Microscopy Measurements Research Articles

Surface characterization of biochar from agricultural residues for environmental applications

Bio-waste materials banana (Musa ealbisiana) leaves, cassava (Manihot esculenta) peels, mango (Mangifera indica) leaves, plantain (Plantago lanceolata) leaves and peels were pyrolyzed at different temperatures; 300, 400, 450, 500 and 600 oC using a muffle furnace. The biochar samples obtained were characterized and properties evaluated for their potential application in soil for agronomic and environmental benefits. The measured physico-chemical properties; pH, bulk density, percentage yield and electrical conductivity varied with temperature of pyrolysis and somewhat with the source of the bio-waste. Surface morphology and elemental composition were determined from Scanning Electron Microscopic (SEM) and Energy Dispersive X-ray (EDX) measurements and showed variations in texture, porosity and elemental composition with pyrolysis temperature. The produced biochar yields were in the range 16.1 to 84.6% and highest for banana leaves (BL) pyrolysed at 300 oC. The scanned images showed a remarkable surface morphology for all the biochar samples obtained at temperatures ≥ 450 oC. The pH obtained indicate the alkaline nature of the biochars with mean values > 7.5 except for cassava peels (CP) pyrolysed at 300 oC having a value of 5.5. From the elemental analysis, the high carbon content (> 60%) at higher temperatures (> 450 oC) of the biochars and the molar O/C ratios may suggest the suitability of the biochars in applications for long-term carbon sequestration and also promising candidates for soil amendment due to increase in macro porosity.

Study on the electrical performance degradation mechanism of β -Ga2O3 p-n diode under heavy ion radiation

The impact of heavy ion irradiation on the β-Ga2O3 p-n diode and its physical mechanism have been studied in this Letter. After the irradiation fluence of 1 × 108 cm−2, it is observed that the electrical performance of the device is significantly degraded. The forward current density (JF) is reduced by 49.4%, the reverse current density (JR) is increased by more than two orders of magnitude, and the breakdown voltage (VBR) is decreased by 30%. Based on the results of the deep-level transient spectroscopy measurement, it is concluded that acceptor-like traps generated with an energy level of EC-0.75 eV in the β-Ga2O3 drift layer dominate the JF degradation of the device, which are most likely related to Ga vacancies. These acceptor-like traps result in the reduction of change carrier concentration, which in turn leads to a decrease in JF. In addition, according to the conductive atomic force microscope measurements and theoretical calculation, it is clearly observed that the latent tracks induced by heavy ion irradiation can act as leakage paths, leading to a significant degradation of JR and VBR.

Synthesis of an Organotin S‐thiobenzoylthioglycolate Complex and its Application as a Single Source Precursor to SnS2 Thin Film

AbstractS‐thiobenzoylthioglycolic acid possessing two sulfur and two oxygen atoms was used to synthesize an oxoorganotin(IV) carboxylate molecule, [BuSn(O)(O2CCH2SC(S)Ph)]6. The molecule is a hexanuclear cluster that has been characterized structurally by single‐crystal X‐ray diffraction analysis. The complex was used as a single‐source precursor to prepare a thin film of SnS2 by the chemical vapor deposition technique. The distinct triangular formations of SnS2 were characterized by spectral and microscopic measurements. Well‐defined boundaries and considerable sizes of SnS2 structures have been identified.

Combined effects of pores and cracks on the effective thermal conductivity of materials: a numerical study

Porous solids are commonplace in engineering structures and in nature. Material properties are inevitably affected by the internal inhomogeneity. The effective thermal conductivity of porous materials has been and remains to be a subject of extensive research. Less attention has been devoted to thermal conductivity impacted by internal cracks. This study is devoted to theoretical analyses of the combined effects of pores and cracks on the effective thermal conductivity. Systematic numerical simulations using the finite element method are performed based on two-dimensional models, with periodic distributions of internal pores and cracks. The parametric investigations seek to address how individual geometric layout can influence the overall thermal conduction behavior. In addition to circular pores and isolated cracks, angular pores with cracks extending from their sharp corners are also considered. It is found that both isolated cracks and cracks connected to existing pores can significantly reduce the effective thermal conductivity in porous materials. Since it is much easier to microscopically detect internal pores than thin cracks, care should be taken in using the apparent porosity from microscopic images and density measurements to estimate the overall thermal conductivity. Quantitative analyses of the detailed geometric effects are reported in this paper.

Multi-hole liquid CO2 flashing jet: A novel method for achieving trade-off between impact region and impact force through phase transition

A novel multi-hole liquid CO2 flashing jet for coalbed methane exploitation is proposed, which undergoes phase transition during the injection of superheated CO2. The thermal stress generated during the phase-transition process is beneficial for rock fragmentation. Different types of nozzles were compared, and a conical convergent nozzle was selected owing to its wider jets. The proposed jet interaction criteria based on the fuel were examined using CO2, and discrepancies due to the internal phase transition and stronger cooling effects were observed. Nozzles with larger drilling angles were found to be more prone to transition from cone-shaped to jet-shaped morphologies. Coal-breaking experiments were also performed, and three distinct coal-breaking patterns induced by multi-hole flashing CO2 jets were identified. The effects of thermal stress on rock-breaking were evaluated using a beam-scanning electron microscope and wave velocity measurement with a piezoelectric accelerometer. Thermal cracks induced by matrix contraction were identified, indicating the potential to enhance breakage efficiency. The results indicate that the trade-off between the impact region and impact force should be carefully adjusted to achieve the desired coal-breaking performance. This study provides a potential method to utilize CO2, as well as some guidance for the issues that must be addressed in energy exploration using CO2.

New Evidences of Fluid Inclusions from Wufeng Formation Reveal Shale Gas Accumulation and Leakage Histories in Northern Guizhou, Southwestern China

Abstract Shale gas accumulation and leakage histories are significant for evaluating the prospects of hydrocarbon exploration. The Wufeng Formation in northern Guizhou is a potential target for shale gas exploration and development. This work selected a typical Well YH1 to conduct detailed fluid inclusion analyses in the Wufeng Formation. We integrated the inclusion results with systematic core description, thin-section microscopic observation, laser Raman spectroscopy, microscopic temperature measurement, and burial–thermal history to reveal shale gas accumulation and leakage histories in northern Guizhou. The results show that the source rocks of the Wufeng Formation occurred in oil generation since the Permian and entered the stage of natural gas generation at the end of the Late Triassic. During the Early Jurassic and Early Cretaceous, shale gas accumulated in the Wufeng Formation reservoirs, and the stratigraphical pressure coefficient ranged from 1.47 to 1.97. Under the influence of the Yanshan orogeny, northern Guizhou experienced a rapid uplift and exhumation since the end of the Early Cretaceous. Under the influence of this tectonic, the stratigraphical pressure plummeted to the normal level, adversely impacting the accumulated shale gas in reservoirs and resulting in leakage events since the end of the Early Cretaceous. The reservoirs were further destroyed and adjusted, and the gas continued to leak because of a long-term and large-scale uplift and exhumation during the Himalayan orogeny. This work clarified that shale gas accumulation and leakage histories are significant for evaluating petroleum exploration.

Determination of the significance of atomic concentration on surface properties of Ba x Mg1-x F2 alloy coatings via microscopic and spectroscopic techniques.

Both BaF2 and MgF2 compounds and Ba x Mg1-x F2 alloy thin films were deposited on glass and silicon (Si) substrates in nanometric sizes (100 ± 10 nm) in a high vacuum environment by radio frequency (rf) magnetron sputtering. Using BaF2 (99% purity) and MgF2 (99% purity) target materials and adjusting the power levels applied to these targets, Ba x Mg1-x F2 alloy coatings at different atomic concentrations were formed under the same vacuum conditions. The microstructure and surface characteristics of the samples were analysed with the help of spectroscopic and microscopic methods. For the surface characterization, with scanning acoustic microscopy (SAM), 2-dimensional surface acoustic images of the samples were mapped, the surface acoustic impedance values were determined, and information about the micro hardness of the materials was obtained. Surface roughness values and grain sizes were obtained by taking 3-dimensional surface images of investigated materials using atomic force microscopy (AFM). Average nanometric particle sizes were determined for each sample with scanning electron microscopy (SEM), therefore, information about surface homogeneity was obtained. For the microstructural characterization, quantitative elemental analysis was performed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDS), and stoichiometric ratios of atomic compositions were identified. By evaluating the data obtained from the microscopic and spectroscopic measurements, the effect of the atomic concentration parameter on the morphological properties of the material was determined. The usability of the produced binary fluoride alloy thin film coatings is promising for emerging optoelectronic, ceramic industry, biomedical and surface acoustic wave applications.

Formulation and investigation of differently charged β-cyclodextrin-based meloxicam potassium containing nasal powders

Nasal systemic drug delivery may provide an easy way to substitute parenteral or oral dosing, however, the excipients have an important role in nasal formulations to increase the permeability of the mucosa and prolong the residence time of the drug. In this work, we aimed to produce meloxicam potassium monohydrate (MXP) containing nasal powders by a nano spray drier with the use of a neutral, an anionic and a cationic β-cyclodextrin as permeation enhancers, and (polyvinyl)alcohol (PVA) as a water soluble polymer. The following examinations were performed in order to study the effect of the applied excipients on the nasal applicability of the formulations: laser scattering, scanning electron microscope measurement, XRPD, DSC and FTIR measurements, adhesivity, in vitro drug release and permeability tests through an artificial membrane and RPMI 2650 cells. Based on our results, spherical particles were prepared with a size of 1.89–2.21 µm in which MXP was present in an amorphous state. Secondary interactions were formed between the excipients and the drug. The charged cyclodextrin-based formulations showed significantly higher adhesive force values regardless of the presence of PVA. The drug release was fast and complete. The passive diffusion of MXP was influenced not only by the charge of the cyclodextrin, but the presence of PVA, too. The permeation of the drug was enhanced in the presence of the anionic cyclodextrin testing it on RPMI 2650 cell model.

Influence of power ramps on the physical properties of AZO thin films deposited at room temperature by RF magnetron sputtering technique

Abstract Aluminum-doped zinc oxide (AZO) thin films were deposited on glass substrates at room temperature by RF sputtering technique. Power ramps between 125 and 105 W were applied with a step of 4 W by intervals of 15, 7.5 and 1.8 min, for 180 min at 1.60 Pa. In this study, we investigated the structural, morphological, electrical, and optical properties of AZO films. X-ray Diffraction analysis showed that the films have a wurtzite-type hexagonal crystalline structure with a preferential crystallographic orientation (002) normal to the c axis. The average transmittance is greater than 76% for the wavelength range in the visible spectrum. The bandgap values were found between 3.32 and 4.01 eV, and refractive index was 1.79–2.60. Atomic force microscope measurements show homogeneous films with a roughness between 17–22 nm. A minimum resistivity value of 2.0 × 10−3 Ω cm was obtained for the film by using a power ramp of 4 W/1.8 min.

Exploring the Impact of Oxygen Doping in Li2FeS2 Cathode Materials for Li-Ion Batteries

Over the past few decades, rechargeable lithium-ion batteries have become popular for a variety of applications, such as electric vehicles, smart grids, and portable energy devices. However, due to their limited capacity, stability, and lifespan, they are not suitable for advanced transportation applications. To overcome these challenges, researchers have investigated the use of low-cost, high-energy-density, and safe positive electrode materials for secondary lithium batteries, including lithium iron sulfide. In this particular study, our focus is to investigate the effect of highly electronegative anion doping on the properties of lithium iron sulfide cathode through the solid-state method. Our approach involves using both in-situ and ex-situ observations to establish a correlation between the Redox behavior and structural properties of the prepared cathode materials. We have designed and characterized the material using various techniques, such as X-ray absorption spectroscopy (XAS) and synchrotron-based X-ray diffraction (XRD). Scanning electron microscope (SEM) measurement was conducted to study the morphology of the cathode material. Transmission electron microscopy (TEM) was employed to further study the microstructure of the cathode material at an atomic level. We analyzed the electron density distribution of the modified cathode material using XANES measurement and studied the structural properties through synchrotron-based XRD. Our study has revealed that oxygen-doping helps to improve material stability. As a result, the modified cathode (with optimal oxygen doping) exhibited a 50% capacity enhancement compared to pristine after 100 cycles. We also observed a shift to a higher voltage oxidation plateau of the oxygen-doped cathode material which is due to the influence of anion substitution on the electrochemistry and charge storage mechanisms. In summary, our detailed characterization and experimental results demonstrate the potential of oxygen-doped Li2FeS2 as a promising cathode material for advanced lithium-ion battery applications. The study's detailed characterization and experimental results will be presented, along with future perspectives.

Tetraphenylethylene tethered 1-(pyridine-2-yl)imidazo[1,5-a]pyridine: Synthesis, aggregation induced emission, copper(II) ion detection and imaging of latent fingerprint

The development of aggregation induced emissive probe with high sensitivity and selectivity for Cu2+ ions is a fascinating research in biomedical sciences. In this context, we have successfully synthesized an aggregation induced emissive probe for the selective detection of Cu2+ ions by incorporating a 1-(pyridine-2-yl)imidazo[1,5-a]pyridine arm in the tetraphenylethylene framework. The aggregates have been characterized using pivotal microscopic and photophysical measurements. The results exhibits that the aggregates have a spherical shape with an average size of 90 nm and a fluorescence quantum yield of ∼23 %. The aggregated fluorescent probe exhibited an excellent selectivity towards Cu2+ ions with a detection limit of 83 nM and presented a good efficacy over diverse environmental water samples. Furthermore, the quenching type is delineated as static due to complexation followed by deaggregation which was supported by dynamic light scattering and Tyndall effect experiments. In addition, the high solid state emissive property of the probe makes it a potential candidate for latent fingerprint analysis to gather level 2 and 3 information thereby playing a substantial role in forensic investigations.

Effects of NIR-reflective pigments on waterborne polyurethane coatings and their thermal insulation performance

Waterborne coatings have garnered much attention and gradually occupied the coating market recently due to the significant advantages in volatile organic compound emissions compared with solvent-borne coatings. Waterborne polyurethane coatings are a majority portion of waterborne coatings. Unlike solvent-borne coatings, the film formation of waterborne coatings occurs in an inhomogeneous phase, which brings a challenge for pigmentation in waterborne coatings. However, the influence of pigment on film formation and the property of waterborne polyurethane coating remain unclear. In this study, the different contents of commercial black near-infrared (NIR) reflective pigments were incorporated into both commercial and synthetic waterborne polyurethane systems. The film formation process was monitored by multispeckle diffusing wave spectroscopy. The impact of the pigment content on dry films was assessed through scanning electron microscope, color and gloss measurements, dynamical thermal analyzer, and tensile testing. Furthermore, the thermal insulation performance of the waterborne polyurethane coatings was evaluated to study the function of the NIR reflective pigments. Our findings reveal that the addition of black NIR reflective pigments yields a multifaceted effect on film formation and coating morphology and improves thermal insulating property. Elevated pigment content correlated with increased crosslinking density, tensile stress, and Young's modulus.

Enhancement of ferroelectric properties of the Ga0.6Fe1.4O3 films by Zn,N co-doping

Multiferroic materials have attracted considerable interests due to their scientific and technological importance in advanced devices. Ga0.6Fe1.4O3 thin film exhibits ferrimagnetism above room temperature but suffers from large leakage current. To reduce the charge conduction and enhance the ferroelectric properties of Ga0.6Fe1.4O3 film, ion doping is a useful technique. In this study, we fabricated Ga0.6Fe1.4-xZnxO3/N films by substituting Zn2+ and N3- ions in Ga0.6Fe1.4O3 for Fe and O, respectively. The influence of Zn, N co-doping on the structure, leakage current, magnetic and ferroelectric properties of the films were investigated. The results indicated that the films exhibited the orthorhombic structure with the incorporation of Zn and N. All Ga0.6Fe1.4-xZnxO3/N films showed above room temperature ferrimagnetism, and the magnetization and transition temperature values decreased with Zn,N co-doping. The microscopic and macroscopic ferroelectric measurements have demonstrated the ferroelectric polarization switching of the films. The ferroelectric hysteresis loops of the Ga0.6Fe1.38Zn0.02O3/N film showed the remnant polarization of ∼0.46 μC/cm2 with the coercive field of ±2 V at room temperature. The leakage current significantly reduced from ∼3.27×10−1 A/cm2 for pure Ga0.6Fe1.4O3 film to ∼1.48×10−5 A/cm2 for Ga0.6Fe1.35Zn0.05O3/N film, by four orders of magnitude. This may be attributed to the incorporation of Zn2+ and N3-, providing charge compensation to valence fluctuations of Fe between Fe3+ and Fe2+. These results provide an effective method to improve the ferroelectricity of Ga0.6Fe1.4O3 film, and open a wide perspective for the potential application in magnetoelectric devices.

Visualizing micro leakage position by dynamic measurement in operando hydrogen microscope

We developed an operando hydrogen microscope (OHM) to determine where in materials hydrogen is trapped and causes embrittlement, and the location of hydrogen leak from gas lines, by hydrogen visualization. In the OHM, hydrogen atoms that permeate through a sample are ionized by incident electrons on the sample surface, desorbed into an ultra-high vacuum environment, and then detected. We visualized the surface hydrogen distribution from the hydrogen desorption position. It is also possible to visualize atoms adsorbed from gas phase, as well as gases that leak rather than permeate. The probability that a gas will be adsorbed depends on the substance. The amount of adsorbate increases at a site of locally high pressure. We created guidelines for background evaluation and quantitative analysis of leakage amount under the experimental conditions. Therefore, by visualizing the distribution of adsorbed substances using OHM, we can identify the location of a leak. We visualized a controlled leak of hydrogen in a sintered stainless steel body.

A novel focus measure algorithm for three-dimensional microscopic vision measurement based on focus stacking

The three-dimensional (3D) microscopic vision measurement methods based on focus stacking are widely used because of their outstanding advantages such as noncontact, high accuracy, high flexibility, and low cost. On-site focus stacking 3D microscopic measurement is susceptible to environmental disturbances, surface dirt, illumination occlusion, and the shape of the object itself. This leads to the difficulty of obtaining the focus position accurately, stably, and quickly with the existing focus measure function. To improve the ability to extract the focus signals from the image, high-pass mask operators and band-pass mask operators are designed. A new high-pass and band-pass energy weighting focus measure function with rotation invariance is proposed. A focus stacking microscopic measurement system is constructed to validate the proposed focus measure function. Six classical and latest focus measure functions are selected for the quantitative performance comparison experiments. The experimental results show that the proposed algorithm has the best performance in accuracy, sensitivity, unimodality, and monotonic interval range. This measure function has a high operational efficiency, nearly three times the computational efficiency of the frequency domain measure function. The measure function also drastically reduces the evaluation curve fluctuation, peak collapse, and other anomalies, and shows good robustness.

Design and analysis of quorum sensing language “Interpreter” ecosystem for microbial community

Microbes in diverse natural communities communicate via quorum sensing (QS) signals that act as microbial languages. QS-based communications have been reconstructed in two-strain microbiota for promising consortium-based applications. However, investigation and synthesis of multiple QS signals transmission in the QS communication network (QSCN) are less explored. In this study, QS language “interpreter” was proposed and constructed in five Escherichia coli strains to simulate the linear and circular QSCN among natural microbial communities. Specifically, by combining strain-level microscopic and bulk-level macroscopic measurements, we investigate the performances and dynamics of synthetic three-strain QS language “interpreter” ecosystems that are in response to dramatic environmental changes. Results of micro- and macroscopic experiments showed that the existence of complex QS language “interpreter” ecosystems promote the stability maintenance of microbial community. Furthermore, a comprehensive kinetic computational model was developed for the optimization of tunable directed QSCN. Finally, the perspectives of the QSCN for the effective control of microbial communities were discussed and summarized. This study revealed the dynamic control of complex microbial communications, contributing to ecosystem-based engineering and microbiome-based therapeutics.

High-Temperature-Resistant Profile Control System Formed by Hydrolyzed Polyacrylamide and Water-Soluble Phenol-Formaldehyde Resin.

To realize the effective profile control of a heavy oil reservoir, hydrolyzed polyacrylamide (HPAM) and water-soluble phenol-formaldehyde resin (PR) were chosen to prepare the profile control system, which gelled at medium or low temperatures and existed stably at high temperatures in the meantime. The effects of phenolic ratios, PR concentration, and HPAM concentration on the formation and strength of the gels were systematically studied by the gel-strength code method and rheological measurements. And the microstructure of the gels was investigated by scanning electron microscope measurements. The results showed that the gelling time of the HPAM-PR system was 13 h at 70 °C. The formed gel could stay stable for 90 days at 140 °C. In addition, the gels showed viscoelastic properties, and the viscosity reached 18,000 mPa·s under a 1.5 s-1 shearing rate due to their three-dimensional cellular network structure. The formation of the gels was attributable to the hydroxyl groups of the PR crosslinking agent, which could undergo the dehydration condensation reaction with amide groups under non-acidic conditions and form intermolecular crosslinking with HPAM molecules. And the organic crosslinker gel system could maintain stability at higher temperatures because covalent bonds formed between molecules.

Remotely Controlled Surface Charge Modulation of Magnetoelectric Nanogenerators for Swift and Efficient Drug Delivery.

We have developed a highly efficient technique of magnetically controlled swift loading and release of doxorubicin (DOX) drug using a magnetoelectric nanogenerator (MENG). Core-shell nanostructured MENG with a magnetostrictive core and piezoelectric shell act as field-responsive nanocarriers and possess the capability of field-triggered drug release in a cancerous environment. MENGs generate a surface electric dipole when subjected to a magnetic field due to the strain-mediated magnetoelectric effect. The capability of directional magnetic field-assisted modulation of the surface electrical dipole of MENG provides a mechanism to create/break ionic bonds with DOX molecules, which facilitates efficient drug attachment and on-demand swift detachment of the drug at a targeted site. The magnetic field-assisted drug-loading mechanism was minutely analyzed using spectrophotometry and Raman spectroscopy. The detailed time-dependent analysis of controlled drug release by the MENG under unidirectional and rotating magnetic field excitation was conducted using field-emission scanning electron microscopy, energy-dispersive X-ray, and atomic force microscopic measurements. In vitro, experiments validate the cytocompatibility and magnetically assisted on-demand and swift DOX drug delivery by the MENG near MCF-7 breast cancer cells, which results in a significant enhancement of cancer cell killing efficiency. A state-of-the-art experiment was performed to visualize the nanoscale magnetoelectric effect of MENG using off-axis electron holography under Lorentz conditions.

Real-time control of microcrystal formation with inline process microscopy

The control of microcrystal formation during crystallization is necessary to ensure good separation of crystals and molasses without adding excessive wash water. This paper presents an automatic inline process microscope measurement of sugar crystals and how its results are utilized in a real-time process control. The system captures high-precision transilluminated images of sugar crystals flowing through a 10-mm wide gap in the evaporating crystallizer. It automatically analyses the sugar crystals in size range from 10 µm to 4 mm visible in images. System reports the number of detected microcrystals (10–30 µm) and crystals (>30 µm), mean aperture of crystals (MA), co-efficient of variation in size (CV), crystal growth rate and volume fractions of the specified crystal size classes in real time. The performance of the control and monitoring approach is highlighted with the results of example strikes.

Polarization enhancement mechanism from tissue staining in multispectral Mueller matrix microscopy.

Mueller matrix microscopy can provide comprehensive polarization-related optical and structural information of biomedical samples label-freely. Thus, it is regarded as an emerging powerful tool for pathological diagnosis. However, the staining dyes have different optical properties and staining mechanisms, which can put influence on Mueller matrix microscopic measurement. In this Letter, we quantitatively analyze the polarization enhancement mechanism from hematoxylin and eosin (H&E) staining in multispectral Mueller matrix microscopy. We examine the influence of hematoxylin and eosin dyes on Mueller matrix-derived polarization characteristics of fibrous tissue structures. Combined with Monte Carlo simulations, we explain how the dyes enhance diattenuation and linear retardance as the illumination wavelength changed. In addition, it is demonstrated that by choosing an appropriate incident wavelength, more visual Mueller matrix polarimetric information can be observed of the H&E stained tissue sample. The findings can lay the foundation for the future Mueller matrix-assisted digital pathology.