Scanning Force Microscopy Research Articles

Electrophoretic deposition of novel antibacterial and biocompatible polydopamine and ZIF-8 hybrid composite coating on anodized Ti-6Al-4V alloy with silane primary substrate

Production of biocompatible and corrosion resistance dental implant is a requirement in the modern dental science. In this work, the Ti-6Al-4V was used alloy for the dental implant application that has investigated to make it more corrosion resistive and antibacterial with electrophoretic deposition of silane precursor solution that made of acidic solution of tetraethyl orthosilicate (TEOS) and methyl three ethoxy silane (MTES). The optimized silane coating has been achieved with 30 V, 30 min and at 100 °C ramped annealing by comparison of Taffel analysis and electrochemical impedance spectroscopy (EIS). Also, a new nanocomposite including polydopamine (PDA) and zeolite imidazole frame work composed from Zn (NO3)2 .6H2O and 2-methylimidazole (ZIF-8) that name PDA@ZIF-8 has been used as biocompatible and corrosion resistance amplifier to the precursor solution and used in the multilayer deposition process. The morphology analysis including atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) imaging and the obtained parameters show that coating has appropriate roughness that could increase the bounding of implant. A good adhesion strength has been determined for the two-layers silane coating with PDA@ZIF-8 according to the pull- off test. On the other hand, the antibacterial analysis indicate that the coating is an effective material for S. mutans and E. coli reduction that is another criterion for the dental implant materials. The results was introduced the coated Ti-6Al-4V could be used as corrosion resistive and antibacterial dental implant material.

Recent Progress of Imaging Chemical Bonds by Scanning Probe Microscopy: A Review.

In the past decades, the invention of scanning probe microscopy (SPM) as the versatile surface-based characterization of organic molecules has triggered significant interest throughout multidisciplinary fields. In particular, the bond-resolved imaging acquired by SPM techniques has extended its fundamental function of not only unraveling the chemical structure but also allowing us to resolve the structure-property relationship. Here, we present a systematical review on the history of chemical bonds imaged by means of noncontact atomic force microscopy (nc-AFM) and bond-resolved scanning tunneling microscopy (BR-STM) techniques. We first summarize the advancement of real-space imaging of covalent bonds and the investigation of intermolecular noncovalent bonds. Beyond the bond imaging, we also highlight the applications of the bond-resolved SPM techniques such as on-surface synthesis, the determination of the reaction pathway, the identification of molecular configurations and unknown products, and the generation of artificial molecules created via tip manipulation. Lastly, we discuss the current status of SPM techniques and highlight several key technical challenges that must be solved in the coming years. In comparison to the existing reviews, this work invokes researchers from surface science, chemistry, condensed matter physics, and theoretical physics to uncover the bond-resolved SPM technique as an emerging tool in exploiting the molecule/surface system and their future applications.

Evaluation of AlN insertion layer on the properties of heterogeneous integrated Ga2O3 films on sapphire

Integration of gallium oxide (Ga2O3) with highly thermal conductive AlN/sapphire substrate is more effective to dissipate heat in the Ga2O3-based devices. In this work, the properties of Ga2O3 films grown on sapphire and AlN/sapphire substrates via MOCVD were both examined via various experimental methods. The X-ray diffraction (XRD) analysis showed good crystallinity and different orientations of Ga2O3 and AlN thin films. The absorption properties and band gaps were extracted from UV/Vis spectra. The atomic force microscopy (AFM) scanning images showed smooth Ga2O3 surfaces on sapphire and AlN/sapphire substrates (RMSs of 2.4 nm and 4.8 nm, respectively). The scanning electron microscopy (SEM) highlighted well-defined grains of Ga2O3 and distinct boundaries of both heterostructures. X-ray photoelectron spectroscopy (XPS) analysis depicted the distributions of various components throughout the films. Finally, by using the time-domain thermoreflectance (TDTR) method, the thermal conductivity and the thermal boundary conductivity of Ga2O3 without AlN interlayer were found to be 3.1 W/(m·K) and 70.1 MW/(m2·K) respectively. By comparison, adding AlN interlayer made the thermal conductivity and thermal boundary conductivity rise to 3.3 W/(m·K) and 111.5 MW/(m2·K) respectively. These findings have demonstrated the high-quality Ga2O3/AlN integration and good heat dissipation provided by AlN interlayer, opening up new prospects for Ga2O3/AlN devices in the future.

Computational Support to Explore Ternary Solid Dispersions of Challenging Drugs Using Coformer and Hydroxypropyl Cellulose.

A majority of drugs marketed in amorphous formulations have a good glass-forming ability, while compounds less stable in the amorphous state still pose a formulation challenge. This work explores ternary solid dispersions of two model drugs with a polymer (i.e., hydroxypropyl cellulose) and a coformer as stabilizing excipients. The aim was to introduce a computational approach by preselecting additives using solubility parameter intervals (i.e., overlap range of solubility parameter, ORSP) followed by more advanced COSMO-RS theory modeling. Thus, a mapping of calculated mixing enthalpy and melting points is proposed for in silico evaluation prior to hot melt extrusion. Following experimental testing of process feasibility, the selected formulations were tested for their physical stability using conventional bulk analytics and by confocal laser scanning and atomic force microscopy imaging. In line with the in silico screening, dl-malic and l-tartaric acid (20%, w/w) in HPC formulations showed no signs of early drug crystallization after 3 months. However, l-tartaric acid formulations displayed few crystals on the surface, which was likely a humidity-induced surface phenomenon. Although more research is needed, the conclusion is that the proposed computational small-scale extrusion approach of ternary solid dispersion has great potential in the formulation development of challenging drugs.

Theory for measuring electric charge density of a ring from scanning force microscopy

We consider a ring that carries an arbitrary electric charge density in the presence of a scanning force microscopy tip. We propose an algorithm that predicts this charge density from knowledge of the electrostatic ring-tip contribution to the total scanning force microscopy force–distance curves. We first solve the direct electrostatic problem of finding the electrostatic forces by the ring on a scanning force microscopy conducting probe. These forces are in the pN and nN range and, therefore, measurable with current technologies. Finally, we describe a method based on the least squares minimization method to measure the charge on the ring.

Amorphous to Polycrystalline Phase Transition of In Situ Annealed Ge Films: Structural, Morphological, Optical, and Electrical Characteristics

AbstractRadio Frequency (RF) sputtered germanium (Ge) thin films were deposited on glass substrate at in situ annealing temperatures of 400, 450, 500, 550, and 600 °C. X‐ray diffraction (XRD) and Raman spectroscopy revealed that the Ge films were initially amorphous but transformed to polycrystalline after annealing at 450 °C. Further annealing up to 600 °C resulted in improved crystallinity. Strain studies of the films using XRD and Raman showed compressive (out‐of‐plane) and tensile (in‐plane) strains, respectively, throughout all the annealing temperatures. The surface morphology of the films was recorded using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM), which showed grain growth with annealing temperatures. The optical energy gap evaluated from absorption spectra for crystalline films decreased with annealing temperature, indicating improvement in crystallinity of films. The resistivity of the films deduced using current‐voltage measurements was found to decrease with annealing temperature, which can be attributed to enhancement in grain size. This study establishes a correlation between strain, grain size, optical energy gap, and electrical resistivity with temperature for Ge films deposited on glass substrates. Thus, the present study provides insights into variation in physical and electrical properties of films with in situ annealing temperature for their applicability in optoelectronic devices.

Effects of carbon nanoparticle insertion on stress reduction in hydrogenated amorphous carbon films using plasma chemical vapor deposition

Stress reduction in hydrogenated amorphous carbon (a-C:H) films is of considerable interest for improving their performance as protective films. Herein, we reduced the compressive stress of the films by inserting carbon nanoparticles (CNPs) between two a-C:H layers to form an a-C:H/CNP/a-C:H sandwich structure using a system of plasma chemical vapor deposition (CVD). We measured the deposition features of the CNPs via transmission electron microscopy (TEM) and assessed the dependence of the stress on the thickness of the second a-C:H layer as a parameter of surface coverage, Cp. We represented the stress reduction as a function of Cp; mean size of large CNPs, and thickness of the first and second a-C:H layers. In addition, the surface and film morphologies were investigated using atomic force microscopy (AFM) and cross-sectional scanning electron microscopy (SEM). Compared with films without CNPs, those containing CNPs with 8.9 % Cp showed 36 % lower stress when the thickness of the second a-C:H layer was similar to that of the first (154 nm). The deposited CNPs exhibited two size groups, with mean sizes of the small and large CNPs of 5 and 16 nm, respectively. Stress reduction was strongly correlated with the distance between large CNPs. The insertion of CNPs between a-C:H films affects the surface morphology of the second layer, and the stress decreases when the growth stage of the film starts transitioning from three-dimensional (3D) to two-dimensional (2D).

Enhancing membrane-based scanning force microscopy through an optical cavity

Enhancing membrane-based scanning force microscopy through an optical cavity

Hevea brasiliensis rubber particles' fluid interfaces reveal size impact on early coagulation steps

Natural rubber originates from the coagulation of rubber particles (RP) from Hevea brasiliensis latex. The size distribution of Hevea RP is bimodal with the presence of small rubber particles (SRP) and large rubber particles (LRP). This study aims at getting a better understanding of the early coagulation steps of Hevea RP taking into account the particle size. SRP and LRP were obtained by centrifugation of freshly tapped ammonia-free latex from RRIM600 clone. Size and zeta potential measurements showed that both RP fractions were efficiently separated and stable in basic buffer. SRP and LRP dispersions were placed in a Langmuir trough and RP were let to adsorb at the air-liquid interface to form interfacial films. Surface tension and ellipsometry indicate that the formation kinetics and the stabilization of the film at the air-liquid interface are faster for SRP than LRP. Moreover, the arrangement of RP at the interface differs between SRP and LRP, as shown by Brewster angle microscopy, atomic force microscopy and confocal laser scanning microscopy. First, the RP membrane and cis-1,4-polyisoprene core spread at the air-liquid interface before clustering. Then, while the SRP fuse, the LRP keep their structure in individual particles in floating aggregate. The role of the non-isoprene molecules on the different organization of SRP and LRP films is discussed, the one of the two major RP proteins, SRPP1 (Small Rubber Particle Protein) and Rubber Elongation Factor (REF1) in the early coagulation steps.

High-Speed Three-Dimensional Scanning Force Microscopy Visualization of Subnanoscale Hydration Structures on Dissolving Calcite Step Edges.

Hydration at solid-liquid interfaces plays an essential role in a wide range of phenomena in biology and in materials and Earth sciences. However, the atomic-scale dynamics of hydration have remained elusive because of difficulties associated with their direct visualization. In this work, a high-speed three-dimensional (3D) scanning force microscopy technique that produces 3D images of solid-liquid interfaces with subnanoscale resolution at a rate of 1.6 s per 3D image was developed. Using this technique, direct 3D images of moving step edges were acquired during calcite dissolution in water, and hydration structures on transition regions were visualized. A Ca(OH)2 monolayer was found to form along the step edge as an intermediate state during dissolution. This imaging process also showed that hydration layers extended from the upper terraces to the transition regions to stabilize adsorbed Ca(OH)2. This technique provides information that cannot be obtained via conventional 1D/2D measurement methods.

Microbicidal Polymer Nanoparticles Containing Clotrimazole for Treatment of Vulvovaginal Candidiasis

Vulvovaginal candidiasis (VVC) alters the innate cervicovaginal immunity, which provides an important barrier against viruses and other infections. The incidence of this disease has not decreased in the last 30 years, so effective treatments are still needed. Nanoparticles (NPs) of cellulose acetate phthalate (CAP) and clotrimazole (CLZ) were prepared by the emulsification-diffusion method. NPs were characterized using dynamic light scattering, atomic force microscopy and differential scanning calorimetry; their release profile was determined by the dialysis bag technique and mucoadhesion was evaluated with the mucin-particle method. The growth inhibition study of Candida albicans was carried out using the plate counting technique. Finally, accelerated physical stability tests of NPs were carried out, both in water and in SVF. The CAP-CLZ NPs had an average diameter of 273.4 nm, a PDI of 0.284, smooth surfaces and spherical shapes. In vitro release of CLZ from the CAP NPs was categorized with the Weibull model as a matrix system in which initial release was rapid and subsequently sustained. The inhibition of C. albicans growth by the CAP-CLZ NPs was greater than that of free CLZ, and the CAP-only NPs had a microbicidal effect on C. albicans. The NPs showed poor mucoadhesiveness, which could lead to studies of their mucopenetration capacities. An accelerated physical stability test revealed the erosion of CAP in aqueous media. A nanoparticulate system was developed and provided sustained release of CLZ, and it combined an antifungal agent with a microbial polymer that exhibited antifungal activity against C. albicans.Graphical

Stability Enhancement by Hydrophobic Anchoring and a Cross-Linked Structure of a Phospholipid Copolymer Film for Medical Devices.

Surface modification using zwitterionic 2-methacryloyloxyethylphosphorylcholine (MPC) polymers is one of the most reasonable ways to prepare medical devices that can suppress undesired biological reactions such as blood coagulation. Usable MPC polymers are hydrophilic and water soluble, and their surface modification strategy involves exploiting the copolymer structures by adding physical or chemical bonding moieties. In this study, we developed copolymers composed of MPC, hydrophobic anchoring moiety, and chemical cross-linking unit to clarify the role of hydrophobic interactions in achieving biocompatible and long-term stable coatings. The four kinds of MPC copolymers with cross-linking units, such as 3-methacryloxypropyl trimethoxysilane (MPTMSi), and four different hydrophobic anchoring moieties, such as 3-(methacryloyloxy)propyltris(trimethylsiloxy)silane (MPTSSi) named as PMMMSi, n-butyl methacrylate (BMA) as PMBSi, 2-ethylhexyl methacrylate (EHMA) as PMESi, and lauryl methacrylate as PMLSi, were synthesized and coated on polydimethylsiloxane, polypropylene (PP), and polymethyl pentene. These copolymers were uniformly coated on the substrate materials PP and poly(methyl pentene) (PMP), to achieve hydrophilic and electrically neutral coatings. The results of the antibiofouling test showed that PMBSi repelled the adsorption of fluorescence-labeled bovine serum albumin the most, whereas PMLSi repelled it the least. Notably, all four copolymers suppressed platelet adhesion similarly. The variations in protein adsorption quantities among the four copolymer coatings were attributed to their distinct swelling behaviors in aqueous environments. Further investigations, including 3D scanning force microscopy and neutron reflectivity measurements, revealed that the PMLSi coating exhibited a higher water intake under aqueous conditions in comparison to the other coatings. Consequently, all copolymer coatings effectively prevented the invasion of platelets but the proteins penetrated the PMLSi network. Subsequently, the dynamic stability required to induce shear stress was evaluated using a circulation system. The results demonstrated that the PMMMSi and PMLSi coatings on PMP and PP exhibited exceptional platelet repellency and maintained high stability during circulation. This study highlights the potential of hydrophobic moieties to improve hemocompatibility and stability, offering potential applications in medical devices.

Synergic Effect of the Antimicrobial Peptide ToAP2 and Fluconazole on Candida albicans Biofilms.

Candida albicans is one of the agents of invasive candidiasis, a life-threatening disease strongly associated with hospitalization, particularly among patients in intensive care units with central venous catheters. This study aimed to evaluate the synergistic activity of the antifungal peptide ToAP2 combined with fluconazole against C. albicans biofilms grown on various materials. We tested combinations of different concentrations of the peptide ToAP2 with fluconazole on C. albicans biofilms. These biofilms were generated on 96-well plates, intravenous catheters, and infusion tubes in RPMI medium at two maturation stages. Scanning electron microscopy and atomic force microscopy were employed to assess the biofilm structure. We also evaluated the expression of genes previously proven to be involved in C. albicans biofilm formation in planktonic and biofilm cells after treatment with the peptide ToAP2 using qPCR. ToAP2 demonstrated a synergistic effect with fluconazole at concentrations up to 25 µM during both the early and mature stages of biofilm formation in 96-well plates and on medical devices. Combinations of 50, 25, and 12.5 µM of ToAP2 with 52 µM of fluconazole significantly reduced the biofilm viability compared to individual treatments and untreated controls. These results were supported by substantial structural changes in the biofilms observed through both scanning and atomic force microscopy. The gene expression analysis of C. albicans cells treated with 25 µM of ToAP2 revealed a decrease in the expression of genes associated with membrane synthesis, along with an increase in the expression of genes involved in efflux pumps, adhesins, and filamentation. Our results highlight the efficacy of the combined ToAP2 and fluconazole treatment against C. albicans biofilms. This combination not only shows therapeutic potential but also suggests its utility in developing preventive biofilm tools for intravenous catheters.

A novel refractive index based-fiber optic sensor for milk adulteration detection

Milk adulteration poses a significant risk to public health and consumer trust, compromising its nutritional value. To address this, we've developed an optical fiber-based sensor using a Lossy Mode Resonance (LMR) approach. Antimony Oxide (Sb2O3) serves as the sensing layer, deposited onto the optical fiber's unclad core using Radio Frequency Magnetron sputtering. The sensing layer underwent comprehensive characterization, including X-Ray diffraction (XRD), UV–Vis spectroscopy, Ellipsometer, Atomic Force Microscopy (AFM), EDAX, and Field Emission Scanning Microscopy (FESEM). The sensor was tested for formaldehyde and water adulteration across normal milk type 1, full-fat milk type 2, vendor milk type 3, and, with concentrations ranging from 0 % to 10 %. Observations included resonance wavelength shifts and sensing parameters such as sensor response, sensitivity, and repeatability. For Sb2O3-coated sensor probes, responses to formaldehyde and water adulteration for type 1 milk is 2.05 % and 2.22 %, type 2 milk is 2.17 % and 2.4 %, and type 3 milk is 1.90 % and 1.95 %. Sensitivity for Sb2O3-coated probe to formaldehyde are 2.2 nm/v% (type 1 milk),1.9 nm/v% (type 2 milk) and 1.5 nm/v% (type 3 milk). For water in milk, the sensitivities are 1.7 nm/v%, 1.5 nm/v%, and 1.2 nm/v%. Furthermore, a prototype sensor probe has been developed for continuous milk adulteration monitoring, interfaced with Arduino and Thing Speak.

Conversion of preferred crystalline orientation by annealing and its impacts on the structural, electronic, and optical properties of pulsed laser-deposited CdO thin films

The impact of annealing on the preferred crystalline orientation as well as the structural, electronic, and optical properties of pulsed laser-deposited 150 ± 3 nm thick cadmium oxide (CdO) films was studied. X-ray diffraction analysis revealed that the annealed CdO films have smaller crystallite sizes, as their molecules at the grain boundaries possessed enough kinetic energy to rearrange their preferred crystalline orientation between (111) and (200). The atomic force microscopy and field emission scanning electron microscopy analyses revealed an enhancement in the active surface area with optimized grain boundaries by annealing which facilitates gas adsorption/desorption. DC electrical conductivity depends on the annealing process and reveals two different conduction mechanisms. The direct optical energy gap was decreased from 3.41 eV to 2.76 eV by annealing at 473 K which is greater than the theoretical value, i.e. 2.2 eV, for bulk CdO. The findings agree with the Burstein-Moss effect as a result of the increased carrier concentration following the generation of numerous oxygen vacancy sites and Cd interstitials. However, mutual charge carrier-impurity interaction and charge carrier Columb interaction contributed to narrowing the band gap by increasing the annealing temperature. The enhanced values of Urbach energy, optical packing density, dispersion parameters, optical conductivity, dissipation factor, oscillator strength, and lattice dielectric constant supported the effectiveness of the annealing process on tailoring optoelectronic responses in the infrared region for the CdO thin films for use in optoelectronic devices. Moreover, the calculated linear optical susceptibility, and nonlinear constants (i.e. third-order optical susceptibility and nonlinear refractive index) were the highest for CdO films annealed at 473 K. The improved value of the figure of merit, solar material protection factor, and solar skin protection factor for the CdO films, annealed at 473 K supports its use in several photovoltaic applications, including solar cells.

Temperature dependence of the friction and wear behavior of pure tungsten

In this work, the friction and wear characteristics of rolled pure tungsten were investigated by using atomic force microscope (AFM) and field emission scanning electron microscope (SEM) with electron backscatter diffraction (EBSD) characterization techniques. A ductile to brittle transition (DBT) related frictional wear behaviors have been discovered. The results indicated that the coefficient of friction maintains an almost constant value of 0.45 at low temperatures (≤ 400 °C), whereas it consistently decreases at 600 °C due to the generation of a surface oxide. The wear rate varies with temperatures and reaches a maximum at 200 °C due to the transition of the tungsten matrix from brittleness to pseudoplasticity, which leads to severe adhesive wear and large mass loss. In addition, the evolution of sub-grains underneath the friction layer and Vickers microhardness were evaluated as well. This work provides insight into understanding the relationship between temperatures, microstructure and the frictional properties of tungsten materials, and thus provides guidance for improving frictional wear behaviors in tungsten materials.

Application of Recycled Ultrafiltration Membranes in an Aerobic Membrane Bioreactor (aMBR): A Validation Study.

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4-0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) and commercial UF membrane (molecular weight cut-off (MWCO) 150 kDa) (c-150 kDa); (ii) r-UF membrane modified by dip-coating using catechol (CA) and polyethyleneimine (PEI) (mr-UF) and c-20 kDa membrane. Permeability, fouling behavior, and permeate quality were evaluated. Extensive membrane characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and confocal laser scanning microscopy (CLSM). Permeate quality for r-UF and mr-UF membranes was excellent and comparable to that obtained using commercial membranes under similar conditions. Additionally, r-UF and mr-UF membranes presented a steadier performance time. Additionally, r-UF membrane demonstrated less tendency to be fouled (Rf, m-1) r-UF 7.92 ± 0.57 × 1012; mr-UF 9.90 ± 0.14 × 1012, c-150 kDa 1.56 ± 0.07 × 1013 and c-20 kDa 1.25 ± 0.50 × 1013. The r-UF membrane showed an excellent antibiofouling character. Therefore, r-UF membranes can be successfully implemented for wastewater treatment in aMBR, being a sustainable and cost-effective alternative to commercial membranes that can contribute to overcome membrane fouling and membrane replacement issues.

Vibrations of viscoelastic FG porous graphene-platelets reinforced doubly-curved shells via experimental characterisation of graphene platelets

This work explores the vibrations of viscoelastic functionally-graded (FG) porous graphene-platelets reinforced doubly-curved shallow shells via experimental characterisations of graphene platelets. In particular, the effects of ultrasonication time of graphene platelets, on the vibrations of graphene-platelets reinforced shells, are studied. This is of interest because graphene platelets are often ultrasonicated in solvents to achieve better dispersions during the fabrication of graphene-platelets/epoxy composite structures. In this study, geometric characteristics of the graphene platelets under different sonication times are quantitatively and qualitatively analysed through experimental characterisation techniques, including a laser diffraction particle size analyser, a scanning electron microscopy (SEM), and a scanning force microscopy (SFM). The geometric characteristics of graphene platelets are considered in the effective material properties using a micromechanics model of Halpin-Tsai. Different FG distributions of graphene platelets and closed-cell porosity are modelled. The Kelvin-Voigt viscoelastic model is used to consider the internal friction-induced energy dissipation for the polymeric composite shell. Hamilton’s variational principle and an assumed mode method are used to derive and solve the equations of motion, respectively, for the vibrations of the doubly-curved shells. The effects of graphene platelets sonication time, in combination with the effects of graphene platelets weight fraction, porosity coefficient, FG distributions, shell thickness ratio, and shell curvature radii, are scrutinised. The results show that increasing ultrasonication time reduces the shell’s out-of-plane dimensionless fundamental frequency as a result of the reduction in graphene platelets aspect ratio.

Depth resolution in piezoresponse force microscopy

Piezoresponse force microscopy (PFM) is one of the most widespread methods for investigating and visualizing ferroelectric domain structures down to the nanometer length scale. PFM makes use of the direct coupling of the piezoelectric response to the crystal lattice, and hence, it is most often applied to spatially map the three-dimensional (3D) near-surface domain distribution of any polar or ferroic sample. Nonetheless, since most samples investigated by PFM are at least semiconducting or fully insulating, the electric ac field emerging from the conductive scanning force microscopy (SFM) tip penetrates the sample and, hence, may also couple to polar features that are deeply buried into the bulk of the sample under investigation. Thus, in the work presented here, we experimentally and theoretically explore the contrast and depth resolution capabilities of PFM, by analyzing the dependence of several key parameters. These key parameters include the depth of the buried feature, i.e., here a domain wall (DW), as well as PFM-relevant technical parameters such as the tip radius, the PFM drive voltage and frequency, and the signal-to-noise ratio. The theoretical predictions are experimentally verified using x-cut periodically poled lithium niobate single crystals that are specially prepared into wedge-shaped samples, in order to allow the buried feature, here the DW, to be “positioned” at any depth into the bulk. This inspection essentially contributes to the fundamental understanding in PFM contrast analysis and to the reconstruction of 3D domain structures down to a 1 μm-penetration depth into the sample.

Synthesis and characterization of a new eco-friendly dopamine derivative schiff base as an effective corrosion inhibitor for mild steel in acidic environment

The natural corrosion inhibitor behaviour of a newly synthesized dopamine derivative Schiff base (4-DBAB) has been inspected on mild steel in aggressive 1 M HCl using linear polarization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques. The Schiff base was synthesized by eco-friendly pathway. Characterization of the synthesized new non-toxic inhibitor was performed using FT-IR and 1H-NMR spectroscopy techniques. The anti-corrosive efficiencies at optimum concentration of 4-DBAB inhibitor was 87.4% after 1 h and 98.4% after 120 h by impedance technique in acidic solution. The potential of zero charge of mild steel was also determined to elucidate the inhibition mechanism in the presence of the highest 4-DBAB solution. The atomic force microscopy and field emission scanning electron microscopy researches performed on surface morphology to provide additional support on the interaction between the mild steel surface and 4-DBAB molecules. Adsorption behaviour of the inhibitor was also studied at different durations by experimental inhibition results and showed the Langmuir isotherm involving chemisorption. Highlights A new dopamine-derived Schiff base (4-DBAB) with natural and environmentally friendly corrosion inhibition properties was synthesized. (Synthesis of eco-friendly compound). 4-DBAB demonstrated a high anti-corrosive efficiency after 120 hours in aggressive 1M HCl, as determined by impedance technique. (Exceptional corrosion inhibition). The determination of the potential of zero charge of mild steel provided insights into the inhibition mechanism in the presence of the highest 4-DBAB solution. (Mechanism elucidation). AFM and FE-SEM studies on surface morphology supported the interaction between the mild steel and 4-DBAB molecules, affirming its corrosion inhibition properties. (Surface interaction analysis).