which have drawn academic and industry attention in recent years. The aim of this study was to determine the effect of fatty acid chain length and monoacylglyceride (MAG) concentration on the performance and structural properties of MAG-based oleofoams. Four different MAGs (monolaurin, monomyrystin, monopalmitin, and monostearin) were studied at three concentration levels (5, 10, and 15 wt%). The fatty acid chain length had a statistically significant impact on the size and shape of crystals formed, while higher MAG concentrations led to higher numbers of crystals in the continuous oil phase. These differences affected the performance and physical properties of the oleofoams: compared to other MAGs, monostearin based oleofoams were harder and exhibited higher values of G′ and G″, had higher overrun and showed better stability. Lastly, through microscopy techniques it was successfully proved that monostearin-based oleofoams are stabilized by both bulk and Pickering stabilization.

Spirulina platensis protein nanoparticle-based bigels: Dual stabilization, phase inversion, and 3D printing

Nanoparticle-based bigel is a miscellaneous emulsion system consisting of two immiscible gels, combining Pickering and bigel mechanism, which resulted in enhanced technological and functional outputs. The edible Spirulina platensis protein nanoparticle (SPNP)-based bigel with double network structure was prepared by homogenizing a hydrogel and an oleogel made from xanthan gum (XG) and sunflower wax (SW), respectively. Increasing oleogel/hydrogel (OG/HG) ratio led to phase inversion from O/W to W/O bigels as OG fraction ranged from 54 wt% to 60wt%. XG network existed between oil droplets of O/W bigels and in the internal phase of W/O bigels, and SPNPs were adsorbed at W–O interfaces of all types of bigels (O/W, semibicontinuous, and W/O). Due to bigel formation depending on non-covalent interactions, it was summarized into a dual stability mechanism, both bigel and Pickering emulsion, combining interfacial and bulk stabilization in one system. These bigels displayed more superior to those bigels consisting of wax-based oleogel since the ideal printability regardless of only 5 wt% SW in OG. Owing to the effect of nozzle shearing of bigels after extrusion, all bigel inks showed a slight gather in the same phase and a significant decrease in hardness, springiness, cohesiveness, and gumminess after 3D printing, respectively. This study opens avenues for rationally designing novel plant-based products and offers a novel approach for the application of bigels as saturated fat replacers.

Experimental study on the in-situ foam performance stabilized by microbial polysaccharide and its diverting characteristics at high temperature

Foam fluid shows good performance as diverting agent for reservoir stimulation, but complex generation procedure and high flow friction restrict its further application especially in offshore fields. To overcome these limitations, the objective of this study is to create stable in-situ foam system and investigate its potential in diverting fluid in heterogeneous reservoirs at high temperature. To prepare in-situ foam system, self-generated gas system was analyzed in terms of gas production volume and production efficiency. Foaming agents and foam stabilizers were optimized at the temperatures ranging from 70 ℃ to 90 ℃. Then in-situ foaming performance of the system combining self-generated gas reactants (sodium nitrite and ammonium chloride), the foaming agent (alpha olefin sulfonate), and the foam stabilizer (diutan gum) without blender was investigated based on foaming volume and bulk stability. Single core and parallel core flooding experiments were applied to investigate the plugging ability and diverting characteristics of in-situ foam. The results showed that the large pore volume was blocked by in-situ foam even at 150 ℃ as shown by the increase of residual resistance factor during subsequent water flooding. Parallel core flooding experiments also proved the diverting ability of in-situ foams as the diversion ratio of low-permeability core was higher than that of high-permeability core during subsequent water flooding. Moreover, the diversion performance of in-situ foam strongly depended on the permeability contrast, environment temperature, permeability of low-permeability core, and injection rate. Although diversion failed when permeability contrast was more than 10, in-situ foam also had good thermal stability and diverting ability at 150 ℃ in the permeability contrast range of 3 to 8. Such stable in-situ foam shows promising potential as diverting agent in heterogeneous formation for reservoir stimulation at high temperature.

THE EFFECTS OF PARTICLE SIZE AND TEMPERATURE ON THE STABILITY AND LOCAL STRUCTURAL EVOLUTIONS OF AMORPHOUS BULK AND NANOPARTICLES OF THE FeNI3 ALLOYS

The effects of particle size (2-6 nm) and temperature (300-1900 K) on the stability and local structural evolutions of amorphous bulk and nanoparticles of the FeNi3 alloys have been studied by using classical molecular dynamics (MD) simulation method combined with embedded atom model (EAM) in Largescale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The nanoparticles were obtained from the unstable amorphous bulk FeNi3 alloys. MD simulations have been performed for glassy FeNi3 intermetallic alloy by making use of pairwise interatomic interaction potentials and electron densities calculated via EAM method. The formation and evolution of structures and their stability have been analyzed at a wide temperature range (300-1900 K) by calculating radial distribution functions (RDF), interatomic distances (ID), coordination numbers (CN), core-to-surface concentration profiles, as well as Voronoi analysis. According to the results, although some deviations in the structural properties occurred during the heat treatment, the amorphous nanoparticles exhibited the same crystal structure and local atomic configuration with its bulk counterpart at room temperature.

Isolation and Screening of Amylase Producing Bacteria from Soil and Production of Amylase

Amylase falls under class of hydrolytic enzymes catalysing breakdown of starch into monosaccharide units. There are various biological sources of enzymes viz. plants, fungi and bacteria. But the preferred one is microbial source due to ease of bulk production and stability of enzymes to work at extreme environmental conditions. This study reports isolation of amylase producing bacteria from sorghum cultivated farm soil and using them for production of amylase enzyme. During the course of the study three isolates viz. AP- 1, AP-2 and AP-3 were obtained which were identified as Bacillus cereus, Bacillus alvei and Bacillus licheniformis, respectively on the basis of morphological and biochemical characters. Amongst three isolates highest yield was obtained from Bacillus alvei which was 17.6 U/ml. Optimum conditions of pH, temperature and substrate concentration were determined for enzymatic activity. Crude enzyme samples obtained from all three isolates found to work best at 1.5% starch concentration and slightly acidic to neutral pH. The enzyme produced by B. alvei and B. cereus was found to be thermostable working best at 50 oC. In view of applications and demands of amylases in various fields further extension of study is needed for qualitative and quantitative enhancements

Interfacial characterization of an oxidative pickering emulsion stabilized by polysaccharides/polyphenol complex nanogels via a multiscale study

Incorporating antioxidants into the soft colloidal emulsifiers has been necessarily required to prepare antioxidant Pickering emulsions. Establishing interfacial properties-physical and chemical properties relationships has not been deeply explored by a comprehensive multiscale approach. Herein, the polysaccharide composite nanoparticles acted as antioxidants interface-anchored reservoirs were designed via non-covalent interaction between hydroxypropyl chitosan (HPCS), sodium alginate (Alg) and purple corn bracts anthocyanins (PCBA) at the molecular level. The orderly packing HPCS-Alg/PCBA composite nanoparticles formed the more highly-dense adsorption layers at oil/water interfaces at the microscopic level. With increasing the PCBA concentration, the bridged network particle aggregates between neighboring droplets resulted in a smaller size at the mesoscopic level and higher bulk stability at the macroscopic level. Interestingly, the bridged structures formed stronger antioxidant shells around dispersed droplets, further improving oxidative stability. These results highlighted the characteristics of the interfacial layers (thickness, strength, and viscoelasticity) that could be engineered to regulate the oxidation stability of Pickering emulsions at different scales. Therefore, this work proposed a novel strategy to protect lipid droplets of emulsions via manipulating the antioxidative soft colloidal particle's interfacial properties in the Pickering emulsions system, further extending the applications of antioxidant Pickering emulsions in food colloidal fields.

Single Metal Atoms Embedded in the Surface of Pt Nanocatalysts: The Effect of Temperature and Hydrogen Pressure

Embedding energetically stable single metal atoms in the surface of Pt nanocatalysts exposed to varied temperature (T) and hydrogen pressure (P) could open up new possibilities in selective and dynamical engineering of alloyed Pt catalysts, particularly interesting for hydrogenation reactions. In this work, an environmental segregation energy model is developed to predict the stability and the surface composition evolution of 24 Metal M-promoted Pt surfaces (with M: Cu, Ag, Au, Ni, Pd, Co, Rh and Ir) under varied T and P. Counterintuitive to expectations, the results show that the more reactive alloy component (i.e., the one forming the strongest chemical bond with the hydrogen) is not the one that segregates to the surface. Moreover, using DFT-based Multi-Scaled Reconstruction (MSR) method and by extrapolation of M-promoted Pt nanoparticles (NPs), the shape dynamics of M-Pt are investigated under the same ranges of T and P. The results show that under low hydrogen pressure and high temperature ranges, Ag and Au—single atoms (and Cu to a less extent) are energetically stable on the surface of truncated octahedral and/or cuboctahedral shaped NPs. This indicated that coinage single-atoms might be used to tune the catalytic properties of Pt surface under hydrogen media. In contrast, bulk stability within wide range of temperature and pressure is predicted for all other M-single atoms, which might act as bulk promoters. This work provides insightful guides and understandings of M-promoted Pt NPs by predicting both the evolution of the shape and the surface compositions under reaction gas condition.