Repulsive Electrostatic Interactions Research Articles

A diffused double-layer model of bulk nanobubbles in aqueous NaCl solutions

Bulk nanobubbles, known for their extraordinary stability due to their electrically charged surface, still have an elusive mechanism. This research examines the surface electrical properties of oxygen nanobubbles in various NaCl solution concentrations, utilizing a diffused double-layer model. The process involves the creation of nanobubbles through the hydrodynamic cavitation technique, followed by an assessment of their size and zeta potential. To quantify their influence on nanobubble stability, the thickness of the double layer, the density of surface charge, electrostatic repulsion and attractive force, and interaction energy between bubbles are evaluated. The results show that adding NaCl to nanobubble solutions increases bubble size while decreasing their negative zeta potential, minimizing repulsive electrostatic interactions among the bubbles. These findings are consistent with the diffused double-layer theory. Specifically, higher NaCl concentrations in solutions lead to thinner double layers and decreased energy barriers. Observing nanobubble stability in a 10 mM NaCl solution over six months reveals a decrease in bubble size accompanied by an increase in zeta potential. This rise in negative zeta potential correlates with changes in Debye length and ionic strength, inversely proportional to the solution's conductivity, likely due to reduced NaCl concentration over time. Furthermore, the pressure differential at the bubble interface is insufficient to overcome the pressure caused by the liquid's surface tension, indicating potential limitations in applying the diffused double-layer model. This highlights the need for further investigation to establish a more comprehensive understanding of the mechanical stability of bulk nanobubbles.

Static magnetic fields enhance microbial aggregation and adhesion to promote aerobic granulation

Aerobic granulation promoted by static magnetic field had been widely noticed because of its environmental friendliness and economic feasibility. The mechanism of strengthening aerobic granulation by static magnetic field needed to be clarified. Consequently, this study aspired to promote aerobic granulation by loading different intensities of static magnetic fields (R1: 0 mT, R2: 10 mT, R3: 50 mT), and elucidate the potential mechanism of static magnetic fields enhancement in terms of microbial interactions, chemical structure and adhesion performance of extracellular polymeric substances (EPS), metabolic pathways. Compared to R1 (day 45), R3 and R2 completed granulation at day 34 and day 42 respectively. Under the influence of magnetic fields, the interfacial adsorption free energy between microorganisms decreased from −55.88 mJ/m2 (R1) to −64.32 mJ/m2 (R2) and −75.02 mJ/m2 (R3), and the energy barriers preventing microbial aggregation in R2 and R3 were reduced. This was attributed to the fact that magnetic fields induced microorganisms to secrete highly hydrophobic EPS and enhanced adhesion to metal cations (Ca2+, Mg2+, etc.), resulting in an enhanced hydrophobic interaction and a reduced electrostatic repulsion interaction between microorganisms. Furthermore, magnetic fields increased the relative abundance of EPS-producing bacteria (Chryseobacterium, Candidatus_Competibacter, Thauera, Zoogloea) and upregulated the abundance of functional genes associated with the synthesis of hydrophobic amino acids (trpA, trpB, ADT, ilvE, proC, metH) and energy supply (mdh, cs, acn, IDH, sucA, frdA). The above results proved that the static magnetic field promoted aerobic granulation by enhancing microbial aggregation and adhesion, which provided sufficient theoretical support for the construction of a new wastewater treatment plant.

Using the benzenepolycarboxylic acid (BPCA) method to assess activated biochars and their PFAS sorption abilities

Activated carbon (AC) has important industrial and environmental applications as it has excellent abilities to sorb contaminants such as per- and polyfluoroalkyl substances (PFAS). Current research aims to develop activated biochars (AB) from renewable biomass to replace AC that is produced from fossil feedstock. Both AC and AB are primarily comprised of condensed aromatic carbon (ConAC), the component that is the focus of this study. ConAC is characterized to determine its relationship with biochar activation conditions and PFAS sorption, which are understudied at present.Benzenepolycarboxylic acid (BPCA) markers for ConAC were quantified in steam-activated biochars (AB-Steam) and carbon dioxide-activated biochars (AB-CO2) prepared from waste timber at different temperatures (800, 850, 900 °C) and molar ratios of feedstock-carbon:steam (0.50 – 1.25). A non-activated biochar was also included as a reference. ConAC relative to total organic carbon content was higher in AB-Steam than in AB-CO2 (92 ± 2 % vs. 81 ± 11%). The ratio of benzenehexa- (B6CA) to benzenepentacarboxylic (B5CA) acids revealed that AB-Steam also had larger ConAC clusters than AB-CO2. These findings provide novel evidence that steam activation is more effective than CO2 activation in creating ConAC.To assess how ConAC impacts AB sorption abilities, AB-Steam were used to remediate PFAS from contaminated soils. The observed strong correlations between ConAC content and sorption of long-chain PFAS suggest the importance of hydrophobic interactions between PFAS tails and ConAC. Poor correlations for short-chain PFAS, on the other hand, indicated the existence of electrostatic repulsion interactions between PFAS head groups and ConAC. Collectively, these results explain the great ability of AB-Steam to sorb PFAS from contaminated soils (up to 100% remediation). More broadly, this work demonstrates that the BPCA method can be a valuable tool to assess the quality of biochars and other carbonaceous sorbents in relation to their production conditions or contaminant sorption abilities.

Affinity-based engineering of carbon nanotube embedded polyamide membranes for simultaneous desalination and boron removal

Reverse osmosis (RO) is the leading technology for obtaining drinking and irrigation water from seawater. Although currently developed RO membranes achieve high salt rejection; several challenges exist, such as permselectivity trade-off, biological/chemical contamination, and insufficient retention of small and neutral molecules like boric acid. Due to its toxicity to living organisms and strictly monitored levels in potable water, removal of boron has gained considerable attention in RO industry. Thin film nanocomposite (TFN) membranes have emerged by incorporating nanomaterials with superior water/salt selectivity into polyamide (PA) layer of composite membranes. For the first time, our group investigated the potential of carboxylated carbon nanotube (CNT) embedding in the selective layer of TFN membranes for boron removal. Within this frame, we hypothesize that embedding fillers with low boron affinity accompanied by high water permeability in the selective layer of TFN membranes improves boron removal without suffering from the permselectivity trade-off. In this study, we investigated the boron removal performance of functionalized CNT (f-CNT) embedded TFN membranes. Initially, CNTs were functionalized with three different functional groups (namely, biotin (BIO), 8-amino caprylic acid (ACA), and zwitterion (ZWT)) to narrow down the tube entrance, provide repulsive electrostatic interactions with boron, and interfere with the hydrogen bonding between water and boric acid molecules. Then, TFN membranes incorporating f-CNTs were fabricated, characterized, and tested. Showing high compatibility with PA, ZWT functionalization has increased water/boron selectivity of TFN membranes by 66% and water permeability by 44%, while maintaining the salt rejection at 98%. Furthermore, we employed molecular dynamics simulations and potential of mean force calculations to elucidate the boron exclusion mechanism in f-CNTs. With its flexible structure and “gate-keeper” ability, ZWT functional group was found to show the highest energy barrier against boron transport. Hence, engineering CNT/PA TFN membranes to promote steric hindrance and decrease solute affinity is promising for efficient removal of detrimental small molecules from seawater.

Direct in-situ insights into the asymmetric surface reconstruction of rutile TiO2 (110)

The reconstruction of rutile TiO2 (110) holds significant importance as it profoundly influences the surface chemistry and catalytic properties of this widely used material in various applications, from photocatalysis to solar energy conversion. Here, we directly observe the asymmetric surface reconstruction of rutile TiO2 (110)-(1×2) with atomic-resolution using in situ spherical aberration-corrected scanning transmission electron microscopy. Density functional theory calculations were employed to complement the experimental observations. Our findings highlight the pivotal role played by repulsive electrostatic interaction among the small polarons −formed by excess electrons following the removal of neutral oxygen atoms− and the subsequent surface relaxations induced by these polarons. The emergence and disappearance of these asymmetric structures can be controlled by adjusting the oxygen partial pressure. This research provides a deeper understanding, prediction, and manipulation of the surface reconstructions of rutile TiO2 (110), holding implications for a diverse range of applications and technological advancements involving rutile-based materials.

Clustered surface amino acid residues modulate the acid stability of GH10 xylanase in fungi

Acidic xylanases are widely used in industries such as biofuels, animal feeding, and fruit juice clarification due to their tolerance to acidic environments. However, the factors controlling their acid stability, especially in GH10 xylanases, are only partially understood. In this study, we identified a series of thermostable GH10 xylanases with optimal temperatures ranging from 70 to 90 °C, and among these, five enzymes (Xyn10C, Xyn10RE, Xyn10TC, Xyn10BS, and Xyn10PC) exhibited remarkable stability at pH 2.0. Our statistical analysis highlighted several factors contributing to the acid stability of GH10 xylanases, including electrostatic repulsion, π-π stacking, ionic bonds, hydrogen bonds, and Van der Waals interactions. Furthermore, through mutagenesis studies, we uncovered that acid stability is influenced by a complex interplay of amino acid residues. The key amino acid sites determining the acid stability of GH10 xylanases were thus elucidated, mainly concentrated in two surface regions behind the enzyme active center. Notably, the critical residues associated with acid stability markedly enhanced Xyn10RE’s thermostability by more than sixfold, indicating a potential acid-thermal interplay in GH10 xylanases. This study not only reported a series of valuable genes but also provided a range of modification targets for enhancing the acid stability of GH10 xylanases.Key points• Five acid stable and thermostable GH10 xylanases were reported.• The key amino acid sites, mainly forming two enriched surface regions behind the enzyme active center, were identified responsible for acid stability of GH10 xylanases.• The finding revealed interactive amino acid sites, offering a pathway for synergistic enhancement of both acid stability and thermostability in GH10 xylanase modifications.

Adaptive Capacity of a DNA Polymerase Clamp-loader ATPase Complex.

The ability of mutations to facilitate adaptation is central to evolution. To understand how mutations can lead to functional adaptation in a complex molecular machine, we created a defective version of the T4 clamp-loader complex, which is essential for DNA replication. This variant, which is ∼5,000-fold less active than the wild type, was made by replacing the catalytic domains with those from another phage. A directed-evolution experiment revealed that multiple substitutions to a single negatively charged residue in the chimeric clamp loader-Asp 86-restore fitness to within ∼20-fold of wild type. These mutations remove an adventitious electrostatic repulsive interaction between Asp 86 and the sliding clamp. Thus, the fitness decrease of the chimeric clamp loader is caused by a reduction in affinity between the clamp loader and the clamp. Deep mutagenesis shows that the reduced fitness of the chimeric clamp loader is also compensated for by lysine and arginine substitutions of several DNA-proximal residues in the clamp loader or the sliding clamp. Our results demonstrate that there is a latent capacity for increasing the affinity of the clamp loader for DNA and the sliding clamp, such that even single-point mutations can readily compensate for the loss of function due to suboptimal interactions elsewhere.

Unified understanding and mitigation of detrimental phase transition in cobalt-free LiNiO2

Ni-enriched layered materials are used as electrode materials of Li-ion batteries for electric vehicle applications. Stoichiometric LiNiO2 with cationic Ni3+/Ni4+ redox is the ideal electrode material, but the gradual loss of capacity at the high voltage region, associated with Ni ion migration, hinders its use for practical applications. Therefore, to improve electrode reversibility of LiNiO2, less abundant Co ions and/or other electrochemically inactive ions, e.g., Al3+ ions, are in part substituted for Ni ions. Nevertheless, a unified understanding of improvement by metal substitution is as yet not established. In this study, the origin causing detrimental phase transition in LiNiO2 is discussed through the detailed analysis on LiNiO2 integrated with nanosized Li3PO4 derived from a metastable and rocksalt LiNiO2–Li3PO4 solid solution sample. LiNiO2 derived from the metastable rocksalt oxide has approximately 6 % anti-site defects, and the particle size growth is suppressed by uniformly dispersed nanosized Li3PO4. In low crystallinity LiNiO2 with partial structural disordering, the Ni ion migration to tetrahedral sites is effectively suppressed because of repulsive electrostatic interaction from Ni ions in Li layers. Moreover, from these findings, non-stoichiometric Li0.975Ni1.025O2 with smaller particle size has been directly synthesized without high-energy milling and Li3PO4 integration, and significant improvement of electrode reversibility is achieved. Electrode reversibility of non-stoichiometric Li0.975Ni1.025O2 is further improved through surface stabilization in a highly concentrated electrolyte solution. The unified understanding of deterioration mechanisms for LiNiO2 offers a new criterion to design Co-free LiNiO2 without metal substitution, leading to full utilization of a reversible capacity for layered materials.

Photocatalytic Reduction of CO2 into CO with Cyclometalated Pt(II) Complexes of N^C^N Pincer Dipyridylbenzene Ligands: A DFT Study.

In this work, density functional theory (DFT) calculations were employed to study the photocatalytic reduction of CO2 into CO using a series of Pt(II) square planar complexes with the general formula [Pt(5-R-dpb)Cl] (dpb = 1,3-di(2-pyridyl)benzene anion, R = H, N,N-dimethylaniline,T thiophene, diazaborinine). The CO2-into-CO conversion process is thought to proceed via two main steps, namely the photocatalytic/reduction step and the main catalytic step. The simulated absorption spectra exhibit strong bands in the range 280-460 nm of the UV-Vis region. Reductive quenching of the T1 state of the complexes under study is expected to be favorable since the calculated excited state redox potentials for the reaction with sacrificial electron donors are highly positive. The redox potentials reveal that the reductive quenching of the T1 state, important to the overall process, could be modulated by suitable changes in the N^C^N pincer ligands. The CO2 fixation and activation by the three coordinated Pt(II) catalytically active species are predicted to be favorable, with the Pt-CO2 bond dissociation energies D0 in the range of -36.9--10.3 kcal/mol. The nature of the Pt-CO2 bond of the Pt(II) square planar intermediates is complex, with covalent, hyperconjugative and H-bonding interactions prevailing over the repulsive electrostatic interactions. The main catalytic cycle is estimated to be a favorable exergonic process.

Insight into the adsorption and co-adsorption of PPCPs on Ti3C2Tx MXene: Behaviors, mechanisms and application potentials

In this study, four pharmaceutical compounds including sulfamethoxazole (SMX), oxytetracycline (OTC), ciprofloxacin (CIP), and ibuprofen (IBU) with different functional groups and pKa, were selected as representative pollutants to systematically investigate the Pharmaceutical and Personal Care Products (PPCPs) adsorption on a nanomaterial Ti3C2Tx MXene in simulated solution and real surface water. The results show that Ti3C2Tx was an excellent PPCPs adsorbent, but the process was affected by the characteristics of pollutants pronouncedly, the obtained maximum adsorption capacity were OTC (210.97 mg/g) > IBU (185.05 mg/g) > CIP (160.60 mg/g) > SMX (68.12 mg/g). Specially, the charge screen effect caused Ti3C2Tx precipitation during CIP adsorption. The response surface methodology analysis indicates that initial solution pH (3–11) had significant effects, while the influence of humic acid (0–10 mg/L) or sodium chloride (0–10 mg/L) was limited, and the interactions between these factors was slight. In the co-adsorption process, the competitive effects reduced the adsorption of SMX and IBU, however, the enhanced positive ionization and the possible electrostatic repulsive interactions promoted that of CIP and OTC. In real surface water, although the influence of natural organic matters was negligible, the preferential adsorption of background metal ions such as aluminum and calcium ions reduced the adsorption capacity of the selected PPCPs by approximately 29.9 % to 88.4 %. Moreover, the adsorbent characterization conjoined with performance examination imply that electrostatic attraction dominated the Ti3C2Tx adsorption of PPCPs, and hydrogen bonding interactions as well as surface complexation might also contributed. These observations suggest that Ti3C2Tx MXene has the potential for use as adsorbent to eliminate aqueous PPCPs, nevertheless, the interference of co-existing metal ions and the stability of adsorbent were also noteworthy.

Design of Carbon Aggregation Structure in Polymer Electrolyte Fuel Cell Catalyst Ink by Solvent Hydrophilicity

Controlling the porous structure of the cathode catalyst layer in a polymer electrolyte fuel cell is essential to reduce the reaction and mass transport resistance of the oxygen reduction reaction. As the catalyst layer is a coating of a catalyst ink, the aggregation structure of platinum-supported carbon (Pt/C) and ionomer in ink is a key property for achieving the optimal catalyst layer.1 Previous studies reported that the weight fraction of water in solvents could control aggregation structure in ink.2-4 For example, Kumano et al.2 reported that increasing the water ratio to 1-propanol enhances the ionomer adsorption on Pt/C (Γ) and dispersion of Pt/C, causing the lowering of the viscosity of the inks. Based on the results, they speculated that water repels ionomers and promotes their adsorption on Pt/C particles. They further speculated that the ionomers adsorbed on the Pt/C particles induce repulsive interactions between Pt/C particles via electrostatic repulsive interactions among sulfonate groups of adsorber ionomers. By the enhanced repulsive interactions, Pt/C particles are dispersed, and viscosity decreases. The discussion in the previous study likely indicates that the hydrophilicity of the solvent is an essential factor controlling the aggregation structure of catalyst ink. Here, we verify this hypothesis. As a universal indicator of the hydrophilicity, we adopt the hydrogen-bond term HSP-δH of the Hansen solubility parameters. We examined how HSP-δH is correlated to the ionomer adsorption ratio to Pt/C (Γ), viscoelasticity of ink, and structural properties of ink measured by ultra-small angle X-ray scattering (USAXS).The catalyst inks were prepared by mixing Pt/C (TEC10V30E, TKK), Nafion 20 wt% solution (DE2020, Chemours), ultrapure water, and three different alcohols [ethanol (EtOH), 1-propanol (PrOH) and diacetone alcohol (DAA)]. The water weight fraction in the solvents was set to 25 - 85 wt%. Γ is plotted as a function of HSP-δH in Fig. 1. Regardless of the alcohol species, Γ increases with increasing HSP-δH. The trend is consistent with the previously reported trend observed in the mixtures of water and 1-propanol. Figures 2 (a) and (b) show the equilibrium storage modulus G’0 obtained by the rheometer and the fractal dimension D 2 of agglomerates of Pt/C particles in ink as functions of Γ. Here, D 2 is determined by fitting the unified model5 to the USAXS spectrum obtained by the synchrotron radiation (Spring-8, Japan). Both decreases with the increase of Γ. The lowering of D 2 indicates that the agglomerates of Pt/C particles are dispersed and turn to less-structured particles, as schematically shown in Fig. 2 (c). By the dispersion, G’0 decreases. Accordingly, the hydrophilicity, indeed, promotes the ionomer adsorption, and the adsorption induces the dispersion. The hydrophilicity is a key factor controlling the structure and rheology of the catalyst ink, and HSP-δH is a universal descriptor of hydrophilicity. Reference K. B. Hatzell, M. B. Dixit, S. A. Berlinger, and A. Z. Weber, J. Mater. Chem. A, 5 (39), 20527-20533 (2017). N. Kumano, K. Kudo, Y. Akimoto, M. Ishii, and H. Nakamura, Carbon, 169 429-439 (2020). S. Takahashi, T. Mashio, N. Horibe, K. Akizuki, and A. Ohma, ChemElectroChem, 2 (10), 1560-1567 (2015). T. Van Cleve, S. Khandavalli, A. Chowdhury, S. Medina, S. Pylypenko, M. Wang, K. L. More, N. Kariuki, D. J. Myers, A. Z. Weber, S. A. Mauger, M. Ulsh, and K. C. Neyerlin, ACS Appl Mater Interfaces, 11 (50), 46953-46964 (2019). G. Beaucage, H. K. Kammler, and S. E. Pratsinis, J. Appl. Crystallogr., 37 (4), 523-535 (2004). Figure captions Figure 1 Dependence of the ionomer adsorption ratio Γ on the HSP-δH of the catalyst ink solvent. Figure 2 (a) Γ dependence of the equilibrium storage modulus G’0 of the catalyst inks. G’0 is plotted on a logarithmic scale. G’0 values of inks that are not measurable due to being less than the measurable lower limit are conventionally described as 0. (b) Γ dependence of the mass fractal D 2 of Pt/C aggregates in the inks. (c) Schematic illustration of the aggregation structure of Pt/C in the solvents. Figure 1

Electrostatic interaction and regioselectivity enhancement in proline cis-4-hydroxylase for L-pipecolic acid hydroxylation

L-Proline cis-4-hydroxylase (cis-P4H), a non-heme Fe2+/α-ketoglutarate-dependent dioxygenase (KDD), finds application in proline C4 hydroxylation and selective L-pipecolic acid (L-PA) C5 hydroxylation. Nonetheless, its regioselectivity is often ambiguous, yielding nearly equal amounts of cis-5/cis-3 hydroxylated L-PA isomers, posing challenges in separation and purification. In this study, we selected Kordia jejudonensis proline hydroxylase (KjPH) for modification and investigated the electrostatic effect's molecular mechanism on its regioselectivity. Through sequence and catalytic domain alignment of KjPH (cis-5/cis-3 = 20:1), SmP4H (cis-5/cis-3 = 1:1, from Sinorhizobium meliloti), and MlP4H (cis-5/cis-3 = 1:7, from Mesorhizobium loti), we identified four non-conserved key residues (Y35, S57, F95, and C97). We confirmed that F95 in KjPH plays a pivotal role in affecting regioselectivity. The single-site variant F95Y significantly enhanced regioselectivity, increasing the cis-5/cis-3 ratio from 20:1 to 55:1. Molecular dynamics simulations unveiled that the improved regioselectivity of the F95Y variant primarily resulted from the electrostatic repulsive interaction, which increased the distance between the substrate's C3 site and the Fe2+ catalytic core.

Difference in the Charge-Separation Energetics between Distinct Conformers in the PixD Photoreceptor.

Blue light using flavin (BLUF) domain proteins are photoreceptors in various organisms. The PixD BLUF domain can adopt two conformations, W91out and W91in, with Trp91 either proximal or distal to flavin (FMN). Using a quantum mechanical/molecular mechanical/polarizable continuum model approach, the energetics of charge-separated and biradical states in the two conformations were investigated. In the W91out conformation, the charge-separated state (FMN•-) is more stable than the photoexcited state (FMN*), whereas it is less stable due to an electrostatic repulsive interaction with the Ser28 side chain in the W91in conformation. This leads to a lower activation energy for the charge separation in the W91out conformation, resulting in a faster charge separation compared to that in the W91in conformation. In the W91out conformation, the radical state (FMNH•) is more stable than FMN•- and forms from FMN•-, leading to reorientation of the Gln50 side chain adjacent to FMN and formation of a hydrogen bond between Gln50 and FMN. Subsequently, a signaling state forms through charge recombination. In contrast, in the W91in conformation, FMN•- cannot proceed further, returning to the dark-adapted state, as FMNH• is less stable. Thus, formation of the signaling state exclusively occurs in the W91out conformation.

The conformational phase diagram of charged polymers in the presence of attractive bridging crowders.

Using extensive molecular dynamics simulations, we obtain the conformational phase diagram of a charged polymer in the presence of oppositely charged counterions and neutral attractive crowders for monovalent, divalent, and trivalent counterion valencies. We demonstrate that the charged polymer can exist in three phases: (1) an extended phase for low charge densities and weak polymer-crowder attractive interactions [Charged Extended (CE)]; (2) a collapsed phase for high charge densities and weak polymer-crowder attractive interactions, primarily driven by counterion condensation [Charged Collapsed due to Intra-polymer interactions [(CCI)]; and (3) a collapsed phase for strong polymer-crowder attractive interactions, irrespective of the charge density, driven by crowders acting as bridges or cross-links [Charged Collapsed due to Bridging interactions [(CCB)]. Importantly, simulations reveal that the interaction with crowders can induce collapse, despite the presence of strong repulsive electrostatic interactions, and can replace condensed counterions to facilitate a direct transition from the CCI and CE phases to the CCB phase.

Ion binding with charge inversion combined with screening modulates DEAD box helicase phase transitions

Membraneless organelles, or biomolecular condensates, enable cells to compartmentalize material and processes into unique biochemical environments. While specific, attractive molecular interactions are known to stabilize biomolecular condensates, repulsive interactions, and the balance between these opposing forces, are largely unexplored. Here, we demonstrate that repulsive and attractive electrostatic interactions regulate condensate stability, internal mobility, interfaces, and selective partitioning of molecules both invitro and in cells. We find that signaling ions, such as calcium, alter repulsions between model Ddx3 and Ddx4 condensate proteins by directly binding to negatively charged amino acid sidechains and effectively inverting their charge, in a manner fundamentally dissimilar to electrostatic screening. Using a polymerization model combined with generalized stickers and spacers, we accurately quantify and predict condensate stability over a wide range of pH, salt concentrations, and amino acid sequences. Our model provides a general quantitative treatment for understanding how charge and ions reversibly control condensate stability.

Electron‐Withdrawing Substituents Allow Boosted NIR‐II Fluorescence in J‐Type Aggregates for Bioimaging and Information Encryption

AbstractDeveloping molecular fluorophores with enhanced fluorescence in aggregate state for the second near‐infrared (NIR‐II) imaging is highly desirable but remains a tremendous challenge due to the lack of reliable design guidelines. Herein, we report an aromatic substituent strategy to construct highly bright NIR‐II J‐aggregates. Introduction of electron‐withdrawing substituents at 3,5‐aryl and meso positions of classic boron dipyrromethene (BODIPY) skeleton can promote slip‐stacked J‐type arrangement and further boost NIR‐II fluorescence of J‐aggregates via increased electrostatic repulsion and intermolecular hydrogen bond interaction. Notably, NOBDP‐NO2 with three nitro groups (−NO2) shows intense NIR‐II fluorescence at 1065 nm and high absolute quantum yield of 3.21 % in solid state, which can be successfully applied in bioimaging, high‐level encoding encryption, and information storage. Moreover, guided by this electron‐withdrawing substituent strategy, other skeletons (thieno‐fused BODIPY, aza‐BODIPY, and heptamethine cyanine) modified with −NO2 are converted into J‐type aggregates with enhanced NIR‐II fluorescence, showing great potential to convert aggregation caused emission quenching (ACQ) dyes into brilliant J‐aggregates. This study provides a universal method for construction of strong NIR‐II emissive J‐aggregates by rationally manipulating molecular packing and establishing relationships among molecular structures, intermolecular interactions, and fluorescence properties.

Electron-Withdrawing Substituents Allow Boosted NIR-II Fluorescence in J-Type Aggregates for Bioimaging and Information Encryption.

Developing molecular fluorophores with enhanced fluorescence in aggregate state for the second near-infrared (NIR-II) imaging is highly desirable but remains a tremendous challenge due to the lack of reliable design guidelines. Herein, we report an aromatic substituent strategy to construct highly bright NIR-II J-aggregates. Introduction of electron-withdrawing substituents at 3,5-aryl and meso positions of classic boron dipyrromethene (BODIPY) skeleton can promote slip-stacked J-type arrangement and further boost NIR-II fluorescence of J-aggregates via increased electrostatic repulsion and intermolecular hydrogen bond interaction. Notably, NOBDP-NO2 with three nitro groups (-NO2 ) shows intense NIR-II fluorescence at 1065 nm and high absolute quantum yield of 3.21 % in solid state, which can be successfully applied in bioimaging, high-level encoding encryption, and information storage. Moreover, guided by this electron-withdrawing substituent strategy, other skeletons (thieno-fused BODIPY, aza-BODIPY, and heptamethine cyanine) modified with -NO2 are converted into J-type aggregates with enhanced NIR-II fluorescence, showing great potential to convert aggregation caused emission quenching (ACQ) dyes into brilliant J-aggregates. This study provides a universal method for construction of strong NIR-II emissive J-aggregates by rationally manipulating molecular packing and establishing relationships among molecular structures, intermolecular interactions, and fluorescence properties.

Insight into the influence of surface wettability on flotation properties of solid particles – Critical contact angle in flotation

Bubble-particle attachment is a fundamental element of the flotation process, and its occurrence depends on the stability of the thin liquid film separating these objects. In this study, the effect of surface wettability on the stability of liquid film and subsequent attachment was investigated by flotation of glass microspheres (70–110 μm) with controlled contact angles (9–89°) in a Hallimond tube. Additionally, pH was varied to determine the electrostatic interactions between the bubble and particles. The results showed that for the flotation process to take place, the minimum (critical) value of the contact angle must be exceeded. This value was found to be ca. 25° when the electrostatic interactions were either attractive or weakly repulsive and as high as 62° for strong repulsive electrostatic interactions. These findings highlight the role of attractive hydrophobic interactions, whose importance increases with increasing surface contact angle in the context of stability of thin liquid films.

Review of Separator Modification Strategies: Targeting Undesired Anion Transport in Room Temperature Sodium–Sulfur/Selenium/Iodine Batteries

AbstractRechargeable sodium–sulfur/selenium/iodine (Na–S/Se/I2) batteries are regarded as promising candidates for large‐scale energy storage systems, with the advantages of high energy density, low cost, and environmental friendliness. However, the electrochemical performances of Na–S/Se/I2 batteries are still restricted by several inherent issues, including the “shuttle effect” of polysulfides/polyselenides/polyiodides (PSs/PSes/PIs), sluggish kinetics of the conversion reactions at the cathodes, and Na dendrite growth at the anodes. Among these challenges, uncontrolled “shuttle effect” of PSs/PSes/PIs is a major contributing factor for the irreversible loss of active cathode materials and severe side reactions on Na metal anodes, leading to rapid failure of the batteries. Separator modification has been demonstrated to be an effective strategy to suppress the shuttling of PSs/PSes/PIs. Herein, the latest achievement in modifying separators for high‐performance Na–S/Se/I2 batteries is comprehensively reviewed. The reaction mechanisms of each battery system are first discussed. Then, strategies of separator modification based on the different functions for regulating the transportation of PSs/PSes/PIs are summarized, including applying electrostatic repulsive interaction, introducing conductive layers, improving sieving effects, enhancing chemisorption capability, and adding efficient electrocatalysts. Finally, future perspectives on the practical application of modified separators in high‐energy rechargeable batteries are provided.

Imidazole-octyl mixed-mode stationary phase based on macroporous silica for the purification of ovomucoid and ovotransferrin.

A process-simplified hard template approach was established to synthesize the monodisperse macroporous silica microspheres with homogeneous structures by twice alkali-thermal treatment and calcination routes. Porous vinyl-functionalized polysesquioxane microspheres (V-PMSQ) were synthesized through a hydrolyzation-polycondensation method and used as templates. The template particles with large aperture and high pore volume were obtained by adjusting the pH value and reaction time of the twice alkali-thermal reaction. After calcination, monodisperse silica microspheres with an average pore size of 30nm, homogeneous pore structures, and narrow particle size distribution were fabricated, which can be directly used as chromatographic matrices without classification. After that, a new reversed-phase/strong anion-exchange (RP/SAX) mixed-mode stationary phase Sil-S-VOIM was prepared by bonding the 1-vinyl-3-octyl-imidazole ligands to the above silica microspheres through a "thiol-ene" click reaction. The performance of the Sil-S-VOIM column was evaluated by one acidic protein (transferrin) and two basic proteins (lysozyme, α-chymotrypsin) and compared to a single imidazole-modified Sil-S-VIM column and an octyl-modified Sil-C8 column, respectively. Due to the synergistic effect of electrostatic repulsion and hydrophobic interactions, baseline separations of the above proteins were observed only on the Sil-S-VOIM column, with resolutions of 2.55 and 2.01 between lysozyme and transferrin, and between transferrin and α-chymotrypsin, respectively, indicating good selectivity and separation ability compared with single-mode stationary phases. It was applied to the isolation of egg white samples with peaks identified by SDS-PAGE and MALDI-TOF-MS. The results showed that the selective retention and isolation of ovomucoid and ovotransferrin were successfully achieved, with yields of 78.8% and 67.2%, respectively. The protocol described in this work is simpler, faster, and has higher protein recovery. Overall, this new mixed-mode stationary phase provided a promising potential for the separation and determination of intact proteins.