Colloidal Surface Research Articles

Self‐Generated Ions Modify the Pair Interaction and the Phase Separation of Chemically Active Colloids

Chemically active colloids that release/consume ions are an important class of active matter, and exhibit interesting collective behaviors such as phase separation, swarming, and waves. Key to these behaviors is the pair‐wise interactions mediated by the concentration gradient of self‐generated ions. This interaction is often simplified as a pair‐wise force decaying at 1/r2, where r is the interparticle distance. Here, we show that this simplification fails for isotropic and immotile active colloids with net ion production, such as Ag colloids in H2O2. Specifically, the production of ions on the surface of the Ag colloids increases the local ion concentration, c, and attenuates the pair‐wise interaction force that scales with ∇c/c. As a result, the attractive force between an Ag colloid and its neighbor (active or passive) decays at 1/r or 1/r2 for small or large r, respectively. In a population, the attraction of a colloid by a growing cluster also scales with ∇c/c, so that medium‐sized clusters grow fastest, and that the cluster coarsening slows with time. These results, supported by finite element and Brownian dynamic simulations, highlight the important role of self‐generated ions in shaping the collective behavior of chemically active colloids.

Group‐VA Doped ZnO Injection Layer for Bright and Efficient Perovskite Light‐Emitting Diodes

AbstractHeteroatom doping of the ZnO electron injection layer (EIL) is widely applied to the fabrication of high‐performance quantum‐dot and perovskite light‐emitting diodes (PeLEDs), while group‐VA atomic dopant is rarely studied. Here, VA bismuth (Bi) with strong metallicity is screened as a substitution dopant to regulate the colloid size, surface terminal, and defect density of the ZnO precursor. The as‐fabricated Bi‐doped ZnO (ZnBiO) EIL shows enhanced conductivity, passivated trap states, more n‐type nature, and appropriate band alignment with FAPbI3 (FA: formamidinium), contributing to smooth injection paths with minimal transport losses. Promoted by inhibited hydroxyl terminations of ZnBiO, the FAPbI3 crystals grown into flat nanocylinder domains with higher crystallinity and area‐thickness ratio, leading to a champion PeLED efficiency of 22.3%, a high near‐infrared radiance of 684 W sr−1 m−2, and nearly an order of magnitude extended operational stability, which shows great promise of ZnBiO as the optimal EIL for various LED application scenarios beyond classical ZnMgO.

Impact of the Interfacial Kapitza Resistance on Colloidal Thermophoresis.

Thermal gradients impart thermophoretic forces on colloidal particles, pushing colloids toward cold or hot regions, a phenomenon called thermophoresis. Current theoretical approaches relate the Soret coefficient to local changes in the interfacial tension around the colloid, which lead to fluid flow around the colloid surface. The Kapitza resistance, a key variable in the description of interfacial heat transport, is an experimentally accessible property that modifies interfacial thermal fields. Here, we introduce a theoretical approach that describes colloid thermophoretic forces by incorporating explicitly Kapitza resistance effects. Our formulation can be used to monitor the dependence of thermophoresis on interfacial thermal resistance. We show that the resistance modifies the thermal field around the colloids and identify experimental conditions where the Kapitza resistance influences the thermophoretic forces. We validate our theoretical approach by implementing a nonequilibrium molecular dynamics model of a colloid suspended in a solvent.

Chiral, Topological, and Knotted Colloids in Liquid Crystals

The geometric shape, symmetry, and topology of colloidal particles often allow for controlling colloidal phase behavior and physical properties of these soft matter systems. In liquid crystalline dispersions, colloidal particles with low symmetry and nontrivial topology of surface confinement are of particular interest, including surfaces shaped as handlebodies, spirals, knots, multi-component links, and so on. These types of colloidal surfaces induce topologically nontrivial three-dimensional director field configurations and topological defects. Director switching by electric fields, laser tweezing of defects, and local photo-thermal melting of the liquid crystal host medium promote transformations among many stable and metastable particle-induced director configurations that can be revealed by means of direct label-free three-dimensional nonlinear optical imaging. The interplay between topologies of colloidal surfaces, director fields, and defects is found to show a number of unexpected features, such as knotting and linking of line defects, often uniquely arising from the nonpolar nature of the nematic director field. This review article highlights fascinating examples of new physical behavior arising from the interplay of nematic molecular order and both chiral symmetry and topology of colloidal inclusions within the nematic host. Furthermore, the article concludes with a brief discussion of how these findings may lay the groundwork for new types of topology-dictated self-assembly in soft condensed matter leading to novel mesostructured composite materials, as well as for experimental insights into the pure-math aspects of low-dimensional topology.

A simple, rapid, and low-cost approach for colloidal nanoparticle-based Surface Enhanced Raman Scattering detection of endosulfan pesticide at trace levels

A simple, rapid, and low-cost approach for colloidal nanoparticle-based Surface Enhanced Raman Scattering detection of endosulfan pesticide at trace levels

Modeling of Electric Double Layer to Analyze Reaction Kinetics

Electric double layers (EDLs) play a fundamental role in various electrochemical processes such as colloid dispersion, surface charging, and charge-transfer reactions. Increasingly, the role of EDLs on reaction kinetics is being studied (1). Despite the extensive history of EDL modeling, there remain challenges in accurate prediction of its structure. The characteristic length of EDL (nanometer scale) exceeds the grasp of typical ab-initio molecular-dynamic simulations in order to capture a whole picture of the statistical equilibrium. While continuum models offer a means to estimate the thermodynamic equilibrium of EDLs with substantially lower computational cost than molecular dynamics, state–of-the-art continuum models require parameter fitting(2) due to the lack of appropriate expressions for microscopic interactions.Herein, we propose a predictive multiscale continuum model of EDL that eliminates the empirical fitting and relies more on physical relations. This model computes the distribution of the electrostatic potential, electron density, and species’ concentrations by minimizing the total grand potential of the system. The grand potential is calculated from entropic energy, electrostatic energy, electron energy, solute-solute interactions, and electrode-solute interactions. These energy expressions include not only the terms from previous work(2), but also the microscopic interactions that are newly introduced in this work: polarization of hydration shells, electrostatic interaction in parallel plane toward the electrode, and ion-size-dependent entropy. The parameters that identify the electrode and electrolyte materials are obtained from independent experiments such as vacuum work function, bulk modulus, X-ray diffraction, and concentration-dependent dielectric constant. The developed model reproduces the trends in the experimental differential capacitance with multiple electrode and electrolyte materials (Ag (111)-NaF, Ag (111)-NaClO4, and Hg-NaF), which verifies the accuracy and predictiveness of the model in a system without significant specific electrode-electrolyte interactions. The difference in the capacitance between mercury and silver electrode was attributed to the difference in the electron stability in the metal that is parameterized from the material’s bulk modulus. Finally, extension of the model to systems with specific electrode-electrolyte interactions (e.g., Pt (111)-NaClO4) and the analysis of reaction kinetics will be introduced. Overall, the model framework and findings will provide insights into the EDL structures and guidance on how to tailor electrode-electrolyte interface for improved reaction kinetics. Acknowledgements: This work was partially supported by the Hydrogen and Fuel Cell Technologies Office (HFTO), Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE) through the Million Mile Fuel Cell Truck (M2FCT) consortia, technology managers G. Kleen and D. Papageorgopoulos, under contract number DE-AC02- 05CH11231, as well as by a CRADA with Toyota Central R&D Labs., Inc. and by the Center for Ionomer-based Water Electrolysis (CIWE), a DOE Energy Earthshot Research Center. Reference: S. J. Shin, D. H. Kim, G. Bae, S. Ringe, H. Choi, H. K. Lim, C. H. Choi and H. Kim, Nat Commun, 13, 174 (2022).J. Huang, J Chem Theory Comput, 19, 1003 (2023).

Critical adsorption and charge reversal in polyelectrolyte solutions: Analytical mean-field theory.

An analytical linearized mean-field theory is presented to describe the adsorption behavior of polyelectrolytes near charged colloidal surfaces with additional short-ranged non-electrostatic interactions. The coupling between the polyelectrolyte segment density and electrostatic potential is explicitly accounted for in a self-consistent manner. This coupling gives rise to highly non-linear behavior, such as oscillations of the electrostatic potential. We derive analytical expressions for the critical surface charge density σc, after which adsorption takes place, and recover the well-known σc∼ns3/2 scaling regime, where ns is the salt concentration. In addition, the theory yields a new ns1 scaling regime if the surface is hard and a unified ns1 scaling regime if the surface also possesses some short-ranged attraction with the polyelectrolyte. Furthermore, we derive an analytical expression to describe the critical polyelectrolyte concentration φc to achieve complete charge reversal, which is found to scale as φc ∼ σ2/(f2c2), where c is related to the magnitude of short-ranged interactions and f is the average charge per monomer of the polyelectrolyte. It is observed that within our theory, complete charge reversal can only take place if the short-ranged interactions are sufficiently strong to completely compensate for the entropy loss of adsorption.

Fire alarm nano-coating with the controlled release of phosphorus-containing free radical for considerable flame retardant performance

The colloidal properties and surface charge characteristics of graphene oxide (GO) often lead to flocculation during the layer-by-layer (LBL) assembly. Innovatively, the charged flame retardant molecule, amino-tris(methylene phosphonic acid) (ATMP), is encapsulated within the inner cavity of halloysite nanotubes (HNTs). This integration exploits the unique structural features of HNT's inner cavity and outer wall. A composite nano-coating is constructed on the three-dimensional skeletal structure of melamine foam (MF) by assemblying GO with HNT-ATMP. This composite nano-coating exhibits both condensed-phase and gas-phase flame retardant functions. During the thermal decomposition process, phosphorus-containing radicals released from the HNTs' inner cavities enhance the flame retardancy. Moreover, the composite nano-coating demonstrates sensitive fire warning performance. A composite MF coated with 10 layers of this nano-coating emits a warning signal within 8 s fire exposure and maintains this signal without circuit failure. This study elucidates the mechanisms of flame retardancy and fire warning based on the thermal decomposition process and char layer analysis. By addressing the issue of GO flocculation during the assembly process, this research not only clarifies the underlying flame retardant and fire warning mechanisms of composite nano-coating but also proposes solutions for prolonging the duration of fire warning signals in advanced materials.

A holistic insight on stability and transport of hematite colloid: Role of various environmental factors

Hematite colloids (Hem) could carry pollutants into deep underground environments and its potential ecological risk needs to be evaluated. This study investigated the aggregation and transport behavior of Hem under different solution pH, electrolyte concentration and humic acid (HA) concentration. Rising the electrolyte concentration would shrink the double electric layer of Hem, weaken the electrostatic repulsion and promote the aggregation of Hem. The critical coagulation concentration (CCC) of Hem was higher at pH 5 (48.83 mM) than pH 10 (24.70 mM), implying that Hem were more stable under acidic conditions than under alkaline conditions. The addition of HA increased the negative charge of Hem and improved the electrostatic repulsion between colloid and sand surface, thus intensifying the stability and mobility of Hem. High HA concentration (≥ 0.5 mg/L) had little effect on the surface charge of Hem, indicating that electrostatic repulsion was not the dominant, however increasing HA significantly improve the stability and transport of Hem by stimulating the steric hindrance interaction. The effect of HA on the transport of Hem under acidic condition was significantly higher than that under alkaline condition because HA changed the surface charge of Hem from positive to negative under acidic condition, so that the electrostatic repulsion between the colloid and sand surface increased sharply and accompanied by a significant penetration. This study exhibited a holistic view on the aggregation and transport behavior of Hem in typical soil environment, and extended the understanding of co-transport potential mechanisms of colloids with contaminants and/or nutrients.

Natural mineral colloids facilitated transport of EE2 in saturated porous media: Effects of humic acid and conjugate form

Steroid estrogens have posed significant ecological risks to aquatic organisms due to their potent endocrine-disrupting effects. The role of natural mineral colloids in facilitating the transport of hydrophobic organic pollutants in the environment has been confirmed, but the control mechanisms of colloids on 17α-Ethinylestradiol (EE2) migration in the subsurface environment are often still not well understood. This study combined the batch sorption equilibrium experiments and dynamic transport simulations to reveal the interface interactions and co-transport characteristics between illite colloids and EE2 at both macroscopic and microscopic levels. The existing form changes of EE2 and the influence of coexisting humic acid (HA) during transport in porous media were also specifically investigated. The batch experiments demonstrated that the primary mechanisms governing EE2 sorption onto illite colloids involved surface sorption and hydrogen bonding. The coexistence of HA could load onto the surface of illite colloids, thereby enhancing the colloidal sorption capacity for EE2. Transport experiments demonstrated that the migratory ability of EE2 in silty clay was limited, but illite colloids could significantly promote its penetration, with the peak penetration content (Ct/C0) increasing from 0.64 to 0.77. In the absence of HA, EE2 primarily transported in a dissolved form, accounting for 62.86% of the total concentrations. When HA concentrations were increased to 10 mg/L and 20 mg/L, the proportion of colloidal conjugate EE2 in the effluents reached 52.13% and 54.49%, respectively. The enhanced transport of EE2 by HA was primarily attributed to the improved migration ability of illite colloids and the increased proportion of illite-EE2 conjugate, resulting in a maximum Ct/C0 value of 0.94. The validity of these results was further confirmed by employing calculations based on the Derjaguin–Landau–Verwey–Overbeek and Colloidal Filtration Theory. This study provides new insights of understanding the transport of EE2 in subsurface environment.

Discovery and application of food catalysts to promote the coupling of PQQ (quinone) with amines.

Biocatalysts (enzymes) play a crucial role in catalyzing specific reactions across various industries, often offering environmentally friendly and sustainable alternatives to chemical catalysts. However, their catalytic activities are susceptible to denaturation. In this study, we present the discovery of novel protein-based biocatalysts derived from processed foods, including skimmed milk, soy milk, cheese, and dried tofu. These food catalysts exhibit high availability, low cost, safety, and thermo-stability. Focusing on the physiologically intriguing coenzyme pyrroloquinoline quinone (PQQ), we observed that the reaction with glycine to form imidazolopyrroquinoline (IPQ) did not proceed efficiently when PQQ was present at very low concentrations. Surprisingly, in the presence of protein-based foods, this reaction was significantly accelerated. Notably, skimmed milk enhanced the PQQ detection limit (600 times lower) during high-performance liquid chromatography (HPLC) following IPQ derivatization. Milk appears to facilitate the reaction between PQQ and various amino acids, primary amines, and secondary amines. Further investigations revealed that food catalysis operates through a non-enzymatic mechanism. Additionally, nuclear magnetic resonance spectroscopy demonstrated that milk components interacted with amino substrates due to the ability of amines to react with quinones on colloidal surfaces. These practical food catalysts not only contribute to environmental safety but also hold significance across diverse scientific domains. Non-enzymatic protein catalysts find applications in biocatalysis, organic synthesis, food technology, analytical chemistry, and fundamental nutritional and evolutionary studies.

Adsorption and distribution of heavy metals in aquatic environments: The role of colloids and effects of environmental factors

The study investigated the distributions of heavy metals (Cd, Cr, Cu, Mn, and Pb) between dissolved fraction (<0.7 µm) and particles (>0.7 µm) during the adsorption process. The dissolved fraction was further separated into truly dissolved (<3 kDa) and colloidal (3 kDa-0.7 µm) fractions. Significant metal adsorption occurred on the colloids, resulting in their aggregation into particles, which in turn influenced the particle adsorption kinetics. Colloids could either accelerate or inhibit the transformation of metal ions into particulates, depending on their stability. Competitive metals for colloids (Pb and Cr) were more susceptible to the effects of colloids than other elements. DOM was the predominant environmental factor influencing colloid behavior. The XDLVO theory showed that DOM enhanced the negative charge of colloids and made the colloid surface more hydrophilic, inhibiting the aggregation of colloids. DOM resulted in substantial increases in the concentrations of colloidal Pb and Cr from 0.31 μg/L and 4.58 μg/L to 20.52 μg/L and 43.51 μg/L, respectively, whereas the increment for less competitive metals (Cd and Mn) was smaller. These findings suggest that the distribution of heavy metals is influenced not only by adsorption from particles and ions but also by the complex dynamics of colloids.

Optical and molecular insights into dissolved organic matter release in soils induced by downward migration of biochar colloids

The frequent wildfires and extensive biochar application accumulate biochar colloids in soils. The transport of biochar colloids may influence the release of soil dissolved organic matter (DOM) due to their high mobility and active surface, posing a detrimental impact on carbon cycle, pollutants behaviors, and water quality. Here, we examined the effect of pristine and aged biochar colloids on soil DOM release in three types of soils (black soil, fluvisol, and paddy soil) through adsorption and column experiments combined with fluorescence excitation/emission matrix spectroscopy (EEM) and fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Adsorption experiment showed that biochar exhibited little effect on soil DOM release, while transport experiment indicated that the downward movement of both pristine and aged biochar colloids significantly enhanced the release of soil DOM, especially black soil and fluvisol. EEM spectra indicated that a humic acid-like substance with large molecular weights was the primary DOM that enhanced release from black soil (10.9–12.0% enhancement) and fluvisol (6–8% enhancement) during biochar colloid transport. Condensed aromatic-like (22.8% and 19.4%) and tannin-like (18.4% and 18.9%) compounds are the primary molecules correlated to the enhanced release of humic acid-like substances. Although chemical aging resulted in a more negative surface of aged biochar colloids and slightly enhanced biochar colloid transport (up to 7.0%), it showed no distinct effect on the release of soil DOM. This study indicates that biochar colloids may cause an increase in DOM release when irrigation and rainfall occur, and more attention should be paid to the environmental impacts of biochar colloids from intensive biochar application and wildfires.Graphical

Enzyme-free and label-free detection of HER2 in human serum based on Ag+-released hybridization chain reaction signal amplification

The overexpression of human epidermal growth factor receptor 2 (HER2) has been linked to aggressive breast cancer and worse clinical outcomes. However, accurately measuring HER2 remains challenging, due to its low serum content. Herein, we developed a novel method for HER2 detection in serum by the combination of aptamer with C-Ag+-C structure, Ag+-released hybridization chain reaction (Ag+-HCR) and coprecipitation of Ag+ and gold nanoparticles (AuNPs) in the solution including Eosin Y (EY) and AgI colloids. Following the aptamer bound to HER2, signal amplification occurred through the release of numerous Ag+ by Ag+-HCR. This process subsequently induced AuNPs aggregation on the surface of AgI colloids, resulting in reduced fluorescence intensity of EY in the supernatant. The reduced value of EY fluorescence intensity in the supernatant was proportional to the level of HER2. Under optimized reaction conditions, a wide detection range was obtained between 0.09 and 9000 pg/mL with a limit of detection of 11.7 fg/mL in diluted human serum, and 96 serum samples in a 96-well plate could be measured simultaneously by a microtiter plate reader within 2 h. Moreover, the quantitative results of HER2 were consistent with those obtained using the enzyme-linked immunosorbent assay kit (r = 0.9995). Therefore, leveraging the delicate design of Ag+-HCR signal amplification, this enzyme-free, label-free, and effective method has demonstrated to be capable of detecting HER2 in serum due to its high sensitivity. Remarkably, this method may be extended to detect other cancer-related proteins and genes by replacing the corresponding target sequences.

Mechanical properties of polymer modified mortars using polymer latexes with varied glass transition temperature and surface charges

Mechanical properties of polymer modified mortar (PMM) were investigated using self-synthesized polymer latexes with varied glass transition temperature (Tg) and colloidal surface charges to build correlations between the mechanical properties of PMMs and the intrinsic properties of the polymers. Generally, compressive strength and elastic modulus of mortar are decreased, but ductility and toughness are enhanced by incorporation of the polymers. Impacts of the lower Tg polymers on the mechanical properties of PMMs are more pronounced. With increasing polymer content, flexural and tensile strength of mortar first increase and then decrease when using low Tg polymers that form continuous film during hardening of the mortars, while steadily decrease in the case of high Tg polymers that exist as individual particles in the hardened PMMs. For the high Tg polymer modified mortars, it is interestingly found that a subsequential heat treatment effectively promotes the film formation of the polymers in the hardened PMMs and thus greatly increases their flexural and tensile strength. This indicates that polymer film formation is essential to the enhancement of the PMMs, because the polymer films play a crack-bridging effect while the individual particles cannot do such job. The high Tg polymers lead to higher tensile strength of PMMs after heat treatment due to the higher inherent strength of the polymer film. Higher colloidal surface charge benefits the mechanical properties of the PMMs by (1) promoting a more homogenous polymer distribution in the hardened PMMs and/or (2) improving the bonding between the polymer phase and cement hydrates.

Phenylacetylene-Terminated Poly(Ethylene Glycol) as Ligands for Colloidal Noble Metal Nanoparticles: a New Tool for "Grafting to" Approach.

We report a new design of polymer phenylacetylene (PA) ligands and the ligand exchange methodology for colloidal noble metal nanoparticles (NPs). PA-terminated poly(ethylene glycol) (PEG) can bind to metal NPs through acetylide (M-C≡C-R) that affords a high grafting density. The ligand-metal interaction can be switched between σ bonding and extended π backbonding by changing grafting conditions. The σ bonding of PEG-PA with NPs is strong and it can compete with other capping ligands including thiols, while the π backbonding is much weaker. The σ bonding is also demonstrated to improve the catalytic performance of Pd for ethanol oxidation and prevent surface absorption of the reaction intermediates. Those unique binding characteristics will enrich the toolbox in the control of colloidal surface chemistry and their applications using polymer ligands.

Implanting Colloidal Nanoparticles into Single-Crystalline Zeolites for Catalytic Dehydration.

The encapsulation of functional colloidal nanoparticles (100 nm) into single-crystalline ZSM-5 zeolites, aiming to create uniform core-shell structures, is a highly sought-after yet formidable objective due to significant lattice mismatch and distinct crystallization properties. In this study, we demonstrate the fabrication of a core-shell structured single-crystal zeolite encompassing an Fe3O4 colloidal core via a novel confinement stepwise crystallization methodology. By engineering a confined nanocavity, anchoring nucleation sites, and executing stepwise crystallization, we have successfully encapsulated colloidal nanoparticles (CN) within single-crystal zeolites. These grafted sites, alongside the controlled crystallization process, compel the zeolite seed to nucleate and expand along the Fe3O4 colloidal nanoparticle surface, within a meticulously defined volume (1.5×107≤V≤1.3×108 nm3). Our strategy exhibits versatility and adaptability to an array of zeolites, including but not restricted to ZSM-5, NaA, ZSM-11, and TS-1 with polycrystalline zeolite shell. We highlight the uniformly structured magnetic-nucleus single-crystalline zeolite, which displays pronounced superparamagnetism (14 emu/g) and robust acidity (~0.83 mmol/g). This innovative material has been effectively utilized in a magnetically stabilized bed (MSB) reactor for the dehydration of ethanol, delivering an exceptional conversion rate (98 %), supreme ethylene selectivity (98 %), and superior catalytic endurance (in excess of 100 hours).

Implanting Colloidal Nanoparticles into Single‐Crystalline Zeolites for Catalytic Dehydration

AbstractThe encapsulation of functional colloidal nanoparticles (100 nm) into single‐crystalline ZSM‐5 zeolites, aiming to create uniform core–shell structures, is a highly sought‐after yet formidable objective due to significant lattice mismatch and distinct crystallization properties. In this study, we demonstrate the fabrication of a core–shell structured single‐crystal zeolite encompassing an Fe3O4 colloidal core via a novel confinement stepwise crystallization methodology. By engineering a confined nanocavity, anchoring nucleation sites, and executing stepwise crystallization, we have successfully encapsulated colloidal nanoparticles (CN) within single‐crystal zeolites. These grafted sites, alongside the controlled crystallization process, compel the zeolite seed to nucleate and expand along the Fe3O4 colloidal nanoparticle surface, within a meticulously defined volume (1.5×107≤V≤1.3×108 nm3). Our strategy exhibits versatility and adaptability to an array of zeolites, including but not restricted to ZSM‐5, NaA, ZSM‐11, and TS‐1 with polycrystalline zeolite shell. We highlight the uniformly structured magnetic‐nucleus single‐crystalline zeolite, which displays pronounced superparamagnetism (14 emu/g) and robust acidity (~0.83 mmol/g). This innovative material has been effectively utilized in a magnetically stabilized bed (MSB) reactor for the dehydration of ethanol, delivering an exceptional conversion rate (98 %), supreme ethylene selectivity (98 %), and superior catalytic endurance (in excess of 100 hours).

Effects of surfactants on the physical properties of silicate binders and the mechanical properties of silicate-bonded foundry sand cores

In the foundry industry, casting sand cores require high and low peak and residual strengths, respectively, to achieve comprehensive optimal mechanical performance. The peak and residual strengths of sand cores are positively related, highlighting the criticality of balancing them. Thus, an innovative approach comprising the incorporation of anionic surfactants into the silicate binder was introduced to balance both factors. Additionally, the investigation of the effects of the anionic surfactants on the physical properties of the silicate binder, including its colloidal stability, surface tension and adhesion, revealed that four different anionic surfactants reduced the surface tension and adhesion of the silicate binders and reduced the residual strength of the silicate-bonded sand cores. Among them, 0.10 wt% lauryl ether phosphate reduced the surface tension and adhesion of the adhesive by 49.64 and 112 mN/m, respectively, and reduced the residual strength of the sand core by 0.035 MPa. However, increasing the dosage did not further reduce the residual strength of the sand core, although it continued to reduce its peak strength. Therefore, during silicate binder modification with anionic surfactants, the dosage of the anionic surfactant must be kept at ≤0.10 wt%, as this dosage exerted the most comprehensive optimal modification effect, which was attributable to the adsorption of anionic polymers onto the surface of the silicate aggregates. This adsorption weakened the network structure of the silicate aggregates and imparted the sand cores with appropriate mechanical properties during casting.

Immunogenic and toxic effects of graphene oxide nanoparticles in mouse skeletal muscles and human red blood cells

To investigate immunogenic and toxic effects of graphene oxide (GO) nanoparticles in mouse skeletal muscles and in human blood in vitro. GO nanoparticles prepared using a probe sonicator were supended in deionized H2O or PBS, and particle size and surface charge of the nanoparticles were measured with dynamic light scattering (DLS). Different concentrations (0.5, 1.0 and 2.0 mg/mL) of GO suspension or PBS were injected at multiple sites in the gastrocnemius muscle (GN) of C57BL/6 mice, and inflammatory response and immune cell infiltrations were detected with HE and immunofluorescence staining. We also examined the effects of GO nanoparticles on human red blood cell (RBC) morphology, hemolysis and blood coagulation using scanning electron microscope (SEM), spectrophotometry, and thromboelastography (TEG). GO nanoparticles suspended in PBS exhibited better colloidal dispersity, stability and surface charge effects than those in deionized H2O. In mouse GNs, injection of GO suspensions dose- and time-dependently resulted in sustained muscular inflammation and myofiber degeneration at the injection sites, which lasted till 8 weeks after the injection; immunofluorescence staining revealed obvious infiltration of monocytes, macrophages, dendritic cells and CD4+ T cells around the injection sites in mouse GNs. In human RBCs, incubation with GO suspensions at 0.2, 2.0 and 20 mg/mL, but not at 0.002 or 0.02 mg/mL, caused significant alterations of cell morphology and hemolysis. TEG analysis showed significant abnormalities of blood coagulation parameters following treatment with high concentrations of GO. GO nanoparticles can induce sustained inflammatory and immunological responses in mouse GNs and cause RBC hemolysis and blood coagulation impairment, suggesting its muscular toxicity and hematotoxicity at high concentrations.