Super-assembly platform for diverse nanoparticles with tunable topological architectures and surface morphologies.

Self-assembly leveraged by nature enables the sophisticated generation of a wide range of nanoparticles (NPs) with rich architectures and morphologies. However, existing artificial self-assembly platforms largely only allow for the fabrication of single type of NPs with limited structures, due to their inability to define interfacial interaction between seeds and growth materials, which is critically important to gain controllable growth patterns of the grown materials on the seeds' surface. Here, we report a versatile super-assembly platform that shows the capabilities to fabricate diverse NPs with tunable topological architectures and surface morphologies, e.g., molecular-like NPs, hollow asymmetric NPs, patchy NPs, etc. We unprecedentedly discovered the powerful functions of polyvinylpyrrolidone (PVP), which enable us to well define interfacial interaction between growth materials and seeds to achieve the controllable and tunable generation of various complex topological growth patterns. Moreover, the nucleation pattern (island nucleation or layered nucleation) of the patches can be thermodynamically modulated via the polarity of the solvent, while the number and size of the patches can be kinetically tuned by the ratio of polystyrene (PS), precursor, and catalyst. Interestingly, the hollow NPs can be generated by single-one processing step in our platform, unlike the multiple steps laboriously and widely employed by previously reported fabrication platforms. In addition, we demonstrate that our annealed NPs can not only selectively reflect visible light, and show well-controlled colors from gray, blue, to green, but also exhibit excellent photothermal conversion performances with a high photothermal conversion efficiency of 68.7% that are superior to currently routinely reported of 40%. This super-assembly platform can serve as a powerful toolset to sophisticatedly create varied NPs with tunable hierarchical architectures and controllable surface morphologies, which would significantly benefit the development of drug delivery, nanomaterial assembly, nano pigments, nanoreactors, and beyond.

Demulsification Performance and Mechanism of Tertiary Amine Polymer-Grafted Magnetic Nanoparticles in Surfactant-Free Oil-in-Water Emulsion.

Numerous cationic magnetic nanoparticles (MNPs) have previously been developed for demulsifying oil-in-water (O/W) emulsion, and results showed that the cationic MNPs could effectively flocculate and remove the negatively charged oil droplets via charge attraction; however, to the best of our knowledge, there are no research reports regarding the synergetic influence of both the positive charge density and interfacial activity of MNPs on the demulsification performance. In this study, three tertiary amine polymer-grafted MNPs, namely, poly(2-dimethylaminoethyl acrylate)-grafted MNPs (M-PDMAEA), poly(2-dimethylamino)ethyl methacrylate)-grafted MNPs (M-PDMAEMA), and poly(2-diethylaminoethyl methacrylate)-grafted MNPs (M-PDEAEMA), were synthesized and evaluated for their demulsification performance. Results demonstrated that a high positive charge density and superior interfacial activity of MNPs could cause partial oil droplet re-dispersion when excessive MNPs were introduced, leading to a lower magnetic separation efficiency and narrower demulsification window. Herein, a demulsification window is defined as a range of nanoparticle dosages in which the MNPs can effectively demulsify the O/W emulsion under certain conditions. For highly positively charged MNPs, their good interfacial activity could aggravate the formation of a narrower demulsification window. When tertiary amine polymer-grafted MNPs carried a lower positive charge density or weak interfacial activity, that is, M-PDMAEA at pH 4.0, M-PDMAEMA at pH 5.0-9.0, and M-PDEAEMA at pH 9.0-10.0, wide demulsification windows were observed. Additionally, a recycling experiment suggested that MNPs could maintain high demulsification efficiency up to at least five cycles, indicating their satisfactory recyclability. The three tertiary amine polymer-grafted MNPs can be potentially used for efficient demulsification from surfactant-free O/W emulsion in various pH ranges.

Interfacial-assembly engineering of asymmetric magnetic-mesoporous organosilica nanocomposites with tunable architectures.

The asymmetric morphology of nanomaterials plays a crucial role in regulating their physical and chemical properties, which can be tuned by two key factors: (i) interfacial interaction between seed particles and growth materials (anisotropic island nucleation) and (ii) reaction kinetics of the growth material (growth approach). However, controllable preparation of asymmetric nanoarchitectures is a daunting challenge because it is difficult to tune the interfacial energy profile of a nanoparticle. Here, we report an interfacial-assembly strategy that makes use of different surfactant/organosilica-oligomer micelles to actively regulate interfacial energy profiles, thus enabling controllable preparation of well-defined asymmetric nanoarchitectures (i.e., organosilica nano-tails) on magnetic Fe3O4 nanoparticles. For our magnetic nanocomposite system, the assembly structure of surfactant/organosilica-oligomer micelles and the interfacial electrostatic interaction are found to play critical roles in controlling the nucleation and architectures of asymmetric magnetic-mesoporous organosilica nanocomposite particles (AMMO-NCPs). Surfactant/organosilica-oligomer micelles with a one-dimensional wormlike linear structure could strengthen the interfacial assembly behavior between seed particles and growth materials, and thus achieved the longest tail length (25 µm) exceeding the previously reported highest recorded value (2.5 µm) of one order of magnitude. In addition, clickable AMMO-NCPs can employ a thiol-ene click reaction to modify their surface with a broad range of functional groups, such as amines, carboxyls, and even long alkyl chains, which allows for expanding functionalities. We demonstrate that C18 alkyl-grafted AMMO-NCPs can self-assemble into self-standing membranes with robust superhydrophobicity. In addition, carboxyl-modified AMMO-NCPs exhibit excellent adsorption capacity for cationic compounds. This study paves the way for designing and synthesizing asymmetric nanomaterials, which possess immense potential for future engineering applications in nanomaterial assembly, nanoreactors, biosensing, drug delivery, and beyond.

Resonant signals in the lithosphere-atmosphere-ionosphere coupling.

A study in the lithosphere, atmosphere and ionosphere (LAI) coupling often troubles scientists due to a certain distance between distinct instruments, which monitor geophysical parameters in different spheres. An instrumental system was established in southwest China (Leshan; LESH) for monitoring vibrations and perturbations in LAI (MVP-LAI). A ground-based Global Navigation Satellite System (GNSS) receiver at the YADU station locates ~ 260 km away that continuously receives electromagnetic signals transmitted from the BeiDou navigation System (BDS) geostationary satellites to monitor the total electron content (TEC) at the ionospheric pierce point right over the MVP-LAI system. The employment of YADU TEC benefits in elimination of possible shaking effects happening on multiple instruments at the LESH station and mitigation the troubles due to the discrepancy in observation places. Through a stacking process on the retrieved data for increase of signal to noise ratios, a novel phenomenon of the resonant LAI coupling at a fundamental mode of ~ 3.4 mHz and its multiples persists in ground vibrations, atmospheric pressure and TEC retrieved from the MVP-LAI system and the YADU station. The retrieved data share frequencies during the operational period of 1.5 months that is irrelevant to obvious events in the lithosphere, atmosphere and ionosphere. The persistence of the resonant LAI coupling is essential in the Earth's system.

Controllable Microemulsion Synthesis of Hybrid TiO2-SiO2 Hollow Spheres and Au-Doped Hollow Spheres with Enhanced Photocatalytic Activity.

Hollow structures in TiO2 materials can enhance the photocatalytic properties by reducing the diffusion length and improving the accessibility of active sites for the reactants. However, existing approaches for preparing hollow TiO2 materials have two drawbacks that restrict their engineering applicability: first, a heavy reliance on templates to form a hollow structure, which makes the preparation laborious, complicated, and costly; second, difficult-to-achieve high crystallization while maintaining the small grain size in calcinated TiO2, which is crucial for enhancing photocatalytic activity. Herein, a simple, effective method is proposed that not only enables the preparation of hybrid TiO2-SiO2 hollow spheres without the template fabrication and removal process via microemulsion technology but also achieves both high crystallization and a small grain size in calcinated TiO2 at once through the calcination of amorphous TiO2 with organosilane at a high temperature of 850 °C. The prepared TiO2-SiO2 hollow spheres with tunable sizes demonstrate high photocatalytic activity with a maximum k value of 133.74 × 10-3 min-1, which is superior to commercial photocatalyst P25 (k = 114.97 × 10-3 min-1). In addition, Au can be doped in the hybrid TiO2-SiO2 shell to gain Au-doped hollow spheres that show a high k value of up to 694.14 × 10-3 min-1, which is 6 times larger than that of P25 and much better than that reported in the literature. This study not only provides an effective approach to stabilize and tune the grain growth of the TiO2 photocatalyst during calcination but also enables the simple preparation of hollow TiO2-based materials with controllable hollow nanostructures.

Large air pressure changes triggered by P-SV ground motion in a cave in northern Taiwan.

Acoustic-gravity waves are generally considered to be one of the major factors that drive changes of the total electron content in the ionosphere. However, causal mechanisms of couplings between sources in the lithosphere and responses in the atmosphere and the ionosphere are not fully understood, yet. A barometer in the cave of the SBCB station records an unusual phenomenon of larger amplitudes in air pressure changes inside than those at the Xinwu station (outside). Accordingly, the comparison between the recorded data at the SBCB and Xinwu station can drive investigations of potential sources of the unusual phenomenon. Analytical results of phase angle differences reveal that the air pressure outside the cave at the Xinwu station often leads air pressure changes inside at the SBCB station at relatively low frequency bands. In contrast, the larger pressure changes at frequencies > ~ 5 × 10-4 Hz inside the cave at the SBCB station lead smaller changes outside at the Xinwu station. To expose causal mechanisms of the unusual phenomenon, continuous seismic waveforms are further conducted for examination. When the horizontal and vertical ground velocities of ground vibrations yield a difference in the phase angle close to 90°, coherence values between the air pressure changes and ground vibrations become large. This suggests that the pressure-shear vertical ground vibrations can drive air pressure changes. Meanwhile, the results shed light on investigating the existence of acoustic waves near the Earth's surface using a partially confined space underground due to that the assumptions of the waves can propagate upward into the atmosphere driving changes in the ionosphere.

Aluminum-doping-based method for the improvement of the cycle life of cobalt-nickel hydroxides for nickel-zinc batteries.

The unsatisfactory cycle life of nickel-based cathodes hinders the widespread commercial usage of nickel-zinc (Ni-Zn) batteries. The most frequently used methods to improve the cycle life of Ni-based cathodes are usually complicated and/or involve using organic solvents and high energy consumption. A facile process based on the hydrolysis-induced exchange of the cobalt-based metal-organic framework (Co-MOF) was developed to prepare aluminum (Al)-doped cobalt-nickel double hydroxides (Al-CoNiDH) on a carbon cloth (CC). The entire synthesis process is highly efficient, energy-saving, and has a low negative impact on the environment. Compared to undoped cobalt-nickel double hydroxide (Al-CoNiDH-0%), the as-prepared Al-CoNiDH as the electrode material displays a remarkably improved cycling stability because the Al-doping successfully depresses the transition in the crystal phase and microstructure during the long cycling. Benefiting from the improved performance of the optimal Al-CoNiDH electrode (Al-CoNiDH-5% electrode), the as-constructed aqueous Ni-Zn battery with Al-CoNiDH-5% as the cathode (Al-CoNiDH-5%//Zn) displays more than 14% improvement in the cycle life relative to the Al-CoNiDH-0%//Zn battery. Moreover, this Al-CoNiDH-5%//Zn battery achieves a high specific capacity (264 mAh g-1), good rate capability (72.4% retention at a 30-fold higher current), high electrochemical energy conversion efficiency, superior fast-charging ability, and strong capability of reversible switching between fast charging and slow charging. Furthermore, the as-assembled quasi-solid-state Al-CoNiDH-5%//Zn battery exhibits a decent electrochemical performance and satisfactory flexibility.

Controllable synthesis of raspberry-like PS-SiO2 nanocomposite particles via Pickering emulsion polymerization.

This paper presents a simple and controllable method for the synthesis of monodisperse nanometer-sized organic-inorganic raspberry-like polystyrene (PS)-SiO2 nanocomposite particles (NCPs) via Pickering emulsion polymerization, by simply using a silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate (MPS), as an auxiliary monomer and controlling its hydrolysis/condensation processes and amount. In this method, when MPS was stirred in acidic water with styrene (St) for a period of time, and then a basic silica solution added, raspberry-like PS-SiO2 NCPs were directly obtained after the polymerization. The whole process needs neither surface treatment for the silica particles nor additional surfactants or stabilizers. We propose that a silica-stabilized Pickering emulsion is formed through Si-OH reaction between the hydrolysis/condensation products of MPS distributed on the St droplets surface and the silica particles.

Controllable Synthesis and Surface Wettability of Flower-Shaped Silver Nanocube-Organosilica Hybrid Colloidal Nanoparticles.

Synthesis of hybrid colloidal particles with complex and hierarchical structures is attracting much interest theoretically and technically in recent years, but still remains a tremendous challenge. Here, we present a mild and controllable wet-chemical method for the synthesis of silver nanocube (Ag NC)-organosilica hybrid particles with finely tuned numbers (with one, two, three, four, five, or six) and sizes of organosilica petals, by simply controlling the affinity with Ag NC/nature, amount, and prehydrolysis process of alkoxysilanes. The morphologies of hybrid colloidal particles have an obvious influence on the surface wettability of the hybrid particle-based films. More and larger organosilica petals can increase the surface hydrophobicity of the hybrid particle-based films.

Facile synthesis of asymmetric Ag-organosilica hybrid nanoparticles with tunable morphologies and optical properties.

This study reports a simple and novel wet-chemical method for synthesizing asymmetric Ag-organosilica hybrid nanoparticles with finely-tuned morphologies and optical properties.

Fabrication, properties and applications of Janus particles.

Although the concept of Janus particles was raised in the early 1990s, the related research has not attracted considerable interest until recently due to the special properties and applications of these colloidal particles as well as the advances in new fabrications. Janus particles can be divided into three categories: polymeric, inorganic, and polymeric-inorganic, and each kind of Janus particles can be spherical, dumbbell-like, half raspberry-like, cylindrical, disk-like, or any of a variety of other shapes. Different Janus particles may share common preparation principles or require specific fabrication processes, and may have different assembly behaviours and properties. This critical review discusses the main fabrication methods of the three kinds of Janus particles, and then highlights the important properties and applications of these Janus particles developed in recent years, and finally proposes some perspectives on the future of Janus particle research and development.