Formation Of Such Nanoparticles Research Articles

A Novel Pathway of Functional microRNA Uptake and Mitochondria Delivery.

Extracellular microRNAs (miRNAs) play a critical role in horizontal gene regulation. Uptake of extracellular miRNAs by recipient cells and their intracellular transport, however, remains elusive. Here RNA phase separation is shown as a novel pathway of miRNA uptake. In the presence of serum, synthetic miRNAs rapidly self-assembly into ≈110nm discrete nanoparticles, which enable miRNAs' entry into different cells. Depleting serum cationic proteins prevents the formation of such nanoparticles and thus blocks miRNA uptake. Different from lipofectamine-mediated miRNA transfection in which majority of miRNAs are accumulated in lysosomes of transfected cells, nanoparticles-mediated miRNA uptake predominantly delivers miRNAs into mitochondria in a polyribonucleotide nucleotidyltransferase 1(PNPT1)-dependent manner. Functional assays further show that the internalized miR-21 via miRNA phase separation enhances mitochondrial translation of cytochrome b (CYB), leading to increase in adenosine triphosphate (ATP) and reactive oxygenspecies (ROS) reduction in HEK293T cells. The findings thus reveal a previously unrecognized mechanism for uptake and delivery functional extracellular miRNAs into mitochondria.

Formation of lithium carbonate nano-particles using a massively arrayed microfluidic fiber reactor

Microfluidic-based nanoprecipitation is an important tool in modern process intensification to form nanoparticles with well controlled size, size distribution and surface properties. Lithium carbonate nanoparticles were formed continuously with controlled size distribution in the present work using a vertical microfluidic fiber contactor/reactor. The reactor operates as an industrially relevant massively arrayed microfluidic environment which can be scaled for high throughput. Lithium carbonate nanoparticles are an important intermediate for the mining, recycling and production of lithium ion for batteries, pore formers for fuel cell catalysis, and even in pharmaceuticals. Formation of such nanoparticles in a microfluidic environment has the potential for elegant control of polydispersity, and for the fiber contactor/reactor the micro-environment is massively arrayed and high throughput is simultaneously possible. Continuous microfluidic fractional precipitation of lithium carbonate nanoparticles with diameters as small as 5.9 nm is described. The solvent was a CO2-saturated water solution and the anti-solvent was isopropanol. The effects of process parameters (including temperature, surfactant concentration, antisolvent strength, and process flowrate) on product size and polydispersity were examined. In particular, lower temperatures seemed to produce low polydispersity. The product was characterized using dynamic light scattering (DLS). A computational fluid dynamics model is also presented to predict the nucleation point (along the length of the reactor) where nanoparticles were likely forming. Correlation to crystal growth mechanisms in the reactor and the importance of reactor length (Otswald versus digestive ripening) is discussed, residence time being one potential contributing factor to the low polydispersity.

Structure of Y0.75La0.25PO4·0.67H2O rhabdophane nanoparticles synthesized by the hydrothermal microwave method

Nanopowders with a rhabdophane structure of nominal composition Y0.75La0.25PO4·0.67H2O were obtained by hydrothermal-microwave synthesis. The monoclinic structure of rhabdophane was refined by the Rietveld method within the C2 (5) space group. The nanopowders were studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron microdiffraction (selected area electron diffraction, SAED), small angle X-ray scattering (SAXS), thermal analysis, low-temperature nitrogen adsorption-desorption measurements for analysis of surface area and porosity (ASAP) and pycnometric density measurements. These methods showed the formation of rod-like single-crystal rhabdophane nanoparticles with isolated pores inside the nanoparticles. To describe the formation of such nanoparticles, a mechanism of coherent-accommodative intergrowth of nanoscale clusters with rhabdophane structure is proposed.

New Insights into the Degradation Behavior of Air Electrodes during Solid Oxide Electrolysis and Reversible Solid Oxide Cell Operation

The commercialization of reversible solid oxide cells (RSOCs) is limited by the severe degradation of the air electrodes during solid oxide electrolysis cells (SOECs) operation. Herein, the degradation behavior of (La0.8Sr0.2)0.95Mn1−xCoxO3−δ (LSMC) air electrodes where x = 0.1, 0.3, and 0.5 is reported. After the SOEC test, the air electrode with x = 0.1 delaminates. While previous studies reported delamination due to the disintegration of air electrodes, for the first time, it is shown that delamination can also occur due to the disintegration of the samaria‐doped ceria (SDC) barrier layer into nanoparticles. The formation of such nanoparticles weakens the contact between the air electrode and barrier layer and encourages delamination. The air electrode with x = 0.3, shows excellent long‐term stability and also produces an electrolysis current density of 0.63 A cm−2 in 50% H2O/50% H2 at 1.3 V. This mechanistic study will allow researchers to develop air electrodes with improved long‐term stability.

Synergistic Effect of New ZrNi5/Nb2O5 Catalytic Agent on Storage Behavior of Nanocrystalline MgH2 Powders

Due to its availability and high storage capacity, Mg is an ideal material in hydrogen storage applications. In practice, doping Mg/MgH2 with catalyst(s) is necessary in enhancing the de/rehydrogenation kinetics and minimizing both of decomposition temperature and its related apparent activation energy. The present study proposed a new heterogeneous catalytic agent that consisted of intermetallic compound (ZrNi5)/metal oxide (Nb2O5) binary system for using with different concentrations (5−30 wt%) to improve MgH2. Doping MgH2 powders with low concentration (5, 7, 10 wt%) of this new catalytic system led to superior absorption/desorption kinetics, being indexed by the short time that is required to absorb/desorb 4.2−5.6 wt% H2 within 200 s to 300 s. Increasing the doping dose to 15–30 wt% led to better kinetic effect but a significant decrease in the hydrogen storage capacity was seen. The dependent of apparent activation energy and decomposition temperature of MgH2 on the concentration of ZrNi5/Nb2O5 has been investigated. They tended to be linearly decreased with increasing the catalyst concentrations. The results elucidated the crucial role of catalytic additives on the disintegration of MgH2 into ultrafine powders (196 nm to 364 nm diameter). The formation of such nanoparticles enhance the hydrogen diffusion and shorten the time that is required for the hydrogenation/dehydrogenation process. Moreover, this refractory catalytic system acted as a grain growth inhibitor, in which Mg/MgH2 powders maintained their submicron level during the cycle-life-test that was extended to 100 h at 200 °C.

Growth of Fe–Pt Magnetic Nanoparticles on Silica Particles Modified with Organic Molecules

In the present paper, we describe the formation of an assembly composed of Fe–Pt magnetic nanoparticles on a template particle. The assembly is composed of a magnetic nanoshell for core/shell particles or hollow particles for application in nanomedicine devices. For this purpose, magnetic nanoparticles should be densely accumulated or deposited on template particles, Fe–Pt nanoparticles completely cover silica template particles by modifying them with a polymer such as poly(diallyldimethylammonium chloride) (PDDA), polyethyleneimine (PEI), or poly(N-vinyl-2-pyrrolidone) (PVP) followed by the polyol reduction of Fe and Pt compounds. Studies of their morphological, crystallographic, and magnetic properties reveal that Fe–Pt nanoparticles are selectively grown on the polymer-modified silica template particles; the polymer probably supplies nucleation sites for the formation of such nanoparticles. The species of polymer used strongly affects crystallographic and magnetic properties of the nanoparticles, particularly, the atomic ordering of Fe–Pt nanoparticles formed on silica template particles.

Formation of crystalline PuO2+x·nH2O nanoparticles upon sorption of Pu(V,VI) onto hematite

It has been recognized that natural aquatic colloids can readily sorb actinide elements, including plutonium, whose behavior is complicated by its multiple valence states and the possibility of redox reactions under environmental conditions. In this paper, the sorption and surface-mediated redox transformations of hexavalent plutonium on synthetic well-characterized hematite colloids are studied in a series of batch sorption experiments. The variation in the kinetics of the Pu–hematite interactions, Pu-L3-XAFS, and HRTEM over a broad range of total concentrations of Pu have been studied in an attempt to define the molecular-level speciation of Pu. The surface-mediated slow reduction of Pu(V/VI) results in the formation of crystalline nanoparticles of PuO2+x·nH2O approximately 1.5nm in size at [Pu]tot⩾10−9M. This result is confirmed independently by HRTEM images of Pu-containing particles and through the identification in the EXAFS of a Pu neighbor shell at 3.8Å. The formation of such nanoparticles potentially influences the colloid-mediated transport of Pu in the subsurface environment because of the very slow leaching of Pu from the hematite colloids.

Anodic Film Formation on AA 2099-T8 Aluminum Alloy in Tartaric–Sulfuric Acid

The anodizing behavior of a lithium-containing aluminum alloy (AA 2099-T8) in an environmentally friendly electrolyte, namely tartaric–sulfuric acid (TSA), has been examined under potentiodynamic and potentiostatic conditions. Specifically, the dependence of the anodic film morphology and composition on the anodizing voltage was investigated. It is revealed that porous anodic films with well-defined cells were formed at relatively low voltages while porous anodic films with pores of increased dimensions and lateral porosity were formed at increased voltages. In addition, it is indicated that copper in the alloy matrix can be occluded in the anodic film material as copper-rich nanoparticles or it can be oxidized and incorporated into the film material as copper ions, depending on the anodizing voltage. In the latter case, the process is accompanied by oxygen gas generation within the film material, resulting in the lateral porosity in the anodic film. Further, the structures of the copper-rich nanoparticles have been determined and the mechanism of the formation of such nanoparticles has been discussed.

EXAFS Characterization of Dendrimer−Pt Nanocomposites Used for the Preparation of Pt/γ-Al2O3 Catalysts

Pt/gamma-Al2O3 catalysts were prepared using hydroxyl-terminated generation four (G4OH) PAMAM dendrimers as the templating agents and the various steps of the preparation process were monitored by extended X-ray absorption fine structure (EXAFS) spectroscopy. The EXAFS results indicate that, upon hydrolysis, chlorine ligands in the H(2)PtCl(6) and K(2)PtCl(4) precursors were partially replaced by aquo ligands to form [PtCl3(H2O)3]+ and [PtCl2(H2O)2] species, respectively. The results further suggest that, after interaction of such species with the dendrimer molecules, chlorine ligands from the first coordination shell of Pt were replaced by nitrogen atoms from the dendrimer interior, indicating that complexation took place. This process was accompanied by a substantial transfer of electron density from the dendrimer to platinum, indicating that the dendrimer plays the role of a ligand. Following treatment of the H(2)PtCl(6)/G4OH and K(2)PtCl(4)/G4OH complexes with NaBH4, no substantial changes were observed in the electronic or coordination environment of platinum, indicating that metal nanoparticles were not formed during this step under our experimental conditions. However, when the reduction treatment was performed with H2, the formation of extremely small platinum clusters, incorporating no more than four Pt atoms was observed. The nuclearity of these clusters depends on the length of the hydrogen treatment. These Pt species remained strongly bonded to the dendrimer. Formation of larger platinum nanoparticles, with an average diameter of approximately 10 A, was finally observed after the deposition and drying of the H(2)PtCl(6)/G4OH nanocomposites on a gamma-Al(2)O(3) surface, suggesting that the formation of such nanoparticles may be related to the collapse of the dendrimer structure. The platinum nanoparticles formed appear to have high mobility because subsequent thermal treatment in O2/H2, used to remove the dendrimer component, led to further sintering.

Perovskite barium zirconate titanate nanoparticles directly synthesized from solutions

Perovskite barium zirconate titanate nanoparticles (25–20 nm in diameter) were synthesized at low temperatures and under ambient pressure using titanium alkoxide, zirconium alkoxide and barium hydroxide as the starting materials. Microstructural analyses by X-ray diffraction and transmission electron microscopy indicated that the powders were nano-scaled, well crystallized, and had a perovskite phase. It is proposed that an acid–base neutralization reaction is the key mechanism behind the formation of such nanoparticles.