Pub Date : 2026-02-09DOI: 10.1021/acs.langmuir.5c06452
Zhenghao Shi,Man Hin Kwok,Yifeng Sheng,To Ngai
Metal–organic frameworks (MOFs) offer high porosity and tunable chemistry, while practical applications are often hindered by their poor processability, low packing density, and inadequate mechanical stability when used in powder form. Shaping MOFs into monoliths could dramatically solve these limitations. However, traditional methods such as sol–gel synthesis, freeze-drying, casting, or templating often involve multiple steps or organic solvents, leading to structural collapse and loss of intrinsic porosity. To overcome the aforementioned challenges, herein we report a green, one-step strategy for fabricating hierarchically porous MOF monoliths via Pickering foam templating. By using hexanoic acid (HA) to in situ modulate the surface of CuO nanoparticles (NPs), ultrastable aqueous foams could be directly prepared while subsequently serving as templates for in situ MOF conversion and growth at the air–water interface. In this work, two typical MOF monoliths based on CuBDC and HKUST-1 were synthesized by this method without the use of surfactants, polymers, or harmful solvents. Besides, backbone materials, such as bacterial cellulose (BC), could subsequently be introduced as a reinforcing scaffold to improve mechanical integrity. Structural analyses revealed that the resulting CuBDC monoliths exhibited well-defined hollow spherical shells templated from the foam bubbles, and the incorporation of BC significantly enhanced compressive strength while preserving hierarchical porosity, although the excessive BC slightly caused pore collapse and surface area reduction. The monoliths showed great potential for CO2 adsorption achieving the highest uptake of 2.42 × 10–1 mmol g–1 at 298 K. This study presents the first demonstration of using Pickering wet foam as a direct template for MOF monoliths, offering a sustainable and tunable approach for scalable fabrication of porous materials suitable for gas storage, separation, and adsorption applications.
{"title":"Sustainable CO2 Capture Using Porous CuBDC Monoliths via Pickering Foam Templating Reinforced with Bacterial Cellulose","authors":"Zhenghao Shi,Man Hin Kwok,Yifeng Sheng,To Ngai","doi":"10.1021/acs.langmuir.5c06452","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c06452","url":null,"abstract":"Metal–organic frameworks (MOFs) offer high porosity and tunable chemistry, while practical applications are often hindered by their poor processability, low packing density, and inadequate mechanical stability when used in powder form. Shaping MOFs into monoliths could dramatically solve these limitations. However, traditional methods such as sol–gel synthesis, freeze-drying, casting, or templating often involve multiple steps or organic solvents, leading to structural collapse and loss of intrinsic porosity. To overcome the aforementioned challenges, herein we report a green, one-step strategy for fabricating hierarchically porous MOF monoliths via Pickering foam templating. By using hexanoic acid (HA) to in situ modulate the surface of CuO nanoparticles (NPs), ultrastable aqueous foams could be directly prepared while subsequently serving as templates for in situ MOF conversion and growth at the air–water interface. In this work, two typical MOF monoliths based on CuBDC and HKUST-1 were synthesized by this method without the use of surfactants, polymers, or harmful solvents. Besides, backbone materials, such as bacterial cellulose (BC), could subsequently be introduced as a reinforcing scaffold to improve mechanical integrity. Structural analyses revealed that the resulting CuBDC monoliths exhibited well-defined hollow spherical shells templated from the foam bubbles, and the incorporation of BC significantly enhanced compressive strength while preserving hierarchical porosity, although the excessive BC slightly caused pore collapse and surface area reduction. The monoliths showed great potential for CO2 adsorption achieving the highest uptake of 2.42 × 10–1 mmol g–1 at 298 K. This study presents the first demonstration of using Pickering wet foam as a direct template for MOF monoliths, offering a sustainable and tunable approach for scalable fabrication of porous materials suitable for gas storage, separation, and adsorption applications.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"51 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the relationship between interfacial molecular structures and their frictional properties is one of the key issues in analyzing boundary lubrication mechanisms. In this study, the interfacial structure and frictional behavior of stearic acid (SA) solution were investigated using frequency-modulation atomic force microscopy (FM-AFM) and lateral force microscopy (LFM). FM-AFM visualized two distinct repulsive regions on steel and self-assembled monolayer substrates corresponding to vertically adsorbed SA molecules and a solvation layer of n-hexadecane (HD) molecules oriented parallel to the surface. Interaction force analysis revealed that the upper solvation layer was disrupted under approximately 15.6 pN loading. LFM measurements demonstrated a transition in the friction coefficient near 123 pN, indicating a load-dependent change in the interfacial configuration. A comparison of FM-AFM and LFM contact pressures using the Derjaguin–Muller–Toporov model showed that variations in Young’s modulus and Poisson’s ratio had a negligible effect on the estimated contact pressure, confirming the consistency of breakthrough pressure between the two measurement methods. These findings suggest that the low-friction regime under light pressure originates from the parallel alignment of HD molecules on the vertically oriented SA film.
{"title":"Friction Mechanism on Steel Surface in n-Hexadecane Containing Stearic Acid Based on Cross-Sectional Observation Using Frequency-Modulation Atomic Force Microscopy","authors":"Kaisei Sato,Yuko Sato,Seiya Watanabe,Shinya Sasaki","doi":"10.1021/acs.langmuir.5c05564","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c05564","url":null,"abstract":"Understanding the relationship between interfacial molecular structures and their frictional properties is one of the key issues in analyzing boundary lubrication mechanisms. In this study, the interfacial structure and frictional behavior of stearic acid (SA) solution were investigated using frequency-modulation atomic force microscopy (FM-AFM) and lateral force microscopy (LFM). FM-AFM visualized two distinct repulsive regions on steel and self-assembled monolayer substrates corresponding to vertically adsorbed SA molecules and a solvation layer of n-hexadecane (HD) molecules oriented parallel to the surface. Interaction force analysis revealed that the upper solvation layer was disrupted under approximately 15.6 pN loading. LFM measurements demonstrated a transition in the friction coefficient near 123 pN, indicating a load-dependent change in the interfacial configuration. A comparison of FM-AFM and LFM contact pressures using the Derjaguin–Muller–Toporov model showed that variations in Young’s modulus and Poisson’s ratio had a negligible effect on the estimated contact pressure, confirming the consistency of breakthrough pressure between the two measurement methods. These findings suggest that the low-friction regime under light pressure originates from the parallel alignment of HD molecules on the vertically oriented SA film.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"57 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By creating tailor-made binding sites, molecularly imprinted polymers (MIPs) function as synthetic antibodies, offering comparable specificity with enhanced stability and lower cost. While molecular imprinting technology has achieved significant success with small molecules, its application to macromolecules such as proteins remains challenging. This is primarily due to the common use of aqueous solutions for protein imprinting, where key interactions like hydrogen bonding and electrostatic forces are significantly weakened. To address these limitations, this study reports the rational design of a Cu(II)-coordinated MIPs nanocavity for the efficient and selective adsorption of bovine serum albumin (BSA). The approach leverages the chelation between histidine residues on the surface of BSA and Cu(II), in conjunction with the primary monomer N-isopropylacrylamide (NIPAM) and various functional monomers, including acrylamide (AAM), dimethylaminoethyl methacrylate (DMAEMA), 4-vinylpyridine (4-Vpy), and methacrylic acid (MAA), to construct a shape memory characteristic imprinted nanocavity. Notably, polyglutamic acid peptide cross-linkers (PC) were employed in place of conventional cross-linkers, through a pH-induced helical-coil conformational change, they allow for the gentle yet complete extraction of the BSA template. Experimental results demonstrated that the incorporation of Cu(II) improved the imprinting effect, with the Cu(II)-containing hydrogel achieving an adsorption capacity of 757.5 mg/g and an imprinting factor (IF) of 5.28. Mechanistic analysis revealed that the coordination of Cu(II) synergistically combines the strength of covalent bonds with the flexibility of noncovalent interactions, while the dynamic structure of the PC enhances the specificity of the imprinted sites. Separation experiments conducted with actual serum samples validated the high selectivity of this material for BSA. This research introduces a strategy for protein molecular imprinting technology that integrates high adsorption performance with mild desorption conditions, suggesting significant potential applications in the fields of biomedicine and blood analysis.
{"title":"Rational Engineering of Copper Ion-Coordinated Molecularly Imprinted Polymers for Synergistic Enhancement of Protein Recognition and Separation","authors":"Yanbing Song,Zhuo Zhao,Yuxuan Wang,Ran Cheng,Yafei Wang,Yan Zhang,Ying Guan,Yongjun Zhang","doi":"10.1021/acs.langmuir.5c05246","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c05246","url":null,"abstract":"By creating tailor-made binding sites, molecularly imprinted polymers (MIPs) function as synthetic antibodies, offering comparable specificity with enhanced stability and lower cost. While molecular imprinting technology has achieved significant success with small molecules, its application to macromolecules such as proteins remains challenging. This is primarily due to the common use of aqueous solutions for protein imprinting, where key interactions like hydrogen bonding and electrostatic forces are significantly weakened. To address these limitations, this study reports the rational design of a Cu(II)-coordinated MIPs nanocavity for the efficient and selective adsorption of bovine serum albumin (BSA). The approach leverages the chelation between histidine residues on the surface of BSA and Cu(II), in conjunction with the primary monomer N-isopropylacrylamide (NIPAM) and various functional monomers, including acrylamide (AAM), dimethylaminoethyl methacrylate (DMAEMA), 4-vinylpyridine (4-Vpy), and methacrylic acid (MAA), to construct a shape memory characteristic imprinted nanocavity. Notably, polyglutamic acid peptide cross-linkers (PC) were employed in place of conventional cross-linkers, through a pH-induced helical-coil conformational change, they allow for the gentle yet complete extraction of the BSA template. Experimental results demonstrated that the incorporation of Cu(II) improved the imprinting effect, with the Cu(II)-containing hydrogel achieving an adsorption capacity of 757.5 mg/g and an imprinting factor (IF) of 5.28. Mechanistic analysis revealed that the coordination of Cu(II) synergistically combines the strength of covalent bonds with the flexibility of noncovalent interactions, while the dynamic structure of the PC enhances the specificity of the imprinted sites. Separation experiments conducted with actual serum samples validated the high selectivity of this material for BSA. This research introduces a strategy for protein molecular imprinting technology that integrates high adsorption performance with mild desorption conditions, suggesting significant potential applications in the fields of biomedicine and blood analysis.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"15 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-09DOI: 10.1021/acs.langmuir.5c05600
Xinlei Zhang,Cunjia Pan,Bakhtiyor A. Rasulov,Bei Zhang
Large-pore borophene, a novel two-dimensional (2D) material with exceptional electrical properties and unique electronic structure, shows thermal and electrical potential in nanoribbon configurations due to quantum confinement effects. Surface adsorption is an effective strategy to tune the physicochemical properties of low-dimensional materials due to enhanced electron/phonon scattering effects. In this work, thermal/electric transport behavior of large-pore borophene nanoribbons (LH_ψ) with surface-adsorbed DBHD molecules was systematically investigated by using density functional theory (DFT) combined with nonequilibrium Green’s function (NEGF) method. Asymmetric single-sided adsorption significantly suppresses thermal conductance by enhancing the out-of-plane phonon scattering behavior. Symmetric double-sided π–π stacking plays a dual role: a significant decrease in charge transfer reduces the electrical conductance of LH_ψ/(DBHD)2 system; double-sided π–π stacking boosts thermal conductance by suppressing out-of-plane vibrations simultaneously to enhance the phonon coherent transport behavior. This work provides a theoretical basis to expand large-pore borophene nanoribbons for the application of thermal and electric properties and functional electronic devices.
{"title":"Regulation of the Thermal and Electrical Transport Properties of Large-Pore Borophene Nanoribbons Based on Molecular Surface Adsorption Engineering","authors":"Xinlei Zhang,Cunjia Pan,Bakhtiyor A. Rasulov,Bei Zhang","doi":"10.1021/acs.langmuir.5c05600","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c05600","url":null,"abstract":"Large-pore borophene, a novel two-dimensional (2D) material with exceptional electrical properties and unique electronic structure, shows thermal and electrical potential in nanoribbon configurations due to quantum confinement effects. Surface adsorption is an effective strategy to tune the physicochemical properties of low-dimensional materials due to enhanced electron/phonon scattering effects. In this work, thermal/electric transport behavior of large-pore borophene nanoribbons (LH_ψ) with surface-adsorbed DBHD molecules was systematically investigated by using density functional theory (DFT) combined with nonequilibrium Green’s function (NEGF) method. Asymmetric single-sided adsorption significantly suppresses thermal conductance by enhancing the out-of-plane phonon scattering behavior. Symmetric double-sided π–π stacking plays a dual role: a significant decrease in charge transfer reduces the electrical conductance of LH_ψ/(DBHD)2 system; double-sided π–π stacking boosts thermal conductance by suppressing out-of-plane vibrations simultaneously to enhance the phonon coherent transport behavior. This work provides a theoretical basis to expand large-pore borophene nanoribbons for the application of thermal and electric properties and functional electronic devices.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"45 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study focuses on developing novel materials based on lysozyme, a protein derived from egg white, modified with aluminum hydroxide nanoparticles (γ-Al(OH)3 and α-Al(OH)3) via an adsorption technique to enhance oxytetracycline antibiotic (OTC) removal from water systems. The optimal parameters for lysozyme adsorption on both phases of Al(OH)3 were determined to be a pH of 10, a contact time of 120 min, an Al(OH)3 dosage of 10 mg/mL, and an ionic strength of 1 mM KCl. For OTC removal using lysozyme-modified γ-Al(OH)3 (LGH) and α-Al(OH)3 (LAH), the optimum conditions were identified as a pH of 6, an adsorbent dosage of 10 mg/mL, and a contact time of 90 min. The adsorption kinetics of OTC on both materials adhered to the pseudo-second-order model, while the Freundlich model provided the best fit for the adsorption isotherms. The LGH demonstrated a higher OTC adsorption capacity of 62.9 mg/g compared to LAH with 45.7 mg/g. The adsorption mechanism for OTC on LGH was primarily driven by nonelectrostatic interactions, whereas electrostatic forces predominantly governed OTC adsorption on LAH. Even after four regeneration cycles, the OTC removal efficiencies remained above 70.5% for LGH and 87.9% for LAH. These findings highlight that both lysozyme-modified aluminum hydroxides are environmentally friendly and highly effective materials for removing OTC from aquatic environments.
{"title":"Hybrid Materials Based on Protein-Modified Nano-Aluminum Hydroxide for Efficient Oxytetracycline Removal: Mechanism Insights","authors":"Thi-Tra-My Tran,Phuong-Thao Nguyen,Thi-Diu Dinh,Thanh-Son Le,Thanh-Binh Nguyen,Tien-Duc Pham","doi":"10.1021/acs.langmuir.5c04604","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c04604","url":null,"abstract":"This study focuses on developing novel materials based on lysozyme, a protein derived from egg white, modified with aluminum hydroxide nanoparticles (γ-Al(OH)3 and α-Al(OH)3) via an adsorption technique to enhance oxytetracycline antibiotic (OTC) removal from water systems. The optimal parameters for lysozyme adsorption on both phases of Al(OH)3 were determined to be a pH of 10, a contact time of 120 min, an Al(OH)3 dosage of 10 mg/mL, and an ionic strength of 1 mM KCl. For OTC removal using lysozyme-modified γ-Al(OH)3 (LGH) and α-Al(OH)3 (LAH), the optimum conditions were identified as a pH of 6, an adsorbent dosage of 10 mg/mL, and a contact time of 90 min. The adsorption kinetics of OTC on both materials adhered to the pseudo-second-order model, while the Freundlich model provided the best fit for the adsorption isotherms. The LGH demonstrated a higher OTC adsorption capacity of 62.9 mg/g compared to LAH with 45.7 mg/g. The adsorption mechanism for OTC on LGH was primarily driven by nonelectrostatic interactions, whereas electrostatic forces predominantly governed OTC adsorption on LAH. Even after four regeneration cycles, the OTC removal efficiencies remained above 70.5% for LGH and 87.9% for LAH. These findings highlight that both lysozyme-modified aluminum hydroxides are environmentally friendly and highly effective materials for removing OTC from aquatic environments.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"1 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138795","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-09DOI: 10.1021/acs.langmuir.5c06370
Jie-Yao Song,Ge Dong,Jun-Ru Tian,Jia Li,Wen-Yi Zhou,Shan-Shan Li,Zhongchang Wang
Designing efficient catalysts for the electrocatalytic coreduction of CO2 and N2 into urea remains challenging due to the sluggish activation of both molecules and the complex C–N coupling process. Herein, we report an iron-based metal–organic framework (Fe-MOF) system in which the ratio of Fe2+/Fe3+ active sites is modulated via solvent regulation to promote synergistic catalysis. Structural and spectroscopic analyses confirm that Fe-MOF-1, prepared in ethanol, possesses a higher Fe2+/Fe3+ ratio (0.91) than Fe-MOF-2 (0.56), leading to enhanced electronic conductivity and charge-transfer efficiency. Fe-MOF-1 exhibits a urea yield rate of 3.02 mmol h–1 g–1 with a Faradaic efficiency of 10.4% at −0.71 V (vs RHE), outperforming Fe-MOF-2. In situ FT-IR analysis reveals the generation of *COOH, *NH2, and C–N intermediates, confirming the occurrence of C–N coupling on Fe-MOF-1. The cooperative function of Fe2+ and Fe3+ centers facilitates simultaneous CO2 reduction and N2 activation, enabling efficient urea synthesis under mild conditions. This work provides mechanistic insights and a rational design strategy for dual-valence metal sites toward sustainable C–N coupling catalysis.
{"title":"Fe2+/Fe3+ Redox Modulation in Iron-Based Metal–Organic Frameworks for Efficient C–N Coupling in Electrocatalytic Urea Synthesis","authors":"Jie-Yao Song,Ge Dong,Jun-Ru Tian,Jia Li,Wen-Yi Zhou,Shan-Shan Li,Zhongchang Wang","doi":"10.1021/acs.langmuir.5c06370","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c06370","url":null,"abstract":"Designing efficient catalysts for the electrocatalytic coreduction of CO2 and N2 into urea remains challenging due to the sluggish activation of both molecules and the complex C–N coupling process. Herein, we report an iron-based metal–organic framework (Fe-MOF) system in which the ratio of Fe2+/Fe3+ active sites is modulated via solvent regulation to promote synergistic catalysis. Structural and spectroscopic analyses confirm that Fe-MOF-1, prepared in ethanol, possesses a higher Fe2+/Fe3+ ratio (0.91) than Fe-MOF-2 (0.56), leading to enhanced electronic conductivity and charge-transfer efficiency. Fe-MOF-1 exhibits a urea yield rate of 3.02 mmol h–1 g–1 with a Faradaic efficiency of 10.4% at −0.71 V (vs RHE), outperforming Fe-MOF-2. In situ FT-IR analysis reveals the generation of *COOH, *NH2, and C–N intermediates, confirming the occurrence of C–N coupling on Fe-MOF-1. The cooperative function of Fe2+ and Fe3+ centers facilitates simultaneous CO2 reduction and N2 activation, enabling efficient urea synthesis under mild conditions. This work provides mechanistic insights and a rational design strategy for dual-valence metal sites toward sustainable C–N coupling catalysis.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"59 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138797","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-09DOI: 10.1021/acs.langmuir.5c05155
Seishi Shimizu, Nobuyuki Matubayasi
Given a surface tension isotherm (i.e., how interfacial free energy changes with the surfactant concentration), can we gain insight into how surfactant molecules interact at the interface and in the bulk solution? Historically, surfactants were modeled to bind onto a uniform interface, before aggregating stoichiometrically at the critical micelle concentration (CMC). However, this simple model contrasts with counterevidence, e.g., premicelles (smaller aggregates below CMC) and aggregate size distribution, necessitating a departure from stoichiometric aggregation models. To this end, a novel theory for surface tension will be established by synthesizing the statistical thermodynamic fluctuation theory for sorption and self-assembly in solution. This theory provides a link between the functional shape of a surface tension isotherm and the underlying interactions. We demonstrate that the gradient and curvature of a surface tension isotherm reveal a competition between surfactant sorption and bulk number fluctuation without employing any model assumptions. This novel theory proposes to (i) redefine the surfactant aggregation number using number fluctuations to replace the stoichiometric model, (ii) generalize the Szyszkowski–Langmuir isotherm (which implicitly assumes site-specific adsorption on uniformly distributed binding sites) with the novel ABC isotherm to capture the surface–bulk difference of surfactant number correlation, and (iii) replace the surfactant “area-per-molecule” with the projected area, by incorporating the thickness of the interface. This theory can be applied to surfactants and small molecules (e.g., alcohols) alike, eliminating the need for separate models over a spectrum of self-association propensities.
{"title":"Surface Tension Isotherms: Reconceptualizing Adsorption, Self-Assembly, and Micelle Formation via the Fluctuation Theory","authors":"Seishi Shimizu, Nobuyuki Matubayasi","doi":"10.1021/acs.langmuir.5c05155","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c05155","url":null,"abstract":"Given a surface tension isotherm (i.e., how interfacial free energy changes with the surfactant concentration), can we gain insight into how surfactant molecules interact at the interface and in the bulk solution? Historically, surfactants were modeled to bind onto a uniform interface, before aggregating stoichiometrically at the critical micelle concentration (CMC). However, this simple model contrasts with counterevidence, e.g., premicelles (smaller aggregates below CMC) and aggregate size distribution, necessitating a departure from stoichiometric aggregation models. To this end, a novel theory for surface tension will be established by synthesizing the statistical thermodynamic fluctuation theory for sorption and self-assembly in solution. This theory provides a link between the functional shape of a surface tension isotherm and the underlying interactions. We demonstrate that the gradient and curvature of a surface tension isotherm reveal a competition between surfactant sorption and bulk number fluctuation without employing any model assumptions. This novel theory proposes to (i) redefine the surfactant aggregation number using number fluctuations to replace the stoichiometric model, (ii) generalize the Szyszkowski–Langmuir isotherm (which implicitly assumes site-specific adsorption on uniformly distributed binding sites) with the novel ABC isotherm to capture the surface–bulk difference of surfactant number correlation, and (iii) replace the surfactant “area-per-molecule” with the projected area, by incorporating the thickness of the interface. This theory can be applied to surfactants and small molecules (e.g., alcohols) alike, eliminating the need for separate models over a spectrum of self-association propensities.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"161 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Conventional photocatalysts suffer from rapid electron–hole recombination, severely limiting their practical application in wastewater treatment. Moreover, many organic degradation systems require the addition of hydrogen peroxide or persulfate to enhance photocatalytic activity, but this not only often leads to secondary pollution but also results in low oxidant utilization efficiency. To overcome this fundamental constraint, a novel direct Fe-based Metal–Organic Frameworks (Fe-MOF)/BiOBr heterojunction was innovatively constructed via hydrothermal synthesis. Without the need for additional oxidizing agents, this catalyst relies solely on light energy to initiate and maintain the photocatalytic degradation reaction. The optimized MIL-101/BiOBr composite demonstrated outstanding performance, achieving over 99% degradation of Rhodamine B (RhB) within 60 min under UV light, retaining an 88% degradation rate at an ultrahigh dye concentration (80 mg/L), and maintaining exceptional cycling stability (89.57% after 5 cycles). Mechanistically, ESR/trapping experiments identified h+ and ·O2– as the dominant species, while comprehensive characterization (SEM, XRD, XPS, BET) and photoelectrochemical analyses confirmed the successful preparation of the heterojunction. Furthermore, density functional theory (DFT) calculations combined with the analysis of degradation intermediates allowed the prediction of the Rhodamine B degradation pathway from both theoretical and experimental perspectives. The catalyst also exhibited versatile degradation capability, efficiently removing methylene blue (73.1–97.7%) and tetracycline with accelerated kinetics. Overall, the Fe-MOF/BiOBr synthesized in this study represents a photocatalytic material with significant practical potential for wastewater degradation thanks to its innovative advantages such as light-driven operation, high electron–hole separation efficiency, stable performance, broad organic degradation capability, and well-elucidated degradation pathways.
{"title":"Synthesis, Mechanism Analysis, and Degradation Pathways of Fe-Based Metal–Organic Frameworks/BiOBr Heterojunctions for Effective Photocatalytic Organic Pollutant Degradation","authors":"Yifeng Wang,Xinpeng Chen,Ziwei Wu,Guoqiang Chen,Tieling Xing","doi":"10.1021/acs.langmuir.5c03800","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c03800","url":null,"abstract":"Conventional photocatalysts suffer from rapid electron–hole recombination, severely limiting their practical application in wastewater treatment. Moreover, many organic degradation systems require the addition of hydrogen peroxide or persulfate to enhance photocatalytic activity, but this not only often leads to secondary pollution but also results in low oxidant utilization efficiency. To overcome this fundamental constraint, a novel direct Fe-based Metal–Organic Frameworks (Fe-MOF)/BiOBr heterojunction was innovatively constructed via hydrothermal synthesis. Without the need for additional oxidizing agents, this catalyst relies solely on light energy to initiate and maintain the photocatalytic degradation reaction. The optimized MIL-101/BiOBr composite demonstrated outstanding performance, achieving over 99% degradation of Rhodamine B (RhB) within 60 min under UV light, retaining an 88% degradation rate at an ultrahigh dye concentration (80 mg/L), and maintaining exceptional cycling stability (89.57% after 5 cycles). Mechanistically, ESR/trapping experiments identified h+ and ·O2– as the dominant species, while comprehensive characterization (SEM, XRD, XPS, BET) and photoelectrochemical analyses confirmed the successful preparation of the heterojunction. Furthermore, density functional theory (DFT) calculations combined with the analysis of degradation intermediates allowed the prediction of the Rhodamine B degradation pathway from both theoretical and experimental perspectives. The catalyst also exhibited versatile degradation capability, efficiently removing methylene blue (73.1–97.7%) and tetracycline with accelerated kinetics. Overall, the Fe-MOF/BiOBr synthesized in this study represents a photocatalytic material with significant practical potential for wastewater degradation thanks to its innovative advantages such as light-driven operation, high electron–hole separation efficiency, stable performance, broad organic degradation capability, and well-elucidated degradation pathways.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"35 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-08DOI: 10.1021/acs.langmuir.5c04491
Martijn H. P. de Heer Kloots, Hanne M. van der Kooij, Christof van Sluijs, Gerald A. Metselaar, Anthonie Stuiver, Wiebe M. de Vos, Jasper van der Gucht
Polyelectrolytes can be used to make water-based, recyclable, and robust coatings, making use of their strong electrostatic interactions. They are conventionally applied in a layer-by-layer fashion, which is labor-intensive and thus expensive. Recently, polyelectrolyte complexes have also been applied in a single step, where both polycation and polyanion are simultaneously applied to the surface. To avoid complexation before application, a volatile base was added to deprotonate amines on the polycation. Only after evaporation of the base, charges are introduced on the polycation, initiating complexation. However, the associative phase separation in these polyelectrolyte coatings is poorly understood. Here, we study the associative phase separation in poly(ethylene imine):poly(acrylic acid) coatings using confocal fluorescence microscopy. We find that the initial polyelectrolyte concentration has a profound impact on the macroscale homogeneity during and after drying. Using fluorescently labeled polyelectrolytes, we show that during coating drying, a continuous polyelectrolyte complex matrix forms, with polyelectrolyte-poor inclusions. We explain these observations by connecting the changes in composition in the coating film to the underlying phase diagram of the polyelectrolyte mixture. We anticipate that the increased understanding of the associative phase separation described in this study will significantly aid the development of homogeneous functional polyelectrolyte coatings.
{"title":"Associative Phase Separation in Single-Step Polyelectrolyte Complex Coatings","authors":"Martijn H. P. de Heer Kloots, Hanne M. van der Kooij, Christof van Sluijs, Gerald A. Metselaar, Anthonie Stuiver, Wiebe M. de Vos, Jasper van der Gucht","doi":"10.1021/acs.langmuir.5c04491","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c04491","url":null,"abstract":"Polyelectrolytes can be used to make water-based, recyclable, and robust coatings, making use of their strong electrostatic interactions. They are conventionally applied in a layer-by-layer fashion, which is labor-intensive and thus expensive. Recently, polyelectrolyte complexes have also been applied in a single step, where both polycation and polyanion are simultaneously applied to the surface. To avoid complexation before application, a volatile base was added to deprotonate amines on the polycation. Only after evaporation of the base, charges are introduced on the polycation, initiating complexation. However, the associative phase separation in these polyelectrolyte coatings is poorly understood. Here, we study the associative phase separation in poly(ethylene imine):poly(acrylic acid) coatings using confocal fluorescence microscopy. We find that the initial polyelectrolyte concentration has a profound impact on the macroscale homogeneity during and after drying. Using fluorescently labeled polyelectrolytes, we show that during coating drying, a continuous polyelectrolyte complex matrix forms, with polyelectrolyte-poor inclusions. We explain these observations by connecting the changes in composition in the coating film to the underlying phase diagram of the polyelectrolyte mixture. We anticipate that the increased understanding of the associative phase separation described in this study will significantly aid the development of homogeneous functional polyelectrolyte coatings.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"73 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-08DOI: 10.1021/acs.langmuir.5c06106
Bignya Rani Dash,Ramesh L. Gardas,Ashok Kumar Mishra
We report the synthesis of a novel long-chain protic ionic liquid (PIL), 1,5-diazabicyclo[4.3.0]non-5-ene laurate ([DBNH][H23C11COO]), that undergoes remarkable transformation into a stable ionogel upon controlled water addition. To the best of our knowledge, this is the first demonstration that a PIL forms lyotropic liquid-crystalline mesophases exhibiting birefringence. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) reveal smectic-like phases with temperature-driven structural transitions. The ionogel exhibits clustering triggered emission (CTE) and excitation-dependent luminescence behavior. The microheterogeneity of the gel was probed using Nile red (NR). The steady-state emission spectrum of NR shows a transition from bimodal to unimodal near 80 °C, indicating a temperature-driven gel to sol transition. Wavelength-dependent fluorescence lifetimes of NR reveal slow solvation dynamics, with the rise time observed at longer emission wavelengths, 660 nm, providing a sensitive means to monitor the microheterogeneity of the gel medium. In addition, the material’s optical textures can be tunable upon the addition of aqueous inorganic salts, demonstrating its stimuli-responsive nature. Rheological measurements show clear ion-specific effects on the mechanical properties of the ionogels. The neat ionogel shows an elastic response, while the NaCl-containing ionogel exhibits the highest gel strength. In contrast, ionogels containing KCl, CsCl, and RbCl show weaker gel networks and more viscous behavior, indicating the soft nature of these gels. These findings introduce a new class of thermoresponsive, PIL-based lyotropic ionogels and demonstrate an anion-centered strategy for the first time that could be relevant for soft-matter applications.
{"title":"Water-Mediated Liquid Crystalline Ionogel Formation in a Long-Chain Protic Ionic Liquid: An Anion-Centered Design Strategy","authors":"Bignya Rani Dash,Ramesh L. Gardas,Ashok Kumar Mishra","doi":"10.1021/acs.langmuir.5c06106","DOIUrl":"https://doi.org/10.1021/acs.langmuir.5c06106","url":null,"abstract":"We report the synthesis of a novel long-chain protic ionic liquid (PIL), 1,5-diazabicyclo[4.3.0]non-5-ene laurate ([DBNH][H23C11COO]), that undergoes remarkable transformation into a stable ionogel upon controlled water addition. To the best of our knowledge, this is the first demonstration that a PIL forms lyotropic liquid-crystalline mesophases exhibiting birefringence. Polarized optical microscopy (POM) and differential scanning calorimetry (DSC) reveal smectic-like phases with temperature-driven structural transitions. The ionogel exhibits clustering triggered emission (CTE) and excitation-dependent luminescence behavior. The microheterogeneity of the gel was probed using Nile red (NR). The steady-state emission spectrum of NR shows a transition from bimodal to unimodal near 80 °C, indicating a temperature-driven gel to sol transition. Wavelength-dependent fluorescence lifetimes of NR reveal slow solvation dynamics, with the rise time observed at longer emission wavelengths, 660 nm, providing a sensitive means to monitor the microheterogeneity of the gel medium. In addition, the material’s optical textures can be tunable upon the addition of aqueous inorganic salts, demonstrating its stimuli-responsive nature. Rheological measurements show clear ion-specific effects on the mechanical properties of the ionogels. The neat ionogel shows an elastic response, while the NaCl-containing ionogel exhibits the highest gel strength. In contrast, ionogels containing KCl, CsCl, and RbCl show weaker gel networks and more viscous behavior, indicating the soft nature of these gels. These findings introduce a new class of thermoresponsive, PIL-based lyotropic ionogels and demonstrate an anion-centered strategy for the first time that could be relevant for soft-matter applications.","PeriodicalId":50,"journal":{"name":"Langmuir","volume":"83 1","pages":""},"PeriodicalIF":3.9,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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