Magnetic-Field Directed Vapor-Phase Assembly of Low Fractal Dimension Metal Nanostructures: Experiment and Theory

Ferromagnetic-Antiferromagnetic Coupling in Gas-Phase Synthesized M(Fe, Co, and Ni)-Cr Nanoparticles for Next-Generation Magnetic Applications

Combining ferromagnetic-antiferromagnetic materials in nanoalloys (i.e., nanoparticles, NPs, containing more than one element) can create a diverse landscape of potential electronic structures. As a result, a number of their magnetic properties can be manipulated, such as the exchange bias between NP core and shell, the Curie temperature of nanoparticulated samples, or their magnetocaloric effect. In this work, such a family of materials (namely M-Cr NPs where M is Fe, Co, Ni, or some combination of them) is reviewed with respect to the tunability of their magnetic properties via optimized doping with Cr up to its solubility limit. To this end, gas-phase synthesis has proven a most effective method, allowing excellent control over the physical structure, composition, and chemical ordering of fabricated NPs by appropriately selecting various deposition parameters. Recent advances in this field (both experimental and computational) are distilled to provide a better understanding of the underlying physical laws and point toward new directions for cutting-edge technological applications. For each property, a relevant potential application is associated, such as memory cells and recording heads, induced hyperthermia treatment, and magnetic cooling, respectively, aspiring to help connect the output of fundamental and applied research with current real-world challenges.

Bioinspired magnetic cilia: from materials to applications

Microscale and nanoscale cilia are ubiquitous in natural systems where they serve diverse biological functions. Bioinspired artificial magnetic cilia have emerged as a highly promising technology with vast potential applications, ranging from soft robotics to highly precise sensors. In this review, we comprehensively discuss the roles of cilia in nature and the various types of magnetic particles utilized in magnetic cilia; additionally, we explore the top-down and bottom-up fabrication techniques employed for their production. Furthermore, we examine the various applications of magnetic cilia, including their use in soft robotics, droplet and particle control systems, fluidics, optical devices, and sensors. Finally, we present our conclusions and the future outlook for magnetic cilia research and development, including the challenges that need to be overcome and the potential for further integration with emerging technologies.

Vaporization-Controlled Energy Release Mechanisms Underlying the Exceptional Reactivity of Magnesium Nanoparticles

Magnesium nanoparticles (NPs) offer the potential of high-performance reactive materials from both thermodynamic and kinetic perspectives. However, the fundamental energy release mechanisms and kinetics have not been explored due to the lack of facile synthetic routes to high-purity Mg NPs. Here, a vapor-phase route to surface-pure, core-shell nanoscale Mg particles is presented, whereby controlled evaporation and growth are utilized to tune particle sizes (40-500 nm), and their size-dependent reactivity and energetic characteristics are evaluated. Extensive in situ characterizations shed light on the fundamental reaction mechanisms governing the energy release of Mg NP-based energetic composites across particle sizes and oxidizer chemistries. Direct observations from in situ transmission electron microscopy and high-speed temperature-jump/time-of-flight mass spectrometry coupled with ignition characterization reveal that the remarkably high reactivity of Mg NPs is a direct consequence of enhanced vaporization and Mg release from their high-energy surfaces that result in the accelerated energy release kinetics from their composites. Mg NP composites also demonstrate mitigated agglomeration and sintering during reaction due to rapid gasification, enabling complete energy extraction from their oxidation. This work expands the compositional possibilities of nanoscale solid fuels by highlighting the critical relationships between metal volatilization and oxidative energy release from Mg NPs, thus opening new opportunities for strategic design of functional Mg-based nanoenergetic materials for tunable energy release.

Aptamers functionalized hybrid nanomaterials for algal toxins detection and decontamination in aquatic system: Current progress, opportunities, and challenges

Purification and detection of algal toxins is the most effective technique to ensure that people have clean and safe drinking water. To achieve these objectives, various state-of-the-art technologies were designed and fabricated to decontaminate and detect algal toxins in aquatic environments. Amongst these technologies, aptamer-functionalized hybrid nanomaterials conjugates have received significant consideration as a result of their several benefits over other methods, such as good controllable selectivity, low immunogenicity, and biocompatibility. Because of their excellent properties, aptamer-functionalized hybrid nanomaterials conjugates are one of several remarkable agents. Several isolated aptamer sequences for algal toxins are addressed in this review, as well as aptasensor and decontamination aptamer functionalized metal nanoparticle-derived hybrid nanocomposites applications. In addition, we present diverse aptamer-functionalized hybrid nanomaterial conjugates designs and their applications for sensing and decontamination.

Modelling and simulation of field directed linear assembly of aerosol particles

Unlike liquid phase colloidal assembly, significantly changing the structure of fractal aggregates in the aerosol phase, is considered impractical. In this study, we discuss the possibility of applying external magnetic and electric fields, to tune the structure and fractal dimension (D_f) of aggregates grown in the aerosol phase. We show that external fields can be used to induce dipole moments in primary nanoparticles. We found that an ensemble of particles with induced dipole moments will interact through directional attractive and repulsive forces, leading to the formation of linear, chain-like aggregates with D_f ~ 1. The aggregate structure transition is dependent on the primary particle sizes, temperature and applied field strength which was evaluated by performing a hybrid ensemble/cluster-cluster aggregation Monte Carlo simulation. We demonstrate that the threshold magnetic field strength required to linearly assemble 10-500 nm particle sizes are practically achievable whereas the electric field required to assemble sub-100 nm particles are beyond the breakdown strength of most gases. To theoretically account for the enhanced coagulation rates due to attractive interactions, we have also derived a correction factor to both free molecular and transition regime coagulation kernel, based on magnetic dipolar interactions. A comparison has been made between the coagulation time-scales estimated by theory and simulation, with the estimated magnetization time-scales of the primary particles along with oscillation time period of the magnetic field, to demonstrate that sub-50 nm superparamagnetic primary particles can be magnetized and assembled at any temperature, while below the Curie temperature ferromagnetic particles of all sizes can be magnetized and assembled, given the applied field is higher than the threshold.