Nanometer Dimensions Research Articles

Magnetic skyrmions: materials, manipulation, detection, and applications in spintronic devices

Abstract Magnetic skyrmions are vortex-like spin configurations that possess nanometric dimensions, topological stability, and high controllability through various external stimuli. Since their first experimental observation in helimagnet MnSi in 2009, magnetic skyrmions have emerged as a highly promising candidate for carrying information in future high-performance, low-energy-consumption, non-volatile information storage, and logical calculation. In this article, we provide a comprehensive review of the progress made in the field of magnetic skyrmions, specifically in materials, manipulation, detection, and application in spintronic devices. Firstly, we introduce several representative skyrmion material systems, including chiral magnets, magnetic thin films, centrosymmetric materials, and Van der Waals materials. We then discuss various methods for manipulating magnetic skyrmions, such as electric current and electric field, as well as detecting them, mainly through electrical means such as the magnetoresistance effect. Furthermore, we explore device applications based on magnetic skyrmions, such as track memory, logic computing, and neuromorphic devices. Finally, we summarize the challenges faced in skyrmion research and provide future perspectives.

A 90-day oral exposure to food-grade gold at relevant human doses impacts the gut microbiota and the local immune system in a sex-dependent manner in mice

BackgroundEdible gold (Au) is commonly used as a food additive (E175 in EU) for confectionery and cake decorations, coatings and in beverages. Food-grade gold is most often composed of thin Au sheets or flakes exhibiting micro- and nanometric dimensions in their thickness. Concerns about the impact of mineral particles used as food additives on human health are increasing with respect to the particular physico-chemical properties of nanosized particles, which enable them to cross biological barriers and interact with various body cell compartments. In this study, male and female mice were exposed daily to E175 or an Au nanomaterial (Ref-Au) incorporated into food at relevant human dose for 90 days in order to determine the potential toxicity of edible gold.ResultsE175 or Ref-Au exposure in mice did not induce any histomorphological damage of the liver, spleen or intestine, nor any genotoxic effects in the colon and liver despite an apparent higher intestinal absorption level of Au particles in mice exposed to Ref-Au compared to the E175 food additive. No changes in the intestinal microbiota were reported after treatment with Ref-Au, regardless of sex. In contrast, after E175 exposure, an increase in the Firmicutes/Bacteroidetes ratio and in the abundance of Proteobacteria were observed in females, while a decrease in the production of short-chain fatty acids occurred in both sexes. Moreover, increased production of IL-6, TNFα and IL-1β was observed in the colon of female mice at the end of the 90-day exposure to E175, whereas, decreased IL-6, IL-1β, IL-17 and TGFβ levels were found in the male colon.ConclusionsThese results revealed that a 90-day exposure to E175 added to the diet alters the gut microbiota and intestinal immune response in a sex-dependent manner in mice. Within the dose range of human exposure to E175, these alterations remained low in both sexes and mostly appeared to be nontoxic. However, at the higher dose, the observed gut dysbiosis and the intestinal low-grade inflammation in female mice could favour the occurrence of metabolic disorders supporting the establishment of toxic reference values for the safe use of gold as food additive.

Acetylation of Cellulose Nanocrystals Extracted from Cotton for Drilling Fluid Application: Structural and Thermal Characterization

In petroleum exploration, cellulose derivatives such as carboxymethylcellulose (CMC) are frequently used in drilling, cementing and fracturing fluids. However, under extreme drilling conditions, these additives have limited performance. In this regard, cellulose nanocrystals particles (CNCs) which are also derived from cellulose material are a suitable candidate due to their shear thinning rheology and thixotropy properties, even at low concentrations, among so many properties thanks to their crystalline structure and their nanometric dimensions.In this work, hydrolyzed fibers from industrial cotton are acetylated using acetic anhydride and sulfuric acid as catalysts, with the aim to modify surface properties of the obtained CNCs without changing their fiber structure and morphology. FTIR analysis pointed out the acetylation success of the obtained nanocrystals whose dimensions were found to be unaltered by the modification process. SEM images of cotton nanocrystal indicate that CNCcsurface modification preserves the nanoscale dimensions of the nanoparticles. Also, TGA analysis showed thermal stability for the acetylated CNCc.

Could a Non-Cellular Molecular Interactome in the Blood Circulation Influence Pathogens' Infectivity?

We advance the notion that much like artificial nanoparticles, relatively more complex biological entities with nanometric dimensions such as pathogens (viruses, bacteria, and other microorganisms) may also acquire a biomolecular corona upon entering the blood circulation of an organism. We view this biomolecular corona as a component of a much broader non-cellular blood interactome that can be highly specific to the organism, akin to components of the innate immune response to an invading pathogen. We review published supporting data and generalize these notions from artificial nanoparticles to viruses and bacteria. Characterization of the non-cellular blood interactome of an organism may help explain apparent differences in the susceptibility to pathogens among individuals. The non-cellular blood interactome is a candidate therapeutic target to treat infectious and non-infectious conditions.

The True Nature of Tricalcium Phosphate Used as Food Additive (E341(iii))

Tricalcium phosphate (TCP) is a food additive, labeled E341(iii), used in powdered food preparation, such as baby formula. In the United States, calcium phosphate nano-objects were identified in baby formula extractions. Our goal is to determine whether the TCP food additive, as is used in Europe, can be classified as a nanomaterial. The physicochemical properties of TCP were characterized. Three different samples (from a chemical company and two manufacturers) were thoroughly characterized according to the recommendations of the European Food Safety Authority. A commercial TCP food additive was identified as actually being hydroxyapatite (HA). It presents itself in the form of particles of different shapes (either needle-like, rod, or pseudo-spherical), which were demonstrated in this paper to be of a nanometric dimension: E341(iii) is thus a nanomaterial. In water, HA particles sediment rapidly as agglomerates or aggregates over a pH of 6 and are progressively dissolved in acidic media (pH < 5) until the complete dissolution at a pH of 2. Consequently, since TCP may be considered as a nanomaterial on the European market, it raises the question of its potential persistency in the gastrointestinal tract.

Controlled Nanoplatelet Deposition of 2D Chromium Trihalide Solid Solutions

The two-dimensional (2D) chromium trihalides CrCl3, CrBr3, and CrI3 are most famous for their exotic magnetic properties when their crystals get downscaled to nanometer dimensions. One way to tune the properties of such materials and to further increase their potential utility, e.g., in spintronics, is the formation of solid solutions. Here, we present a detailed theoretical and experimental study on the synthesis and nanoplatelet growth of CrBrxCl3–x and CrBrxI3–x solid solutions. Phase pure powder was obtained by tempering the respective parent compounds at 600 and 550 °C, using additional iodine in the case of CrBrxI3–x. The dominant stacking order changes at x = 1.8 for CrBrxCl3–x while remaining similar to CrI3 for the whole CrBrxI3–x series. A consecutive chemical vapor transport from 575 → 525 °C for 2 h (CrBrxCl3–x) or 600 → 550 °C for 3 h with 0.1 mmol additional iodine (CrBrxI3–x) resulted in the deposition of high-quality nanoplatelets on a substrate with only several nanometers in height. The composition can be controlled by the choice of the starting material, since only small shifts in the anion ratio occur during the transport. The deposited CrBrxCl3–x nanoplatelets can then be easily delaminated by ultrasonication in ethanol to reduce the height even further to few-layer dimensions. These nanoplatelets could potentially be used to investigate the property changes (e.g., in terms of magnetic response) for the downscaling of these solid solutions. We further demonstrate the quality of the deposited material by transmission electron microscopy, selected area electron diffraction, and X-ray photoelectron spectroscopy. Raman spectroscopy of the solid solution series reveals a complex evolution of vibrational modes. Photoluminescence measurements on solid solution samples show emission peaks in the near-infrared energy range with the specific energy and intensity being composition and temperature dependent.

BIOSYNTHESIS OF COPPER OXIDE NANOPARTICLES AND EVALUATION OF THEIR ANTIMICROBIAL PROPERTIES

Objective: This research was carried out to synthesize and characterize copper oxide nanoparticles (CuONPs) using Vernonia amygdalina leaf extract and investigate the in vitro antimicrobial properties using clinical microbial isolates. Methods: The CuONPs were synthesized by heating a mixture of copper sulfate pentahydrate and V. amygdalina aqueous extract. The CuONPs were characterized by Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and particle size analysis. Phytochemical analysis of V. amygdalina was carried out to determine the bio-molecules that served as a reducing agent during the synthesis of CuONPs. The antimicrobial activities of CuONPs and V. amygdalina were evaluated by the agar disc diffusion method against Staphylococcus aureus, Escherichia coli, and Candida albicans. Ampicillin and fluconazole were used as reference antibacterial and antifungal agents, respectively. Results: The nanoparticles were in the nanometer dimension and exhibited significant antimicrobial activity (P<0.05) against the tested microbes. However, the standard antibacterial drug, ampicillin, showed higher antibacterial activity against S. aureus and E. coli with the inhibition zone diameter of (IZD) of 13.10±0.38 mm and 11.80±0.12 mm, respectively. Fluconazole had no antifungal activity against C. albicans while V. amygdalina demonstrated good antibacterial activity against S. aureus and E. coli but lacked antifungal activity against C. albicans. However, the combination of CuONPs and plant extract exhibited significant antifungal activity with an IZD of 10.37±0.72 mm. Conclusion: An eco-friendly, simple, reproducible, and economical CuONPs have been synthesized using V. amygdalina leaf extract. The findings indicate that CuONPs could be used as an antimicrobial agent.

Lipid Nanoparticles as Promising Carriers for mRNA Vaccines for Viral Lung Infections.

In recent years, there has been an increase in deaths due to infectious diseases, most notably in the context of viral respiratory pathogens. Consequently, the focus has shifted in the search for new therapies, with attention being drawn to the use of nanoparticles in mRNA vaccines for targeted delivery to improve the efficacy of these vaccines. Notably, mRNA vaccine technologies denote as a new era in vaccination due to their rapid, potentially inexpensive, and scalable development. Although they do not pose a risk of integration into the genome and are not produced from infectious elements, they do pose challenges, including exposing naked mRNAs to extracellular endonucleases. Therefore, with the development of nanotechnology, we can further improve their efficacy. Nanoparticles, with their nanometer dimensions, move more freely in the body and, due to their small size, have unique physical and chemical properties. The best candidates for vaccine mRNA transfer are lipid nanoparticles (LNPs), which are stable and biocompatible and contain four components: cationic lipids, ionizable lipids, polyethylene glycols (PEGs), and cholesterol, which are used to facilitate cytoplasmic mRNA delivery. In this article, the components and delivery system of mRNA-LNP vaccines against viral lung infections such as influenza, coronavirus, and respiratory syncytial virus are reviewed. Moreover, we provide a succinct overview of current challenges and potential future directions in the field.

Engineered nanoflowers, nanotrees, nanostars, nanodendrites, and nanoleaves for biomedical applications

Abstract The development of architectured nanomaterials has been booming in recent years in part due to their expanded applications in the biomedical field, such as biosensing, bioimaging, drug delivery, and cancer therapeutics. Nanomaterials exhibit a wide variety of shapes depending on both the intrinsic properties of the materials and the synthesis procedures. Typically, the large surface areas of nanomaterials improve the rate of mass transfer in biological reactions. They also have high self-ordering and assembly behaviors, which make them great candidates for various biomedical applications. Some nanomaterials have a high conversion rate in transforming the energy of photons into heat or fluorescence, thus showing promise in cancer treatment (such as hyperthermia) and bioimaging. The nanometric dimension makes them suitable for passing through the biological barriers or interacting with the natural molecules (such as DNA, protein). Nanoflowers, nanotrees, nanostars, and nanodendrites are examples of nano-sized structures, which exhibit unique geometry-dependent properties. Here we reviewed the fabrication methods, features, properties, and biomedical applications of four nano-structured materials including nanoflowers, nanotrees, nanostars, nanodendrites, and nanoleaves. We further provided our perspectives on employing these novel nanostructures as advanced functional materials for a broad spectrum of applications.

Nanoparticle toxicity may cause testicular dysfunction

Nanoparticle toxicity may cause testicular dysfunction

Electrochemical Determination of Vitamin B12 (Cyanocobalamin) using Mercury Nanodroplets Supported at Montmorillonite on a Carbon Paste Electrode (CPE)

A simple and effective electrochemical sensor for cobalt using mercury nanodroplets supported on montmorillonite (MMT) was developed. Physical analyses allowed the identification of crystalline structure, morphology, and presence of mercury structures in MMT-Hg2+ with nanometric dimensions between 3 and 11 nm. Electrochemical responses obtained by differential pulse anodic stripping voltammetry (DPASV) using carbon paste electrode modified with montmorillonite decorated with mercury nanodroplets (CPEM-MT-Hg) toward cobalt (II) provide a limit of detection (LOD) of 3.4 × 10−6 mol L−1, limit of quantification (LOQ) of 1.1 × 10−5 mol L−1, and a linear dynamic range (LDR) from 3.5 × 10−5 to 2.9 × 10−4 mol L−1. The developed method was applied to the determination of cobalt ions in a commercial vitamin B12 sample.

A Sol-Gel/Solvothermal Synthetic Approach to Titania Nanoparticles for Raman Thermometry.

The accurate determination of the local temperature is one of the most important challenges in the field of nanotechnology and nanomedicine. For this purpose, different techniques and materials have been extensively studied in order to identify both the best-performing materials and the techniques with greatest sensitivity. In this study, the Raman technique was exploited for the determination of the local temperature as a non-contact technique and titania nanoparticles (NPs) were tested as nanothermometer Raman active material. Biocompatible titania NPs were synthesized following a combination of sol-gel and solvothermal green synthesis approaches, with the aim of obtaining pure anatase samples. In particular, the optimization of three different synthesis protocols allowed materials to be obtained with well-defined crystallite dimensions and good control over the final morphology and dispersibility. TiO2 powders were characterized by X-ray diffraction (XRD) analyses and room-temperature Raman measurements, to confirm that the synthesized samples were single-phase anatase titania, and using SEM measurements, which clearly showed the nanometric dimension of the NPs. Stokes and anti-Stokes Raman measurements were collected, with the excitation laser at 514.5 nm (CW Ar/Kr ion laser), in the temperature range of 293-323 K, a range of interest for biological applications. The power of the laser was carefully chosen in order to avoid possible heating due to the laser irradiation. The data support the possibility of evaluating the local temperature and show that TiO2 NPs possess high sensitivity and low uncertainty in the range of a few degrees as a Raman nanothermometer material.

Shape-memory effect in twisted ferroic nanocomposites

The shape recovery ability of shape-memory alloys vanishes below a critical size (~50 nm), which prevents their practical applications at the nanoscale. In contrast, ferroic materials, even when scaled down to dimensions of a few nanometers, exhibit actuation strain through domain switching, though the generated strain is modest (~1%). Here, we develop freestanding twisted architectures of nanoscale ferroic oxides showing shape-memory effect with a giant recoverable strain (>8%). The twisted geometrical design amplifies the strain generated during ferroelectric domain switching, which cannot be achieved in bulk ceramics or substrate-bonded thin films. The twisted ferroic nanocomposites allow us to overcome the size limitations in traditional shape-memory alloys and open new avenues in engineering large-stroke shape-memory materials for small-scale actuating devices such as nanorobots and artificial muscle fibrils.

Influence of water based binary composite nanofluids on thermal performance of solar thermal technologies: sustainability assessments

Recent technological advances have made it possible to produce particles with nanometer dimensions that are uniformly and steadily suspended in traditional solar liquids and have enhanced the impact of thermo-physical parameters. In this research, a three-dimensional flat plate solar collector was built using a thin flat plate and a single working fluid pipe. The physical model was solved computationally under conditions of conjugated laminar forced convection in the range 500 ≤ Re ≤ 1900 and a heat flux of 1000 W/m2. Distilled water (DW) and different types of hybrid nanofluids (namely, 0.1%-Al2O3@Cu/DW, 0.1%-MWCNTs@Fe3O4/DW, 0.3%-MWCNTs@Fe3O4/DW, 0.5%-Ag@MgO/DW, 1%-Ag@MgO/DW, 1%-S1 and 1%-S2, where MWCNTs are multi-wall carbon nanotubes, S1 means 2CuO–1Cu and S2 means 1CuO–2Cu nanocomposites) were evaluated via a set of parameters. The numerical results revealed that, by increasing the working fluid velocity (the Reynolds number), the average heat transfer coefficient, pressure loss, heat gain and solar collector efficiency were increased. Meanwhile, outlet fluid temperature and flat plate surface temperature were decreased. At Re = 1900, 1%-S2 and 1%-S1 presented higher thermal performance enhancement by 44.28% and 36.72% relative to DW. Moreover, low thermal performance enhancement of 7.59% and 7.44% were reported by 0.1%-Al2O3@Cu/DW and 0.3%-MWCNTs@Fe3O4/DW, respectively.

Effect of the plasma experimental parameters on the dose and profiles of hydrogen in-diffused into the GaN/AlGaN/GaN/Si high electron mobility transistor

The structures of electronic devices based on GaN and its AlGaN alloys grown on foreign substrates, display a high threading dislocations concentration (TDs); 107–1011 cm-2, introducing deffects diminishing the devices predicted performances. The High Electron Mobility Transistor (HEMT) core is constituted by an AlGaN/GaN heterojunction, where the AlGaN layer, of nanometric dimensions, results on the formation of the high mobility-two-dimensional electron gas (TEG). The TEG performance might be improved by its hydrogenation, although the process can, as well, catastrophically degrade the device. Here is presented a detailed study of the effect of the hydrogenation experimental parameters: plasma power, sample temperature and duration, on its dose and distribution throughout the structure. This study found that the dose depends on the square of the plasma power, increases linearly on the hydrogenation time and slightly proportional to the sample temperature. These results shed light on how to improve the AlGaN/GaN HEMT performance.

Nanotechnology- based target drug delivery system

A nanotechnology can be described as the process of manipulating, studying, and manufacturing objects with a nanometer dimension. Through site-specific, targeted delivery of medicines, nanotechnology can benefit the treatment of chronic diseases in humans. Recent nanomedicine discoveries have led to the development of numerous outstanding drugs e.g., chemotherapeutics, biologics, immunotherapeutic, etc. The purpose of this chapter is to describe various nanocarriers that can be used to deliver therapeutic molecules.

Heat Exchange in a Contact Zone of Nanoinstrumentation with Elements of the Microsystem Technology

Theoretical studies of physical processes and phenomena in the zone of physical interaction of nanoinstruments with the surfaces of elements of microsystem technology are carried out in work. Based on the conducted research, mathematical models of energy heat exchange in the zone of physical contact of nanometric dimensions were compiled, and their analytical solution was obtained using the Fourier method of separation of variables and Goodman’s integral method. Simultaneously, the energy components of the processes in the nanocontact zone were considered. The numerical solution of the mathematical model of energy heat exchange in the zone of physical nanocontact was carried out using a software application based on the finite element method. The results were checked according to the equivalent thermal scheme to confirm the adequacy and accuracy of the obtained models. As a result, the mechanisms of energetic interaction of the nanoinstrument with the surfaces of the elements of microsystem technology devices were clarified. It is shown that the use of the proposed method of equivalent thermal circuits for the evaluation of mathematical models of the energy interaction of nanoinstruments with the surfaces of microsystem technology device elements, as well as the further study of the distribution of thermal fields in the nanocontact zone, differs from other numerical and analytical methods in terms of sufficient accuracy and speed of calculations. At the same time, it was established that the discrepancy between the results of mathematical modeling and the results obtained according to the equivalent thermal scheme does not exceed 5-8 %.

Quantum Dots: Targeted and Traceable Drug Delivery System

“Quantum dots (QD’s) are semiconductor crystals of nanometre dimensions with distinctive conductive properties determined by its size”. If the semiconductor particle area unit is created sufficiently small, quantum effects get to play. When UV light hits these conductive nanoparticles, they will emit light of varied colors and these colors will be varied by dominant the dimensions of nanoparticles. Traditional imaging models like MRI andPET are less sensitive compared to optical imaging done using QD’s which is significantly cheaper, cost-effective and shortens the time required for drug development. Earlier QD’s were cadmium based which provides it with unique photonic properties and photonic stability but because of its toxicity, it is replaced with alternative materials like germanium, silicon and carbon. The structure of QD’s contains a core that is a structural scaffold and imaging distinction agent. Small hydrophobic molecules can be embedded in between the inorganic core and amphiphilic polymer coating layer, hydrophilic agents can be immobilized in the hydrophilic end of the amphiphilic polymer through covalent and non-covalent bonds. This kind of nanostructures acts as a magic bullet that not solely identifies, binds to the targeted unhealthy cells however additionally emits detectable signals that help in the real-time tracking.

Solvent Free Twin Screw Processed Silybin Nanophytophospholipid: In Silico, In Vitro and In Vivo Insights.

Silybin (SIL) is a polyphenolic phytoconstituent that is commonly used to treat liver disorders. It is difficult to fabricate an orally delivered SIL product due to its low oral bioavailability (0.95%). Therefore, the current research focusses on the development of a novel composition of a phospholipid complex, termed as nanophytophospholipid, of SIL by employing a unique, solvent-free Twin Screw Process (TSP), with the goal of augmenting the solubility and bioavailability of SIL. The optimised SIL-nanophytophospholipid (H6-SNP) was subjected to physicochemical interactions by spectrometry, thermal, X-ray and electron microscopy. The mechanism of drug and phospholipid interaction was confirmed by molecular docking and dynamics studies. Saturation solubility, in vitro dissolution, ex vivo permeation and preclinical pharmacokinetic studies were also conducted. H6-SNP showed good complexation efficiency, with a high practical yield (80%). The low particle size (334.7 ± 3.0 nm) and positively charged zeta potential (30.21 ± 0.3 mV) indicated the immediate dispersive nature of H6-SNP into nanometric dimensions, with good physical stability. Further high solubility and high drug release from the H6-SNP was also observed. The superiority of the H6-SNP was demonstrated in the ex vivo and preclinical pharmacokinetic studies, displaying enhanced apparent permeability (2.45-fold) and enhanced bioavailability (1.28-fold). Overall, these findings indicate that not only can phospholipid complexes be formed using solvent-free TSP, but also that nanophytophospholipids can be formed by using a specific quantity of lipid, drug, surfactant, superdisintegrant and diluent. This amalgamation of technology and unique composition can improve the oral bioavailability of poorly soluble and permeable phytoconstituents or drugs.

Molecular dynamics simulation of thermal behavior of nanofluid flow in a nanochannel with Cetryltrimethylammoniu Bromide surfactant molecules

The poor heat transfer properties of the base fluid are the first effective obstacle to improving heat exchangers' efficiency. The key point of using very high conductivity of solid particles (in nanometer dimension) is hundreds of times more than common fluids in heat transfer in the composition of these fluids. Therefore, adding nanoparticles (NPs) to base fluids has been a solution to increase the heat transfer (HT) properties of common energy-carrying fluids. On the other hand, adding surfactants prevents the sedimentation and instability of NPs and improves the thermal performance of nanofluids (NF). So, this study surveyed the thermal properties of water-copper NF with/without surfactant molecules in a rectangular nanochannel using molecular dynamics (MD) simulation. Cetryltrimethylammoniu Bromide (CTAB) molecules were used as surfactants, copper structure as NPs, and water molecules as a base fluid in this simulation. In the present study, the effect of nanochannel wall temperature, copper nanoparticle (NP) size, and force field type (DREIDING, Universal Force-Field (UFF), and CHARM) on thermal conductivity (Knf) of water-copper NF were studied. The results show that as the wall temperature decreased from 80 to 30 K, Knf decreased from 0.783 to 0.753 Wm-1K−1. On the other hand, by increasing the radius of NPs from 0.5 to 2 nm, Knf and heat flux (HF) increase from 0.77 to 0.798 Wm-1K−1 and 5734 to 6352 W.m−2, respectively. One of the important purposes of researchers and engineers in various industries is to increase efficiency and reduce the systems' size. Therefore, it is expected that the results of this study will be effective in many different thermal industries.