Scanning Atomic Force Microscopy Research Articles

Effect of thermal annealing on structure and magnetic properties in a Ni–Cr multilayer

Abstract Evolution of structural and magnetic properties in a nickel/chromium (Ni/Cr) multilayer, as a function of different annealing temperatures was investigated. The Ni/Cr multilayer of nominal structure [Cr (50 Å)/Ni (50 Å)]×10/Cr (30 Å) was grown on a Si substrate by radio frequency ion beam sputtering at room temperature. X-ray diffraction, X-ray reflectometry, atomic force microscopy and crossectional scanning electron microscopy were employed for the complete structural characterization of the multilayer whereas superconducting quantum interference device vibration sample magnetometer was used for the bulk magnetisation study. The effect of in-situ and ex-situ annealing on overall structural property of the multilayer also reported in present work. From in-situ X-ray reflectometry (50–400 °C), 300 °C was detected as the optimum temperature for improved structural properties of the Ni/Cr multilayer. Initiation of alloying in the multilayer sample was noticed at 350 °C. The multilayer found to exhibit polycrystalline nature observed by X-ray diffraction. Total thickness of the multilayer system was confirmed by crossectional scanning electron microscopy and in well agreement with X-ray reflectivity results. The Ni/Cr sample found to exhibit soft ferromagnetic behaviour after annealing at 300 °C and 400 °C. However the net magnetic moment reduced upon annealing at higher temperature (400 °C).

Antibacterial Properties of Ethacridine Lactate and Sulfmethoxazole Loaded Functionalized Graphene Oxide Nanocomposites.

The emergence of drug-resistant bacterial strains that reduce the effectiveness of antimicrobial agents has become a major ongoing health concern in recent years. It is therefore necessary to find new antibacterials with broad-spectrum activity against both Gram-positive and Gram-negative bacteria, and/or to use nanotechnology to boost the potency of already available medications. In this research, we examined the antibacterial efficacy of sulfamethoxazole and ethacridine lactate loaded two-dimensional glucosamine functionalized graphene-based nanocarriers against a range of bacterial isolates. Graphene oxide was first functionalized with glucosamine, which as a carbohydrate moiety can render hydrophilic and biocompatible characters to the GO surface, and subsequently loaded with ethacridine lactate and sulfamethoxazole. The resulting nanoformulations had distinct, controllable physiochemical properties. By analyzing the formulation using Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (PXRD), a thermogravimetric analysis (TGA), zetasizer, and a morphological analysis using Scanning Electron Microscopy and Atomic Force Microscopy, researchers were able to confirm the synthesis of nanocarriers. Both nanoformulations were tested against Gram-negative bacteria, including Escherichia coli K1, Serratia marcescens, Pseudomonas aeruginosa, Salmonella enterica, as well as Gram-positive bacteria, including Bacillus cereus, Streptococcus pyogenes, and Streptococcus pneumoniae. Importantly, ethacridine lactate and its nanoformulations exhibited significant antibacterial properties against all bacteria tested in this study. When tested for minimum inhibitory concentration (MIC), the results were remarkable and revealed that ethacridine lactate presented MIC90 at 9.7 µg/mL against S. enteric, and MIC90 at 6.2 µg/mL against B. cereus. Notably, ethacridine lactate and its nanoformulations showed limited toxicity effects against human cells using lactate dehydrogenase assays. Overall, the results revealed that ethacridine lactate and its nanoformulations possess antibacterial activities against various Gram-negative and Gram-positive bacteria and that nanotechnology can be employed for the targeted delivery of effective drugs without harming the host tissue.

Calibrate the non-orthogonal error of AFM with two-dimensional self-traceable grating

The calibration of the non-orthogonal error in nanoscale measurements is of paramount importance for analytical measuring instruments. Particularly, the calibration of non-orthogonal errors in atomic force microscopy (AFM) is essential for the traceable measurements of novel materials and two-dimensional (2D) crystals. The 2D self-traceable grating with a theoretical non-orthogonal angle of less than 0.0027° and an expanded uncertainty of 0.003° (k = 2) are measured by the Metrological Large Range Scanning Probe Microscope (Met. LR-SPM). In this study, we characterized the local and overall non-orthogonal error in AFM scans and proposed a protocol to tune the optimal scanning parameters of AFM minimizing the non-orthogonal error. We presented the method for accurately calibrating a commercial AFM system for non-orthogonal by establishing a detailed uncertainty budget and errors analysis. Our results verified the important advantages of the 2D self-traceable grating in calibrating precision instruments.

Heat Treatment and Dynamic Mechanical Analysis Strain Sweep Effects on the Phase Structure and Morphology of an Fe-28Mn-6Si-5Cr Shape Memory Alloy

Fe-Mn-Si-based shape memory alloys (SMAs) have been extensively investigated since 1982 for various useful properties that enhance the development of different applications such as anti-seismic dampers for very tall buildings, pipe joints, or rail fasteners. In particular, the Fe-28Mn-6Si-5Cr (mass. %) alloy has been mainly used in vibration mitigation or self-adjustable axial displacement applications. Dynamic mechanical analysis (DMA), performed by strain sweeps (SS), enables the monitoring of the evolution of storage modulus and internal friction variations with increasing strain amplitudes at different constant frequencies and temperatures. Thus, applying dynamic bending with various frequencies and amplitudes that actually represents an isothermal mechanical treatment. In the present paper, an Fe-28Mn-6 Si-5Cr (mass. %) SMA was cast by ingot metallurgy, hot-rolled, and water quenched in order to obtain thermally induced martensite and avoid the occurrence of cooling cracks. The influence of the holding time, between 2 and 10 h, at 1050 °C and the effects of DMA-SS performed at three different frequencies were analyzed by a differential scanning calorimetry, an X-ray diffraction, and a scanning electron and atomic force microscopy. The effects of the holding time and mechanical treatment on the structure and morphology of martensite plates were corroborated with the results of the thermal analysis.

Relationship Between Structural and Optical Properties in Vanadium Pentoxide

Spray pyrolysis technique (SPT) and radio-frequency magnetron sputtering (RF-MS) were used to obtain vanadium oxide (VxOy) layers. The surface morphology was visualized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Further, t

Effect of Heat Treatment on Zirconium Oxide High‐k Gate Dielectric in Silicon‐Based Metal Oxide Semiconductor Capacitors

Herein, zirconia thin films are successfully prepared on silicon substrates using the sol–gel method, and the microstructure, optical, and electrical properties of zirconia high‐k gate dielectric films are analyzed at different annealing temperatures. X‐ray diffraction results show that ZrO2 films crystallize above 500 °C and the grain size increases with the increase of annealing temperature; X‐ray photoelectron spectroscopy analysis confirms that metal–oxygen bonds can be effectively formed and defects in the films are eliminated by annealing treatment, with significant changes in the valence band shift (ΔEv) and conduction band shift (ΔEc) with increasing annealing temperature. Analysis of the optical properties of the films by UV‐Vis confirms that all zirconia films have high transmittance, with the bandgap increasing from 5.54 to 5.74 eV with increasing annealing temperature. Atomic force microscope and field emission scanning electron microscope show that the film quality is better and the root mean square roughness of the zirconia films increases from 0.551 to 1.190 nm and the film thickness decreases from 176.19 to 58.73 nm with increasing annealing temperature. Electrical performance tests show that proper annealing is effective in improving electrical properties, such as obtaining a larger dielectric constant (k) and a lower leakage current density.

Decomposition of Fingerprints on Porous TiO2 Thin Films

This study investigated the effect of the mixing ratio of TiO2 nanoparticles (P25) and titanium alkoxide (T-sol) on various properties of TiO2 films. The specific surface area of the TiO2 film was determined using BET analysis, while the microstructure and thickness were analyzed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), respectively. Transmittance and pencil hardness tests were conducted to evaluate the transparency and durability of the coating layer, respectively. The results showed that, as the P25 content increased, the specific surface area of the TiO2 film also increased, but this effect decreased as the ratio of T-sol to P25 increased. Additionally, the thickness and surface roughness (Ra) of the coating layer increased as the P25 content increased, with the thickness increasing from 210 to 950 nm and Ra increasing from 51 to 88 nm. However, the transmittance of the coating layer decreased as the P25 content increased, indicating that the films became less transparent. Furthermore, the pencil hardness of the coating layer decreased as the P25 content increased, indicating that the films became less durable. Finally, the oil contact angle decreased as the P25 content increased, indicating that the films became more hydrophilic.

Divulging the Potential of Sodium Carbide Thin Film for Semiconductor Applications

The work reported in this article is an attempt to introduce the least explored sodium carbide as a thin film and to explore its semiconducting behavior. The sodium carbide thin film deposited by the radio frequency sputtering technique is subjected to morphology, structure, and spectroscopic characterizations. The floral petal‐like morphology, understood from the field‐emission scanning electron microscopy and atomic force microscopy images, helps in enhancing interaction with the radiation that is revealed through the UV–visible absorption spectrum. X‐ray diffraction, photoelectron and Raman spectroscopic analyses confirm that the film is sodium carbide. The optical emission behavior of the sodium carbide thin film in the blue region is unveiled through the photoluminescence spectrum, power spectrum, color purity, and chromaticity diagram. Employing the refractive index and extinction coefficient values from the specular reflectance data, optical and electrical conductivities, nonlinear refractive index, linear and nonlinear optical susceptibility, dissipation factor, and surface and volume energy loss functions and their wavelength dependence due to interfacial polarization are investigated. The transfer matrix method is used to understand the spatial variation of the induced electric field and optical current density.

Low energy Ag ion irradiation-induced surface modification studies of Au-graphene oxide nanocomposite thin films

The surface modifications of graphene oxide (GO) based thin films have attracted considerable attention owing to the tuning of properties leading to several applications. Being a clean and impurity-free method, ion irradiation may prove superior to conventional methods in modifying the properties; however, the damage induced by the beam needs to be investigated. The present work investigates the surface modifications in the Au-graphene oxide thin films by 220 keV Ag ion irradiation at different ion fluence 3 × 1014, 1 × 1015, 3 × 1015, and 1 × 1016 ions/cm2. The Raman and X-ray Spectroscopy (XPS) show the transformation of GO matrix of Au-GO thin films into amorphous carbon at higher fluence, whereas the scanning electron microscopy and atomic force microscopy, show segregation of the Au thin layer into island type structures over the GO layer at high fluence; this is caused by the local heating produced due to ion irradiation. The XPS and X-ray diffraction results confirm the redistribution of the thin Au layer with Ag ion irradiation. The UV- visible spectroscopy show a slight blue shift in the surface plasmon peak of Au caused by the amorphization of GO matrix due to the beam irradiation. These thin ion beam-modified nanocomposites thin films may find various applications in surface-enhanced spectroscopy, optical filters, plasmonic devices, etc.

SUSTAINABLE SYNTHESIS AND CHARACTERIZATION OF TUNABLE AND MULTIPURPOSE NANOCELLULOSE FROM FRESHWATER AQUATIC WEED AS PHARMACEUTICAL EXCIPIENT

Objective: The main objective of this work was to understand the basic properties of crystalline nanocellulose (CNC) that can be useful as a novel excipient in pharmaceutical formulations. This covers the isolation and preparation of nanocellulose followed by characterization. Methods: Cellulose was isolated from aquatic weed by autoclaving and bleaching. Cellulose to CNC conversion involved gluconic acid treatments at different concentrations (40%, 50% and 60%) followed by centrifugation and neutralization. CNC was further characterized by Differential Scanning Calorimetry (DSC) and Thermo gravimetric Analysis (TGA), Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM) for surface morphology, elemental analysis by Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), crystallinity index by X-Ray Diffraction (XRD), and optical microscopy. Results: Acid concentration affects the moisture uptake, particle size, and yield of CNC. CNC size ranged from 350 nm to 900 nm with a crystallinity index 80% to 85%. Moisture uptake was 6.38±0.12% at 33% relative humidity. DSC and TGA established thermal stability over 200 °C. Nanocellulose has shown Angle of repose (28.81°), Carrs index (12.32), zeta potential (33mV) values and heavy metals within pharmacopoeial limits. Conclusion: CNC from water hyacinth was prepared successfully by sustainable process. CNC physico-chemical characterization revealed the stable nature of CNC, suitable to be used as an excipient in pharmaceutical formulations.

Aerogels based on cationically modified chitosan and poly(vinyl alcohol) for efficient capturing of viruses

In this study, we developed a new filtering bioaerogel based on linear polyvinyl alcohol (PVA) and the cationic derivative of chitosan (N-[(2-hydroxy-3-trimethylamine) propyl] chitosan chloride, HTCC) with a potential antiviral application. A strong intermolecular network architecture was formed thanks to the introduction of linear PVA chains, which can efficiently interpenetrate the glutaraldehyde(GA)-crosslinked HTCC chains. The morphology of the obtained structures was examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The aerogels and modified polymers' elemental composition (including the chemical environment) was determined using X-ray photoelectron spectroscopy (XPS). New aerogels with more than twice as much developed micro- and mesopore space and BET-specific surface area were obtained concerning the starting sample chitosan aerogel crosslinked by glutaraldehyde (Chit/GA). The results obtained from the XPS analysis showed the presence of cationic 3-trimethylammonium groups on the surface of the aerogel, which can interact with viral capsid proteins. No cytotoxic effect of HTCC/GA/PVA aerogel was also observed on fibroblast cells of the NIH3T3 line. Furthermore, the HTCC/GA/PVA aerogel has been shown that efficiently traps mouse hepatitis virus (MHV) from suspension. The presented concept of aerogel filters for virus capture based on modified chitosan and polyvinyl alcohol has a high application potential.

A New Method of AFM‐Based Nanolithography Using Frequency Enhanced Electrochemical Pressure Solution Etching

AbstractA new method of direct‐write nanolithography that is able to rapidly etch silica surfaces under a scanning atomic force microscopy (AFM) probe in tapping mode (TM) is reported. In this lithography technique, silica surfaces are etched using a recently described electro‐chemo‐mechanical phenomenon of frequency enhanced electrochemical pressure solution (FEEPS). In FEEPS, the tapping of the AFM tip generates oscillations of the Stern potential at the silica‐water interface that can accelerate the silica dissolution kinetics by more than 5–6 orders of magnitude when surface resonance states are achieved; i.e., when the oscillation frequency is in phase with the dynamics of interfacial chemical reaction steps. By scanning silica surfaces in TM, silica is selectively dissolved below the tapping tip as it is scanned. The FEEPS accelerated silica dissolution rates can generate etched features with depths of more than 60 nm in a single AFM tip pass. The rate of etching can be controlled easily by varying the scanning rate or by modulating the tapping frequency. This fine control over the silica etching process and because material is removed (dissolved) rather than displaced as with nanoscratching, the FEEPS process lends itself to gray‐scale nanolithography which is demonstrated.

Dynamic Wetting Properties of Silica-Poly (Acrylic Acid) Superhydrophilic Coatings.

Superhydrophilic coatings based on a hydrophilic silica nanoparticle suspension and Poly (acrylic acid) (PAA) were prepared by dip coating. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to examine the morphology of the coating. The effect of surface morphology on the dynamic wetting behavior of the superhydrophilic coatings was studied by changing the silica suspension concentration from 0.5% wt. to 3.2% wt. while keeping the silica concentration in the dry coating constant. The droplet base diameter and dynamic contact angle with respect to time were measured using a high-speed camera. A power law was found to describe the relationship between the droplet diameter and time. A significantly low experimental power law index was obtained for all the coatings. Both roughness and volume loss during spreading were suggested to be responsible for the low index values. The water adsorption of the coatings was found to be the reason for the volume loss during spreading. The coatings exhibited good adherence to the substrates and retention of hydrophilic properties under mild abrasion.

The Antibacterial Activity of the Biosynthesized Copper Oxide Nanoparticles by Lantana camara Flowers Extract Against Some Bacterial Isolated from Burns

The study included 70 Surface swabs collected from patients in different ages of both genders suffering from burns infections. All the specimens were diagnosed by subculturing in differential and selective media, microscopically and by following the biochemical tests to confirm identifications. Antibiotic susceptibility test was done to all the bacterial isolates.The identification of the clinical isolates showed that the 16(22.9%) were belonged to Staphylococcus aureus and 6(8.6%) of Staphylococcus epidermidis , whereas 23(32.8%),20(28.6%) isolates were for Pseudomonas aeruginosa ,Acinetobacter baumannii respectively. Copper oxide nanoparticles were biosynthesized by Lantana camara flower extracts which acted as a reducing agent for copper nitrate salts, characterization of the metal oxide was done by using Ultra violate visible light Spectroscopy, Fourier transforms Infrared spectroscopy, X-ray Diffraction, Atomic Force Microscopy and Field Emission Scanning Electron Microscopy. The biological activity of Copper Oxide Nanoparticles was screened toward three clinical isolates that showed multiple drug resistance isolated from burns by following agar wells diffusion method which proved the ability of copper oxide nanoparticles to inhibit growth of the clinical bacterial isolates. The minimum inhibitory concentrations were determined toward the tested bacteria by using the microdilution method.

Preparation and characterization of lithium trivanadate thin films by spray pyrolysis method for supercapacitor applications

The lithium trivanadate (LiV3O8) thin films were deposited over stainless steel (SS) substrates by spray pyrolysis method. The material deposited at an optimized substrate temperature of 350°C and at an annealing temperature of 500°C (LV350_500/SS) performed better in electrochemical properties. The structural and surface morphological characteristics of the as deposited materials were determined using the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. The stable V5+ state was observed for the as-prepared LiV3O8 thin film in the X-ray photoelectron (XPS) spectrum. The electrochemical performance of the thin films were characterized using a three-electrode configuration with Ag/AgCl as the reference electrode, thin film material as the working electrode, and the platinum wire as the counter electrode. The 1 M LiNO3 aqueous solution was taken to be the electrolyte. LV350_500/SS made using a Li/V molar concentration of 0.1: 0.3 displayed an initial specific discharge capacitance value of 695 Fg−1 at a current density of 0.25 Ag−1, in the voltage range of -0.4 V to 0.4 V. But, the LV350_500/SS prepared using Li/V molar concentration of (0.05: 0.15) showed a low specific capacitance value of 181 Fg−1. A symmetric supercapacitor device made with the LV350_500/SS thin film as the electrodes and poly(vinylidene fluoride-co-hexafluoropropylene)/2D Graphene Oxide (PVdF-HFP/GO) composite polymer membrane as the electrolyte showed an excellent specific discharge capacitance value of 31 Fg−1 for a current density of 0.25 Ag−1. The calculated specific energy density and specific power density values were found to be 69 Whkg−1 and 1002 Wkg−1 respectively, for the above symmetric device.

Parasitic masking effect in GaN SA-MOVPE using SiO2 masks deposited by the PECVD technique

The paper reports a phenomenon of parasitic substrate masking during selective area metalorganic vapor phase epitaxy (SA-MOVPE) of gallium nitride (GaN) using silicon dioxide (SiO2) masks deposited by plasma enhanced chemical vapor deposition (PECVD) at pressures above 150 hPa. The discussion of the thermal stability and nitridation process of the SiO2 films is followed by the presentation of the experimental work results focused on the investigation of the relationship between the parasitic masking effect and pressure in the MOVPE reactor chamber. Analysis of the surface morphology is conducted using scanning electron microscopy (SEM) and atomic force microscopy (AFM). A hypothesis was proposed explaining the formation of the deposition-free region that indicates silanimine (HNSi) layer formation as a possible factor responsible for the adverse inhibition of GaN nucleation.

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.

Impact of Sample Preparation Methods on Single-Cell X-ray Microscopy and Light Elemental Analysis Evaluated by Combined Low Energy X-ray Fluorescence, STXM and AFM.

Although X-ray fluorescence microscopy is becoming a widely used technique for single-cell analysis, sample preparation for this microscopy remains one of the main challenges in obtaining optimal conditions for the measurements in the X-ray regime. The information available to researchers on sample treatment is inadequate and unclear, sometimes leading to wasted time and jeopardizing the experiment's success. Many cell fixation methods have been described, but none of them have been systematically tested and declared the most suitable for synchrotron X-ray microscopy. The HEC-1-A endometrial cells, human spermatozoa, and human embryonic kidney (HEK-293) cells were fixed with organic solvents and cross-linking methods: 70% ethanol, 3.7%, and 2% paraformaldehyde; in addition, HEK-293 cells were subjected to methanol/ C3H6O treatment and cryofixation. Fixation methods were compared by coupling low-energy X-ray fluorescence with scanning transmission X-ray microscopy and atomic force microscopy. Organic solvents lead to greater dehydration of cells, which has the most significant effect on the distribution and depletion of diffusion elements. Paraformaldehyde provides robust and reproducible data. Finally, the cryofixed cells provide the best morphology and element content results. Although cryofixation seems to be the most appropriate method as it allows for keeping cells closer to physiological conditions, it has some technical limitations. Paraformaldehyde, when used at the average concentration of 3.7%, is also an excellent alternative for X-ray microscopy.

Envision and Appraisal of Biomolecules and Their Interactions through Scanning Probe Microscopy

Scanning probe microscopy (SPM) has gifted a novel eye to envision nanotechnology and nanoscience. The SPM technique involves a sharp probe that moves over the sample surface and leads to produce signals, which facilitates a deep understanding of the structural, electronic, vibrational, optical, magnetic, (bio) chemical, and mechanical properties of the material. Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) measure various kinds of physical properties such as electric current, force, and capacitance. Moreover, AFM shows a prominent feature over STM that it accepts insulating surfaces and can work under physiological conditions, making it feasible to study biological molecules. Herein, the SPM approach toward biomolecule imaging and appraising different physiological processes with molecular resolution is highlighted. The review raises awareness regarding current obstacles in biological sample preparation and possible ways to conquer these difficulties. Subsequently, the recent applications of STM and AFM on various biomolecules with representative examples like DNA, protein, and carbohydrates are discussed. The conductance measurement studies of the biological samples emphasize applications like drug delivery, biosensors, molecular electronics, and spintronics fields. This is followed by an outlook of future perspectives making a pavement toward the basic science and applied field of biomolecules using SPM technology.

Anticancer Activity of Synthesized ZnO and ZnO/AgCl Nanocomposites against Five Human Cancer Cells

In this work, a refluxing method is used to prepare nanoparticles of zinc oxide (ZnO NPS) and zinc oxide /silver chloride nanocomposites (ZnO/AgCl NCS). The structural properties of nanocrystals are studied by Atomic Force Microscope (AFM), X-Ray Diffraction (XRD), and Field Emission Scanning Electron Microscopy (FE-SEM) to determine the average crystal size, morphology, particle size and average grain size of nanocrystals. The results of anticancer efficiency of ZnO NPs and ZnO/AgCl NCs show cytotoxic activity against five human cancer cells, namely hepatocellular carcinoma, rhabdomyosarcoma (RD), colorectal carcinoma (HCT116), mammary gland (MCF-7), and epidermoid carcinoma (Hep2) compared against doxorubicin. The anticancer mechanism of pure and nanocomposites ZnO are suggested according to the release of Zn+2 and the production of reactive oxidation species (ROS) and the effect of these species on cancer inhibition.