A Cu-Ag double-layer coating strategy for stable and reversible Zn metal anodes.

Structuring a stable artificial coating to mitigate dendrite growth and side reactions is an effective strategy for protecting the Zn metal anode. Herein, a Cu-Ag double-layer metal coating is constructed on the Zn anode (Zn@Cu-Ag) by simple and in-situ displacement reactions. The Cu layer enhances the bond between the Ag layer and Zn substrate by acting as an intermediary, preventing the Ag coating from detachment. Concurrently, the Ag layer serves to improve the corrosion resistance of Cu metal. During plating, the initial Cu sheets and Ag particles on the surface of Zn@Cu-Ag electrode gradually transform into a flat and smooth layer, resulting in the formation of AgZn, AgZn3, and (Ag, Cu)Zn4 alloys. Alloys play a multifunctional role in inhibiting dendrite growth and side reactions due to decreased resistance, low nucleation barrier, enhanced zincophilicity, and strong corrosion resistance. Consequently, the Zn@Cu-Ag symmetric cell exhibits continuous stable performance for 3750 h at 1 mA cm-2. Furthermore, the Zn@Cu-Ag||Zn3V3O8 full cell achieves an initial capacity of 293.4 mAh g-1 and realizes long cycling stability over 1200 cycles. This work provides new insight into the engineering of an efficient artificial interface for highly stable and reversible Zn metal anodes.

In Situ Spontaneous Construction of Zinc Phosphate Coating Layer Toward Highly Reversible Zinc Metal Anodes.

Aqueous zinc ion batteries have received widespread attention due to their merits of high safety, high theoretical specific capacity, low cost, and environmental benignity. Nevertheless, the irreversible issues of Zn anode deriving from side reactions and dendrite growth have hindered its commercialization in large-scale energy storage systems. Herein, a zinc phosphate tetrahydrate (Zn3 (PO4 )2 ·4H2 O, ZnPO) coating layer is in situ formed on the bare Zn by spontaneous redox reactions at room temperature to tackle the above issues. Particularly, the dense and brick-like ZnPO layer can effectively separate the anode surface from the aqueous electrolyte, thus suppressing the serious side reactions. Moreover, the ZnPO layer with high ionic conductivity, high Zn2+ transference number, and low nucleation barrier permits rapid Zn2+ transport and enables uniform Zn deposition, ensuring dendrite-free Zn deposition. As a result, the ZnPO@Zn symmetric battery achieves a high Coulombic efficiency of 99.8% and displays ultrahigh cycle stability over 6000 h (> 8 months), far surpassing its counterparts. Furthermore, the ZnPO@Zn||MnO2 full battery exhibits excellent electrochemical performances. Therefore, this work provides a new reference for simple and large-scale preparation of highly reversible Zn metal anodes, and has great potential for practical applications.

Synthesis and Propulsion of Magnetic Dimers under Orthogonally Applied Electric and Magnetic Fields.

Anisotropic particles have been widely used to make micro/nanomotors that convert chemical, ultrasonic, electrical, or magnetic energy into mechanical energy. The moving directions of most colloidal motors are, however, difficult to control. For example, asymmetric dimers with two lobes of different sizes, ζ-potential, or chemical composition have shown rich propulsion behaviors under alternating current (AC) electric fields due to unbalanced electrohydrodynamic flow. While they always propel in a direction perpendicular to the applied electric field, their moving directions along the substrate are hard to control, limiting their applications for cargo delivery. Inspired by two separate engine and steering wheel systems in automobiles, we use orthogonally applied AC electric field and direct current (DC) magnetic field to control the dimer's speed and direction independently. To this end, we first synthesize magnetic dimers by coating dopamine-functionalized nanoparticles on geometrically asymmetric polystyrene dimers. We further characterize their static and dynamic susceptibilities by measuring the hysteresis diagram and rotation speed experimentally and comparing them with theoretical predictions. The synthesized dimers align their long axes quickly with a planar DC magnetic field, allowing us to control the particles' orientation accurately. The propulsion speed of the dimers, on the other hand, is tunable by an AC electric field applied perpendicularly to the substrate. As a result, we can direct the particle's motion with predesigned trajectories of complex shapes. Our bulk-synthesis approach has the potential to make other types of magnetically anisotropic particles. And the combination of electric and magnetic fields will help pave the way for the assembly of magnetically anisotropic particles into complex structures.

Preliminary proposal: a classification system for reconstruction with autologous femoral head after periacetabular tumors resection.

BACKGROUND: Although researchers have adopted various methods for the resection and reconstruction of periacetabular tumors, the total incidence rate of complications remains high. Aiming for preserving the acetabulum and reducing the risk of complications, we applied a surgery method using tumor-free autologous femoral head to reconstruct the defective acetabulum after resection of periacetabular tumors followed by performing a conventional total hip arthroplasty (THA). Moreover, we proposed a preliminary classification system for these surgery methods. METHODS: We retrospectively reviewed 6 patients treated with acetabulum reconstruction combined with autologous femoral head following peri-acetabulum resection between April 2010 and May 2018. All patients were diagnosed as periacetabular tumors including chondrosarcoma (n = 5) and chondroblastoma (n = 1). Clinical data such as age, diagnosis, complications, local recurrence or metastasis, and function (Musculoskeletal Tumor Society 1993, MSTS93) were documented. The average time of follow-up was 62.5 months (range, 17 to 106 months). RESULTS: A total of 5 patients survive with average MSTS93 score of 27.8 points (range, 26-30). One patient, suffering from multiple bone metastasis prior treatment, ended up dying. One who had received radiotherapy before surgery had poor incision healing. Further, a classification system was preliminary proposed in 2 patients involving the pubis (type A) and 4 patients involving ischium (type B). CONCLUSIONS: Based on the results, we preliminary proposed a classification system for reconstruction with autologous femoral head after periacetabular low malignant tumors resection. The clinical results suggested that surgery methods involving pubis (type A) and ischium (Type B) are safe and feasible. However, further researches should be conducted to verify our classification system.

Prussian blue analogue functionalized magnetic microgels with ionized chitosan for the cleaning of cesium-contaminated clay.

To deal with regeneration of nuclear-waste-contaminated soil, it is important to develop new materials and techniques for effective removal of radioactive cesium ions from clay. We report herein a synergistic remediation method for cleaning cesium-contaminated clay by Prussian blue analogue-functionalized magnetic microgel along with ionized chitosan. The magnetic microgels were prepared by surface polymerization of 4-vinyl pyridine and styrene on magnetite nanoparticles and attachment of Prussian blue analogues by ligand exchange reaction. The adsorption of cesium ions by magnetic microgels in aqueous solution follows the second-order kinetics process. And the maximum adsorption capacity was determined to be 149.70 mg/g by Langmuir adsorption model. When ionized chitosan hydrochloride was mixed with cesium-contaminated clay, we found that 200 mg/g clay of chitosan hydrochloride can realize 87.6 % of cesium release from clay within 2 h. Further use of magnetic microgel adsorbents can adsorb 95.5 % free cesium ions in solution, achieving an overall 83.7 % cleaning efficiency from cesium-contaminated clays. The microgels can be regenerated effectively and recycled magnetically while keeping the adsorption capacity constant after multiple times of use. The underlying principle demonstrated in this work can be extended to remediation of other types of radionuclides or heavy-metal ions in contaminated soil.

Functionalized Nanoparticles for the Dispersion of Gas Hydrates in Slurry Flow.

Gas hydrates are crystals that can form in oil and gas production. Their agglomeration in flowlines may disrupt the normal production. One current strategy of hydrate management is to inject an anti-agglomerant, a type of low-dosage hydrate inhibitor that prevents hydrate agglomeration. Concerns in the use of these chemicals include their toxicity, cost, and environmental impacts. In this study, we exploited functionalized nanoparticles in place of anti-agglomerants to produce hydrate slurry, with the potential benefit of nanoparticles to be more environmentally friendly and conveniently recyclable. We coated 256 nm spherical silica nanoparticles with different hydrophobicity and evaluated their performance for the hydrate dispersion at atmospheric and high pressure. Nanoparticles with moderate hydrophobicity stabilized oil-in-water (O/W) or water-in-oil (W/O) emulsions. Direct visualization of the cyclopentane hydrate formation from the nanoparticle-stabilized emulsions revealed different morphologies of hydrate particles depending on whether the nanoparticles prevented agglomeration. We also measured the apparent viscosity of a hydrate-nanoparticle mixture using a high-pressure rheometer. Nanoparticles with moderate hydrophobicity during hydrate formation slowed the viscosification, reduced the maximum viscosity, increased the water conversion, and ultimately helped to maintain a low steady-state viscosity. Increasing nanoparticle or salt concentrations also improved the gas hydrate dispersion. Our study demonstrated the great potential of using nanoparticles in preventing agglomeration of gas hydrates under realistic pipeline flow conditions.

Change the Collective Behaviors of Colloidal Motors by Tuning Electrohydrodynamic Flow at the Subparticle Level.

As demonstrated in biological systems, breaking the symmetry of surrounding hydrodynamic flow is the key to achieve autonomous locomotion of microscopic objects. In recent years, a variety of synthetic motors have been developed based on different propulsion mechanisms. Most work, however, focuses on the propulsion of individual motors. Here, we study the collective behaviors of colloidal dimers actuated by a perpendicularly applied AC electric field, which controls the electrohydrodynamic flow at subparticle levels. Although these motors experience strong dipolar repulsion from each other and are highly active, surprisingly, they assemble into a family of stable planar clusters with handedness. We show that this type of unusual structure arises from the contractile hydrodynamic flow around small lobes but extensile flow around the large lobes. We further reveal that the collective behavior, assembled structure, and assembly dynamics of these motors all depend on the specific directions of electrohydrodynamic flow surrounding each lobe of the dimers. By fine-tuning the surface charge asymmetry on particles and salt concentration in solution, we demonstrate the ability to control their collective behaviors on demand. This novel type of active assembly via hydrodynamic interactions has the potential to grow monodisperse clusters in a self-limiting fashion. The underlying concept revealed in this work should also apply to other types of active and asymmetric particles.

Inducing Propulsion of Colloidal Dimers by Breaking the Symmetry in Electrohydrodynamic Flow.

We show that dielectric colloidal dimers with broken symmetry in geometry, composition, or interfacial charges can all propel in directions that are perpendicular to the applied ac electric field. The asymmetry in particle properties ultimately results in an unbalanced electrohydrodynamic flow on two sides of the particles. Consistent with scaling laws, the propulsion direction, speed, and orientation of dimers can be conveniently tuned by frequency. The new propulsion mechanism revealed here is important for building colloidal motors and studying collective behavior of active matter.