Scanning Atomic Force Microscopy Research Articles

Impact of Cd/Sn molar ratio and annealing temperature on the properties of spin coated Cd2SnO4 thin films

We have synthesized and characterized spin coated Cd2SnO4 (CTO) thin films in the present work by varying the Cd/Sn = 2,3,4, and 5 M ratios, and 450 and 500 οC annealing temperatures. The structural studies were done using X-ray diffraction (XRD) and the results show that all the films exhibit a polycrystalline nature with (311) plane preferred orientation corresponding to Cd2SnO4 inverse spinel cubic phase. The morphological studies were done using an atomic force microscope (AFM) and field emission scanning electron microscope (FESEM). The thin films obtained with a roughness of 3–40 nm, and uniformly distributed grains without cracks are evident from the micrographs. The elemental analyses were carried out by employing EDAX and XPS techniques. The optical properties such as transmittance, bandgap, and refractive index are obtained using UV–Vis spectroscopy. The films were showing high transmittance (75–93 %) in the visible region. The band gaps of the investigated samples are found to be in the range of 3.4 eV–3.7 eV. The refractive index of CTO thin films in the 350–1000 nm wavelength range is around 1.7 to 1.9. The electrical properties show better results for the films annealed at 500 οC. The mobility values obtained are in the range of 0.6–4 cm2/Vs for different Cd/Sn ratio samples. The carrier concentration of CTO thin films is in the range of 4 × 1018 to 28 × 1018 cm−3. The presence of defects such as oxygen vacancy, Cd/Sn interstitial, and self-doping of Cd and Sn results in increased carrier concentration at higher Cd/Sn ratios. Besides, the wettability analysis was performed by contact angle measurements, which infer a hydrophobic to hydrophilic conversion in terms of the surface roughness of CTO thin films. From optoelectrical results, it is evident that the films exhibited better optical and electrical properties and are suitable for optoelectronic devices.

Low-cost photocatalytic membrane modified with green heterojunction TiO2/ZnO nanoparticles prepared from waste

The combination of photocatalysis and membrane procedures represents a promising approach for water treatment. This study utilized green synthesis methods to produce TiO2 nanoparticles (NPs) using Pomegranate extract and ZnO nanoparticles using Tangerine extract. These nanoparticles were then incorporated into a polyvinyl chloride (PVC) nanocomposite photocatalytic membrane. Different devices were used to examine the properties of nanocomposite membranes. The prepared membranes' morphology was examined using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). The hydrophilicity of the membrane surface was assessed through the measurement of contact angle, while the crystal structure and chemical bonding were analyzed using Raman and Fourier transform infrared spectroscopy (FT-IR). The study also encompassed an examination of the mechanical properties. The hydrophilicity of the modified membrane exhibited a significant improvement. Additionally, there was an observed increase in both the pure water flux and rejection values. The photocatalytic activity of the membrane was found to be enhanced when exposed to sunlight as compared to when kept in the dark. The TiO2/ZnO nanocomposites membrane exhibited the highest level of photocatalytic degradation, achieving a rejection rate of 98.7% compared to the unmodified membrane. Therefore, it was determined that the TiO2/ZnO nanocomposites membrane exhibited superior performance to the other membranes assessed. The potential utility of our research lies in its application within the water treatment industry, specifically as an effective technique for modifying PVC membranes.

Corrosion mitigation of mild steel in 1 M HCl acid using an expired drug: An experimental approach

The research undertaken highlights the effectiveness of pharmaceutical drug Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione) (PB) as inhibitor to mitigate corrosion of mild steel (MS) in 1 M HCl. Corrosion studies were done by electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in the absence and presence of the Phenobarbitone (PB) drug. Kinetic parameters were calculated by studying the corrosion rate at different temperatures. Results were fitted into suitable adsorption isotherm and from the adsorption data thermodynamic parameters were computed and discussed in detail. Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), and atomic force microscopy (AFM) techniques. The nature of the protective layer formed over the metal was studied by measuring the contact angle (CA), which demonstrated the formation of the adsorbed inhibitor layer. Inhibition efficiency increased with increase in concentration of inhibitor and with increase in temperature. For the addition of 0.04 gL-1, the maximum corrosion inhibition efficiency of 78.3 % was achieved at 313 K. Inhibitor acted as a mixed inhibitor with more control over the anodic reaction. Increase in efficiency with increase in temperature suggested the possibility of chemical adsorption. Inhibitor obeyed Langmuir adsorption isotherm, supporting chemical adsorption. Surface morphology clearly demonstrated the formation of barrier film on the surface of metal which prevented further dissolution of metal thereby decreasing the corrosion rate.

Discontinuous Dissolution Mechanism of Olivine Deduced from a Topography Observation Method.

Olivine dissolution plays an important role in environmental science and technology, from controlling global element circulation to carbon capture for climate change mitigation. Most studies have been focused on investigating its dissolution rates by monitoring chemical effluent changes under various conditions. However, only by observation of surface reactivity can we unravel the actual mechanism (s) of dissolution. Here, we studied the dissolution of an olivine (010) plane in a flow-through reaction cell with an acidic solution, a surface-controlled regime, and far-from-equilibrium conditions. Direct mineral surface topography measurements using vertical scanning interferometry and atomic force microscopy allowed for quantitative analyses of the spatial and temporal changes in the dissolution rate. The (010) plane dissolved discontinuously in time for different surface sites, resulting in a heterogeneously distributed rate map. Pits with different depths showed opposite dissolution rate distributions from the dislocation center to further out from the etch pit. Based on the step-wave model, we propose a mechanism of dissolution that is governed by the competition between Gibbs free energy of the dissolution process, ΔG, and the critical free energy of the opening of etch pits, i.e., ΔGcrit. The migration of step waves, the distribution of surface defects, the strain field of etch pits, and other dynamic elements, resulting in the instantaneous change of ΔGcrit on the surface, are important factors leading to the discontinuous dissolution of crystal materials. This discontinuous dissolution provides new insight into the guidance of crystalline mineral applications and the prediction of material properties regarding mineral dissolution variation.

In vitro antioxidant activity of the polysaccharide from Auricularia auricula and its structural characterisation

A new polysaccharide (AAP) was extracted from Auricularia auricula by water extraction and alcohol precipitation. The antioxidant activity in vitro showed that AAP had a good scavenging effect on ABTS free radicals. Then AAP was purified by DEAE-52 ion exchange chromatography to obtain the purified component pAAP. The structure analysis showed that the molecular weight (Mw) of pAAP was 96.768 kDa, which was composed of rhamnose (Rha), arabinose (Ara), fucose (Fuc), xylose (Xyl), mannose (Man), glucose (Glu) and galactose (Gal), with the ratio of 0.1:0.157:0.33:2.797:2.881:2.988:0.587, and contained α-pyranose configuration and β-pyranose configuration. Field emission scanning electron microscopy and atomic force microscopy revealed the special conformation of pAAP in the ring and chain shape.

Effect of substrate temperature and annealing on the growth of TiO2‐x thin films deposited by using DC‐magnetron sputtering technique

In this study, the effect of annealing on the structural, surface morphology and chemical structure of titanium suboxide (TiO2‐x) thin films has been investigated. TiO2‐x films had been grown on Si substrates by DC‐magnetron sputtering with different sputter powers (75 and 100 W) at room temperature (RT) and 200°C substrate temperature (ST). The films were subsequently annealed for 1 h at 300, 400 and 500°C in vacuum. The impact of ST, post‐annealing and sputter power on crystallinity, surface morphology and chemical state of the films were studied. Grazing incidence X‐ray diffraction (GIXRD) data revealed that the films were amorphous or exhibited a very low crystalline structure while deposited at RT and even after annealing. Moreover, the films showed crystallinity while deposited at ST and exhibited an anatase‐rutile (A‐R) mix phase from anatase (A) annealed at 300°C (75 W at ST). X‐ray reflectivity (XRR) data showed that the mass density of the films increased with the annealing temperature. Images obtained using atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) revealed that post‐annealing increased the surface roughness of the films. X‐ray photoelectron spectroscopy (XPS) analysis indicated the films were sub stoichiometric. It was also indicated that Ti was in the form of Ti4+ and Ti3+ states in all films, and the proportion of Ti4+ slightly increased after post‐annealing at 500°C. The findings showed that post‐annealing, ST and sputtering power can all affect the growth of TiO2‐x films.

Solid-State Dewetting of Thin Au Films for Surface Functionalization of Biomedical Implants.

Biomaterial-centered infections of orthopedic implants remain a significant burden in the healthcare system due to sedentary lifestyles and an aging population. One approach to combat infections and improve implant osteointegration is functionalizing the implant surface with anti-infective and osteoinductive agents. In this framework, Au nanoparticles are produced on the surface of Ti-6Al-4V medical alloy by solid-state dewetting of 5 nm Au film and used as the substrate for the conjugation of a model antibiotic vancomycin via a mono-thiolated poly(ethylene glycol) linker. Produced Au nanoparticles on Ti-6Al-4V surface are equiaxed with a mean diameter 19.8 ± 7.2 nm, which is shown by high-resolution scanning electron microscopy and atomic force microscopy. The conjugation of the antibiotic vancomycin, 18.8 ± 1.3 nm-thick film, is confirmed by high resolution-scanning transmission electron microscopy and X-ray photoelectron spectroscopy. Overall, showing a link between the solid-state dewetting process and surface functionalization, we demonstrate a novel, simple, and versatile method for functionalization of implant surfaces.

Development and evaluation of a protease inhibitor antiretroviral drug-loaded carbon nanotube delivery system for enhanced efficacy in HIV treatment

The primary objective of this study was to enhance the effectiveness of the protease inhibitor antiretroviral drug by designing a novel delivery system using carboxylated multiwalled carbon nanotubes (COOH-MWCNTs). To achieve this, Fosamprenavir calcium (FPV), a prodrug of amprenavir known for inhibiting the proteolytic cleavage of immature virions, was selected as the protease inhibitor antiretroviral drug, and loaded onto COOH-MWCNTs using a direct loading method. The structural specificity of the drug-loaded MWCNTs, the percent entrapment efficiency, and in vitro drug release were rigorously evaluated for the developed formulation, referred to as FPV-MWCNT. Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and atomic force microscopy (AFM) techniques were employed to confirm the structural integrity and specificity of the FPV-MWCNT formulation. The results demonstrated a remarkable entrapment efficiency of 79.57 ± 0.4 %, indicating the successful loading of FPV onto COOH-MWCNTs. FE-SEM and AFM analyses further confirmed the well-dispersed and elongated structure of the FPV-MWCNT formulation, without any signs of fracture, ensuring the stability and integrity of the drug delivery system. Moreover, particle size analysis revealed an average size of 290.1 nm, firmly establishing the nanoscale range of the formulation, with a zeta potential of 0.230 mV, signifying the system's colloidal stability. In vitro drug release studies conducted in methanolic phosphate buffer saline (PBS) at pH 7.4 and methanolic acetate buffer at pH 5 demonstrated sustained drug release from the FPV-MWCNT formulation. Over a period of 96 h, the formulation exhibited a cumulative drug release of 91.43 ± 2.3 %, showcasing the controlled and sustained release profile. Furthermore, hemolysis studies indicated a notable reduction in the toxicity of both FPV and MWCNT upon conjugation, although the percent hemolysis increased with higher concentrations, suggesting the need for careful consideration of dosage levels.In conclusion, the findings from this study underscore the potential of the FPV-MWCNT formulation as an effective and promising drug-conjugated system for delivering antiretroviral drugs. The successful encapsulation, sustained drug release, and reduced toxicity make FPV-MWCNT a compelling candidate for enhancing the therapeutic efficacy of protease inhibitor antiretroviral drugs in the treatment of HIV. The developed delivery system holds great promise for future advancements in HIV treatment and paves the way for further research and development in the field of drug delivery utilizing carbon nanotube-based systems.

A comprehensive study from the micro- to the nanometric scale: Evaluation of chilling injury in tomato fruit (Solanum lycopersicum)

Tomato fruit is susceptible to chilling injury (CI) during its postharvest handling at low temperature. The symptoms caused by this physiological disorder have been commonly evaluated by visual inspection at a macro-observation scale on fruit surface; however, the structure at deeper scales is also affected by CI. This work aimed to propose a descriptive model of the CI development in tomato tissue under the micro-scale, micro-nano-scale and nano-scale approaches using fractal analysis. For that, quality and fractal parameters were determined. In this sense, light microscopy, Environmental Scanning Electron Microscopy (ESEM) and Atomic Force Microscopy (AFM) were applied to analyse micro-, micro-nano- and nano-scales, respectively. Results showed that the morphology of tomato tissue at the micro-scale level was properly described by the multifractal behaviour. Also, generalised fractal dimension (Dq=0) and texture fractal dimension (FD) of CI-damaged pericarp and cuticle were higher (1.659, 1.601 and 1.746, respectively) in comparison to non-chilled samples (1.606, 1.578 and 1.644, respectively); however, FD was unsuitable to detect morphological changes at the nano-scale. On the other hand, lacunarity represented an appropriate fractal parameter to detect CI symptoms at the nano-scale due to differences observed between damaged and regular ripe tissue (0.044 and 0.025, respectively). The proposed multi-scale approach could improve the understanding of CI as a complex disorder to the development of novel techniques to avoid this postharvest issue at different observation scales.

The effect of cathode arc current on the structures of TiN thin films prepared by cathodic arc deposition

The titanium nitride (TiN) thin films were fabricated by the cathodic arc deposition technique. The effect of titanium cathode arc current on structural, chemical, and morphological properties of thin films was investigated by X-ray diffraction(XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and atomic force microscopy (AFM), respectively. The XRD results showed titanium nitride formation with a fcc phase structure for all samples and the preferred orientation changed from (111) to (200) plane with increasing the cathode arc current from 50 to 60 A. The crystallized sizes of the thin films increased as increasing the cathode arc current. In addition, the relationship between the size of the microdroplets on the coating surfaces and the arc current was examined.

Correlation of sputtering power with microstructure and ionic conductivity in lithium aluminum oxide thin films prepared by reactive co-sputtering

Li–Al–O thin films synthesized via the reactive magnetron co-sputtering have the potential to act as solid-state electrolytes in micro-batteries. In this paper, the constant RF power (155 W) and variable DC power (20–50 W) were applied to lithium (Li) and aluminum (Al) metal targets, respectively, in Ar/O2 atmosphere to produce films with adequate ionic conductivity. The influence of DC sputtering power on the composition, microstructure, band gap energy, ionic conductivity, and dielectric loss of films were studied in detail. X-ray photoelectron spectroscopy (XPS) showed a shift of the Li 1s peak towards higher binding energy with increasing DC power. X-ray diffraction (XRD) spectra confirmed the amorphous state for all as-deposited films, while the post-annealed films at 950 °C contain the γ-LiAlO2 phase. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) images revealed that the increasing DC power had a significant impact on the film morphology, enlarging grain size and increasing surface roughness. Energy dispersive X-ray (EDX) spectroscopy showed that increasing the DC power increased the Al content. The optical properties were examined by ultraviolet–visible (UV–vis) spectroscopy, which indicated that increasing the Al content led to a blue shift of the absorption edge and an increase in the band gap energy (5.40–5.68 eV). Increasing the DC power resulted in an improvement of room-temperature conductivity by two orders of magnitude (∼2.85 × 10−9 S cm−1) and a decrease in the activation energy from 0.54 eV to 0.32 eV. These results suggest that composition and microstructure significantly affect the ionic transport in co-sputtered Li–Al–O films.

Improving the mechanical, thermal and surface properties of polyaspartic ester bio-based polyurea coatings by incorporating silica and titania

Polyaspartic ester polyurea coatings are known for their eco-friendly properties due to the absence of VOCs and free isocyanates. While these coatings offer many advantages to the industry, achieving durability often requires the use of trimers with high NCO content. In such cases, applicators face challenges due to their notably short pot life. Furthermore, the second component used is a petroleum-based polyisocyanate, which limits its classification as a sustainable material. In this study, bio-based polyisocyanates were employed in polyaspartic coatings for the first time, thereby positioning them as sustainable alternatives without compromising their conventional properties. Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance Spectroscopy (13C and 1H) were utilized to characterize the structure of polyaspartic ester coatings derived from biobased polyisocyanates along with solvent-free and catalyst-free PAEs. It was determined that the coating formulation had a convenient working time at room temperature. Pendulum hardness and contact angle measurements indicated that hard coatings with hydrophobicity were obtained with the addition of SiO2 and TiO2 particles without reducing the working time. The results revealed a notable 37% increase in tensile strength with the addition of 3 wt% silica compared to the base coating, and a remarkable 43 wt% increase when the coating obtained an equal proportion of titanium and silica at the same concentration. Additionally, Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) studies revealed that the composite coatings comprising titanium and silica particles exhibited higher glass transition temperatures and residual char yields compared to the base coating. The morphology and surface roughness of the coatings were characterized using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM).

Solution-processed CsPbBr3 perovskite LEDs using blended-polymer additives for nearly 100% surface coverage

The all-inorganic perovskite material (CsPbBr3) is a promising light-emitting material due to its narrow color spectrum, wet solution processability, and cost-effectiveness. Despite such advantages, pinholes, poor surface coverage, and stability issues limit widespread applications of perovskite light-emitting devices (PeLEDs) in solid-state lighting applications. The performance of PeLEDs depends strongly on the morphological characteristics of the perovskite layer, with low surface coverage and surface roughness observed to lead to higher current leakage and lower current efficiency. We find that perovskite thin films blended with polymers to form composite layers effectively enhance the thin film’s surface coverage and uniformity, improving performance. We report CsPbBr3 PeLEDs with dual polymer additives, with a 12.1% reduction in the turn-on voltage (Von), a 97.21% reduction in leakage current density, a 200%+ enhancement in maximum brightness, and a 700% increase in power efficiency compared to a control CsPbBr3 device. To study the likely source of these enhancements, we have conducted a comparative film analysis of test and control devices using field-emission scanning electron microscopy and atomic force microscopy. A reduced crystal grain size (∼204nm to ∼101nm) and a nearly 100% (99.79%) surface coverage (compared to 79.53% found for control devices) suggest that the improved overall morphology and surface coverage likely play a significant role in the improved performance. Further, a reduction in surface roughness (∼45%) and the formation of a nearly pinhole-free film are observed to increase yield by 20%.

Research on Tip Characterization Techniques Based on Two-Dimensional Self-Traceable Nano-Gratings

The characterization of scanning tip morphology is crucial for accurate linewidth measurements. Conventional rectangular characterizers are affected by lateral distortion caused by the nonlinearities in AFM scanning, leading to errors between the actual characterization results and the true values. In this study, we innovatively developed self-traceable two-dimensional nano-gratings using chromium atomic deposition technology and extreme ultraviolet interference lithography. We used this structure as a characterizer for conducting scanning tip characterizations.This paper analyzed the periodic stability of the grating sample during scanning and corrected the lateral distortion of atomic force microscopy (AFM) at scan scales of 0.5 µm and 1 µm based on its self-traceable characteristics. Additionally, we extracted the angle information of the scanning tip in the X direction and Y direction within a scan scale of 0.5 µm. The results demonstrate that the two-dimensional grating sample exhibited excellent periodic stability during scanning. The characterization errors for the tip’s X direction and Y direction angles are within ±2°, showing high consistency. This study highlights that self-traceable two-dimensional grating samples have the capability for in situ bidirectional characterization of tip information, providing a creative solution for the development of new-style tip characterizers.

Experimental and ab initio studies of the structural and optoelectronic properties of hexagonal wurtzite ZnO1-xSx alloys

The structural and optoelectronic properties of ZnO1-xSx alloys were investigated experimentally as well as theoretically. The ZnO1-xSx alloy thin films at different S concentrations (0.0 < x < 1.0) were deposited on quartz substrates by radiofrequency magnetron sputtering. The alloy composition was monitored with the help of optical emission spectroscopy. The ab initio density functional theory (DFT) based calculations were performed for the hexagonal wurtzite ZnO1-xSx system with the S compositions of x = 0.0, 0.0625, 0.125, 0.25, 0.5, 0.75, 0.875, 0.9375 and 1.0. The X-ray diffraction (XRD) and Raman spectroscopy measurements suggest the hexagonal wurtzite phase for the entire composition range. The films exhibit good crystalline quality with preferential growth along the c-axis. The linear change in the lattice parameter (c) was observed both from XRD analysis and DFT based calculations. The X-ray photoelectron spectroscopy confirms the anionic substitution of oxygen (O2−) and sulphur (S2−) in the hexagonal wurtzite lattice. Field emission scanning electron microscopy and atomic force microscopy were used to study the surface morphology. The optical properties were evaluated through transmittance spectroscopy and spectroscopic ellipsometry. The density of state calculations shows the forbidden region which confirms the semiconducting nature for all the alloy compositions. The energy band gap obtained from the respective Tauc's plots was found to vary from 2.9 to 3.6 eV with a bowing parameter of 3.2 eV. The same trend was observed in the calculated electronic band structures through DFT. The optical constants were evaluated from spectroscopic ellipsometry and the corresponding band gap values were compared with the values obtained from optical transmittance.

Kinetic Analysis of Oxygen Evolution on Spin-Coated Thin-Film Electrodes via Electrochemical Impedance Spectroscopy

Sustainable and renewable energy technologies have attracted significant attention for reducing greenhouse emissions in the shift from fossil fuels. The production of green hydrogen from water electrolysis is considered an environmentally friendly strategy for a decarbonized economy. We examine the activities of the hydrogen and oxygen evolution reactions (HER and OER) using spin-coated thin-film electrodes with Pt/C and IrO2 nano-electrocatalysts under acidic conditions. The nano-electrocatalysts are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The electrocatalytic activities of nanoscale Pt/C and IrO2 are close to those of commercial Pt/C and superior to commercial IrO2, resulting in improved overall water splitting performance. Furthermore, the OER kinetics analysis using the IrO2 electrode is conducted using EIS measurements with distribution of relaxation time (DRT) analysis, resulting in a comparable exchange current density to that from the Tafel slope method (6.7 × 10−2 mA/cm2 versus 5.1 × 10−2 mA/cm2), demonstrating the validity of the kinetics analysis. This work provides a general strategy for preparing novel and highly active OER electrode materials for water electrolysis.

Polybenzopyrrole/nano-alumina composite blend with zirconium silicate reinforced epoxy as protective coating to subside corrosion of carbon steel within a dilute NaCl solution

The present work inspects the corrosion retardation of carbon steel by zirconium silicate reinforced epoxy blended with fabricated (PB/AN) polybenzopyrrole/nano-alumina composite, termed as PB/AN@ZE coating. Nano-alumina (AN), polymer polybenzopyrrole (PB), and polymer nanocomposite (PB/AN) were conveniently synthesized and their structural, thermal and morphological information were confirmed through Fourier transform infrared spectroscopy, X-ray diffraction, Thermogravimetric analysis, Atomic Force Microscopy and Field Emission Scanning Electron Microscopy. The molecular dynamics computation data evidence that the designed composite PB/AN is highly stable and found to have the interaction energy of 67.63 eV. Anti-wettability behaviour of the formulated coating was examined using Contact-angle Goniometer. The corrosion-resistant behaviour with different weight% loading of PB/AN in the zirconium silicate reinforced epoxy coating on low-carbon steel was examined in 3.5 % NaCl by using EIS or Electrochemical Impedance Spectroscopy and PDP or Potentiodynamic polarisation studies. The EIS and PDP results of 0.25% PB/AN@ZE coating indicated the excellent barrier to control the corrosion kinetics with high protection efficiency of 97.14 % even after 24 days immersion in NaCl solution and damage induced coating (kept immersed for 24 h in NaCl) was evidenced with a high impedance value of 1.48 × 109 Ω.cm2.

Toward conformational identification of molecules in 2D and 3D self-assemblies on surfaces

The design of supramolecular networks based on organic molecules deposited on surfaces, is highly attractive for various applications. One of the remaining challenges is the expansion of monolayers to well-ordered multilayers in order to enhance the functionality and complexity of self-assemblies. In this study, we present an assessment of molecular conformation from 2D to 3D supramolecular networks adsorbed onto a HOPG surface under ambient conditions utilizing a combination of scanning probe microscopies and atomic force microscopy- infrared (AFM-IR). We have observed that the infrared (IR) spectra of the designed molecules vary from layer to layer due to the modifications in the dihedral angle between the C=O group and the neighboring phenyl ring, especially in the case of a 3D supramolecular network consisting of multiple layers of molecules.

Recycled carbon fiber potential for reuse in carbon fiber/PA6 composite parts

Pyrolysis reclaiming is the most promising process to treat high volumes of composite waste with an advantageous carbon footprint. This paper aims to compare pyrolysis reclaimed carbon fibers (RCF) to virgin sized fibers (VF) and de-sized fibers (VFT) in their capability to bond to a polyamide 6 matrix. Micromechanical tensile testing of single fiber samples of the three fiber types was conducted. A minor reduction in tensile strength and an unchanged elastic modulus of the RCF compared to VF was observed. Scanning electron microscopy and atomic force microscopy scans were used to evaluate the morphology of the fibers. To evaluate the surface energy of the fibers, tensiometric testing was conducted. RCF showed a better adhesion capability compared to VFT through higher total surface energy. Moreover, X-ray spectrophotometry scans highlighted a higher proportion of functional groups at the RCF surface compared to VFT. Finally, pull-out tests underlined a decrease of the interfacial shear strength of RCF and VFT by 35% compared to VF. Overall, this study’s results further the understanding of the impact of the pyrolysis reclaiming process on RCF mechanical and adhesion properties.

Mechanism and Quantitative Characterization of Wettability on Shale Surfaces: An Experimental Study Based on Atomic Force Microscopy (AFM)

Wettability, as a vital tool for analyzing and describing oil flow, plays a significant role in determining oil/water relative permeability, residual oil distribution, and on–site recovery efficiency. Although the contact angle method is widely used for measuring wetting behavior, it is susceptible to the effects of surface roughness, oil–water saturation, and the distribution of mixed wetting within the range of droplet sizes. Additionally, millimeter–scale droplets fail to accurately represent the wetting distribution and the influencing factors at the micro/nano–scale. Therefore, this study presents a comprehensive investigation of the microstructure and wettability of shale samples. The characterization of the samples was performed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques to gain insights into their microscopic features, surface properties, and wettability. Results demonstrate the following: (1) Quartz and clay minerals tended to exhibit rough surface topography, appearing as darker areas (DA) under scanning electron microscopy (SEM). It is worth noting that plagioclase minerals exhibited brighter areas (BA) under SEM. (2) An increase in the content of minerals such as quartz and clay minerals was observed to decrease the surface oil wetting behavior. In contrast, plagioclase feldspar exhibited an opposite trend. (3) Based on the adhesive forces of the samples towards oil or water, a wetting index, I, was established to evaluate the wettability of shale at a microscale. The dimensionless contact angle W, obtained by normalizing the contact angle measurement, also consistently indicated oil wetting behavior. (4) By comparing the differences between I and W, it was observed that surface roughness significantly affected the behavior of water droplets. The presence of roughness impeded the contact between the solid and liquid phases, thus influencing the accuracy of the wetting results. Organic matter also plays a significant role in influencing surface wettability, and its distribution within the shale samples can lead to localized variations in wettability.