Self-Propelled Aero-GaN Based Liquid Marbles Exhibiting Pulsed Rotation on the Water Surface.

We report on self-propelled rotating liquid marbles fabricated using droplets of alcoholic solution encapsulated in hollow microtetrapods of GaN with hydrophilic free ends of their arms and hydrophobic lateral walls. Apart from stationary rotation, elongated-spheroid-like liquid marbles were found, for the first time, to exhibit pulsed rotation on water surfaces characterized by a threshold speed of rotation, which increased with the weight of the liquid marble while the frequency of pulses proved to decrease. To throw light upon the unusual behavior of the developed self-propelled liquid marbles, we propose a model which takes into account skimming of the liquid marbles over the water surface similar to that inherent to flying water lily beetle and the so-called helicopter effect, causing a liquid marble to rise above the level of the water surface when rotating.

Highly Porous and Ultra-Lightweight Aero-Ga2O3: Enhancement of Photocatalytic Activity by Noble Metals.

A new type of photocatalyst is proposed on the basis of aero-ß-Ga2O3, which is a material constructed from a network of interconnected tetrapods with arms in the form of microtubes with nanometric walls. The aero-Ga2O3 material is obtained by annealing of aero-GaN fabricated by epitaxial growth on ZnO microtetrapods. The hybrid structures composed of aero-Ga2O3 functionalized with Au or Pt nanodots were tested for the photocatalytic degradation of methylene blue dye under UV or visible light illumination. The functionalization of aero-Ga2O3 with noble metals results in the enhancement of the photocatalytic performances of bare material, reaching the performances inherent to ZnO while gaining the advantage of the increased chemical stability. The mechanisms of enhancement of the photocatalytic properties by activating aero-Ga2O3 with noble metals are discussed to elucidate their potential for environmental applications.

Aero-Ga2O3 Nanomaterial Electromagnetically Transparent from Microwaves to Terahertz for Internet of Things Applications.

In this paper, fabrication of a new material is reported, the so-called Aero-Ga2O3 or Aerogallox, which represents an ultra-porous and ultra-lightweight three-dimensional architecture made from interconnected microtubes of gallium oxide with nanometer thin walls. The material is fabricated using epitaxial growth of an ultrathin layer of gallium nitride on zinc oxide microtetrapods followed by decomposition of sacrificial ZnO and oxidation of GaN which according to the results of X-ray diffraction (XRD) and X-ray photoemission spectroscopy (XPS) characterizations, is transformed gradually in ß-Ga2O3 with almost stoichiometric composition. The investigations show that the developed ultra-porous Aerogallox exhibits extremely low reflectivity and high transmissivity in an ultrabroadband electromagnetic spectrum ranging from X-band (8-12 GHz) to several terahertz which opens possibilities for quite new applications of gallium oxide, previously not anticipated.

Mesenchymal stem cells proliferation and remote manipulation upon exposure to magnetic semiconductor nanoparticles.

In this paper, we report on spatial redistribution of bone marrow mesenchymal stem cells loaded with magnetic nanoparticles under the influence of continuously applied magnetic field. Semiconductor nanoparticles were synthesized by epitaxial growth of a GaN thin layer on magnetic sacrificial core consisting of ZnFe2O4 nanoparticles. Different quantities of nanoparticles were incubated in vitro with mesenchymal stem cells. High density of nanoparticles (50 µg/ml) leads to a decrease in the number of cells during incubation, while the density of nanoparticles as low as 10 µg/ml is enough to drag cells in culture and rearrange them according to the spatial distribution of the magnetic field intensity.

Advanced Hybrid GaN/ZnO Nanoarchitectured Microtubes for Fluorescent Micromotors Driven by UV Light.

The development of functional microstructures with designed hierarchical and complex morphologies and large free active surfaces offers new potential for improvement of the pristine microstructures properties by the synergistic combination of microscopic as well as nanoscopic effects. In this contribution, dedicated methods of transmission electron microscopy (TEM) including tomography are used to characterize the complex hierarchically structured hybrid GaN/ZnO:Au microtubes containing a dense nanowire network on their interior. The presence of an epitaxially stabilized and chemically extremely stable ultrathin layer of ZnO on the inner wall of the produced GaN microtubes is evidenced. Gold nanoparticles initially trigger the catalytic growth of solid solution phase (Ga1- x Znx )(N1- x Ox ) nanowires into the interior space of the microtube, which are found to be terminated by AuGa-alloy nanodots coated in a shell of amorphous GaOx species after the hydride vapor phase epitaxy process. The structural characterization suggests that this hierarchical design of GaN/ZnO microtubes could offer the potential to exhibit improved photocatalytic properties, which are initially demonstrated under UV light irradiation. As a proof of concept, the produced microtubes are used as photocatalytic micromotors in the presence of hydrogen peroxide solution with luminescent properties, which are appealing for future environmental applications and active matter fundamental studies.

Electromagnetic interference shielding in X-band with aero-GaN.

We investigate the electromagnetic shielding properties of an ultra-porous lightweight nanomaterial named aerogalnite (aero-GaN). Aero-GaN is made up of randomly arranged hollow GaN microtetrapods, which are obtained by direct growth using hydride vapor phase epitaxy of GaN on the sacrificial network of ZnO microtetrapods. A 2 mm thick aero-GaN sample exhibits electromagnetic shielding properties in the X-band similar to solid structures based on metal foams or carbon nanomaterials. Aero-GaN has a weight four to five orders of magnitude lower than the weight of metals.

Targeting Endothelial Cells with Multifunctional GaN/Fe Nanoparticles.

In this paper, we report on the interaction of multifunctional nanoparticles with living endothelial cells. The nanoparticles were synthesized using direct growth of gallium nitride on zinc oxide nanoparticles alloyed with iron oxide followed by core decomposition in hydrogen flow at high temperature. Using transmission electron microscopy, we demonstrate that porcine aortic endothelial cells take up GaN-based nanoparticles suspended in the growth medium. The nanoparticles are deposited in vesicles and the endothelial cells show no sign of cellular damage. Intracellular inert nanoparticles are used as guiding elements for controlled transportation or designed spatial distribution of cells in external magnetic fields.

Viability and proliferation of endothelial cells upon exposure to GaN nanoparticles.

Nanotechnology is a rapidly growing and promising field of interest in medicine; however, nanoparticle-cell interactions are not yet fully understood. The goal of this work was to examine the interaction between endothelial cells and gallium nitride (GaN) semiconductor nanoparticles. Cellular viability, adhesion, proliferation, and uptake of nanoparticles by endothelial cells were investigated. The effect of free GaN nanoparticles versus the effect of growing endothelial cells on GaN functionalized surfaces was examined. To functionalize surfaces with GaN, GaN nanoparticles were synthesized on a sacrificial layer of zinc oxide (ZnO) nanoparticles using hydride vapor phase epitaxy. The uptake of GaN nanoparticles by porcine endothelial cells was strongly dependent upon whether they were fixed to the substrate surface or free floating in the medium. The endothelial cells grown on surfaces functionalized with GaN nanoparticles demonstrated excellent adhesion and proliferation, suggesting good biocompatibility of the nanostructured GaN.

Three-dimensional Aerographite-GaN hybrid networks: single step fabrication of porous and mechanically flexible materials for multifunctional applications.

Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes. In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic, and sensors applications.