Atomic Force Microscopy Morphology Research Articles

Effects of Acid Etching on the Microstructure and Stiffness of Human Teeth

Abstract The mechanical properties of acid-etched enamel and dentin are important for understanding tooth erosion and developing innovative dental restorative materials. In this study, the microstructure and mechanical properties of both enamel and dentin were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) to quantify the impact of acid etching. SEM images demonstrated that enamel rods have a diameter of approximately 5 μm, while dentinal tubules have a diameter of around 2 μm. After acid etching, the intertubular and peritubular regions were exposed, with the peritubular regions showing a thickness of approximately 1 μm. AFM measurements showed that the stiffness of enamel at the bottom, middle, and top layers is 26.28±4.24 GPa, 32.03±8.68 GPa, and 23.94±3.53 GPa, respectively. For dentin, the stiffness is 16.28±2.76 GPa at the bottom layer and 17.59±5.33 GPa at the middle layer. AFM morphology and stiffness maps illustrated the microstructures of enamel rod and sheaths, as well as dentin tubules in both unetched and acid-etched tooth sections. The stiffness of the acid-etched enamel rod and peritubular dentin decreased by 7-fold and 3.6-fold, respectively, compared to the unetched enamel rod and peritubular dentin.

Multiscale Characterization of Rejuvenated RAP Binders

Abstract Reclaimed asphalt pavement (RAP) is increasingly being utilized in asphalt pavements because of the high cost and scarcity of virgin asphalt materials. However, because RAP is a stiff material, it requires careful engineering to prevent cracking. Recycling agents have shown the ability to partially restore the properties of RAP binders if applied in a proper type and dose. Many studies investigated the impact of recycling agents when added to blends of virgin and RAP binders, but only a few investigated their effectiveness when applied to only RAP binders. The aim of this paper is to investigate the effect of various types and doses of recycling agents on the properties of RAP binders. Rheological properties were measured using a dynamic shear rheometer (DSR). Fourier-transform infrared spectroscopy was utilized to measure the degree of oxidation of the rejuvenated RAP binders. Furthermore, atomic force microscopy (AFM) tests were conducted to measure the morphology and modulus of rejuvenated RAP binders at the nanoscale. Finally, AFM measurements were used to calculate a rejuvenation index (RI), which was developed in an earlier study by the authors to assess the effectiveness of recycling agents in resisting the adverse effects of aging. DSR results demonstrated that the inclusion of recycling agents lowered the stiffness of the RAP binders. AFM morphology images revealed the presence of a large number and varying sizes of phase associations in the RAP binders. These phase associations became more pronounced with aging. Some recycling agents partially reversed the aging effect by reducing the area occupied by these associations. Nonetheless, after long-term aging, the effect of recycling agents diminished. The results of this study revealed that characterizing rejuvenated RAP binders at both the microscale and macroscale levels can indicate the effectiveness of recycling agents and aid in the selection of type or dose of recycling agent.

Additional Enhancement of Surface-Enhanced Raman Scattering Spectra of Myoglobin Precipitated under Action of Laser Irradiation on Self-Assembled Nanostructured Surface of Ag Films

The modifications of the microstructure of myoglobin deposited onto SERS-active Ag-based substrates by drying a drop of aqueous solution with and without laser irradiation and the corresponding surface-enhanced Raman scattering (SERS) spectra are studied. It is shown that drying with laser irradiation leads to the formation of protein aggregates of various types, including crystal-like aggregates. It is also shown that after such drying, the aggregates generally have SERS spectra characterized by a change in the position of the vibration bands and the ratios of their amplitudes compared to the spectra of proteins dried without additional treatment. In particular, parts of the SERS spectra of aggregates formed under laser irradiation are characterized by an additional enhancement (up to 100×) compared to the SERS spectra of myoglobin dried in air at room temperature. The crystallization processes were modeled using the results of atomic force microscopy morphology studies of dried myoglobin on the SERS-active substrates to determine the conditions under which crystal-like aggregates start to grow at surface irregularities, specifically those with a volume close to that of the critical-size nucleus, and where the lowest energy of formation occurs. A correlation is established between surface irregularities, the amplitude, and the change in the SERS spectra during the drying of a myoglobin solution sample on a nanostructured Ag-based surface.

Enhancement of multifunctional optoelectronic and spintronic applications of nanostructured Cr-doped SnO2 thin films by conducting microstructural, optical, and magnetic measurements

A chemical synthesis method was used to produce Cr-doped SnO2 nanoparticles. By using the TEM technique, the nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) nanopowder was confirmed. With different Cr concentrations, the electron beam deposition technique was used to deposit a series of Sn1-xCrxO2 nanocrystalline thin films on a silica substrate. X-ray diffraction (XRD), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and vibrating sample magnetometry (VSM) techniques were used to examine the physical properties of the deposited films. The nanocrystalline nature of the Sn1-xCrxO2 (0.0 ≤ x ≤ 0.1) thin film was confirmed by XRD and AFM morphology measurements. The XRD spectrum of the Sn1-xCrxO2 nanocrystalline film demonstrated a tetragonal crystal structure with no detectable extra phases. The optical measurements showed that as the Cr content increases, the direct optical energy gap Eg decreases without any sign of solubility limit up to x ≤ 0.1. The decrease in Eg is attributed to the sp-d exchange interaction. Also, the spectral behavior of the refractive index dispersion of the Cr-doped SnO2 indicates that as the Cr dopant increases, the refractive index of the deposited film also increases, which is attributed to the increase in the polarizability. Moreover, as the Cr content raises the atomic number, the density of the deposited film increases from 1.43 × 1022 cm−3 for SnO2 to 1.57 × 1022 cm−3 for Sn0·9Cr0·1O2. Further, the behavior of the refractive index dispersion of the deposited film was revealed using a single oscillator model proposed by Wemple-DiDomenico (WDD). Our calculations revealed that as the Cr concentration increases, the value of oscillator energy Eo decreases owing to the decrease in Eg, whereas the value of dispersion energy Ed increases because of the chemical structural changes such as the lattice parameters. Finally, the magnetic studies revealed that incorporating a small fraction of Cr into SnO2 produces room temperature ferromagnetism in the film, which is gradually suppressed by a further increase in Cr doping. These findings indicate that the Cr-doped SnO2 film can be recommended for optoelectronic and spintronic device applications.

Investigation of physiochemical and rheological properties of waste cooking oil/SBS/EVA composite modified petroleum asphalt

ABSTRACTThe objective of this research is to investigate the physiochemical and rheological properties of waste cooking oil (WCO)/styrene‐b‐butadiene‐b‐styrene/ethylene vinyl acetate (SBS/EVA) composite modified asphalt. A petroleum asphalt composite modified with SBS/EVA and oil/SBS/EVA were prepared to undergo the physical, rheological, and microscopic experiments. Comparing these tests results with the properties of unmodified petroleum asphalt, SBS and EVA cause an improvement in pavement performance, but weaken the storage stability. Although the high‐temperature performance undermined by the addition of WCO, the thermal stability, fatigue property, and low temperature crack resistance improved obviously. In addition, WCO mainly composed by low‐weight components, and these can supplement the light components in the polymer‐modified asphalt. EVA could increase the percentage of large molecular size of asphalt, while WCO relieves this trend. The reactions between WCO and these polymers (SBS and EVA) are physical reactions. Atomic force microscopy morphology results reflect that SBS and EVA increase the surface complexity and roughness, and WCO makes the asphalt surface smooth. This indicates WCO increases the dispersion of polymers in asphalt. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48828.

Breaking down and reconstruction of islands during the film growth of CuPc on HOPG

We have observed breaking down and reconstruction of islands in the film growth of a copper phthalocyanine (CuPc) film on highly ordered pyrolytic graphite using photoelectron spectroscopy (PES) and atomic force microscopy (AFM). At the initial deposition of CuPc, the film adopts the Stranski-Krastanov mode and the islands increase normally with the nominate film thickness. At a critical thickness around 6 nm, the islands break down suddenly into small clusters. Further deposition drives the reunion of clusters to form large islands again and makes the film coverage smaller at a nominate thickness of 13 nm. The nonmonotonic PES data and AFM morphology confirmed the re-exposure of the substrate and the first layer CuPc during the island reconstruction process. This nonmonotonic growth behavior may exist widely in many anisotropic molecular film growth processes where the thin film phases are confined or restricted by the symmetry of the substrate and different from their bulk phases.

Resistivity Depends on Preferred Orientation for Transparent Conductive Thin Films

An Al-doped ZnO (AZO) thin film is an important and useful material for optoelectronic devices. In this paper, pure ZnO and AZO thin films were deposited on glass substrates by using pulsed laser deposition (PLD) at different substrate temperatures from room temperature to 650°C. The effect of substrate temperature on the crystallization behavior and optoelectronic properties of the AZO thin films were studied using X-ray diffraction (XRD), atomic force microscopy (AFM), transmittance spectra and resistance measuring system, and so on. The XRD results indicated that all the samples were polycrystalline with a hexagonal wurtzite structure. As the substrate temperature was increased from RT to 650°C, the preferred orientation of the AZO thin films undergone a gradual change that affect the resistivity of the thin film. The AFM morphology also showed the same growth pattern. The average optical transmittance of over 90% in the visible range was obtained at a substrate temperature of 400°C. In addition, with increasing substrate temperature, the optical band gap decreased first and then increased, reaching a minimum at 400°C, which is the same trend as the resistivity. These results indicate that the atoms can easily diffuse from one position to another at the proper substrate temperature. The atoms trapped in non-equilibrium positions can shift to positions closer to equilibrium, which causes the Al atoms to be evenly disperse on the surface of the ZnO thin film to improve the transmittance and the conductivity.

Electrical properties, structural properties, and deep trap spectra of thin α-Ga2O3 films grown by halide vapor phase epitaxy on basal plane sapphire substrates

Undoped epitaxial films of α-Ga2O3 were grown on basal plane sapphire substrates by halide vapor phase epitaxy (HVPE) in three different modes: standard HVPE, HVPE with constant flow of Ga and pulsed supply of O2 (O2-control growth regime), and with constant flow of O2 and pulsed delivery of Ga (Ga-control growth fashion). The best crystalline quality as judged by x-ray symmetric and asymmetric reflection half-widths and by atomic force microscopy morphology profiling was obtained with the O2-control deposition, and these results appear to be the best so far reported for α-Ga2O3 films. All grown α-Ga2O3 epilayers were high-resistivity n-type, with the Fermi level pinned near Ec − 1 eV deep traps. Photoinduced current transient spectra also showed the existence in standard HVPE samples and samples grown under the O2-control pulsed growth conditions of deep hole traps with levels near Ev + 1.4 eV whose density was suppressed in the Ga-control pulsed HVPE samples. The levels of the dominant deep traps in these α-Ga2O3 samples are close to the position of dominant electron and hole traps in well documented β-Ga2O3 crystals and films.

Local-dependency of morphological and optical properties between breast cancer cell lines

Breast cancer is the most malignant type of cancer in women and is a global health problem, with mortality by metastasis being the main factor among others. Currently, detection and diagnosis of breast cancer is achieved through a variety of procedures, such as clinical examination, medical imaging, biopsy, and histopathological analysis. In contrast, spectroscopic analysis has a variety of advantages such as being noninvasive, not destroying biological materials, and not requiring additional histological analysis. In this study, various approaches using Raman spectroscopy, atomic force microscopy (AFM), and optical microscopy were used together to differentiate between and characterize normal breast cell lines (MCF-10A) and breast cancer cell lines (MDA-MB-231, MDA-MB-453). Raman spectra of normal breast cell and breast cancer cell lines confirmed visual differences in the concentrations of various compounds. These spectra were also analyzed using principle component analysis (PCA), and the PCA results showed reliable separation of the three cell lines and the cancer cell lines (MDA-MB-231, MDA-MB-453). With these results, optically synchronizing the AFM morphology, the Raman spectroscopy, and the visible RGB optical transmission intensity provided contrasts for not only conformational differences but also intracellular variation between the normal and cancer cell lines. We observed the inherent characteristic that there is no local difference in cancer cells regardless of morphology in a wide range of optical properties such as absorption, scattering and inelastic scattering.

Towards developing an efficient sensitive element for trinitrotoluene detection: TiO2 thin films functionalized with molecularly imprinted copolymer films

In this study, TiO2 films were successfully grown in-situ onto a FTO substrate by a hydrothermal method, using TiCl4 as Ti precursor, and further on functionalized with a 2,4,6-trinitrotoluene-molecularly imprinted polymer (TNT-MIP) film as a preliminary step in developing a trinitrotoluene (TNT) reusable sensor to overcome the international security issues. For investigating the TiO2 film thickness, crystalline structure and morphology, the films were autoclaved at 200°C at different times. The X-ray diffraction showed that TiO2 films possessed a rutile structure, with no cracks visible by atomic force microscopy (AFM), and the films morphology observed by scanning electron microscopy (SEM) was highly dependent upon the hydrothermal treatment time. Yet, the TiO2 films with a more porous surface were more suitable for TNT-MIP film deposit. Rheology of precursor polymer film solutions, based on poly (acrylonitrile-co-acrylic acid), poly (acrylonitrile-co-methacrylic acid) or poly (acrylonitrile- co-itaconic acid), and the structure and adherence of TNT-MIP films were investigated in order to establish the correct recipe of the MIP. The removal yield of TNT from the imprinted films, the thickness, the porosity and the compatibility with the inorganic TiO2 film were adequate for the poly (acrylonitrile-co-acrylic acid) system with an acrylonitrile: acrylic acid practical ratio of 86.1:13.9 (wt./wt.). Farmore, AFM morphology corroborated with SEM results highlighted the effect of TNT imprinting in the copolymer matrix as the surface of the imprinted layer was quite different from that of the non-imprinted layer.

The effect of perylene diimides chemical structure on the photovoltaic performance of P3HT/perylene diimides solar cells

Core substituted perylene diimides are promising n-type semiconductor materials for organic photovoltaic applications. We have prepared three Donor-Acceptor-Donor perylene diimide molecules, substituted in bay positions with bithiophene, spirobifluorene and bithiophene spirobifluorene groups. These molecules were tested as electron acceptors, in blend with P3HT as donor material, in bulk heterojunction solar cells. The active layers of these devices were optimized by thermal treatment or by the presence of additives and the photovoltaic characteristics were measured. The photovoltaic performances of the three perylene diimides were studied and discussed through absorption and emission spectroscopy characterization, atomic force microscopy morphology study and charge-carrier transport measurements.

The role of Ar flow rates on synthesis of nanostructured zirconium nitride layer growth using plasma enhanced hot filament nitriding (PEHFN) technique

The effects of nonreactive sputter gas (argon) flow rates on the surface properties of zirconium are investigated in argon-nitrogen admixture (60 sccm) using dc plasma enhanced hot filament nitriding (PEHFN) technique. The nitrided specimens are analyzed using X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and nano hardness tester to study their surface properties. Phase analysis (XRD) confirms the development of o-Zr3N4 phase for all exposure conditions. Crystallite size analysis using XRD and AFM morphology confirms the growth of nanostructured zirconium nitride layers. Considerable enhancement in hardness is found when the sample is treated for 40 sccm argon in the admixture Ar:N2 (60 sccm).

Miscibility of Perylene Derivatives with Fatty Acid in Two-Dimensional Binary Mixture

Two component mixtures of a uorescent perylene dye (derivative of 3,4,9,10-perylenetetracarboxylic acid) with arachidic acid in the whole range of mole fraction have been investigated in form of molecular monolayers at the air water interface at di erent pH of the water subphase. Miscibility of the components in the Langmuir monolayers have been examined for pH 3 and pH 13 of the subphase. Using the Langmuir Blodgett technique the monolayers were transferred onto freshly cleaved mica sheets and morphology of the lms was analyzed using atomic force microscopy working in tapping mode. Investigation of the components miscibility in monolayers, determined by mean molecular area and surface pressure analysis reveals di erent behavior of the mixtures depending on pH of the subphase. Atomic force microscopy morphology images of the Langmuir Blodgett lms strongly support conclusion about the components mixing and coverage of the mica surface. It has been found that onto acidic subphases components are only miscible in vestigial form, whereas on alkaline the miscibility is strongly a ected by the dye concentration.

Preparation, structural and optical characterization of nanocrystalline CdS thin film

Nano-structured CdS thin film was deposited onto a glass substrate by an electron beam evaporation technique at room temperature from a powder prepared by a hydrothermal method. The morphology and structural properties of the as-deposited film were characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques. The AFM morphology study confirms that the CdS thin film has nano-sized grains and a dense morphology. The mean particle size that resulted from XRD analyses was 8.4nm. Also, the XRD patterns show that CdS powder and thin film have hexagonal wurtzite type structure with a preferred c-axis orientation along (002) plane. The refractive index and the film thickness were obtained using the Swanepoel method from transmission spectrum. The optical band gap was calculated from the absorption spectrum, and was found to be 2.41eV corresponding to direct optical transition. The dispersion of the refractive index was explained using a single oscillator model. The dielectric relaxation time and the optical conductivity were determined and studied with photon energy.

The correlation of epitaxial graphene properties and morphology of SiC (0001)

The electronic properties of epitaxial graphene (EG) on SiC (0001) depend sensitively on the surface morphology of SiC substrate. Here, 2–3 layers of graphene were grown on on-axis 6H-SiC with different step densities realized through controlling growth temperature and ambient pressure. We show that epitaxial graphene on SiC (0001) with low step density and straight step edge possesses fewer point defects laying mostly on step edges and higher carrier mobility. A relationship between step density and EG mobility is established. The linear scan of Raman spectra combined with the atomic force microscopy morphology images revealed that the Raman fingerprint peaks are nearly the same on terraces, but shift significantly while cross step edges, suggesting the graphene is not homogeneous in strain and carrier concentration over terraces and step edges of substrates. Thus, control morphology of epitaxial graphene on SiC (0001) is a simple and effective method to pursue optimal route for high quality graphene and will be helpful to prepare wafer sized graphene for device applications.

Discharge properties and AFM imaging experiments of cantilever probe integrated with microplasma reactor

A new conception of cantilever array-based microplasma nanoetching and atomic force microscopy (AFM) morphology inspection in the same system is proposed in this Letter. A cantilever probe integrated with microplasma reactor and SiO 2 cantilever array with hollow pyramid tip are successfully fabricated. The experiment results show that the microplasma reactor can discharge stably in CHF 3 /Ar mixtures, and V - I characteristics of the microdischarges are in hollow cathode discharge mode. AFM imaging experiments using the cantilever probe with the microplasma reactor is performed and sample surface morphology with nano-scaled resolution is inspected. The results of this Letter may lay a foundation for the future work of plasma parallel nanofabrication and AFM morphology inspection in the same system.

Surface hydrophobicity modification of cellulose fibers by layer-by-layer self-assembly of lignosulfonates

Self-assembled multilayers of lignosulfonates (LS) were built up on both quartz slides and cellulose fibers using a Cu2+-mediated layer-by-layer (LBL) technique. The growth of LS multilayers on quartz slides was monitored by UV-Vis spectroscopy, and the absorbance at 205 nm as well as at 280 nm was found to linearly increase with the number of layers. The formation of LS multilayers on fibers surfaces was characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The XPS results showed that the surface contents of the characteristic elements, S and Cu, of LS multilayers were increased with the number of layers, which suggests the deposition of LS-Cu2+ complexes on cellulose fibers. Furthermore, there was a good linear relationship between the calculated surface LS content and the increment of LS layers. The AFM morphology results confirmed that the cellulose microfibrils on fiber surface were gradually covered by LS particles, resulting in the increase of surface roughness as self-assembly proceeded. The hydrophobicity of cellulose fiber probed by dynamic contact angle was significantly increased due to LBL self-assembly of LS on its surface. The initial contact angle was increased from 0° to 115° as the cellulose fibers were modified with a 5-layer LS multilayer. The reduction rate of the contact angle was dependent on the number of layers. When the cellulose fiber was modified by a 5-layer LS multilayer, the contact angle shifted from 115 to 98° after 0.12 s, suggesting some degree of hydrophobic character. Therefore, this technique provides a simple but effective way for promoting hydrophobicity of cellulose fibers in a controllable manner.

Impact of AFM-induced nano-pits in a-Si:H films on silicon crystal growth

Conductive tips in atomic force microscopy (AFM) can be used to localize field-enhanced metal-induced solid-phase crystallization (FE-MISPC) of amorphous silicon (a-Si:H) at room temperature down to nanoscale dimensions. In this article, the authors show that such local modifications can be used to selectively induce further localized growth of silicon nanocrystals. First, a-Si:H films by plasma-enhanced chemical vapor deposition on nickel/glass substrates are prepared. After the FE-MISPC process, yielding both conductive and non-conductive nano-pits in the films, the second silicon layer at the boundary condition of amorphous and microcrystalline growth is deposited. Comparing AFM morphology and current-sensing AFM data on the first and second layers, it is observed that the second deposition changes the morphology and increases the local conductivity of FE-MISPC-induced pits by up to an order of magnitude irrespective of their prior conductivity. This is attributed to the silicon nanocrystals (<100 nm) that tend to nucleate and grow inside the pits. This is also supported by micro-Raman spectroscopy.

Preliminary study on the morphology of rabies virus by atomic force microscopy

Objective To explore the application of atomic force microscopy（ AFM ） on the research of morphology of the rabies viruses. Methods To prepare the rabies virus CTN-1v strains by ultracentrifugation, and observe it with transmission electron microscopy （TEM） which negatively stained by phosphotungstic acid. Then study the morphology of rabies virus with AFM based on the result of TEM. AFM image applies the tapping mode to rabies virus without any further treatment in air at room temperature. Results The TEM image is two-dimensional image which can be seen the classical bullet-shaped structure,and the spike structure can also be seen. The AFM image showed the rabies virus morphology with three-dimensional image which can shows the characteristics of the virus surface and edge. The rabies virus particle was successfully observed by TEM or AFM methods. Conclusion It＇s the first time to get the three-dimensional morphological structure of rabies virus by atomic force microscopy, compared with transmission electron microscopy, AFM is a new research tool for viral morphology study with the advantages of simple sample preparing and intuitionistic and visible interface for researchers. Key words: Rabies virus Morphology Atomic force microscopy

Impact of Top (Pt, Au, and Al) Electrodes on HfAlOx-Based MIM Capacitors

The electrical and dielectric properties of films deposited by radio frequency magnetron cosputtering of and targets with Au as the bottom electrode and Pt, Au, and Al as the top electrodes forming metal–insulator–metal (MIM) structures have been studied. layers are characterized by X-ray photoelectron spectroscopy to examine the chemical composition. Atomic force microscopy morphology study shows that root mean square value of surface roughness of the film decreases after annealing. From grazing incidence X-ray diffraction study, it is observed that the deposited films remain amorphous up to annealing temperature. For electrical characterization, current–voltage and capacitance–voltage characteristics were studied in the frequency range of . MIM capacitors with Pt top electrode were found to have the lowest leakage current of (at ) and low energy dissipation with improved voltage coefficients of capacitance values . Low field conduction mechanism was found to be dominated by Schottky emission, while at high field () it is dominated by Poole–Frenkel mechanism. Change in the quadratic voltage coefficient of capacitance under different stress voltages was found to be the lowest with Pt top electrode.