Atomic Force Microscopy Characterization Research Articles

Crosslinking induces high mineralization of apatite minerals on collagen fibers

Type I collagen, as the critical organic component of bone matrix, plays a template role in mineralization. Gamma-ray irradiation is used to prepare collagen with different crosslinking degrees without introducing foreign substances for mineralization. Significant improvement in crosslinking degree of collagen can be inferred by enzymolysis and differential scanning calorimetry analysis. Scanning electron microscopy observation reveals that, as crosslinking degree increases, the pore structure of collagen becomes more compact. Fourier transform infrared spectroscopy analysis shows the intact retention of classical triple-helical structure of collagen after crosslinking and the following mineralization. Atomic force microscopy characterization, calcium and phosphorus assay kit tests and thermogravimetry measurements indicate that the more compact the collagen structure, the more hydroxyapatite can attach on collagen fibers. These findings reveal the high crosslinking degree of collagen is favorable for the improvement of mineralization ability by providing a more stable and compact network structure. Such crosslinked collagen may provide a more potential way for the preparation of bone substitute materials.

Development of a Perchlorate Chemical Sensor Based on Magnetic Nanoparticles and Silicon Nitride Capacitive Transducer

AbstractWe report in this work the development of a novel capacitance electrochemical sensors based on silicon nitride substrate (Si3N4) chemically modified with a structure of Cobalt phthalocyanine, C,C,C,C‐tetracarboxylic acid‐Polyacrylamide (Co(II)Pc‐PAA). This sensitive layer was tested with and without magnetic nanoparticles (MNP) for perchlorate ( ) detection. The developed chemical sensor with Si3N4/APTES‐MNP/Co(II)Pc‐PAA structure has shown a better performance when compared to the other structure based on Si3N4/Co(II)Pc‐PAA. Contact angle measurements (CAM) and atomic force microscopy (AFM) characterizations have been performed to characterize the functionalization of the chemical sensors surface. Under the optimized structure of the chemical sensor, electrochemical measurements were carried out using Mott‐Schottky analysis for detection within the large range of 10−10 to 10−4 M with a very low detection limit of 2×10−10 M. The chemical sensor has demonstrated a high selectivity toward when compared to other interfering anions such as Cl−, SO42−, and CO32−. The present capacitive chemical sensor is very promising for sensitive and rapid detection of for environmental applications.

Microwave-Assisted Regeneration of Single-Walled Carbon Nanotubes from Carbon Fragments.

Direct growth of chirality-controlled single-walled carbon nanotubes (SWNTs) with metal catalyst free strategy, like cloning or epitaxial growth, has suffered from the low efficiency. The underlying problem is the activation of seed edge. Here an unexpectedly efficient microwave-assisted pathway to regenerate SWNTs from carbon fragments on SiO2 /Si substrate is demonstrated via Raman spectroscopy and atomic force microscope (AFM) characterization. In this attempt, microwave irradiation provides fast heating to remove polar groups bonded to carbon nanotubes and reduce the spontaneous closure of tubes' open ends. The survived SWNT and carbon fragments connected to it after plasma treatment are simply microwaved and then they serve as the template for regeneration. Scanning electron microscope and AFM characterizations indicate that the efficiency of the regeneration can reach 100%. And the regenerated SWNT has been proved without any change in chirality compared to the original SWNT. Electrical measurements on regenerated carbon nanotube films indicate 1 and 2 times increase in on/off ratio and on-state current respectively than original carbon nanotube films obtained from solution-phase separation, confirming the improvement of SWNT's quality. The microwave-assisted regeneration is found to be highly effective and would be applied to improve the cloning efficiency of carbon nanotubes potentially.

Controlling of green nanocellulose fiber properties produced by chemo-mechanical treatment process via SEM, TEM, AFM and image analyzer characterization

Nanocellulose fibers were extracted from Oil Palm Empty Fruit Bunch (OPEFB) fibers by a chemo-mechanical treatment process. The aim of this study is to observe and investigate the morphological structure and fiber dimension characteristic of each stage in the nanocellulose production. The fiber structure characterization of the raw, purified pulps, extracted cellulose and nanocellulose fibers were controlled by observation and investigation under Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM) and Image Analyzer. The morphological observation illustrated that the isolation of nanocellulose fibers had greatly decreased from micron to nanoscale, up to 5-10 nm in diameter, and therefore suitable to be used as quality nano-reinforcement in the polymer matrix for a potential environmental green nanobiocomposites development.

Atomic force microscopy characterisation of alkali-silica reaction products to reveal their nanostructure and formation mechanism

Microscopic studies on alkali-silica reaction (ASR) products revealed two distinct forms of solid ASR products. However, their chemical and morphological aspects have not been adequately understood. This study provides a new insight into the nanostructure of ASR products as examined by atomic force microscopy (AFM). Results reveals that the surface microscale morphology of the rosette-like ASR product is associated with the loss of surface water, and the granular ASR product is formed by the accumulation of nanoscale particles with a typical size of around thirty nanometers. Moreover, the application of AFM provides evidence for the fluid nature of the granular ASR product at high moisture content.

Single-Step Binary Electrostatic Directed Assembly of Active Nanogels for Smart Concentration-Dependent Encryption.

Anionic and cationic (N-isopropylacrylamide derivatives) active colloidal hydrogel nanoparticles, i.e., nanogels, are electrostatically assembled on surfaces to form microscale patterns with complex geometries. While using mixed dispersions of these two kinds of nanogels, we demonstrate the capability of sorting the nanogels in one step to form binary nanogel patterns on a surface. These patterns appear independently or simultaneously depending on the relative proportion of each nanogel type in the mixture. Hence, the resulting nanogel patterns provide quantitative information regarding the dispersion composition and can be used to achieve smart concentration-dependent nanogel encryption. Moreover, atomic force microscopy characterization measurements performed in liquid prove that the assembled nanogels maintain their swelling/deswelling properties once attached to the surface. Consequently, this method paves the way for applying such active nanogel patterns to produce smart coatings and sensors.

Amyloid Beta Peptide VHHQ, KLVFF, and IIGLMVGGVV Domains Involved in Fibrilization: AFM and Electrochemical Characterization.

The time-dependent structural modifications and oxidation behavior of specifically chosen five short amyloid beta (Aβ) peptides, Aβ1-16, Aβ1-28, Aβ10-20, Aβ12-28, and Aβ17-42, fragments of the complete human Aβ1-40 peptide, were investigated by atomic force microscopy (AFM) and voltammetry. The objective was to determine the influence of different Aβ domains (VHHQ that contains electroactive histidine H residues, KLVFF that is the peptide hydrophobic aggregation core, and IIGLMVGGVV that is the C-terminus hydrophobic region), and of Aβ peptide hydrophobicity, in the fibrilization mechanism. The short Aβ peptides absence of aggregation or the time-dependent aggregation mechanisms, at room temperature, in free chloride media, within the time window from 0 to 48 h, were established by AFM via changes in their adsorption morphology, and by differential pulse voltammetry, via modifications of the amino acid residues oxidation peak currents. The first oxidation peak was of tyrosine Y residue and the second peak was of histidine H and methionine M residues oxidation. A correlation between the presence of an intact highly hydrophobic KLVFF aggregation core and the time-dependent changes on the Aβ peptides aggregation was found. The hydrophobic C-terminal domain IIGLMVGGVV, present in the Aβ1-40 peptide, also contributed to accelerate the formation of Aβ1-40 peptide aggregates and fibrils.

Electrochemical and AFM Characterization of G-Quadruplex Electrochemical Biosensors and Applications.

Guanine-rich DNA sequences are able to form G-quadruplexes, being involved in important biological processes and representing smart self-assembling nanomaterials that are increasingly used in DNA nanotechnology and biosensor technology. G-quadruplex electrochemical biosensors have received particular attention, since the electrochemical response is particularly sensitive to the DNA structural changes from single-stranded, double-stranded, or hairpin into a G-quadruplex configuration. Furthermore, the development of an increased number of G-quadruplex aptamers that combine the G-quadruplex stiffness and self-assembling versatility with the aptamer high specificity of binding to a variety of molecular targets allowed the construction of biosensors with increased selectivity and sensitivity. This review discusses the recent advances on the electrochemical characterization, design, and applications of G-quadruplex electrochemical biosensors in the evaluation of metal ions, G-quadruplex ligands, and other small organic molecules, proteins, and cells. The electrochemical and atomic force microscopy characterization of G-quadruplexes is presented. The incubation time and cations concentration dependence in controlling the G-quadruplex folding, stability, and nanostructures formation at carbon electrodes are discussed. Different G-quadruplex electrochemical biosensors design strategies, based on the DNA folding into a G-quadruplex, the use of G-quadruplex aptamers, or the use of hemin/G-quadruplex DNAzymes, are revisited.

Time- and Composition-Dependent Evolution of Distinctive Microstructures in Bitumen

Bitumen’s chemistry often results in complicated intermolecular associations, which are manifested by the diverse microstructures as observed by atomic force microscopy (AFM). These microstructures largely contribute to bitumens’ bulk mechanical properties; therefore, it is essential to understand the chemical–microstructural–mechanical relationships for optimal design of bitumen-related applications. However, the complex nature of bitumen and the various influencing factors often lead to practical challenges in investigation of bitumens’ microstructures and their chemical origins. This study aims at addressing some of the main concerns related to AFM characterization of bitumens’ microstructures, namely the dependence of bitumens’ microstructures on such factors as sample preparation methods, annealing conditions and durations, and chemical composition. Our results suggest that microstructures of bitumen films of a few micrometers or thicker (i.e., the thickness of the asphalt-coating layer over the aggr...

Young’s modulus of multi-layer microcantilevers

A theoretical model for calculating the Young’s modulus of multi-layer microcantilevers with a coating is proposed, and validated by a three-dimensional (3D) finite element (FE) model using ANSYS parametric design language (APDL) and atomic force microscopy (AFM) characterization. Compared with typical theoretical models (Rayleigh-Ritz model, Euler-Bernoulli (E-B) beam model and spring mass model), the proposed theoretical model can obtain Young’s modulus of multi-layer microcantilevers more precisely. Also, the influences of coating’s geometric dimensions on Young’s modulus and resonant frequency of microcantilevers are discussed. The thickness of coating has a great influence on Young’s modulus and resonant frequency of multi-layer microcantilevers, and the coating should be considered to calculate Young’s modulus more precisely, especially when fairly thicker coating is employed.

Morphology and FT-IR analysis of anti-pollution flashover coatings with adding nano SiO2 particles

By adding nano SiO2 particles, an enhanced K-PRTV anti-pollution flashover coating had been prepared. Optical profile meter (GT-K), atomic force microscopy (AFM), infrared spectrometer (FT-IR) and EDS characterization were carried out on the coating surface analysis. Those results has been use to optimize the further design and platform of the enhanced K-PRTV pollution flash coating experiment. It is also to improve the plan formulation, formulation optimization and preparation of the hydrophobic modified K-PRTV which is based on anti-pollution coating experiment. More importantly, the anti-pollution flashover K-PRTV coating with super hydrophobic modified is the great significance for K-PRTV coating.

In situ growth of copper oxide-graphite carbon nitride nanocomposites with peroxidase-mimicking activity for electrocatalytic and colorimetric detection of hydrogen peroxide

This study reported a facile approach for the preparation of copper oxide-graphitic carbon nitride nanocomposites by an in situ growth method in aqueous solution. The powder X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and atomic force microscopy characterizations of the copper oxide-graphitic carbon nitride nanocomposites suggest that we have successfully synthesized a novel nanozyme. The nano-sized of copper oxide nanoparticles embedded in graphitic carbon nitride nanoparticles were evaluated focusing on the principle of horseradish peroxidase-like activity catalyzing the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine in the presence of hydrogen peroxide. Furthermore, we constructed dual sensor platforms based on copper oxide-graphitic carbon nitride nanocomposites. By constructing an electrochemical platform and a colorimetric sensor to detect hydrogen peroxide, it is shown that copper oxide-graphitic carbon nitride nanocomposites had an excellent peroxidase mimicking catalytic performance. We envision that our nanozyme have great potential in a variety of applications in catalytic field, electrochemical sensing, optical imaging, and environmental assay.

Electrical Homogeneity of Large-Area Chemical Vapor Deposited Multilayer Hexagonal Boron Nitride Sheets.

Large-area hexagonal boron nitride (h-BN) can be grown on polycrystalline metallic substrates via chemical vapor deposition (CVD), but the impact of local inhomogeneities on the electrical properties of the h-BN and their effect in electronic devices is unknown. Conductive atomic force microscopy (CAFM) and probe station characterization show that the tunneling current across the h-BN stack fluctuates up to 3 orders of magnitude from one substrate (Pt) grain to another. Interestingly, the variability in the tunneling current across the h-BN within the same substrate grain is very low, which may enable the use of CVD-grown h-BN in ultra scaled technologies.

Organic bioelectronic plasma polymerised polyterpenol thin films: preservation of properties relevant to biomedical and organic electronic applications following exposure to sterilising doses of gamma radiation

Plasma polymers such as polyterpenol have been investigated for use as biofunctional coatings, insulating/dielectric layers in electronics, and adhesion promoting interlayers in organic electronics. The commercialisation of plasma polymers in these and other biomaterial-related applications is contingent upon their ability to resist degradation in response to sterilising and potentially damaging ionising radiation, such as gamma rays. Hence, this study focusses on the stability of plasma polymerised polyterpenol thin films following exposure to gamma radiation doses ranging from 0 to 100 kGy. Irradiated films were subjected to ellipsometry, current–voltage, dielectric, Fourier transform infrared, and atomic force microscopy characterisation. Stability of polyterpenol was evidenced by the observed lack of radiation-induced variation in its complex refractive index, optical band gap, relative permittivity, dc conductivity, surface chemical functionalities, and surface morphology.

Acoustic and atomic force microscopy characterization of microbubbles with varying shell chemistry

Applications of microbubbles (MBs) in diagnostic and therapeutic interventions critically depend on their stability and scattering properties. The shell chemistry of MBs defines these properties. We investigated the effects of shell chemistry on the size, abundance, acoustic response, and mechanical properties of MBs by varying the poly(ethylene glycol) (PEG) molar ratio (0 to 100%) in a two-lipid (DPPC and DPPE-PEG2000) component shell formulation. Increasing PEG concentration from 0% to 10% resulted in an increase in the number of MBs by at least 10-fold, with adverse effects upon further increases. Microbubbles made with 5–10% PEG generated the strongest fundamental as well as nonlinear (subharmonic and second harmonic) components at the excitation frequency of 2.25 MHz. We used interfacial rheological models to determine the mechanical properties of MB shells as functions of PEG concentration using experimentally measured attenuation values. We also employed atomic force microscopy (AFM) to perform thin planar film characterization of the shells. The correlation between the AFM measurements of film properties and the acoustic responses of the corresponding coated MBs will be discussed.

Preparation and characterization of molecularly imprinted mussel inspired film as antifouling and selective layer for electrochemical detection of sulfamethoxazole

Abstract The present work describes the development of a novel simple and cheap electrochemical sensor based on molecularly imprinted polydopamine, for the detection of sulfamethoxazole (SMX) an antibiotic widely used in food industry. A double step procedure is used for sensor fabrication consisting in molecularly imprinted polydopamine (PDA-MIP) electropolymerization on a gold electrode and template removal through a simple washing procedure with diluted acetic acid. SMX detection was then performed amperometrically. A deep investigation of PDA-MIP electropolymerization was performed combining electrochemical, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) characterization and comparing the obtained results with the corresponding non-imprinted polymer (PDA-NIP), evidencing, for the first time, the possibility of secondary reaction that can occur between template molecule and polymer during material synthesis. Antifouling properties of here prepared PDA-MIP film were observed avoiding the use of complex cleaning procedure of electrode surface during the measurements. Under the selected optimum conditions, MIP sensor evidenced a linear range from 0.8 to 170 μM and a good selectivity in presence of other structurally related molecules such as sulfadimethoxine. The PDA-MIP film was then used for the first time in food analysis to determine SMX in spiked milk samples at two different concentrations (3.4 μM and 9.8 μM) obtaining satisfactory recovery results (103 ± 6% and 99 ± 8% respectively).

New Tethered Phospholipid Bilayers Integrating Functional G-Protein-Coupled Receptor Membrane Proteins.

Membrane proteins exhibiting extra- and intracellular domains require an adequate near-native lipid platform for their functional reconstitution. With this aim, we developed a new technology enabling the formation of a peptide-tethered bilayer lipid membrane (pep-tBLM), a lipid bilayer grafted onto peptide spacers, by way of a metal-chelate interaction. To this end, we designed an original peptide spacer derived from the natural α-laminin thiopeptide (P19) possessing a cysteine residue in the N-terminal extremity for grafting onto gold and a C-terminal extremity modified by four histidine residues (P19-4H). In the presence of nickel, the use of this anchor allowed us to bind liposomes of variable compositions containing a 2% molar ratio of a chelating lipid, 1,2-dioleoyl-sn-glycero-3-[(N-(5-amino-1-carboxypentyl)iminodiacetic acid)succinyl] so-called DOGS-NTA, and to form the planar bilayer by triggering liposome fusion by an α-helical (AH) peptide derived from the N-terminus of the hepatitis C virus NS5A protein. The formation of pep-tBLMs was characterized by surface plasmon resonance imaging (SPRi), and their continuity, fluidity, and homogeneity were demonstrated by fluorescence recovery after photobleaching (FRAP), with a diffusion coefficient of 2.5 × 10-7 cm2/s, and atomic force microscopy (AFM). By using variable lipid compositions including phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol 4,5-bisphosphate (PIP2), sphingomyelin (SM), phosphatidic acid (PA), and cholesterol (Chol) in various ratios, we show that the membrane can be formed independently from the lipid composition. We made the most of this advantage to reincorporate a transmembrane protein in an adapted complex lipid composition to ensure its functional reinsertion. For this purpose, a cell-free expression system was used to produce proteoliposomes expressing the functional C-X-C motif chemokine receptor 4 (CXCR4), a seven-transmembrane protein belonging to the large superfamily of G-protein-coupled receptors (GPCRs). We succeeded in reinserting CXCR4 in pep-tBLMs formed on P19-4H by the fusion of tethered proteoliposomes. AFM and FRAP characterization allowed us to show that pep-tBLMs inserting CXCR4 remained fluid, homogeneous, and continuous. The value of the diffusion coefficient determined in the presence of reinserted CXCR4 was 2 × 10-7 cm2/s. Ligand binding assays using a synthetic CXCR4 antagonist, T22 ([Tyr5,12, Lys7]-polyphemusin II), revealed that CXCR4 can be reinserted in pep-tBLMs with functional folding and orientation. This new approach represents a method of choice for investigating membrane protein reincorporation and a promising way of creating a new generation of membrane biochips adapted for screening agonists or antagonists of transmembrane proteins.

Characterization of screw dislocation-driven growth in nickel micro-nanostructure electrodeposition process by AFM

In this study, nickel coating with micro-nanostructure feature was fabricated by a simple two-step method during electrodeposition process. To evaluate surface morphology characteristics, the histogram and power spectral density analyses of atomic force microscopy data were extracted from two different morphologies of nickel films. Results showed that boric acid plays an important role in the control of nucleation and the growth of micro-nanostructures. With clear observation of growth steps in atomic force microscopy characterization, terrace width and spiral growth proved the existence of screw dislocation growth.

Role of sputtering power on the microstructural and electro‐optical properties of ITO thin films deposited using DC sputtering technique

The effects of sputtering power on the deposition rate as well as the microstructural, electrical, and optical properties of indium tin oxide (ITO) thin films are investigated in this paper. ITO thin films were deposited on glass substrates using direct current (DC) magnetron sputtering of different DC powers, ranging from 60 to 140 W, onto externally unheated glass substrates. All samples were grown at the minimum sustainable plasma pressure to reduce the destructive role of pressure. The microstructural, electrical, and optical properties of the sputtered ITO films were systematically characterized by X‐ray diffraction (XRD), atomic force microscopy (AFM), four‐probe electrical conductivity, and optical spectroscopy. XRD studies confirmed the cubic bixbyite ITO structure, and the main preferred orientations of the prepared thin films were (222), (400), (440), and (622). AFM analysis showed a minimum surface roughness of 1.37 nm for the films deposited at 140 W, while the average size of the grains was 65 ± 5 nm. The deposition time was fixed at 10 min for all samples, and the AFM characterization of the films showed 170, 230, and 250 nm thickness for the samples deposited at 60, 100 and 140 W, respectively. From the variations of the sheet resistance and the XRD patterns of the ITO thin films, it was concluded that, as the ratio I222/I400 of a sample approaches unity, the sheet resistance of the layer reduces. A minimum sheet resistance 16 Ω/square, transmittance 85% with the thickness of 230 nm, and optical bandgap 4.09 eV were found for the thin film grown on the externally unheated substrates at 100 W DC power and 32 mTorr working pressure. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Structural Characterization and computational approach to doped hafnium oxide nano crystals for thermo and photoluminescence applications

ABSTRACTDoped hafnium oxide (X-HfO2, X= Eu, Tb, Dy) thin films were deposited by experimental ultrasonic spray pyrolysis process. Doped Hf nano crystal (nc-X-Hf) embebed in the HfO2 matrix were obtained. The process was made at substrate temperature between 300 °C and 550 °C, showing at this higher temperature the monoclinic phase, which improve the dopants incorporation. Computational simulations were made to analyze molecular dynamics in advance to improve physical and chemical properties. Energy relaxation, and charge distribution behaviour demonstrated an atomic re-arranged to form the nano clusters of 5nm to 10 nm diameter. Vibrational modes were calculated. Photoluminescence (PL) spectra were obtained, as dopant function. Atomic Force Microscopy (AFM), X-ray diffraction and High Resolution Transmission Electron Microscopy (HRTEM) characterizations were made. Characteristics bright peaks appear in the Thermoluminescence (TL) spectra, and PL peak emission as well, of the Eu, Tb, Dy dopants in the HfO2 matrix. The results obtained show that nanocrystal structures embebed in a metal oxide matrix of HfO2 could be a prominent material to be used in radiation dosimetry, technological development, and radiological protection.