Oxide Microparticles Research Articles

Control of thermal barrier performance by optimized nanoparticle size and experimental evaluation using a solar simulator

An experimental investigation to evaluate the radiative properties of a selectively transparent thin coating on a substrate of a different material has been performed in order to evaluate its thermal behavior for applications where a low temperature at the surface exposed to the sun is desired. Copper (II) oxide (CuO) micro-particles have been used to create a pigmented coating on a paper substrate. The particle volume fraction and size have been optimized by the theoretical methodology. The spectral reflectance was measured using spectroscopy in the visible (VIS) and near-infrared (NIR) regions. The spectral emissivity was evaluated from the reflectance in IR region. The temperatures of the designed coatings and typical black paints are measured in a solar simulator. The temperature measurement was simulated by numerical analysis. The temperature of CuO coating on standard white paper was 10°C lower than the ones of typical black paint while keeping the desired dark tone.

Improvement of cell infiltration in electrospun polycaprolactone scaffolds for the construction of vascular grafts.

The less-than-ideal cell infiltration resulting from inherently small pore size limits the application of electrospinning scaffold in tissue engineering and regeneration medicine. The present study aims to develop a porogenic method which can significantly increase pore size in electrospinning scaffold and enhance cell migration. With this method, composite scaffolds consisting of poly(epsilon-caprolactone) (PCL) fibers and poly(ethylene oxide) (PEO) microparticles were prepared by simultaneously electrospinning and electrospraying. Removal of the PEO microparticles from the composites generated large pores. In vitro culture of NIH3T3 cells and in vivo subcutaneous implantation both demonstrated that the porogenic scaffolds markedly facilitated cell infiltration. With the same technique, vascular grafts with alternative dense and loose layers were prepared by turning on or off electrospraying PEO. SEM showed that there was no a clear delamination between the loose and dense layers. The mechanical strength and burst pressure of these vascular grafts could meet the requirements of vascular implantation. In conclusion, electrospinning PCL fibers with electrospraying PEO microparticles may be an effective and controllable method to increase pore size in electrospinning scaffold and provides a useful tool for the fabrication of vascular grafts that meets the need of blood vessel replacement.

Abstract 217: Use of Magnetic Resonance Imaging Method For Quantification Of Myocardial Salvage In A Rat Model Of Ischemia-reperfusion Injury.

Introduction: Quantification of myocardial “area-at-risk” (AAR) and infarct (MI) zone is critical for assessing novel therapies targeting myocardial ischemia-reperfusion (IR) injury. The current standard method involves perfusion with Evan’s Blue (EB), staining with TTC and manual slicing and analysis. We have developed an MRI method for quantifying MI and AAR in whole hearts which provides superior 3D resolution to the standard approach. Methods: Rats were given an IR injury, recovered for 24 hours then infused with Gd-DTPA via the tail vein. The coronary artery was then religated, and a solution containing both iron oxide microparticles and EB was infused. For comparison, hearts were then harvested and transversally sectioned for TTC staining. Some hearts were kept intact for MRI only analysis. Ex-vivo MRI T2* and T1 images were acquired on a 9.4T magnet. The AAR (red) was quantified by comparing the T2* signal loss in perfused regions (blue) and high T1-signal in infarcted zones (white) from Gd-DTPA retention. Results: MRI and EB/TTC measures on the same slice for both AAR and MI were highly correlated (r=0.92-0.94;p<0.05). 3D MRI acquisition and analysis of whole hearts reduced intra-observer variability, and automated segmentation and analysis further reduced inter-observer variation. Conclusion: This novel MRI technique allows precise assessment of infarct and AAR zones and is highly suited to automation of both analysis and acquisition. This method could remove the need for tissue slicing, and via a centralised MRI facility, could permit 3D digital analysis of hearts at high anatomical resolution, accessible for all laboratories already performing IR experiments.

Formation process of metallic copper fine particles from cupric oxide microparticles at room temperature.

Copper (Cu) fine particles were prepared by room-temperature hydrazine reduction of Cu oxide microparticles. In this study, to reveal the formation process of metallic Cu homogeneous fine particles from cupric oxide (CuO) microparticles, hydrazine was added to a CuO slurry at room temperature. The morphological changes in the product during the reduction with and without ammonia were observed by using scanning electron microscopy (SEM). The SEM images indicated that not only did the Cu2+ dissolve in water by complex formation with ammonia or hydrazine, but also that Cu2+ ions on the surface of CuO microparticles were reduced by hydrazine to form metallic Cu fine particles. Tuning the sizes of Cu particles by the stabilizing reagent is also discussed.

Automated quantification of myocardial salvage in a rat model of ischemia-reperfusion injury using 3D high-resolution magnetic resonance imaging (MRI).

BackgroundQuantification of myocardial “area at risk” (AAR) and myocardial infarction (MI) zone is critical for assessing novel therapies targeting myocardial ischemia–reperfusion (IR) injury. Current “gold‐standard” methods perfuse the heart with Evan's Blue and stain with triphenyl tetrazolium chloride (TTC), requiring manual slicing and analysis. We aimed to develop and validate a high‐resolution 3‐dimensional (3D) magnetic resonance imaging (MRI) method for quantifying MI and AAR.Methods and ResultsForty‐eight hours after IR was induced, rats were anesthetized and gadopentetate dimeglumine was administered intravenously. After 10 minutes, the coronary artery was re‐ligated and a solution containing iron oxide microparticles and Evan's Blue was infused (for comparison). Hearts were harvested and transversally sectioned for TTC staining. Ex vivo MR images of slices were acquired on a 9.4‐T magnet. T2* data allowed visualization of AAR, with microparticle‐associated signal loss in perfused regions. T1 data demonstrated gadolinium retention in infarcted zones. Close correlation (r=0.92 to 0.94; P<0.05) of MRI and Evan's Blue/TTC measures for both AAR and MI was observed when the combined techniques were applied to the same heart slice. However, 3D MRI acquisition and analysis of whole heart reduced intra‐observer variability compared to assessment of isolated slices, and allowed automated segmentation and analysis, thus reducing interobserver variation. Anatomical resolution of 81 μm3 was achieved (versus ≈2 mm with manual slicing).ConclusionsThis novel, yet simple, MRI technique allows precise assessment of infarct and AAR zones. It removes the need for tissue slicing and provides opportunity for 3D digital analysis at high anatomical resolution in a streamlined manner accessible for all laboratories already performing IR experiments.

The influence of TiO2 and ZnO powder mixtures on photocatalytic activity and rheological behavior of cement pastes

The photocatalytic activity of titania nano/microparticles (nT and mT) and zinc oxide microparticles (mZ) as well as the rheological behavior of cement pastes with the addition of those particles were evaluated applying design of experiments (DoE). Such additives ranged from 0 to 1.2wt.% in the cement paste, while the water/cement ratio (0.45) and superplasticizer (0.45wt.%) remained invariable. Thus, pure blends and binary or ternary mixtures were studied. Pure blends containing nT or mT and ternary mixtures 0.67mT:0.17nT:0.17mZ reached the best and comparable performances in terms of photocatalytic activity. The rheological parameters (plastic viscosity and yield stress) values changed along time in distinct levels described by a quadratic model. Samples with nT became less fluid, and the yield stress was the main rheological parameter affected. The kinetics of hydration was not significantly affected by additions up to 120min testing, but showed noticeable distinctions for longer periods: mZ (delayed) and nT (shortened), while mT required about the same time to reach the maximum exothermic peak than reference paste.

Ultra-high stability and durability of iron oxide micro- and nano-structures with discovery of new three-dimensional structural formation of grain and boundary

In this research, we have applied a facile polyol method with the addition of NaBH4 to synthesize polyhedral α-Fe2O3 oxide microparticles with the large size of 1–10μm at 200–230°C for about 25–30min. The sharp polyhedral shapes and morphologies have been formed in the good assistance of NaBH4 as versatile strong reducing agent. The sharp polyhedral and large Fe oxide microparticles exhibited a uniform characterization of size, shape and morphology with the pure α-Fe2O3 structure. To study durability and stability of the microparticles under temperature, we have rationally carried out isothermal heat treatment of the prepared α-Fe2O3 oxide microparticles at high annealing temperature about 500°C and 900–910°C for 1h. A new structure was found in the pure α-Fe2O3 particles with micro- and nano-structure co-existed with the very good formation of a three-dimensional (3D) structure with the oxide grains and the boundaries. The interesting phenomena of the deformation of surface, size, shape, and structure are discovered in α-Fe2O3 oxide microparticles by isothermal heat treatment. Apart from surface deformation, the new micro- and nano-structure of large α-Fe2O3 microparticles cannot be destroyed but they can be retained in their specific characteristics of size, shape, and morphology because of both plastic and elastic deformation co-existed. The interesting surface deformation by heat treatment is observed in comparison with the case without heat treatment. The typical magnetic properties of α-Fe2O3 microparticles were investigated in the appearance of grain and boundary. Finally, our proposal of the new technologies with particle heat treatment is very crucial to make novel micro- and nano-structures of ultra-high durability and stability with the grains and the boundaries that can be utilized in catalysis, energy and environment for future.

Relationship Between the Surface Energy and the Histologic Results of Different Titanium Surfaces

The aim of this study was to evaluate, through in vitro and in vivo studies, the existence of a relationship between surface energy, for wettability, and the clinical behavior of dental implants with different surfaces, one with a surface treated by sandblasting with titanium oxide microparticles followed by acid-etching treatment (experimental group) and another with a machined surface (control group). For the in vitro tests, a total of 30 titanium disks (15 disks for each group) were evaluated by scanning electron microscopy and dispersive energy spectroscopy and for surface roughness and wettability. For the in vivo tests, a total of 24 implants (12 implants for each group) were inserted in the tibiae of 6 rabbits and were removed after 30 and 60 days for histologic analysis. The results showed that the implants with the experimental surface presented a low wettability, and it also resulted in highly stimulated new bone formation in vivo, when compared with the control group dental implant. As for the bone formation, differences between the different surfaces seemed evident, both in quantity and in quality, as implants from the experimental group showed a higher new bone deposition than that from the control group. Thus, in vitro and in vivo tests demonstrated an excellent biologic response of the surfaces treated by sandblasting with microparticles of titanium oxide followed by acid etching.

One-step/one-pot decoration of oxide microparticles with silver nanoparticles

HypothesisHeterogeneous nucleation of silver oxide (Ag2O) onto oxide microparticles (OMPs) followed by spontaneous thermal decomposition produce nanostructures made of OMPs decorated with silver nanoparticles (OMP|AgNPs). ExperimentsColloidal chemistry methods have been used to produce the decoration of OMPs with silver nanoparticles (AgNPs), by carrying out the Ag2O precipitation/thermal decomposition. The process is driven in water enriched acetone medium containing NaOH, NH3, AgNO3 and SiO2MPs as substrate. Optical and morphological properties of OMP|AgNPs were characterized by using STEM, EDS, HRTEM and Raman spectroscopy. FindingsA new synthetic method to decorate OMPs (TiO2, SiO2) with metallic AgNPs in a single step/single pot reaction is proven effective to produce OMP|AgNPs either in aqueous or water enriched media.

Biodegradable, polymer encapsulated, metal oxide particles for MRI-based cell tracking.

Metallic particles have shaped the use of magnetic resonance imaging (MRI) for molecular and cellular imaging. Although these particles have generally been developed for extracellular residence, either as blood pool contrast agents or targeted contrast agents, the coopted use of these particles for intracellular labeling has grown over the last 20 years. Coincident with this growth has been the development of metal oxide particles specifically intended for intracellular residence, and innovations in the nature of the metallic core. One promising nanoparticle construct for MRI-based cell tracking is polymer encapsulated metal oxide nanoparticles. Rather than a polymer coated metal oxide nanocrystal of the core: shell type, polymer encapsulated metal oxide nanoparticles cluster many nanocrystals within a polymer matrix. This nanoparticle composite more efficiently packages inorganic nanocrystals, affording the ability to label cells with more inorganic material. Further, for magnetic nanocrystals, the clustering of multiple magnetic nanocrystals within a single nanoparticle enhances r2 and r2* relaxivity. Methods for fabricating polymer encapsulated metal oxide nanoparticles are facile, yielding both varied compositions and synthetic approaches. This review presents a brief history into the use of metal oxide particles for MRI-based cell tracking and details the development and use of biodegradable, polymer encapsulated, metal oxide nanoparticles and microparticles for MRI-based cell tracking.

Development of TiO2 and Au Nanocomposite Electrode as CEA Immunosensor Transducer

AbstractA carbon paste electrode (CPE) was modified by titanium(IV) oxide microparticles and then gold nanoparticles were dispersed in chitosan and immobilized on the CPE surface. As result a nanostructure modified composite electrode was obtained. Carcinoembriyonic antigen (CEA) was chosen as model analyte and the developed electrode was used as CEA immunosensor transducer for the first time. Two linear ranges of 0.01–1 ng/mL and 1–20 ng/mL with corresponding correlation coefficients R2=0.986 and R2=0.990, were found respectively. The limit of detection of the developed immunosensor was calculated as 0.01 ng/mL with 2.8 % relative standard deviation (n=5). The developed system was applied for CEA detection in synthetically prepared serum sample and very promising recovery values were obtained.

Magnetic Resonance Imaging of Single Co-Labeled Mesenchymal Stromal Cells after Intracardial Injection in Mice

The aim of this study was to establish co-labeling of mesenchymal stromal cells (MSC) for the detection of single MSC in-vivo by MRI and histological validation. Mouse MSC were co-labeled with fluorescent iron oxide micro-particles and carboxyfluorescein succinimidyl ester (CFSE). The cellular iron content was determined by atomic absorption spectrometry. Cell proliferation and expression of characteristic surface markers were determined by flow cytometry. The chondrogenic differentiation capacity was assessed. Different amounts of cells (n1 = 5000, n2 = 15 000, n3 = 50 000) were injected into the left heart ventricle of 12 mice. The animals underwent sequential MRI on a clinical 3.0 T scanner (Intera, Philips Medical Systems, Best, The Netherlands). For histological validation cryosections were examined by fluorescent microscopy. Magnetic and fluorescent labeling of MSC was established (mean cellular iron content 23.6 ± 3 pg). Flow cytometry showed similar cell proliferation and receptor expression of labeled and unlabeled MSC. Chondrogenic differentiation of labeled MSC was verified. After cell injection MRI revealed multiple signal voids in the brain and fewer signal voids in the kidneys. In the brain, an average of 4.6 ± 1.2 (n1), 9.0 ± 3.6 (n2) and 25.0 ± 1.0 (n3) signal voids were detected per MRI slice. An average of 8.7 ± 3.1 (n1), 22.0 ± 6.1 (n2) and 89.8 ± 6.5 (n3) labeled cells per corresponding stack of adjacent cryosections could be detected in the brain. Statistical correlation of the numbers of MRI signal voids in the brain and single MSC found by histology revealed a correlation coefficient of r = 0.91. The study demonstrates efficient magnetic and fluorescent co-labeling of MSC and their detection on a single cell level in mice by in-vivo MRI and histology. The described techniques may broaden the methods for in-vivo tracking of MSC. • Detection of single magnetically labeled MSC in-vivo using a clinical 3.0 T MRI is possible.• Fluorescent and magnetic co-labeling does not affect cell vitality.• The number of cells detected by MRI and histology has a high correlation.

Picosecond nonlinear optical properties of cuprous oxide with different nano-morphologies

Cuprous oxide nanoclusters, microcubes and microparticles were successfully synthesized by a simple co-precipitation method. Phase purity and crystallinity of the samples were studied by using X-ray powder diffraction. Transmission electron microscopy (TEM) images show different morphologies like nanoclusters, microcubes and microparticles. For linear and nonlinear optical measurements, the as-synthesized Cu2O with different morphologies were dispersed in isopropanol solution. The absorption spectrum recorded in the visible regions shows peaks that depend on the morphology of the particles and the peak shifts towards red region as one goes from nanoclusters to microparticles. Simple open-aperture Z-scan technique is used to measure nonlinear optical properties of cuprous oxide at 532 nm, 30 ps excitation at 10 Hz repetition rate. Cuprous oxide nanoclusters show reverse saturable absorption (RSA) behaviour, the microcubes and microparticles at a similar concentration exhibit saturable absorption (SA) type of behaviour at lower peak intensities and exhibit RSA within SA at higher peak intensities. The results show that the transition from SA to RSA can be ascribed to the two-photon absorption (TPA) process.

Enhanced thermoelectric effect of carbon fiber reinforced cement composites by metallic oxide/cement interface

Thermoelectric power of carbon fiber reinforced cement composites was firstly enhanced efficiently by metallic oxide microparticles in the cement matrix. The absolute Seebeck coefficient of these composites increased steadily with increasing metallic oxide content and achieved 4–5 folds of the original one. The largest absolute thermoelectric power of +100.28µV/°C was obtained for the composite with 5.0wt% Bi2O3 microparticles. The carrier scattering of the interface between oxide microparticles and cement matrix is probably attributed to the Seebeck effect enhancement.

One-step magnetic modification of non-magnetic solid materials

Abstract A rapid and simple method has been developed for the magnetization of non-magnetic materials. The postmagnetization procedure employs magnetic iron oxide microparticles (prepared using a microwave assisted procedure from ferrous sulphate) which are thoroughly mixed with the powder material to be modified. After drying, stable magnetically responsive materials have been formed.

3D imaging of human cells using PIXEμCT

We report imaging of human lung epithelial cells exposed to cobalt oxide ([Formula: see text]) microparticles using three-dimensional (3D) particle-induced X-ray emission microcomputed tomography ([Formula: see text]). The use of energy-selectable quasi-monochromatic low-energy X-rays generated via proton microbeam bombardment led to high-quality images. We also carried out two-dimensional (2D) micro-PIXE imaging. The 3D [Formula: see text] imaging data are complementary with 2D micro-PIXE images and the CT value ratios of the cells show that the strong absorption stems from [Formula: see text]. The 2D micro-PIXE analysis provides projection images of the elemental distribution, and this in combination with the 3D [Formula: see text] imaging revealed details of the internal distribution of [Formula: see text], and hence provides insight into the mechanisms of [Formula: see text] toxicity via intracellular perinuclear accumulation.

Electrical Properties and Phase Behavior of Proton Conducting Nanocomposites Based on the Polymer System (1 － x)[PVOH + H&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;PO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; + H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O]&amp;#183;x(Nb&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;5&amp;lt;/sub&amp;gt;)

In the present work, novel blend polymer electrolyte membranes using poly(vinyl alcohol) (PVA), doped with hypophosphorous acid (H3PO2) and reinforced with porous niobium oxide (Nb2O5) microparticles in different compositions were prepared by the solution-casting technique. Their phase behavior and ionic conductivity were studied by differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and impedance spectroscopy (IS) in the radio-frequency range. Using a constant H3PO2/PVA weigh ratio of 0.25, it was found that the water content in the blended hydrogel membranes increased with increasing the filler Nb2O5 content, thus increasing the electrical conductivity. However, the suitable weight ratio of Nb2O5:(H3PO2/PVA) for the blend performance (both mechanically and electrically) was x = 0.075, with a maximum ionic conductivity of 2.7 × 10﹣3 S·cm﹣1 at 120°C. For all blends prepared, the lost tangent plots show asymmetrical peaks, as a consequence of correlations in the mobile ion diffusion as a function of frequency. Although this “universal dynamic response” was observed at all temperatures, variations in the tan(δ) relaxation peaks indicate a decrease of ionic correlation when the temperature is increased. Both the dc conductivity and tan(δ) peaks frequency dependency are thermally activated, following an Arrhenius-type behavior with activation energy of the same order, indicating that the corresponding ionic processes have the same origin, i.e., proton jump among available sites in the polymer matrix. The additions of oxide particles to the membranes improve their thermal and electrical properties, attributed to an approximation effect.

Evolution of nanoscale morphology in single and binary metal oxide microparticles during reduction and oxidation processes

Metal oxide composites are enabling materials for many energy conversion systems such as chemical looping and photocatalysis.

The exothermic reaction route of a self-heatable conductive ink for rapid processable printed electronics

We report the exothermic reaction route and new capability of a self-heatable conductive ink (Ag2O and silver 2,2-dimethyloctanoate) in order to achieve both a low sintering temperature and electrical resistivity within a short sintering time for flexible printed electronics and display appliances. Unlike conventional conductive ink, which requires a costly external heating instrument for rapid sintering, self-heatable conductive ink by itself is capable of generating heat as high as 312 °C when its exothermic reaction is triggered at a temperature of 180 °C. This intensive exothermic reaction is found to result from the recursive reaction of the 2,2-dimethyloctanoate anion, which is thermally dissociated from silver 2,2-dimethyloctanoate, with silver oxide microparticles. Through this recursive reaction, a massive number of silver atoms are supplied from silver oxide microparticles, and the nucleation of silver atoms and the fusion of silver nanoparticles become the major source of heat. This exothermic reaction eventually realizes the electrical resistivity of self-heatable conductive ink as low as 27.5 μΩ cm within just 40 s by combining chemical annealing, which makes it suitable for the roll-to-roll printable electronics such as a flexible touch screen panel.

Synthesis of mesoporous silica oxide/C-dot complex (meso-SiO2/C-dots) using pyrolysed rice husk and its application in bioimaging

Due to the abundance of silica and carbon in rice (Oryza sativa) husk (RH), we exploited it for the synthesis of a mesoporous silica oxide micro-particles (meso-SiO2)/C-dot complex for biological imaging using a novel hot injection method commonly used for semiconductor quantum dots. Carbon dots (C-dots) with a high degree of green fluorescence were observed under UV-light they were found to be embedded to a significant extent in meso-SiO2 as confirmed by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The mesoporous nature of the complex was confirmed using N2 adsorption–desorption measurements. Surface functionalization was studied using Fourier transform infrared spectroscopy (FTIR). The synthesized meso-SiO2/C-dots complex was used for labeling yeast cells since the fungi closely represents eukaryotic organisms. Furthermore, the meso-SiO2/C-dot complex was found to be highly bio-compatible for Vero cells. This study might help in the further utilization of the complex for the theranostic application of simultaneous cellular imaging and drug delivery.