Atomic Force Microscopy Images Research Articles

IrO2-ZrO2-SiO2 ternary oxide composites- based DSAs: Activity toward oxygen evolution reaction with long-term stability

BackgroundHigher purity of copper is produced by Electrowinning (EW) in the cathode. A major challenge in this technique is the anodic structure that causes in the energy consumption, corrosion resistance, and contamination of the copper produced in the cathode. MethodsTernary metallic oxide (IrO2-ZrO2-SiO2) composites with the different molar percentages of IrO2: SiO2 (10:60, 15:55, and 20:50%) were prepared on titanium substrate by the sol-gel technique, and then thermal decomposition to study the impact of IrO2 and SiO2 contents on the electrocatalyst performances of the dimensionally stable anodes (DSAs). The physicochemical properties of the DSAs were determined by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), Atomic force microscopy (AFM), and electrochemical measurements. Significant findingsFE-SEM and AFM images display the impact of SiO2 on the crystallization and crystal growth of IrO2, leading to the formation of finer oxide particles and the porous morphology of the ternary oxide coatings. The DSA composed of 50 % SiO2 and 20 % IrO2 (IZS (20–30–50)) with a more porous surface area represented high apparent electrocatalytic activity toward the oxygen evolution reaction with long-term stability as analyzed under cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and accelerated lifetime (ALT) plots.

Step height measurement of monoatomic silicon crystal lattice steps with a commercial atomic force microscope

Abstract Precise control of advanced materials relies on accurate dimensional metrology at the sub-nanometre scale. At this scale, the accuracy of scanning probe microscopy (SPM) has been limited by the lack of traceable transfer standard artefacts with calibration structures of suitable dimensions. With the adoption in 2019 of the silicon crystal lattice spacing as a secondary realization of the metre in the International System of Units (SI), SPM users have direct access to a realization of the SI metre at the sub-nanometre level by means of the step height of self-assembled monatomic lattice steps that can form on the surface of silicon crystals. A key challenge of successfully adopting this pathway is establishing the need for established protocols to minimize measurement errors and artifacts in routine laboratory use.
In this study, step height measurements of monoatomic lattice steps in an ordinal/staircase structure on a Si(111) crystal surface have been derived from images acquired with a commercially available, research-level atomic force microscope (AFM). Measurement results derived from AFM images using three different SPM image processing and analysis software packages are compared. Significant sources of measurement uncertainty are identified; principally the contribution from the dependence on scan direction. The calibration of the
AFM derived from this measurment was used to traceably measure the sub-nanometre lattice steps on a silicon carbide crystal surface to demonstrate the viability of this calibration pathway.

REPROGRAMMING FILAMENTOUS FD VIRUSES TO CAPTURE COPPER IONS.

C-terminal truncated variants (A, VA, NVA, ANVA, FANVA and GFANVA) of our recently identified Cu(II) specific peptide "HGFANVA" were displayed on filamentous fd phages. Wild type fd-tet and engineered virus variants were treated with 100 mM Cu(II) solution at a final phage concentration of 1011vir/ml and 1012vir/ml. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) imaging before Cu(II) exposure showed»6-8 nm thick filamentous virus layer formation. Cu(II) treatment resulted in aggregated bundle-like assemblies with mineral deposition. HGFANVA phage formed aggregates with an excessive mineral coverage. As the virus concentration was 10-fold decreased, nanowire-like assemblies were observed for shorter peptide variants A, NVA and ANVA. Wild type fd phages did not show any mineral formation. Energy dispersive X-ray spectroscopy (EDX) analyses revealed the presence of C and N peaks on phage organic material. Cu peak was only detected for engineered viruses. Metal ion binding of viruses was next investigated by enzyme-linked immunosorbent assay (ELISA) analyses. Engineered viruses were able to bind Cu(II) forming mineralized intertwined structures although no His (H) unit was displayed. Such genetically reprogrammed virus based biological materials can be further applied for bioremediation studies to achieve a circular economy.

Engineered microbubbles decorated with red emitting carbon nanoparticles for efficient delivery and imaging

Altering the route of uptake by the cells is an attractive strategy to overcome drug-receptor adaptation problems. Carbon nanoparticles (CNPs) with emission beyond tissue autofluorescence for imaging biological tissues were used to study the phenomenon of uptake by the cells. In this regard, red-emitting carbon nanoparticles (CNPs) were synthesized and incorporated onto lipid microbubbles (MBs). The CNPs showed red emissions in the range of 640 nm upon excitation with 480 nm wavelength of light. Atomic force microscopic and confocal microscopic images showed the successful loading of CNPs onto the MB. Carbon nanoparticle loaded microbubbles (CNP-MBs) were treated with NIH 3 T3 cells at different concentrations. Confocal microscopic imaging studies confirm the presence of CNPs inside the treated cells. Cytotoxicity studies revealed that the CNPs showed minimal toxicity towards cells after loading onto MBs. The CNPs are usually taken up by the cells through the clathrin-mediated (CME) pathway, but when loaded onto MBs, the mechanism of uptake of CNPs is altered, and the uptake by the cells was observed even in the presence of inhibitors for the CME pathway. Loading CNPs onto MBs resulted in the uptake of CNPs by the cell through micropinocytosis and sonophoresis in the presence of ultrasound. The in vivo uptake CNP-MBs were performed in Danio rerio (Zebrafish larvae). This study provides insights into altering the uptake pathway through reformulation by loading nanoparticles onto MBs.

Atomic force microscopy simulations for CO-functionalized tips with deep learning

Atomic force microscopy (AFM) operating in the frequency modulation mode with a metal tip functionalized with a CO molecule is able to image the internal structure of molecules with an unprecedented resolution. The interpretation of these images is often difficult, making the support of theoretical simulations important. Current simulation methods, particularly the most accurate ones, require expertise and resources to perform ab initio calculations for the necessary inputs (i.e charge density and electrostatic potential of the molecule). Here, we propose a computationally inexpensive and fast alternative to the physical simulation of these AFM images based on a conditional generative adversarial network (CGAN), that avoids all force calculations, and uses as the only input a 2D ball–and–stick depiction of the molecule. We discuss the performance of the model when trained with different subsets extracted from the previously published QUAM-AFM database. Our CGAN reproduces accurately the intramolecular contrast observed in the simulated images for quasi–planar molecules, but has limitations for molecules with a substantial internal corrugation, due to the strictly 2D character of the input.

Synthesis of Wrinkled MoS2 Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space

Synthesis of Wrinkled MoS2 Thin Films Using a Two-Step Method Consisting of Magnetron Sputtering and Sulfurization in a Confined Space

Influence of the DEA Concentration on Structural and Optical Properties of Nanodot PbS Thin Films Growth by Chemical Solution Deposition: Unveiling Dual Optical Absorption Edges

The present paper presents a straightforward method for producing thin film layers of sulfide quantum dots (PbS-QDs) on a glass substrate using chemical solution deposition (CSD) assisted by dipcoating technique. The deposited PbS-QDs films were subjected to a comprehensive analysis using atomic force microscopy (AFM), energy dispersive X-ray (EDX) scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–vis–IR absorption, and photoluminescence spectroscopic (PL) techniques to investigate the effects of varying concentrations of diethanol amine (DEA) on their morphology, crystal structure, elemental composition, light absorption, and emission characteristics. The spherical shape of the PbS-QDs was confirmed by AFM and SEM images with average sizes around 100 and 50 nm, respectively. The energy dispersive X-ray (EDX) analysis provides evidence the existence of Pb and S elements within the PbS matrix. X-ray diffraction (XRD) results validate that the deposited films exhibit high crystallinity, with a preferential orientation along the (111) plane and a face-centered cubic lattice structure of PbS. The crystallite size of PbS is measured to be 46.6 nm. Based on the optical absorption measurements, we have determined the size range of PbS nanocrystals to be between 4.3 and 11.5 nm. The optical studies reveal the presence of two optical absorption edges within the visible and infrared spectrum, two direct band gap energy, two cut-off wavelengths, two confinement energy, two Urbach energy tail, and dual emission peaks of PbS-QDs at room temperature. The analysis reveals the presence of two distinct band gap energies, one in the visible range (1.3–2.28 eV) and the other in the infrared range (0.65–0.88 eV), which can be attributed to the formation of two distinct sizes of quantum dots situated in two different layers. The first layer, deposited directly on the glass substrate, comprises quantum dots with an average size of approximately 5.2 nm, while the second layer contains quantum dots with an average size of about 9.5 nm. This ability to tune the band gap of PbS in the visible range up to the IR band (0.65–2.28 eV) is a critical feature that holds the potential for the development of innovative optoelectronic devices.

INSIGHTS INTO THE WRITING PROCESS OF THE MASK-FREE NANOPRINTING FLUID FORCE MICROSCOPY TECHNOLOGY

Abstract Platelets are activated immediately when contacting with non-physiological surfaces. Minimization of surface-induced platelet activation is important not only for platelet storage but also for other blood-contacting devices and implants. Chemical surface modification tunes the response of cells to contacting surfaces, but it requires a long process involving many regulatory challenges to transfer into a marketable product. Biophysical modification overcomes these limitations by modifying only the surface topography of already approved materials. The available large and random structures on platelet storage bags do not cause a significant impact on platelets because of their smallest size (only 1-3 µm) compared to other cells. We have recently demonstrated the feasibility of the mask-free nanoprint fluid force microscope (FluidFM) technology for writing dot-grid and hexanol structures. Here, we demonstrated that the technique allows the fabrication of nanostructures of varying features including grid, circle, triangle, and Pacman-like structures. Characteristics of nanostructures including height, width, and cross-line were analyzed and compared using atomic force microscopy imaging. Based on the results, we identified several technical issues, such as the printing direction and shape of structures that directly altered nanofeatures during printing. Importantly, both geometry and interspace governed the degree of platelet adhesion, especially, the structures with triangular shapes and small interspaces prevent platelet adhesion better than others. We confirmed that FluidFM is a powerful technique to precisely fabricate a variety of desired nanostructures for the development of platelet/blood-contacting devices if technical issues during printing are well controlled.

Image-driven machine learning for automatic characterization of grain size and distribution in smart vanadium dioxide thin films

This study focuses on characterizing grain size and distribution in vanadium dioxide (VO2) thin films using Atomic Force Microscope (AFM) images. Traditional segmentation methods face challenges in accurately detecting grains, and this paper addresses these limitations by employing machine learning-based classification approaches, defining three classes: grains, joints or dividing lines, and the background. Various classification methods, including supervised, unsupervised, and thresholding-based approaches, were investigated, demonstrating the superiority of machine learning-based methods over traditional segmentation techniques. Deep Learning (DL) models, such as Convolutional Neural Networks (CNN), Deep Belief Networks (DBN), and Deep Boltzmann Machines (DBM), achieved the best results in accuracy and precision. The DBN algorithm, in particular, outperformed other methods with a 93.66% accuracy in grain detection. This could be attributed to its probabilistic modeling and effective handling of challenging pixels, making it a powerful tool for accurate grain size and distribution analysis.

How Does the Antibiotic Amphotericin B Enter Membranes and What Does It Do There?

Amphotericin B is a popular antifungal antibiotic, but the exact way it works is still a matter of debate. Here, we used monolayers composed of phosphatidylcholine with ergosterol as a model of fungal lipid membranes to study drug incorporation from the aqueous phase and analyze the molecular reorganization of membranes underlying the biological activity of the antibiotic. The results show that the internalization of antibiotic molecules into membranes occurs only in the presence of ergosterol in the lipid phase. Comparison of images of solid-supported monolayers obtained by atomic force microscopy and lifetime imaging fluorescence microscopy shows the formation of intramembrane clusters of various sizes in the lipid phase, consisting mainly of antibiotic dimers and relatively large membrane pores (∼15 nm in diameter). The results reveal multiple modes of action of amphotericin B, acting simultaneously, each of which adversely affects the structural properties of the lipid membranes and their physiological functionality.

Reconfigurable aqueous 3D printing with adaptive dual locks.

Using aqueous two-phase systems (ATPSs) for three-dimensional (3D) printed complex structures has attracted considerable attention in the field of biomedicine. In this study, we present an unusual approach to constructing reconfigurable 3D printed structures within an aqueous environment. Inspired by biological systems, we introduce both specific and nonspecific interactions to anchor functionalized nanoparticles to the water-water interface, thereby imparting adaptive dual locks of structural integrity and permeability to the 3D printed liquid structures. Using state-of-the-art in situ liquid-liquid interfacial atomic force microscopy imaging, we successfully demonstrate various morphologies of interfacial films formed at the ATPS interface. In addition, by incorporating d-glucose or sodium alginate into the systems, the dual locks can be easily manipulated. Our study paves a pathway for 3D printing multiresponsive all-aqueous systems with controllable structures and permeability, showing promising implications for the development of smart drug delivery systems and in vivo reactions.

Designing reduced graphene oxide decorated Ni doped δ-MnO2 nanocomposites for supercapacitor applications

Reduced Graphene Oxide (rGO) decorated δ-MnO2 and Ni-doped δ-MnO2 samples have been synthesized by a microwave-assisted co-precipitation technique which is low cost, simple and fast reaction method. The structural and morphological properties of synthesized samples have been characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). XRD result indicates that all samples have monoclinic crystal structure with δ phase of MnO2. The morphologies of MnO2 transformed into perforated porous nanoflakes with Ni doping and rGO composition in MnO2. AFM images confirmed that surface roughness for 3 % Ni-doped MnO2 samples is higher due to the chemical adsorption of samples. Raman spectroscopy results show the presence of vibrational and Raman active modes of MnO2.X-ray photoelectronic spectroscopy revealed the presence of mixed valencies of Mn such as Mn2+, Mn3+, and Mn4+ in prepared nanocomposites while Ni shows 2+ valency. The specific capacitance (Cs) of pure δ -MnO2 samples were 68 Fg-1 and rGO decorated 3 % Ni-doped MnO2 composition 694 Fg-1 at 10 mVs−1 respectively. EIS data of the rGO decorated Ni-doped MnO2 composition samples confirm that the porous nanoflake-shaped rGO decorated 3 % Ni-doped MnO2 composite sample has a low resistance value among all samples. These results reveal that rGO-decorated 3 % Ni-doped MnO2 nanoflakes should be a promising material for designing and fabricating the electrode material for high-performance supercapacitors.

Epitaxial AlN film with improved quality on Si (111) substrates realized by boron pretreatment via MOCVD

This study investigated the growth of AlN epitaxial films on 2-in. Si(111) via metal-organic chemical vapor deposition. By introducing triethylboron (TEB) during trimethylaluminum pretreatment, a nearly crack free AlN epilayer with a thickness of 500 nm was acquired. The x-ray diffraction rocking curves of AlN (002) and (102) exhibited full width at half maximum values of 0.22° and 0.36°, respectively. Atomic force microscopy image analysis showed that after the introduction of TEB, larger grains appeared on the surface of Si(111) substrate, promoting the 3D growth pattern of the subsequent AlN buffer layer. Laytec reflection curves depicted the morphological transition from 3D to 2D growth mode during AlN deposition. At the same time, the curvature value was significantly reduced by 20 km−1, and the Raman spectrum peak of E2(high) shifted from 648.7 to 652.5 cm−1, indicating that the surface tensile stress was greatly reduced, effectively suppressing the crack problem of AlN on Si(111).

Study of AlN Epitaxial Growth on Si (111) Substrate Using Pulsed Metal–Organic Chemical Vapour Deposition

A dense and smooth aluminium nitride thin film grown on a silicon (111) substrates using pulsed metal–organic chemical vapor deposition is presented. The influence of the pulsed cycle numbers on the surface morphology and crystalline quality of the aluminium nitride films are discussed in detail. It was found that 70 cycle numbers produced the most optimized aluminium nitride films. Field emission scanning electron microscopy and atomic force microscopy images show a dense and smooth morphology with a root-mean-square-roughness of 2.13 nm. The narrowest FWHM of the X-ray rocking curve for the AlN 0002 and 10–12 reflections are 2756 arcsec and 3450 arcsec, respectively. Furthermore, reciprocal space mapping reveals an in-plane tensile strain of 0.28%, which was induced by the heteroepitaxial growth on the silicon (111) substrate. This work provides an alternative approach to grow aluminium nitride for possible application in optoelectronic and power devices.

Corrosion behavior and surface structure analysis of pure aluminum immersed in fluoride‐sulfate solutions simulating polymer electrolyte membrane fuel cell‐produced water

AbstractBipolar plates are the key component in polymer electrolyte membrane fuel cells (PEMFCs), which ensure the low cost of the fuel cell stack and furnish some of the important applications such as distributing the reactant gases, conducting the electrons, and removing the waste heat in PEMFCs. Thus, metallic bipolar plates (BPs), such as aluminum (Al), have attracted immense consideration and afford better performance in different machine‐driven applications and mass manufacturing opportunities. In order to increase the corrosion resistance of Al BPs, several methods are used and conducted by scientists. The corrosion behavior and surface structure analysis of pure Al were studied through the immersion process in fluoride‐sulfate solutions, assuming its use as BPs in PEMFC‐produced water. The open cell voltage, interfacial contact resistance, and polarization tests and the fuel cell operations were performed to evaluate cell voltage, current density, corrosion resistance, and the effect of fluoride and sulfate ions on the BPs in PEMFC. The hydrophobicity character of the surface of Al BPs was observed by the measurement of the wettability test. The atomic force microscopy images were taken to study the surface roughness, which was correlated with the corrosion rates of Al BPs. In addition, the amount of corrosion was calculated after 24–120 h of immersion in fluoride‐sulfate solutions. The scanning electron microscopy, transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy data were analyzed to investigate the surface structure, morphology, and elemental analyses. Thus, the results found in this study revealed that Al‐based materials can be suitable for BPs in PEMFCs. Furthermore, it is noticed that the amount of corrosion was influenced by the presence of even a very small amount of fluoride ions present in the PEMFC environment, while it was suppressed efficiently by sulfate ions.

Morphology Observation of Two-Dimensional Monolayers of Model Proteins on Water Surface as Revealed by Dropping Method.

We have investigated the morphology of two-dimensional monolayers of gramicidin-D (GD) and alamethicin (Al) formed on the water surface by the dropping method (DM) using surface tension measurement (STm), Brewster angle microscopy (BAM), and atomic force microscopy (AFM). Dynamic light scattering (DLS) revealed that GD in alcoholic solutions formed a dimeric helical structure. According to the CD and NMR spectroscopies, GD molecules existed in dimer form in methanol and lipid membrane environments. The STm results and BAM images revealed that the GD dimer monolayer was in a liquid expanded (LE) state, whereas the Al monolayer was in a liquid condensed (LC) state. The limiting molecular area (A0) was 6.2 ± 0.5 nm2 for the GD-dimer and 3.6 ± 0.5 nm2 for the Al molecule. The AFM images also showed that the molecular long axes of both the GD-dimer and Al were horizontal to the water surface. The stability of each monolayer was confirmed by the time dependence of the surface pressure (π) observed using the STm method. The DM monolayer preparation method for GD-dimer and Al peptide molecules is a useful technique for revealing how the model biological membrane's components assemble in two dimensions on the water surface.

Atomic force microscopy 3D structural reconstruction of individual particles in the study of amyloid protein assemblies.

Recent developments in atomic force microscopy (AFM) image analysis have made three-dimensional (3D) structural reconstruction of individual particles observed on 2D AFM height images a reality. Here, we review the emerging contact point reconstruction AFM (CPR-AFM) methodology and its application in 3D reconstruction of individual helical amyloid filaments in the context of the challenges presented by the structural analysis of highly polymorphous and heterogeneous amyloid protein structures. How individual particle-level structural analysis can contribute to resolving the amyloid polymorph structure-function relationships, the environmental triggers leading to protein misfolding and aggregation into amyloid species, the influences by the conditions or minor fluctuations in the initial monomeric protein structure on the speed of amyloid fibril formation, and the extent of the different types of amyloid species that can be formed, are discussed. Future perspectives in the capabilities of AFM-based 3D structural reconstruction methodology exploiting synergies with other recent AFM technology advances are also discussed to highlight the potential of AFM as an emergent general, accessible and multimodal structural biology tool for the analysis of individual biomolecules.

Enhanced Photocatalytic and Filtration Performance of TiO2-Ag Composite-Coated Membrane Used for the Separation of Oil Emulsions

Polyvinylidene fluoride (PVDF) membranes were coated with TiO2 and TiO2-Ag to enhance their efficiency for oil-in-water emulsion separation. The photocatalytic activities of the two modified membranes and their filtration performances were compared in detail. The significantly enhanced photocatalytic activity of the TiO2-Ag composite was proved using a methyl orange (MO) solution (c = 10−5 M) and a crude oil emulsion (c = 50 mg·L−1). The TiO2-Ag-coated membrane reduced the MO concentration by 87%, whereas the TiO2-modified membrane reached only a 46% decomposition. The photocatalytic reduction in the chemical oxygen demand of the emulsion was also ~50% higher using the TiO2-Ag-coated membrane compared to that of the TiO2-coated membrane. The photoluminescence measurements demonstrated a reduced electron/hole recombination, achieved by the Ag nanoparticle addition (TiO2-Ag), which also explained the enhanced photocatalytic activity. A significant improvement in the oil separation performance with the TiO2-Ag-coated membrane was also demonstrated: a substantial increase in the flux and flux recovery ratio (up to 92.4%) was achieved, together with a notable reduction in the flux decay ratio and the irreversible filtration resistance. Furthermore, the purification efficiency was also enhanced (achieving 98.5% and 99.9% COD and turbidity reductions, respectively). Contact angle, zeta potential, scanning electron microscopy (SEM), and atomic force microscopy (AFM) measurements were carried out to explain the results. SEM and AFM images revealed that on the TiO2-Ag-coated membrane, a less aggregated, more continuous, homogeneous, and smoother nanolayer was formed due to the ~50% more negative zeta potential of the TiO2-Ag nanocomposite compared to that of the TiO2. In summary, via Ag addition, a sufficiently hydrophilic, beneficially negatively charged, and homogeneous TiO2-Ag-coated PVDF membrane surface was achieved, which resulted in the presented advantageous filtration properties beyond the photocatalytic activity enhancement.

Stochastic Assessment of Dissolution at Fluid‐Mineral Interfaces

AbstractChemical weathering associated with dissolution/precipitation at interfaces between minerals and flowing fluids is key for the evolution of geologic systems, including groundwater contamination and storage capacity. Relying on Atomic Force Microscopy (AFM) yields reaction rates at nanoscale resolutions. Challenges limiting our ability to quantify heterogeneity associated with these processes include establishing reliable platforms allowing AFM imaging of real‐time and in situ absolute material fluxes across mineral surfaces under continuous flow conditions to complement typically acquired surface topography images. We provide an experimental workflow and heterogeneous absolute rates at the nanoscale across the surface of a calcite crystal under dissolution. These high‐quality experimental observations are then interpreted through a stochastic approach. The latter is geared to embed diverse kinetic modes driving the degree of spatial heterogeneity of the reaction and corresponding to different mechanistic processes documented across the crystal surface.

Adaptive under-sampling strategy for fast imaging in compressive sensing-based atomic force microscopy

Compressive sensing (CS) can reconstruct the rest information almost without distortion by advanced computational algorithm, which significantly simplifies the process of atomic force microscope (AFM) scanning with high imaging quality. In common CS-AFM, the partial measurements randomly come from the whole region to be measured, which easily leads to detail loss and poor image quality in regions of interest (ROIs). Consequently, important microscopic phenomena are missed probably. In this paper, we developed an adaptive under-sampling strategy for CS-AFM to optimize the process of sampling. Under a certain under-sampling ratio, the weight coefficient of ROIs and regions of base (ROBs) were set to control the distribution of under-sampling points and corresponding measurement matrix. A series of simulations were completed to demonstrate the relationship between the weight coefficient of ROIs and image quality. After that, we verified the effectiveness of the method on our homemade AFM. Through a lot of simulations and experiments, we demonstrated how the proposed method optimized the sampling process of CS-AFM, which speeded up the process of AFM imaging with high quality.