Natural aluminosilicate nanotubes loaded with RuCo as nanoreactors for Fischer-Tropsch synthesis

Following nanoarchitectural approach, mesoporous halloysite nanotubes with internal surface composed of alumina were loaded with 5-6 nm RuCo nanoparticles by sequential loading/reduction procedure. Ruthenium nanoclusters were loaded inside clay tube by microwave-assisted method followed by cobalt ions electrostatic attraction to ruthenium during wetness impregnation step. Developed nanoreactors with bimetallic RuCo nanoparticles were investigated as catalysts for the Fischer-Tropsch process. The catalyst with 14.3 wt.% of Co and 0.15 wt.% of Ru showed high activity (СO conversion reached 24.6%), low selectivity to methane (11.9%), CO₂ (0.3%), selectivity to C₅₊ hydrocarbons of 79.1% and chain growth index (α) = 0.853. Proposed nanoreactors showed better selectivity to target products combined with high activity in comparison to the similar bimetallic systems supported on synthetic porous materials. It was shown that reducing agent (NaBH₄ or H₂) used to obtain Ru nanoclusters at first synthesis step played a very important role in the reducibility and selectivity of resulting RuCo catalysts.

Organic modification of layered zirconium phosphate/phosphonate for controlled release of therapeutic inorganic ions

The present study aims to develop a layered zirconium phosphate/phosphonate (LZP) powder to control the release of therapeutic inorganic ions. Organically modified LZPs were successfully prepared with various contents of phenyl groups via a reflux method in an aqueous solution containing phosphoric and phenylphosphonic acids. Powder X-ray diffraction analysis and Fourier transform infrared spectroscopy revealed that the crystal structure of the synthesized LZP samples was identical to that of α-zirconium phosphate, even after modification. The amount of incorporated organic molecules increased with increasing molar fractions of phenylphosphonic acid in the starting composition, as determined from the thermal analysis. Cobalt ion (Co2+), a type of therapeutic inorganic ion, was incorporated into the organically modified LZP through treatment with an acetonitrile solution containing tetrabutylammonium ions, followed by treatment with an acetonitrile solution containing CoCl2. The amount of incorporated Co2+ depended on the concentration of the phenyl groups. Furthermore, the highest amount of Co2+ was incorporated in the sample (ZP-Ph-0.5) prepared with equimolar phosphoric/phenylphosphonic acid. The ZP-Ph-0.5 sample additionally showed the ability to incorporate copper or iron ions (Cu2+ or Fe3+). The incorporated ion, either Co2+ or Cu2+, was continuously released from the ZP-Ph-0.5 sample in a saline solution over a period of three weeks, whereas the release of Fe3+ was negligible. The quantity of Co2+ released was higher than that of Cu2+. The controlled release of Co2+ from the ZP-Ph-0.5 sample was also observed in a simulated body fluid that mimicked the ionic concentration of human blood plasma. These results confirm that a specific degree of phenyl modification makes LZP a candidate host material for releasing therapeutic inorganic ions.

Current approaches for the exploration of antimicrobial activities of nanoparticles

Infectious diseases of bacterial and viral origins contribute to substantial mortality worldwide. Collaborative efforts have been underway between academia and the industry to develop technologies for a more effective treatment for such diseases. Due to their utility in various industrial applications, nanoparticles (NPs) offer promising potential as antimicrobial agents against bacterial and viral infections. NPs have been established to possess potent antimicrobial activities against various types of pathogens due to their unique characteristics and cell-damaging ability through several mechanisms. The recently accepted antimicrobial mechanisms possessed by NPs include metal ion release, oxidative stress induction, and non-oxidative mechanisms. Another merit of NPs lies in the low likelihood of the development of microbial tolerance towards NPs, given the multiple simultaneous mechanisms of action against the pathogens targeting numerous gene mutations in these pathogens. Moreover, NPs provide a fascinating opportunity to curb microbial growth before infections: this outstanding feature has led to their utilization as active antimicrobial agents in different industrial applications, e.g. the coating of medical devices, incorporation in food packaging, promoting wound healing and encapsulation with other potential materials for wastewater treatment. This review discusses the progress and achievements in the antimicrobial applications of NPs, factors contributing to their actions, mechanisms underlying their efficiency, and risks of their applications, including the antimicrobial action of metal nanoclusters (NCs). The review concludes with a discussion of the restrictions on present studies and future prospects of nanotechnology-based NPs development.

Alkyl-capped copper oxide nanospheres and nanoprolates for sustainability: water treatment and improved lubricating performance

Metal oxide nanoparticles of different nature have been used in different fields such as therapeutics, biomarkers, tribology or environmental remediation, among others. Besides, the surface modification of such nanoparticles is of particular interest to bring designed functions. In this paper we describe the synthesis of CuO nanoparticles with two different geometries (spherical and prolate) and decorated with long alkyl chains in order to use as dye removers by adsorption and/or photo-degradation of a persistent model dye (Congo Red) and as lubricant additives to improve the tribological performance of base lubricant oils. Alkyl-functionalized CuO nanoparticles demonstrated a high stability in oily suspensions and an improvement in the friction reducing the CoF ca. 26%; the alkyl-decorated nanoparticles showed also higher adsorption kinetics for Congo Red than the neat ones following a pseudo-second-order trend, although with lower adsorption efficiency. The synthesis, surface modification and physic-chemical characterization of spherical and prolate CuO nanoparticles are described as well as their applications as lubricant additives and Congo Red photocatalytic removal.

Study of local intracellular signals regulating axonal morphogenesis using a microfluidic device

The establishment and maintenance of axonal patterning is crucial for neuronal function. To identify the molecular systems that operate locally to control axonal structure, it is important to manipulate molecular functions in restricted subcellular areas for a long period of time. Microfluidic devices can be powerful tools for such purposes. In this study, we demonstrate the application of a microfluidic device to clarify the function of local Ca²⁺ signals in axons. Membrane depolarization significantly induced axonal branch-extension in cultured cerebellar granule neurons (CGNs). Local application of nifedipine using a polydimethylsiloxane (PDMS)-based microfluidic device demonstrated that Ca²⁺ entry from the axonal region via L-type voltage-dependent calcium channels (L-VDCC) is required for branch extension. Furthermore, we developed a method for locally controlling protein levels by combining genetic techniques and use of a microfluidic culture system. A vector for enhanced green fluorescent protein (EGFP) fused to a destabilizing domain derived from E. coli dihydrofolate reductase (ecDHFR) is introduced in neurons by electroporation. By local application of the DHFR ligand, trimethoprim (TMP) using a microfluidic device, we were able to manipulate differentially the level of fusion protein between axons and somatodendrites. The present study revealed the effectiveness of microfluidic devices to address fundamental biological issues at subcellular levels, and the possibility of their development in combination with molecular techniques.

Towards a metadata scheme for the description of materials - the description of microstructures

The property of any material is essentially determined by its microstructure. Numerical models are increasingly the focus of modern engineering as helpful tools for tailoring and optimization of custom-designed microstructures by suitable processing and alloy design. A huge variety of software tools is available to predict various microstructural aspects for different materials. In the general frame of an integrated computational materials engineering (ICME) approach, these microstructure models provide the link between models operating at the atomistic or electronic scales, and models operating on the macroscopic scale of the component and its processing. In view of an improved interoperability of all these different tools it is highly desirable to establish a standardized nomenclature and methodology for the exchange of microstructure data. The scope of this article is to provide a comprehensive system of metadata descriptors for the description of a 3D microstructure. The presented descriptors are limited to a mere geometric description of a static microstructure and have to be complemented by further descriptors, e.g. for properties, numerical representations, kinetic data, and others in the future. Further attributes to each descriptor, e.g. on data origin, data uncertainty, and data validity range are being defined in ongoing work. The proposed descriptors are intended to be independent of any specific numerical representation. The descriptors defined in this article may serve as a first basis for standardization and will simplify the data exchange between different numerical models, as well as promote the integration of experimental data into numerical models of microstructures. An HDF5 template data file for a simple, three phase Al-Cu microstructure being based on the defined descriptors complements this article.

Enhanced cellular uptake of lactosomes using cell-penetrating peptides

Polymeric micelles that are composed of synthetic polymers are generally size controllable and can be easily modified for various applications. Lactosomes (A₃B-type) are biodegradable polymeric micelles composed of an amphipathic polymer, including three poly(sarcosine) blocks and a poly(l-lactic acid) block. Lactosomes accumulate in tumors in vivo through the enhanced permeability and retention (EPR) effect, even on frequently administering them. However, lactosomes cannot be efficiently internalized by cells. To improve cellular uptake of lactosomes, cell-penetrating peptide (CPP)-modified lactosomes were prepared. Seven CPPs (including EB1 and Pep1) were used, and most of them improved the cellular uptake efficiency of lactosomes. In particular, EB1- and Pep1-modified lactosomes were efficiently internalized by cells. In addition, by using CPP-modified and photosensitizer-loaded lactosomes, we demonstrated the photoinduced killing of mammalian cells, including human cancer cells. Accumulation of the EB1-modified lactosomes in NCI-N87 tumors was shown by in vivo imaging. Thus, this study demonstrated that the CPP-modified lactosome is a promising drug carrier.

Growth condition dependence of unintentional oxygen incorporation in epitaxial GaN

Growth conditions have a tremendous impact on the unintentional background impurity concentration in gallium nitride (GaN) synthesized by molecular beam epitaxy and its resulting chemical and physical properties. In particular for oxygen identified as the dominant background impurity we demonstrate that under optimized growth stoichiometry the growth temperature is the key parameter to control its incorporation and that an increase by 55 °C leads to an oxygen reduction by one order of magnitude. Quantitatively this reduction and the resulting optical and electrical properties are analyzed by secondary ion mass spectroscopy, photoluminescence, capacitance versus voltage measurements, low temperature magneto-transport and parasitic current paths in lateral transistor test structures based on two-dimensional electron gases. At a growth temperature of 665 °C the residual charge carrier concentration is decreased to below 10¹⁵ cm^-3, resulting in insulating behavior and thus making the material suitable for beyond state-of-the-art device applications.

Experimental study and modeling of atomic-scale friction in zigzag and armchair lattice orientations of MoS2

Physical properties of two-dimensional materials, such as graphene, black phosphorus, molybdenum disulfide (MoS₂) and tungsten disulfide, exhibit significant dependence on their lattice orientations, especially for zigzag and armchair lattice orientations. Understanding of the atomic probe motion on surfaces with different orientations helps in the study of anisotropic materials. Unfortunately, there is no comprehensive model that can describe the probe motion mechanism. In this paper, we report a tribological study of MoS₂ in zigzag and armchair orientations. We observed a characteristic power spectrum and friction force values. To explain our results, we developed a modified, two-dimensional, stick-slip Tomlinson model that allows simulation of the probe motion on MoS₂ surfaces by combining the motion in the Mo layer and S layer. Our model fits well with the experimental data and provides a theoretical basis for tribological studies of two-dimensional materials.

Luminescence of delafossite-type CuAlO2 fibers with Eu substitution for Al cations

CuAlO₂ has been examined as a potential luminescent material by substituting Eu for Al cations in the delafossite structure. CuAlO₂:Eu³⁺ nanofibers have been prepared via electrospinning for the ease of mitigating synthesis requirements and for future optoelectronics and emerging applications. Single-phase CuAlO₂ fibers could be obtained at a temperature of 1100 °C in air. The Eu was successfully doped in the delafossite structure and two strong emission bands at ~405 and 610 nm were observed in the photoluminescence spectra. These bands are due to the intrinsic near-band-edge transition of CuAlO₂ and the f-f transition of the Eu³⁺ activator, respectively. Further electrical characterization indicated that these fibers exhibit semiconducting behavior and the introduction of Eu could act as band-edge modifiers, thus changing the thermal activation energies. In light of this study, CuAlO₂:Eu³⁺ fibers with both strong photoluminescence and p-type conductivity could be produced by tailoring the rare earth doping concentrations.

Room-temperature synthesis of three-dimensional porous ZnO@CuNi hybrid magnetic layers with photoluminescent and photocatalytic properties

A facile synthetic approach to prepare porous ZnO@CuNi hybrid films is presented. Initially, magnetic CuNi porous layers (consisting of phase separated CuNi alloys) are successfully grown by electrodeposition at different current densities using H2 bubbles as a dynamic template to generate the porosity. The porous CuNi alloys serve as parent scaffolds to be subsequently filled with a solution containing ZnO nanoparticles previously synthesized by sol-gel. The dispersed nanoparticles are deposited dropwise onto the CuNi frameworks and the solvent is left to evaporate while the nanoparticles impregnate the interior of the pores, rendering ZnO-coated CuNi 3D porous structures. No thermal annealing is required to obtain the porous films. The synthesized hybrid porous layers exhibit an interesting combination of tunable ferromagnetic and photoluminescent properties. In addition, the aqueous photocatalytic activity of the composite is studied under UV-visible light irradiation for the degradation of Rhodamine B. The proposed method represents a fast and inexpensive approach towards the implementation of devices based on metal-semiconductor porous systems, avoiding the use of post-synthesis heat treatment steps which could cause deleterious oxidation of the metallic counterpart, as well as collapse of the porous structure and loss of the ferromagnetic properties.

Electrical and photo-electrical properties of MoS2 nanosheets with and without an Al2O3 capping layer under various environmental conditions

The electrical and photo-electrical properties of exfoliated MoS₂ were investigated in the dark and in the presence of deep ultraviolet (DUV) light under various environmental conditions (vacuum, N₂ gas, air, and O₂ gas). We examined the effects of environmental gases on MoS₂ flakes in the dark and after DUV illumination through Raman spectroscopy and found that DUV light induced red and blue shifts of peaks (E¹_2 g and A_1 g) position in the presence of N₂ and O₂ gases, respectively. In the dark, the threshold voltage in the transfer characteristics of few-layer (FL) MoS₂ field-effect transistors (FETs) remained almost the same in vacuum and N₂ gas but shifted toward positive gate voltages in air or O₂ gas because of the adsorption of oxygen atoms/molecules on the MoS₂ surface. We analyzed light detection parameters such as responsivity, detectivity, external quantum efficiency, linear dynamic range, and relaxation time to characterize the photoresponse behavior of FL-MoS₂ FETs under various environmental conditions. All parameters were improved in their performances in N₂ gas, but deteriorated in O₂ gas environment. The photocurrent decayed with a large time constant in N₂ gas, but decayed with a small time constant in O₂ gas. We also investigated the characteristics of the devices after passivating by Al₂O₃ film on the MoS₂ surface. The devices became almost hysteresis-free in the transfer characteristics and stable with improved mobility. Given its outstanding performance under DUV light, the passivated device may be potentially used for applications in MoS₂-based integrated optoelectronic circuits, light sensing devices, and solar cells.