Assessing the effect of acid and alkali treatment on a halloysite-based catalyst for dry reforming of methane.

Dry reforming of methane (DRM) has recently received wide attention owing to its outstanding performance in the reduction and conversion of CH4 and CO2 to syngas (H2 and CO). From an industrial perspective, nickel (Ni)-supported catalysts have been deemed among the most suitable catalysts for DRM owing to their low cost and high activity compared to noble metals. However, a downside of nickel catalysts is their high susceptibility to deactivation due to coke formation and sintering at high temperatures. Using appropriate supports and preparation methods plays a major role in improving the activity and stability of Ni-supported catalysts. Halloysite nanotubes (HNTs) are largely utilized in catalysis as a support for Ni owing to their abundance, low cost, and ease of preparation. The treatment of HNTs (chemical or physical) prior to doping with Ni is considered a suitable method for increasing the overall performance of the catalyst. In this study, the surface of HNTs was activated with acids (HNO3 and H2SO4) and alkalis (NaOH and Na2CO3 + NaNO3) prior to Ni doping to assess the effects of support treatment on the stability, activity, and longevity of the catalyst. Nickel catalysts on raw HNT, acid-treated HNT, and alkali-treated HNT supports were prepared via wet impregnation. A detailed characterization of the catalysts was conducted using X-ray diffraction (XRD), BET surface area analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), solid-state nuclear magnetic resonance (ssNMR), H2-temperature programmed reduction, (H2-TPR), CO2-temperature programmed desorption (CO2-TPD), and Ni-dispersion via H2-pulse chemisorption. Our results reveal a clear alteration in the structure of HNTs after treatment, while elemental mapping shows a uniform distribution of Ni throughout all the different supports. Moreover, the supports treated with a molten salt method resulted in the overall highest CO2 and CH4 conversion among the studied catalysts and exhibited high stability over 24 hours testing.

Building block 3D printing based on molecular self-assembly monolayer with self-healing properties.

The spontaneous formation of biological substances, such as human organs, are governed by different stimuli driven by complex 3D self-organization protocols at the molecular level. The fundamentals of such molecular self-assembly processes are critical for fabrication of advanced technological components in nature. We propose and experimentally demonstrate a promising 3D printing method with self-healing property based on molecular self-assembly-monolayer principles, which is conceptually different than the existing 3D printing protocols. The proposed molecular building-block approach uses metal ion-mediated continuous self-assembly of organic molecular at liquid-liquid interfaces to create 2D and 3D structures. Using this technique, we directly printed nanosheets and 3D rods using dithiol molecules as building block units.

Oxidation of Au/Ag films by oxygen plasma: phase separation and generation of nanoporosity.

The oxidation of Au/Ag alloy thin films using radio-frequency oxygen plasma was studied in this work. It was demonstrated that there is a phase separation occurring between silver and gold. In addition, it was shown that the preferential oxidation of silver resulted in a solid-state diffusion of silver toward the surface where it oxidized and formed nanoporous microspheres. The gold phase remaining in the film exhibited nanoporosity due to the injected vacancies at the metal/silver oxide interface. Based on the scanning transmission electron microscopy analysis coupled with energy dispersive X-ray mapping a mechanism was proposed based on solid-state diffusion and the Kirkendall effect to explain the different steps occurring during the oxidation process.

Internalization of Metal-Organic Framework Nanoparticles in Human Vascular Cells: Implications for Cardiovascular Disease Therapy.

Abstract: Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Alteration of endothelial cells and the underlying vasculature plays a central role in the pathogenesis of various CVDs. The application of nanoscale materials such as nanoparticles in biomedicine has opened new horizons in the treatment of CVDs. We have previously shown that the iron metal-organic framework nanoparticle, Materials Institut Lavoisier-89 (nanoMIL-89) represents a viable vehicle for future drug delivery of pulmonary arterial hypertension. In this study, we have assessed the cellular uptake of nanoMIL-89 in pulmonary artery endothelial and smooth muscle cells using microscopy imaging techniques. We also tested the cellular responses to nanoMIL-89 using molecular and cellular assays. Microscopic images showed cellular internalization of nanoMIL-89, packaging into endocytic vesicles, and passing to daughter cells during mitosis. Moreover, nanoMIL-89 showed anti-inflammatory activity without any significant cytotoxicity. Our results indicate that nanoMIL-89 formulation may offer promising therapeutic opportunities and set forth a new prototype for drug delivery not only in CVDs, but also for other diseases yet incurable, such as diabetes and cancer.

Polysulfone Membranes Embedded with Halloysites Nanotubes: Preparation and Properties.

In the present study, nanocomposite ultrafiltration membranes were prepared by incorporating nanotubes clay halloysite (HNTs) into polysulfone (PSF) and PSF/polyvinylpyrrolidone (PVP) dope solutions followed by membrane casting using phase inversion method. Characterization of HNTs were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and thermogravimetric (TGA) analysis. The pore structure, morphology, hydrophilicity and mechanical properties of the composite membranes were characterized by using SEM, water contact angle (WCA) measurements, and dynamic mechanical analysis. It was shown that the incorporation of HNTs enhanced hydrophilicity and mechanical properties of the prepared PSF membranes. Compared to the pristine PSF membrane, results show that the total porosity and pore size of PSF/HNTs composite membranes increased when HNTs loadings were more than 0.5 wt % and 1.0 wt %, respectively. These findings correlate well with changes in water flux of the prepared membranes. It was observed that HNTs were homogenously dispersed within the PSF membrane matrix at HNTs content of 0.1 to 0.5 wt % and the PSF/HNTs membranes prepared by incorporating 0.2 wt % HNTs loading possess the optimal mechanical properties in terms of elastic modulus and yield stress. In the case of the PSF/PVP matrix, the optimal mechanical properties were obtained with 0.3 wt % of HNTs because PVP enhances the HNTs distribution. Results of bovine serum albumin (BSA) filtration tests indicated that PSF/0.2 wt % HNTs membrane exhibited high BSA rejection and notable anti-fouling properties.

Self-Healing Performance of Multifunctional Polymeric Smart Coatings.

Multifunctional nanocomposite coatings were synthesized by reinforcing a polymeric matrix with halloysite nanotubes (HNTs) loaded with corrosion inhibitor (NaNO3) and urea formaldehyde microcapsules (UFMCs) encapsulated with a self-healing agent (linseed oil (LO)). The developed polymeric nanocomposite coatings were applied on the polished mild steel substrate using the doctor's blade technique. The structural (FTIR, XPS) and thermogravimetric (TGA) analyses reveal the loading of HNTs with NaNO3 and encapsulation of UFMCs with linseed oil. It was observed that self-release of the inhibitor from HNTs in response to pH change was a time dependent process. Nanocomposite coatings demonstrate decent self-healing effects in response to the external controlled mechanical damage. Electrochemical impedance spectroscopic analysis (EIS) indicates promising anticorrosive performance of novel nanocomposite coatings. Observed corrosion resistance of the developed smart coatings may be attributed to the efficient release of inhibitor and self-healing agent in response to the external stimuli. Polymeric nanocomposite coatings modified with multifunctional species may offer suitable corrosion protection of steel in the oil and gas industry.

Microstructure degradation of Ni/CGO anodes for solid oxide fuel cells after long operation time using 3D reconstructions by FIB tomography.

Solid oxide fuel cells (SOFCs) are electrochemical conversion devices, which essentially consist of two porous electrodes separated by a dense, oxide ion conducting electrolyte. The performance and the durability of SOFCs strongly depend on the electrode microstructure. In this paper, the impact of a relatively long exposure time (up to 20 000 h) under realistic operation terms (temperature (T) = 850 °C, current density (J) = 190-250 mA cm-2) in the kinetics of microstructural degradation are investigated for porous nickel (Ni)/ceria gadolinium oxide (CGO) anodes, to understand the microstructural evolution in SOFC cermet anodes. A combined system of Focused Ion Beam (FIB) and Scanning Electron Microscope (SEM) tomography was used to analyze various anode microstructures aged during different operating times (2500 h, 15 000 h and 20 000 h). The methodologies of image acquisition as well as the segmentation and the object recognition were improved, offering a reliable quantification of Ni-grain growth, connectivity, tortuosity factor and triple phase boundary length (TPBL). The representative volume element (RVE) was also studied, and its dependence on aging time was confirmed. To construct a volume that can be accurate and representative for the whole sample, the necessary corresponding 3D reconstruction size was adjusted by increasing operating time, in order to suppress the influence of microstructure variation caused by Ni and CGO agglomeration. Statistically significant 3D microstructural changes were observed in the anode by increasing the operating time, including nickel particle size distribution, changes in connectivity of the ceramic part (CGO) and a significant decrease of contiguous triple phase boundary densities. Additional qualitative observations were done in order to gain a complete insight of the degradation phenomena in nickel based cermet anodes.