Transmission Electron Microcopy Images Research Articles

ML-assisted optimization method for the prediction of 3-dimensional fractal structures from microscopic images

Aggregated aerosol particles released from high temperature processes and combustion processes are often described as quasi-fractal aggregates, where the shape of these particles is represented by the scaling law. A detailed understanding of the morphology is quite important as various properties are strongly dependent on the particle shape. Electron microcopy based image analysis is the most commonly used technique to visualize and study the morphological features. In this study, we propose a machine learning (ML)-assisted retrieval method where ML techniques are combined with optimization algorithms to predict the morphological features and the corresponding 3-dimensional structures from microscopic images. The proposed algorithm is comprehensively tested with “synthetic” images as well as Transmission Electron Microcopy images. Various ML models, including Linear regression, Artificial Neural Network, K-nearest neighbours, Random Forest regression, and XGBoost are used for preliminary prediction of the morphological features (Number of monomers (N), fractal prefactor (kf) and fractal Dimension (Df)). These are used to narrow down the search space in the optimization algorithms. Random Forest and XGBoost methods achieved approximately 0.96 R2 score for N, 0.85 for Df and 0.73 for kf. Multiple optimization methods, including PSO, JAYA, and JAYA-SA, were tested in the study. The method was tested across a wide range of parameters, including N (up to 500), Df (1.1–2.7), and kf (0.6–2.1), and the results are quite promising while comparing various 3-dimensional properties of the retrieved structures. The retrieved fractal parameters, N and Df, exhibited errors under 10%, and the predicted kf values were found within approximately 15% using the proposed method. Results also show that the 3-dimensional properties of the predicted structure are quite close to the structures used for testing the algorithm. The algorithm was also parallelized to improve the computational time. The results show that the predicted fractal parameters and the retrieved 3-dimensional structures are quite similar to the structures used for testing across a wide range of particle morphologies. The incorporation of ML models has significantly improved the accuracy and computational speed, compared to the existing retrieval techniques.

Preparation and luminescence behaviour of perovskite LaAlO3:Tb3+ nanophosphors for innovative displays

Herein, we report the preparation, structural and luminescent behaviour of the perovskite LaAlO3:Tb3+ nanophosphors. The low temperature gel-combustion method was employed for the preparation of the present La1−xAlO3:xTb3+ (x = 0.01–0.09) nanomaterials. The crystalline nature and other unit cell parameters were calculated by diffraction pattern and refined data of Rietveld. The present perovskite nanophosphor was found to be cubic crystal having space group Pm3̅m with space number 221. Transmission electron microcopy image has affirmed the smooth morphology, uniform distribution of particles (20–60 nm) with some agglomeration. The analysis of chemical bonding with vibrational characteristics was done by Fourier transform infrared (FTIR) spectroscopy. The information about elemental composition of the selected phosphor was obtained with the help of EDX analysis. In PL spectra recorded at λex= 266 nm, the dominating emission was obtained on 543 nm for 5D4→7F5 in the greenish spectral region. The appropriate color coordinates in the intense green region confirmed the potentiality of LaAlO3:Tb3+ nanophosphors in the display devices and other lighting applications.

Er3+ activated LaAlO3 perovskite phosphor: Crystal structure and down conversion photoluminescent behaviour for optoelectronic devices

• Trivalent Erbium activated LaAlO 3 perovskite materials were synthesized effectively through urea assisted gel-combustion method. • Rietveld refinement technique was utilized to confirm the structure of prepared materials and estimate various structural parameters. • G. Blasse’s theory was applied to understand the quenching effect of concentration. • The suitable color parameters of synthesized materials make them promising agent for optoelectronic devices. A series of green light emissive La 1-x AlO 3 :xEr 3+ (x = 0.01 to 0.08) nanophosphors were effectively synthesized via reliable, ecofriendly and low temperature based urea assisted gel-combustion process. The diffraction patterns and refinement data have revealed that the synthesized material is crystalline in nature with single phase cubic crystal structure having space group Pm3̅m (2 2 1). Moreover, the crystallite sizes were calculated by Debye-Scherrer’s formula (19–32 nm) and Williamson-Hall method (40–70 nm). Transmission electron microcopy image has affirmed the smooth morphology, uniform distribution of particles (40–70 nm) with some agglomeration. The examination of chemical bonding with vibrational characteristics was carried out by Fourier transform infrared (FTIR) spectroscopy. Elemental purity was proven by EDX analysis of the synthesized materials. The photoluminescence emission spectrum of the present phosphors was recorded at excitation wavelength of 376 nm and most intense peak detected on 548 nm with 4 S 3/2 → 4 I 15/2 which is responsible for the intense green color. In the luminescence intensity, a regular increasing fashion was observed with the concentration of Er 3+ ion upto 0.05 (called critical concentration) and then continuously decreased because of concentration quenching effect. Enhanced CIE parameters like chroma coordinates (0.307, 0.587), CCT value (5952.92 K) and color purity (94.41%) validate the potentiality of the synthesized phosphors in optoelectronic applications and other different lighting fields.

A Ferrofluid with High Specific Absorption Rate Prepared in a Single Step Using a Biopolymer.

An exhaustive characterization of the physicochemical properties of gum arabic (GA)-coated Fe3O4 magnetic nanoparticles was conducted in this work. These nanoparticles were obtained via the in-situ coprecipitation method (a fast single-step method) in two GA:Fe ratios, 10:1 and 20:1, respectively. Several experimental techniques were applied in the characterization process, all of them described below. Using Transmission Electron Microcopy images, they were shown to have spherical-like morphology with 11 nm diameter. The Fourier Transform Infrared spectra confirmed the attachment of the GA on the surface of the magnetic nanoparticles (MNPs), providing good colloidal stability from pH 7 to 8. The thickness of the coatings (1.7 nm and 1.1 nm) was determined using thermogravimetric measurements. A high specific absorption rate and superparamagnetic properties were determined using alternant and static magnetic fields, respectively. The GA-coated MNPs were non-cytotoxic, according to tests on HT-29 human intestine cells. Additionally, HT-29 cells were exposed to magnetic fluid hyperthermia at 530 kHz, and the induction of cell death by the magnetic field, due to the heating of GA-coated MNP, was observed.

Biosynthesis of silver nanoparticles using novel Bacillus sp. SBT8

ABSTRACTBiosynthesis of silver nanoparticles (AgNPs) using microorganisms is an important application of nanobiotechnology and green chemistry because of interest by pharmaceutical and food manufacturers. In this study, biosynthesis of AgNPs by a novel Bacillus strain isolated from a soil sample from Sakarya district in Turkey was investigated. Biosynthesis was performed using cell-free supernatant of the bacterium following 24 h growth. Effects of varying AgNO3 concentration (1–10 mM), pH (5–10), and temperature (30–40°C) on the synthesis of AgNPs were determined. Formation of AgNPs was monitored by UV–VIS spectroscopy. Field emission scanning electron microscopy was used to compare morphologies among the various culture conditions. The peaks created by surface plasmon resonance (SPR) of metals were obtained only at 4 and 6 mM AgNO3 concentrations and the maximum concentration for the biosynthesis was observed at 6 mM. The highest yield was achieved at pH 10 and larger nanoparticles were obtained at this pH. The optimum temperatures for biosynthesis were 33 and 37°C. Fourier transform infrared spectroscopy analysis and transmission electron microcopy images confirmed that the proteins served as capping. Energy-dispersive spectroscopy analysis validated the formation of AgNPs. AgNPs exhibited antibacterial activity toward Gram-positive and Gram-negative pathogens.

Bioavailability of coated and uncoated ZnO nanoparticles to cucumber in soil with or without organic matter

There is a gap of knowledge for the fate, effects and bioavailability of coated and uncoated ZnO nanoparticles (NPs) in soil. Moreover, little is known about the effects of soil properties on effects of NPs on plants. In this study, the availability ZnO NPs in two soils with different organic matter content (one treated with cow manure (CM) and the other as untreated) was compared with their bulk particles. Results showed that coated and uncoated ZnO NPs can be more bioaccessible than their bulk counterpart and despite their more positive effects at low concentration (< 100mgkg−1), they were more phytotoxic for plants compared to the bulk ZnO particles at high concentration (1000mgkg−1) in the soil untreated with CM. The concentration of 1000mgkg−1 of ZnO NPs, decreased shoot dry biomass (52%) in the soil untreated with CM but increased shoot dry biomass (35%) in CM-treated soil compared to their bulk counterpart. In general, plants in the CM-treated soil showed higher Zn concentration in their tissues compared with those in untreated soil. The difference in shoot Zn concentration between CM-treated and untreated soil for NPs treatments was more than bulk particles treatment. This different percentage at 100mgkg−1 of bulk particles was 20.6% and for coated and uncoated NPs were 37% and 32%, respectively. Generally, the distribution of ZnO among Zn fractions in soil (exchangeable, the metal bound to carbonates, Fe-Mn oxides, organic matter and silicate minerals and the residual fraction) changed based on applied Zn concentration, Zn source and soil organic matter content. The root tip deformation under high concentration of NPs (1000mgkg−1 treatment) was observed by light microscopy in plants at the soil untreated with CM. It seems that root tip deformation is one of the specific effects of NPs which in turn inhibits plant growth and nutrients uptake by root. The transmission electron microcopy image showed the aggregation of NPs inside the plant cytoplasm and their accumulation adjacent to the cell membrane.

Synthesis of MoS2/g-C3N4 nanocomposites with enhanced visible-light photocatalytic activity for the removal of nitric oxide (NO).

Molybdenum disulfide and graphitic carbon nitride (MoS2-g-C3N4) nanocomposites with visible-light induced photocatalytic activity were successfully synthesized by a facile ultrasonic dispersion method. The crystalline structure and morphology of the MoS2-g-C3N4 nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microcopy (TEM), high-resolution TEM (HRTEM) and scanning electron microscopy (SEM). The optical property of the as-prepared nanocomposites was studied by ultraviolet visible diffusion reflection (UV-vis) and photoluminescence(PL) spectrum. It could be observed from the TEM image that the MoS2 nanosheets and g-C3N4 nanoparticles were well combined together. Moreover, the photocatalytic activity of MoS2-g-C3N4 composites was evaluated by the removal of nitric oxide under visible light irradiation (>400nm). The experimental results demonstrated that the nanocomposites with the MoS2 content of 1.5 wt% exhibited optimal photocatalytic activity and the corresponding removal rate of NO achieved 51.67%, higher than that of pure g-C3N4 nanoparticles. A possible photocatalytic mechanism for the MoS2-g-C3N4 nanocomposites with enhanced photocatalytic activity could be ascribed to the hetero-structure of MoS2 and g-C3N4.

Self-textured oxide structure for improved performance of 365 nm ultraviolet vertical-type light-emitting diodes.

High performance 365 nm vertical-type ultraviolet light-emitting diodes (LEDs) are demonstrated by the insertion of a self-textured oxide mask (STOM) structure using metal-organic chemical vapor deposition. The dislocation densities were reduced significantly via the STOM by the observation of the transmission electron microcopy image. Under an injection current of 20 mA, a 50% light output power enhancement was achieved, representing an enhancement of 35.4% in light extraction efficiency and injected electron efficiency of the LED with STOM in comparison to that without STOM. At 350 mA, the light output power of the STOM-LEDs was approximately 24.4% higher. Measurements of the optical and electrical properties of the LED showed that the corrugated STOM structure improved the light scattering and reflection which increased the light output, and also enhanced the current spreading to intensify radiative recombination.

Laser-induced solution synthesis and deposition: A generic method to make metal chalcogenide nanotubes at high rate with high consistency

This article reports a new processing method for manufacturing nanotubes and possibly other nano entities with consistency at high rate. We show that this method can be applied for a wide range of materials, as demonstrated by a variety of metal chalcogenides. The proposed novel laser-induced solution synthesis and deposition method is a quantum jump for improving the consistency and manufacturing rate of chemical bath deposition and electroless deposition. We demonstrate the generic nature of this method by synthesizing nanocrystals of a number of arbitrarily selected metal chalcogenides, that is, tin oxide, iron oxide, manganese oxide and zinc sulfide, and depositing each of them in an ion-track polymer membrane for making uniform nanotubes. The mechanism of the tube formation is discussed. High consistency, fast growth rate, scalability and the ability of laser patterning are observed. Moreover, high-resolution transmission electron microcopy images indicate that the nanotubes made by this method, as demonstrated in SnO2, are coalesced by monodisperse ultrafine nanoparticles.

Ethanol Sensing Properties of Tungsten Oxide Nanocubes Prepared by a Urea-Assisted Hydrothermal Method

A facile hydrothermal process has been employed to synthesize WO3nanocubes using urea as an assistant agent. The crystal structure and morphology of WO3nanocubes have been characterized by X-ray diffraction (XRD), scanning electron microcopy (SEM) and transmission electron microcopy (TEM). XRD, SEM and TEM images of the products illustrate that WO3square nanostructures have a single orthorhombic phase, length of ~ 100-200 nm and thickness of ~ 40 nm. The ethanol sensing property of as-prepared tungsten oxide nanocubes is studied at ethanol concentration of 10-1000 ppm and working temperature of 160-400 °C. The result shows that the WO3 nanocubes have high sensitivity to ethanol because of their small size and special morphology.

Characterization and Catalytic Behavior of Nano Pt/MgO Catalysts

Pt/MgO catalysts were prepared by using wet impregnation method. X-ray diffraction, transmission electron microcopy (TEM), electron spectroscopy for chemical analysis, and temperature programmed surface reaction (TPSR) were used to characterize the calcined and used catalysts. Partial Oxidation of Methane (POM) to synthesis gas was carried out in a fixed bed micro-reactor to test the catalytic activity. TEM images revealed that Pt particles have the size of less than 10 nm, the size of the support MgO is about 50200 nm. At 800C, the Pt/MgO catalyst exhibited a very high activity and stability for POM reaction. Both the conversion of methane and selectivities to CO and H2 remained almost constant up to 120 h. The dispersed Pt existed in the metallic state. The state and the dispersion of active Pt and the structure of support MgO were very stable, together with the high ability to resist carbon deposition, made the catalysts show a very high stability for POM under stoichiometric reaction conditions.

Highly efficient Ru/MgO catalysts for NH 3 decomposition: Synthesis, characterization and promoter effect

Highly dispersed Ru nanoparticles exhibiting high catalytic activity in NH 3 decomposition were prepared by a polyol reduction method. The physicochemical properties were studied using nitrogen physisorption, X-ray diffraction (XRD), transmission electron microcopy (TEM) and thermogravimetry (TG). BET measurements showed the obtained Ru/MgO mesoporous material possessed a surface area as high as 151 m 2 g cat - 1 . As evidenced by TEM images, the particle size of Ru ranged narrowly from 1.2 to 2.3 nm. XRD examination revealed that the MgO particles as the support with mean size of 8 nm were successfully synthesized. Different alkali metal salts were added as the promoter through conventional impregnation, by which the catalytic activity could be significantly enhanced.

Comparison of Fe/Al&amp;lt;tex&amp;gt;$_2$&amp;lt;/tex&amp;gt;O&amp;lt;tex&amp;gt;$_3$&amp;lt;/tex&amp;gt;and Fe, Co/Al&amp;lt;tex&amp;gt;$_2$&amp;lt;/tex&amp;gt;O&amp;lt;tex&amp;gt;$_3$&amp;lt;/tex&amp;gt;Catalysts Used for Production of Carbon Nanotubes From Acetylene by CCVD

Characterization of iron containing alumina supported catalysts was performed by transmission electron microcopy (TEM), Mo/spl uml/ssbauer, and XPS spectroscopy during formation of multiwall carbon nanotubes from acetylene at 1000 K. TEM images showed that carbon fibers (outer diameter is around 20-40 nm) were generated on Fe/Al/sub 2/O/sub 3/ samples while on the bimetallic Fe,Co/Al/sub 2/O/sub 3/ carbon nanotubes with an average diameter of 8-12 nm were formed. XPS spectra revealed that Fe-Co alloy formed during the interaction of Fe,Co/Al/sub 2/O/sub 3/ and acetylene at 1000 K. The formation of the bimetallic alloy was proven by Mo/spl uml/ssbauer spectroscopy as well.

Effect of hydrogen bonding on the rheology of polycarbonate/organoclay nanocomposites

The linear dynamic viscoelastic properties and non-linear transient rheology of polycarbonate (PC)/clay nanocomposites were investigated at temperatures ranging from 240 to 280 °C. For the study, nanocomposites of PC and natural montmorillonite (Cloisite Na+) or chemically modified clay (Cloisite 30B) were prepared by melt blending in a twin-screw extruder. Cloisite 30B is a natural montmorillonite modified with methyl, tallow, bis-2-hydroxyethyl, quaternary ammonium chloride (MT2EtOH). In both PC/Cloisite Na+ and PC/Cloisite 30B nanocomposites the concentration of clay was varied from 2.3 to 4.3wt%. In situ Fourier transform infrared (FTIR) spectroscopy results show that at temperatures ranging from 30 to 280 °C the carbonyl groups in PC and the hydroxyl groups in MT2EtOH of Cloisite 30B in PC/Cloisite 30B nanocomposites formed hydrogen bonds, while no evidence of hydrogen bonding was observed in the PC/Cloisite Na+ nanocomposites. There are no discernible sharp reflections in the X-ray diffraction (XRD) patterns of PC/Cloisite 30B nanocomposites, after Cloisite 30B having the d001 spacing of 1.85 nm was mixed with PC, whereas the d001 spacing changes little (1.17 nm) before and after the mixing of Cloisite Na+ to PC. Transmission electron microcopy (TEM) images show that organoclay platelets are well dispersed in PC/Cloisite 30B nanocomposites, while the untreated clay platelets are poorly dispersed in PC/Cloisite Na+ nanocomposites. The observed differences in XRD patterns and TEM images between the two nanocomposite systems are explained by in situ FTIR spectroscopy. The results of rheological measurements (linear dynamic viscoelasticity, non-linear transient shear flow, and steady-state shear flow) support the conclusions drawn from the results of XRD, TEM, and FTIR spectroscopy.