Negatively Charged Research Articles

Unravelling heterogenous adsorption performance of hydrochar particle and key properties in heavy metal immobilization relative to corresponding residual bulk hydrochar

Immobilization performance of released hydrochar particle (HP) to metal is largely unknown and hinder accurate estimation to immobilization effect in hydrochar application. Herein, HPs derived from typical biomass, food waste (FW), and blue algae (BA), were collected to investigate their adsorption abilities, mechanisms towards typical Cd(II) relative to residual bulk hydrochar (BH) and unravel corresponding properties of this heterogeneity. The results were: 1) the micro-sized HP with poor porous structure, less O-containing functional groups (OFGs) and negative surface charge induced inferior adsorption capacities (0.65-0.81 times) but quicker adsorption rate (3.09-10.08 times) towards Cd(II) compared with BH, 2) cation bridge interaction in coagulation and settling processes unexpectedly facilitated adsorption performance of micro-sized and negative charged FWHPs added with counterions, 3) HP facilitated its electrostatic attraction with Cd(II) rather than common pore filling and surface complexation, especially bare aromatic structure in HP formed another cation-π interaction with Cd(II) highlighted by density functional theory (DFT) method. The special coagulation process and cation-π interaction of HP will facilitate its vertical co-migration ability but weaken immobilization stability towards metals. The distinct heterogeneities of adsorption ability of HP and BH and underlying key properties provide an in-depth understanding of hydrochar application for remediation of metal contaminants in soil/water environment.

The effect of extremolytes ectoine and hydroxyectoine on the heat-induced protein aggregation: The case of growth hormone

The extremolytes ectoine and hydroxyectoine are osmolytes found in extremophilic microorganisms. They are stabilisers of proteins and other macromolecules, including DNA and lipids. The aim of the study was to investigate the effect of the additives on the heat-induced aggregation of mink growth hormone as a model protein. The first-order rate constants of protein aggregation were determined at 60 °C depending on the additive concentration and pH of the solution. The onset temperature of aggregation was also recorded using a circular dichroism spectropolarimeter. The study showed that the effect of the additives depended on the pH of the solution. The first-order rate constants of aggregation were lower when the protein molecule had a negative charge. The effect also depended on the structure of the extremolyte itself. When the protein molecule was positively charged, hydroxyectoine destabilised the mink growth hormone molecule and promoted the aggregation. The different effects of the additives were determined by the different interactions with the protein molecules, as shown by circular dichroism measurements and previously by fluorescence spectroscopy. Therefore, when using ectoine or hydroxyectoine for protein formulation, the effect of the additive should be carefully analysed for each protein individually.

Fabrication of PVC-based electromagnetic interference shielding composite film by positively charged SMA enhancing the dispersibility of carbon nanomaterial

To address the weak binding force and poor dispersion stability of carbon (C) nanoparticles in current non-covalent modification methods, we employed organic amine-grafted styrene maleic anhydride copolymers (SMA-N) to modify C nanoparticles (C@SMA-N) through π–π conjugation and positive charge interactions. The obtained C@SMA-N has excellent dispersion in N, N-dimethylacetamide (DMAc), which is attributed to the enhanced steric hindrance and electrostatic repulsion from the grafted organic amine chains. To study the impact of surface modification on the electromagnetic interference shielding effectiveness (EMI SE), C@SMA-N was used as a conductive filler in polyvinyl chloride (PVC) composite films, which exhibits a higher EMI SE performance than pristine C nanoparticles. Particularly, the obtained C@SMA-N using polyether amine (PEA) (C@SMA-PEA) exhibits a better EMI SE performance. By optimizing the SMA-PEA grafting parameters, the PVC/C@SMA-PEA composite films transition from insulators to conductors at a C@SMA-PEA content of 0.3 wt%. To achieve a higher EMI SE performance, the filler content, mixed filler composition, and film thickness were optimized. The results indicate that with a total filler content of 20 wt% and a mixed filler comprising fibrous form carbon nanotubes (CNT) and particles form carbon black (CB) in a 10:1 mass ratio (CB@SMA-PEA to CNT@SMA-PEA), the composite film has a thickness of 0.08 mm and an EMI SE value of 20.2 dB. Increasing the thickness to 0.2 mm enhances the EMI SE value to 31.5 dB. These findings indicate that thinner films have a higher EMI SE performance and promising application prospects in the field of electromagnetic shielding.

A biodegradable lipid nanoparticle delivers a Cas9 ribonucleoprotein for efficient and safe in situ genome editing in melanoma

The development of melanoma is closely related to Braf gene, which is a suitable target for CRISPR/Cas9 based gene therapy. CRISPR/Cas9-sgRNA ribonucleoprotein complexes (RNPs) stand out as the safest format compared to plasmid and mRNA delivery. Similarly, lipid nanoparticles (LNPs) emerge as a safer alternative to viral vectors for delivering the CRISPR/Cas9-sgRNA gene editing system. Herein, we have designed multifunctional cationic LNPs specifically tailored for the efficient delivery of Cas9 RNPs targeting the mouse Braf gene through transdermal delivery, aiming to treat mouse melanoma. LNPs are given a positive charge by the addition of a newly synthesized polymer, deoxycholic acid modified polyethyleneimine (PEI-DOCA). Positive charge enables LNPs to be delivered in vivo by binding to negatively charged cell membranes and proteins, thereby facilitating efficient skin penetration and enhancing the delivery of RNPs into melanoma cells for gene editing purposes. Our research demonstrates that these LNPs enhance drug penetration through the skin, successfully delivering the Cas9 RNPs system and specifically targeting the Braf gene. Cas9 RNPs loaded LNPs exert a notable impact on gene editing in melanoma cells, significantly suppressing their proliferation. Furthermore, in mice experiments, the LNPs exhibited skin penetration and tumor targeting capabilities. This innovative LNPs delivery system offers a promising gene therapy approach for melanoma treatment and provides fresh insights into the development of safe and effective delivery systems for Cas9 RNPs in vivo. Statement of significanceCRISPR/Cas9 technology brings new hope for cancer treatment. Cas9 ribonucleoprotein offers direct genome editing, yet delivery challenges persist. For melanoma, transdermal delivery minimizes toxicity but faces skin barrier issues. We designed multifunctional lipid nanoparticles (LNPs) for Cas9 RNP delivery targeting the Braf gene. With metal microneedle pretreatment, our LNPs effectively edited melanoma cells, reducing Braf expression and inhibiting tumor growth. Our study demonstrates LNPs' potential for melanoma therapy and paves the way for efficient in vivo Cas9 RNP delivery systems in cancer therapy.

Highly Anion-Conductive Viologen-Based Two-Dimensional Polymer Membranes as Nanopower Generators.

Two-dimensional polymers (2DPs) and their layer-stacked 2D covalent organic frameworks (2D COFs) membranes hold great potential for harvesting sustainable osmotic energy. The nascent research has yet to simultaneously achieve high ionic flux and selectivity, primarily due to inefficient ion transport dynamics. This is directly related to ultrasmall pore size (<3 nm), much smaller than the duple Debye length in the diluted electrolyte (6-20 nm), as well as low charge density (<4.5 mC m-2). Here, we introduce a π-conjugated viologen-based 2DP (V2DP) membrane possessing a large pore size of 4.5 nm, strategically enhancing the overlapping of the electric double layer, coupled with an exceptional positive surface charge density (~6 mC m-2). These characteristics enable the membrane to facilitate high anion flux while maintaining ideal selectivity. Notably, V2DP membranes realize an impressive current density of 5.5×103 A m-2, surpassing benchmarks set by previously reported nanofluidic membranes. In the practical application scenario involving the mixing of artificial seawater and river water, the V2DP membranes exhibit a considerable ion transference number of 0.70 towards Cl-, contributing to an outstanding power density of ~55 W m-2. Theoretical calculations reveal the important role of the large quantity of anion transport sites, which act as binding sites evenly located in the positively charged N-containing pyridine rings. These binding sites enable kinematic coupling and decoupling between anions and the V2DP skeleton, establishing a continuous Cl- ion transport pathway. This work demonstrates the great promise of large-area ultrathin 2DP membranes featuring highly organized charged ion transport networks when applied for osmotic energy conversion.

Identification of the N-terminal residues responsible for the differential microdomain localization of CYP1A1 and CYP1A2

The endoplasmic reticulum (ER) is organized into ordered regions enriched in cholesterol and sphingomyelin, and disordered microdomains characterized by more fluidity. Rabbit CYP1A1 and CYP1A2 localize into disordered and ordered microdomains, respectively. Previously, a CYP1A2 chimera containing the first 109 amino acids of CYP1A1 showed altered microdomain localization. The goal of this study was to identify specific residues responsible for CYP1A microdomain localization. Thus, CYP1A2 chimeras containing substitutions from homologous regions of CYP1A1 were expressed in HEK 293T/17 cells, and the localization was examined after solubilization with Brij 98. A CYP1A2 mutant with the three amino acids from CYP1A1 (VAG) at positions 27-29 of CYP1A2 was generated that showed a distribution pattern similar to those of CYP1A1/1A2 chimeras containing both the first 109 amino acids and the first 31 amino acids of CYP1A1 followed by remaining amino acids of CYP1A2. Similarly, the reciprocal substitution of three amino acids from CYP1A2 (AVR) into CYP1A1 resulted in a partial redistribution of the chimera into ordered microdomains. Molecular dynamic simulations indicate that the positive charges of the CYP1A1 and CYP1A2 linker regions between the N-termini and catalytic domains resulted in different depths of immersion of the N-termini in the membrane. The overlap of the distribution of positively charged residues in CYP1A2 (AVR) and negatively charged phospholipids was higher in the ordered than disordered microdomain. These findings identify three residues in the CYP1A N-terminus as a novel microdomain-targeting motif of the P450s and provide a mechanistic explanation for the differential microdomain localization of CYP1A.

Anion-Driven Bandgap Tuning of AgIn(SxSe1-x)2 Quantum Dots.

Accurate tuning of the electronic and photophysical properties of quantum dots is required to maximize the light conversion efficiencies in semiconductor-assisted processes. Herein, we report a facile synthetic procedure for AgIn(SxSe1-x)2 quantum dots with S content (x) ranging from 1 to 0. This simple approach allowed us to tune the bandgap (2.6-1.9 eV) and extend the absorption of AgIn(SxSe1-x)2 quantum dots to lower photon energies (near-IR) while maintaining a small QD size (∼5 nm). Ultraviolet spectroscopy studies revealed that the change in the bandgap is modulated by the electronic shifts in both the valence band and the conduction band positions. The negative overall charge of the as-synthesized quantum dots enabled us to make films of quantum dots on mesoscopic TiO2. Excited state studies of the AgIn(SxSe1-x)2 quantum dot films demonstrated a fast charge injection to TiO2, and the electron transfer rate constant was found to be 1.5-3.5 × 1011 s-1. The results of this work present AgIn(SxSe1-x)2 quantum dots synthesized by the one-step method as a potential candidate for designing light-harvesting assemblies.

Hepatoprotective Activity of Gingko biloba‐Mediated TiO2 NPs Against Acetaminophen‐Induced Albino Rats‐ In Vitro Studies

AbstractNumerous effects of “titanium dioxide nanoparticles (TiO2 NPs)” have been described and significantly utilized in complementary drugs for many decades. This study is conducted to analyze the therapeutic efficiency of TiO2 NPs against the acetaminophen‐(AMP) induced toxicity. TiO2 NPs were initially prepared using Ginkgo biloba leaf extract as reducing and stabilizing agent. The prepared TiO2 NPs were studied using various spectroscopic and microscopic techniques. AFM, TEM, XRD, and DLS studies have confirmed the formation of TiO2 NPs with size between 20 to 60 nm with negative surface charge of about −12 mV. Later, hepatoprotective studies were performed by administering AMP to albino mice only once at a dosage of 2 g/kg p.o. Post 24 h of AMP intoxication, the animals were treated orally with three different doses of TiO2 NPs (150, 100, and 50 mg/kg) or silymarin at an amount of 50 mg/kg p.o., administered only once. Post 24 h of last treatment, all the animals were surrendered to death. The group of mice administered with AMP displayed a substantial raise in the serum alkaline phosphatase (560 ± 31.90), lactate dehydrogenase (167 ± 10.17), aspartate amino transferase (251 ± 14.82), alanine amino transferase (326 + 18.96), bilirubin (2.2 ± 1.066), cholesterol (96.7 ± 6.2), and albumin (6.0 ± 1.27) in serum, which signified the liver damage. A considerably depleted level of glutathione (5.4 + 1.24) was detected in the mice intoxicated with AMP. The activities of catalase (33.2 ± 2.66) and superoxide dismutase (36 ± 2.93) declined after exposure to acetaminophen, resulting in oxidative stress in liver. The performance of adenosine triphosphatase (901 ± 50.7) and glucose‐6‐phosphatase (3.9 + 1.15) were considerably inhibited after administrating with AMP. On treating with TiO2 NPs, all the variables reversed significantly towards regular levels and were noticed to be nontoxic. The groups treated with TiO2 NPs exhibited less activity of ALT, AST, LDH, and SALP in serum, indicating the protective effect of TiO2 NPs to prevent liver damage. Exposure with TiO2 NPs inverted the cholesterol, albumin, and bilirubin levels towards normal, which is similar to silymarin treatment. TiO2 NPs exhibited a substantial change in tissue and blood biochemical parameters with that of control groups. These results indicate that TiO2 NPs possesses hepatoprotective properties that mitigate the hepatotoxicity induced by acetaminophen in rats. Hence, TiO2 NPs can be further utilized in the preparation of medicine against hepatic and renal diseases, post further clinical and preclinical studies.

Turing structured nanofiltration membrane fabricated by sulfonated cellulose nanocrystals mediated interfacial polymerization for enhanced permeability separation performance

Preparing Turing structure nanofiltration (NF) membrane is a representative strategy to obtain high permeability and selectivity. However, getting a tailored Turing structure by adjusting the interfacial polymerization (IP) process remains a significant challenge. Herein, sulfonated cellulose nanocrystals (S-CNC) with excellent hydrophilicity and negative surface charges were selected as aqueous phase additives to explore their influence on the morphology and composition of polyamide (PA) layer as well as its NF performance. It was found the surface morphology of the PA layer was effectively changed by adjusting the content of S-CNC in the aqueous phase. As the content of S-CNC increased, the Turing structure underwent a series of evolutions, from an “octopus leg structure” to a densely packed ridge-valley structure to a large ridge-valley structure filled with dense nodular particles. Finally, it changed back to the typical PA morphology of densely distributed nodular particles. By exploring the interaction between S-CNC and piperazine (PIP), it was demonstrated that the hydrogen bond and electrostatic interaction between S-CNC and PIP synergistically inhibited the diffusion of PIP, thus resulting in various Turing structures. Benefiting from the unique Turing structure, the prepared SCNF-10 NF membranes showed excellent permeability and separation properties with pure water permeability (PWP) of 16.9 LMH bar−1 and Na2SO4 rejection rate of 98.0 %. SCNF-10 NF membranes also exhibited good selectivity with a separation factor of 34.6 for mono-bivalent salts and long-term permeation stability. It is anticipated that this regulation strategy for various Turing structures preparation can provide a deeper understanding of the application of cellulose nanocrystals to NF membranes in the later stage, which will also promote the development of the high performance of NF membranes.

Delivering urokinase-type plasminogen activator using mulberry leaf exosomes enables thrombolysis and remodeling of venous microenvironments

In the treatment of thrombosis, conventional nanocarriers inevitably have problems, such as adverse reactions and difficulties in synthesis. Inspired by the concept of ‘medicine food homology,’ we extracted and purified natural exosomes from mulberry leaves as carriers for the delivery of urokinase-type plasminogen activator (uPA) for targeted therapy. The obtained mulberry leaf exosomes (MLE) possessed a desirable hydrodynamic particle size (119.4 nm), a uniform size distribution (polydispersity index = 0.174), and a negative surface charge (−23.3 mv). Before loading with uPA, MLE were grafted with cyclic RGD (cRGD) to selectively bind activated platelets for thrombus targeting. The cytometry studies revealed that MLE@cRGD has a high thrombus targeting ability about 74.3 %. Animal tests demonstrated that the delivered uPA could dissolve clots almost completely in femoral vein thrombosis models. In addition, MLE could remodel venous microenvironments by effectively eliminating reactive oxygen species (ROS) and promoting the phenotypic transformation of macrophages from M1 to M2 for venous tissue repair.

Novel methods for determination and manipulation of surface charges performed on an atmospheric DBD microplasma

Abstract In photo- and electrocatalysis it is already well-established that surface charges can alter chemical adsorption and reaction paths of the catalyst. However, the novel realm of plasma catalysis lacks experimental exploration regarding the impact of plasma-induced surface charges on catalytic processes. This paper paves the way by introducing a straightforward method for precisely charging the dielectric (catalyst) in a dielectric barrier discharge microplasma at atmospheric pressure. It additionally enables the determination of this surface charge avoiding artifacts or volume charge interference. Through pre-charging of the dielectric, the charges’ impacts on re-ignition and forming of charge equilibria during the discharge are investigated. Moreover, a laser-assisted operando technique is introduced to generate up to 15% of either positive or negative additional surface charges (compared to the default operation) within 3.5 μs after irradiation and potential for even higher yields. The charges’ origin and the plasma’s response to these laser-induced surface charges are explored.

On the coupled effect of a MIS-based anode and AlGaN-polarized super-junction to reduce the local electric field for AlGaN/GaN Schottky barrier diodes

This work employs advanced physical models with the help of technology computer-aided design tools to systematically design and investigate AlGaN/GaN Schottky barrier diodes (SBDs), focusing on enhancing forward conduction and reverse blocking characteristics. A recessed metal/insulator/III-nitride (MIS) anode is demonstrated to manage electric field distribution. The incorporation of a 1 nm thick Al2O3 layer enables a reduced leakage current and a significant increase in breakdown voltage (BV). Subsequently, tailored field plates (FPs) further improve the BV of the MIS SBD to ∼1650 V but strong electric field magnitude will be found at the edge of the FP. Hence, a MIS SBD with a graded AlGaN barrier layer (MIS-GA SBD) is designed, featuring a gradient decrease in Al content along the [0001] direction. The generation of negative polarization charges within the barrier functions as a super-junction, significantly homogenizing the electric field. As a result, the MIS-GA SBD achieves a remarkable BV exceeding 3500 V, highlighting its strong potential for high-voltage power electronic applications.

Competent CuS QDs@Fe MIL101 heterojunction for Sunlight-driven degradation of pharmaceutical contaminants from wastewater

In this study, we introduce an advanced photocatalyst developed by integrating copper sulfide quantum dots (CuS QDs) with an iron-based metal–organic framework (MOF), specifically Fe MIL101. The resulting CuS QDs@Fe MIL101 photocatalyst is engineered to efficiently degrade meloxicam (MLX) under simulated sunlight. The heterojunctions were generated by incorporating different concentrations of CuS QDs (5 %, 10 %, 15 %, 20 %, and 50 %) into the Fe MIL101 MOF matrix using the microwave-assisted hydrothermal method. The results of the XRD and the TEM studies confirmed the formation of the heterojunctions, which maintain the structural integrity of both CuS QDs and Fe MIL101. The BET measurements indicated a decrease in surface area upon CuS QDs incorporation, attributed to porés blockage and structural modifications. UV–Vis diffuse reflectance spectroscopy (DRS) revealed a redshift in absorption edges as CuS QDs content increased, enhancing visible light absorption. Photoluminescence (PL) investigations revealed that the 15 % CuS QDs@Fe MIL101 heterojunction had an effective charge separation and low recombination rates. The zeta potential analysis revealed a negative surface charge, indicating an overall electronegative characteristic. The photocatalytic performance, assessed through the degradation of MLX, demonstrated that the 15 % CuS QDs@Fe MIL101 heterojunction achieved the maximum degradation efficiency, reaching 96 % after 45 min of irradiation at a dosage of 0.1 g/L. This exceptional performance is attributed to potent charge separation, improving visible light absorption, high surface area and adsorption capacity. Various scavengers were used to investigate the roles of different reactive species, revealing holes as the predominant active species in the photocatalytic degradation process. These results highlight the potential of 15 % CuS QDs@Fe MIL101 heterojunctions as efficient photocatalyst for environmental remediation from pharmaceutical pollutants under simulated sunlight. These findings highlight the potential for application of CuS QDs@Fe MIL101 in real-world wastewater treatment systems, particularly in addressing pharmaceutical contaminants like meloxicam in industrial effluents.

Delivery of Avocado Seed Extract Using Novel Charge-Switchable Mesoporous Silica Nanoparticles with Galactose Surface Modified to Target Sorafenib-Resistant Hepatocellular Carcinoma.

Sorafenib-resistant (SR) hepatocellular carcinoma (HCC) is a current serious problem in liver cancer treatment. Numerous phytochemicals derived from plants exhibit anticancer activity but have never been tested against drug-resistant cells. Avocado seed extract (APE) isolated by maceration was analysed for its phytochemical composition and anticancer activity. Novel design charge-switchable pH-responsive nanocarriers of aminated mesoporous silica nanoparticles with conjugated galactose (GMSN) were synthesised for delivering APE and their physicochemical properties were characterized. The drug loading efficiency (%LE) and entrapment efficiency (%EE) were evaluated. Anticancer activity of APE loaded GMSN was measured against HCC (HepG2, Huh-7) and SR-HCC (SR-HepG2). Anticancer activity of APE against non-resistant HepG2 (IC50 50.9 ± 0.83 μg mL-1), Huh-7 (IC50 42.41 ± 1.88 μg mL-1), and SR-HepG2 (IC50 62.58 ± 2.29 μg mL-1) cells was confirmed. The APE loaded GMSN had a diameter of 131.41 ± 14.41 nm with 41.08 ± 2.09%LE and 44.96 ± 2.26%EE. Galactose functionalization (55%) did not perturb the original mesoporous structure. The GMSN imparted positive surface charges, 10.3 ± 0.61mV at acidic medium pH 5.5 along with rapid release of APE 45% in 2h. The GMSN boosted cellular uptake by HepG2 and SR-HepG2 cells, whereas the amine functionalized facilitated their endosomal escape. Their anticancer activity was demonstrated in non-resistant HCC and SR-HCC cells with IC50 values at 30.73 ± 3.14 (HepG2), 21.86 ± 0.83 (Huh-7), 35.64 ± 1.34 (SR-HepG2) μg mL-1, respectively, in comparison to the control and non-encapsulated APE. APE loaded GMSN is highly effective against both non-resistant HCC and SR-HCC and warrants further in vivo investigation.

Surface functionalized porous MXene (Ti3C2Tx)/Polyethyleneimine membrane for efficient osmotic energy conversion

The development of ion-selective membranes is crucial for achieving efficient osmotic power conversion in reverse electrodialysis system. However, balancing ion selectivity and ion permeability in membranes remains a challenge, limiting improvements in energy conversion efficiency for practical applications. In this study, we develop efficient cation exchange membranes by integrating versatile aromatic hydroxyl groups with MXene nanosheets and polyethyleneimine (PEI) into their lamellar structure. This approach holds promise for achieving non-swelling, high selectivity, and enhanced power density for osmotic energy conversion. The abundance positive surface charge within PEI molecules, combined with the 2D sub-nanochannels of MXene nanosheets, facilitates the biomimetic replication of channel size, chemical groups, and adjustable charge density in the resulting membranes. The fabrication of these membranes is easily achieved through simple hydrothermal, functionalization, and surface-charged techniques, suggesting promising scalability. These membranes exhibit remarkable stability against swelling in aqueous solutions for up to 25 days and demonstrate a high selectivity of 0.95 and a superior output power density of 18.3 W/m2 in artificial river water and seawater.

Remarks on 2D quantum cosmology

We consider two-dimensional quantum gravity endowed with a positive cosmological constant and coupled to a conformal field theory of large and positive central charge. We study cosmological properties at the classical and quantum level. We provide a complete ADM analysis of the classical phase space, revealing a family of either bouncing or big bang/crunch type cosmologies. At the quantum level, we solve the Wheeler-DeWitt equation exactly. In the semiclassical limit, we link the Wheeler-DeWitt state space to the classical phase space. Wavefunctionals of the Hartle-Hawking and Vilenkin type are identified, and we uncover a quantum version of the bouncing spacetime. We retrieve the Hartle-Hawking wavefunction from the disk path integral of timelike Liouville theory. To do so, we must select a particular contour in the space of complexified fields. The quantum information content of the big bang cosmology is discussed, and contrasted with the de Sitter horizon entropy as computed by a gravitational path integral over the two-sphere.

Selective adsorption behaviors and mechanisms of benzyl quaternary ammonium salt on quartz and gypsum: A combined experimental and theoretical study

Benzyl quaternary ammonium salt is an effective collector of quartz from gypsum. To investigate the selective collection mechanism of tetradecyl dimethyl benzyl ammonium chloride (TDBAC) for quartz from a microscopic view, the adsorption experiments, first-principles calculations based on density functional theory (DFT), and molecular dynamics (MD) simulation were performed in this work. The adsorption experiment results show that the adsorption capacity of TDBAC on the quartz surface was 1.6 × 10−6 mol/m2, much larger than that on the gypsum surface (1.0 × 10−7 mol/m2). The interaction energy of TDBAC with quartz surface was −20202.98 kJ/mol, much smaller than that with gypsum surface (-78.37 kJ/mol). DFT calculation results indicate that the quartz surface was more likely to interact with TDBAC through electrostatic attraction since the average negative charge and exposure oxygen density of the quartz surface were both greater than those of the gypsum surface. After the adsorption of TDBAC, there were hydrogen bonds formed between the hydrogen atoms in TDBAC and the oxygen atoms on the quartz surface. This work confirmed that the highly selective adsorption of TDBAC on quartz surface was attributed to the strong electrostatic attraction and hydrogen-bond interaction.

Enhancing separation performance of thin film nanocomposite membranes by self-etching of polydopamine-modified calcium carbonate during interfacial polymerization process

The acid-accepting and gas-generating properties, along with the formation of extensive nanovoids, make CaCO3 nanoparticles attractive as sacrificial nanofillers for fabricating thin-film composite (TFN) nanofiltration membranes. However, challenges such as severe agglomeration and limited acid etching efficiency of the nanoparticles hinder the pursuit of superior membrane performance. In this study, the dispersion and compatibility of CaCO3 nanoparticles within the membrane matrix were improved by modifying them with a polydopamine (PDA) coating. The abundant phenolic hydroxyl groups of PDA enhanced the hydrophilicity and negative charges of membrane surface. Additionally, the PDA capsule increased the etching extent of the CaCO3 nanoparticles by improving the nanoparticle dispersion and generating additional acid, which created sufficient water channels within the polyamide layer. It was demonstrated that incorporating 45 μg/cm2 of PDA-modified CaCO3 nanoparticles doubled the water permeance to 16.7 LMH/bar, while maintaining a low molecular weight cut-off of 249 Da and achieving rejections over 90% for five types of per- and polyfluorinated substances. The PDA modification also overcame the membrane stability issue caused by the agglomerated CaCO3 nanoparticles. This study provides a novel strategy for applying properly modified self-etching nanofillers in TFN membrane development, showing great potential for water treatment applications.

Mussel-inspired co-deposition of catechol-amine and graphene oxide (GO) modified anion exchange membranes (AEMs) for antifouling

Mussel-inspired co-deposition has many applications in surface modification of polymer membranes. Organic fouling of ion exchange membranes is one of the common issues that hinder electrodialysis treatment of industrial wastewater. In this work, anion exchange membranes were surface-modified by the mussel-inspired co-deposition of catechol-amine and graphene oxide (GO) nanosheets. Results showed that co-deposition with catechol (CA) and m-phenylenediamine (MPD) as reactant monomers rapidly generated modifying layer on the AEM surface. And the addition of GO into co-deposition helped improve the homogeneity and reduce polymer particle aggregation. The synergistic effect of catechol-amine and GO nanosheets was beneficial to form uniform modifying layer with improved hydrophilicity and negative charge density of membrane surface. In eletrodialysis experiments with sodium dodecyl benzene sulfonate (SDBS) as model foulants, GO-CA-MPD-3h modified AEM maintained high desalination rate close to that without folants, indicating good modifying antifouling performance. Mussel-inspired co-deposition of catecholamines and functional materials give new insights into membrane modificatin through a feasible and cost-effective method

Effect of CO2 mixing on the rheological and electrochemical properties of fresh mortar at the early age

The study aimed to elucidate the mechanism behind rheological modification due to CO2 mixing at the mixing and post-mixing stages from an electrochemical perspective. The results indicated that CO2 mixing reduced the flowability while increasing penetration resistance and static yield stress. The electrostatic attraction between particles with opposite surface charges and the bridging effect of calcium carbonate constitute the primary factors for influencing the rheological properties of mortar at an early age. The altered surface charge of carbonized cement particles, primarily resulting from CO2 injection lowering the pH and ion concentration, reversed the zeta potential of particles from the traditionally negative charge (-3.59 mV) to a positive value (+13.3 mV). Furthermore, CO2 mixing further enhanced the dissolution of cement particles and accelerated the hydration process, thereby increasing the rate of structural build-up. CO2 mixing was demonstrated to be a potential rheological modifier for 3D-printed concrete applications.