Matchstick-Like Cu₂S@Cu_<i>x</i>O Nanowire Film: Transition of Superhydrophilicity to Superhydrophobicity

We fabricated a matchstick-like Cu₂S@Cu_<i>x</i>O nanowire film on copper mesh by applying a Cu­(OH)₂ nanowires template-sacrificial method, which can transformed from superhydrophilic to superhydrophobic just after storage in air for a certain period without any further organic modification. The surface morphology, chemical composition and the wettability were investigated by Scanning Electron Microscopy (SEM), X-ray diffractometer (XRD), Raman, X-ray Photoelectron Microscopy (XPS), and contact angle measurement. Results showed that the change of surface chemical composition and the trapped air among the matchstick-like structures were the decisive factors for the wettability transition. Therefore, on-demand oil/water separation was achieved, which was performed by using the superhydrophilic–underwater superoleophobic mesh for separating light oil/water mixtures and the superhydrophobic one for separating heavy oil/water mixtures

Dissipative Particle Dynamics Simulation on the Nanocomposite Delivery System of Quantum Dots and Poly(styrene‑<i>b</i>‑ethylene oxide) Copolymer

Dissipative particle dynamics (DPD) simulation was used to investigate the self-assembling dynamics process of poly­(styrene-<i>b</i>-ethylene oxide) (PS-<i>b</i>-PEO) block copolymer and quantum dots (QDs) in an aqueous solution. The effects of molecular weight (MW) and segment construction of a PS–PEO block copolymer on the structure and size of the self-assembled micelles were discussed. The structural properties of micelles were characterized by a radial distribution function. The simulation results are qualitatively consistent with those of previous experiments and show that there are only small QD clusters. The hydrophobic PS chains form the micelle core, while the hydrophilic PEO chains form the shell. The size of the self-assembled PS–PEO/QDs micelle increases with the MW of PS-<i>b</i>-PEO block copolymer and the lengths of PEO and PS segments. The simulation results indicate that the assembling process includes four sequential transient stages: (1) the random distribution of all components in aqueous solution; (2) formation of small clusters with polymer chains and QDs; (3) crashing together of small spheres and the formation of larger aggregates; (4) stabilization of assembled micelles. The simulation reveals the physical insights of the QD loading mechanism of the PEG micelle at the mesoscopic scale, indicating the DPD simulation can be used as an adjunct to provide other valuable information for experiments

Inspired by Stenocara Beetles: From Water Collection to High-Efficiency Water-in-Oil Emulsion Separation

Inspired by the water-collecting mechanism of the Stenocara beetle’s back structure, we prepared a superhydrophilic bumps–superhydrophobic/superoleophilic stainless steel mesh (SBS-SSM) filter <i>via</i> a facile and environmentally friendly method. Specifically, hydrophilic silica microparticles are assembled on the as-cleaned stainless steel mesh surface, followed by further spin-coating with a fluoropolymer/SiO₂ nanoparticle solution. On the special surface of SBS-SSM, attributed to the steep surface energy gradient, the superhydrophilic bumps (hydrophilic silica microparticles) are able to capture emulsified water droplets and collect water from the emulsion even when their size is smaller than the pore size of the stainless steel mesh. The oil portion of the water-in-oil emulsion therefore permeates through pores of the superhydrophobic/superoleophilic mesh coating freely and gets purified. We demonstrated an oil recovery purity up to 99.95 wt % for surfactant-stabilized water-in-oil emulsions on the biomimetic SBS-SSM filter, which is superior to that of the traditional superhydrophobic/superoleophilic stainless steel mesh (S-SSM) filter lacking the superhydrophilic bump structure. Together with a facile and environmentally friendly coating strategy, this tool shows great application potential for water-in-oil emulsion separation and oil purification