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It is well-known that surfactants tend to aggregate into clusters or micelles in aqueous solutions due to their special structures, and it is difficult for the surfactant molecules involved in the aggregation to move spontaneously to the oil-water interface. In this article, we developed a new grand-canonical molecular dynamics (GCMD) model to predict the saturated adsorption amount of surfactant with constant concentration of surfactant molecules in the bulk phase, which can prevent surfactants aggregating in the bulk phase and get the atomic details of the interfacial structural change with increase of the adsorption amount through a single GCMD run. The adsorption of anionic surfactant sodium dodecyl sulfate (SDS) at the heptane-water interface was studied to validate the model. The saturated adsorption amount obtained from the GCMD simulation is consistent with the experimental results. The adsorption kinetics of SDS molecules during the simulation can be divided into three stages: linear adsorption stage, transition adsorption stage, and dynamic equilibrium stage. We also carried out equilibrium molecular dynamics (EMD) simulations to compare with GCMD simulation. This GCMD model can effectively reduce the simulation time with correct prediction of the interfacial saturation adsorption. We believe the GCMD method could be especially helpful for the computational study of surfactant adsorption under complex environments or emulsion systems with the adsorption of multiple types of surfactants.

Uniform hydrogel microparticles with MOF nanoparticles for molecular co-confinement of cascade enzymes are developed by droplet microfluidics to achieve enhanced stability and reusability under harsh conditions. Water-swollen polyacrylamide hydrogel is used for constructing the microparticles; while microporous zeolitic imidazolate framework-8 (ZIF-8) nanoparticles are incorporated in the hydrogel networks for multi-enzyme co-confinement. With the ZIF-8 nanoparticles as armour, the multiple enzymes in the microparticles show good stability for efficient biocatalytic cascades under harsh conditions. This is demonstrated by using glucose oxidase (GOx) and horseradish peroxidase (HRP) as typical cascade enzymes. The hydrogel microparticles with both GOx and HRP confined in their ZIF-8 nanoparticles exhibit enhanced stability for efficient biocatalytic cascades and storage, after treatment under harsh conditions involving high temperature, UV light, and protease. Moreover, the hydrogel microparticles allow easy recycling and good reusability after repeated treatment at high temperature (80 °C). This work provides a simple and efficient strategy to create multiple-enzyme-loaded microcarriers with good stability and reusability for biocatalytic cascades.

A novel type of reduced graphene oxide (rGO) modified melamine sponges (rGS) filling with paraffin (rGS-pf) is developed for efficient solar-thermal conversion and heat management. The microstructures, filling and holding capacity of paraffin in porous rGS, solar-thermal energy conversion and energy harvesting efficiency of the prepared rGS-pf have been investigated systematically. The content of rGO nanosheets coated on the skeletons of rGS-pf is only 0.11%, while the loading content of paraffin in the rGS-pf is as high as 97.53%. Based on the solar-thermal conversion property of rGO nanosheets in the rGS-pf and the heat storage ability of paraffin in the rGS-pf, the proposed rGS-pf provides excellent performance for heat management. The efficiency of solar-thermal conversion could reach up to 92.5%. The thermo-regulation provided by the proposed rGS-pf is real-time, repeatable and long-term stable. The results in this study provide valuable guidance for developing functional materials for efficient solar-thermal conversion and heat management.

A superhydrophilic nanostructured surface of zinc-coordinated polydopamine is formed by the growth and intertwining of the PDA/Zn nanowires via Zn–N and Zn–O bonds, which has potential for preventing biomaterial-associated biofouling and infections.

A novel type of functional graphene oxide nanosheets (GNs) modified with β-cyclodextrins (β-CDs) have been developed by coating dopamine-functionalized cyclodextrin (DACD) molecules on GNs for removing Bisphenol A (BPA) molecules from water. The DACD molecules with both β-CD groups for achieving adsorption property and dopamine (DA) groups for achieving adhesion property are synthesized by grafting DA onto carboxymethyl-β-cyclodextrin (CmβCD). The proposed DACD molecules can be firmly coated on the surfaces of various inorganic and organic substrates. Due to the large specific surface area of GNs, DACD-coated GNs (DACD@GNs) are proposed for efficient adsorption separation of BPA molecules from water. Due to the host-gust complexation between the BPA molecules in water and β-CDs on DACD@GNs, the fabricated DACD@GNs exhibit excellent adsorption performances. The adsorption kinetics can be explained via the pseudo-second-order model effectively. The experimental adsorption capacity of DACD@GNs is 11.29 mg·g−1 for BPA. Furthermore, after the adsorption process, the DACD@GNs can be easily separated from aqueous solutions via vacuum filtration with porous membranes, and then regenerated by simply washing with ethanol. The proposed strategy in this study can be used for effectively functionalizing the surfaces of various substrates with functional β-CDs, which is highly promising in applications in the field of adsorption separations, especially water treatments.

Controllable mass production of monodisperse droplets plays a key role in numerous fields ranging from scientific research to industrial application. Microfluidic ladder networks show great potential in mass production of monodisperse droplets, but their design with uniform microflow distribution remains challenging due to the lack of a rational design strategy. Here an effective design strategy based on backstepping microflow analysis (BMA) is proposed for the rational development of microfluidic ladder networks for mass production of controllable monodisperse microdroplets. The performance of our BMA rule for rational microfluidic ladder network design is demonstrated by using an existing analogism-derived rule that is widely used for the design of microfluidic ladder networks as the control group. The microfluidic ladder network designed by the BMA rule shows a more uniform flow distribution in each branch microchannel than that designed by the existing rule, as confirmed by single-phase flow simulation. Meanwhile, the microfluidic ladder network designed by the BMA rule allows mass production of droplets with higher size monodispersity in a wider window of flow rates and mass production of polymeric microspheres from such highly monodisperse droplet templates. The proposed BMA rule provides new insights into the microflow distribution behaviors in microfluidic ladder networks based on backstepping microflow analysis and provides a rational guideline for the efficient development of microfluidic ladder networks with uniform flow distribution for mass production of highly monodisperse droplets. Moreover, the BMA method provides a general analysis strategy for microfluidic networks with parallel multiple microchannels for rational scale-up.

In this study, a novel class of multifunctional responsive nanoparticles is designed and fabricated as drug nanocarriers for synergetic chemo-photothermal therapy of tumors. The proposed nanoparticles are composed of a thermo-/pH-responsive poly(N-isopropylacrylamide-co-acrylic acid) (PNA) nanogel core, a polydopamine (PDA) layer for photothermal conversion, and an outer folic acid (FA) layer as a targeting agent for the folate receptors on tumor cells. The fabricated nanoparticles show good biocompatibility and outstanding photothermal conversion efficiency. The proposed nanoparticles loaded with doxorubicin (DOX) drug molecules are stable under physiological conditions with low leakage of drugs, while rapidly release drugs in environments with low pH conditions and at high temperature. The experimental results show that the drug release process is mainly governed by Fickian diffusion. In vitro cell experimental results demonstrate that the PNA-DOX@PDA-FA nanoparticles can be phagocytized by 4T1 tumor cells and release drugs in tumor cell acidic environments, and confirm that the combined chemo and photothermal therapeutic efficacy of PNA-DOX@PDA-FA nanoparticles is higher than the photothermal therapeutic efficacy or the chemotherapeutic efficacy alone. The proposed multifunctional responsive nanoparticles in this study provide a novel class of drug nanocarriers as a promising tool for synergetic chemo-photothermal therapy of tumors.

Thermo-responsive polymers can experience the coil-to-globule transition with the temperature increases through the lower critical solution temperature (LCST). In this work, the coarse-grained molecular dynamics and Metadynamics (MetaD) are employed to investigate the dynamics and thermodynamics of structural change of a pair of poly(N-isopropylacrylamide) (PNIPAM) chains in aqueous solution. The results reveal that the PNIPAM molecules can move freely in aqueous solution below LCST, resulting in many extended conformations moving among several free energy basins on the free energy surface (FES); and these structures are dominated by the interaction force between PNIPAM and the water molecules. However, the PNIPAM molecules aggregate above LCST with collapsed conformations, leading to a deep basin on the FES; and these structures are dominated by the force between neighbouring PNIPAM chains. Each of the dominant mechanisms, namely, PNIPAM-water interaction force and intermolecular interaction force between PNIPAM chains, has an extreme tendency and corresponds to the extended and collapsed structures, respectively. However, the compromise in competition between these two mechanisms inevitably results in different characteristic structures including the extended and collapsed ones. In addition, the evolution of the trajectories at different temperatures are also analysed to examine the pathway of structural change.

Ultrasensitive real-time detection of trace Pb

The performance of vanadium redox flow batteries (VRFBs) is largely determined by the membrane as a separator. To address the trade-off issue between the proton conductance and vanadium resistance of sulfonated polyimide (SPI) membranes, novel covalent cross-linked polyfluoro sulfonated polyimide (PFSPI-PAA-X) membranes are developed by designing and synthesizing polyfluoro non-sulfonated diamine and adopting hydrophilic polyacrylic acid (PAA) as the cross-linking agent. The structures, morphology and physico-chemical properties of PFSPI-PAA-X membranes are systematically investigated. PFSPI-PAA-X membranes possess improved chemical stabilities in contrast to the pure PFSPI membrane. Among all PFSPI-PAA-X membranes, the PFSPI-PAA-25 membrane (0.15 Ω cm2) shows the lowest area resistance, which is even a little lower than that of the Nafion 212 membrane (0.16 Ω cm2). And, the PFSPI-PAA-25 membrane also has an extremely low vanadium permeability of 5.90 × 10−9 cm2 min−1, which is two orders of magnitude lower than that of the Nafion 212 membrane (7.53 × 10−7 cm2 min−1). The VRFB performances including the self-discharge time (PFSPI-PAA-25: 52.3 h, Nafion 212: 17.6 h), efficiencies at 60–300 mA cm−2 (PFSPI-PAA-25: CE = 97.3–99.9% and EE = 90.7–73.6%, Nafion 212: CE = 90.9–96.5% and EE = 84.7–72.0%) and peak power density (PFSPI-PAA-25: 451.4 mW cm−2, Nafion 212: 427.9 mW cm−2) of the PFSPI-PAA-25 membrane are all superior to those of the Nafion 212 membrane. Meanwhile, the PFSPI-PAA-25 membrane shows outstanding durability during the 500 times charge–discharge cycle test. Therefore, the as-prepared PFSPI-PAA-25 membrane with excellent cost-performance ratio has a bright future in replacing the Nafion 212 membrane for application in VRFBs.

Graphene oxide (GO) membranes have shown enormous promise in desalination and molecular/ionic sieving. However, the instability of GO membranes in aqueous solutions seriously hinders their practical applications. Herein, we report a novel and simple strategy to fabricate stable GO membranes in water-based environments through the insertion of various metal cations from metal foils (e.g., copper (Cu), iron (Fe), nickel (Ni), and zinc (Zn) foils) and natural deposition. Based on the cation-π, coordination, and electrostatic interaction between metal cations and GO nanosheets, the aqueous stability and mechanical strength of the membranes are significantly improved. The permeation rates for acetone, toluene, and p-xylene molecules across the GO membrane cross-linked by copper ions with a deposition time of 24 h are 0.966, 0.074, and 0.100 mol m-2 h-1, respectively. Moreover, this membrane displays excellent separation performance, and the separation factor of K+/Mg2+ is up to 68.8 in mono-/multivalent metal cation sieving, which indicate the effective molecular/ionic sieving performance. Meanwhile, the ionic sieving of the GO membrane cross-linked by copper ions has excellent repeatability and long-term stability. The versatility of this natural deposition strategy to fabricate GO membranes cross-linked by metal cations is investigated by using Fe foil, Zn foil, and Ni foil as well as other porous substrates such as polyvinylidene fluoride (PVDF), polyethersulfone (PES), and nylon membranes and filter paper. This fabrication strategy also enables low-cost preparation of large-area GO membranes. Therefore, GO membranes cross-linked by metal cations and prepared by this simple metal cation incorporation strategy have large potential application for molecular/ionic sieving in various solution systems.

A novel type of hybrid graphene oxide/laponite (GO/L) layered membrane is developed with stable two-dimensional (2D) nanochannels for efficient separations in aqueous environments. The electrostati...

A smart diffraction grating immunosensor based on antigen-responsive hydrogel with enhanced analyte-induced volume changes is developed for highly selective and sensitive detection of human immunog...

The hierarchical design of mesoscale structures in droplet templates determines the structure and functionality of the resultant microparticles. In this review, we summarize recent progress on the control of microfluidic emulsion templates for the synthesis of polymeric microparticles with desired functionality and internal structure. We introduce strategies for controlling the morphology and interfacial stability of emulsion templates. These strategies are based on manipulation of the mesoscale structure of amphiphilic molecules and nanoparticles at emulsion-droplet interfaces. We also discuss strategies for controlling the mesoscale structure of microparticles, which involve manipulating the interfacial mass-transfer and chemical reactions during template synthesis. We provide insight on the use of these strategies for the rational design and fabrication of polymeric microparticles with predictable internal structures and functionality at the single-particle level.

Pigmentary coloration can produce viewing angle-independent uniform colors via light absorption by chromophores. However, due to the limited diversity in the changes of the molecular configuration of chromophores to undergo color change, the existing materials cannot produce a wide range of visible colors with tunable color saturation and transmittance. Herein, we propose a novel strategy to create materials with a wide visible color range and highly tunable color saturation and transmittance. We fabricated a hydrogel with poly (acrylamide-co-dopamine acrylamide) networks swollen with Fe3+-containing glycerol/water in which the covalently crosslinked polyacrylamide backbone with pendant catechols can ensure that the hydrogel maintains a very stable shape. Hydrogels containing adjustable catechol-Fe3+ coordination bonds with flexible light-interacting configuration changes can display a wide range of visible colors based on the complementary color principle. The catechol-Fe3+ complexes can dynamically switch between noncoordinated and mono-, bis- and tris-coordinated states to harvest light energy from a specific wavelength across the whole visible spectrum. Therefore, these hydrogels can be yellow, green, blue, and red, covering the three primary colors. Moreover, color saturation and transmittance can be flexibly manipulated by simply adjusting the Fe3+ content in the hydrogel networks. The versatility of these smart hydrogels has been demonstrated through diverse applications, including optical filters for color regulation and colorimetric sensors for detecting UV light and chemical vapors. This proposed smart hydrogel provides a universal color-switchable platform for the development of multifunctional optical systems such as optical filters, sensors, and detectors.

The poor bacteriostasis and osseointegration properties of bioinert polyetheretherketone (PEEK) hinder its clinical application. This work reports a simple and versatile strategy for fabricating dual-functional coating with programmed sequential drug release properties on porous PEEK surfaces. The dual-drug-loaded composite coating composed of drug-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles and drug-loaded polyvinyl alcohol (PVA) gel can be immobilized on the surface of sulfonated PEEK by a cyclic freeze-thaw method. Based on the swelling of PVA and the slow degradation of PLGA, the composite coating can realize rapid release of antibacterial drugs and sustained release of osteogenic drugs. The in vitro antibacterial evaluations show that the porous PEEK modified with drug-loaded composite gel coating exhibits an early effective fight against Staphylococcus aureus (S.aureus). The results of in vitro cell experiments show that the PEEK materials modified by the composite gel coating can well support the normal growth, adhesion and proliferation of cells. In addition, the PEEK material coated with the drug-loaded composite gel is found to have positive effects on the osteogenic differentiation of cells in detections of alkaline phosphatase (ALP) activity of cells and the amount of calcium deposition on the surface of the material. The results demonstrate that the proposed porous PEEK modified with dual-drug-loaded composite gel coating simultaneously exhibits excellent osseointegration and exerts early effective antibacterial activity. This dual-functional PEEK material has great application potential in clinical bone tissue repair.