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Abundant pH and UV light stimuli-responsive behaviors of Gemini surfactant 12-3(OH)-12·2Br− and trans-ortho-hydroxyl cinnamic acid in aqueous solution.

The presence of a highly alkaline environment or large amounts of Ca2+ in concrete exerts a great influence on the dispersion of graphene oxide (GO) particles. Therefore, the development of a highly efficient GO dispersant to adapt to complex concrete environments is important. In this work, novel phosphate-modified small molecular polydentate polymers were synthesized and used as efficient dispersants for cement and high-concentration GO solutions. The chemical structure of the polymers was confirmed by 1H NMR and IR spectroscopy, and the effect of adsorption groups on the adsorption ability of polymers was studied by using adsorption experiments and theoretical calculations. Results showed that the dispersant inositol hexaphosphate–methoxy polyether (IHP-MP) features a high adsorption equilibrium constant and strong adsorption ability. IHP-MP exhibited not only good water-reducing and slump-retaining properties but also remarkable cement hydration-retarding effects due to its numerous phosphate groups. IHP-MP could be used as an auxiliary GO dispersant with the comb polymer PCE to effectively reduce the viscosity and improve the stability of GO solutions. SEM, TGA and IR characterization indicated that IHP-MP strongly interacts with the surface groups of GO particles.

The alkylimidazolium tetrafluoroborate ionic liquids (ILs) ([Cnmim][BF4] n = 2, 4, 6, 8, 10) and anionic surfactant sodium dodecyl sulfate (SDS) were combined together to produce effective mediums for chromogenic catalysis of tetramethylbenzidine (TMB) with horseradish peroxidase (HRP) in the presence of H2O2. The chromogenic performance, kinetic behavior, and the possible influencing mechanism for the chromogenic catalysis of HRP-H2O2-TMB were discussed in detail. Therein, the roles of ionic liquids (ILs) were highlighted by the combination of experiments and theoretical calculations. The SDS/[C4mim][BF4] combination displayed superiority in chromogenic catalysis by improving both the substrate solubility and product stability to the maximum extent possible. Furthermore, SDS/[C4mim][BF4] combination showed uniqueness for TMB in improving the chromogenic performance compared with other chromogenic substrates of HRP. Inspired by the efficient chromogenic system, an enhanced enzyme-linked immunosorbent assa...

In this work, four types of comb-like dispersants and one linear dispersant were synthesized to explore the effect of dispersant structure on the bubble structure in water solution and mortar system for the first time. Dispersants were modified with different adsorption groups (i.e., carboxylic acid, phosphate ester, and sulfonic groups). Polymer structures were identified using gel permeation chromatography and infrared spectroscopy. Surface tension test indicated that the comb-like dispersants exhibited lower surface tension than that of the linear dispersants (NSF-2), thereby demonstrating that the polycarboxylate superplasticizer (PCE) solutions possessed high surface activity. The analysis of the foamability and foam stability of the comb-like and linear dispersants were comprehensively investigated at different concentrations. Comb-like dispersants possessed higher foam height and better foamability performance than those of the linear dispersants. The bubbles of the dispersant PCE-3 were smaller in terms of the mean area and possessed higher number of bubbles than those of the other dispersants, which may be essential in reducing the viscosity of the slurry. A similar result was also obtained in the mortar system tested using the AVA instrument for PCE-3 and NSF-2. Adsorption and rheological behavior test indicated that comb-like dispersant PCE-3 is the most effective in reducing the viscosity of the slurry among all the dispersants tested. This result is consistent with that of the foamability experiment.

Machine learning (ML) methods were applied to predict the capacitance of carbon-based supercapacitors. Hundreds of published experimental datasets are collected for training ML models to identify the relative importance of seven electrode features. This present method could be used to predict and screen better carbon electrode materials.

A new lubricating coating with functionalized graphene oxide (fGO) consisting of graphene oxide (GO) with different oxidation degrees, n-octylamine basal plane functionalized GO (bGO), and edge functionalized GO (eGO) was developed with or without 3-aminopropyltrimethoxysilane (APTMS) to reduce friction in macroscale contact with water. The optimal preparation condition of the coating was obtained by the single factor evaluation of a series of factors (20 % APTMS aqueous solution, 12 h immersion time, 0.05 mg/mL GO aqueous solution, and 100 °C curing temperature). The effect of the oxidation degree and functionalization of GO on the friction-reducing and anti-wear behavior of the coating was explored. The coatings with a higher GO oxidation degree exhibited better friction-reduction and anti-wear performance. In addition, the friction-reducing capability of the APTMS-bGO coating was greater than that of APTMS-eGO.

The interaction between star-shaped copolymer poly(2-(dimethylamino)ethyl methacrylate-b-2-(2-methoxyethoxy)ethyl methacrylate) (CDPDPM) and anionic surfactant sodium dodecyl sulfate (SDS) in aqueous solutions are investigated by using fluorescence and dynamic light scattering (DLS) techniques. The effects of nonionic surfactant dodecyl β-D-maltopyranoside (C12G2) and salts including inorganic salt ammonium bromide (NH4Br) and organic salt tetra-n-butylammonium bromide (Bu4NBr) on the interaction between CDPDPM and SDS have been explored systematically. The results have suggested that SDS molecules can bind on CDPDPM by electrostatic interaction between the positively charged CDPDPM and negatively charged SDS and thus weaken the binding ability of CDPDPM to water molecules. CDPDPM exhibits temperature-responsive aggregation behavior in aqueous solution gradually with the increase of SDS concentration and the lower critical solution temperature (LCST) decreases correspondingly. The introduction of nonionic surfactant C12G2 changes the interaction between CDPDPM and SDS significantly by participate the formation of complexes and the stability of the CDPDPM/SDS complexes declines leading to the chance of forming larger complexes is deprived at higher temperature. The addition of NH4Br to the CDPDPM/SDS system can retard the binding of SDS on the polymer chains because of electrostatic shielding. Correspondingly, LCST is higher and the formed aggregates are smaller. For CDPDPM/Bu4NBr/SDS system, the phenomenon is similar to that of the CDPDPM/C12G2/SDS system. This should be attributed to the nature of Bu4N+, possesses not only positive charges but also certain hydrophobicity, and thus Bu4N+ has the ability to participate and facilitate the formation of SDS micelles. Obviously, the LCST of the mixed system can be tailored by adjusting the system composition on purpose.

The gelation behavior and properties of sodium deoxycholate (NaDC) and L-aspartic acid (Asp) in aqueous solution were investigated in detail at 25 °C. The linear polymer poly(2-(2-methoxyethoxy)ethyl methacrylate-co-oligo-(ethylene glycol) methacrylate) (P(MEO2MA90-co-OEGMA10)) and star-shaped polymer poly(2-(dimethylamino)ethyl methacrylate-b-2-(2-methoxyethoxy)ethyl methacrylate) (CDPDPM) were introduced in NaDC/Asp hydrogels for exploring the effects of polymers on the properties of NaDC/Asp hydrogels and the mechanism underlying gelation processes by polymers was proposed. The hydrogels were characterized by phase behavior observation, polarized optical microscopy (POM), cryogenic scanning electron microscopy (cryo-SEM), X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and rheological measurements. Moreover, the adsorption performances of hydrogels with and without polymers to methylene blue (MB) were studied using a UV-vis spectrometer. The results indicated that the transition from sol to gel state was observed with an increase in the Asp concentration in the system. Both linear and star-shaped polymers can participate in the formation of a gel network structure, so that the density of network structure and the mechanical strength of hydrogels increased. Furthermore, it was found that the viscoelasticity of the CDPDPM-containing hydrogel was much higher than that of the P(MEO2MA90-co-OEGMA10)-containing hydrogel under the same condition, indicating that CDPDPM performed better in strengthening the network structure of the hydrogels than P(MEO2MA90-co-OEGMA10) due to the special structure that provided more binding sites for hydrogen bonding and stronger hydrophobicity that inhibited the swelling and dissolution of hydrogels. On coming in contact with the MB solution, the CDPDPM-containing hydrogel can adsorb MB and maintain the hydrogel state for recycling. On the contrary, the NaDC/Asp hydrogel dissolved and P(MEO2MA90-co-OEGMA10)-containing hydrogel collapsed in the MB solution. The properties of the hydrogels are expected to be tailored by introducing polymers with different properties, including the charge numbers, the number of available binding sites, and hydrophobic properties.

MoS2 coating is an effective way to suppress the growth of lithium dendrites, but the study of the layer spacing effect is still lacking. In this work, the diffusion and adsorption of lithium ions on the MoS2 were studied by multiscale simulations. The transport of lithium ions on the MoS2 was investigated by a continuum method, which shows that the smaller layer spacing of 1 nm can enhance the ion diffusion. The QDFT method was used to study the lithium ions transport on 1T- and 2H- MoS2 with layer spacing of 0.65 nm - 1.15 nm. Results indicate that lithium dendrites are more difficult to grow on 2H- MoS2. For both types of MoS2, enlarged layer spacing can reduce lithium dendrites growth and 0.75 nm is the most suitable interlayer distance for MoS2 expanding. We hope our results can provide guidance to the synthesis of dendrite-free lithium metal batteries.

The principal problem in the area of drug delivery is achieving better selectivity and controllability. A new core–shell nanoparticle composite (denoted MSN@Tf@Polymer) with dual-pH-sensitivity has been prepared as a drug carrier for intracellular drug delivery and release. MSN@Tf@Polymer consists of mesoporous silica nanoparticles (MSN), green-transferrin (Tf) and diblock copolymer (poly-2-diisopropylamino ethylmethacrylate-b-methoxy-poly ethyleneglycol: mPEG45-PDPAn). The core–shell structure is self-assembled layer by layer. Results show that nearly 80% doxorubicin hydrochloride (DOX) loaded in MSN@Tf@Polymer could be released in 5 h at pH 5.0, which is an improvement from the results obtained at pH 6.5 and pH 7.4. MTT assay and fluorescence inversion microscope experiments indicate that MSN@Tf is successfully taken up by liver cancer cells (Huh7) without apparent cytotoxicity, and Tf has strong intensity of fluorescence for subcellular localization. Confocal laser scanning microscopy (CLSM) experiments indicate that MSN@Tf@Polymer is able to enter the lysosome of the tumor cells. Furthermore, cell apoptosis experiments prove that DOX loaded in MSN@Tf@Polymer has the best anti-tumor effect compared with free DOX and DOX in bare MSN. MSN@Tf@Polymer has high biocompatibility, enhanced drug loading, site-specific delivery and in situ stimulus release and will also hopefully be applied as an intracellular drug delivery system.

One growing issue is how to use the weakly acidic conditions in endosomes/lysosomes for designing highly pH-sensitive drug carriers to deliver chemotherapeutic drugs accurately. In this paper, pH-sensitive amphiphilic triblock copolymers PEG8-PDPAn-PEG8 (n = 30, 50 and 100) were synthesized. Micelles composed of the copolymers were found to enter into lysosomes using a lysosome tracker method. The pH-sensitivity makes the micelles stable at pH 7.4 but swell and become looser at pH 6.0 due to protonation. Then, doxorubicin (DOX) was efficiently encapsulated in the hydrophobic cores of the micelles and released continuously in a weakly acidic environment. Cell toxicity assays were carried out using 2 human cell lines (HEK293 and Huh7) and showed good cyto-compatibility. In vitro cell viability tests proved that the DOX-loaded micelles could be more efficiently taken up by Huh7 tumor cells than free DOX, as well as actively trigger intracellular DOX release. Furthermore, in addition to small molecules (DOX), the copolymer micelles could also deliver macromolecules (such as transferrin, which could not enter into cells by itself) into lysosomes/endosomes. These nontoxic and multifunctional micelles can serve as a promising treatment candidate for efficient intracellular drug delivery and real-time monitoring.

Photo-responsive materials with adjustable self-assembly morphologies and tunable rheological properties have attracted widespread interests of researchers in recent years because of their potential applications in controlled release, microfluidics, sensors, and so forth. In this paper, a series of UV-sensitive anisotropic fluids were prepared by combining trans-ortho-methoxycinnamate (trans-OMCA, in its salts form) and cationic Gemini surfactant propanediyl-α, ω-bis (N-dodecyl-N, N-dimethylammonium bromide) (12-3-12·2Br−) based on the research of self-assembly behaviors of the mixed system. The photo-responsive behaviors of anisotropic fluid formed in 12-3-12·2Br−/trans-OMCA/H2O system including macroscopic phase transition, microstructure transformation, rheological property, molecular interaction and isomerization degree of trans-OMCA were investigated by various techniques including UV-vis spectrum, rheology measurement, 1H NMR and 2D NOESY spectrum, transmission electron microscopy (TEM), polarized optical microscopy (POM), and dynamic light scattering (DLS). It is proved that upon exposure to UV-light, ortho-methoxycinnamate (OMCA) undergoes a photo-isomerization from trans form to cis form, which results in geometry transitions of the 12-3-12·2Br−/OMCA aggregates accompanied by a continuous phase separation and combination macroscopically; both proportion and concentration of OMCA in anisotropic solution have great influences on the photo-responsive behaviors of the system including the durations of UV irradiation and isomerization degrees of OMCA at the phase transition points. The photo-responsiveness of this smart fluids and the quantitative analysis are expected to provide reference for academic research or practical application in the fields of biomedicine, soft matters, food engineering and sunscreen.

Air pollution has become increasingly serious. Fine particulate matter (PM2.5) is the most well-known air pollutant, which leads to some common respiratory diseases when inhaled into the lungs to certain concentration. However, there is a lack of research on the process of dynamically monitoring the real-time effect of nanoparticles on the pulmonary surfactant monolayer. In this study, the DPPC/DPPG monolayer is prepared by the Langmuir method to simulate the lung surfactant monolayer during respiration and the carbon nanoparticles are introduced to the monolayer under different surface pressures to simulate the real dynamic process of inhaling nanoparticles during breathing. The effect of carbon nanoparticles on the surface behavior of DPPC/DPPG monolayer in real-time was examined in details by a combination of surface pressure (π)-area (A) isotherms, compressibility modulus (Cs-1)-surface pressure (π) isotherms and the Brewster angle microscopy (BAM). The results have shown that the introduction of carbon nanoparticles under different surface pressures affects the properties of lipid monolayers. The added carbon nanoparticles under lower surface pressure are easy to penetrate the lipid molecules to inhibit monolayer phase transition. When the carbon nanoparticles are introduced to the monolayer under higher surface pressure, they tend to self-aggregate to reduce the monolayer stability rather than interact with lipid tail chains. This work not only confirms the exotic hydrophobic carbon nanoparticles retain in the DPPC/DPPG monolayer irreversibly and affect the surface behavior of monolayer during respiration, but also opens a new idea for real-time monitoring of the effects of PM2.5 on lung health.

Oxygen-containing functional groups have strong effect on the electrochemical capacitive behavior of carbon electrodes and have been subjected to many experimental investigations. However, there are relatively few theoretical reports on the relation between the oxygen-containing functional groups and the capacitance of carbon supercapacitors. In this study, we present a simple molecular model to describe electric double layer (EDL) in the presence of Faradaic reactions. We find that electrodes modified with oxygen functional groups increase the Faradaic capacitance but have relatively little influence on the EDL capacitance. The theoretical predictions agree quantitatively with experimental observations. We hope that this joint model by combining quantum DFT and classical DFT could provide a theoretical routine to study pseudocapacitors.

The structure and number of air-voids in concrete can greatly affect the macroscopic performance of concrete. Therefore, the development of highly efficient concrete air content regulators, such as air-entraining agents or defoamers, is important. In this work, one novel block phenyloxy polyether with different propylene oxide (PO) units was successfully synthesized, and this kind of surfactants could be used as air-entraining agents or defoamers by controlling the ratio and position of PO in the polymer structure. The structures of these surfactants were verified by 1H NMR and infrared spectroscopy. Results of foamability and foam stability tests of these surfactants in water solutions indicated that the position and ratios of PO in the polymer structure have a remarkable effect on the foam properties of the surfactants. When these surfactants were applied to cement mortar, surfactant S4 with PO units adjacent to benzene ring group exhibited excellent air entrainment performance, whereas surfactants S8 and S9 with PO units at the end of the polymer showed obvious defoaming ability. The surface activity, adsorption and rheological properties were also tested to understand this type of surfactants. The results of concrete application and mechanism study showed that this type of surfactant had great potential for practical application.

The moisturizing and frictional interactions between emulsion and skin have a significant influence on the moisturizing efficacy and sensory properties of cosmetics. To deeply understand the interactions, we developed a kind of wax emulsion with liquid crystal structure and studied their interactions with dry, semi-moist and fully-moist skin. The moisturizing interaction was studied by using skin hydration test and tape stripping analysis, and it was found that with the increasing of liquid crystal content in the emulsion, the skin hydration level increased, desquamation index decreased and number of cutaneous lines increased, suggesting the increased moisturizing effect and barrier function. The frictional interaction was studied by finger friction test, and it was found that firstly during and after the application of emulsion on skin, the frictional interaction followed the stribeck-curve rule of lubrication. Secondly, when changing the water content of the substrate skin, the frictional behavior of the whole system showed a bell-curve behavior. Both skin hydration and water amount in the interfacial film played role in the frictional interaction between emulsion and skin, and the frictional interaction mechanism between wax emulsion and finger skin with different type of skin was proposed. This was the first time to study and discuss the effect of skin moist status on the moisturizing and frictional interactions between cosmetic emulsion and skin. The findings were significant for the design of high quality personal care products.

Photoresponsive micellar systems with adjustable aggregate morphologies and rheological properties may be useful in a number of fields such as in microfluidics, controlled release, and sensors. However, the complexity and great difficulty of synthesising photosensitive molecules hamper their practical applications to a significant degree. In this study, we constructed a novel photoinduced self-assembly system by introducing the photoresponsive derivative trans-2-methoxy-cinnamate (trans-OMCA) into the gemini surfactant N,N′-bis(dodecyldimethyl)-1,2-ethane diammonium dibromide (12-2-12·2Br−) solutions. The system displays abundant phase behaviors, and the long worm-like micelles, vesicles, as well as an aqueous two-phase system (ATPS) are observed in the 12-2-12·2Br−/trans-OMCA mixed system even at lower surfactant concentrations. The UV-responsive behavior of the formed vesicles and the worm-like micelles is investigated systematically. The results have shown that OMCA undergoes photoisomerization from the trans-form to the cis-form through UV light irradiation that alters the molecular packing at the micellar interface and thus leads to the transformation of micellar morphologies. The long worm-like micelles will turn into much shorter units when the sample is exposed to 365 nm UV light accompanied by a decrease in solution viscosity by more than an order of magnitude. The formed vesicle system, however, can be utilized to generate a multi-state self-assembly structure, including a worm-like micelle and a small spherical micelle, depending on the UV irradiation time. The morphologies of micelles in a 12-2-12·2Br−/trans-OMCA mixed system can be tailored by adjusting the system composition and the duration of UV light irradiation. Correspondingly, the rheological behavior of the 12-2-12·2Br−/trans-OMCA mixed system can be purposely tuned. The light-induced system with abundant self-assembly behaviors and tunable rheological properties would widen the potential application of gemini surfactants in drug delivery, smart fluids, and materials science.

The effect of chitin nanoparticles on surface behavior of lipid systems containing dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) is studied by surface pressure (π)-area (A) isotherms, polarization-modulation infrared reflection absorption spectroscopy (PM-IRRAS), Brewster angle microscopy (BAM). The variation of surface behavior of DPPC/DPPG monolayers is induced mainly by electrostatic interactions between nanoparticles and head groups of phospholipids. At lower surface pressure, nanoparticles can penetrate into the monolayers and the positive charges carried by nanoparticles benefits the enrichment of phospholipid molecules at surface, which not only increases the mean molecular area but also hinders the formation of phospholipid liquid-condensed (LC) phase. However, when surface pressure is higher, the nanoparticles flee away from the surface and some of the phospholipid molecules are pulled out of the monolayers together to the subphase and decrease the order degree of the monolayers. Moreover, nanoparticles can destroy the hydrogen-bond between water molecules and phosphate head groups and thus lead to the dehydration of phosphate groups. This work confirms that chitin nanoparticles can affect the surface behavior of DPPC/DPPG monolayers. Furthermore, the results obtained using mixed monolayer containing two major lung surfactants DPPC/DPPG and nanoparticles will be helpful for deep understanding the harm of PM2.5 to lung health.

How to design intelligent carriers for delivering drugs to the target accurately and releasing drug timely with the help of a certain environmental stimulus is still a challenge in tumor treatment. In this work, pH-sensitive bola-type triblock copolymers, composed of poly(2-(diisopropylamino) ethylmethacrylate) (PDPA) and methoxy-poly(ethyleneglycol) (mPEG), were synthesized. Liposomes containing these copolymers (Liposome@Bola) have been prepared by simply mixing the copolymer with phospholipids and cholesterol. From the fluorescence polarization measurement, the stability of Liposome@Bola was found to be increased a lot comparing to the pure liposome. As a result, the doxorubicin (DOX) leakage of the former was restrained in neutral environment. However, when pH decreased from 7.4 to 6.0, DOX released percentage had been increased 30-60 points, which was heavily depend on the phospholipid composition. Furthermore, the size effects of PEG and PDPA segments were also investigated. These results indicated the synthesized bola-type copolymers improved the pH-controllability of drug release of liposome, i.e., increased the difference between the release amount under pH 7.4 and pH 6.0. The bola-type copolymer exhibited a good potential application in smartly controlling drug delivery system.

Solute transport behavior across liquid–liquid interfaces plays important roles in many chemical engineering processes and usually occurs in the presence of surfactants. In this work, we report a full all-atom molecular dynamics simulation study of dimethyl sulfoxide (DMSO) crossing a water/hexane interface in different concentrations of sodium dodecylsulfate (SDS). By analyzing various properties, ranging from the configuration and energetic behaviors to the dynamic characteristics, we conclude that the presence of SDS has multiple non-trivial effects: (1) the association of SDS at the interface drives the interfacial region wider and decreases the interfacial tension with an almost linear dependence on SDS concentration; (2) higher SDS concentrations result in both a lower self-diffusion coefficient for DMSO and a smaller resistance force to DMSO moving out of the interfacial region, causing the exchange of DMSO between the interface and bulk region to become more frequent; and (3) the transition of the orientation preference of DMSO molecules passing from the interface to the water-rich phase vanishes. Current simulation studies examining the molecular level provide helpful insights for understanding the influence of surfactants on solute transport.

A new phase separation system, aqueous multiphase system (MuPSs, ranging from two to four phases), containing surfactants and polymer (SDS/DTAB/PEG/NaBr/H 2 O) was designed and the complicated four-phase systems were investigated systematically. To interpret the phase separation phenomena, the phase composition, phase density, phase volume ratio between the studied phase and the whole system as well as the particle size and zeta potential of aggregates in each phases were investigated. The results have shown that the multiphase system contains liquid crystal phase, which may imply a close relationship between MuPSs and liquid crystal. At the same time, it seems there is a direct relationship between zeta potential of the existed phase and the appearance of new phase. Phase composition analysis results illustrate that the rich component for the three phases from top to the third one are PEG, DTAB, and SDS, respectively. However, the bottom phase is almost dilute brine. Furthermore, the differential scanning calorimetry experiments prove that the micro-complexity of aggregates in different phases is different from each other. The studied MuPSs are very stable but temperature sensitive; the coexisted phases have different extraction power to xylenol orange because of the variation of composition. The higher stability of MuPSs makes it useful when the storage and long-term stability of the separation media are important. The work not only provides theoretical guidance for the development of efficient extraction and separation technology but also provides new opportunities for the development of aqueous multiphase systems.

An array of ten β-D-glucopyranosides with varied alkyl chain lengths were enzymatically synthesized. It was found that for longer alkyl chains a lower initial rate and final yield of glucoside was obtained except for methyl glucoside because of the severe toxicity of methanol to the enzyme. From a thermodynamics point of view, the equilibrium constant and Gibbs free energy variation of the glucoside syntheses were systematically investigated. To improve the final yields of the glucosides containing long alkyl chains the equilibrium of the enzymatic glucoside synthesis was altered. The equilibrium yield of decyl β-D-glucoside increased from 1.9% to 6.1% when the water content was reduced from 10% to 5% (v/v) using tert-butanol as a cosolvent and 0.10 mol/L of glucose as a substrate. As for the other longer alkyl chain glucosides, heptyl β-D-glucoside was found to have significant surface activity as well.

Dielectric materials with ultralow dielectric constants (

The transport of biomolecules such as DNA, RNA and proteins in organism is important for life processes. The translocation of these biomolecules through a nanopore in the biomembrane is one of the key steps. In this work, the fast-driven process of a homopolymer translocated through a nanopore has been studied by dissipative particle dynamics (DPD) with two different dissipative radii in three dimensions and compared with the results of Langevin dynamics (LD) method. The results show that the scaling relationship between translocation time (r) and the polymer chain length (N) is τ ∼ N 0.94 by DPD method with small dissipative radius, and τ ∼ N 0.98 with large dissipative radius. However, LD method gives the scaling relationship τ ∼ N 1.27 . In addition, the translocation time by LD method is larger than that by DPD method for the same chain. During the translocation process, the size of subchain of a polymer on the trans side is larger than the size of subchian on the cis side. Moreover, the gyration radius (Rg) of the subchain with the subchain length (L) has a good scaling relationship on the trans side. The scaling relationship is R g ∼ L 0.79 by DPD method with small dissipative radius, R g ∼ L 0.64 with large dissipative radius, and R g ∼ L 0.37 by LD method. The fluctuation of the force resulted from the thermostat decays in the order of LD, DPD with large dissipative radius, and DPD, LD with small dissipative radius. It is shown that the results are different using different simulation methods. Model parameters have also effect on the simulation results. The reasons for the difference are preliminarily analyzed.

A reaction density functional theory (R-DFT) is developed for chemical reactions in confined space by integrating reaction thermodynamics and DFT for chain fluids. The theory is applied to investigate DNA melting in slit pores, with nucleotides represented by coarse-grained charged Lennard-Jones particles. Three types of slit pores are considered for DNA melting: repulsive pore, attractive pore, and under electric field. In repulsive pores, the melting temperature increases slightly with reducing pore width, and the increase magnitude is nearly the same for DNA of different chain lengths. The double-strand DNA (dsDNA) and single-strand DNA (ssDNA) are located in the slit center, particularly for long DNA due to the effect of configuration entropy. In attractive pores, the melting temperature increases with increasing wall-fluid interaction. The DNA chains are preferentially adsorbed near the slit walls with a strong wall-fluid interaction. Under electric field, the melting temperature increases slightly and is more distinct for shorter DNA.

A molecular thermodynamic model is developed to predict DNA melting in ionic and crowded solutions. Each pair of nucleotides in the double-stranded DNA and each nucleotide in the single-stranded DNA are respectively represented by two types of charged Lennard-Jones spheres. The predicted melting curves and melting temperatures T(m) of the model capture the general feature of DNA melting and match fairly well with the available simulation and experimental results. It is found that the melting curve is steeper and T(m) is higher for DNA with a longer chain. With increasing the fraction of the complementary cytosine-guanine (CG) base pairs, T(m) increases almost linearly as a consequence of the stronger hydrogen bonding of the CG base pair than that of adenine-thymine (AT) base pair. At a greater ionic concentration, T(m) is higher due to the shielding effect of counterions on DNA strands. It is observed that T(m) increases in the presence of crowder because the crowder molecules occupy a substantial amount of system volume and suppress the entropy increase for DNA melting. At a given concentration, a larger crowder exhibits a greater suppression for DNA melting and hence a higher T(m). At the same packing fraction, however, a smaller crowder leads to a higher T(m).

Novel large-scale hollow ZnO spherical shells were synthesized by ionic liquids assisted hydrothermal oxidization of pure zinc powder without any catalyst at a relatively low temperature of 160 °C. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) patterns show that the shells are composed of ZnO and the structure of the shells is very unique. Textured flower-like ZnO consisting of ZnO rods is grown on the outer surfaces of shells forming a triple assembly. Room-temperature photoluminescence spectra of the oxidized material show a sharp peak at 379 nm and a wider broad peak centered at 498 nm. The possible growth mechanism of the triple assembly of ZnO is discussed in detail.

Correction for ‘Effects of polymers on the properties of hydrogels constructed using sodium deoxycholate and amino acid’ by Yi Guo et al., RSC Adv., 2018, 8, 8699–8708.

The effect of added salts (NaCl, KCl and NaBr) on the aqueous two-phase system (ATPS) formed in mixtures of Gemini(12-3-12, 2Br−)/sodium dodecyl sulfate/polyethylene glycol has been investigated. Phase diagrams of the aqueous systems containing Gemini(12-3-12, 2Br−), sodium dodecyl sulfate (SDS), polyethylene glycol(PEG) and a salt have been determined experimentally at 313.15 K. The results indicate that the addition of salts not only induces the appearance of ATPS-A (in which anionic surfactant is in excess), shortens the phase separation time, enlarges the regions of ATPS-C (in which cationic surfactant is in excess), and decreases the minimum concentration required for forming an ATPS, but also alters the matching between anionic and cationic surfactants. Extractive experiments also showed that these salts notably enhance the extraction ability of ATPS; the Gemini-rich phase exhibits prominent cohesive action with xylenol orange, regardless of whether or not it is the upper phase or the lower phase.

Interactions between DNA and the cationic gemini surfactant trimethylene-1,3-bis(dodecyldimethylammonium bromide) (12-3-12) in aqueous solution have been investigated by UV–vis transmittance, zeta potential, and fluorescence emission spectrum. Complexes of DNA and gemini surfactant are observed in which the negative charges of DNA are neutralized by cationic surfactants effectively. The DNA-induced micelle-like structure of the surfactant due to the electrostatic and hydrophobic interactions is determined by the fluorescence spectrum of pyrene. It is found that the critical aggregation concentration (CAC) for DNA/12-3-12 complexes depends little on the addition of sodium bromide (NaBr) because of the counterbalance salt effect. However, at high surfactant concentration, NaBr facilitates the formation of larger DNA/surfactant aggregates. Displacement of ethidium bromide (EB) by surfactant evidently illustrates the strong cooperative binding between surfactant and DNA. In contrast to that in the absence of surfactant, the added NaBr at high surfactant concentration influences not only the binding of surfactant with DNA, but also the stability of DNA/EB complex.

The middle-phase microemulsion (Winsor III) induced by salt in the low surfactant + cosurfactant (S + A) region of n -butanol/ n -octane/water/alkanediyl-α,ω(dimethydodecyl-ammonium bromide) (12-3-12) system was investigated by salinity scan. It is shown that the original water-in-oil single phase cannot form Winsor III even when the NaCl aqueous solution added reaches saturation. However, the original coexisting multi-phase and oil-in-water single phase can form Winsor III easily in a wide concentration range of salt, which is favorable to the application of Winsor III. The super low salinity for the initial formation of Winsor III ( S 1 ) attributes to the special structure of geminis. The water content, salinity, and temperature have great effect on the volume fraction of Winsor III and the temperature induces different phase transition from Winsor II to Winsor III. The condition for the formation of stable Winsor III was obtained by the interfacial tension (IFT) measurements. The multi-phase microemulsion was also studied by fluorescence, and the information, which was used to determine the microstructure of single-phase microemulsion. The results agree well with that obtained from the conductivity measurement carried out in our previous work.

Salts NaCl, KCl or NaBr shorten the phase-separation time of the ATPS (aqueous two-phase system) in mixed solutions of Gemini (12-3-12,2Br − ) and sodium dodecyl sulfate (SDS). They also change the region of ATPS; it moves toward higher molar mixing ratios of Gemini to SDS and becomes wider. The minimum concentration of surfactant needed for the formation of ATPS is also lowered. Negative ions play the dominant role. Densities of the coexisting phases are strongly influenced by the total concentration of surfactants, the molar mixing ratio of Gemini to SDS, temperature and the type of salt. For some cases, phase inversion (the upper phase changes to lower and the bottom phase changes to upper) appears. Salts notably enhance extraction ability; the oil-like phase (looks like oil in appearance), a Gemini-rich solution, shows affinity for xylenol orange. Results obtained from negative-staining and transmission electron microscopies show that salts change the microstructures of the two phases. In the oil-like phase, the long rod-like micelles tend to congregate into big-rammed aggregates and form a coarse network structure that increases viscosity. The conjugate phase contains mixed multilamellar vesicles, micelles, loops and cylindrical micelles.

Phase behavior and microstructures have been investigated for aqueous mixtures of cationic Gemini surfactant (12-3-12,2Br−) and anionic surfactant sodium dodecyl sulfate (SDS) using freeze-etching and negative-staining and with transmission electron microscopy (TEM). The phase diagram shows different regions characterized by different microstructures. Most of the regions are occupied by multi-lamellar phases in which vesicles coexist with micelles when the solutions are dilute. The multi-lamellar vesicles have higher stability because of their special structures. The ratio of vesicles to micelles varies with concentration and composition of the mixed-surfactant solutions. At higher surfactant concentrations, we observe other phases: the lamellar phase, anisotropic phase, aqueous two-phase system (ATPS), rod-like micelle phase, as well as other unique microstructures such as cylindrical micelles formed by short rod-like micelles, and porous morphology. Observations are reported for the transformation among different phases, especially from rod-like to spherical micelles.

The phase behavior of a system of n-butanol/n-octane/water/cationic gemini surfactant, alkanediyl- α , ω -(dimethydodecyl-ammonium bromide)(12-n-12, n = 3 , 4 , 6 ), has been investigated by determination the pseudo-ternary phase diagrams. The results have shown that the spacer group of gemini surfactant has a great effect on the phase behavior. The longer the spacer group for the geminis, the more similar the geminis properties to the traditional ones. The mixing content of surfactant and cosurfactant needed for forming microemulsions increases with the geminis' spacer group. The study has also shown that the shorter spacer group of geminis is favorable for the formation of higher ordered surfactant aggregates such as liquid crystals. Furthermore, the microstructures of each region for the studied systems have been investigated by electrical conductivity measurements, UV-visible absorbance spectra of pyrene probe, and dynamic light scattering (DLS). All the results are in accord with each other. DLS makes use of the sensitivity of DLS to structural changes and as expected the hydrodynamic diameter of the microemulsion droplet changes as the transformation of microemulsion microstructures take place. Moreover, the spherical and network structures of microemulsion were further verified by freezing-etching TEM.

Interactions between cationic gemini surfactant alkanediyl- α , ω -bis(dodecyldimethylammonium bromide) (12-n-12, n = 3 , 4 , 6 ) and oppositely charged polyelectrolyte sodium polyacrylate (NaPAA) in aqueous solution have been investigated by measuring fluorescence, conductivity, UV–vis transmittance, dynamic lighting scattering, and transmission electron microscopy. Micelle-like structure and 12-n-12/NaPAA complex are observed to form due to the electrostatic and hydrophobic interactions, and the effective diameter of the complex reduces with increasing 12-n-12 concentration. The microstructures of 12-n-12/NaPAA solution determined from fluorescence and electron microscopy measurements are in good agreement. The spacer length is found to play an important role in the interactions of 12-n-12 with NaPAA.

Gemini is defined as a surfactant made up of two identical amphiphilic moieties connected by a spacer group at the level of head groups or the alkyl chains close to the head groups. Mesostructures or morphologies of mixed surfactant solutions containing cationic gemini (12-3-12,2Br−) and anionic SDS have been studied by both experiments and simulations. Negative-staining transmission electron microscope was used to determine the structures in different regions of the ternary, most of those regions are occupied by multilamellar phases in which vesicles coexist with micelles when the solutions are dilute. At higher surfactant concentrations, the lamellar phase, rodlike micelle phase, as well as other unique structures such as cylindrical micelles formed by short rodlike ones are observed. For simulations, we adopted dissipative particle dynamics (DPD) technique. With carefully chosen parameters, especially the conservative term, we could reproduce a great variety of mesostructures including spherical micelles, rodlike micelles, planar micelles, network with junctions, bilayer membranes as well as multilamellar aggregates, most of which can be found in corresponding experimental work. DPD results also reveal vividly the self-assembling mechanism that the dispersed surfactant molecules are organized to form small micelles, then fused and twisted to encapsulate water to form vesicles.

The effect of hydrophilicity or hydrophobicity of polyelectrolyte on the interaction between polyelectrolyte and oppositely charged surfactants was investigated by using coarse-grained molecular dynamics simulations. The aggregation of surfactants on the hydrophilic polyelectrolyte is significantly different from that on the hydrophobic polyelectrolyte. The complexes evolve from the "bottle brush", through the "necklace", then to the micelle. However, the rod-like micelle, in which polyelectrolyte wraps around the micelle surface, only appears in the hydrophilic polyelectrolyte system. For the hydrophobic polyelectrolyte system, the spherical micelle is formed, and the polyelectrolyte penetrates into the hydrophobic core of complexes. The hydrophobic nature of the surfactant tails induces the surfactant's tendency to depart from the hydrophilic polyelectrolyte and point toward the bulk phase, but it is apt to combine with the hydrophobic polyelectrolyte, leading to a parallel configuration between the surfactants and the polyelectrolyte. When the charge ratio (Z) of surfactant to polylelectrolyte is lower, the polyelectrolyte shows extended structure, and with the increase of Z, the polyelectrolyte collapse undergoes either a continuous or an abrupt change depending on if it is a hydrophobic or hydrophilic polyelectrolyte. At higher charge density of the hydrophilic polyelectrolyte, there is a synergistic effect of the electrostatic interaction between surfactant and polyelectrolyte, with the hydrophobic interaction among the adsorbed surfactants. For the hydrophobic polyelectrolyte system, no synergistic effect is observed.

Interactions between ionic liquid surfactant [C 12 mim]Br and DNA in dilute brine were investigated in terms of various experimental methods and molecular dynamics (MD) simulation. It was shown that the aggregation of [C 12 mim]Br on DNA chains is motivated not only by electrostatic attractions between DNA phosphate groups and [C 12 mim]Br headgroups but also by hydrophobic interactions among [C 12 mim]Br alkyl chains. Isothermal titration calorimetry analysis indicated that the [C 12 mim]Br aggregation in the presence and absence of DNA are both thermodynamically favored driven by enthalpy and entropy. DNA undergoes size transition and conformational change induced by [C 12 mim]Br, and the charges of DNA are neutralized by the added [C 12 mim]Br. Various microstructures were observed such as DNA with loose coil conformation in nature state, necklace-like structures, and compact spherical aggregates. MD simulation showed that the polyelectrolyte collapses upon the addition of oppositely charged surfactants and the aggregation of surfactants around the polyelectrolyte was reaffirmed. The simulation predicted the gradual neutralization of the negatively charged polyelectrolyte by the surfactant, consistent with the experimental results.

The micellization of cationic gemini surfactant trimethylene-1,3-bis (dodecyldimethylammonium bromide) (12-3-12·2Br) was investigated and critical micelle concentrations (CMC) and thermodynamic parameters were evaluated as functions of ionic strength and temperature. The micellization of 12-3-12·2Br is entropically driven and thermodynamically favored. Raising the temperature slightly increases the CMC, while increasing the ionic strength lowers the CMC. A multi-technique study of the 12-3-12·2Br/DNA interaction and its dependence on ionic strength, temperature and DNA concentration were presented. DNA with loose coil conformation, necklace-like structure, highly ordered toroidal aggregates and coexisting of large aggregates and small structures in DNA/12-3-12·2Br system were observed. Critical aggregation concentrations (CAC), interaction saturation concentrations (C(2)), and associated thermodynamic parameters were determined. The screening effect of salt decreases the DNA/12-3-12·2Br electrostatic attraction, but favors the formation of free 12-3-12·2Br micelles or aggregates on the DNA chain. DNA acts as a separate phase contacting with the surfactant molecules and therefore CAC is independent of DNA concentration. Increasing DNA concentration postpones the appearance of free micelle in bulk phase, consequently increases the C(2). Finally an interaction mechanism between 12-3-12·2Br and DNA was proposed.