Co-reporter:Jinglin Shen;Zhi Wang;Di Sun;Guokui Liu;Shiling Yuan;Mohamedally Kurmoo;Xia Xin
Nanoscale (2009-Present) 2017 vol. 9(Issue 48) pp:19191-19200
Publication Date(Web):2017/12/14
DOI:10.1039/C7NR06359H
Supramolecular self-assembly, based on non-covalent interactions, has been employed as an efficient approach to obtain various functional materials from nanometer-sized building blocks, in particular, [Ag6(mna)6]6−, mna = mercaptonicotinate (Ag6-NC). A challenging issue is how to modulate the self-assembly process through regulating the relationship between building blocks and solvents. Herein, we report the controlled self-assembly of hexanuclear silver nanoclusters into robust multilayer vesicles in different solvents, DMSO, CH3CN, EG and MeOH. Their unique luminescence enables them to be bifunctional probes to sense Fe3+ and DL-dithiothreitol (DTT). By protonating the Ag6-NC to Ag6-H-NC using hydrochloric acid (HCl), the multilayer vesicles survive in aprotic solvents, DMSO and CH3CN, but are transformed to nanowires in protic solvents, water, EG and MeOH. Our results demonstrated that the solvent-bridged H-bond plays a key role in the evolution of the morphologies from vesicles to nanowires. Moreover, the nanowires could further hierarchically self-assemble in water into hydrogels with high water content (99.5%), and with remarkable mechanical strength and self-healing properties. This study introduces a robust cluster-based building block in a supramolecular self-assembly system and reveals the significance of aprotic and protic solvents for the modulation of the morphologies of cluster-based aggregates.
Co-reporter:Cunxue He, Heng Zhang, Cunguo Lin, Li Wang, Shiling Yuan
Chemical Physics Letters 2017 Volume 676(Volume 676) pp:
Publication Date(Web):16 May 2017
DOI:10.1016/j.cplett.2017.03.070
•We model the adsorption of mussel protein on two film surfaces.•We investigate the conformation of the adsorbed protein and the interaction between the protein and films.•While adsorption on the films is ruled by van-der Waals interactions.•The interfacial water molecules near the solid films have a profound influence on adsorption behavior of protein.The adhesion of marine life would produce a certain degree of corrosion effect on the hull surface. Shellfish organisms, such as barnacles and mussels, were always used to research the impediment of coating material to protein adsorption. In this work, the adsorbed behaviors of mussel protein on the PDMS and C7F16-SAM surfaces were explored by molecular dynamics (MD) simulations. Simulation results showed that protein was strongly adsorbed onto the hydrophobic surface, as reflected by the large interaction energy; while the adsorption onto the hydrophilic PDMS surface was weak due to two strongly adhered water layers.Download high-res image (121KB)Download full-size image
Co-reporter:Han Zhang, Ling-Yu Guo, Jianmei Jiao, Xia XinDi Sun, Shiling Yuan
ACS Sustainable Chemistry & Engineering 2017 Volume 5(Issue 2) pp:
Publication Date(Web):December 30, 2016
DOI:10.1021/acssuschemeng.6b01805
In this paper, new inorganic–organic hybrid nanoflowers consisting of a Weakley-type polyoxometalate Na9[EuW10O36]·32H2O (denoted as EuW10) and biomolecule dopamine (DA) were fabricated through a simple ionic self-assembly (ISA) method. The hybrid nanoflowers were fully characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, Raman spectra, X-ray diffraction (XRD), and fluorescence spectra. We found that the electrostatic interaction and hydrogen-bonding interaction between EuW10 and DA favored the formation of the hierarchical flowerlike structure with hundreds of nanopetals and their morphologies could be controlled simply by tuning the ratio and respective concentrations of the components. Once forming EuW10/DA vesicles or nanoflowers, the fluorescence of EuW10 was quenched due to the hydrogen bonding between the ammonium group of DA and the oxygen atom of EuW10 that blocked the hopping of the d1 electron in EuW10. Interestingly, the calcinated nanoflower showed excellent decomposition efficiency toward the organic pollutants such as the dyes of methyl orange (MO) and rhodamine B (RhB). Moreover, the catalyst for MO can be reused at least 6 cycles with only a slight dropping of catalytic efficiency, suggesting their promising applications in the treatment of wastewater.Keywords: Catalysis; Dyes; Eu-containing polyoxometalate; Fluorescence; Nanoflowers;
Co-reporter:Jichao Sun, Heng Zhang, Mei Hu, Xiangjia Meng, Shiling Yuan
Chemical Physics Letters 2017 Volume 678(Volume 678) pp:
Publication Date(Web):16 June 2017
DOI:10.1016/j.cplett.2017.04.057
•A cylindrical oil model was performed inside a silica nanopore.•Molecular dynamics simulation was used to obtain the aggregation of oil phase.•Steered MD simulation was performed to study oil migration inside silica nanopore.•Solvent accessible surface area was used to study the oil migration process.Two suggested systems of oil in the porosity of the reservoir rock after water flooding were built with an oil cylinder inside a silica nanopore. A series of MD simulations were performed to obtain the aggregation structure of oil phase. The results revealed that heavy oil components showed different distribution position inside silica nanopore in the two oil systems. Heavy oil molecules in heptane can precipitate and adsorbed on silica surface. Steered MD simulation was used to study the oil displacement. By analyzing solvent accessible surface area (SASA), we demonstrated the migration of heavy oil components at molecular level.The snapshots of oil distribution at different simulation time. (a) system A; (b) system B. Asphaltenes, red; resins, green; light components, brown.Download high-res image (203KB)Download full-size image
Co-reporter:Peng Cui, Heng Zhang, Ying Ma, Qingquan Hao, Gang Liu, Jichao Sun, Shiling Yuan
Chemical Physics Letters 2017 Volume 685(Volume 685) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.cplett.2017.07.075
•Translocation mechanism of preformed particle gel in nanopore was investigated.•Effects of surface chemistry and heterogeneity on translocation was scrutinized.•Properties of hydration layer around different nanopores were compared.The translocation behavior of preformed particle gel (PPG) in porous media is crucial for its application in enhanced oil recovery. By means of non-equilibrium molecular dynamics simulation, the translocation mechanism of PPG confined in different silica nanopores were investigated. The influence of surface chemistry and chemical heterogeneity of silica nanopore on the translocation process was revealed. As the degree of surface hydroxylation increases and the heterogeneity decreases, the pulling force needed to drive PPG decreases. We infer that the nanopore’s surface (i.e. surface chemistry and heterogeneity) affects the translocation of PPG indirectly by forming different hydration layers.Download high-res image (143KB)Download full-size image
Co-reporter:Fengfeng Gao, Guokui Liu, Shiling Yuan
Applied Surface Science 2017 Volume 407(Volume 407) pp:
Publication Date(Web):15 June 2017
DOI:10.1016/j.apsusc.2017.02.087
•The reasons of betaine to enhance the stability of foam films are investigated by molecular simulation.•An electrostatic structure is formed at the air/water interface due to the electrostatic interaction.•The electrostatic structure becomes denser with the increasing concentration of betaine.Zwitterionic betaines are widely used as foam boosters due to these can enhance the stability of foam films. In this paper, mechanistic insights of betaine to improve the stability of alkyl-polyoxyethylene carboxylate (AEC) foam are provided by molecular simulation. In the simulation, we observe the electropositive nitrogen atoms in betaine interact with the electronegative sulfur atoms, an electrostatic structure is formed at the air/water interface. Interaction energies of the mixed surfactants are calculated by the quantum chemistry methods. The calculations show betaine-AEC and betaine–betaine possess attractive interaction, and that AEC–AEC has repulsion to each other. In the other words, the repulsion between the headgroups of anionic surfactants is relaxed by betaine. Additionally, the influence of concentration of betaine on the stability of foam films is also simulated. The RDF and coordination numbers show that the electrostatic structures become denser with the increasing concentration of betaine. Therefore, entry barrier is enhanced accordingly. The SMD simulation also demonstrates the same variation tendency of entry barrier. The simulation details provide vital supplements to experiments.
Co-reporter:Long Bai, Enze Li, Zhiping Du, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 522(Volume 522) pp:
Publication Date(Web):5 June 2017
DOI:10.1016/j.colsurfa.2017.02.062
•The effects of solute cations on the packing of PMMA substrates were studied by MDS.•The hydrophobic interaction between cations and water was evaluated through P(θ).•The more polar the cation is, the more water molecules penetrate into the substrate.•Water/salt bridge structure can form between water/cations and PMMA chains.•Water/salt bridges can induce the swelling/collapse of PMMA substrates respectively.The structure of polyelectrolyte substrates could be changed from swelling to collapse by exchanging different electrolyte solutions. However, few investigations explained the phenomenon at the molecular level. In this paper, we employed a molecular dynamics method to simulate the structural changes of poly(methacrylic acid sodium) (PMMA) substrates with the presence of pure water, NH4Cl, tetramethylammonium bromide (TMAB) and tetraethylammonium bromide (TEAB) solution. The simulated results show that the percentage of water molecules penetrated into the substrate and the height of PMMA substrates gradually decrease following the order pure water > NH4+ > TMA+ > TEA+. This may be ascribe to the hydrophobic interaction between the solute cations and water molecules, which can exclude water molecules from the substrates and further influence the height of PMMA substrates. In particular, through the observation at the molecular level, it is obvious that the existence of water bridge structure and salt bridge structure formed between penetrated particles and PMMA chains play a key role in the structural change of PMMA substrates. Water bridges can induce the swelling of PMMA substrates and salt bridges will result in collapse happening. This work may promote a further understanding of the cationic effects on the structure of PMMA substrates at the molecular level and provide a new insight to study the interfacial micro-structure of other biological substrates in future.Download high-res image (105KB)Download full-size image
Co-reporter:Guochun Lv, Fengfeng Gao, Guokui Liu, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2017 Volume 515(Volume 515) pp:
Publication Date(Web):20 February 2017
DOI:10.1016/j.colsurfa.2016.11.066
•The properties of asphaltene at crude oil-water interface were investigated using MD simulation.•Two angles were used to codetermine the orientation of asphaltene at crude oil–water interface.•Hydrogen bond is a signification factor for the stability of asphaltene at oil–water interface.•The aggregation state is most stable for asphaltene molecules at oil–water interface.As the major stabilizer for crude oil emulsion in petroleum industry, asphaltene has been concerned more widespread with the increasing demand of energy in the world. The in-depth understanding on its properties at crude oil-water interface has some beneficial effect on dealing with the emulsion in oil industry. To investigate these interfacial properties at molecular level, molecular dynamics (MD) simulation was utilized. The results show that asphaltene molecules tend to different orientation between them at this interface so as to decrease the repulsive force of aggregation process. Moreover, the contributors to asphaltene stability at crude oil-water interface also were discussed. It mainly includes hydrogen bond networks around asphaltene polar group. The hydrogen bond networks behave like an anchor to grab hold of asphaltene at the interface. The aggregation properties of asphaltene at oil-water interface were obtained by using the umbrella sampling method. The results indicate that aggregation state is most stable for asphaltene molecules at oil-water interface and the system free energy will increase after the aggregate be broken.Download high-res image (566KB)Download full-size image
Co-reporter:Han Zhang, Jichao Sun, Xia Xin, Wenlong Xu, Jinglin Shen, Zhaohua Song, Shiling Yuan
Journal of Colloid and Interface Science 2016 Volume 467() pp:43-50
Publication Date(Web):1 April 2016
DOI:10.1016/j.jcis.2015.12.005
A salt-free surfactant system formed by a peptide amphiphile with short headgroup (PA, C16-GK-3) and a zwitterionic surfactant (dodecyldimethylamine oxide, C12DMAO) in water has been systematically investigated. The microstructures and properties of C16-GK-3/C12DMAO mixed system were characterized using a combination of microscopic, scattering and spectroscopic techniques, including transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR), circular dichroism (CD) and rheological measurements. Rich phase transitions have been observed by adjusting the concentration of C16-GK-3. Investigation of the hydrogels of C16-GK-3/C12DMAO with TEM, SEM and AFM showed that all of these hydrogels form nanobelts. The nanobelt formation is performed in a hierarchical manner: β-sheet peptides and C12DMAO first interact each other to form small aggregates, which then arrange themselves to form one dimensional (1D) left-handed ribbons. The ribbons further aggregated into flat and rigid nanobelts. We proposed a mechanism to interpret the self-assembly process according to the specific peptide structure as well as multiple equilibria between the hydrogen bonding interactions between the headgroups of C16-GK-3, between C12DMAO molecules and the headgroups of C16-GK-3, chirality of the amino acid residues and hydrophobic interactions of the alkyl chains.TEM and AFM height images of the hydrogel with cC12DMAO = 50 g L−1 and cC16-GK-3 = 40 g L−1.
Co-reporter:Jinglin Shen, Xia Xin, Teng Liu, Lu Tong, Guiying Xu, Shiling Yuan
Journal of Colloid and Interface Science 2016 Volume 468() pp:78-85
Publication Date(Web):15 April 2016
DOI:10.1016/j.jcis.2016.01.037
Supermolecular hydrogels were prepared by α-cyclodeatrin (α-CD) and Tyloxapol, which can be considered as an oligomer of the nonionic surfactant polyoxyethylene tert-octylphenyl ether (TX-100) with a polymerization degree below 7. Two carbon materials, graphene oxide (GO) and graphene, were mixed into the α-CD/Tyloxapol hydrogel to adjust the physicochemical properties of hydrogel. In order to get stable graphene dispersion and then mix it with α-CD/Tyloxapol hydrogel, both TX-100 and Tyloxapol were used to disperse graphene for comparison. Interestingly, it can be found that TX-100 could disperse graphene better than Tyloxapol owing to smaller molecular size of TX-100 compared with Tyloxapol. Then, both the α-CD/Tyloxapol/GO and α-CD/Tyloxapol/graphene hydrogels were characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, small angle X-ray scattering (SAXS), X-ray diffraction (XRD) and rheological measurements. The results revealed that the addition of carbon materials into α-CD/Tyloxapol hydrogel can change their microstructures and the rheological properties. Furthermore, it can be confirmed that a little amount of carbon materials could induce fluorescence quenching sharply which could be a promising candidate for optical sensor.
Co-reporter:Han Zhang, Xia Xin, Jichao Sun, Liupeng Zhao, Jinglin Shen, Zhaohua Song, Shiling Yuan
Journal of Colloid and Interface Science 2016 Volume 484() pp:97-106
Publication Date(Web):15 December 2016
DOI:10.1016/j.jcis.2016.08.052
The discovery of a class of self-assembling peptides that spontaneously undergo self-organization into well-ordered structures opened a new avenue for molecular fabrication of biological materials. In this paper, the structure controlled helical nanofibers were prepared by two artificial β-sheet dipeptides with long alkyl chains derived from l- and d-threonine (Thr) and sodium hydroxide (NaOH). These helical nanofibers have been characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffraction (XRD). It was demonstrated that the helicity of the nanofibers could be easily controlled by changing the chirality of the constituent amino acids in the peptide species (d- or l-threonine). Moreover, the hydrogen bonding interactions between the amide groups as well as the hydrophobic interactions among the alkyl chains play important roles in the self-assembly process. It also can be observed that with the passage of time, the hydrogen bonding interactions between the individual nanofiber induced the conversion from nanofibers to nanobelts. Particularly, gold and silver nanoparticles performed good catalytic ability were synthesized using the assembled nanofibers as template.The mechanism of formation of helical structures for (L, L) and (D, D).
Co-reporter:Guokui Liu, Yaoyao Wei, Fengfeng Gao, Shiling Yuan and Chengbu Liu
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 16) pp:11357-11361
Publication Date(Web):24 Mar 2016
DOI:10.1039/C6CP01042C
The micellization of amphiphilic molecules is an important phenomenon in the natural world. However, the origin of entropy change during micellization is still unclear. Molecular dynamics simulation was applied to study configurational entropy change of amphiphilic molecules in micellization. The entropy change of polar heads, hydrophobic chains, vibration, translation and rotation are discussed. Analyses provide a clear physical picture of the entropy increase in micellization, and thus foundations for further study.
Co-reporter:Guokui Liu, Heng Zhang, Gang Liu, Shiling Yuan and Chengbu Liu
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 2) pp:878-885
Publication Date(Web):19 Nov 2015
DOI:10.1039/C5CP05639J
All-atom molecular dynamics (MD) simulations were performed to study the effects of different tetraalkylammonium (TAA+) counterions, including tetramethylammonium (TMA+), tetraethylammonium (TEA+), tetrapropylammonium (TPA+) and tetrabutylammonium (TBA+), on dodecyl sulfate (DS−) micelles. Structural properties, such as the radius of gyration (Rg), micelle radius (Rs), micelle size, solvent accessible surface area (SASA), carbon and sulfur distribution, hydration numbers, and distribution of polar heads on the micelle surface, were investigated. The simulation results show that the longer the carbon chains of the TAA+ counterion, the greater the radius of the micelle formed. TMA+ leads to the most compact structure of the DS− micelle among the five studied systems and DS− and TAA+ formed mixed-micelles. There are mainly four interaction patterns between TAA+ and DS− ions, and the pattern in which two alkyl chains of the TAA+ ion penetrate into the DS− micelle is the most favorable one. Based on the preceding analysis, a model based on this MD method is proposed.
Co-reporter:Han Zhang, Menghong Yu, Aixin Song, Yawen Song, Xia Xin, Jinglin Shen and Shiling Yuan
RSC Advances 2016 vol. 6(Issue 11) pp:9186-9193
Publication Date(Web):06 Jan 2016
DOI:10.1039/C5RA25437J
The self-assembly behavior of a nonionic surfactant (n-dodecyl tetraethylene monoether, C12E4) and a peptide amphiphile (PA, C16-GK-3) mixed system was investigated using a combination of microscopic, scattering and spectroscopic techniques, including transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS), Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) and rheological measurements. The change of the contents of C16-GK-3 and C12E4 induced the transitions in the nanostructures and simultaneously led to changes in macroscopic properties, i.e., mixtures of C12E4 with C16-GK-3 can be hierarchically self-assembled into various helical nanofibers and then further assembled to dandelion-like and dendrite nanostructures by changing the content of C16-GK-3 and C12E4, which resulted in transitions from solution to two phase, sol and hydrogel states that were noted on increasing the concentration of C16-GK-3 at a fixed concentration of C12E4 or varying C12E4 concentration at a fixed concentration of C16-GK-3. On the basis of a series of characterizations, we proposed a possible mechanism of the self-assembly, for which the hydrogen bonding interaction between the headgroups of C16-GK-3 and between C16-GK-3 and C12E4, as well as hydrophobic interaction between the alkyl chains of C16-GK-3 and C12E4, were the main driving forces.
Co-reporter:Yaoyao Wei, Guokui Liu, Zhongni Wang and Shiling Yuan
RSC Advances 2016 vol. 6(Issue 55) pp:49708-49716
Publication Date(Web):16 May 2016
DOI:10.1039/C6RA05188J
All-atom molecular dynamics (MD) simulations were performed to study the aggregation behaviour of different sodium dodecyl benzenesulphonate positional isomers (xΦ12) where x = 1, 2, 3, 4, 5 and 6. In the simulation, the solvent accessible surface area, carbon and sulphur distribution, angle possibility distribution, chain conformation, hydration numbers, distribution of polar heads on the micelle surface, and the interaction energy among the benzene rings were analyzed. The simulated results showed that these six isomer micelles are more elliptical than spherical and the micelle radius increases with the shifting of the benzenesulphonate group from one side to the middle of the alkyl chain. In the micellar aggregate, the short alkyl chains are located at the polar layer of the micelle while the long alkyl chains assemble in the central region of the micelle. In the six different isomers, 1Φ12 isomer shows some special structural features.
Co-reporter:Jinglin Shen, Jinyu Pang, Guiying Xu, Xia Xin, Yingjie Yang, Xiaoyu Luan and Shiling Yuan
RSC Advances 2016 vol. 6(Issue 14) pp:11683-11690
Publication Date(Web):18 Jan 2016
DOI:10.1039/C5RA26464B
Novel fluorescent vesicles based on inclusion complexes of β-cyclodextrins (β-CD) with Tyloxapol were constructed. For comparison, α-cyclodextrins (α-CD) were also selected to form inclusion complexes with Tyloxapol. The vesicles formed by β-CD/Tyloxapol were characterized thoroughly using various techniques including phase behavior observation, transmission electron microscopy (TEM), freeze fracture transmission electron microscopy (FF-TEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), 2D 1H–1H ROESY NMR, fluorescence spectra, Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The results of TEM, SEM, FF-TEM, AFM indicated the formation of vesicles of β-CD/Tyloxapol; they presented aggregation-induced emission enhancement properties because the alkyl chain of Tyloxapol molecules enters the cavity of β-CD and forms inclusion complexes, while α-CD/Tyloxapol showed aggregation-induced quenching fluorescence emission properties owing to the interaction between PEO chain of Tyloxapol molecules and α-CD. Moreover, the vesicles of β-CD/Tyloxapol were responsive to external stimuli and their fluorescent intensities were changed by various environmental conditions such as urea, phenylalanine, α-amylase and NaOH. These properties made our vesicle a promising candidate as novel, smart, stimuli-responsive, fluorescent vesicular sensors.
Co-reporter:Heng Zhang, Ying Ma, Qingquan Hao, Hua Wang, Gang Liu and Shiling Yuan
RSC Advances 2016 vol. 6(Issue 9) pp:7172-7180
Publication Date(Web):06 Jan 2016
DOI:10.1039/C5RA24282G
Preformed particle gels (PPG) as a potential oil-displacement agent, composed of cross-linked partially hydrolyzed polyacrylamide, are being applied to promote the oil recovery ratio in several oil fields in China. At the molecular level, a molecular dynamics simulation of PPG transporting through nanopores was performed to investigate its propagation mechanisms during gel injection. Initially, a silica nanopore was modeled as a finite-length cylindrical pore, in which the inner surface was fully hydroxylated. Then, a swollen PPG with a smaller size was put in. After a long enough simulation, the hydration layer induced by silica pore surface was discussed to study the effect on the transport of the PPG. Steered molecular dynamics was then used to mimic the transport of the PPG under injection pressure. The results suggested that this hydration layer served as a physical and energy barrier that keeps the PPG away from the pore surface by analyzing radial number density distributions, orientational arrangement, dependence of the diffusive mobility, hydrogen bonding characteristics and potential of mean force. In addition, the lubrication of the hydration layer may reduce the resistance that the PPG has to overcome while transporting through nanopores. These factors will promote the propagation of the PPG within the nanopores and reduce the injection pressure. The simulated results are expected to provide molecular level insights into the mechanism of PPG transporting through nanoporous media or the molecular design of optimized PPG.
Co-reporter:Hui Yan
The Journal of Physical Chemistry C 2016 Volume 120(Issue 5) pp:2667-2674
Publication Date(Web):January 20, 2016
DOI:10.1021/acs.jpcc.5b09841
We investigated the effect of surfactants on the oil displacement process inside a nanoscale silica pore using molecular dynamics simulations. First, an oil cylinder was built inside a silica pore to mimic residual oil in the porosity of the reservoir rock after water flooding. In the simulations, we focused on a layering organization of oil molecules adsorbed onto the pore surface, and then a series of equilibrium MD simulations were run to obtain the organization structures of the oil drop in the presence or absence of surfactant molecules. These simulated results showed that the surfactant could disturb the layering organization of the oil drop, since the hydrophobic chains of surfactant molecules could penetrate into the oil phase. And around the polar head of the surfactant, water molecules could form water channels between the oil phase and solid surface, which is vital to the displacement process. Finally, we used steered molecular dynamics (SMD) method to mimic the displacement and migration process of an oil drop inside the pore. From SMD calculations, detailed information about the process was obtained, and the free energy of the process was calculated using the WHAM method. Through analysis of the free energy, we demonstrated the mechanism of surfactants aiding in the oil recovery at a molecular level. Our study provided information on the oil displacement within a nanoscale pore at the molecular level, which is expected to provide useful information for enhanced oil recovery (EOR) experiments.
Co-reporter:Gang Liu, Heng Zhang, Guokui Liu, Shiling Yuan, Qingzeng Zhu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016 Volume 509() pp:401-407
Publication Date(Web):20 November 2016
DOI:10.1016/j.colsurfa.2016.09.029
•The kinetic MC simulation is employed to study the center shift of template-induced deposition.•Two mechanisms of center shift are proposed: nucleation deviation and growth deviation.•The dependence of the shift mechanism on the interactions has been confirmed.•Based on details of the two shift mechanisms, a method for reducing center deviation is supplied.In this paper, the center shift of organic particles on template-induced surface is systematically studied by a series of kinetic Monte Carlo simulations. The morphology evolution of center shift, the dependence of center deviation on interactions and the effects of geometrical sizes are obtained. Based on the morphology evolution of center shift, two different mechanisms are proposed, i.e. nucleation deviation and growth deviation. The former is mainly induced by the lateral nucleation of deposited particles, and the latter is mainly determined by the randomly diffusion motion of deposited particles. The two mechanisms present a significant difference for the evolution of center deviation. Based on the details of the two mechanisms, a possible method for reducing the center deviation is also supplied in the simulation.
Co-reporter:Jinglin Shen, Xia Xin, Teng Liu, Shubin Wang, Yingjie Yang, Xiaoyu Luan, Guiying Xu, and Shiling Yuan
Langmuir 2016 Volume 32(Issue 37) pp:9548-9556
Publication Date(Web):August 26, 2016
DOI:10.1021/acs.langmuir.6b01829
Giant vesicles (1–10 μm) were constructed via a facile ionic self-assembly (ISA) strategy using an anionic dye Acid Orange II (AO) and an oppositely charged ionic-liquid-type cationic surfactant 1-tetradecyl-3-methylimidazolium bromide (C14mimBr). This is the first report about preparing giant vesicles through ISA strategy. Interestingly, the giant vesicle could keep the original morphology during the evaporation of solvent and displayed solid-like properties at low concentration. Moreover, giant vesicles with large internal capacity volume and good stability in solution could also be achieved by increasing the concentrations of AO and C14mimBr which contributed to the increase of the other noncovalent cooperative interactions. In order to facilitate comparison, a series of parallel experiments with similar materials were carried out to investigate and verify the driving forces for the formation of these kinds of giant vesicles by changing the hydrophobic moieties or the head groups of the surfactants. It is concluded that the electrostatic interaction, hydrophobic effect and π–π stacking interaction play key roles in this self-assembly process. Importantly, the giant vesicles can act as a smart microcarrier to load and release carbon quantum dot (CQD) under control. Besides, the giant vesicles could also be applied as a microrector to synthesize monodispersed Ag nanoparticles with diameter of about 5–10 nm which exhibited the ability to catalyze reduction of 4-nitroaniline. Therefore, it is indicated that our AO/C14mimBr assemblies hold promising applications in the areas of microencapsulation, catalyst support, and lightweight composites owing to their huge sizes and large microcavities.
Co-reporter:Han Zhang, Lingyu Guo, Zengchun Xie, Xia XinDi Sun, Shiling Yuan
Langmuir 2016 Volume 32(Issue 51) pp:13736-13745
Publication Date(Web):November 19, 2016
DOI:10.1021/acs.langmuir.6b03709
In this work, through the aqueous phase self-assembly of an Eu-containing polyoxometalate (POM), Na9[EuW10O36]·32H2O (EuW10) and different amino acids, we obtained spontaneously formed vesicles that showed luminescence enhancement for EuW10 and arginine (Arg), lysine (Lys), or histidine (His) complexes, but luminescence quenching for EuW10 and glutamic acid (Glu) or aspartic acid (Asp) complexes. The binding mechanisms between them have been explored at the molecular level by using different characterization techniques. It was found that EuW10 acted as polar head groups interact with the positively charged residues for alkaline amino acids, protonated amide groups for acidic amino and nonpolar acid aminos through electrostatic interactions, and the remaining segments of amino acids served as relatively hydrophobic parts aggregated together forming bilayer membrane structures. Moreover, the different influences of amino acids on the fluorescence property of EuW10 revealed that the electrostatic interaction between the positive charged group of amino acid and the polyanionic cluster dominates the fluorescence properties of assemblies. Furthermore, a turn-off sensing application of the EuW10/Arg platform to probe dopamine (DA) against various other biological molecules such as neurotransmitters or amino acids was also established. The concept of combining POMs with amino acids extends the research category of POM-based functional materials and devices.
Co-reporter:Ying Ma, Heng Zhang, Qingquan Hao, Gang Liu, Hua Wang, and Shiling Yuan
The Journal of Physical Chemistry C 2016 Volume 120(Issue 34) pp:19389-19395
Publication Date(Web):August 15, 2016
DOI:10.1021/acs.jpcc.6b04832
Understanding the translocation mechanism of preformed particle gel (PPG) through the nanoporous medium is crucial for gel treatment during enhanced oil recovery. On the basis of nonequilibrium molecular dynamics simulation, the translocation process of PPG in silica nanopores consisting of two different diameters was investigated. During the simulation, an external pulling force was applied to PPG representing the injection pressure. The simulation results suggest that a synergetic deformation and dehydration of PPG occurs during the translocation from the wide side into the narrow side. The energy barrier of the translocation process mainly result from the conformational energy change of PPG (mainly from the angle bend and dihedral torsion) and the dissociation energy barrier between PPG’s hydrophilic groups and water. Furthermore, the nanopore size has a crucial impact on the translocation mechanism of PPG, not only the degree of the deformation and dehydration near the entrance, but also the translocation mechanism after they entered the nanopore. For a nanopore with a large diameter, PPG can reabsorb water to induce a complete hydration layer around it after entry. However, for the nanopore with a small size, the compression from the pore restricts PPG’s rehydration ability. Without the screen and lubrication of the hydration layer, the pulling force needed to drive PPG increased rapidly, which means a larger injection pressure in the macroscopic view. The findings are helpful for understanding the translocation process of PPG in porous media on molecular level and, also, will facilitate technology developments for enhancement of recovery efficiency of petroleum.
Co-reporter:Jinglin Shen, Xia Xin, Guokui Liu, Jinyu Pang, Zhaohua Song, Guiying Xu, and Shiling Yuan
The Journal of Physical Chemistry C 2016 Volume 120(Issue 48) pp:27533-27540
Publication Date(Web):November 17, 2016
DOI:10.1021/acs.jpcc.6b08140
A fluorescent solid-like giant vesicle was prepared by using an anionic dye methyl orange (MO) and an oppositely charged surfactant 1-tetradecyl-3-methylimidazolium bromide (C14mimBr) on the basis of the ionic self-assembly (ISA) strategy. The properties of MO/C14mimBr complexes were comprehensively characterized. The results indicated that the giant vesicle was formed by the fusion of small vesicles and could keep its original structure during the evaporation of solvent. Besides, the giant vesicles exhibit luminescent property owing to the break of intermolecular π–π stacking of MO, which achieves the transformation from aggregation-caused quenching to aggregation-induced emission by noncovalent interaction. Moreover, MO/C14mimBr complexes also exhibit smart pH-responsive characteristics and abundant thermic phase behavior. That is, various fluorescent structures (polyhedron, giant vesicle, chrysanthemum, peony-like structure) were obtained when pH ≥ 4, whereas a simple nonfluorescent structure (microflake) was obtained when pH = 2 due to the changes of MO configuration. Thus, the fluorescence behavior can be predicted with the color change directly visible to the naked eye by changing the pH. It is expected that the facile and innovative design of supramolecular material by the ISA strategy could be used as pH detection probes and microreactors.
Co-reporter:Gang Liu, Heng Zhang, Guokui Liu, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2016 Volume 494() pp:186-193
Publication Date(Web):5 April 2016
DOI:10.1016/j.colsurfa.2016.01.033
•The kinetic Monte Carlo simulations were employed to study the hetero-patterning of deposited organic molecules on template-induced surface.•A detailed and quantitative analysis was conducted to determine the dependence of anisotropic growth on the amount of particles and molecular interactions.•The effects of prepatterns size and the amount of deposited particles on the organic hetero-structure growth process obtained in the simulations are well consistent with experimental outcome.In this paper, the hetero-patterning of organic particles on template-induced surface are systematically studied by a series of kinetic Monte Carlo simulations. The details of anisotropic growth process, the dependence of aggregation morphology on interactions and the effects of geometrical sizes are obtained. The simulated results showed that the size of prepattern plays a crucial role in the hetero-structure growth process. Especially for the deposited morphology, the thickness of organic film is relevant with the prepattern size. In the simulation, the dependence of deposition morphology on the amount of deposited particles is also obtained. The results also showed that the thickness ratio on two type squares even can be completely controlled by the amount of deposited particles. Besides the size of template and the amount of deposited particles, the interactions between different particles also exhibit strong influence on the deposited morphology. Both the weak and strong organic particle-organic particle interactions can reduce the anisotropic growth, while the moderate value can result in the maximum anisotropic growth.
Co-reporter:Hui Yan, Shiling Yuan, Suyuan Zeng, Meiju Niu
Applied Surface Science 2015 Volume 349() pp:163-168
Publication Date(Web):15 September 2015
DOI:10.1016/j.apsusc.2015.04.211
Highlights
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We modeled condensed and expanded monolayers on mica substrate.
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The structural features of different monolayers were studied upon the MD methods.
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Perylene prefers to deposit onto the surface of LC monolayer.
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The density of alkyl chains on the substrate influences the diffusion of perylene.
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Deposition mechanism was explained using umbrella sampling simulations.
Co-reporter:Jichao Sun, Heng Zhang, Kai Guo and Shiling Yuan
RSC Advances 2015 vol. 5(Issue 124) pp:102182-102190
Publication Date(Web):23 Nov 2015
DOI:10.1039/C5RA19508J
Dipeptide sodium salts derived from alanine can readily self-assemble into helical nanostructures as observed in experiments. But what are the primary driving forces of the organizing process at the molecular level is still worthwhile discussing. In this study, molecular dynamics simulation was employed to investigate the nanostructure at the molecular level, and different driving forces were deduced for the self-assembled process of dipeptide sodium salts. The simulated results showed that van der Waals forces are in favour of the aggregation of alkyl chains in the solution, resulting in one hydrophobic core of condensed fibril. Hydrogen bonds and electrostatic interactions represented by the water-bridge and salt-bridge structure between dipeptide molecules are major driving forces for the hydrophilic amide groups to form the nanostructure shell. In the self-assembly, the bilayer structure of the dipeptide was the basic unit of helical fibril. The structures of the salt bridge and water bridge are distributed over the surface of the fibril, weakening the electrostatic interaction between the dipeptide molecules. The results show that water molecules penetrating into the self-assembled structure should be considered as one part of the peptide self-assembly. Analysis of the self-assembled conformation showed that the hydrophilic amide groups aggregated as small clusters in the hydrophilic shell. Terminal amide groups, forming hydrogen bonds with water molecules around the chiral carbon atom, decide the handedness of the self-assembly.
Co-reporter:Lin Wang, Xia Xin, Mengzhou Yang, Jinglin Shen and Shiling Yuan
RSC Advances 2015 vol. 5(Issue 84) pp:68404-68412
Publication Date(Web):06 Aug 2015
DOI:10.1039/C5RA13497H
Graphene oxide (GO) was successfully incorporated into a hybrid lyotropic liquid crystal (LLC) matrix formed by two kinds of surfactants n-dodecyl tetraethylene monoether (C12E4) and 1-dodecyl-3-methylimidazolium bromide ionic liquid (C12mimBr). By changing the ratios of C12E4 and C12mimBr, two types of C12E4/C12mimBr LLC matrixes (lamellar and hexagonal phase) were formed and the effects of the concentration of GO and temperature on the properties of GO/C12E4/C12mimBr LLC composites were systematically investigated by polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS) and rheological measurement. Both POM observations and SAXS results indicated that GO can be well-dispersed in the hybrid LLC matrixes at room temperature. Moreover, after the incorporation of GO, the temperature tolerance of GO/C12E4/C12mimBr LLC composites were enhanced compared with pure C12E4/C12mimBr hybrid LLC and aggregated GO was not observed in the C12E4/C12mimBr LLC hybrid hexagonal matrix with the increase of temperature while it can be observed in the C12E4/C12mimBr LLC hybrid lamellar matrix. The results of rheological measurements showed that the addition of GO were helpful for enhancing the mechanical properties of C12E4/C12mimBr LLC. Thus, the success preparation of GO/hybrid LLC composites can highly improve the thermal stability of these materials and widen the applications of GO/LC materials in nanotechnology, electrochemical, drug delivery systems and bioengineering areas.
Co-reporter:Gang Liu, Heng Zhang, Wenchong Wang, Shiling Yuan
Chemical Physics Letters 2015 Volume 628() pp:54-59
Publication Date(Web):16 May 2015
DOI:10.1016/j.cplett.2015.04.007
•The KMC simulations are used to study the area-selective patterning.•Molecular interactions play a key role in anisotropic wetting of organic particle.•The square root of time law widely observed in experiment has been confirmed.•The dependence of flow velocity on temperature agrees with experimental outcome.•The geometry effect of channel exerts significant effect on the flow velocity.In this Letter, the kinetic Monte Carlo simulations are employed to study the microscopic mechanisms of patterning molten organic particles based on liquid behavior on templated surfaces. The simulated results show that the binding energy difference between the organic particle and templated surface plays a key role in the anisotropic wetting of organic particles. And the square root of time law between the spreading distance and simulated time on different temperatures is well consistent with experimental observation. We also note that the geometry effect of channel edge has very significant effect on the dependence of spreading velocity on template dimensions.
Co-reporter:Lin Wang, Xia Xin, Mengzhou Yang, Xin Ma, Jinglin Shen, Zhaohua Song, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2015 Volume 483() pp:112-120
Publication Date(Web):20 October 2015
DOI:10.1016/j.colsurfa.2015.07.044
•We used sodium deoxycholate and graphene oxide to prepare hydrogels.•The introduction of GO to NaDC hydrogel enhances the mechanical strength of the composite hydrogel.•The incorporation of GO exhibits good dye absorption property for hydrogels.Sodium deoxycholate/graphene oxide (NaDC/GO) composite hydrogels were prepared in varying salinity. The hydrogels were characterized in detail by phase behavior study, transmission electron microscopy (TEM) observations, scanning electron microscopy (SEM) observations, X-ray powder diffraction (XRD) mesurements, Fourier transform infrared (FT-IR) spectra and rheological measurements. It was found that the introduction of GO to NaDC hydrogel enhances the mechanical strength of the composite hydrogel. When contacted with methylene blue solution, methylene blue can be absorbed inside the gel accompanied with a swelling of the gel. On the contrary, the hydrogel forms by NaDC only dissolves in methylene blue solution, forming a homegeous solution. Further study reveals that the gelation of NaDC/GO composite gel can be accelerated by an increase in salinity. This work may open the door for a variety of applications of NaDC/GO composite hydrogels such as in biotechnology, drug delivery and sewage treatment.Schematic representation of the structure of NaDC/GO hydrogel.
Co-reporter:Lin Wang, Xia Xin, Kai Guo, Mengzhou Yang, Xin Ma, Jing Yuan, Jinglin Shen and Shiling Yuan
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 28) pp:14771-14780
Publication Date(Web):29 Apr 2014
DOI:10.1039/C4CP00622D
Carbon nanotubes (CNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix at room temperature through spontaneous phase separation. The phase separation process occurred in n-dodecyl tetraethylene monoether (C12E4) solutions induced by the hydrophilic polymer, poly(ethylene glycol) (PEG). It was found that the molecular weight of PEG has a significant effect on the CNTs–C12E4 system, which not only influences the phase behavior of the system but also changes the properties of the CNTs–LLC composites. Polarized optical microscopy (POM) images, combined with small-angle X-ray scattering (SAXS) results, indicate that CNTs incorporate within the layers of the lamellar LLCs without destroying the structure of LLCs. Moreover, UV-vis absorption, Raman spectra and rheological measurements were performed to investigate the characteristic properties of the CNTs–LLC composites. This study not only gives a more comprehensive understanding of polymer-induced phase separation, but also expands the potential uses of CNTs–LLC composites in nanotechnology.
Co-reporter:Lin Wang, Xia Xin, Mengzhou Yang, Xin Ma, Zhenyu Feng, Rui Chen, Jinglin Shen and Shiling Yuan
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 38) pp:20932-20940
Publication Date(Web):22 Aug 2014
DOI:10.1039/C4CP02634A
Two kinds of carbon materials, i.e., graphene and graphene oxide (GO), were successfully incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl tetraethylene monoether (C12E4). The properties of graphene–C12E4 and GO–C12E4 LLC composites were characterized by UV-vis absorption, transmission electron microscopy (TEM) observations, polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS) and rheological measurements. SAXS results indicate that both graphene and GO are well-dispersed in the C12E4 LLC matrix and some interactions occur between the C12E4 LLC matrix and graphene (or GO) sheets. Moreover, it is demonstrated that graphene interacts with the hydrophobic part of C12E4 LLC while GO mainly interacts with the hydrophilic part of C12E4 LLC because of the different properties of graphene and GO. Integration of graphene and GO into C12E4–PEG systems by a spontaneous phase separation method reveals the different interaction mechanisms of graphene and GO with C12E4 LLC. It can be concluded that the mechanical and electrical properties of the C12E4 LLC have been largely improved by the incorporation of graphene and GO, which opens the door for wide applications in nanotechnology, electrochemical and biochemical areas.
Co-reporter:Fengfeng Gao, Hui Yan, Qiwei Wang and Shiling Yuan
Physical Chemistry Chemical Physics 2014 vol. 16(Issue 32) pp:17231-17237
Publication Date(Web):17 Jun 2014
DOI:10.1039/C4CP02038C
In enhanced oil recovery (EOR), the micro-oil droplet heavily affected the stability of foam and prevented foam flooding. In this paper, the oil bridge-stretching mechanism of foam rupture was described through molecular dynamics with the aim of providing supplements to the experiments at the molecular level. Two important phenomena for foam rupture have been pointed out by the simulation. One is about the pseudoemulsion film, representing the stability of the oil–water–air three phase interface. The bound water connecting the headgroups of the surfactant through strong H-bonding interactions played a vital role in the stability of the pseudoemulsion film. These water molecules could hinder the disappearance of the water phase in the pseudoemulsion film. The additional energy barrier, which was influenced by the surfactant concentration, also played a vital role in preventing the destruction process. The other factor is about the oil bridge, which appeared after the destruction of the pseudoemulsion film. The external horizontal force stretched the bridge resulting in the destruction of the bridge. The process was decided by the properties of the oil molecules. In the simulation, the stretching force was divided into three stages including the initial increasing force, the middle equilibrium force and the final decreasing force. Especially the second equilibrium force, which stretched the middle of the oil bridge so that it became thin, was vital to the foam rupture. The concentration and properties of the oil molecules were the crucial factors for foam rupture. The simulated results offer important supplements to experiments.
Co-reporter:Heng Zhang, Gang Liu, Wenchong Wang, Lifeng Chi and Shiling Yuan
RSC Advances 2014 vol. 4(Issue 48) pp:25005-25010
Publication Date(Web):29 May 2014
DOI:10.1039/C4RA01756K
Template directed growth of functional organic molecules is a recently developed technique to generate organic micro/nano-structures on surfaces. Using templates of a metal patterned substrate, two different mechanisms were observed: area selective nucleation on predefined patterns with molecules nucleated on top of patterns and step-edge induced area selective growth on the substrate. Until now, much work has been done to investigate the microscopic mechanism of the former one. However, little attention was paid to the latter one. Here in this work, a series of kinetic lattice Monte Carlo simulations were conducted to get deeper insight into the microscopic mechanism of step-edge induced area selective growth. The time-resolved process of structure formation, the relationship between nucleation control efficiency and template size, and different growth regimes were studied. The results agree well with experimental speculation while selecting appropriate interactions.
Co-reporter:Fengfeng Gao, Zhen Xu, Guokui Liu, and Shiling Yuan
Energy & Fuels 2014 Volume 28(Issue 12) pp:7368-7376
Publication Date(Web):November 17, 2014
DOI:10.1021/ef5020428
Carboxyl asphaltene is commonly discussed in the petroleum industry. In most conditions, electroneutral carboxyl asphaltene molecules can be deprotonated to become carboxylate asphaltenes. Both in crude oil and at the oil/water interface, the characteristics of anionic carboxylate asphaltenes are different than those of the carboxyl asphaltenes. In this paper, molecular dynamics (MD) simulations are utilized to study the structural features of different asphaltene molecules, namely, C5 Pe and anionic C5 Pe, at the molecular level. In crude oil, the electroneutral C5 Pe molecules prefer to form a steady face-to-face stacking, while the anionic C5 Pe molecules are inclined to form face-to-face stacking and T-shaped II stacking because of the repulsion of the anionic headgroups. Anionic C5 Pe has a distinct affinity to the oil/water interface during the simulation, while the C5 Pe molecules persist in the crude oil domain. A three-stage model of anionic C5 Pe molecules adsorbed at the oil/water interface is finally developed.
Co-reporter:Hua Wang, Heng Zhang, Shiling Yuan, Zhen Xu, Chengbu Liu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014 Volume 454() pp:104-112
Publication Date(Web):20 July 2014
DOI:10.1016/j.colsurfa.2014.04.009
•The transition from monolayer adsorption of a polymer–surfactant complex to multilayer structures was observed at the interface.•For multilayer structures, the two polymer chains were linked by two layers of surfactant.•The hydrophobic interaction between surfactant tails is the main reason for the formation of a layered structure.•The electrostatic interaction was the main driving force for the binding of surfactant to the polyelectrolyte.The adsorption of polyelectrolyte–surfactant mixture of sodium poly(acrylic acid) (NaPAA) and dodecyl trimethyl ammonium bromide (C12TAB) at the air/water interface was studied using molecular dynamics simulation. In our simulations, the transition from monolayer adsorption of a polymer–surfactant complex to a multilayer structure was observed with increasing surfactant concentration at the interface. For the multilayer structure, the two polyelectrolyte chains were linked by two layers of surfactant molecules which adopted a tail-to-tail arrangement. The results indicated that the electrostatic interaction was the main driving force for the binding of surfactants to the polyelectrolyte, meanwhile the hydrophobic interaction between surfactant tails induced a layer-by-layer packing arrangement at high surfactant concentration. The dynamic properties of inorganic ions implied that the complex of polyelectrolyte and surfactant was an ion-exchange process. Our conclusions are in accordance with experimental results on polyelectrolytes and ionic surfactants.MD simulations snapshots of the adsorption structure of oppositely charged polyelectrolyte and ionic surfactant complexes at the interface.
Co-reporter:Congyun Zhang, Zhen Xu, Hui Yan, Fengfeng Gao, Shiling Yuan
Chemical Physics Letters 2013 Volume 571() pp:38-43
Publication Date(Web):20 May 2013
DOI:10.1016/j.cplett.2013.03.075
Highlights•Molecular dynamics was used to study the rubrene deposition behavior on different templates.•Quantum chemistry calculation was employed to validate the π-stacking of rubrene.•Template structures exert significant effect on the rubrene growth behavior and crystallinity.•The rubrene molecules diffused and preferentially deposited along the step-edge of SAM.•The area-selective growth can be due to the binding energy difference.Molecular dynamics simulations and quantum mechanics calculation were employed to study the deposition behavior of organic luminescent molecules rubrene onto bare dioxide silicon substrate and self-assembled monolayers (SAM) patterned substrate. A mixed system was constructed to investigate the edge-induced area-selective growth. Our simulation results suggest that the functionalized SAM decoration on the substrate surface exerts significant effect on the growth behavior and crystallinity of rubrene molecules. In the mixed system, the rubrene molecules diffused and preferetially deposited along the step-edge of SAM and formed a typical π-conjugated structure by standing up-right.Graphical abstract
Co-reporter:Congyun Zhang, Hui Yan, Kai Lv, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 424() pp:59-65
Publication Date(Web):5 May 2013
DOI:10.1016/j.colsurfa.2013.02.014
In this paper, we report a facile synthesis of mesoporous silica nanomaterials by utilizing cetyltrimethylammonium bromide (CTAB)/sodium dodecylbenzenesulfonate (SDBS) vesicle systems as templates. The porous nanostrucures with varied morphologies, including nanocapsules and nanospheres can be successfully fabricated by simply regulating the volume ratio (R) of ethanol to ethyl ether. In addition, we also investigated the influences of vesicular solution concentration on the nanomaterial morphologies with two different vesicle systems. A vesicle-templating mechanism was proposed to explain the formation of porous silica nanostructures.Highlights► A facile path to fabricate hierarchically mesoporous silica particles was explored. ► Vesicle bilayer or chamber was simply used as compartmentalized reaction space. ► The variation of sample morphology was achieved by changing co-solvent volume. ► The vesicle concentration also greatly affects the physical property of materials.
Co-reporter:EnZe Li;ZhiPing Du;ShiLing Yuan
Science China Chemistry 2013 Volume 56( Issue 6) pp:773-781
Publication Date(Web):2013 June
DOI:10.1007/s11426-013-4835-7
The microscopic behaviors of a water layer on different hydrophilic and hydrophobic surfaces of well ordered self-assembled monolayers (SAMs) are studied by molecular dynamics simulations. The SAMs consist of 18-carbon alkyl chains bound to a silicon(111) substrate, and the characteristic of its surface is tuned from hydrophobic to hydrophilic by using different terminal functional groups (-CH3, -COOH). In the simulation, the properties of water membranes adjacent to the surfaces of SAMs were reported by comparing pure water in mobility, structure, and orientational ordering of water molecules. The results suggest that the mobility of water molecules adjacent to hydrophilic surface becomes weaker and the molecules have a better ordering. The distribution of hydrogen bonds indicates that the number of water-water hydrogen bonds per water molecule tends to be lower. However, the mobility of water molecules and distribution of hydrogen bonds of a water membrane in hydrophobic system are nearly the same as those in pure water system. In addition, hydrogen bonds are mainly formed between the hydroxyl of the COOH group and water molecules in a hydrophilic system, which is helpful in understanding the structure of interfacial water.
Co-reporter:Heng Zhang, Hua Wang, Guiying Xu, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 417() pp:217-223
Publication Date(Web):20 January 2013
DOI:10.1016/j.colsurfa.2012.10.066
Fmoc protected D-Ala-D-Ala dipeptides were known to self-assemble into supramolecular hydrogel with interesting properties. However their molecular mechanisms were not well understood. In this study, a series of coarse grained molecular dynamics simulation were conducted to investigate the formation of this hydrogel at different concentrations. The three dimensional network of hydrogel and the stacking of the Fmoc planes were observed intuitively from the snapshots of the trajectory. Importantly, by analyzing the RDF of Fmoc planes’ centriods and the distribution of neighboring Fmocs, we confirmed the π–π interaction as the mainly driving force for the gelation process.Highlights► Simulation of gelation was expanded to large scale and long time by using CG-MD. ► We got the gel’s configuration on molecular level (π stacking, entanglement). ► We confirmed the π–π stacking as the mainly gelation driven force.
Co-reporter:Hui Yan, Peng Cui, Cheng-Bu Liu, and Shi-Ling Yuan
Langmuir 2012 Volume 28(Issue 11) pp:4931-4938
Publication Date(Web):February 23, 2012
DOI:10.1021/la300146s
In the present work, the structural and dynamical aspects of the solubilization process of pyrene within a sodium dodecyl sulfate micelle were studied using molecular dynamics simulations. Our results showed that free pyrene as the fluorescence probe can be spontaneously solubilized into the micelle and prefers to be located in the hydrophobic core region. As the local concentration of pyrene increased, two molecular probes could enter into the core hydrophobic region and the excited dimer of pyrene molecules was formed, showing a stacking mode of π–π conjugation. Since the π–π stacking interaction between the two pyrene molecules was very weak, formation of the excimer was a dynamic process with the two pyrene molecules alternately separating and associating with each other. In this case, the two pyrene molecules were found to be mainly distributed in the palisade layer of the micelle due to the balance between the weak π–π stacking interaction and the hydrophobic interaction of probe molecules with the surfactant tails.
Co-reporter:Qian Liu, Shiling Yuan, Hui Yan, and Xian Zhao
The Journal of Physical Chemistry B 2012 Volume 116(Issue 9) pp:2867-2875
Publication Date(Web):February 15, 2012
DOI:10.1021/jp2118482
The mechanism of oil detachment from solid surfaces in aqueous surfactant solutions is studied by molecular dynamics simulations. At the initial simulation, the hydrophilic silica surface changes into a hydrophobic one due to the adsorption of the alkane molecules. Two-dimensional ordered arrangement of alkane molecules on the first layer is the key to the oil detachment from the silica surface. Upon addition of cetyltrimethylammonium bromide (CTAB) solution, the alkane molecules on the solid surface can be detached from a hydrophilic silica surface. Ultimately, the silica surface becomes hydrophilic, and the oil molecules are solubilized in the surfactant micelles. During the process of oil detachment, it is demonstrated that the formation of a water channel in the oil phase between the surfactant solution and the silica surface is vital for the oil detachment. Meanwhile, water molecules can penetrate the oil–water interface by diffusion and form the gel layer at the water–silica interface under the hydrogen-bonding and electrostatic interaction, in the close vicinity of the contact line. Both of these will accelerate the removal of the oil molecules from the silica surface under the surfactant solution. According to the energy and configurations with time evolution, one three-stage model of oil detachment from the silica surface is developed at the molecular level. The simulation results agree with the experimental phenomenon.
Co-reporter:Fen Wang;Rong Fan;HaiTao Kang;GuiYun Jin;FengShi Luan
Science Bulletin 2012 Volume 57( Issue 17) pp:2148-2154
Publication Date(Web):2012 June
DOI:10.1007/s11434-012-5029-y
The Beiqian site located in Jimo city, Qingdao, a few kilometers from the modern coastline was excavated in 2007, 2009 and 2011. A large number of human bones from the early Dawenkou period were unearthed. Through C and N stable isotopic analysis, the food structure of the “Beiqian” ancestors was reconstructed and the influence of terrestrial and marine resources on their lifestyle was discussed. Based on the δ13C and δ15N stable isotopic values of human bone collagen, the analytical results obtained through a ternary mixed model reveal that the food sources of the Beiqian ancestors included about 44.1% marine species (probably shellfish and fish), 34.1% C4 plants (possibly millet), and 21.8% land animals. These results indicate that they lived mainly from fishing and farming, supplemented by hunting or poultry raising. Compared with other sites in the same period, the stable isotope results show that 5000–6000 years ago, the lifestyles of ancestors in the Yangtze River basin, Yellow River basin, Northern coastal area and inland area were very different. The ancestors from the Yangtze River basin focused on rice farming and fishing, whereas the ancestors in the Yellow River basin farmed millet and raised animals. Those in coastal areas relied mostly on farming and marine fishing.
Co-reporter:Kai Lv, Haitao Kang, Heng Zhang, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2012 Volume 402() pp:108-116
Publication Date(Web):20 May 2012
DOI:10.1016/j.colsurfa.2012.03.032
Molecular simulation studies were performed to explore the properties of functionalized Mg–Al layered double hydroxides (LDHs). Using molecular dynamics (MD) simulations, the intercalation of photoactive dyes (methyl orange, MO) into a Mg:Al 2:1 LDH system were studied, for which some limited experimental data have been reported (J. Colloid Interface Sci. 2008, 318, 337). The interlayer structure, hydrogen bonding, and consequent swelling of LDH compounds containing MO molecules were shown on the molecular level. Quantum mechanical density functional theory was also employed in order to get the geometry optimization and atomic charges. The concentration profiles, mean square displacement (MSD), and self-diffusion coefficient were calculated using the trajectory files on the basis of MD simulations, and the results indicated that the MO molecules were much more stable when intercalated into the LDH layers. The orientation of the intercalated MO molecules was measured at the interface of the LDH layers. The tail vectors of the MO molecule were tilted with an average angle from 70° to 76°, and most of the angular distribution is about 74.15°, which had a good agreement with the experimental data 74.1°.Graphical abstractThe MD simulated equilibrium structures before and after 3 ns for the MO-LDH systems. Two different systems were researched, and the results of the MD displayed the interlayer structure and arrangement, which exhibit a certain disorder.Highlights► Two different LDH-MO systems were studied by molecular dynamic simulation. ► The concentration profiles, MSD, and self-diffusion coefficient were calculated using the trajectory files. ► The MO molecules were much more stable when intercalated into the LDH layers. ► The mechanism gives a great contribution to the design of photonic materials and chemical sensors.
Co-reporter:Congyun Zhang, Haitao Kang, Kai Lv, Hui Chen, and Shiling Yuan
Industrial & Engineering Chemistry Research 2011 Volume 50(Issue 22) pp:12521-12526
Publication Date(Web):September 29, 2011
DOI:10.1021/ie2003768
Maize leaves and sheaths are cheap agricultural byproducts that contain an abundance of amorphous hydrated silica (named phytoliths). However, there have been no attempts at utilizing the phytoliths to synthesize silica nanotubes. In this paper, we describe the morphologies and microstructures of phytoliths in leaves and sheaths of maize, and synthesize hollow silica nanotubes using the phytoliths in cetyltrimethyl ammonium bromide (CTAB) /sodium dodecyl benzene sulfonate (SDBS) surfactant system. TEM and SEM images show that the phytoliths exist in cross and dumbbell shapes in maize. The silica nanotubes obtained from the naturally deposited phytoliths exhibit special blue photoluminescence. This optical characteristic indicates that the agro-based waste materials may have potential applications in the fields of light localization and other integrated optical devices.
Co-reporter:Zhen Xu, Michael Hirtz, Shiling Yuan, Chengbu Liu, Lifeng Chi
Chemical Physics Letters 2011 Volume 507(1–3) pp:138-143
Publication Date(Web):29 April 2011
DOI:10.1016/j.cplett.2011.03.069
Abstract
A series of MD simulations were conducted towards the selective deposition of organic luminescent molecules 3(5)-(9-anthryl) pyrazole (ANP) and perylene onto different densely packed organosilane self-assembled monolayers (SAMs). Our simulations indicated that the packing density of alkyl chains on SAM may directly control the site-selective deposition of organic molecules. Additionally we propose a possible mechanism for this phenomenon, which can also explain the experimental findings of the selective deposition of organic molecules onto template structures, made of l-α-dipalmitoyl-phosphatidylcholine (DPPC) in alternating liquid expanded (LE) and liquid condensed (LC) states.
Co-reporter:Zhen Xu, Ke Song, Shi-Ling Yuan, and Cheng-Bu Liu
Langmuir 2011 Volume 27(Issue 14) pp:8611-8620
Publication Date(Web):June 3, 2011
DOI:10.1021/la201328y
Molecular dynamics simulations are used to study the micronature of the organization of water molecules on the flat surface of well-ordered self-assembled monolayers (SAMs) of 18-carbon alkanethiolate chains bound to a silicon (111) substrate. Six different headgroups (−CH3, −C═C, −OCH3, −CN, −NH2, −COOH) are used to tune the character of the surface from hydrophobic to hydrophilic, while the level of hydration is consistent on all six SAM surfaces. Quantum mechanics calculations are employed to optimize each alkyl chain of the different SAMs with one water molecule and to investigate changes in the configuration of each headgroup under hydration. We report the changes of the structure of the six SAMs with different surfaces in the presence of water, and the area of the wetted surface of each SAM, depending on the terminal group. Our results suggest that a corrugated and hydrophobic surface will be formed if the headgroups of SAM surface are not able to form H-bonds either with water molecules or between adjacent groups. In contrast, the formation of hydrogen bonds not only among polar heads but also between polar heads and water may enhance the SAM surface hydrophilicity and corrugation. We explicitly discuss the micromechanisms for the hydration of three hydrophilic SAM (CN-, NH2- and COOH-terminated) surfaces, which is helpful to superhydrophilic surface design of SAM in biomimetic materials.
Co-reporter:Hui Yan, Xin-Li Guo, Shi-Ling Yuan, and Cheng-Bu Liu
Langmuir 2011 Volume 27(Issue 10) pp:5762-5771
Publication Date(Web):April 15, 2011
DOI:10.1021/la1049869
The effect of Ca2+ ions on the hydration shell of sodium dodecyl carboxylate (SDC) and sodium dodecyl sulfonate (SDSn) monolayer at vapor/liquid interfaces was studied using molecular dynamics simulations. For each surfactant, two different surface concentrations were used to perform the simulations, and the aggregation morphologies and structural details have been reported. The results showed that the aggregation structures relate to both the surface coverage and the calcium ions. The divalent ions can screen the interaction between the polar head and Na+ ions. Thus, Ca2+ ions locate near the vapor/liquid interface to bind to the headgroup, making the aggregations much more compact via the salt bridge. The potential of mean force (PMF) between Ca2+ and the headgroups shows that the interaction is decided by a stabilizing solvent-separated minimum in the PMF. To bind to the headgroup, Ca2+ should overcome the energy barrier. Among contributions to the PMF, the major repulsive interaction was due to the rearrangement of the hydration shell after the calcium ions entered into the hydration shell of the headgroup. The PMFs between the headgroup and Ca2+ in the SDSn systems showed higher energy barriers than those in the SDC systems. This result indicated that SDSn binds the divalent ions with more difficulty compared with SDC, so the ions have a strong effect on the hydration shell of SDC. That is why sulfonate surfactants have better efficiency in salt solutions with Ca2+ ions for enhanced oil recovery.
Co-reporter:Zhen Xu, Shi-Ling Yuan, Hui Yan, Cheng-Bu Liu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2011 380(1–3) pp: 135-142
Publication Date(Web):
DOI:10.1016/j.colsurfa.2011.02.046
Co-reporter:Xinli Guo, Shiming Yuan, Shouhong Yang, Kai Lv, Shiling Yuan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2011 Volume 384(1–3) pp:212-218
Publication Date(Web):5 July 2011
DOI:10.1016/j.colsurfa.2011.03.055
Self-assembly of ABA triblock copolymer confined in concentric-spherical nanopores was studied using MesoDyn simulation. Our calculation shows that in this confined geometry a zoo of exotic structures can be formed. These structures include perforated vesicle like carbon fullerene, strip pattern and hybrid structure. Moreover, the dependence of the chain conformation on the volume fraction, the interactions between blocks and the diameter of the spherical pore are also investigated. The results of these simulations can be used to predict the amphiphilic triblock copolymer morphologies confined in concentric-spherical nanopores and should be helpful in designing polymeric nanomaterials in future.Graphical abstractHighlights► In this study, nanospheres with perforate vesicle formed by ABA triblock copolymer, like carbon fullerene, were obtained at moderate ratio of hydrophilic and hydrophobic solvent blocks. ► Their morphological patterns are related to the polymer concentration, polymer–solvent interaction parameter and the diameter of the nanospheres. ► The approach reported in this work will furnish important and useful information to experiments of amphiphilic polymer nanospheres.
Co-reporter:Shi-Ming Yuan, Hui Yan, Kai Lv, Cheng-Bu Liu, Shi-Ling Yuan
Journal of Colloid and Interface Science 2010 Volume 348(Issue 1) pp:159-166
Publication Date(Web):1 August 2010
DOI:10.1016/j.jcis.2010.04.026
A quantum mechanics (QM) method has been used to calculate molecular properties of sodium dodecylbenzenesulfonate (SDBS) in vacuum and in solution. Furthermore, molecular dynamics (MD) simulations have been used to determine the dynamic behavior of SDBS moving from the bulk solution to the air/water interface. QM calculations suggest that two head-group oxygen atoms on each surfactant molecule interact with a Na+ ion, despite the availability of three oxygen atoms in the head group. MD simulations showed that the Na+ ion must overcome the energy barrier between two solvent layers around the head group to form stable ion pair in solution, which is consistent with experimental results. In the simulation, in moving from the bulk to the interface, SDBS can aggregate in a short time, and the adsorption adopts a preferred orientation. The results indicate that formation of favorable hydrophobic interactions of the surfactant alkyl chains is the origin of interfacial adsorption of SDBS.Theoretical simulation has been used to calculate the molecular properties of a surfactant SDBS in vacuum and in aqueous solution.
Co-reporter:Hui Chen, Fen Wang, Congyun Zhang, Yuanchang Shi, Guiyun Jin, Shiling Yuan
Journal of Non-Crystalline Solids 2010 Volume 356(50–51) pp:2781-2785
Publication Date(Web):November 2010
DOI:10.1016/j.jnoncrysol.2010.09.051
In this paper, amorphous hydrated silica in Gramineae plant, named as phytoliths, was extracted and investigated from wheat straw. Porous nano-structured silica was prepared from agricultural waste materials through combustion and acid leaching. The results show that: i) the phytoliths in epidermal cells of wheat straw are round with a diameter of 14–22 μm, while those in trachea are oblong with a length of 18–40 μm and a width of 12–18 μm. These different phytoliths are all core–shell structures with the silica shell and the organism core of the plant cells; ii) The distribution of particle size, surface area, pore diameter and pore volume of nano-structured silica samples decreases with the increase of calcining temperature, and at a higher temperature, some agglomerates are formed. The results of this work are useful for scientists pursuing new synthetic route for valuable and widely applicable nanoscale silica materials, also helping to solve disposal and pollution problems.
Co-reporter:Hui Yan, Shi-Ling Yuan, Gui-Ying Xu and Cheng-Bu Liu
Langmuir 2010 Volume 26(Issue 13) pp:10448-10459
Publication Date(Web):June 15, 2010
DOI:10.1021/la100310w
The effect of Ca2+ and Mg2+ on the H-bonding structure around the headgroup of the surfactants sodium dodecyl sulfate (SDS) and sodium dodecyl sulfonate (SDSn) in solution has been studied by molecular dynamics simulation. Our results show that binding between the headgroup of the surfactant and Ca2+ or Mg2+ is prevented by a stabilizing solvent-separated minimum formed in the potential of mean force (PMF) between the interacting ion-pair. Among the contributions to the PMF, the major repulsive interaction is due to the rearrangement of the hydration shell after the ions enter into the original H-bonding structure of water around the headgroup, leading to a decrease in the number of H-bonds and an increase in their lifetimes. In the second hydration shell around the headgroup, additional water molecules are bound to the headgroup oxygen atoms either directly or bridged by Ca2+ and Mg2+. The PMF shows that the energy barriers to ion-pairing between the headgroup and Ca2+ and Mg2+ in the SDSn system are higher than those in the SDS system, and the water coordination numbers for Ca2+ or Mg2+ in SDS solution are lower. This result indicates that SDS binds the ions easily compared with SDSn, and the ions have a strong effect on the original hydration structure. That is why sulfonate surfactants such as SDSn have better efficiency in salt solution with Ca2+ and Mg2+ for enhanced oil recovery.
Co-reporter:Shou-Hong Yang;Yuen-Kit Cheng;Shi-Ling Yuan
Journal of Molecular Modeling 2010 Volume 16( Issue 12) pp:1819-1824
Publication Date(Web):2010 December
DOI:10.1007/s00894-010-0673-0
Self-assembly of AB diblock copolymer confined in concentric-cylindrical nanopores was studied using MesoDyn simulation. Our calculation shows that in this confined geometry a zoo of exotic structures can be formed. These structures include bicontinuous phases like carbon nanotube, imperfect single helixes and double helixes. Moreover, the dependence of the chain conformation on the volume fraction, concentration, the interactions between blocks and the diameter of the cylindrical pore are investigated. The results of these simulations can be used to predict the diblock copolymer morphologies confined in concentric-cylindrical nanopores and should be helpful in designing polymeric nanomaterials in the future.
Co-reporter:Shouhong Yang;Xiuqing Zhang;Shiling Yuan
Journal of Molecular Modeling 2008 Volume 14( Issue 7) pp:607-620
Publication Date(Web):2008/07/01
DOI:10.1007/s00894-008-0319-7
The microphase separation dynamics of the triblock copolymer surfactant P103 [(ethylene oxide)17(propylene oxide)60(ethylene oxide)17] was investigated by a dynamic variant of mean-field density functional theory. Different self-assembled aggregates, spherical micelles, micellar clusters and disk-like micelles, are explored in the solution. The spherical micelle above critical micelle concentration (CMC) is a dense core consisting mainly of PPO and a hydrated PEO swollen corona, and is in good agreement with the experimental results concerning their structures. At a concentration of 10–15%, micellar clusters with a larger PPO core form as a result of coalescence among spherical micelles. At concentrations above 16% by volume, a series of disk-like micelles come into being. The order parameters show that spherical micelles are easily formed, while the micellar clusters or disk-like micelles need a longer time to reach steady equilibrium. The results show that mesoscopic simulation can augment experimental results on amphiphilic polymers, and provide some mesoscopic information at the mesoscale level.
Co-reporter:Shouhong Yang, Shiling Yuan, Xiuqing Zhang, Yijing Yan
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2008 Volume 322(1–3) pp:87-96
Publication Date(Web):5 June 2008
DOI:10.1016/j.colsurfa.2008.02.029
The microphase separation dynamics of tri-block copolymers Pluronic EO17PO60EO17 (P103), EO19PO43EO19 (P84) and EO19PO29EO19 (P65) was simulated in aqueous solution by a dynamic variant of mean-field density functional theory for Gaussian chains. For a Pluronic copolymer with smaller ratio of poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) (P103, P84 and P65) at low concentration, with an increase of the concentration, the micellar phases change from spherical micelles and micellar clusters, to disk-like micelles for the P103 and P84 solutions, and from spherical micelles to worm-like micelles for the P65 solution. In the P103 and P84 systems, the spherical micelles and micellar clusters can be divided clearly by order parameter, and in the P65 solution the phase separation of worm-like micelle with simulation time is shown clearly by the 3D density field of the PO block. With a decrease of the ratio of hydrophobic PPO and PEO (from P103, P84 to P65), the critical micellar concentration (cmc) increases. It was found that the cmc were 4 vol.% for P103, 7 vol.% for P84 and 43 vol.% for P65. It was concluded that mesoscopic simulation can be considered as an adjunct to experimentation and can provide mesoscopic information otherwise inaccessible (or, not easily accessible) from experimentation.
Co-reporter:Haihui Jiang, Shiling Yuan, Gang Liu, Qilong Wang
Chemical Physics Letters 2007 Volume 438(1–3) pp:53-58
Publication Date(Web):11 April 2007
DOI:10.1016/j.cplett.2007.02.049
A study on mechanisms of radical initiated surface chain reaction of ethylene molecule on the H-terminated Si(1 1 1) has been carried out by using density functional theory and ab initio molecular dynamic methods. On Si(1 1 1) surface, one of the crucial steps of the surface chain reaction, namely, the abstraction of a H atom from a nearby surface hydride unit, is found to have a somewhat smaller activation energy from the nearest silicon site than from the next nearest silicon site. Ab initio molecular dynamics shows that the H-abstraction on Si(1 1 1) surface is very easy to be obtained from the transition state.A study on mechanisms of radical initiated surface chain reaction of ethylene molecule on the H-terminated Si(1 1 1) has been carried out, and the abstraction of a H atom from a nearby surface hydride unit is found to have a somewhat smaller activation energy from the nearest silicon site.
Co-reporter:Xiuqing Zhang, Shiling Yuan, Guiying Xu, Chengbu Liu
Acta Physico-Chimica Sinica 2007 Volume 23(Issue 2) pp:139-144
Publication Date(Web):February 2007
DOI:10.1016/S1872-1508(07)60011-4
The microphase separation dynamics of triblock copolymer surfactant [(ethylene oxide)27(propylene oxide)61(ethylene oxide)27] (P104) in aqueous solution was simulated by a dynamic variant of mean-field density functional theory for Gaussian chains. Different morphologies depending on the simulation concentration and time were shown in low concentration (ϕ<35%). With the increase of the concentration, the self-assemble aggregates changed from spherical micelles, micellar clusters, to disk-like micelles. (1) In the spherical micellar region (5%–10%, ϕ), the result of the simulation was similar to that of the experiment in that micelle was a dense core consisting mainly of PPO and a hydrated PEO swollen corona. (2) Due to the coalescence among spherical micelles, larger micellar clusters are formed in a concentration ranging from 11% to 15% (ϕ). (3) Owing to the attractions between the PEO coronas of micellar clusters, series of disk-like micelles were found above the concentration 16% (ϕ). The order parameters showed that the phase separation of spherical micelles was easily formed, while the micellar cluster or disk-like micelles required a longer time to acquire a steady equilibrium.
Co-reporter:Shi-Ling Yuan, Yan Zhang, Yan Li
Chemical Physics Letters 2004 Volume 389(1–3) pp:155-159
Publication Date(Web):1 May 2004
DOI:10.1016/j.cplett.2004.03.095
Abstract
The structure of alkyl monolayers on the H-terminated Si(1 1 1) surface under the external electric field was investigated by molecular simulation method. Molecular mechanic calculations showed that the energy per alkyl chain reduces linearly with increasing of carbon number in alkyl chains from two-carbon to eighteen-carbon. When the external electric field was added between the optimized alkyl chains, the calculated energy per chain is coincident with the experimental current density after alkyl-modified silicon crystal was considered as the semiconductor. The conclusion is that molecular simulation can provide other information and be considered as an adjunct for the experiments from another investigation way.
Co-reporter:Shiling Yuan, Yan Zhang, Yan Li, Guiying Xu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2004 Volume 242(1–3) pp:129-135
Publication Date(Web):2 August 2004
DOI:10.1016/j.colsurfa.2004.03.031
The morphology of alkyl monolayers on the H-terminated Si(1 1 1) surface was investigated by molecular simulation method. Molecular mechanics calculations showed that the energy per alkyl chain decreases linearly with the increase of carbon number in eighteen-carbonit from C2 to C18. And the densely packed, well-ordered monolayer on Si(1 1 1) surface can be shown using energy Minimizer method. When the structure of the ester, hydroxide, carboxyl, amine and alkyl–terminated Si surface monolayers on the H–terminated Si(1 1 1) surface was investigated, we found that the H-bonding and steric effect play important roles in the formation process of monolayers on Si(1 1 1) surfaces. And the orderliness of the monolayers is related to the tilt angle of single chain on Si(1 1 1) surface. The conclusion is that molecular simulation can provide useful information and be considered as an adjunct for the experiments at the molecular level.
Co-reporter:Shi-Ling Yuan, Zheng-Ting Cai and Yuan-Sheng Jiang
New Journal of Chemistry 2003 vol. 27(Issue 3) pp:626-633
Publication Date(Web):24 Jan 2003
DOI:10.1039/B207998D
The structure of eight-carbon monolayers on the H-terminated Si(111) surface was investigated by a molecular simulation method. Molecular mechanics calculations showed that the best substitution percentages on the Si(111) surface were 50% for octene or octyne-derived monolayers and 40% for the styrene or phenylacetylene-derived monolayers. These values are in good agreement with the experimental results. After a two-dimensional cell containing alkyl chains and four layers of Si atoms was constructed, the densely packed and well-ordered monolayer on the Si(111) surface can be shown at the molecular level. At the same time, the thickness of the monolayers and the tilt angle of the alkyl chain were also calculated. Additionally, the theoretical calculations showed that the CC bond of the alkyne only reacts once with the H-terminated Si(111) surface, that is only one Si–C bond per organic molecule is formed on the Si(111) surface, which verifies the experimental results. It is thus shown that molecular simulation can provide otherwise inaccessible microscopic information at the molecular level, and may be considered as a useful adjunct to experiments.
Co-reporter:Yuan Shi-Ling;Cai Zheng-Ting;Xu Gui-Ying
Chinese Journal of Chemistry 2003 Volume 21(Issue 2) pp:
Publication Date(Web):26 AUG 2010
DOI:10.1002/cjoc.20030210205
The aggregates in sodium dedecylsulphate (SDS)/dimethylbenzene/water systems have been investigated using dissipative particles dynamic (DPD) simulation method. Through analyzing three-dimensional structures of aggregates, three simulated results are found. One is the phase separation, which is clearly observed by water density and the aggregates in the simulated cell; another is the water morphology in reverse micelle, which can be found through the isodensity slice of water including bound water, trapped water and bulky water; the third is about the water/oil interface, i. e., ionic surfactant molecules, SDS, prefer to exist in the interface between water and oil phase at the low concentration.
Co-reporter:Shi-Ling Yuan, Zheng-Ting Cai, Gui-Ying Xu, Yuan-Sheng Jiang
Chemical Physics Letters 2002 Volume 365(3–4) pp:347-353
Publication Date(Web):15 October 2002
DOI:10.1016/S0009-2614(02)01494-X
A simple model, i.e., sodium bis(2-ethylhexyl) sulfosuccinate (AOT) represented by one-head and two-tail beads tied together by a harmonic spring and water or iso-octane by one bead, was put forward via dissipative particles dynamics (DPD) simulation method. Using the changes of interfacial tension between water and oil phase, a ternary phase diagram of AOT/water/iso-octane system was drawn.
Co-reporter:Hai Tao Kang, Kai Lv, Shi Ling Yuan
Applied Clay Science (February 2013) Volume 72() pp:184-190
Publication Date(Web):February 2013
DOI:10.1016/j.clay.2013.01.015
Co-reporter:Fengfeng Gao, Hui Yan, Qiwei Wang and Shiling Yuan
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 32) pp:NaN17237-17237
Publication Date(Web):2014/06/17
DOI:10.1039/C4CP02038C
In enhanced oil recovery (EOR), the micro-oil droplet heavily affected the stability of foam and prevented foam flooding. In this paper, the oil bridge-stretching mechanism of foam rupture was described through molecular dynamics with the aim of providing supplements to the experiments at the molecular level. Two important phenomena for foam rupture have been pointed out by the simulation. One is about the pseudoemulsion film, representing the stability of the oil–water–air three phase interface. The bound water connecting the headgroups of the surfactant through strong H-bonding interactions played a vital role in the stability of the pseudoemulsion film. These water molecules could hinder the disappearance of the water phase in the pseudoemulsion film. The additional energy barrier, which was influenced by the surfactant concentration, also played a vital role in preventing the destruction process. The other factor is about the oil bridge, which appeared after the destruction of the pseudoemulsion film. The external horizontal force stretched the bridge resulting in the destruction of the bridge. The process was decided by the properties of the oil molecules. In the simulation, the stretching force was divided into three stages including the initial increasing force, the middle equilibrium force and the final decreasing force. Especially the second equilibrium force, which stretched the middle of the oil bridge so that it became thin, was vital to the foam rupture. The concentration and properties of the oil molecules were the crucial factors for foam rupture. The simulated results offer important supplements to experiments.
Co-reporter:Lin Wang, Xia Xin, Mengzhou Yang, Xin Ma, Zhenyu Feng, Rui Chen, Jinglin Shen and Shiling Yuan
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 38) pp:NaN20940-20940
Publication Date(Web):2014/08/22
DOI:10.1039/C4CP02634A
Two kinds of carbon materials, i.e., graphene and graphene oxide (GO), were successfully incorporated into a lyotropic liquid crystal (LLC) matrix formed by n-dodecyl tetraethylene monoether (C12E4). The properties of graphene–C12E4 and GO–C12E4 LLC composites were characterized by UV-vis absorption, transmission electron microscopy (TEM) observations, polarized optical microscopy (POM) observations, small-angle X-ray scattering (SAXS) and rheological measurements. SAXS results indicate that both graphene and GO are well-dispersed in the C12E4 LLC matrix and some interactions occur between the C12E4 LLC matrix and graphene (or GO) sheets. Moreover, it is demonstrated that graphene interacts with the hydrophobic part of C12E4 LLC while GO mainly interacts with the hydrophilic part of C12E4 LLC because of the different properties of graphene and GO. Integration of graphene and GO into C12E4–PEG systems by a spontaneous phase separation method reveals the different interaction mechanisms of graphene and GO with C12E4 LLC. It can be concluded that the mechanical and electrical properties of the C12E4 LLC have been largely improved by the incorporation of graphene and GO, which opens the door for wide applications in nanotechnology, electrochemical and biochemical areas.
Co-reporter:Guokui Liu, Heng Zhang, Gang Liu, Shiling Yuan and Chengbu Liu
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 2) pp:NaN885-885
Publication Date(Web):2015/11/19
DOI:10.1039/C5CP05639J
All-atom molecular dynamics (MD) simulations were performed to study the effects of different tetraalkylammonium (TAA+) counterions, including tetramethylammonium (TMA+), tetraethylammonium (TEA+), tetrapropylammonium (TPA+) and tetrabutylammonium (TBA+), on dodecyl sulfate (DS−) micelles. Structural properties, such as the radius of gyration (Rg), micelle radius (Rs), micelle size, solvent accessible surface area (SASA), carbon and sulfur distribution, hydration numbers, and distribution of polar heads on the micelle surface, were investigated. The simulation results show that the longer the carbon chains of the TAA+ counterion, the greater the radius of the micelle formed. TMA+ leads to the most compact structure of the DS− micelle among the five studied systems and DS− and TAA+ formed mixed-micelles. There are mainly four interaction patterns between TAA+ and DS− ions, and the pattern in which two alkyl chains of the TAA+ ion penetrate into the DS− micelle is the most favorable one. Based on the preceding analysis, a model based on this MD method is proposed.
Co-reporter:Guokui Liu, Yaoyao Wei, Fengfeng Gao, Shiling Yuan and Chengbu Liu
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 16) pp:NaN11361-11361
Publication Date(Web):2016/03/24
DOI:10.1039/C6CP01042C
The micellization of amphiphilic molecules is an important phenomenon in the natural world. However, the origin of entropy change during micellization is still unclear. Molecular dynamics simulation was applied to study configurational entropy change of amphiphilic molecules in micellization. The entropy change of polar heads, hydrophobic chains, vibration, translation and rotation are discussed. Analyses provide a clear physical picture of the entropy increase in micellization, and thus foundations for further study.
Co-reporter:Shi-Ling Yuan ; Xiu-Qing Zhang ;Kwong-Yu Chan
Langmuir () pp:
Publication Date(Web):January 22, 2009
DOI:10.1021/la8035133
Mesoscale simulation was performed to investigate the dynamical structural behavior of the pluronic P123 block copolymer in the synthesis of mesoporous SBA-15. Shear is introduced to represent stirring in the actual experiment, and a weak charge is included to simulate the acidic conditions in the synthesis. Under shear, with the increase in weak charge in the PEO [poly(ethylene oxide)] block, the template forms more ordered hexagonal phases, and the pore sizes of the cylindrical hydrophobic PPO [poly(propylene oxide)] blocks decrease. The structural factor shows three types of water molecules in the mesoscale aggregates, including bulk water in the solution, bound water around the hydrophilic PEO corona, and trapped water in the hydrophobic PPO core. When 1,3,5-trimethyl-benzene (TMB) is added to the system as a swelling agent, expanded hexagonal phases are formed, and the density mapping of TMB shows that the TMB molecules are mainly located in the hydrophobic PPO cores. In configurations with spherical micelles, although bimodally dispersed spheres are observed, the face-centered cubic (fcc) packing of the micelles hardly changes with the addition of TMB. In agreement with experimental results, the simulations show that the shear and the weak charge are essential to the formation of hexagonal templates in the copolymer. Mesoscopic simulations complement experimental investigations on the morphology changes of amphiphilic polymer in template syntheses and can provide important guidance for further experiments.
Co-reporter:Lin Wang, Xia Xin, Kai Guo, Mengzhou Yang, Xin Ma, Jing Yuan, Jinglin Shen and Shiling Yuan
Physical Chemistry Chemical Physics 2014 - vol. 16(Issue 28) pp:NaN14780-14780
Publication Date(Web):2014/04/29
DOI:10.1039/C4CP00622D
Carbon nanotubes (CNTs) were incorporated into a lyotropic liquid crystal (LLC) matrix at room temperature through spontaneous phase separation. The phase separation process occurred in n-dodecyl tetraethylene monoether (C12E4) solutions induced by the hydrophilic polymer, poly(ethylene glycol) (PEG). It was found that the molecular weight of PEG has a significant effect on the CNTs–C12E4 system, which not only influences the phase behavior of the system but also changes the properties of the CNTs–LLC composites. Polarized optical microscopy (POM) images, combined with small-angle X-ray scattering (SAXS) results, indicate that CNTs incorporate within the layers of the lamellar LLCs without destroying the structure of LLCs. Moreover, UV-vis absorption, Raman spectra and rheological measurements were performed to investigate the characteristic properties of the CNTs–LLC composites. This study not only gives a more comprehensive understanding of polymer-induced phase separation, but also expands the potential uses of CNTs–LLC composites in nanotechnology.
![1-Propanaminium, N,N-dimethyl-N-[2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl]-3-sulfo-, inner salt, homopolymer](/data/chemimg/3779600/41488-70-4.png)
![1-Propanaminium, N,N-dimethyl-N-[2-[(2-methyl-1-oxo-2-propen-1-yl)oxy]ethyl]-3-sulfo-, inner salt, homopolymer](/data/chemimg/3779600/41488-70-4_b.png)
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