Contact Atomic Force Microscopy Research Articles

(Digital Presentation) Investigation of Microstructure Dependent Inhibitor Adsorption Mechanism on Carbon Steel By in Situ Atomic Force Microscopy

In the petroleum industry, organic surfactant type inhibitors have been widely applied in the oil and gas industry considering their high efficiency. Carbon steels with various carbide contents have also been used extensively as pipeline materials during the transport and storage of crude oil due to their excellent mechanical properties and low cost. The previous investigation of inhibition mechanism on carbon steel is limited by lack of surface characterization techniques at a molecular level. Atomic force microscopy (AFM) can not only provide localized visual observation, but can also achieve the detection of mechanical properties of an inhibitor film. In this study, in situ AFM contact mode friction imaging and in situ AFM tapping mode phase imaging techniques have been applied to investigate the influence of the ferritic-pearlitic microstructure of carbon steel on inhibitor adsorption mechanisms during CO2 corrosion under different inhibitor concentrations. At concentration above surface saturation, AFM contact mode friction images show a large friction contrast between inhibitor covered cementite structures and ferrite structures, while in the absence of inhibitor, this friction contrast almost disappears, indicating the inhibitor adsorption induced this difference. AFM tapping mode phase images indicate uniform adsorption of inhibitor on both cementite and ferrite structures.The differences observed in these AFM analyses indicate that the adhesion force of inhibitor molecules on cementite could be smaller than on ferrite, or the molecular orientations of inhibitor molecules adsorbed on cementite and ferrite structures could be different. The special adsorption behavior of inhibitor molecules on cementite means the carbide component of the microstructure could directly influence inhibitor adsorption and may decrease inhibitor efficiency. Simultaneous linear polarization resistance tests in electrochemical AFM (EC-AFM) cell indicates a maximum inhibition efficiency at concentration above saturation.Keywords : Contact mode AFM, friction contrast, tapping mode AFM, phase contrast, cementite, ferrite, organic inhibitor, adhesion force.Statement of importance:Studies related to inhibitor adsorption mechanisms on ferritc-pearlitic carbon steels can be connected with the practical issues that iron carbide can impair the corrosion inhibitor performance on carbon steels. This AFM work connects the corrosion inhibition effect with the carbon steel components at a molecular level for the first time. Physical explanations regarding the interactions between inhibitor molecules and carbon steel microstructures can also be provided with the assistance of molecular simulations.Figure caption: Contact and tapping mode AFM images of inhibitor film formed on UNS G1018 steel at 2 CMC (100ppm) tetradecyldimethylbenzylammonium inhibitor + 1 wt% NaCl. The contact mode friction image indicates a large friction contrast between inhibitor covered cementite and ferrite structure, while the tapping mode phase image indicates a negligible softness contrast between cementite and ferrite structure. Figure 1

Comparison of the physicochemical properties and aging behavior of two different APTES-derived plasma polymer-based coatings

Recently, new plasma polymerization-based techniques emerged to deposit chemically functional coatings for various applications. However, little is known on the aging of these layers. Therefore, this study aims to investigate the physicochemical properties of aerosol-assisted atmospheric pressure plasma deposited (3-aminopropyl)triethoxysilane-based (AAPD-APTES) coatings and compare their aging behavior to APTES-modified plasma polymerized hexamethyldisiloxane-based coatings (ppHMDSO-APTES). X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), water contact angle (WCA) and atomic force microscopy (AFM) measurements indicated that the applied power had an insignificant impact on the wettability, chemistry and morphology of the AAPD-APTES films. A complex nitrogen-containing organosilicon layer was obtained with significant preservation of the Si-O-C-bonds. For the ppHMDSO-APTES coatings, XPS indicated that these layers had a significantly higher amount of preserved primary amines and a different surface morphology. Oxidation and hydrolysis of Si-O-C-bonds were the most prevalent aging processes for the AAPD-APTES coatings, while protonation of primary amines was most important for the ppHMDSO-APTES films. This study indicates that further research is needed to examine the differences in coating chemistry and aging of other AAPD-based and conventional plasma polymers. Additionally, it provides a reference to decide which coating type and associated aging processes are preferred for certain applications.

Assuring the Biofunctionalization of Silicone Covalently Bonded to Rhamnolipids: Antibiofilm Activity and Biocompatibility.

Silicone-based medical devices composed of polydimethylsiloxane (PDMS) are widely used all over the human body (e.g., urinary stents and catheters, central venous catheters stents) with extreme clinical success. Nevertheless, their abiotic surfaces, being prone to microorganism colonization, are often involved in infection occurrence. Improving PDMS antimicrobial properties by surface functionalization with biosurfactants to prevent related infections has been the goal of different works, but studies that mimic the clinical use of these novel surfaces are missing. This work aims at the biofunctional assessment of PDMS functionalized with rhamnolipids (RLs), using translational tests that more closely mimic the clinical microenvironment. Rhamnolipids were covalently bonded to PDMS, and the obtained surfaces were characterized by contact angle modification assessment, ATR-FTIR analysis and atomic force microscopy imaging. Moreover, a parallel flow chamber was used to assess the Staphylococcus aureus antibiofilm activity of the obtained surfaces under dynamic conditions, and an in vitro characterization with human dermal fibroblast cells in both direct and indirect characterization assays, along with an in vivo subcutaneous implantation assay in the translational rabbit model, was performed. A 1.2 log reduction in S. aureus biofilm was observed after 24 h under flow dynamic conditions. Additionally, functionalized PDMS lessened cell adhesion upon direct contact, while supporting a cytocompatible profile, within an indirect assay. The adequacy of the biological response was further validated upon in vivo subcutaneous tissue implantation. An important step was taken towards biofunctional assessment of RLs-functionalized PDMS, reinforcing their suitability for medical device usage and infection prevention.

Spin-induced asymmetry reaction-The formation of asymmetric carbon by electropolymerization.

We describe the spin polarization–induced chirogenic electropolymerization of achiral 2-vinylpyridine, which forms a layer of enantioenhanced isotactic polymer on the electrode. The product formed is enantioenriched in asymmetric carbon polymer. To confirm the chirality of the polymer film formed on the electrode, we also measured its electron spin polarization properties as a function of its thickness. Two methods were used: First, spin polarization was measured by applying magnetic contact atomic force microscopy, and second, magnetoresistance was assessed in a sandwich-like four-point contact structure. We observed high spin-selective electron transmission, even for a layer thickness of 120 nm. A correlation exists between the change in the circular dichroism signal and the change in the spin polarization, as a function of thickness. The spin-filtering efficiency increases with temperature.

Surface potential and local conductivity measurements of micropatterned aromatic monolayers covalently attached to n-Si(111) via Si–C and Si–O bonds

The surface potentials and local conductivity of self-assembled monolayers (SAMs) formed using aromatic molecules covalently bonded to n-type silicon (111) via Si–C and Si–O bonds were measured using Kelvin probe force microscopy (KPFM) and conductive AFM (CAFM). Surface potential measurements were done using micropatterned SAMs with hexadecyl SAM as a reference to eliminate surface potential variations due to the cantilever tips. Micropatterning was conducted via vacuum ultraviolet photolithography at λ = 172 nm. Ellipsometry, X-ray photoelectron spectroscopy, static water contact angle and atomic force microscopy tests show that the aromatic SAMs were well-organized despite the short molecular lengths of the precursors. KPFM results show that Si–C bonded SAMs have higher surface potentials compared to Si–O SAMs, which is in agreement with dipole moments estimated by Molecular Orbital Package semi-empirical computations. CAFM scans showed conductive domains for the aromatic SAM regions, and Si–O SAMs exhibited a higher current than Si–C SAMs.

Ability to Inhibit H+ Transmission of Gemini Surfactants with Different Chain Lengths under Different Ca2+ Circumstances.

To study the ability to inhibit ion transmission of the Gemini surfactant under different Ca2+ circumstances, three kinds of Gemini surfactants with different alkyl chain lengths are synthesized (Cn-4-Cn, n = 12, 14, and 16), which are characterized using 1H NMR, 13C NMR, and Fourier transform infrared spectroscopy. To analyze the property of inhibition of the acid–rock reaction rate, surface tension and contact angle measurements and atomic force microscopy (AFM) results are obtained with different surfactants and under different Ca2+ concentrations. Inhibition rates with different alkyl chain lengths and an acid-etched surface morphology are also studied carefully. The result shows that all cationic Gemini surfactants significantly impact the control of the reaction rate, and the reaction rate decreased remarkably by 44.4% after adding 12-4-12. The ΔG and WA indicate that 12-4-12 has the best adsorption ability on the rock with added Ca2+ compared with the other two Gemini surfactants. It is revealed through the AFM that Ca2+ can significantly change the adsorption morphology of the surfactant. The surfactant adsorption area decreased when Ca2+ is dispersed in the solution as well. These two phenomena can lead to the reduced ability to block H+ of 14-4-14 and 16-4-16. However, the presence of Ca2+ affects the adsorption area of 12-4-12 slightly. Thus, the reaction rate, including that of 12-4-12, is almost unchanged. Because 12-4-12 is adsorbed tightly on the rock surface, H+ can only react with the rock on the unabsorbed dot, resulting in rock surface nonuniformity after being etched, which is beneficial for maintaining the conductivity of the crack.

Fabrication and Characterization of Polycaprolactone with Retinoic Acid and Cerium Oxide for Anticancer Applications

In the present study, poly (ε-caprolactone) (PCL) composite electrospun nanofibers were fabricated by combining PCL, retinoic acid (RA), and cerium oxide (CeO2). The parameters processing of material fibers by electrospinning were optimized to obtain PCL-based electrospun nanofiber to be used in drug delivery. The results showed that combined solvents and polymer concentration were found to play key roles in determining the morphology of nanofiber. A single solvent (Dimethylformamide DMF, 100%) favored the beads' formation, whereas beadless fibers were produced with mixed solvents(DMF, chloroform, and methanol). The formation of beads was clearly inhibited due to an increased concentration from 10 to 15% w/v of the polymer. Nanofibers of PCL, PCL/RA, PCL/CeO2, and PCL/RA/CeO2 were fabricated and characterized using the combined techniques of SEM (scanning electron microscopy), FTIR (Fourier transform infrared), XRD (X-ray diffraction), TGA (thermogravimetric analysis), contact angle measurements and AFM (atomic force microscopy). The SEM micrographs of RA/CeO2 loaded PCL nanofibers exhibited similar morphology, and none of them showed bead formation or the presence of RA or CeO2 on the surface of the nanofiber matrices. The nanofibers loaded with 0.5% RA/CeO2 drug have the highest diameter (130 ± 33 nm), and the pure PCL nanofibers showed the smallest diameter (74 ± 20 nm) among all the drug-loaded samples evaluated. Also, the XRD analysis displayed the very low crystallinity of RA/CeO2 in PCL loaded with RA/CeO2. The result shows that the drug-loaded nanofiber has similar thermal stability to the PCL nanofiber, indicating that the addition of RA and CeO2 decreases the hydrophobicity. The drug-loaded nanofiber has higher surface roughness than the PCL nanofiber, according to AFM data. Based on the results, PCL/RA/CeO2 nanofiber is considered a potential material for drug delivery applications.

New insights into the role of calcium dioleate in selectively separating fluorite from calcite during cleaning process

Research on fluorite and calcite cleaning process have been ignoring the effects of calcium dioleate in pulp on flotation. In this study, flotation tests showed that flotation separation of fluorite and calcite could be achieved by the cleaning process under acidic conditions. Solution chemistry equilibrium calculations revealed that large amounts of calcium dioleate formed, and this compound was the main component in the cleaning solutions of fluorite and calcite under acidic conditions. Desorption and adsorption tests, contact angle measurements and atomic force microscopy (AFM) revealed the mechanism of selective separation of fluorite and calcite during the cleaning process under acidic conditions. Flotation tests showed that under acidic conditions, calcite flotation was strongly inhibited but fluorite flotation was less affected. Desorption and adsorption measurements and mineral surface contact angle analysis revealed that under acidic conditions, the calcium dioleate on the surface of calcite rough concentrate was desorbed into the solution, whereas the calcium dioleate in the solution did not readily absorb on calcite surface. The calcium dioleate on the surface of fluorite rough concentrate was hardly desorbed, whereas the calcium dioleate in the solution continued to adsorb on the surface. AFM intuitively confirmed the desorption of calcium dioleate from calcite surface and the adsorption of this compound on fluorite surface under acidic conditions. The selective adsorption of calcium dioleate on fluorite rough concentrate is an important factor that promotes the selective separation of fluorite and calcite during the cleaning process.

The competing influence of surface roughness, hydrophobicity, and electrostatics on protein dynamics on a self-assembled monolayer.

Surface morphology, in addition to hydrophobic and electrostatic effects, can alter how proteins interact with solid surfaces. Understanding the heterogeneous dynamics of protein adsorption on surfaces with varying roughness is experimentally challenging. In this work, we use single-molecule fluorescence microscopy to study the adsorption of α-lactalbumin protein on the glass substrate covered with a self-assembled monolayer (SAM) with varying surface concentrations. Two distinct interaction mechanisms are observed: localized adsorption/desorption and continuous-time random walk (CTRW). We investigate the origin of these two populations by simultaneous single-molecule imaging of substrates with both bare glass and SAM-covered regions. SAM-covered areas of substrates are found to promote CTRW, whereas glass surfaces promote localized motion. Contact angle measurements and atomic force microscopy imaging show that increasing SAM concentration results in both increasing hydrophobicity and surface roughness. These properties lead to two opposing effects: increasing hydrophobicity promotes longer protein flights, but increasing surface roughness suppresses protein dynamics resulting in shorter residence times. Our studies suggest that controlling hydrophobicity and roughness, in addition to electrostatics, as independent parameters could provide a means to tune desirable or undesirable protein interactions with surfaces.

Mechanofluorochromic Material toward a Recoverable Microscale Force Sensor

AbstractAmong the multiple classes of mechanofluorochromic (MFC) compounds reported in recent years, simple donor–acceptor molecules involving oligooxyethylene N‐substituted diphenylamine connected to a dicyanovinyl group by a thienyl spacer constitute a specific class of mechano‐stimulable smart materials with a unique combination of properties including turn‐on mechanofluorochromism with red‐light photoluminescence emission, turn‐off second harmonic generation, and self‐recovery in ambient conditions. While the dynamics of the MFC processes of thin films of these materials have already been investigated, the correlation of the behavior observed at the macroscale with elemental processes taking place at the micro‐ and nanoscopic scales remains largely unexplored. In this work, atomic force microscopy (AFM) coupled with wide‐field and confocal optical microscopies is used to investigate the turn‐on/recovery MFC behavior of microcrystals and nanostructures. It is shown that the red light photoluminescence of microcrystals and nano‐objects can be turned‐on by contact AFM and that the intensity of light emission is linearly correlated to the applied nominal force. Recovery is associated with a decrease in emission intensity, which can be reactivated again by subsequent contact scans. These results thus pave the way toward the development of micro‐/nanoscale recoverable force‐sensing technologies based on this particular class of smart molecular materials.

Boxcar Averaging Scanning Nonlinear Dielectric Microscopy.

Scanning nonlinear dielectric microscopy (SNDM) is a near-field microwave-based scanning probe microscopy method with a wide variety of applications, especially in the fields of dielectrics and semiconductors. This microscopy method has often been combined with contact-mode atomic force microscopy (AFM) for simultaneous topography imaging and contact force regulation. The combination SNDM with intermittent contact AFM is also beneficial for imaging a sample prone to damage and using a sharp microscopy tip for improving spatial resolution. However, SNDM with intermittent contact AFM can suffer from a lower signal-to-noise (S/N) ratio than that with contact-mode AFM because of the shorter contact time for a given measurement time. In order to improve the S/N ratio, we apply boxcar averaging based signal acquisition suitable for SNDM with intermittent contact AFM. We develop a theory for the S/N ratio of SNDM and experimentally demonstrate the enhancement of the S/N ratio in SNDM combined with peak-force tapping (a trademark of Bruker) AFM. In addition, we apply the proposed method to the carrier concentration distribution imaging of atomically thin van der Waals semiconductors. The proposed method clearly visualizes an anomalous electron doping effect on few-layer Nb-doped MoS2. The proposed method is also applicable to other scanning near-field microwave microscopes combined with peak-force tapping AFM such as scanning microwave impedance microscopy. Our results indicate the possibility of simultaneous nanoscale topographic, electrical, and mechanical imaging even on delicate samples.

Research of the replacement of dichromate with depressants mixture in the separation of copper-lead sulfides by flotation

• Humic substance and hydrogen peroxide are promising depressants on galena. • The hydrogen peroxide can accelerate dissolution of galena lattice. • An adsorption model is finally obtained. To reduce the environmental impact caused by highly toxic dichromate in flotation separation of copper-lead sulfide, the replacement of dichromate with depressants mixture (humic substance and hydrogen peroxide) was investigated in this paper. The single mineral flotation and the mixed binary minerals experiment at pH 6.5 showed that combined depressants could be efficient in separating galena from chalcopyrite and achieve a lead concentrate comparable to conventional method using dichromate as typical depressant. The contact angle measurement and atomic force microscopy (AFM) imaging indicated that, for the same concentration of sodium humate, the treatment by hydrogen peroxide could increase surface wettability and largely enhance chemical adsorption of humate on galena surface. Ion dissolution tests and adsorption tests indicated that the hydrogen peroxide can accelerate dissolution of galena lattice and the hydrogen peroxide or Pb 2+ could promote the adsorption of NaHA on the surface of galena.

Water-Resistant Surface Modification of Hydrophobic Polymers with Water-Soluble Surfactant Additives.

Water-soluble nonionic surfactant, pentaethylene glycol monododecyl ether, C12E5, spontaneously blooms to the surface of spin-cast hydrophobic polyisoprenes, generating hydrophilic surfaces. This system provides a simple model for hydrophilic chemical modification of rubbery polymers that demonstrates surprisingly rich, complex, and unexpected behaviour. The vertical depth profiles were quantified using neutron reflectometry (NR) using a novel procedure to account for undulations in the film thickness. Surface properties were characterized using contact angle analysis and atomic force microscopy (AFM). Despite the low surface tension of the toluene solvent used in film preparation and the low surface energy of the polyisoprene (PI) matrix, NR depth profiles revealed clear evidence of surfactant segregation. This surface layer was typically thicker than a monolayer, but incomplete, yet was remarkably stable with respect to dissolution, even when exposed to hundreds of thousands of times the volume of water required to dissolve all the surfactant on the surface. Despite the apparent resistance to removal from the surface, water exposure does alter the subsequent wettability of the surface, with a hydrophilic-to-hydrophobic transition occurring after rinsing. Complementary AFM images of these C12E5/cis-PI films showed unexpected strand-like features on the surface of the film, which we attribute to a non-uniform lateral distribution of some of the surfactant. This surface structure becomes more evident after rinsing, and it appears that there are two distinct populations of surfactant on the PI film surface. We conclude that some of the bloomed surfactant exists as layers, which are relatively inert with respect to rinsing or surface modification, and some is laterally inhomogeneous. This latter population is primarily responsible for surface wetting behaviour but is not detected by specular NR.

Miktoarm Star Copolymers Prepared by Transformation from Enhanced Spin Capturing Polymerization to Nitroxide-Mediated Polymerization (ESCP-Ŧ-NMP) toward Nanomaterials.

Reversible-deactivation radical polymerization (RDRP) serves as a powerful tool nowadays for the preparations of unique linear and non-linear macromolecules. In this study, enhanced spin capturing polymerizations (ESCPs) of styrene (St) and tert-butyl acrylate (tBA) monomers were, respectively, conducted in the presence of difunctional (1Z,1′Z)-1,1′-(1,4-phenylene) bis (N-tert-butylmethanimine oxide) (PBBN) nitrone. Four-arm (PSt)4 and (PtBA)4 star macroinitiators (MIs) can be afforded. By correspondingly switching the second monomer (i.e., tBA and St), miktoarm star copolymers (μ-stars) of (PSt)2-μ-(PtBA-b-PSt)2 and (PtBA)2-μ-(PSt-b-PtBA)2) were thus obtained. We further conducted hydrolysis of the PtBA segments to PAA (i.e., poly(acrylic acid)) in μ-stars to afford amphiphilic μ-stars of (PSt)2-μ-(PAA-b-PSt)2 and (PAA)2-μ-(PSt-b-PAA)2. We investigated each polymerization step and characterized the obtained two sets of “sequence-isomeric” μ-stars by FT-IR, 1H NMR, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). Interestingly, we identified their physical property differences in the case of amphiphilic μ-stars by water contact angle (WCA) and atomic force microscopy (AFM) measurements. We thus proposed two microstructures caused by the difference of polymer chain sequences. Through this polymerization transformation (Ŧ) approach (i.e., ESCP-Ŧ-NMP), we demonstrated an interesting and facile strategy for the preparations of μ-stars with adjustable/switchable interior and exterior polymer structures toward the preparations of various nanomaterials.

Exploring Nanomechanical Properties of Soot Particle Layers by Atomic Force Microscopy Nanoindentation

In this work, an experimental investigation of the nanomechanical properties of flame-formed carbonaceous particle layers has been performed for the first time by means of Atomic Force Microscopy (AFM). To this aim, carbon nanoparticles with different properties and nanostructures were produced in ethylene/air laminar premixed flames at different residence times. Particles were collected on mica substrates by means of a thermophoretic sampling system and then analyzed by AFM. An experimental procedure based on the combination between semi-contact AFM topography imaging, contact AFM topography imaging and AFM force spectroscopy has been implemented. More specifically, a preliminary topological characterization of the samples was first performed operating AFM in semi-contact mode and then tip-sample interaction forces were measured in contact spectroscopy mode. Finally, semi-contact mode was used to image the indented surface of the samples and to retrieve the projected area of indents. The hardness of investigated samples was obtained from the force–distance curves measured in spectroscopy mode and the images of intends acquired in semi-contact mode. Moreover, the Young’s modulus was measured by fitting the linear part of the retraction force curves using a model based on the Hertz theory. The extreme force sensitivity of this technique (down to nNewton) in addition to the small size of the probe makes it extremely suitable for performing investigation of mechanical properties of materials at the nanoscale. The experimental procedure was successfully tested on reference materials characterized by different plastic behavior, e.g., polyethylene naphthalate and highly oriented pyrolytic graphite. Both hardness and Young’s modulus values obtained from AFM measurements for different soot particle films were discussed.

Experimental investigation of water sensitivity effects on microscale mechanical behavior of shale

Drilling and multi-stage hydraulic fracturing bring a large amount of water into clay-bearing shale reservoirs, which may lead to attenuation of fracturing effects and wellbore instability. However, a thorough understanding of changes in shale micromechanics and corresponding mechanisms when exposed to water remains unclear. In this work, samples were selected based on clay enrichment. Subsequently, the contact resonance (CR) technique based on atomic force microscopy (AFM) was performed to characterize the micromechanics of shales after exposure to water. Visual phenomena provided by environmental scanning electron microscopy (ESEM) assisted to explain the underlying mechanisms. It was found that the hydration effect lowered both the storage modulus and stiffness of samples, but with different contributions from brittle minerals and clay, as well as variations depending on bedding plane orientation. Due to the difference in composition, the investigated terrestrial shale material exhibited stronger water sensitivity and anisotropy, with a general decrease of 15%–25% in storage modulus, compared with variations of -5%–15% in modulus of marine shale samples. Moreover, microscopic observation experiments revealed that the reduction of capillary force and the interlaminar swelling of clay particles might have been active after water adsorption, which led to the decreases of modulus and stiffness values. However, the swelling-caused confining effect or void space closure during the water imbibition process might have offset this weakening effect and even increased storage modulus. At mesoscale , excessive shrinkage caused the growth of micro-cracks, which in turn significantly attenuated overall mechanical properties. • Comparison of clay composition between terrestrial and marine shale based on clay enrichment. • AFM contact resonance method to characterize the micromechanical properties of shale before and after water adsorption. • Investigation of mechanisms of microscale mechanical changes in hydration and dehydration processes.

Antibacterial catechol-based hyaluronic acid, chitosan and poly (N-vinyl pyrrolidone) coatings onto Ti6Al4V surfaces for application as biomedical implant

Bacterial contamination in implanted biomedical devices is a critical daily concern. The most used material for permanent implant in biomedical field is Ti6Al4V alloy due to its beneficial mechanical properties and high biocompatibility. Accordingly, in this work different polymeric antibacterial coatings poly(N-vinyl pyrrolidone) (PVP), hyaluronic acid (HA) and chitosan (CHI) were developed and comparatively analysed for Ti6Al4V surface covering. The adhesion of these coatings to Ti6Al4V substrates were carried out after the conjugation of these polymers with the so well-known bioadhesive properties of catechol (CA) anchor group. These surface modifications were characterized by X-ray photoelectronic spectroscopy, contact angle measurements and atomic force microscopy. In addition, the stability of CA-conjugated polymeric coatings was compared with the coatings formed with unconjugated polymers. Finally, the cytocompatibility and antibacterial properties against gram-positive and gram-negative strains on coated Ti6Al4V substrates were assessed confirming the effectiveness of these polymeric coatings against bacterial infections for future applications in protecting biomedical implants.

Macromolecular Chain Structures of Atactic Poly(methyl methacrylate) Visualized on Hydrophilized Graphene Surfaces by Atomic Force Microscopy

Surface treatment of cleaved graphene surfaces with UV/ozone exposure, O2 reactive ion etching, and Ar ion milling was studied by contact angle measurements and atomic force microscopy (AFM). The c...

Self-assembled monolayers of novel imidazole derivative on copper surface for anticorrosion protection in neutral medium

In this paper, we report the 1-(3-aminopropyl)-2-methyl-1-imidazole (APMI) as self-assembled monolayers (SAMs) on copper surface via self-assembly to improve anticorrosion properties. Surface structure and bonding, chemical compositions, wettability and morphology of APMI SAMs on the surface of copper have been investigated by various surface analyses including FT-IR spectroscopy, energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), contact angle measurement (CA) and atomic force microscopy (AFM). FT-IR and XPS analysis show that the APMI molecules are successfully self-assembled on the copper surface, forming a compact protective monolayer. CA measurements revealed the hydrophobic nature of SAMs. The corrosion resistivity of APMI SAMs against corrosion in 3% NaCl solution were studied by Tafel polarization and cyclic voltammetry techniques coupled with scanning electron microscopy and the results show that formed APMI monolayer on copper could prevent the corrosion reaction at the copper-solution interface effectively. The adsorption and corrosion inhibition behaviour of APMI SAMs on Cu are also investigated by quantum chemical calculations. Further, the obtained results from the present inhibitor were compared with the existed inhibitors from the literature.

Kelvin probe force microscopy studies on the influence of hydrocarbon chain length on 1-alkene self-assembled monolayers on Si (111)

Surface potential contrasts were measured for n-type silicon (111) modified with 1-alkene self-assembled monolayers (SAMs) of varying hydrocarbon chain lengths (n = 10–20) using Kelvin probe force microscopy (KPFM). Micropatterned SAMs were used in KPFM analysis, with hexadecyl SAM acting as a reference to avoid possible variations due to different KPFM cantilever tips used for analysis. Micropatterning was performed via vacuum ultraviolet photolithography at λ = 172 nm. Individual samples were also analyzed by ellipsometry, X-ray photoelectron spectroscopy, static water contact angle tests and atomic force microscopy to determine SAM quality. Surface potential changes observed between the different SAMs were attributed to differences in the dipole moment of the precursor molecules, changes in SAM dielectric properties due to differences in molecular packing, and varying oxygen content at the surface.