Atomic Force Microscopy Techniques Research Articles

Synthesis, spectroscopic analysis and electrochemical studies of novel organic compound based on N-alkylphthalazinone chemistry as corrosion inhibitor for carbon steel in 1M HCl

The adsorption affinity and corrosion protection of two synthesized N-alkylphthalazinone derivatives 2(a-b), namely: 2-(prop-2-yn-1-yl)-4-(p-tolyl)phthalazin-1(2H)-one (a) and 4-(4-chlorophenyl)-2-(prop-2-yn-1-yl)phthalazin-1(2H)-one (b) on carbon steel (CS) in an acidic environment using electrochemical and mass loss methods. The mass loss test at the highest inhibitor concentration produced a maximum corrosion efficiency of 93.4% for inhibitor (a). Thermodynamic parameters were determined while the inhibitors' adsorption process was investigated. The inhibitory molecules adsorption on the CS substrate accompanied the Langmuir isotherm. As a function of inhibitor concentration, the thermodynamic activation functions of the dissolution process were calculated. Surface examination such as scanning electron microscopy (SEM), fourier transfer infrared spectroscopy (FTIR), and atomic force microscopy (AFM) techniques were used to confirm the adsorption phenomenon. Also investigated were quantum chemical parameters to approve the donor-acceptor system of the synthesized N-alkylphthalazinone derivatives. The theoretical values are in good correlation with the experimental values.

Comparative radiosensitization efficiency assessment of graphene oxide and Ti3C2 MXene as 2D carbon-based nanoparticles against breast cancer cells: characterization, toxicity and mechanisms

The efficacy of two carbon-based nanomaterials, graphene oxide (GO) and Ti3C2 MXene (MX), on the radiosensitivity of the breast cancer cells (BCCs) was investigated using clinical x-ray irradiation. The prepared GO and MX nanoparticles (NPs) were firstly characterized utilizing Fourier transform infrared, ultraviolet–visible, atomic force microscopy and transmission electron microscopy techniques and subsequently assessed in terms of their radiobiological properties. The results of the cell toxicity assay indicated that neither NPs exhibited significant cytotoxicity after 48 h incubation with BCC up to 50 µg ml−1 concentration without irradiation. The cell internalization results showed an approximately equivalent cellular uptake for both NPs after 6 h incubation with BCC. Our comparative studies with radiotherapy demonstrated that both NPs substantially increased cell proliferation inhibition and cell apoptosis of BCC under x-ray irradiation when compared to BCC treated with irradiation alone. Additionally, the 2ʹ,7ʹ-dichlorofluorescin diacetate flow cytometry results and fluorescent microscopy images revealed that both NPs remarkably increased the level of intracellular reactive oxygen species (ROS) generation in BCC under x-ray irradiation. The MX nanosheets exhibited superior radiosensitization efficiency than GO under x-ray irradiation due to its higher level of intracellular ROS generation (MX = 75.2% and GO = 65.2%). Clonogenic cell survival assay and extracted radiobiological parameters revealed that both NPs in combination with x-ray irradiation induced more lethal damage and less sublethal damage to BCC. Generally, the obtained results demonstrate that the MX NPs, as a stronger radiosensitizer than GO, could be a promising candidate for enhancing the effectiveness of radiotherapy in breast cancer treatment.

Identification of Supramolecular Structures of Porphyrin Polymer on Single-Walled Carbon Nanotube Surface Using Microscopic Imaging Techniques

Although the supramolecular structure of porphyrin polymers on flat surfaces (i.e., mica and HOPG) has been extensively studied, the self-assembly arrays of porphyrin polymers on the SWNT (as curved nanocarbon surfaces) have yet to be fully identified and/or investigated, especially using microscopic imaging techniques, i.e., scanning tunneling microscopy (STM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This study reports the identification of the supramolecular structure of poly-[5,15-bis-(3,5-isopentoxyphenyl)-10,20-bis ethynylporphyrinato]-zinc (II) on the SWNT surface using mainly AFM and HR-TEM microscopic imaging techniques. After synthesizing around >900 mer of porphyrin polymer (via Glaser-Hay coupling); the as-prepared porphyrin polymer is then non-covalently adsorbed on SWNT surface. Afterward, the resultant porphyrin/SWNT nanocomposite is then anchored with gold nanoparticles (AuNPs), which are used as a marker, via coordination bonding to produce a porphyrin polymer/AuNPs/SWNT hybrid. The polymer, AuNPs, nanocomposite, and/or nanohybrid are characterized using 1H-NMR, mass spectrometry, UV-visible spectroscopy, AFM, as well as HR-TEM measuring techniques. The self-assembly arrays of porphyrin polymers moieties (marked with AuNPs) prefer to form a coplanar well-ordered, regular, repeated array (rather than wrapping) between neighboring molecules along the polymer chain on the tube surface. This will help with further understanding, designing, and fabricating novel supramolecular architectonics of porphyrin/SWNT-based devices.

Combining atomic force microscopy with complementary techniques for multidimensional single-cell analysis.

The advent of atomic force microscopy (AFM) provides an amazing instrument for characterising the structures and properties of living biological systems under aqueous conditions with unprecedented spatiotemporal resolution. In addition to its own unique capabilities for applications in life sciences, AFM is highly compatible and has been widely integrated with various complementary techniques to simultaneously sense the multidimensional (biological, chemical and physical) properties of biological systems, offering novel possibilities for comprehensively revealing the underlying mechanisms guiding life activities particularly in the studies of single cells. Herein, typical combinations of AFM and complementary techniques (including optical microscopy, ultrasound, infrared spectroscopy, Raman spectroscopy, fluidic force microscopy and traction force microscopy) and their applications in single-cell analysis are reviewed. The future perspectives are also provided.

Effective Mg Incorporation in CdMgO Alloy on Quartz Substrate Grown by Plasma-Assisted MBE

The development of CdMgO ternary alloy with a single cubic phase is challenging but meaningful work for technological advancement. In this work, we have grown a series of Cd1-xMgxO ternary random alloys with various Mg concentrations (x = 0, 30, 32, 45, and 55%) on quartz substrate by plasma-assisted molecular beam epitaxy (PA-MBE) technique. The structural investigations of alloys were performed using the X-ray diffraction (XRD) technique. The decreases in average crystallite size and lattice parameters were observed with an increase in Mg content in the alloys. XRD analysis confirms a single cubic phase is obtained for alloy compositions. The elemental and morphological studies were carried out using energy dispersive x-ray (EDX) spectroscopy and atomic force microscope (AFM) technique, respectively. The optical investigation was carried out using UV-Vis spectroscopy. The optical bandgaps were estimated using the Tauc relation and it was varied from 2.34 eV to 3.47 eV by varying the Mg content from zero to 55% in the alloys. The Urbach energy increases from 112 meV to 350 meV which suggests a more disordered localized state with an increase in Mg incorporation in the alloys.

Correlation between Friction and Wear in Cylindrical Anchorages Simulated with Wear Machine and Analyzed with Scanning Probe and Electron Microscope.

This paper presents the possibilities of applying atomic force microscopy (AFM) techniques to the study of the wear of prosthetic biomaterials. In the conducted research, a zirconium oxide sphere was used as a test piece for mashing, which was moved over the surface of selected biomaterials: polyether ether ketone (PEEK) and dental gold alloy (Degulor M). The process was carried out with constant load force in an artificial saliva environment (Mucinox). An atomic force microscope with an active piezoresistive lever was used to measure wear at the nanoscale. The advantage of the proposed technology is the high resolution of observation (less than 0.5 nm) in the three-dimensional (3D) measurements in a working area of 50 × 50 × 10 µm. The results of nano wear measurements in two measurement setups are presented: zirconia sphere (Degulor M and zirconia sphere) and PEEK were examined. The wear analysis was carried out using appropriate software. Achieved results present a tendency coincident with the macroscopic parameters of materials.

Atomic force microscopy bending tests of a suspended rod-shaped object: Accounting for object fixing conditions.

The technique of atomic force microscopy (AFM) bending tests of a suspended nano-object (scroll, tube, rod) makes it possible to calculate the Young's modulus of the material it is made of based on experimental data. However, the calculation results involve a large error due to uncertain conditions (console or bridge) of fixing the test object. One of the ways to reduce this error is based on the theoretical consideration of consoles or bridges as beams with one or two ends resting on Winkler elastic foundations. The beam bending problems have been solved in both cases using Krylov's functions. This has allowed for developing an approach to the analytical identification of fixing conditions and including them in the calculations. The application of the approach is illustrated by AFM measurements of the Young's modulus of MgNi_{2}Si_{2}O_{5}(OH)_{4} nanoscrolls.

Quantification of interfacial structure at nanoscale and its relationship with viscoelastic glass transition of SiO2/elastomer nanocomposites

The interfacial structure and chain segment dynamics of nanofiller/polymer composites play an important role in their macroscopic properties. Nevertheless, the mechanisms on the effects of nanofiller on the chain segment dynamics and the glass transition temperature (Tg) of nanocomposites are still controversial. In this study, the interfacial structure (thickness and nanomechanical properties) of silica (SiO2)/solution polymerized butadiene styrene rubber (SSBR) composites were quantified by using quantitative nanomechanical mapping technique of atomic force microscopy. The quantitative relationship between the degree of graft of coupling agent (CA) on SiO2 and interfacial structure was built up. The formation mechanism of interfacial structure in SiO2/SSBR composites with different degree of graft on SiO2 was revealed. A new insight on the effect of interfacial interaction of polymer nanocomposites on their chain segment dynamics and Tg was proposed. With the increase in degree of graft, the interfacial thinkness largely increases, the dispersion of SiO2 is more homogeneous, and the total area of interfacial SSBR layer largely increases, resulting in the significant decrease in chain density of SSBR matrix, and thus a significant decrease in Tg. This study provides guidance for the interfacial design of high performance polymer nanocomposites for their wider application in industry.

Single-molecular insights into the breakpoint of cellulose nanofibers assembly during saccharification

Plant cellulose microfibrils are increasingly employed to produce functional nanofibers and nanocrystals for biomaterials, but their catalytic formation and conversion mechanisms remain elusive. Here, we characterize length-reduced cellulose nanofibers assembly in situ accounting for the high density of amorphous cellulose regions in the natural rice fragile culm 16 (Osfc16) mutant defective in cellulose biosynthesis using both classic and advanced atomic force microscopy (AFM) techniques equipped with a single-molecular recognition system. By employing individual types of cellulases, we observe efficient enzymatic catalysis modes in the mutant, due to amorphous and inner-broken cellulose chains elevated as breakpoints for initiating and completing cellulose hydrolyses into higher-yield fermentable sugars. Furthermore, effective chemical catalysis mode is examined in vitro for cellulose nanofibers conversion into nanocrystals with reduced dimensions. Our study addresses how plant cellulose substrates are digestible and convertible, revealing a strategy for precise engineering of cellulose substrates toward cost-effective biofuels and high-quality bioproducts.

Pancreatic Cancer Presents Distinct Nanomechanical Properties During Progression.

Cancer progression is closely related to changes in the structure and mechanical properties of the tumor microenvironment (TME). In many solid tumors, including pancreatic cancer, the interplay among the different components of the TME leads to a desmoplastic reaction mainly due to collagen overproduction. Desmoplasia is responsible for the stiffening of the tumor, poses a major barrier to effective drug delivery and has been associated with poor prognosis. The understanding of the involved mechanisms in desmoplasia and the identification of nanomechanical and collagen-based properties that characterize the state of a particular tumor can lead to the development of novel diagnostic and prognostic biomarkers. In this study, in vitro experiments were conducted using two human pancreatic cell lines. Morphological and cytoskeleton characteristics, cells' stiffness and invasive properties were assessed using optical and atomic force microscopy techniques and cell spheroid invasion assay. Subsequently, the two cell lines were used to develop orthotopic pancreatic tumor models. Tissue biopsies were collected at different times of tumor growth for the study of the nanomechanical and collagen-based optical properties of the tissue using Atomic Force Microscopy (AFM) and picrosirius red polarization microscopy, respectively. The results from the in vitro experiments demonstrated that the more invasive cells are softer and present a more elongated shape with more oriented F-actin stress fibers. Furthermore, ex vivo studies of orthotopic tumor biopsies on MIAPaCa-2 and BxPC-3 murine tumor models highlighted that pancreatic cancer presents distinct nanomechanical and collagen-based optical properties relevant to cancer progression. The stiffness spectrums (in terms of Young's modulus values) showed that the higher elasticity distributions were increasing during cancer progression mainly due desmoplasia (collagen overproduction), while a lower elasticity peak was evident -due to cancer cells softening- on both tumor models. Optical microscopy studies highlighted that collagen content increases while collagen fibers tend to form align patterns. Consequently, during cancer progression nanomechanical and collagen-based optical properties alter in relation to changes in collagen content. Therefore, they have the potential to be used as novel biomarkers for assessing and monitoring tumor progression and treatment outcomes.

Bottom-Up Generated Height Gauges for Silicon-Based Nanometrology.

Steady progress in integrated circuit design has forced basic metrology to adopt silicon lattice parameter as a secondary realization of the SI meter that lacks convenient physical gauges for precise surface measurements at a nanoscale. To employ this fundamental shift in nanoscience and nanotechnology, we propose a set of self-organized silicon surface morphologies as a gauge for height measurements within the whole nanoscale (0.3-100 nm) range. Using 2 nm sharp atomic force microscopy (AFM) probes, we have measured the roughness of wide (up to 230 μm in diameter) singular terraces and the height of monatomic steps on the step-bunched and amphitheater-like Si(111) surfaces. For both types of self-organized surface morphology, the root-mean-square terrace roughness exceeds 70 pm but has a little effect on step height measurements having 10 pm accuracy for AFM technique in air. We implement a step-free 230-μm-wide singular terrace as a reference mirror in an optical interferometer to reduce the systematic error of height measurements from >5 nm to about 0.12 nm, which allows visualizing 136-pm-high monatomic steps on the Si(001) surface. Then, using a "pit-patterned" extremely wide terrace with dense but counted monatomic steps in a pit wall, we have optically measured mean Si(111) interplanar spacing (313.8 ± 0.4 pm) that agrees well with the most precise metrological data (313.56 pm). This opens up avenues for the creation of silicon-based height gauges using bottom-up approaches and advances optical interferometry among techniques for metrology-grade nanoscale height measurements.

In Situ Atomic Force Microscopy and X‐ray Computed Tomography Characterization of All‐Solid‐State Lithium Batteries: Both Local and Overall

All‐solid‐state lithium batteries (ASSLBs) are promising due to their high‐energy output and low‐risk profile, but their development has only just begun. Atomic force microscopy (AFM) and related techniques have had an impact on ASSLBs research by elucidating the interfacial, morphological, mechanical, electrical, and electrochemical properties of a wide range of electrodes and electrolytes. However, because a cross‐section cut is necessary to define the solid–solid interface, true in situ analysis is not practical. The first part of this review will assess recent advancements in the study of ASSLBs utilizing AFM and other scanning probe microscopy techniques. The interior solid–solid interfaces can be illuminated in situ using X‐ray computed tomography (X‐CT) and other nondestructive characterization techniques, whereas, in contrast, to deepen the subject, it is further examined how X‐CT vary from the use of other instruments for solid‐state battery characterization, compare the information that various methods may give, and assess how well they can accurately reflect real batteries. This review may serve as a reference and point researchers in the direction of future study on the solid–solid interface of ASSLBs.

Enhancing the precision of 3D sidewall measurements of photoresist using atomic force microscopy with a tip-tilting technique

A key issue associated with advanced lithography techniques for semiconductor-device manufacturing is the reduction in the sidewall roughness of photoresist line patterns, known as line-edge roughness (LER). We have developed a technique for measuring the sidewall of the resist pattern using atomic force microscopy (AFM) that enables three-dimensional (3D), high-resolution, low-noise, and nondestructive measurements. Conventional LER measurement technology using scanning electron microscopy (SEM) causes shrinkage of the resist pattern due to electron-beam (EB) exposure, whereas our new AFM technique can in principle avoid EB-induced shrinkage. This AFM technology is capable of 3D measurements because it employs a tip-tilting mechanism that enables the sharp AFM tip to scan the vertical sidewalls, which is difficult for a conventional AFM technique. In addition, laser interferometers are equipped for the measurement of the AFM tip displacement, which yields high-resolution, high-accuracy, and low-noise results. This technology overcomes issues such as low resolution, noise, and destructive measurements that afflict conventional SEM measurements. In addition, it enables observations and quantitative analyses of the 3D sidewall roughness. For example, in the present experiment, we observed that grain shapes (several tens of nm in size) were formed randomly on the resist sidewall and that there were almost no footing shapes. By analyzing the sidewall profiles with a height resolution of 1 nm, we obtain the roughness (self-affine fractal) parameters at each height. This AFM-based resist sidewall measurement technique can, thus, provide important insights into resist patterning and related process technologies for next-generation semiconductor-device manufacturing.

アスファルテン分子モデルの変遷

This paper reviews the average molecular models of asphaltene proposed in past years, and introduces recent results of individual molecular structure analyses. The understanding of the asphaltene molecular structure has evolved as analytical techniques advance. In around 2016, modern mass spectrometry ended the controversy over whether island-type or archipelago-type molecules are correct, and clarified the diversity in chemical composition. Atomic force microscopy techniques can now determine individual molecular structures. The historical changes in our understanding of asphaltene are summarized in five stages (Asphaltene 1.0∼5.0).

Single bubble probe atomic force microscope and impinging-jet technique unravel the interfacial interactions controlled by long chain fatty acid in anaerobic digestion

Anaerobic digestion of lipid-rich wastewater generally suffers from foaming induced by long chain fatty acid (LCFA). However, a systematic understanding of LCFA inhibition, especially the physical inhibition on interfacial interaction still remains unclear. Here, we combined bubble probe atomic force microscope and impinging-jet technique to unravel the interfacial interactions controlled by long chain fatty acids in anaerobic digestion. We showed that LCFA had a significant inhibition on methane production in anaerobic reactors for the inhibition of the conversion of VFAs to methane. By measuring the LCFA influence on methanogenic archaea Methanosarcina acetivorans C2A, the results demonstrated that methanogenesis was limited for substrates utilization but not metabolic pathways. The impinging-jet technique results indicated that LCFA enhanced bubble separation from anaerobic granules and reduced the bubble-bubble coalescence probability. In addition, the bubble probe atomic force microscope (AFM) revealed that LCFA enhanced the adhesion force between bubbles by enhancing electrical double layer (EDL) repulsion and decreasing hydrophobic interactions. Overall, these results complement framework of LCFA inhibition in anerobic digestion and provide a nanomechanical insight into the fundamental interfacial interactions related to bubbles in anaerobic reactors.

Protein Nanofibrils from Fava Bean and Its Major Storage Proteins: Formation and Ability to Generate and Stabilise Foams.

Protein nanofibrils (PNFs) have potential for use in food applications as texture inducers. This study investigated the formation of PNFs from protein extracted from whole fava bean and from its two major storage proteins, globulin fractions 11S and 7S. PNFs were formed by heating (85 °C) the proteins under acidic conditions (pH 2) for 24 h. Thioflavin T fluorescence and atomic force microscopy techniques were used to investigate PNF formation. The foaming properties (capacity, stability, and half-life) were explored for non-fibrillated and fibrillated protein from fava bean, 11S, and 7S to investigate the texturing ability of PNFs at concentrations of 1 and 10 mg/mL and pH 7. The results showed that all three heat-incubated proteins (fava bean, 11S, and 7S) formed straight semi-flexible PNFs. Some differences in the capacity to form PNFs were observed between the two globulin fractions, with the smaller 7S protein being superior to 11S. The fibrillated protein from fava bean, 11S, and 7S generated more voluminous and more stable foams at 10 mg/mL than the corresponding non-fibrillated protein. However, this ability for fibrillated proteins to improve the foam properties seemed to be concentration-dependent, as at 1 mg/mL, the foams were less stable than those made from the non-fibrillated protein.

Influence of InP/ZnS Quantum Dots on Thermodynamic Properties and Morphology of the DPPC/DPPG Monolayers at Different Temperatures.

In this work, the effects of InP/ZnS quantum dots modified with amino or carboxyl group on the characteristic parameters in phase behavior, elastic modulus, relaxation time of the DPPC/DPPG mixed monolayers are studied by the Langmuir technology at the temperature of 37, 40 and 45 °C. Additionally, the information on the morphology and height of monolayers are obtained by the Langmuir-Bloggett technique and atomic force microscope technique. The results suggest that the modification of the groups can reduce the compressibility of monolayers at a higher temperature, and the most significant effect is the role of the amino group. At a high temperature of 45 °C, the penetration ability of InP/ZnS-NH2 quantum dots in the LC phase of the mixed monolayer is stronger. At 37 °C and 40 °C, there is no clear difference between the penetration ability of InP/ZnS-NH2 quantum dots and InP/ZnS-COOH quantum dots. The InP/ZnS-NH2 quantum dots can prolong the recombination of monolayers at 45 °C and accelerate it at 37 °C and 40 °C either in the LE phase or in the LC phase. However, the InP/ZnS-COOH quantum dots can accelerate it in the LE phase at all temperatures involved but only prolong it at 45 °C in the LC phase. This work provides support for understanding the effects of InP/ZnS nanoparticles on the structure and properties of cell membranes, which is useful for understanding the behavior about the ingestion of nanoparticles by cells and the cause of toxicity.

Strengthening Polylactic Acid by Salification: Surface Characterization Study.

Polylactic acid (PLA) is one of the market's most commonly used biodegradable polymers, with diverse applications in additive manufacturing, specifically fused deposition modeling (FDM) 3D printing. The use of PLA in complex and sophisticated FDM applications is continually growing. However, the increased range of applications requires a better understanding of the material properties of this polymer. For example, recent studies have shown that PLA has the potential to be used in artificial heart valves. Still, the durability and longevity of this material in such a harsh environment are unknown, as heart valve failures have been attributed to salification. Additionally, there is a gap in the field for in situ material characterization of PLA surfaces during stiffening. The present study aims to benchmark different dynamic atomic force microscopy (AFM) techniques available to study the salification phenomenon of PLA at micro-scales using different PLA thin films with various salt concentrations (i.e., 10%, 15%, and 20% of sodium chloride (NaCl)). The measurements are conducted by tapping mode AFM, bimodal AFM, the force spectroscopy technique, and energy quantity analysis. These measurements showed a stiffening phenomenon occurring as the salt solution is increased, but the change was not equally sensitive to material property differences. Tapping mode AFM provided accurate topographical information, while the associated phase images were not considered reliable. On the other hand, bimodal AFM was shown to be capable of providing the topographical information and material compositional mapping through the higher eigenmode's phase channel. The dissipated power energy quantities indicated that how the polymers become less dissipative as salt concentration increases can be measured. Lastly, it was shown that force spectroscopy is the most sensitive technique in detecting the differences in properties. The comparison of these techniques can provide a helpful guideline for studying the material properties of PLA polymers at micro- and nano-scales that can prove beneficial in various fields.

Determining Spatial Variability of Elastic Properties for Biological Samples Using AFM.

Measuring the mechanical properties (i.e., elasticity in terms of Young's modulus) of biological samples using Atomic Force Microscopy (AFM) indentation at the nanoscale has opened new horizons in studying and detecting various pathological conditions at early stages, including cancer and osteoarthritis. It is expected that AFM techniques will play a key role in the future in disease diagnosis and modeling using rigorous mathematical criteria (i.e., automated user-independent diagnosis). In this review, AFM techniques and mathematical models for determining the spatial variability of elastic properties of biological materials at the nanoscale are presented and discussed. Significant issues concerning the rationality of the elastic half-space assumption, the possibility of monitoring the depth-dependent mechanical properties, and the construction of 3D Young's modulus maps are also presented.

Microstructural modelling and characterisation of laser-keyhole welded Eurofer 97

The novel reduced activation ferritic/martensitic steel Eurofer 97 is employed by many concept designs for the plasma-facing first wall of the EU DEMO fusion reactor. These designs feature precision joints between Eurofer 97 coolant piping, for which an advanced laser-keyhole welding technique is proposed. In this work the microstructure of these novel laser-keyhole Eurofer 97 welds is modelled by combining finite element thermal analysis with precipitate kinetics modelling. Microanalysis of a representative specimen via scanning electron and high-speed atomic force microscopy techniques is also conducted, complimented by electron backscatter diffraction, energy-dispersive X-ray spectroscopy, and nanoindentation hardness testing. Models of the weld microstructure agree well with the results of microanalysis although the precipitate diameters predicted are slightly underestimated. Several large void defects were discovered within the weld fusion zone, the cause of which is suspected to arise from the evaporation of cerium-rich oxide inclusions present in the as-cast Eurofer 97 during welding.