Surface Atomic Force Microscopy Research Articles

Copper doped hydroxyapatite nanocomposite thin films: synthesis, physico-chemical and biological evaluation.

Cu-doped hydroxyapatite (CuHAp) thin films were obtained using spin coating method. To make these thin films, CuHAp suspensions obtained by sol-gel method were used. The coatings obtained were thermally treated at 500°C. After the thermal treatment, the thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). Moreover, the stability of the suspensions before being used to obtain the thin films was certified by dynamic light scattering (DLS), zeta potential methods and ultrasound measurements. In the XRD patterns, the peaks associated with hexagonal hydroxyapatite were identified in accordance with JCPDS no. 09-0432. EDS and XPS results confirmed the presence of Cu ions in the samples. Data about the morphological features and chemical composition of CuHAp thin films were obtained by performing scanning electron microscopy (SEM) measurements. Our results suggest that the CuHAp thin films surface is continuous and homogenous. The presence of the functional groups in the CuHAp thin films was confirmed by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy studies. Information about the surface topography of the CuHAp thin films has been obtained using atomic force microscopy (AFM). The AFM images determined that the surface topography of the CuHAp thin layer is homogenous and continuous without presenting any unevenness or fissures. The cytotoxicity of CuHAp thin films was assessed using human gingival fibroblasts (HGF-1) cells. The results of the cell viability assays demonstrated that the thin films presented good biocompatible properties towards the HGF-1 cells. Additionally, the adherence and development of HGF-1 cells on the surface of CuHAp thin films were determined using AFM. The AFM surface topographies highlighted that the CuHAp thin film's surface favored the attachment and proliferation of HGF-1 cells on their surface.

Growth phase-dependent changes in conformational and physicochemical properties of bacterial surface biopolymers lead to changes in bacterial adhesion strength at nanoscale and macroscale

This study presents a detailed investigation into conformational, physicochemical and adhesive characteristics of biopolymers on the surfaces of Escherichia coli and potential probiotic Bacillus subtilis harvested from middle-exponential phase (mid-EP), late-exponential phase (late-EP) and early-stationary phase (early-SP) of growth. The lengths to which bacterial surface biopolymers extend (biopolymer brush lengths), densities of grafted bacterial surface biopolymers indicating the amounts of molecules covering the bacterial surfaces (biopolymer grafting densities), adhesion forces of bacterial surface biopolymers to the model inert surfaces of silicon nitride (Si3N4), and the pull-off distances of biopolymers from Si3N4 were measured in water by atomic force microscopy (AFM). The Weibull analysis of AFM adhesion data showed that as the culture aged, the adhesive bonds between Si3N4 AFM tips and surface molecules of E. coli harvested from the culture were broken with a higher applied force. However, the highest applied force to break the bonds was required for B. subtilis in late-EP, followed by those required for cells in early-SP and mid-EP, respectively. The results of a steric model fitting to AFM approach force-distance (FD) curves and analysis of the pull-off distances in the AFM retraction FD curves showed higher biopolymer grafting density for E. coli in early-SP and longer biopolymer brush layer for B. subtilis in late-EP, which were associated with stronger adhesion to Si3N4 in water. The results of thermodynamic adhesion energy calculations based on the Wu model showed that polar interaction energy dominated the bacterial adhesion at the macroscale, the strength of which varied as a function of the growth phase for both E. coli and B. subtilis. The growth phase-dependent variation in polar components of thermodynamic adhesion energies between the bacteria and Si3N4 in water was consistent with the growth phase-dependent variation in the bond strengths between the bacteria and Si3N4 in water as revealed by the Weibull analysis of AFM adhesion data. Therefore, information obtained by Weibull analysis of nanoscale AFM bacterial adhesion data can be used to predict macroscale bacterial adhesion to the model inert Si3N4 surface in water.

Localized surface plasmon resonance and atomic force microscopy study of model lipid membranes and their interactions with amyloid and melatonin

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by the accumulation of amyloid plaques in the brain. The toxicity of amyloid to neuronal cell surfaces arises from interactions between small intermediate aggregates, namely amyloid oligomers, and the cell membrane. The nature of these interactions changes with age and disease progression. In our previous work, we demonstrated that both membrane composition and nanoscale structure play crucial roles in amyloid toxicity, and that membrane models mimicking healthy neuron were less affected by amyloid than model membranes mimicking AD neuronal membranes. This understanding introduces the possibility of modifying membrane properties with membrane-active molecules, such as melatonin, to protect them from amyloid-induced damage. In this study, we employed atomic force microscopy and localized surface plasmon resonance to investigate the protective effects of melatonin. We utilized synthetic lipid membranes that mimic the neuronal cellular membrane at various stages of AD and explored their interactions with amyloid-β (1–42) in the presence of melatonin. Our findings reveal that the early diseased membrane model is particularly vulnerable to amyloid binding and subsequent damage. However, melatonin exerts its most potent protective effect on this early-stage membrane. These results suggest that melatonin could act at the membrane level to alleviate amyloid toxicity, offering the most protection during the initial stages of AD.

Atomic force microscopy and transmission electron microscopy identification of deformation twinning in the Cr2AlC MAX phase

Elementary deformation mechanisms have been investigated in a single-crystalline Cr2AlC MAX phase. Plastic deformation has been induced at room temperature by spherical nanoindentation, with a crystal orientation chosen to minimize basal slip and to promote local crystal reorientation. The combination of Atomic Force Microscopy (AFM) surface observation, Transmission Electron Microscopy (TEM) characterization and Automated Crystal Orientation Mapping (ACOM) in a same region has provided a full 3D characterization of the deformation microstructure. Localized and isolated deformation twins have been identified below the indents. The whole microstructure consists in interactions between dislocations and {112¯4} twin variants. The TEM analysis also revealed activation of a 13〈112¯0〉{1¯103} slip system never reported before in a MAX phase.

Oleaster Leaf Extract: A Potential Environmentally Friendly Inhibitor for Mild Steel

In this research, the potential of Elaeagnus angustifolia tree leaf extract as a green corrosion inhibitor for mild steel in hydrochloric acid solution was examined. The stock concentration of the aqueous extract was determined to be 0.38% (w/v). Other experimental solutions were created by diluting four different extract concentrations in aggressive solution. Experimental measurements, including linear polarization (LPR), electrochemical impedance spectroscopy (EIS), and semi-logarithmic current potential curves by Tafel extrapolation method, were employed to validate the corrosion inhibition effects of the plant leaf extract at varying concentrations. Notably, oleaster leaf extract demonstrated a corrosion protection of over 90% for 0.018% w/v concentration on the mild steel, attributed to its abundance in secondary metabolites such as polyphenols and flavonoids. The atomic force microscopy (AFM) surface maps provide robust evidence for the electrochemical measurement data.

Characterizing steel corrosional features in atomic force microscopy: A Sobel edge detection approach

One of the fundamental characterizations in assessing a material’s surface its surface roughness. Here, we introduce a computational method using measured atomic force microscopy surface roughness data to perform Sobel edge detection of heterogeneity on corroded steel samples. This method enables the spatial mapping of corrosion-induced features and general inconsistencies on a sample’s surface using a freely available algorithm written in the Python computing language. The non-optical method has been tested on three different grades of steel, and results indicate reasonable accuracy when compared to visual observations made from grayscale optical data.

Promising Eco-friendly Inhibitor Potency: Elaeagnus Angustifolia Leaf Extract for Mild Steel

In this research, the potential of Elaeagnus angustifolia tree leaf extract as a green corrosion inhibitor for mild steel in hydrochloric acid solution was examined. The stock concentration of the aqueous extract was determined to be 0.38% (w/v). Other experimental solutions were created by diluting four different extract concentrations in aggressive solution. Experimental measurements, including linear polarization (LPR), electrochemical impedance spectroscopy (EIS), and semi-logarithmic current potential curves by Tafel extrapolation method, were employed to validate the corrosion inhibition effects of the plant leaf extract at varying concentrations. Notably, oleaster leaf extract demonstrated a corrosion protection of over 80% for mild steel, even at low concentrations, attributed to its abundance in secondary metabolites such as polyphenols and flavonoids. The atomic force microscopy (AFM) surface maps provide robust evidence for the electrochemical measurement data.

Surface modification of fully austenitic stainless steel SMO 254 by laser shock peening to induce compressive residual stress

ABSTRACT The laser shock peening process was conducted with varying pulse densities on the SMO 254 material. The formation of an α martensitic layer from the austenitic structure was witnessed after conducting the laser shock peening process, with the migration of elements across the grains. The increase in the surface roughness value, measured by the Atomic force microscope and Mahr surface profilometer, is directly proportional to the rise in pulse density. An elevated value of compressive residual stress of −786 MPa and a higher Vickers micro hardness value of 365 HV were obtained in the specimen where a pulse density of 6000 pulse/cm2 was applied.

Optimization of visible photoluminescence emission from Ni-Zn ferrite thin films

Ni-Zn ferrite films with different thicknesses were prepared by the spray method, aiming to study the relationship between the annealing effect in an oxygen rich environment and the structural, optical properties and photoluminescence emission. X-ray diffraction (XRD) analysis used with Rietveld refinement showed that all prepared samples had a single spinel phase structure. Likewise, the Fourier transform infrared (FTIR) spectra confirmed the phase formation of Ni-Zn ferrites by appearing in both of the two characteristic absorption bands which are related to the tetrahedral and octahedral sites. For annealed thin film samples of Ni-Zn ferrite, the atomic force microscope (AFM) surface morphology exhibits pinning structure on the surface in nanoscale height, whereas for un-annealed samples, there are hills and valleys cover a broad region. The different electronic transitions were estimated from the UV-visible transmission spectrum. Strong photoluminescence (PL) intensity in the visible range was observed under the excitation of UV radiation. The intensity of the PL signal was strongest at a film thickness of 750 nm then decreased for higher thicknesses. This could be interpreted by using proposed energy level structures based on the transmission spectrum of the investigated samples. The strong PL intensity introduces the samples as a direct optical detector for UV radiation.

Influence of the reference surface and AFM tip on the radius and roundness measurement of micro spheres

The performance of tactile and optical surface sensors for nano and micro coordinate measuring machines is currently limited by the lack of precisely characterised micro spheres, since established strategies have mainly been developed for spheres in the range of millimetres or above. We have, therefore, recently focused our research efforts towards a novel strategy for the characterisation of spheres in the sub-millimetre range. It is based on a set of atomic force microscope (AFM) surface scans in conjunction with a stitching algorithm. To obtain an uncertainty statement, the uncertainty about the shape of the reference surface needs to be propagated via the shape of the AFM tip to the actual measurement object. However, the sampling process of an AFM is non-linear and the processing of AFM scans requires complex algorithms. We have, therefore, recently begun to model the characterisation of micro spheres through simulations. In this contribution, this model is extended by the influence of the tip and reference surface. The influence of the tip’s shape and reference surface is investigated through virtual and real experiments. The shape of the tip is varied by using tips with mean radii of 200 nm and 2 μm while sampling the same ruby sphere with a mean radius of 150 μm. In general, the simulation results imply that an uncertainty of less then 10 nm is achievable. However, an experimental validation of the model is still pending. The experimental investigations were limited by the lack of a suitable cleaning strategy for micro parts, which demonstrates the need for further investigations in this area. Although the characterisation of a full sphere has already been demonstrated, the investigations in this contribution are limited to equator measurements.

Oxygen vacancy induced conductivity in Sr n+1Ti n O3n+1/SrTiO3 heterostructures

SrTiO3-based heterostructures have attracted much attention due to the abundant properties compared to single components. Here, we fabricate oxide heterostructure of layed perovskite/perovskite Sr n+1Ti n O3n+1/SrTiO3 and investigate the n value-dependent and thickness-dependent conductivity. X-ray diffraction peaks and reflective high energy electron diffraction indicate good film quality. For films of n=6, the heterostructures are conductive, and the conductivity is better for thicker film. On the contrary, heterostructures with films of n=1, 2, 3, 4, ∞ are insulating. Conductive atomic force microscopy results and surface conductivity tests manifest that the oxygen vacancy induced conductive layer exists near the interface between film and substrate. This work provides feasible method to modulate the transport properties of functional transition metal oxides.

Remineralization Induced by Biomimetic Hydroxyapatite Toothpastes on Human Enamel.

This work aimed to compare the effect of four new toothpastes (P1-P4) based on pure and biomimetic substituted nano-hydroxyapatites (HAPs) on remineralization of human enamel. Artificially demineralized enamel slices were daily treated for ten days with different toothpastes according to the experimental design. Tooth enamel surfaces were investigated using atomic force microscope (AFM) images and surface roughness (Ra) determined before and after treatment. The surface roughness of enamel slices was statistically analyzed by one-way ANOVA and Bonferroni's multiple comparison test. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) data revealed the HAP structure with crystal sizes between 28 and 33 nm and crystallinity between 29 and 37%. The average size of HAP particles was found to be between 30 and 40 nm. The Ra values indicated that P3 (HAP-Mg-Zn-Sr-Si) toothpaste was the most effective after 10 days of treatment, leading to the lowest mean roughness. The P3 and P2 (HAP) toothpastes were found to be effective in promoting remineralization. Specifically, their effectiveness can be ranked as follows: P3 = P2 > P4 (HAP-Mg-Zn-Si) > P1 (HAP-Zn), considering both the chemical composition and the size of their constitutive nanoparticles. The proposed toothpastes might be used successfully to treat early tooth decay.

Shear-reversible clusters of HIV-1 in solution: stabilized by antibodies, dispersed by mucin.

The phenomenon of reversible clustering is expected to further nuance HIV immune stealth because virus surfaces can escape interaction with antibodies (Abs) by hiding temporarily within clusters. It is well known that mucin reduces HIV virulence, and the current perspective is that mucin aggregates HIV-1 to reduce infections. Our findings, however, suggest that mucin is dispersing HIV clusters. The study proposes a new paradigm for how HIV-1 may broadly evade Ab recognition with reversible clustering and why mucin effectively neutralizes HIV-1.

In-situ graphene oxide reduction via inkjet printing using natural reducing inks

The development of eco-friendly alkali lignin-assisted water-based stable graphene oxide (GO) ink presents an innovative approach with the potential to revolutionize the manufacturing of printed and flexible electronics through scalable inkjet printing. However, GO lacks conductivity, necessitating an additional reduction step to restore its electrical properties. Traditional reduction methods using toxic agents or high temperatures are not suitable for large-scale manufacturing due to environmental hazards. In-situ reduction techniques using natural substances offer a promising, cost-effective, and continuous solution for precise reduction of GO-printed patterns via inkjet printing. However, limited research has been conducted on natural-based inkjet printable reducing inks. In this work, in-situ inkjet printable natural reducing inks were produced and printed on top of GO-printed patterns to carry out the reduction process. The reduced printed patterns were investigated for structural, functional groups, morphology, and electrical resistance. The ascorbic acid reduced sample showed an increase in the I D/I G ratio from 1.058 to 1.15, and the interlayer distance decreased from 0.395 to 0.385 nm. The atomic force microscope surface analysis showed a significant increase in the mean roughness by three times for the ascorbic acid-reduced sample, indicating success in the reduction process. The ascorbic acid reduced patterns also showed an electrical conductivity of 1250 S m−1 compared to 0.43 S m−1 for unreduced GO printed patterns, indicating restoration of the sp2 hybridised conductive networks.

Influence of in-situ annealing temperature upon structural, micro-structural, magnetic damping properties in sputtered Fe3O4 thin films

The influence of in-situ annealing temperature upon structural, micro-structural, magnetic properties and Gilbert damping parameters of sputtered Fe3O4 thin films (29–49 nm) upon SiO2/Si substrates have been systematically investigated. The oriented Fe3O4 structural phase was evaluated using grazing incidence X-ray diffraction, confocal Raman spectroscopy and X-ray photoelectron spectroscopy data. The atomic force and field-emission scanning electron microscope surface microstructural images reveal an enhanced grain growth with dominant anti-phase boundaries (APB) with in-situ annealing. The macroscopic spin dynamical response is evaluated using co-planar waveguide ferromagnetic resonance (CPW-FMR) spectroscopy from 15 to 35 GHz frequencies. The FMR data reveals a low Gilbert damping (α) ranging from 0.003 ± 0.001 to 0.009 ± 0.006 for all the in-situ annealed Fe3O4 thin films. Further, high inhomogeneity (ΔH0) parameter is correlated to the surface defects and APBs.

Atomic force microscopy analysis on Hardox alloy using LBM process

Atomic force microscopy (AFM) analysis plays an essential role to investigate the surface investigation of alloy and different composition of materials. The surface quality characteristics of the alloys depend upon the different AFM surface factors. The present paper discusses the surface investigation on laser beam machined area of the hardox steel 450. The surface quality of the machined component is depends on the different alloying element present in the composition. Laser power, cutting speed and pulse duration of the LBM factors were used to enhance the surface profile. The surface was analyzed at laser power of 1500, 2000, 2500 W, cutting speed of 800, 900, 1000 mm/min and pulse duration of 50,100,150 ns. The moderate surface roughness was attained for Hardox steel at medium level of LBM factors. Average roughness of 15.17 µm was attained at laser power of 2500 W, cutting speed of 1000 mm/min and pulse duration of 150 ns.

Investigating the Inhibitory Properties of Cupressus sempervirens Extract against Copper Corrosion in 0.5 M H2SO4: Combining Quantum (Density Functional Theory Calculation-Monte Carlo Simulation) and Electrochemical-Surface Studies.

The study investigates the potential of Cupressus sempervirens (EO) as a sustainable and eco-friendly inhibitor of copper corrosion in a 0.5 M sulfuric acid medium. The electrochemical impedance spectroscopy analysis shows that the effectiveness of corrosion inhibition rises with increasing inhibitor concentrations, reaching 94% with the application of 2 g/L of EO, and potentiodynamic polarization (PDP) studies reveal that EO functions as a mixed-type corrosion inhibitor. In addition, the Langmuir adsorption isotherm is an effective descriptor of its adsorption. Scanning electron microscopy/energy-dispersive X-ray spectroscopy, atomic force microscopy surface examination, and contact angle measurement indicate that EO may form a barrier layer on the metal surface. Density functional theory calculations, Monte Carlo simulation models, and the radial distribution function were also used to provide a more detailed understanding of the corrosion protection mechanism. Overall, the findings suggest that Cupressus sempervirens (EO) has the potential to serve as an effective and sustainable corrosion inhibitor for copper in a sulfuric acid medium, contributing to the development of green corrosion inhibitors for environmentally friendly industrial processes.

Detection of Listeria monocytogenes in foods with a textile organic electrochemical transistor biosensor

Foods contaminated by pathogens are responsible for foodborne diseases which have socioeconomic impacts. Many approaches have been extensively investigated to obtain specific and sensitive methods to detect pathogens in food, but they are often not easy to perform and require trained personnel. This work aims to propose a textile organic electrochemical transistor-based (OECT) biosensor to detect L. monocytogenes in food samples. The analyses were performed with culture-based methods, Listeria Precis™ method, PCR, and our textile OECT biosensor which used poly(3,4-ethylenedioxythiophene) (PEDOT):polystyrene sulfonate (PSS) (PEDOT:PSS) for doping the organic channel. Atomic force microscopy (AFM) was used to obtain topographic maps of the gold gate. The electrochemical activity on gate electrodes was measured and related to the concentration of DNA extracted from samples and hybridized to the specific capture probe immobilized onto the gold surface of the gate. This assay reached a limit of detection of 1.05 ng/μL, corresponding to 0.56 pM of L. monocytogenes ATCC 7644, and allowed the specific and rapid detection of L. monocytogenes in the analyzed samples.Keypoints• Textile organic electrochemical transistors functionalized with a specific DNA probe• AFM topographic and surface potential maps of a functionalized gold gate surface• Comparison between the Listeria monocytogenes Precis™ method and an OECT biosensor

Electrochemical and computational studies of an expired vilazodone Drug as environmentally safe corrosion inhibitor for aluminum in chloride medium

Through using chemical and electrochemical methods, the theoretical and experimental investigation of the expired vilazodone drug's ability to prevent corrosion on aluminium (Al) in a corrosive medium of HCl (1 M) has been examined. Weighing tests (WL), electrochemical (impedance spectroscopy (EIS), potentiodynamic polarization (PDP)), atomic force microscopy (AFM), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) tests at 25 °C have all been used to investigate Vilazodone's capability to prevent corrosion of Al in 1 M HCl in the concentration in the range of 25–150 ppm. The corrosion inhibition effect of the investigate Vilazodone's against Al in acid environment was investigated weight loss and electrochemical methods. The highest % inhibition efficiency (%IE) was 95% resulted from weight loss technique at the highest concentration for inhibitor. According to the PDP data, this examined vilazodone function as a mixed-type inhibitor, impacting both the anodic and cathodic reactions. The inhibitors covered the active points of the metal surface, according to electrochemical impedance spectroscopy (EIS), to prevent corrosion. It was discovered that the inhibitor adsorption on the Al surface obeyed the Langmuir adsorption isothermal model. AFM, SEM, and FTIR surface examinations proved the inhibitor had a significant protective effect against Al dissolution in 1 M HCl. The outcomes from chemical and electrochemical methods are relatively consistent. Vilazodone acted as an effective corrosion inhibitor, according to all of the experimental data.

Influence of Laser Treatment Medium on the Surface Topography Characteristics of Laser Surface-Modified Resorbable Mg3Zn Alloy and Mg3Zn1HA Nanocomposite

In this study, a Mg3Zn alloy and a Mg3Zn1HA nanocomposite were fabricated through disintegrated melt deposition, followed by the hot extrusion process. The specimens were subjected to fiber laser surface modification in air and demineralized water (DM) medium to determine the influence of the laser treatment medium on the microstructure, microhardness, grain size, and surface topography. During the laser treatment, the samples under the water medium produced a lower surface roughness when compared with the air medium. The atomic force microscope (AFM) surface topography scan showed the presence of surface modifications caused by the presence of nanohydroxyapatite (nHA) in the matrix, resulting in a 367.4% and 632.4% increase in the surface roughness (Ra) in the Mg3Zn1HA nanocomposite when compared with the Mg3Zn alloy in water and air media, respectively.