Shilpa SharmaL2C, Julian OberdisseL2C, Johan AlauzunICGM ICMMM, Philippe Dieudonné-George, Thomas Bizien, Cansu Akkaya, Peter Hesemann, Anne-Caroline Genix
Mesoporous systems are ubiquitous in membrane science and applications due to their high internal surface area and tunable pore size. A new synthesis pathway of hydrolytic ionosilica films with mesopores formed by ionic liquid (IL) templating is proposed and compared to the traditional non-hydrolytic strategy. For both pathways, the multi-scale formation of pores has been studied as a function of IL content, combining results of thermogravimetric analysis (TGA), nitrogen sorption, and small-angle X-ray scattering (SAXS). The combination of TGA and nitrogen sorption provides access to ionosilica and pore volume fractions, with contributions of meso- and macropores. We then elaborate an original and quantitative geometrical model to analyze the SAXS data based on small spheres (Rs = 1 -- 2 nm) and cylinders (Lcyl = 10 -- 20 nm) with radial polydispersity provided by the nitrogen sorption isotherms. As a main result, we found that for a given incorporation of templating IL, both synthesis pathways produce very similar pore geometries, but the better incorporation efficacy of the new hydrolytic films provides a higher mesoporosity. Our combined study provides a coherent view of mesopore geometry, and thereby an optimization pathway of porous ionic membranes in terms of accessible mesoporosity contributing to the specific surface. Possible applications include electrolyte membranes of improved ionic properties, e.g., in fuel cells and batteries, as well as molecular storage.
由于具有高内表面积和可调孔径，介孔系统在膜科学和应用中无处不在。结合热重分析 (TGA)、氮吸附和小角 X 射线散射 (SAXS) 的结果，研究了这两种途径中孔隙的多尺度形成与 IL 含量的函数关系。结合热重分析和氮吸附，可以获得离子硅和孔隙体积分数，以及中孔和大孔的贡献。然后，我们根据氮吸附等温线提供的具有径向多分散性的小球体（Rs = 1 - 2 nm）和圆柱体（Lcyl = 10 - 20 nm），建立了一个原创的定量几何模型来分析 SAXS 数据。我们发现，对于给定的模板惰性离子的掺入量，两种合成途径产生的孔隙几何形状非常相似，但新型水解膜的掺入效率更高，中孔率也更高。我们的综合研究为中孔几何提供了一个连贯的视角，从而为多孔离子膜的优化途径提供了一个有助于比表面的可获得中孔率。可能的应用包括改善离子特性的电解质膜，如燃料电池和电池，以及分子存储。
{"title":"Controlled formation of multi-scale porosity in ionosilica templated by ionic liquid","authors":"Shilpa SharmaL2C, Julian OberdisseL2C, Johan AlauzunICGM ICMMM, Philippe Dieudonné-George, Thomas Bizien, Cansu Akkaya, Peter Hesemann, Anne-Caroline Genix","doi":"arxiv-2409.04051","DOIUrl":"https://doi.org/arxiv-2409.04051","url":null,"abstract":"Mesoporous systems are ubiquitous in membrane science and applications due to\u0000their high internal surface area and tunable pore size. A new synthesis pathway\u0000of hydrolytic ionosilica films with mesopores formed by ionic liquid (IL)\u0000templating is proposed and compared to the traditional non-hydrolytic strategy.\u0000For both pathways, the multi-scale formation of pores has been studied as a\u0000function of IL content, combining results of thermogravimetric analysis (TGA),\u0000nitrogen sorption, and small-angle X-ray scattering (SAXS). The combination of\u0000TGA and nitrogen sorption provides access to ionosilica and pore volume\u0000fractions, with contributions of meso- and macropores. We then elaborate an\u0000original and quantitative geometrical model to analyze the SAXS data based on\u0000small spheres (Rs = 1 -- 2 nm) and cylinders (Lcyl = 10 -- 20 nm) with radial\u0000polydispersity provided by the nitrogen sorption isotherms. As a main result,\u0000we found that for a given incorporation of templating IL, both synthesis\u0000pathways produce very similar pore geometries, but the better incorporation\u0000efficacy of the new hydrolytic films provides a higher mesoporosity. Our\u0000combined study provides a coherent view of mesopore geometry, and thereby an\u0000optimization pathway of porous ionic membranes in terms of accessible\u0000mesoporosity contributing to the specific surface. Possible applications\u0000include electrolyte membranes of improved ionic properties, e.g., in fuel cells\u0000and batteries, as well as molecular storage.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alice Etienne-Simonetti, Frédéric Restagno, Isabelle Cantat, Emmanuelle Rio
During coating processes, dust deposition can lead to an uneven thickness in the resulting film, posing significant problems in industrial processes. Our study explores the effects of solid defects using a vertical cylindrical fiber deposited on a silicone oil film coating a horizontal solid substrate. We use a hyperspectral camera to measure the film thickness by interferometry in the vicinity of the defect. As predicted and observed in many studies in various geometries, a circular groove appears around the fiber because of the capillary suction induced by the meniscus that grows at the bottom of the fiber. We measure the evolution of the thickness of the film at the groove over time. The thickness decreases before increasing again leading to the healing of the perturbation at long time. We propose that healing is due to the arrest of the suction when the meniscus reaches its equilibrium shape. By combining geometric analysis with the thin film equation, we have developed scaling laws that predict both the minimum thickness of the groove, that we call the time-minimum thickness, and the time required to reach this minimum. If the time-minimum thickness reaches the thickness at which intermolecular forces begin to play a role prior to healing, the thickness of the groove will stop decreasing and saturate due to the competition between drainage and repulsive intermolecular forces. Based on the previous scaling law, we developed a scaling law accounting for the critical initial thickness of the film below which the intermolecular repulsion will start to have an effect, which is in good agreement with our experiments. These results thus offer valuable insights into predicting and preventing defects in coating processes, thereby improving the quality and reliability of coated products in various industries.
{"title":"Hydrodynamic thinning of a coating film induced by a small solid defect: evidence of a time-minimum thickness","authors":"Alice Etienne-Simonetti, Frédéric Restagno, Isabelle Cantat, Emmanuelle Rio","doi":"arxiv-2409.04260","DOIUrl":"https://doi.org/arxiv-2409.04260","url":null,"abstract":"During coating processes, dust deposition can lead to an uneven thickness in\u0000the resulting film, posing significant problems in industrial processes. Our\u0000study explores the effects of solid defects using a vertical cylindrical fiber\u0000deposited on a silicone oil film coating a horizontal solid substrate. We use a\u0000hyperspectral camera to measure the film thickness by interferometry in the\u0000vicinity of the defect. As predicted and observed in many studies in various\u0000geometries, a circular groove appears around the fiber because of the capillary\u0000suction induced by the meniscus that grows at the bottom of the fiber. We\u0000measure the evolution of the thickness of the film at the groove over time. The\u0000thickness decreases before increasing again leading to the healing of the\u0000perturbation at long time. We propose that healing is due to the arrest of the\u0000suction when the meniscus reaches its equilibrium shape. By combining geometric\u0000analysis with the thin film equation, we have developed scaling laws that\u0000predict both the minimum thickness of the groove, that we call the time-minimum\u0000thickness, and the time required to reach this minimum. If the time-minimum\u0000thickness reaches the thickness at which intermolecular forces begin to play a\u0000role prior to healing, the thickness of the groove will stop decreasing and\u0000saturate due to the competition between drainage and repulsive intermolecular\u0000forces. Based on the previous scaling law, we developed a scaling law\u0000accounting for the critical initial thickness of the film below which the\u0000intermolecular repulsion will start to have an effect, which is in good\u0000agreement with our experiments. These results thus offer valuable insights into\u0000predicting and preventing defects in coating processes, thereby improving the\u0000quality and reliability of coated products in various industries.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"65 Suppl 1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We investigate the positional behavior of a single bacterium confined within a vesicle by measuring the probability of locating the bacterium at a certain distance from the vesicle boundary. We observe that the distribution is bi-exponential in nature. Near the boundary, the distribution exhibits rapid exponential decay, transitioning to a slower exponential decay, and eventually becoming uniform further away from the boundary. The length scales associated with the decay are found to depend on the confinement radius. We interpret these observations using molecular simulations and analytical calculations based on the Fokker-Planck equation for an Active Brownian Particle model. Our findings reveal that the small length scale is strongly influenced by the translational diffusion coefficient, while the larger length scale is governed by rotational diffusivity and self-propulsion. These results are explained in terms of two dimensionless parameters that explicitly include the confinement radius. The scaling behavior predicted analytically for the observed length scales is confirmed through simulations.
{"title":"Curvature dependent dynamics of a bacterium confined in a giant unilamellar vesicle","authors":"Olivia Vincent, Aparna Sreekumari, Manoj Gopalakrishnan, Vishwas V Vasisht, Bibhu Ranjan Sarangi","doi":"arxiv-2409.03578","DOIUrl":"https://doi.org/arxiv-2409.03578","url":null,"abstract":"We investigate the positional behavior of a single bacterium confined within\u0000a vesicle by measuring the probability of locating the bacterium at a certain\u0000distance from the vesicle boundary. We observe that the distribution is\u0000bi-exponential in nature. Near the boundary, the distribution exhibits rapid\u0000exponential decay, transitioning to a slower exponential decay, and eventually\u0000becoming uniform further away from the boundary. The length scales associated\u0000with the decay are found to depend on the confinement radius. We interpret\u0000these observations using molecular simulations and analytical calculations\u0000based on the Fokker-Planck equation for an Active Brownian Particle model. Our\u0000findings reveal that the small length scale is strongly influenced by the\u0000translational diffusion coefficient, while the larger length scale is governed\u0000by rotational diffusivity and self-propulsion. These results are explained in\u0000terms of two dimensionless parameters that explicitly include the confinement\u0000radius. The scaling behavior predicted analytically for the observed length\u0000scales is confirmed through simulations.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"111 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thermal conductivity coefficient $kappa$ measures the ability of a material to conduct a heat current. In particular, $kappa$ is an important property that often dictates the usefulness of a material over a wide range of environmental conditions. For example, while a low $kappa$ is desirable for the thermoelectric applications, a large $kappa$ is needed when a material is used under the high temperature conditions. These materials range from common crystals to commodity amorphous polymers. The latter is of particular importance because of their use in designing light weight high performance functional materials. In this context, however, one of the major limitations of the amorphous polymers is their low $kappa$, reaching a maximum value of about 0.4 W/Km that is 2--3 orders of magnitude smaller than the standard crystals. Moreover, when energy is predominantly transferred through the bonded connections, $kappa ge 100$ W/Km. Recently, extensive efforts have been devoted to attain a tunability in $kappa$ via macromolecular engineering. In this work, an overview of the recent results on the $kappa$ behavior in polymers and polymeric solids is presented. In particular, computational and theoretical results are discussed within the context of complimentary experiments. Future directions are also highlighted.
{"title":"Thermal conductivity of polymers: A simple matter where complexity matters","authors":"Debashish Mukherji","doi":"arxiv-2409.03173","DOIUrl":"https://doi.org/arxiv-2409.03173","url":null,"abstract":"Thermal conductivity coefficient $kappa$ measures the ability of a material\u0000to conduct a heat current. In particular, $kappa$ is an important property\u0000that often dictates the usefulness of a material over a wide range of\u0000environmental conditions. For example, while a low $kappa$ is desirable for\u0000the thermoelectric applications, a large $kappa$ is needed when a material is\u0000used under the high temperature conditions. These materials range from common\u0000crystals to commodity amorphous polymers. The latter is of particular\u0000importance because of their use in designing light weight high performance\u0000functional materials. In this context, however, one of the major limitations of\u0000the amorphous polymers is their low $kappa$, reaching a maximum value of about\u00000.4 W/Km that is 2--3 orders of magnitude smaller than the standard crystals.\u0000Moreover, when energy is predominantly transferred through the bonded\u0000connections, $kappa ge 100$ W/Km. Recently, extensive efforts have been\u0000devoted to attain a tunability in $kappa$ via macromolecular engineering. In\u0000this work, an overview of the recent results on the $kappa$ behavior in\u0000polymers and polymeric solids is presented. In particular, computational and\u0000theoretical results are discussed within the context of complimentary\u0000experiments. Future directions are also highlighted.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"143 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, nanofluidics experiments have been used to characterize the behavior of single DNA molecules confined to narrow slits etched with arrays of nanopits. Analysis of the experimental data relies on analytical estimates of the underlying free-energy landscape. In this study we use computer simulations to explicitly calculate the free energy and test the approximations employed in such analytical models. Specifically, Monte Carlo simulations were used to study a polymer confined to complex geometry consisting of a nanoslit with two square nanopits embedded in one of the surfaces. The two-dimensional Weighted Histogram Analysis Method (WHAM2D) is used to calculate the free energy, $F$, as a function of the sum ($lambda_1$) and the difference ($lambda_2$) of the length of the polymer contour contained in the two nanopits. We find the variation of the free-energy function with respect to confinement dimensions to be comparable to the analytical predictions that employ a simplistic theoretical model. However, there are some noteworthy quantitative discrepancies, particularly between the predicted and observed variation of $F$ with respect to $lambda_1$. Our study provides a useful lesson on the limitations of using simplistic analytical expressions for polymer free-energy landscapes to interpret results for experiments of DNA confined to a complex geometry and points to the value of carrying out accurate numerical calculations of the free energy instead.
最近，纳米流体力学实验被用来描述单个 DNA 分子在蚀刻有纳米孔阵列的窄缝中的行为特征。对实验数据的分析依赖于对基本自由能谱的分析估计。在本研究中，我们利用计算机模拟来明确计算自由能，并测试分析模型所采用的近似值。具体来说，蒙特卡罗模拟用于研究一种局限于复杂几何形状的聚合物，该几何形状由一个表面嵌入两个正方形纳米凹坑的纳米发光体组成。使用二维加权组图分析法（WHAM2D）计算自由能 $F$，它是两个纳米孔中包含的聚合物轮廓长度之和（$lambda_1$）和之差（$lambda_2$）的函数。我们发现自由能函数在约束尺寸方面的变化与采用简单理论模型的分析预测相当。然而，存在一些值得注意的定量差异，特别是 $F$ 相对于 $lambda_1$ 的预测变化与观测变化之间的差异。我们的研究提供了一个有益的教训，即使用聚合物自由能景观的简单分析表达式来解释局限于复杂几何形状的 DNA 实验结果是有局限性的，并指出了对自由能进行精确数值计算的价值。
{"title":"Free-energy landscape of a polymer in the presence of two nanofluidic entropic traps","authors":"James M. Polson, Matthew Kozma","doi":"arxiv-2409.03882","DOIUrl":"https://doi.org/arxiv-2409.03882","url":null,"abstract":"Recently, nanofluidics experiments have been used to characterize the\u0000behavior of single DNA molecules confined to narrow slits etched with arrays of\u0000nanopits. Analysis of the experimental data relies on analytical estimates of\u0000the underlying free-energy landscape. In this study we use computer simulations\u0000to explicitly calculate the free energy and test the approximations employed in\u0000such analytical models. Specifically, Monte Carlo simulations were used to\u0000study a polymer confined to complex geometry consisting of a nanoslit with two\u0000square nanopits embedded in one of the surfaces. The two-dimensional Weighted\u0000Histogram Analysis Method (WHAM2D) is used to calculate the free energy, $F$,\u0000as a function of the sum ($lambda_1$) and the difference ($lambda_2$) of the\u0000length of the polymer contour contained in the two nanopits. We find the\u0000variation of the free-energy function with respect to confinement dimensions to\u0000be comparable to the analytical predictions that employ a simplistic\u0000theoretical model. However, there are some noteworthy quantitative\u0000discrepancies, particularly between the predicted and observed variation of $F$\u0000with respect to $lambda_1$. Our study provides a useful lesson on the\u0000limitations of using simplistic analytical expressions for polymer free-energy\u0000landscapes to interpret results for experiments of DNA confined to a complex\u0000geometry and points to the value of carrying out accurate numerical\u0000calculations of the free energy instead.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220630","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jesús Algaba, Iván M. Zerón, José Manuel Míguez, Joanna Grabowska, Samuel Blazquez, Eduardo Sanz, Carlos Vega, Felipe J. Blas
In this paper, the solubility of carbon dioxide (CO$_{2}$) in water along the isobar of 400 bar is determined by computer simulations using the well-known TIP4P/Ice force field for water and TraPPE model for CO$_{2}$. In particular, the solubility of CO$_{2}$ in water when in contact with the CO$_{2}$ liquid phase, and the solubility of CO$_{2}$ in water when in contact with the hydrate have been determined. The solubility of CO$_{2}$ in a liquid-liquid system decreases as temperature increases. The solubility of CO$_{2}$ in a hydrate-liquid system increases with temperature. The two curves intersect at a certain temperature that determines the dissociation temperature of the hydrate at 400 bar ($T_{3}$). We compare the predictions with the $T_{3}$ obtained using the direct coexistence technique in a previous work. The results of both methods agree and we suggest 290(2)K as the value of $T_{3}$ for this system using the same cutoff distance for dispersive interactions. We also propose a novel and alternative route to evaluate the change in chemical potential for the formation of hydrate along the isobar. The new approach is based on the use of the solubility curve of CO$_{2}$ when the aqueous solution is in contact with the hydrate phase. It considers rigorously the non-ideality of the aqueous solution of CO$_{2}$, providing reliable values for driving force for nucleation of hydrates in good agreement with other thermodynamic routes used. It is shown that the driving force for hydrate nucleation at 400 bar is larger for the methane hydrate than for the carbon dioxide hydrate when compared at the same supercooling. We have also analyzed and discussed the effect of the cutoff distance of the dispersive interactions and the occupancy of CO$_{2}$ on the driving force for nucleation of the hydrate.
{"title":"Solubility of carbon dioxide in water: some useful results for hydrate nucleation","authors":"Jesús Algaba, Iván M. Zerón, José Manuel Míguez, Joanna Grabowska, Samuel Blazquez, Eduardo Sanz, Carlos Vega, Felipe J. Blas","doi":"arxiv-2409.02600","DOIUrl":"https://doi.org/arxiv-2409.02600","url":null,"abstract":"In this paper, the solubility of carbon dioxide (CO$_{2}$) in water along the\u0000isobar of 400 bar is determined by computer simulations using the well-known\u0000TIP4P/Ice force field for water and TraPPE model for CO$_{2}$. In particular,\u0000the solubility of CO$_{2}$ in water when in contact with the CO$_{2}$ liquid\u0000phase, and the solubility of CO$_{2}$ in water when in contact with the hydrate\u0000have been determined. The solubility of CO$_{2}$ in a liquid-liquid system\u0000decreases as temperature increases. The solubility of CO$_{2}$ in a\u0000hydrate-liquid system increases with temperature. The two curves intersect at a\u0000certain temperature that determines the dissociation temperature of the hydrate\u0000at 400 bar ($T_{3}$). We compare the predictions with the $T_{3}$ obtained\u0000using the direct coexistence technique in a previous work. The results of both\u0000methods agree and we suggest 290(2)K as the value of $T_{3}$ for this system\u0000using the same cutoff distance for dispersive interactions. We also propose a\u0000novel and alternative route to evaluate the change in chemical potential for\u0000the formation of hydrate along the isobar. The new approach is based on the use\u0000of the solubility curve of CO$_{2}$ when the aqueous solution is in contact\u0000with the hydrate phase. It considers rigorously the non-ideality of the aqueous\u0000solution of CO$_{2}$, providing reliable values for driving force for\u0000nucleation of hydrates in good agreement with other thermodynamic routes used.\u0000It is shown that the driving force for hydrate nucleation at 400 bar is larger\u0000for the methane hydrate than for the carbon dioxide hydrate when compared at\u0000the same supercooling. We have also analyzed and discussed the effect of the\u0000cutoff distance of the dispersive interactions and the occupancy of CO$_{2}$ on\u0000the driving force for nucleation of the hydrate.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Philipp Ritzert, Alexandra Striegel, Regine von Klitzing
Gold nanoparticles (AuNPs) play an important role in fundamental research and development due to their versatile applications and biocompatibility. This study addresses the aging of three AuNP suspensions after the addition of various sodium salts along the well-known Hofmeister series (NaF, NaCl, NaBr, NaI, NaSCN) at different salt concentrations between 10 mM and 100 mM. The AuNP types differ in size (5 nm vs. 11 nm in diameter) and the capping type (physisorbed citrate vs. covalently bound mercaptopropionic acid (MPA)). We monitor the aggregation of the AuNPs and the suspension stability optically (absorption spectroscopy, photography) and by electron microscopy. The large range of salt concentrations results in a large variety of colloidal stability, e.g., from stable suspensions to fast destabilization followed by sedimentation. At intermediate and high salt concentration strong ion-specific effects emerge that are non-monotonous with respect to the Hofmeister series. In particular, the chaotropic salts, NaI and NaSCN, strongly alter the absorption spectra in very different ways. NaI fuses AuNPs together influencing the primary absorption, while NaSCN retains AuNP structure during aggregation much stronger than the remaining sodium halides, resulting in a secondary absorption peak. Although decreasing the size of AuNPs leads to more stable suspensions, the ion specific effects are even more pronounced due to the increase in total available surface. Even the covalently bound MPA capping is not able to stabilize AuNPs against particle fusion by NaI, although it delays the process. Despite the complex interplay between different effects of ions on the stability of colloidal dispersions, this study disentangles the different effects from electrostatic screening, via adsorption at the interface and bridging of AuNPs, to the competition between ions and the capping agent of the AuNPs.
{"title":"Ion-specific Stability of Gold Nanoparticle Suspensions","authors":"Philipp Ritzert, Alexandra Striegel, Regine von Klitzing","doi":"arxiv-2409.02762","DOIUrl":"https://doi.org/arxiv-2409.02762","url":null,"abstract":"Gold nanoparticles (AuNPs) play an important role in fundamental research and\u0000development due to their versatile applications and biocompatibility. This\u0000study addresses the aging of three AuNP suspensions after the addition of\u0000various sodium salts along the well-known Hofmeister series (NaF, NaCl, NaBr,\u0000NaI, NaSCN) at different salt concentrations between 10 mM and 100 mM. The AuNP\u0000types differ in size (5 nm vs. 11 nm in diameter) and the capping type\u0000(physisorbed citrate vs. covalently bound mercaptopropionic acid (MPA)). We\u0000monitor the aggregation of the AuNPs and the suspension stability optically\u0000(absorption spectroscopy, photography) and by electron microscopy. The large\u0000range of salt concentrations results in a large variety of colloidal stability,\u0000e.g., from stable suspensions to fast destabilization followed by\u0000sedimentation. At intermediate and high salt concentration strong ion-specific\u0000effects emerge that are non-monotonous with respect to the Hofmeister series.\u0000In particular, the chaotropic salts, NaI and NaSCN, strongly alter the\u0000absorption spectra in very different ways. NaI fuses AuNPs together influencing\u0000the primary absorption, while NaSCN retains AuNP structure during aggregation\u0000much stronger than the remaining sodium halides, resulting in a secondary\u0000absorption peak. Although decreasing the size of AuNPs leads to more stable\u0000suspensions, the ion specific effects are even more pronounced due to the\u0000increase in total available surface. Even the covalently bound MPA capping is\u0000not able to stabilize AuNPs against particle fusion by NaI, although it delays\u0000the process. Despite the complex interplay between different effects of ions on\u0000the stability of colloidal dispersions, this study disentangles the different\u0000effects from electrostatic screening, via adsorption at the interface and\u0000bridging of AuNPs, to the competition between ions and the capping agent of the\u0000AuNPs.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"69 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Peter Vogel, David Beyer, Christian Holm, Thomas Palberg
We study the influence of airborne CO2 on the charge state of carboxylate stabilized polymer latex particles suspended in aqueous electrolytes. We combine conductometric experiments interpreted in terms of Hessinger's conductivity model with Poisson-Boltzmann cell (PBC) model calculations with charge regulation boundary conditions. Without CO2, a minority of the weakly acidic surface groups are dissociated and only a fraction of the total number of counter-ions actually contribute to conductivity. The remaining counter-ions exchange freely with added other ions like Na+, K+ or Cs+. From the PBC-calculations we infer a corresponding pKa of 4.26 as well as a renormalized charge in reasonably good agreement with the number of freely mobile counter-ions. Equilibration of salt- and CO2-free suspensions against ambient air leads to a drastic de-charging, which exceeds by far the expected effects of to dissolved CO2 and its dissociation products. Further, no counter-ion-exchange is observed. To reproduce the experimental findings, we have to assume an effective pKa of 6.48. This direct influence of CO2 on the state of surface group dissociation explains our recent finding of a CO2-induced decrease of the {zeta}-potential and supports the suggestion of an additional charge regulation caused by molecular CO2. Given the importance of charged surfaces in contact with aqueous electrolytes, we anticipate that our observations bear substantial theoretical challenges and important implications for applications ranging from desalination to bio-membranes.
{"title":"CO2-induced Drastic Decharging of Dielectric Surfaces in Aqueous Suspensions","authors":"Peter Vogel, David Beyer, Christian Holm, Thomas Palberg","doi":"arxiv-2409.03049","DOIUrl":"https://doi.org/arxiv-2409.03049","url":null,"abstract":"We study the influence of airborne CO2 on the charge state of carboxylate\u0000stabilized polymer latex particles suspended in aqueous electrolytes. We\u0000combine conductometric experiments interpreted in terms of Hessinger's\u0000conductivity model with Poisson-Boltzmann cell (PBC) model calculations with\u0000charge regulation boundary conditions. Without CO2, a minority of the weakly\u0000acidic surface groups are dissociated and only a fraction of the total number\u0000of counter-ions actually contribute to conductivity. The remaining counter-ions\u0000exchange freely with added other ions like Na+, K+ or Cs+. From the\u0000PBC-calculations we infer a corresponding pKa of 4.26 as well as a renormalized\u0000charge in reasonably good agreement with the number of freely mobile\u0000counter-ions. Equilibration of salt- and CO2-free suspensions against ambient\u0000air leads to a drastic de-charging, which exceeds by far the expected effects\u0000of to dissolved CO2 and its dissociation products. Further, no\u0000counter-ion-exchange is observed. To reproduce the experimental findings, we\u0000have to assume an effective pKa of 6.48. This direct influence of CO2 on the\u0000state of surface group dissociation explains our recent finding of a\u0000CO2-induced decrease of the {zeta}-potential and supports the suggestion of an\u0000additional charge regulation caused by molecular CO2. Given the importance of\u0000charged surfaces in contact with aqueous electrolytes, we anticipate that our\u0000observations bear substantial theoretical challenges and important implications\u0000for applications ranging from desalination to bio-membranes.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Given the wide range of length scales, the analysis of polymer systems often requires coarse-graining, for which various levels of description may be possible depending on the phenomenon under consideration. Here, we provide a super-coarse grained description, where polymers are represented as a succession of mesosopic soft beads which are allowed to overlap with others. We then investigate the phase separation behaviors in a mixture of such homopolymers based on mean-field theory, and discuss universal aspects of the miscibility phase diagram in comparison with the numerical simulation. We also discuss an extension of our analysis to mixtures involving random copolymers, which might be interesting in the context of chromatin organization in a cell nucleus.
{"title":"Phase separation in soft repulsive polymer mixtures: foundation and implication for chromatin organization","authors":"Naoki Iso, Yuki Norizoe, Takahiro Sakaue","doi":"arxiv-2409.02461","DOIUrl":"https://doi.org/arxiv-2409.02461","url":null,"abstract":"Given the wide range of length scales, the analysis of polymer systems often\u0000requires coarse-graining, for which various levels of description may be\u0000possible depending on the phenomenon under consideration. Here, we provide a\u0000super-coarse grained description, where polymers are represented as a\u0000succession of mesosopic soft beads which are allowed to overlap with others. We\u0000then investigate the phase separation behaviors in a mixture of such\u0000homopolymers based on mean-field theory, and discuss universal aspects of the\u0000miscibility phase diagram in comparison with the numerical simulation. We also\u0000discuss an extension of our analysis to mixtures involving random copolymers,\u0000which might be interesting in the context of chromatin organization in a cell\u0000nucleus.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A problem of the orientational and density structure properties of a confined three-dimensional (3D) and two-dimensional (2D) Hard Gausssian Overlap (HGO) ellipsoids has been revisited using the Onsager-type second virial approximation of Density Functional Theory (DFT) and constant-pressure Monte-Carlo (MC) simulations. At the walls the asssumed particles in 3D are forced to exhibit planar alignment. In the nematic as well as in the smectic regime particles situated apart from the walls attain homeotropic arrangement. This unusual bistable rearrangement is named as the eigenvalue exchange problem of the order parameter tensor. At the same time a bistable arrangement is not observed in the two-dimensional case of the same system. Comparison of the DFT theory and MC simulation results has been given. Whereas comparison of the orientational properties obtained from MC simulations and DFT theory is reasonable for a large range of densities, it does not concern the density profiles. In denser systems differences become larger. It occurred, however, that by manipulating degree of penetrability of the particles at the walls one can influence the surfacial density which improves comparison. A discussion upon the problem what factors promote simultaneous existence of planar and homeotropic arrangement in a confinement has been provided.
利用密度泛函理论（DFT）的昂萨格型第二维里亚近似和恒压蒙特卡洛（MC）模拟，重新探讨了一个封闭的三维（3D）和二维（2D）硬高斯重叠（HGO）椭球体的定向和密度结构特性问题。在壁面上，假定的三维粒子被强化为平面排列。这种不寻常的双稳态重排被称为阶次参数张量的特征值交换问题。这种不寻常的双稳态重排被命名为阶参量张量的特征值交换问题。比较了 DFT 理论和 MC 模拟结果。虽然通过 MC 模拟和 DFT 理论得到的方向特性的比较在很大的密度范围内是合理的，但这并不涉及密度曲线。在密度更大的体系中，两者的差异会变得更大。不过，通过调节颗粒在壁面上的可穿透性，可以影响表面密度，从而改善比较结果。我们还讨论了哪些因素可以促进在约束中同时存在平面和各向同性排列的问题。
{"title":"Orientational properties of the HGO system in a slit geometry in two-dimensional and three-dimensional case from Monte Carlo simulations and Onsager theory revisited","authors":"Agnieszka Chrzanowska","doi":"arxiv-2409.02796","DOIUrl":"https://doi.org/arxiv-2409.02796","url":null,"abstract":"A problem of the orientational and density structure properties of a confined\u0000three-dimensional (3D) and two-dimensional (2D) Hard Gausssian Overlap (HGO)\u0000ellipsoids has been revisited using the Onsager-type second virial\u0000approximation of Density Functional Theory (DFT) and constant-pressure\u0000Monte-Carlo (MC) simulations. At the walls the asssumed particles in 3D are\u0000forced to exhibit planar alignment. In the nematic as well as in the smectic\u0000regime particles situated apart from the walls attain homeotropic arrangement.\u0000This unusual bistable rearrangement is named as the eigenvalue exchange problem\u0000of the order parameter tensor. At the same time a bistable arrangement is not\u0000observed in the two-dimensional case of the same system. Comparison of the DFT\u0000theory and MC simulation results has been given. Whereas comparison of the\u0000orientational properties obtained from MC simulations and DFT theory is\u0000reasonable for a large range of densities, it does not concern the density\u0000profiles. In denser systems differences become larger. It occurred, however,\u0000that by manipulating degree of penetrability of the particles at the walls one\u0000can influence the surfacial density which improves comparison. A discussion\u0000upon the problem what factors promote simultaneous existence of planar and\u0000homeotropic arrangement in a confinement has been provided.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"4 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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