Nanometer Range Research Articles

Microstructural study with enhanced dielectric and magnetic properties of M−type Nd doped Ba1-xNdxFe12O19 (x = 0–0.20) hexaferrites synthesized via sol–gel auto-combustion route

In the present study, we have examined the influence of Nd doping on the structural, morphological, magnetic, and dielectric properties of barium hexaferrite (Ba1-xNdxFe12O19; 0 ≤ x ≤ 0.20) samples synthesized via the sol–gel auto-combustion route. The XRD patterns confirm the formation of the hexagonal phase, in addition to minor traces of Fe2O3 impurity in the samples. Doping with Nd3+ ions produced strain in the crystal, and the samples retain their hexagonal phase with space group P63/mmc, as ensured by the Rietveld refinement method. FTIR spectroscopy were performed for microstructural analysis, which shows the corresponding stretching and bending bands of iron and oxygen in the samples. The Raman spectra confirmed the Raman fundamental modes at various wavenumbers, which also confirm the hexagonal structure of the samples. The electronic states of all metal ions state were confirmed through x-ray photoelectron (XPS) spectroscopy analysis, which show that iron is present in two oxidation states (Fe2+ and Fe3+) in all the prepared samples. XPS spectra also revealed that the Nd-doped sample is more defective as compared to pure sample. Scanning electron microscopy (SEM) micrographs shows that the non-uniform particle size in the nanometer range. Elemental composition is confirmed using energy dispersive x-ray spectroscopy (EDS) measurement. Additionally, magnetic measurements using a vibrating sample magnetometer (VSM) revealed that the hysteresis loops for 5 % Nd-doped sample shows the maximum value 44.3 emu/g of magnetization, and its values decrease for further increase in Nd doping concentration. The dielectric measurements were performed at room temperature in the frequency range of 1 Hz to 10 MHz, when Nd3+ is doped at the Ba site, it enhances the dielectric constant, dielectric loss, tangent loss, and ac conductivity of the synthesized samples.

Magnetic‐Field Induced Charge Accumulation in Scalable Magnetoelectric PVDF‐TrFE/Ni Composite Devices

AbstractThis study investigates the direct magnetoelectric effect in thin film composites comprising a 550 nm thick poly(vinylidene fluoride‐trifluoroethylene) (PVDF‐TrFE) layer spin‐coated onto a 500 µm thick Ni foil substrate. Direct measurements of charge accumulation on dot capacitors with Au top electrodes, induced by the rotation of Ni magnetization from in‐plane to out‐of‐plane orientation by an applied magnetic field, reveal pronounced magnetoelectric coupling. Polarization differences between in‐plane and out‐of‐plane magnetization states of up to (13.8 ± 0.8) × 10−4 µC cm−2 are derived from charge measurements. This corresponds to a maximum open circuit voltage difference of up to 75 ± 6 mV and a magnetoelectric coupling coefficient with respect to magnetization changes of 310 ± 27 mVA−1. Finite element simulations using COMSOL Multiphysics corroborate experimental findings, indicating near‐independence of generated polarizations and open circuit voltages when lateral capacitor dimensions are reduced into the nanometer range. Simulations of nanoscale pillar devices on rigid substrates, employing materials with optimized piezoelectric and magnetostrictive parameters, predict the potential for generating large open circuit voltage differences exceeding 2 V, highlighting the prospects of such devices for spintronic applications.

A framework for the simulation of individual glycan coordinates to analyze spatial relationships within the glycocalyx.

The glycocalyx is a dense and dynamic layer of glycosylated species that covers every cell in the human body. It plays crucial roles in various cellular processes in health and disease, such as cancer immune evasion, cancer immune therapy, blastocyst implantation, and functional attenuation of membrane protein diffusion. In addition, alterations in glycocalyx structure may play an important role in ocular surface diseases, e.g., dry eye disease. Despite the emerging importance of the glycocalyx, various aspects of its functional organization remain elusive to date. A central reason for this elusiveness is the nanoscale dimension of the glycocalyx in conjunction with its high structural complexity, which is not accessible to observation with conventional light microscopy. Recent advances in super-resolution microscopy have enabled resolutions down to the single-digit nanometer range. In order to fully leverage the potential of these novel methods, computational frameworks that allow for contextualization of the resulting experimental data are required. Here, we present a simulation-based approach to analyze spatial relationships of glycan components on the cell membrane based on known geometrical parameters. We focus on sialic acids in this work, but the technique can be adapted to any glycan component of interest. By integrating data from mass spectrometry and quantitative biological studies, these simulations aim to model possible experimental outcomes, which can then be used for further analysis, such as spatial point statistics. Importantly, we include various experimental considerations, such as labeling and detection efficiency. This approach may contribute to establishing a new standard of connection between geometrical and molecular-resolution data in service of advancing our understanding of the functional role of the glycocalyx in biology as well as its clinical potential.

Evaluation of Stability and In vitro Anti-Cancer Activity of Dihydroquercetin Nanoemulsion

Background: Dihydroquercetin (DHQ), also known as taxifolin, is a flavonoid commonly found in many plants. Dihydroquercetin has been documented to have powerful antioxidant activity and many beneficial properties for human health, especially its ability to inhibit certain types of cancer cells. However, its low solubility and bioavailability are major obstacles to biomedical applications. Moreover, DHQ is chemically unstable and quickly degrades when exposed to alkaline conditions. Objective: In the present study, a DHQ nanoemulsion formulation was prepared by Self Nano- Emulsifying Drug Delivery System (SNEDDS) technique to overcome the above disadvantages. Methods: The obtained nanoemulsion system was evaluated for its micro-properties, stability, and in vitro cytotoxic activity against some cancer cells using tetrazolium dyes (MTS assay). Results: Measurement results showed that the DHQ nanoemulsion was successfully synthesized with typical mean droplet sizes from 9 to 11 nm, and revealed excellent stability over time. Dihydroquercetin in nanoemulsion form is more stable than the non-encapsulated form, as evidenced by the maintenance of droplet size in the nanometer range when dispersed in aqueous solution for up to 48 hours. This stability is particularly pronounced in both acidic and neutral environments. In vitro experiments on cytotoxic activities against A549, Hela, and HepG2 cancer cell lines indicated that the prepared DHQ nanoemulsion effectively inhibited the growth of all these cell lines with IC50 values (μg/mL) of 8.0, 20.4, and 29.5 respectively. Conclusion: From the detailed results above, it is evident that the solubility and bioavailability of DHQ can be improved by creating its nanostructure in the form of nanoemulsions. Furthermore, the nano form of DHQ carried within stable nanoemulsions exhibited better performance in inhibiting cancer cells compared to free DHQ. Therefore, further research is required to explore the development of cancer therapeutics utilizing nano DHQ emulsions.

Investigation of Ti nanostructures via laboratory scanning-free GEXRF.

The ability to characterize periodic nanostructures in the laboratory gains more attention as nanotechnology is widely utilized in a variety of application fields. Scanning-free grazing-emission X-ray fluorescence spectroscopy (GEXRF) is a promising candidate to allow non-destructive, element-sensitive characterization of sample structures down to the nanometer range for process engineering. Adopting a complementary metal-oxide semiconductor (CMOS) detector to work energy-dispersively via single-photon detection, the whole range of emission angles of interest can be recorded at once. In this work, a setup based on a Cr X-ray tube and a CMOS detector is used to investigate two TiO2 nanogratings and a TiO2 layer sample in the tender X-ray range. The measurement results are compared to simulations of sample models based on known sample parameters. The fluorescence emission is simulated using the finite-element method together with a Maxwell-solver. In addition, a reconstruction of the sample model based on the measurement data is conducted to illustrate the feasibility of laboratory scanning-free GEXRF as a technique to non-destructively characterize periodic nanostructures in the tender X-ray range.

Formulasi dan Karakterisasi Nanopartikel Ekstrak Biji Carica (Carica pubescens) dengan Variasi Konsentrasi Kitosan menggunakan Metode Gelasi Ionik

Carica seeds (Carica pubescens) contain alkaloid, saponin, and flavonoid compounds, which have pharmacological activities such as antibacterial, anti-inflammatory, immunomodulatory, and antihyperlipidemic properties, but their bioavailability is low. Nanotechnology has significantly advanced in drug delivery systems because it can enhance absorption in the gastrointestinal tract, allowing entry into the bloodstream. This study aims to create and evaluate the characteristics of carica seed extract nanoparticles with varying concentrations of chitosan. The carica seed extract was obtained using the maceration method with 70% ethanol as the solvent. The Carica seed extract was then formulated into nanoparticles using the ionic gelation method with varying concentrations of chitosan: NaTPP, specifically formulas FA (0.3:1), FB (0.2:1), and FC (0.1:1). The resulting nanoparticle colloids were characterized for particle size, polydispersity index (PDI), percent transmittance (%T), and specific functional groups. The results showed that the particle sizes for formulas FA, FB, and FC were 243.7 nm, 47.96 nm, and 116.6 nm, respectively. The PDI values for formulas FA, FB, and FC were 0.378, 0.357, and 0.52, respectively. The percent transmittance for all three formulas ranged from 99.5% to 99.6%. The characterization of functional groups indicated interactions between the carica seed extract, chitosan, and NaTPP, with the presence of OH, N-H, aliphatic CH, P=O, and PO3 groups. These interactions were observed based on the shift in wavenumbers in the FTIR results for each sample. All carica seed nanoparticle formulas showed particle sizes within the nanometer range (<1000 nm), polydispersity indices less than 1, percent transmittance close to 100%, and specific functional groups indicating interactions between the extract and the coating polymer. Formula FB was the optimal formula, with the smallest nanoparticle size (<100 nm), a PDI value of <0.5, and a percent transmittance of >99%.

Nano-Coating Loaded With Leaf and Flowers of Pelargonium graveolens Plant Extract Stabilized With Fenugreek Seed Gum and Soy Protein Isolate in Increasing the Shelf Life of Mutton Fillet.

In this study, the extract of leaf and flower of Pelargonium graveolens was obtained using an ultrasonic-assisted extraction method. The extraction yield and the content of phenolic, flavonoid, and flavonol compounds in the flower extract were higher (13.93%, 74.97 mg GAE g DM-1, 31.93 mg QE g DM-1, and 9.08 mg QEE g DM-1) than leaf extract (10.69%, 67.46 mg GAE g DM-1, 23.04 mg QE g DM-1, and 11.34 mg QEE g DM-1). Both extracts demonstrated antioxidant properties in tests involving the scavenging of DPPH radicals and the ferric reduction assay. Extracts exhibited antimicrobial properties. MIC of flower extract against Staphylococcus aureus and Escherichia coli were 2500 and 5000, while MBC of leaf extract were 15,000, and 20,000 ppm, respectively. The concentration of 2000 ppm of extracts was encapsulated in fenugreek seed gum (FSG) and soy protein isolate (SPI) produced by the emulsification method. All nano-coatings exhibited a nanometric size range between 172.75 to 255.21 nm, and encapsulation efficiency higher than 80.0% (80.82% to 89.59%). The application of nano-coatings significantly reduced microbial counts and delayed lipid oxidation in mutton meat during 12 days of cold storage at 4°C, enhancing meat quality and extending shelf life. The inclusion of bioactive compounds like polyphenols in the coatings contributed to antimicrobial and antioxidant effects, decreasing pH levels and preventing spoilage. The findings indicated that the combination of edible FSG and SPI as wall materials with 2000 ppm of P. graveolens extract demonstrated efficacy in implementation bacterial growth and lipid oxidation in fresh mutton meat.

Sustainable encapsulation of bio-active agents and microorganisms in electrospun nanofibers: A comprehensive review

Nanotechnology is a technological discipline focused on the design, fabrication, and utilization of structures, systems, and devices through the manipulation of atoms and molecules at the nanoscale. A significant advancement in this field is the development of a nanocarrier system for microbe encapsulation using electrospun nanofibers. These nanofibers, characterized by their diameters in the nanometric range, are produced through nanotechnology. The electrospinning technique is a versatile method that fabricates these nanofibers from polymer solutions, including polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide, polyethylene glycol, and chitosan, using high voltage. Nanofibers play a crucial role in various fields, including environmental remediation, medicine, agriculture, and textiles. Beneficial microorganisms are microbial cells that aid crops by protecting them from pathogens, supplying essential nutrients, and alleviating both biotic and abiotic stresses. Several techniques have been developed to encapsulate microorganisms within nanofibers, with electrospinning being the most widely applied method. This technique effectively traps microbial cells while preserving their viability for extended periods without causing harm. Microorganisms such as bacteria, fungi, and viruses, as well as fertilizers, pesticides, and growth hormones, can be successfully encapsulated within nanofibers. This review provides a comprehensive overview of nanofibers, including their characterization, the polymers utilized (such as chitosan, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polyethylene glycol (PEG), and alginate), and the electrospinning process with its variations. It also discusses techniques for encapsulating microbial cells within nanofibers and their applications in agriculture in the current context.

Tackling Biofilm Resistance of Gram-Positive and Gram-Negative Bacteria Against Levofloxacin via Nanotechnology and Essential Oils

Abstract Introduction The generation of biofilms by bacteria has become a major factor in the rise of antibiotic resistance. Lipid nano-capsules (LNCs) have recently emerged as an innovative platform for drug delivery, due to their unique properties and ability to carry a wide array of therapeutic chemical compounds. Objectives The objective of this research was to create, optimize, and evaluate the antibiofilm efficacy of a peppermint oil emulsion (o/w) containing levofloxacin against resistant bacteria via biofilm formation. Methods Essential oils, particularly peppermint oil known for its antifungal properties, were employed instead of traditional medium chain triglycerides to formulate lipid nanocarriers, utilizing alternating surfactant types (Solutol HS 15 and Cremophor EL) and differing oil to surfactant ratios (2:1 and 1:1). The LFX-LNCs formula, with a 2:1 oil to surfactant ratio, was selected for further investigation due to its physical properties, including particle size, zeta potential, transmission electron microscopy, and polydispersity index. The antibacterial efficiency of LFX-LNCs was evaluated, revealing their ability to eradicate established biofilms of Gram-negative pathogens, including Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), as well as Gram-positive strains such as Staphylococcus aureus (S. aureus). Results The mean particle size of LFX-LNCs varied from 30.86 ± 0.54 nm to 68.36 ± 0.56 nm, demonstrating a narrow size distribution, a negative zeta potential (-1.56 ± 0.24 to -20.2 ± 2.15 mV), and a polydispersity index (PDI) ranging from 0.062 ± 0.006 to 0.26 ± 0.002. Lipid nanocapsules generally exhibit a spherical morphology within the nanometric size range when analyzed by transmission electron microscopy (TEM). The antimicrobial activity assessment revealed that EL 2:1 exhibited the most significant antimicrobial efficacy, characterized by a reduced particle size and an inhibition zone measuring up to (2.43 ± 0.24 cm), demonstrating promising results against several pathogenic strains, including P. aeruginosa, S. aureus, and E. coli. Conclusion This study illustrates the efficacy of LFX-LNCs in the treatment of non-healing wounds infected with biofilm-forming bacteria. Graphical Abstract

Frequency and time domain 19F ENDOR spectroscopy: role of nuclear dipolar couplings to determine distance distributions.

19F electron-nuclear double resonance (ENDOR) spectroscopy is emerging as a method of choice to determine molecular distances in biomolecules in the angstrom to nanometer range. However, line broadening mechanisms in 19F ENDOR spectra can obscure the detected spin-dipolar coupling that encodes the distance information, thus limiting the resolution and accessible distance range. So far, the origin of these mechanisms has not been understood. Here, we employ a combined approach of rational molecular design, frequency and time domain ENDOR methods as well as quantum mechanical spin dynamics simulations to analyze these mechanisms. We present the first application of Fourier transform ENDOR to remove power broadening and measure T2n of the 19F nucleus. We identify nuclear dipolar couplings between the fluorine and protons up to 14 kHz as a major source of spectral broadening. When removing these interactions by H/D exchange, an unprecedented spectral width of 9 kHz was observed suggesting that, generally, the accessible distance range can be extended. In a spin labeled RNA duplex we were able to predict the spectral ENDOR line width, which in turn enabled us to extract a distance distribution. This study represents a first step towards a quantitative determination of distance distributions in biomolecules from 19F ENDOR.

Fast and large refractive index switching of optically isotropic liquid crystal films

ABSTRACT Polymer Dispersed Liquid Crystals (PDLCs) consist of low molecular weight liquid crystal (LC) droplets embedded in a polymer matrix. Nano-PDLCs are a special type of PDLCs where the LC droplet sizes are in the nanometre range. For normal incidence of light, the nano-PDLC has a voltage dependent, isotropic refractive index that could be used to make polarisation independent tunable lenses. Here, we report the effect of chiral dopant on haze, switching time and field-induced variation of the refractive index δn E of PDLC materials having a high birefringence ( Δn = 0.38 at 550 nm ) nematic liquid crystal dispersed in a polymer matrix. As an effect of the chiral dopant, δn decreases slightly from 0.05 to 0.037 at E = 10 V / μm , however the relaxation time and the haze decrease to a much larger extent from 2.5 ms to 0.3 m s, and from 50% to less than 10% at 550 nm, respectively. These improvements are due to the sub-micrometer helical pitch in the LC droplets that reduces the size of the LC droplets well below 1 µm, leading to nano-PDLC with sub-millisecond switching time and low haze.

A Compressive Review on Formulation and Evaluation of Herbal Niosomes containing Phaseolus vulgaris and zingiber officinale for the Treatment of Diabetes Mellitus

This study aimed to formulate and evaluate niosomes containing Phaseolus vulgaris (PV) and Zingiber officinale (ZO) for their antidiabetic activity. Niosomes, non-ionic surfactant vesicles, were prepared using PV and ZO extracts via the thin-film hydration method. The formulations were characterized for particle size, morphology, entrapment efficiency, and in vitro release profile. Antidiabetic activity was assessed through in vitro α-amylase inhibition assay and glucose uptake studies using differentiated 3T3-L1 adipocytes. The formulated niosomes exhibited a mean particle size within the nanometer range, indicating their suitability for drug delivery. Morphological examination revealed spherical vesicles with uniform size distribution. Entrapment efficiency of the bioactive constituents from PV and ZO extracts was found to be satisfactory. In vitro release studies demonstrated sustained release profiles over time, indicative of controlled drug delivery potential. Antidiabetic activity assessment revealed significant α-amylase inhibition by the niosomal formulations compared to free extracts. Furthermore, glucose uptake studies demonstrated enhanced glucose uptake by 3T3-L1 adipocytes treated with niosomes containing PV and ZO extracts compared to untreated cells.

Electrospinning of annatto-loaded cellulose acetate scaffolds using acetone/DMSO as solvent

Abstract Electrospinning has emerged as a versatile technique for producing nanofibers for diverse applications. The fibers produced are highly regarded for their biocompatibility, exceptional surface-to-volume ratios, porosity, and adjustable composition properties, making them promising scaffolds for tissue engineering. In the literature, annatto-loaded cellulose acetate has already been successfully used for electrospinning. However, N,N-dimethylformamide (DMF) was utilized as a solvent in the experiments, which is considered a carcinogenic and mutagenic substance. The aim of this study is to analyze whether comparable results can be achieved with a low toxicity solvent consisting of acetone and dimethyl sulfoxide (DMSO). In this study, we investigate the electrospinning process of cellulose acetate (CA) and cellulose acetate combined with annatto extract (CA/A). Initially, various polymer concentrations ranging from 12% to 16% (w/v) were characterized by rheological measurements to determine their suitability for electrospinning. The morphology and diameter distribution of the electrospun fibers were analyzed using scanning electron microscopy (SEM). Contact angle measurements were carried out to determine the wettability of the electrospun meshes. The rheological investigations conducted revealed that increasing the polymer content of CA raises viscosity, while the incorporation of annatto decreases it. Uniform fibers are achieved at polymer concentrations of 14% and above. The electrospun nanofibers exhibit uniform morphology and diameters in the nanometer range, indicating the successful fabrication of annatto-loaded CA nanofibers. The contact angle measurements showed hydrophilic behavior on all investigated meshes. The incorporation of annatto extract in the electrospun fibers holds promise for various applications, including biomedical scaffolds, scaffolds for cultured meat, filtration membranes and food packaging materials. This study provides valuable insights into optimizing electrospinning parameters for the fabrication of functional nanofibers with enhanced properties.

Enhanced Remediation of Textile Dyes via Nonmetal-Modified Layered Graphitic Carbon Nitride: Influence of Various Oxygen Precursors

Layered two-dimensional (2D) graphitic carbon nitride (gCN)) doped with nonmetals has been extensively utilized as a photo-electrocatalyst. Herein, gCN doped with Oxygen was synthesized through a thermal polymerization process. The effect of various oxygen forerunners, namely citric acid (CA), oxalic acid (OX), and lactic acid (LA) on the photocatalytic ability of the gCN was analyzed. The proposed O-doped gCN samples basic characteristics were characterized by different analytical analyses. Indeed, the O-gCN has formed a sheet-like nature with a nanometre range, so often called a nanosheet. Superior photocatalytic performance was measured when the gCN was prepared by the CA as the O-precursor; 95% malachite green (MG) removal was attained within a short treatment time of 40min by adding a 20mg photocatalyst. The influences of different parameters of catalyst concentration, different precursors, and initial pH of MG degradation were also studied. The generation of active radicals played a major part in the degradation of the MG dye solution. These findings offer fundamental insight into utilizing the O-gCN for the remediation of textile effluents in water resources. The preparation of enormous metal-free catalysts via non-metal doping toward the environmental clean-up.

Investigation of Single-Crystal Process for Ni-Rich Layered Oxides Cathode through Solid State Reaction

Processing of Ni-rich NMC layered oxide cathodes commonly adopt the co-precipitation technique. As a result, very uniform oxide particles in nano-meter range are obtained. However, NMC micro-cracks tend to form in these so-called polycrystals due to volume changes after repeated hundreds of charge/discharge cycles.In recent years, layered oxides developed by a single-crystal process has received great attention. Ni-rich layered oxides with µm-size grain size tend to give better cycling performance with enhanced structural integrity and less volume change during extended cycling tests. Single-crystal process, in fact, involves heating/calcination of oxide/carbonates/nitrates powder compacts. Accordingly, reactions such as decomposition, chemical reactions, diffusion, oxidation, sintering, grain-growth take place as well. Processing parameters such as temperatures and atmosphere play important roles on the grain growth of Ni- rich layered oxides. Furthermore, the lithiation/oxidation of Ni-containing oxides during single-crystal processing may involve charge compensation resulted from defect reactions. During the different stages of processing, the structural, microstructural and electrical properties of decomposed precursors and resultant layered oxides will be examined using XRD, SEM and DC/AC impedance measurements. CV and charge/discharge tests from assembled coin cells will be used to evaluate electrochemical properties of single-crystal Ni-rich layered oxides.

(Invited) Advanced Virtual Sigesn Substrates for the Monolithic Integration of Novel Opto- and Nanoelectronics

In the past three decades, the ternary alloy semiconductor SiGeSn has evolved from a predicted direct semiconductor to a serious candidate for the realization of a myriad of interesting applications. The fields of application vary from novel transistor concepts 1–4 for up-coming processor generations to the already reported electrically pumped heterostructure laser diode 5–7, the last missing key component for the monolithically integrated optical on-chip communication on Si.This rise of SiGeSn originates mainly due to its ability of decoupling its bandgap from its lattice-constant by what it is predestined for the epitaxy of strain-reduced heterostructures and thus their monolithic integration on Si using the well-established Ge virtual substrate technology 8.However, utilizing the lattice-matching on Ge limits the epitaxy of strain-reduced heterostructures to an extremely narrow composition range of SiGeSn, for which a constant concentration ratio of Si to Sn of 3.67 needs to be fulfilled. In addition, the composition ranges of the more desirable direct bandgap SiGeSn require lattice-constants which are much larger than that of Ge, and thus a GeSn virtual substrate. Therefore, unlocking an even larger composition range necessitates a reliable technology for complete strain-relaxation of GeSn.However, up to this day, the complete strain-relaxation of GeSn proves itself quite challenging due to its limited thermal budget. In the case of chemical vapour deposition (CVD) based epitaxy, only partial relaxation occurs during growth, while the complete strain-relaxation is limited to post-growth methods like clearance etching for the strain relief of the resulting free-standing structures. Besides that, during the low-temperature molecular beam epitaxy (MBE) of GeSn, there is insufficient thermal energy for the formation of misfit dislocations. Therefore, MBE grown GeSn structures are typically pseudomorphic or show a very small degree of strain-relaxation. Nevertheless, various approaches, like post-growth annealing (PGA) have been investigated and reported to achieve partial relaxation up to 89 % 9. On top of that, partially relaxed GeSn buffers typically exhibit a surface roughness in the range of a few nanometres which is disadvantageous for high-performance heterostructures with individual layer thicknesses of a few tens of nanometres. A possible approach to counteract this problem is the introduction of surface smoothening steps such as using chemical mechanical polishing (CMP).In this work, we report the development of a combined fabrication scheme of MBE, PGA and CMP to achieve a GeSn double layer buffer stack with a final Sn concentration of 10 %, almost complete strain-relaxation and a surface roughness of ≈ 1.7 nm. A schematic overview of the process and the involved corresponding layer stacks is shown in Fig. 1a.All shown epitaxy experiments were performed in a 6” MBE system, where Si, Ge and Sn are used as matrix materials and B and Sb as dopants, respectively. In order to stabilize the Sn segregation in the low-temperature growth regime of SiGeSn at TS ≤ 200 °C, the substrate temperature is precisely measured and controlled in-situ using mid-infrared pyrometry 10.The development of the GeSn virtual substrates is based on the well-reported Ge virtual substrate on Si(001) 8, followed by an additional 100 nm thick Ge buffer layer. For the actual GeSn virtual substrate, a 400 nm thick GeSn layer with 6% Sn underwent PGA in a rapid thermal annealing system, subsequent to its growth. To achieve a best possible growth interface, a CMP step was used afterwards to smoothen the surface. Atomic force microscopy images of a final strain-relaxed GeSn virtual substrate with and without CMP are compared in Fig. 1b, where a nice cross-hatch pattern can be seen for the sample with CMP. The crucial step is then the growth continuation, which necessitates the effective removal of the native GeSn oxide. For this, a combination of wet etching via hydrogen chloride and a following in-situ soft thermal desorption at TS = 300 °C has proven itself as best solution 11. A final 400 nm thick GeSn layer with 10 % Sn completes the GeSn virtual substrate. This virtual substrate forms then the basis for the subsequent device growth, with the layer stack shown in Fig. 1c, and their fabrication using standard cleanroom processes, as described in an earlier report 11. The current voltage characteristics of an exemplary device with a diameter of 4 µm in Fig. 1d proves a good device functionality.Alongside to the latest results on the current development of GeSn virtual substrates using MBE, we provide an overview of past and future approaches for the realization of virtual SiGeSn substrates and their suitability for monolithically integrated SiGeSn heterostructures on Si. Figure 1

Effect of Micro- and Mesopore Size on Electronic Structure and Oxygen Reduction Kinetics of Platinum

Introduction Oxygen reduction reaction is an indispensable electrochemical reaction to utilize hydrogen or renewable energy in the form of electrochemical devices, i.e., fuel cells or metal-air batteries. However, the reaction overpotential, or activation and concentration overpotentials, must be reduced to raise its expected role in energy conversion. While porous electrodes contribute to decreasing the activation overpotential owing to their high surface area, the effect of pore structure on the reaction kinetics has not been clarified. It is expected that the electronic structures of electrocatalysts change when the pore size is in the range of a few nanometers. In our recent report, we fabricated platinum model electrodes with a uniform pore size of 1.8 nm and controlled electrode thicknesses.1 The intrinsic ORR kinetics was obtained by using a thin model electrode, and the extract activation overpotential was smaller than that of a planar platinum electrode. Herein, to further elucidate the relationship between the pore structure and the ORR kinetics, we present the effect of pore sizes using the platinum model electrodes with controlled pore sizes of 1.3 nm, 1.8 nm, and 3.0 nm (inset in Figure). Our study indicates that the d-band center is shifted downward with decreasing pore size and that ORR kinetics follows a volcano relationship with a maximum at a pore size of 1.8 nm. Experimental Platinum model electrodes were fabricated with the electrodeposition of platinum salt dissolved in a liquid crystalline phase of surfactant.2 The pore diameter was controlled by varying the chain length of the surfactants. The electrode thickness was assumed to be short (~50 nm) enough to mitigate the ORR concentration overpotential.1 Transmission electron microscopy (TEM) was employed to observe the pore structure. The electronic structures of the electrodes were characterized with angle-resolved X-ray photoelectron spectroscopy (ARXPS). The photoelectron takeoff angle was changed to distinguish the local electronic structure of the pore wall from that of the outer surface. Electrochemical measurements were carried out by cyclic voltammetry in N2/O2-saturated 0.1 mol dm–3 KOH solutions with a rotating disk electrode system. Results and discussion The model electrodes exhibited characteristic redox peaks of platinum polycrystalline facets in N2-saturated solution. ORR activities were evaluated in the Tafel plot (Figure), where current densities were normalized by electrochemical surface area and corrected for mass transport. It was found that the activation overpotential was the lowest at a pore size of 1.8 nm. Furthermore, the obtained Tafel slope (ca. –60 mV dec–1) was almost the same, suggesting that the rate-determining step is the same and the concentration activation overpotential is small among the electrodes.1 In ARXPS, the binding energy of the Pt 4f7/2 spectrum exhibited a high energy shift with a decrease in the pore size. The result suggests that the d-band center of platinum is shifted downward with decreasing pore size,3 and that the enhanced ORR kinetics at a pore size of 1.8 nm is attributed to the appropriate adsorption energy of the electrode to oxygen-containing species.4 We will also report the results collected in acidic solutions.

Assessment of Sub-micrometer-Sized Particles with Practical Activities in an Underground Coal Mine

This assessment was designed to explore and characterize the airborne particles, especially for the sub-micrometer sizes, in an underground coal mine. Airborne particles present in the breathing zone were evaluated by using both (1) direct reading real-time instruments (RTIs) to measure real-time particle number concentrations in the workplaces and (2) gravimetric samplers to collect airborne particles to obtain mass concentrations and conduct further characterizations. Airborne coal mine particles were collected via three samplers: inhalable particle sampler (37 mm cassette with polyvinyl chloride (PVC) filter), respirable dust cyclone (10 mm nylon cyclone with 37 mm Zefon cassette and PVC filter), and a Tsai diffusion sampler (TDS). The TDS, a newly designed sampler, is for collecting particles in the nanometer and respirable size range with a polycarbonate filter and grid. The morphology and compositions of collected particles on the filters were characterized using electron microscopy (EM). RTIs reading showed that the belt entry had a greatly nine-times higher total particle number concentration in average (~ 34,700 particles/cm3) than those measured at both the underground entry and office building (~ 4630 particles/cm3). The belt entry exhibited not only the highest total particle number concentration, but it also had different particle size fractions, particularly in the submicron and smaller sizes. A high level of submicron and nanoparticles was found in the belt conveyor drift area (with concentrations ranging from 0.54 to 1.55 mg/m3 among three samplers). The data support that small particles less than 300 nm are present in the underground coal mine associated with dust generated from practical mining activities. The chemical composition of the air particles has been detected in the presence of Ca, Cu, Si, Al, Fe, and Co which were all found to be harmful to miners when inhaled.

Nanotechnological advancement for the treatment of neurodegenerative disorders

Neurodegenerative disorders are chronic and progressive conditions of the central nervous system. This review work focusses on some of the disorders like Alzheimer’s disease, Parkinson’s disease, Amyotrophic lateral sclerosis, and Huntington’s disease which are some of the most prevalent neurodegenerative disorders presenting a substantial challenge on the global health care system. These disorders are characterized by the loss of neurons and the formation of protein aggregates leading to cognitive and motor impairments. The treatment options are available but due to the complex pathophysiology of the disease and the intricate structure of the brain, effective concentrations of drugs are not delivered to brain. Here we discuss some of the recent strategies employed by scientists to enhance the drug delivery and drug targeting to the site of action that is brain for these disorders. Further, nanotechnology-based carrier systems have been discussed which are developed using different natural and synthetic polymers and lipid materials. Owing to many beneficial properties like nanometric size range, physicochemical properties and tunable surface-modifying features, nanocarriers serve as potential systems in the treatment of neurodegenerative diseases as they can easily cross the BBB and reach to the brain in effective concentration. This review article describes neurodegenerative disorders and the limitations associated with their conventional application. Different arrays of nanocarriers such as polymeric nanoparticles, liposomes, Solid Lipid Nanoparticles, Nanostructured Lipid Carriers, and Nanoemulsions have been extensively reviewed. To understand the nanomedicine market, the ongoing clinical trials for various nano-carriers employed to treat these disorders have been compiled and discussed.

Comparing the Efficacies of Electrospun ZnO and TiO2 Nanofibrous Interlayers for Electron Transport in Perovskite Solar Cells

ZnO and TiO2 are both well-known electron transport materials. Their comparison of performance is considered advantageous and novel. Therefore, a viable electrospinning route was considered for the development of highly polycrystalline TiO2 and ZnO nanofibers as an electron transport material (ETM) for perovskite solar cells. The materials were well-characterized in terms of different analytical techniques. The X-ray diffraction detected polycrystalline structural properties corresponding to TiO2 and ZnO. Morphological analysis by scanning electron microscopy revealed that the nanofibers are long, uniform, and polycrystalline, having a diameter in the nanometer range. Optoelectronic properties showed that TiO2 and ZnO exhibit absorption values in the ultraviolet and visible ranges, and band gap values for TiO2 and ZnO were 3.3 and 3.2 eV, respectively. TiO2 bandgap and semiconductor nature were more compatible with Electron Transport Layer (ETL) compared to ZnO. Electrical studies revealed that TiO2 nanofibers have enhanced values of conductivity and sheet carrier mobility compared to ZnO nanofibers. Therefore, higher photovoltaic conversion efficiency was achieved for TiO2 nanofibers (10.4%) compared to ZnO (8.5%).