Size matters: Altering antigen specific immune tolerance by tuning size of particles.

Precisely co-delivering antigens and immunosuppressants via nano/microcarriers to antigen-presenting cells (APCs) to induce antigen-specific immune tolerance represents a highly promising strategy for treating or preventing autoimmune diseases. The physicochemical properties of nano/microcarriers play a pivotal role in regulating immune function, with particle size and surface charge emerging as crucial parameters. In particular, very few studies have investigated micron-scale carriers of antigens. Herein, various nanoparticles and microparticles (NPs/MPs) with diverse particle sizes (ranging from 200 nm to 5 µm) and surface charges were prepared. Antigen peptides (MOG35-55) and immunosuppressants were encapsulated in these particles to induce antigen-specific immune tolerance. Two emulsifiers, PVA and PEMA, were employed to confer different surface charges to the NPs/MPs. The in vitro and in vivo studies demonstrated that NP/MP-PEMA could induce immune tolerance earlier than NP/MP-PVA and that NP/MP-PVA could induce immune tolerance more slowly and sustainably, indicating that highly negatively charged particles can induce immune tolerance more rapidly. Among the different sizes and charged particles tested, 200-nm-NP-PVA and 3-µm-MP-PEMA induced the greatest immune tolerance. In addition, the combination of NPs with MPs can further improve the induction of immune tolerance. In particular, combining 200 nm-NP-PVA with 3 µm-MP-PEMA or combining 500 nm-NP-PEMA with 3 µm-MP-PVA had optimal therapeutic efficacy. This study offers a new perspective for treating diseases by combining NPs with MPs and applying different emulsifiers to prepare NPs and MPs.

Impact of surface charge density modulation on ion transport in heterogeneous nanochannels.

The PNP nanotransistor, consisting of emitter, base, and collector regions, exhibits distinct behavior based on surface charge densities and various electrolyte concentrations. In this study, we investigated the impact of surface charge density on ion transport behavior within PNP nanotransistors at different electrolyte concentrations and applied voltages. We employed a finite-element method to obtain steady-state solutions for the Poisson-Nernst-Planck and Navier-Stokes equations. The ions form a depletion region, influencing the ionic current, and we analyze the influence of surface charge density on the depth of this depletion region. Our findings demonstrate that an increase in surface charge density results in a deeper depletion zone, leading to a reduction in ionic current. However, at very low electrolyte concentrations, an optimal surface charge density causes the ion current to reach its lowest value, subsequently increasing with further increments in surface charge density. As such, at V app = + 1 V and C 0 = 1 mM , the ionic current increases by 25% when the surface charge density rises from 5 to 20  mC . m - 2 , whereas at C 0 = 10 mM , the ionic current decreases by 65% with the same increase in surface charge density. This study provides valuable insights into the behavior of PNP nanotransistors and their potential applications in nanoelectronic devices.

Monitoring changes in the zeta potential and the surface charge of human glioblastoma cells and phosphatidylcholine liposomes induced by curcumin as a function of pH.

Curcumin (CUR) has received worldwide attention for its beneficial effects on human health. Research report possible cytotoxic activity against various cancers, including glioblastoma. So far, little attention has been given to the binding properties of CUR to lipid membranes, which influences their electrical characteristics and can provide insight into their membrane-permeation abilities. Biophysical interactions between the polyphenol and in vitro models (liposomes and LN-18 human glioblastoma cells) were investigated by monitoring zeta potential and the membrane's surface charge as a function of pH. We focused on practical measurements and undertook a theoretical analysis of interactions in the natural cell membrane. We used the MTT assay to evaluate the viability of CUR-treated cells. Measurements performed using the Electrophoretic Light Scattering method demonstrated the dose-dependent effect of CUR on both membrane surface charge and zeta potential analyzed in vitro models. We determined theoretical parameters characterizing the cell membrane based on a quantitative description of the adsorption equilibria formed due to the binding of solution ions to the membrane of glioblastoma cells. The interaction of CUR with liposomes and human cancer cells is pH-dependent.

Influence of titanium surface roughness on a nanoscale on the zeta potential and platelet adhesion.

Thromboembolic complications still arise on blood contacting surfaces. Surface charge and topography influence the subsequent deposition of proteins and platelets, potentially leading to thrombi. Research showed a correlation of surface charge and nanoscale roughness, and a negative surface charge as well as a smooth surface finish are associated with lower thrombogenicity. The aim of this study was to compare the platelet adhesion on titanium with different nanoscale roughnesses and to examine if those roughness variations caused a change in surface charge. Titanium samples were polished and roughened to four different nanoscale roughness levels. Platelet adhesion (covered surface area (CSA), N = 8) was tested in flow chambers with human whole blood using fluorescence imaging. ζ-potential was measured over a broad range of pH-values and interpolated to obtain the ζ-potential for pHBlood (7.4). Platelet adhesion tests were evaluated in terms of p-values and the Wilcoxon test effect size and the trend of the ζ-potential at pHBlood and the CSA was compared. Ra-values ranged between 35 (polished) and 156 nm. Regarding platelet adhesion, the polished sample showed the lowest mean CSA with a medium or strong effect size compared to the roughened samples. The interpolated ζ-potentials for pHBlood follow a similar trend as the CSA, with the lowest ζ-potential measured for the polished surface. These findings suggest that the decreasing ζ-potential due to lower nanoscale roughness might be an additional explanation for the improved hemocompatibility besides the smoother topography.

Impact of nanosilver surface electronic distributions on serum protein interactions and hemocompatibility.

The translation of silver-based nanotechnology 'from bench to bedside' requires a deep understanding of the molecular aspects of its biological action, which remains controversial at low concentrations and non-spherical morphologies. Here, we present a hemocompatibility approach based on the effect of the distinctive electronic charge distribution in silver nanoparticles (nanosilver) on blood components. According to spectroscopic, volumetric, microscopic, dynamic light scattering measurements, pro-coagulant activity tests, and cellular inspection, we determine that at extremely low nanosilver concentrations (0.125-2.5µg ml-1), there is a relevant interaction effect on the serum albumin and red blood cells (RBCs). This explanation has its origin in the surface charge distribution of nanosilver particles and their electron-mediated energy transfer mechanism. Prism-shaped nanoparticles, with anisotropic charge distributions, act at the surface level, generating a compaction of the native protein molecule. In contrast, the spherical nanosilver particle, by exhibiting isotropic surface charge, generates a polar environment comparable to the solvent. Both morphologies induce aggregation at NPs/bovine serum albumin ≈ 0.044 molar ratio values without altering the coagulation cascade tests; however, the spherical-shaped nanosilver exerts a negative impact on RBCs. Overall, our results suggest that the electron distributions of nanosilver particles, even at extremely low concentrations, are a critical factor influencing the molecular structure of blood proteins' and RBCs' membranes. Isotropic forms of nanosilver should be considered with caution, as they are not always the least harmful.

Counterion Distribution in the Stern Layer on Charged Surfaces.

Counterion adsorption at the solid-liquid interface affects numerous applications. However, the counterion adsorption density in the Stern layer has remained poorly evaluated. Here we report the direct determination of surface charge density at the shear plane between the Stern layer and the diffuse layer. By the Grahame equation extension and streaming current measurements for different solid surfaces in different aqueous electrolytes, we are able to obtain the counterion adsorption density in the Stern layer, which is mainly related to the surface charge density but is less affected by the bulk ion concentration. The charge inversion concentration is further found to be sensitive to the ion type and ion valence rather than to the charged surface, which is attributed to the ionic competitive adsorption and ion-ion correlations. Our findings offer a framework for understanding ion distribution in many physical and chemical processes where the Stern layer is ubiquitous.

Surface Charge-Modulated Toxicity of Cysteine-Stabilized Silver Nanoparticles.

The toxicity of silver nanoparticles (AgNPs) depends on their physicochemical properties. The ongoing research aims to develop effective methods for modifying AgNPs using molecules that enable control over the processes induced by nanoparticles in both normal and cancerous cells. Application of amino acid-stabilized nanoparticles appears promising, exhibiting tunable electrokinetic properties. Therefore, this study focused on determining the influence of the surface charge of cysteine (CYS)-stabilized AgNPs on their toxicity towards human normal B (COLO-720L) and T (HUT-78) lymphocyte cell lines. CYS-AgNPs were synthesized via the chemical reduction. Transmission electron microcopy (TEM) imaging revealed that they exhibited a quasi-spherical shape with an average size of 18 ± 3 nm. CYS-AgNPs remained stable under mild acidic (pH 4.0) and alkaline (7.4 and 9.0) conditions, with an isoelectric point observed at pH 5.1. Following a 24 h treatment of lymphocytes with CYS-AgNPs, concentration-dependent alterations in cell morphology were observed. Positively charged CYS-AgNPs notably decreased lymphocyte viability. Furthermore, they exhibited grater genotoxicity and more pronounced disruption of biological membranes compared to negatively charged CYZ-AgNPs. Despite both types of AgNPs interacting similarly with fetal bovine serum (FBS) and showing comparable profiles of silver ion release, the biological assays consistently revealed that the positively charged CYS-AgNPs exerted stronger effects at all investigated cellular levels. Although both types of CYS-AgNPs have the same chemical structure in their stabilizing layers, the pH-induced alterations in their surface charge significantly affect their biological activity.

Regulating band structure, charge transfer and separation, oxygen adsorption and activation by surface ion modification.

As a most promising environmental technology, the substantial enhancement of photocatalytic efficiency is still a big challenge for practical applications. In this work, the surface of Bi2O2CO3 (BOC) nanotubes are modified by Cl and I. The as-obtained samples at different hydrothermal temperatures (T) are designated as T-X-BOC (X = Cl, I). X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) prove that Cl and I merely chemically adsorb on the BOC surface, rather than dope into the crystal lattice. The surface modification of Cl and I slightly increases light absorption range, while significantly promotes the photoelectron migration from bulk to the surface that greatly enhances the carrier separation efficiency. Density functional theory (DFT) calculations further prove that surface Cl and I have adjusted band structure and surface charge distribution. Besides, the surface Cl and I favor the O2 adsorption and trap the surface photoelectrons, thus promoting the formation of •O2-; while the surface Cl and I impede the surface adsorption of H2O, thus refraining the generation of •OH. In the degradation of rhodamine B (RhB), holes and •O2- radicals play the crucial role. Under ultraviolet light irradiation (λ < 420 nm) for 45 min, the RhB degradation ratios over 150-Cl-BOC (94%) and 150-I-BOC (85%) are 4.2 and 3.7 times higher than that of original BOC (18%), respectively. This work demonstrates that the simple surface halogenation modification greatly improves the photocatalytic activity.

Conditional Cell-Penetrating Peptide Exposure as Selective Nanoparticle Uptake Signal.

A major bottleneck diminishing the therapeutic efficacy of various drugs is that only small proportions of the administered dose reach the site of action. One promising approach to increase the drug amount in the target tissue is the delivery via nanoparticles (NPs) modified with ligands of cell surface receptors for the selective identification of target cells. However, since receptor binding can unintentionally trigger intracellular signaling cascades, our objective was to develop a receptor-independent way of NP uptake. Cell-penetrating peptides (CPPs) are an attractive tool since they allow efficient cell membrane crossing. So far, their applicability is severely limited as their uptake-promoting ability is nonspecific. Therefore, we aimed to achieve a conditional CPP-mediated NP internalization exclusively into target cells. We synthesized different CPP candidates and investigated their influence on nanoparticle stability, ζ-potential, and uptake characteristics in a core-shell nanoparticle system consisting of poly(lactid-co-glycolid) (PLGA) and poly(lactic acid)-poly(ethylene glycol) (PLA10kPEG2k) block copolymers with CPPs attached to the PEG part. We identified TAT47-57 (TAT) as the most promising candidate and subsequently combined the TAT-modified PLA10kPEG2k polymer with longer PLA10kPEG5k polymer chains, modified with the potent angiotensin-converting enzyme 2 (ACE2) inhibitor MLN-4760. While MLN-4760 enables selective target cell identification, the additional PEG length hides the CPP during a first unspecific cell contact. Only after the previous selective binding of MLN-4760 to ACE2, the established spatial proximity exposes the CPP, triggering cell uptake. We found an 18-fold uptake improvement in ACE2-positive cells compared to unmodified particles. In summary, our work paves the way for a conditional and thus highly selective receptor-independent nanoparticle uptake, which is beneficial in terms of avoiding side effects.

The surface charge of electroactive materials governs cell behaviour through its effect on protein deposition.

The precise mechanisms underlying the cellular response to static electric cues remain unclear, limiting the design and development of biomaterials that utilize this parameter to enhance specific biological behaviours. To gather information on this matter we have explored the interaction of collagen type-I, the most abundant mammalian extracellular protein, with poly(vinylidene fluoride) (PVDF), an electroactive polymer with great potential for tissue engineering applications. Our results reveal significant differences in collagen affinity, conformation, and interaction strength depending on the electric charge of the PVDF surface, which subsequently affects the behaviour of mesenchymal stem cells seeded on them. These findings highlight the importance of surface charge in the establishment of the material-protein interface and ultimately in the biological response to the material. STATEMENT OF SIGNIFICANCE: The development of new tissue engineering strategies relies heavily on the understanding of how biomaterials interact with biological tissues. Although several factors drive this process and their driving principles have been identified, the relevance and mechanism by which the surface potential influences cell behaviour is still unknown. In our study, we investigate the interaction between collagen, the most abundant component of the extracellular matrix, and poly(vinylidene fluoride) with varying surface charges. Our findings reveal substantial variations in the binding forces, structure and adhesion of collagen on the different surfaces, which collectively explain the differential cellular responses. By exposing these differences, our research fills a critical knowledge gap and paves the way for innovations in material design for advanced tissue regeneration strategies.

Chitosan Coating as a Strategy to Increase Postemergent Herbicidal Efficiency and Alter the Interaction of Nanoatrazine with Bidens pilosa Plants.

The atrazine nanodelivery system, composed of poly(ε-caprolactone) (PCL+ATZ) nanocapsules (NCs), has demonstrated efficient delivery of the active ingredient to target plants in previous studies, leading to greater herbicide effectiveness than conventional formulations. Established nanosystems can be enhanced or modified to generate new biological activity patterns. Therefore, this study aimed to evaluate the effect of chitosan coating of PCL+ATZ NCs on herbicidal activity and interaction mechanisms with Bidens pilosa plants. Chitosan-coated NCs (PCL/CS+ATZ) were synthesized and characterized for size, zeta potential, polydispersity, and encapsulation efficiency. Herbicidal efficiency was assessed in postemergence greenhouse trials, comparing the effects of PCL/CS+ATZ NCs (coated), PCL+ATZ NCs (uncoated), and conventional atrazine (ATZ) on photosystem II (PSII) activity and weed control. Using a hydroponic system, we evaluated the root absorption and shoot translocation of fluorescently labeled NCs. PCL/CS+ATZ presented a positive zeta potential (25 mV), a size of 200 nm, and an efficiency of atrazine encapsulation higher than 90%. The postemergent herbicidal activity assay showed an efficiency gain of PSII activity inhibition of up to 58% compared to ATZ and PCL+ATZ at 96 h postapplication. The evaluation of weed control 14 days after application ratified the positive effect of chitosan coating on herbicidal activity, as the application of PCL/CS+ATZ at 1000 g of a.i. ha-1 resulted in better control than ATZ at 2000 g of a.i. ha-1 and PCL+ATZ at 1000 g of a.i. ha-1. In the hydroponic experiment, chitosan-coated NCs labeled with a fluorescent probe accumulated in the root cortex, with a small quantity reaching the vascular cylinder and leaves up to 72 h after exposure. This behavior resulted in lower leaf atrazine levels and PSII inhibition than ATZ. In summary, chitosan coating of nanoatrazine improved the herbicidal activity against B. pilosa plants when applied to the leaves but negatively affected the root-to-shoot translocation of the herbicide. This study opens avenues for further investigations to improve and modify established nanosystems, paving the way for developing novel biological activity patterns.

Positively Charged Hollow Co Nanoshells by Kirkendall Effect Stabilized by Electron Sink for Alkaline Water Dissociation.

While cobalt (Co) exhibits a comparable energy barrier for H* adsorption/desorption to platinum in theory, it is generally not suitable for alkaline hydrogen evolution reaction (HER) because of unfavorable water dissociation. Here, the Kirkendall effect is adopted to fabricate positive-charged hollow metal Co (PHCo) nanoshells that are stabilized by MoO2 and chainmail carbon as the electron sink. Compared to the zero-valent Co, the PHCo accelerates the water dissociation and changes the rate-determining step from Volmer to Heyrovsky process. Alkaline HER occurs with a low overpotential of 59.0 mV at 10 mA cm-2. Operando Raman and first principles calculations reveal that the interfacial water to the PHCo sites and the accelerated proton transfer are conducive to the adsorption and dissociation of H2O molecules. Meanwhile, the upshifted d-band center of PHCo optimizes the adsorption/desorption of H*. This work provides a unique synthesis of hollow Co nanoshells via the Kirkendall effect and insights to water dissociation on catalyst surfaces with tailored charge states.

Relationships of the Surface Charge of Low-Density Lipoprotein (LDL) with the Serum LDL-Cholesterol and Atherosclerosis Levels in a Japanese Population: The DOSANCO Health Study.

AIM: This study investigated the associations of the surface charge of low-density lipoprotein (LDL) with the serum LDL-cholesterol and atherosclerosis levels in a community-based Japanese population. METHODS: The study had a cross-sectional design and included 409 community residents aged 35-79 years who did not take medications for dyslipidemia. The potential electric charge of LDL and the zeta potential, which indicate the surface charge of LDL, were measured by laser Doppler microelectrophoresis. The correlations of the zeta potential of LDL (-mV) with the serum LDL-cholesterol levels (mg/dL), cardio-ankle vascular index (CAVI), and serum high-sensitivity C-reactive protein (hsCRP) levels (log-transformed values, mg/L) were examined using Pearson's correlation coefficient (r). Linear regression models were constructed to examine these associations after adjusting for potential confounding factors. RESULTS: A total of 201 subjects with correctly stored samples were included in the primary analysis for zeta potential measurement. An inverse correlation was observed between the LDL zeta potential and the serum LDL-cholesterol levels (r=-0.20; p=0.004). This inverse association was observed after adjusting for sex, age, dietary cholesterol intake, smoking status, alcohol intake, body mass index, and the serum levels of the major classes of free fatty acids (standardized ß=-6.94; p=0.005). However, the zeta potential of LDL showed almost no association with CAVI or the serum hsCRP levels. Similar patterns were observed in the 208 subjects with compromised samples as well as all the original 409 subjects. CONCLUSION: A higher electronegative surface charge of LDL was associated with lower serum LDL-cholesterol levels in the general Japanese population.

Multicomponent and Surface Charge Effects on PFOS Sorption and Transport in Goethite-Coated Porous Media under Variable Hydrochemical Conditions.

Perfluorooctanesulfonate (PFOS), a toxic anionic perfluorinated surfactant, exhibits variable electrostatic adsorption mechanisms on charge-regulated minerals depending on solution hydrochemistry. This work explores the interplay of multicomponent interactions and surface charge effects on PFOS adsorption to goethite surfaces under flow-through conditions. We conducted a series of column experiments in saturated goethite-coated porous media subjected to dynamic hydrochemical conditions triggered by step changes in the electrolyte concentration of the injected solutions. Measurements of pH and PFOS breakthrough curves at the outlet allowed tracking the propagation of multicomponent reactive fronts. We performed process-based reactive transport simulations incorporating a mechanistic network of surface complexation reactions to quantitatively interpret the geochemical processes. The experimental and modeling outcomes reveal that the coupled spatio-temporal evolution of pH and electrolyte fronts, driven by the electrostatic properties of the mineral, exerts a key control on PFOS mobility by determining its adsorption and speciation reactions on goethite surfaces. These results illuminate the important influence of multicomponent transport processes and surface charge effects on PFOS mobility, emphasizing the need for mechanistic adsorption models in reactive transport simulations of ionizable PFAS compounds to determine their environmental fate and to perform accurate risk assessment.

Transgenerational reproductive toxicity induced by carboxyl and amino charged microplastics at environmental concentrations in Caenorhabditis elegans: Involvement of histone methylation.

Microplastics, recognized as emerging contaminants, are commonly observed to be charged in the environment, potentially exerting toxic effects on various organisms. However, the transgenerational reproductive toxicity and underlying mechanisms of polystyrene (PS), particularly carboxyl-modified PS (PS-COOH) and amino-modified PS (PS-NH2), remain largely unexplored. In this study, the parental generation (P0) of Caenorhabditis elegans was subjected to environmental concentrations (0.1-100 µg/L) of PS, PS-COOH, and PS-NH2, with subsequent generations (F1-F4) cultured under normal conditions. Exposure to PS-NH2 at concentrations of 10-100 µg/L exhibited more pronounced reproductive toxicity compared to PS or PS-COOH, resulting in decreased brood size, egg ejection rate, number of fertilized eggs, and cell corpses per gonad. Similarly, maternal exposure to 100 µg/L of PS-NH2 induced more severe transgenerational reproductive effects in C. elegans. Significant increases in H3 on lysine 4 dimethylation (H3K4me2) and H3 on lysine 9 trimethylation (H3K9me3) levels were observed in the subsequent generation, concurrent with the transgenerational upregulation of set-30 and met-2 following parental exposure to PS, PS-COOH, and PS-NH2. Correlation analyses revealed significant associations between the expression of these genes with the reproductive ability. Molecular docking studies suggested that PS-NH2 exhibited higher affinity for SET-30 and MET-2. Further analysis demonstrated that transgenerational effects on reproduction were absent in set-30(gk315) and met-2(n4256) mutants, highlighting the pivotal role of set-30 and met-2 in mediating the transgenerational effect. This study provides novel insights into the environmental risks associated with negatively and positively charged microplastics.

Investigation of the impact of planar microelectrodes on macrophage-mediated mesenchymal stem cell osteogenesis.

Osseointegration commences with foreign body inflammation upon implant placement, where macrophages play a crucial role in the immune response. Subsequently, during the intermediate and late stages of osseointegration, mesenchymal stem cells (MSCs) migrate and initiate their osteogenic functions, while macrophages support MSCs in osteogenesis. The utilization of ferroelectric P(VDF-TrFE) covered ITO planar microelectrodes facilitated the simulation of various surface charge to investigate their effects on MSCs' osteogenic differentiation and macrophage polarization and the results indicated a parabolic increase in the promotional effect of both with the rise in piezoelectric coefficient. Furthermore, the surface charge with a piezoelectric coefficient of -18 exhibited the strongest influence on the promotion of M1 polarization of macrophages and the promotion of MSCs' osteogenic differentiation. The impact of macrophage polarization and MSC osteogenesis following the interaction of macrophages affected by surface charge and MSC was ultimately investigated. It was observed that macrophages affected by the surface charge of -18 piezoelectric coefficient still exerted the most profound induced osteogenic effect, validating the essential role of M1-type macrophages in the osteogenic differentiation of MSCs.

Platinum-Iridium Alloy Nanoparticle Coatings Produced by Electrophoretic Deposition Reduce Impedance in 3D Neural Electrodes.

Platinum-based neural electrodes, frequently alloyed with Ir or W, are routinely used to treat neurological disorders. However, their performance is impaired by an increase in impedance that compromises long-term implant functionality. Though there are multiple coating techniques available to address this issue, electrode, and base material often exhibit a compositional mismatch, which impairs mechanical stability and may lead to toxicological side effects. In this work, we coated Pt wire electrodes with ligand-free electrostatically stabilized colloidal Pt90Ir10, Pt90W10, and Pt50W50 alloy nanoparticles (NPs) matching electrode compositions using electrophoretic deposition (EPD) with direct-current (DC) and pulsed-DC fields in aqueous medium. The generated alloy NPs exhibit a solid solution structure as evidenced by HR-TEM-EDX and XRD, though additional WOx phases were identified in the Pt50W50 samples. Consequently, coating efficiency was also impaired in the presence of high W mass fractions in the alloy NPs. Characterization of the NP coatings by cyclic voltammetry and impedance spectroscopy yielded a significant reduction of the impedance in the Pt90Ir10 sample in comparison to the control coated with Pt NPs. The electrochemical surface area (ECSA) of the PtW alloy coatings, on the other hand, was significantly reduced.

Assessing Activation Quality through Evaporative Drying Patterns of Zr-MOF (UiO-66) Colloidal Droplets.

We demonstrate a simple droplet diagnostic approach to monitor the UiO-66 MOF (metal-organic framework) synthesis and its quality using the sessile droplet drying phenomenon. Drying a sessile droplet involves evaporation-driven hydrodynamic flow and particle-nature-dependent self-assembled deposition. In general, the MOF synthesis process involves different sizes and physicochemical nature of particles in every synthesis stage. Equivalent quantities of each of purified pore-activated UiO-66 MOF, yet-to-be-purified pore-inactivated UiO-66 MOF, and reaction precursors of UiO-66 MOF give different deposition patterns when a well-dispersed aqueous droplet of these materials undergoes drying over substrates of varying stiffness and wettability. Yet-to-be-purified, pore-inactivated UiO-66 MOF nanoparticles undergo transport toward the droplet periphery, leading to a thick ring-like deposition at the dried droplet edge. Under appropriate drying conditions, such a deposit leads to desiccation-type mud-like reticular cracking. We study the origin of such ring-like deposits and cracks to understand how the surface charge density of UiO-66 particles controls their stability. We demonstrate that ZrOCl2 salt trapped in a nonpurified pore-inactivated UiO-66 MOF moiety is the principal reason for ring-like deposit formation and subsequent cracking in its dried aqueous droplet edge. Qualitatively, we identified Lewis acid salts that are capable of acting as BroÌ·nsted acid upon hydrolysis (like FeCl3, SnCl2, and ZrOCl2), influence surface charge density and colloidal stability of dispersed UiO-66 MOF particles. As a result, immediate particle coagulation is avoided, so those travel to the droplet edge, forming ring-like deposition and subsequent cracking upon drying. Further, we show that crack patterns on such deposits are highly dependent on the stiffness and temperature of depositing substrates via a competition between axial and lateral strains at the deposit-substrate interface.

Enhanced Photocatalytic Removal of U(VI) from Real Radioactive Wastewater by Modulating the Surface Charge Microenvironment in Porphyrin-Based Hydrogen-Bonded Organic Framework.

Reduction of soluble U(VI) to insoluble U(IV) based on photocatalysts is a simple, environmentally friendly, and efficient method for treating radioactive wastewater. The present study involved the systematic comparison of the photoelectric properties of three metalloporphyrins with different metal centers and the synthesis of a novel porphyrin-based hydrogen-bonded organic framework (Ni-pHOF) photocatalyst by modulating the surface charge microenvironment in porphyrin for enhanced photocatalytic removal of U(VI) from wastewater. Compared to the metal-free HOF, the surface charge microenvironment around the Ni atom in Ni-pHOF accelerated the reduction kinetics of U(VI) under visible light illumination at the initial moment, showing a high removal rate, even in air. The removal rate of U(VI) from aqueous solution by Ni-pHOF can achieve over 98% in the presence of coexisting nonoxidizing cations and only decreased by less than 8% after five cycles, exhibiting high selectivity and good reusability. Furthermore, Ni-pHOF can remove 86.74% of U(VI) from real low-level radioactive wastewater after 120 min of illumination, showcasing practical application potential. Density functional theory (DFT) calculations and electron paramagnetic resonance (EPR) spectra indicated that modulating the surface charge microenvironment in Ni-pHOF through porphyrin metallization is conducive to improving the charge separation efficiency, prompting more e- and •O2- to participate in the reduction reaction of U(VI). This work provides new insights into the metallization of porphyrin-based HOFs and paves a new way for the tailoring of porphyrin-based HOFs/COFs by modulating the surface charge microenvironment to achieve efficient recovery of U(VI) from real radioactive wastewater.

Understanding the relationship between pore size, surface charge density, and Cu2+ adsorption in mesoporous silica.

This research delved into the influence of mesoporous silica's surface charge density on the adsorption of Cu2+. The synthesis of mesoporous silica employed the hydrothermal method, with pore size controlled by varying the length of trimethylammonium bromide (CnTAB, n = 12, 14, 16) chains. Gas adsorption techniques and transmission electron microscopy characterized the mesoporous silica structure. Surface charge densities of the mesoporous silica were determined through potentiometric titration, while surface hydroxyl densities were assessed using the thermogravimetric method. Subsequently, batch adsorption experiments were conducted to study the adsorption of Cu2+ in mesoporous silica, and the process was comprehensively analyzed using Atomic absorption spectrometry (AAS), Fourier transform infrared (FTIR), and L3 edge X-ray absorption near edge structure (XANES). The research findings suggest a positive correlation between the pore size of mesoporous silica, its surface charge density, and the adsorption capacity for Cu2+. More specifically, as the pore size increases within the 3-4.1 nm range, the surface charge density and the adsorption capacity for Cu2+ also increase. Our findings provide valuable insights into the relationship between the physicochemical properties of mesoporous silica and the adsorption behavior of Cu2+, offering potential applications in areas such as environmental remediation and catalysis.