Layers Of Stearic Acid Research Articles

Harnessing Quantum Capacitance in 2D Material/Molecular Layer Junctions for Novel Electronic Device Functionality.

Two-dimensional (2D) materials promise advances in electronic devices beyond Moore's scaling law through extended functionality, such as non-monotonic dependence of device parameters on input parameters. However, the robustness and performance of effects like negative differential resistance (NDR) and anti-ambipolar behavior have been limited in scale and robustness by relying on atomic defects and complex heterojunctions. In this paper, we introduce a novel device concept that utilizes the quantum capacitance of junctions between 2D materials and molecular layers. We realized a variable capacitance 2D molecular junction (vc2Dmj) diode through the scalable integration of graphene and single layers of stearic acid. The vc2Dmj exhibits NDR with a substantial peak-to-valley ratio even at room temperature and an active negative resistance region. The origin of this unique behavior was identified through thermoelectric measurements and ab initio calculations to be a hybridization effect between graphene and the molecular layer. The enhancement of device parameters through morphology optimization highlights the potential of our approach toward new functionalities that advance the landscape of future electronics.

Exploiting Hydrogen Interaction of Drugs and Biodegradable Scaffolds Using Nanoparticles Loaded Nanofibers

AbstractThis study presents a detailed investigation of the structural and surface modifications of Fe3O4 nanoparticles (NPs). Fourier Transform Infrared (FTIR) spectroscopy was utilized to analyze the distinct characteristic peaks of Fe3O4 NPs and their subsequent modifications with stearic acid (ST) layers. The FTIR analysis revealed characteristic peaks at 580 cm−1, and 441 cm−1, corresponding to the Fe‐O stretching vibrations of the bulk Fe3O4 NPs. The successful loading of stearic acid onto the Fe3O4 NPs was confirmed by the appearance of new peaks at 1413 cm−1 and 2908 cm−1, indicative of the asymmetric CH2 stretch and CH3 umbrella vibration modes of stearic acid. UV‐Vis spectroscopy further corroborated the efficient loading of tetracycline and ibuprofen onto Fe3O4/DST nanoparticles, as evidenced by changes in absorption spectra. N2 adsorption‐desorption isotherms illustrated the presence of micro and meso pores on the surface of Fe3O4 NPs, with alterations in pore volume and diameter post‐surface modification and drug loading. Evaluation of magnetic properties indicated a reduction in saturation magnetization after surface modification and drug loading, attributed to changes in homogeneity and surface moments. Differential Reflectance Spectroscopy (DRS) and Raman spectroscopy elucidated distinctive peaks and shifts in spectra, confirming the composition and structural changes in drug‐loaded nanofibers.

Mechanically Durable and Fluorine‐Free Ni–Cr Alloy‐Based Highly Hard Superhydrophobic Coating on Al Alloy

Superhydrophobic coatings, known for their water‐repelling properties, play an important role in corrosion resistance and self‐cleaning applications. This study addresses the pressing need for eco‐friendly and durable fabrication methods for metal surfaces, particularly Al alloys, recognized for their inherent low mechanical properties. The innovative electroplating technique successfully fabricates superhydrophobic coatings on Al alloy surfaces, incorporating a high‐hardness Ni–Cr alloys layer and a low‐surface‐energy stearic acid layer. The resulting coatings exhibit outstanding mechanical durability, corrosion resistance, and self‐cleaning capabilities. With a water contact angle of 165° and a corrosion protection efficiency of 98.6%, these coatings offer a substantial improvement over traditional methods. Moreover, the Leeb hardness of the coated alloy experiences an impressive 83% increase compared to pristine Al alloy. This universally applicable approach opens avenues for developing mechanically robust superhydrophobic coatings on various metallic substrates, with broad implications for engineering applications.

Evaluation of the hydrophobic and barrier properties of the polyurethane coatings covered by stearic acid thin layer

In this paper, a thin stearic acid (SA) film was deposited onto the polyurethane (PU) coatings with different concentrations of stearic acid in the ethanol (1 wt.%, 2 wt.% and 3 wt.%) by centrifuged technique. Fourier transform infrared spectra (FTIR) and water contact angle (WCA) method were performed to characterize and evaluate the hydrophobic layer formed on the surface of the samples. Then, the barrier property of the PU/SA was assessed by using electrochemical impedance spectroscopy (EIS) and accelerated salt spray test method. The results show that the presence of the stearic acid layer was effective for both hydrophobic and barrier properties, especially the samples prepared with 3 wt.% stearic acid. This work landmarks the need for improving the protection ability of polyurethane coatings for a metallic substrate.

Calcite Surfaces Modified with Carboxylic Acids (C2 to C18): Layer Organization, Wettability, Stability, and Molecular Structural Properties.

A fundamental understanding of the interactions between mineral surfaces and amphiphilic surface modification agents is needed for better control over the production and uses of mineral fillers. Here, we controlled the carboxylic acid layer formation conditions on calcite surfaces with high precision via vapor deposition. The properties of the resulting carboxylic acid layers were analyzed using surface-sensitive techniques, such as atomic force microscopy (AFM), contact angle measurements, angle resolved X-ray photoelectron spectroscopy (XPS), and vibrational sum-frequency spectroscopy. A low wettability was achieved with long hydrocarbon chain carboxylic acids such as stearic acid. The stearic acid layer formed by vapor deposition is initially patchy, but with increasing vapor exposure time, the patches grow and condense into a homogeneous layer with a thickness close to that expected for a monolayer as evaluated by AFM and XPS. The build-up process of the layer occurs more rapidly at higher temperatures due to the higher vapor pressure. The stability of the deposited fatty acid layer in the presence of a water droplet increases with the chain length and packing density in the adsorbed layer. Vibrational sum frequency spectroscopy data demonstrate that the stearic acid monolayers on calcite have their alkyl chains in an all-trans conformation and are anisotropically distributed on the plane of the surface, forming epitaxial monolayers. Vibrational spectra also show that the stearic acid molecules interact with the calcite surface through the carboxylic acid headgroup in both its protonated and deprotonated forms. The results presented provide new molecular insights into the properties of adsorbed carboxylic acid layers on calcite.

Surface modification of WE43 magnesium alloy via alkali/stearic acid treatment for biodegradable drug-eluting stent applications

WE43 is a biodegradable magnesium alloy with a high potential for cardiovascular stent applications. Although it has many adequate properties, there are barriers to using it as a drug-eluting stent vehicle. Corrosion and hydrogen gas formation have an adverse effect on the surface, causing attached drug carriers to separate, which limits its functionality as a stent. An alkali treatment in 1 M NaOH solution at various applied potentials was utilized to fix this issue. Subsequently, a stearic acid layer was formed by two different methods to reduce corrosion by decreasing water uptake of the surface. The anodic film's surface morphology and phase structure were analysed using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Nanoindentation tests were carried out to evaluate the anodic layer's mechanical properties. Its corrosion behaviour was characterized using potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS) and hydrogen evolution tests. The adhesive, thin yet effective oxide layers achieved in all the potentials showed increased corrosion resistance. It significantly decreased hydrogen formation, which were then sealed with stearic acid, and the surface became hydrophobic. This sealing layer acted as an additional barrier and enhanced the corrosion resistance of the magnesium alloy up to fifteen times bigger.

An exploration on CO faradaic efficiency with catalyst surface wettability ranging from hydrophilic to superhydrophobic

Hydrophobic electrode can facilitate CO2 mass transfer for carbon dioxide electroreduction reaction (CO2ER) in the microchannel reactor. However, ‘trade-off’ exists because the reaction cannot proceed in the absence of electrolyte. Therefore, effective control of wettability on the surface of the catalyst is significant to achieve efficient CO2ER performance. In this paper, a nanocone-shaped Zn@Ag has been fabricated through a simple two-step preparation process involving the hydrothermal treatment and the galvanic replacement. Further modification of the myristic acid (MA)/stearic acid (SA) layer on the nanocone by the immersion method can extend the interfacial wettability to the superhydrophobic scale. The experimental parameters including the time of three synthesis procedures were adjusted to regulate the dimensions and surface free energy of the nanocone. Consequently, the nanoncone catalyst itself possessed a maximum intrinsic water contact angle (CA) of ∼114°, while the SA modified catalyst demonstrated an outstanding water repellency with CA of ∼152°. The relationship between the CO Faradaic efficiency (FECO) and the surface wettability ranging from hydrophilic to superhydrophobic was ultimately explored. The optimal Zn@Ag@MA catalyst with appropriate hydrophobicity can achieve a FECO of 91%, which is nearly 20% higher than the hydrophilic/superhydrophobic counterpart. In situ attenuated total reflectance infrared (ATR-IR) tests verified that the hydrophobic catalyst can enhance CO2 concentration near the surface and promote the selectivity to CO.

Experimental Study on the Lubrication Enhancement of Slider-on-Disc Contact by Stearic Acid Adsorption under Limited Lubricant Supply

The optimization of the lubricant supply quantity contributes to minimizing energy losses and wastage. To enhance the performance of hydrodynamic bearings running with limited lubricant supply (LLS), this study examined the effect of stearic acid as an additive. Stearic acid is commonly used for boundary lubrication as an organic friction modifier. How the stearic acid adsorption affects the hydrodynamic lubrication of a slider-on-disc contact under LLS was investigated using interferometry measurement and fluorescence observation in this study. Firstly, the oil reservoir of PAO10 with stearic acid adsorption was observed at the slider entrance. Secondly, the film thickness versus speed of PAO10 and PAO10 with 0.1% and 0.3% stearic acid, respectively, were measured. Finally, the morphology and surface properties of the glass and steel blocks with stearic acid adsorption were characterized by atomic force microscopy and Fourier transform infrared spectroscopy. The results show that the stearic acid adsorption layer weakens the wettability of the lubrication track and induces the ‘dewetting’ phenomenon of the lubricating oil. Thus, discrete oil distribution in the form of stripe or droplet can be generated, which leads to the accumulation of lubricating oil at the slider entrance to form a reservoir. An additional inlet pressure that is generated by the oil reservoir due to surface tension increases the oil film formation capacity. Furthermore, the morphologies of the adsorbed stearic acid layer on the glass and the steel blocks are, respectively, characterized by the nano-sized granular bulge and brush structure. This study reveals a new role of stearic acid adsorption in promoting LLS lubrication.

The Impedance Analysis of a Viscoelastic Petalous Structured Stearic Acid Functional Layer Deposited on a QCM.

A functional layer is crucial in a QCM sensor, to immobilize target molecules. The microstructure of the layer determines the sensitivity of the sensor. On the other hand, the microstructure also affects the loading of the sensor. In this study, impedance analysis was used to investigate the relationship between the microstructure and the viscoelastic properties of a petalous stearic acid (SA) functional layer. The SA layer was deposited using a vacuum thermal evaporation technique. Different petalous pillar structures in the elastic layer were generated by varying the deposition time. Analysis showed that the growth of the embedded pillar structures dramatically reduced the conductance and increased the bandwidth. The energy dissipation during the vibration could be related to the interaction between the pillars and the elastic matrix.

Photocatalytic destruction of stearic acid by TiO2 films: Evidence of highly efficient transport of photogenerated electrons and holes

The oxidation of stearic acid (SA) by ambient air, photocatalysed by a TiO2 film, a common test for self-cleaning glass, often exhibits a rate of stearic acid removal, rSA, which is proportional to the fraction of UV light absorbed, which suggests that the transport of both photogenerated electrons and holes from the bulk to the surface is very efficient. This electron, hole transport (EHT) model is tested to the extreme using highly absorbing, absorbance ≫ 2, mesoporous (sol-gel) and microporous (P25) TiO2 films, ca. 0.5–1 μm thick, coated with a layer of SA. Scanning electron micrographs of these films show them to comprise closely connected clusters, which themselves comprise a network of primary photocatalytic particles. Each film produced identical [SA] vs irradiation time decay profiles when irradiated from the front or the back, even though in the latter case the UV irradiance reaching the photocatalyst particles in contact with the SA layer is at least 1000 times lower than the incident irradiance. These results suggest the transport of the photogenerated holes, and most likely electrons too, in these films is very efficient. When the SA layer is replaced with an Ag photocatalyst indicator ink, Ag paii, on a P25 TiO2 film, and irradiated from the back, the ink changes colour quickly due to the reduction of Ag+ in the ink, indicating that the transport of photogenerated electrons through the film is also efficient. The same effect is demonstrated using highly absorbing, and scattering, films of rutile TiO2, ZnO and WO3, thereby suggesting the EHT model is a general feature of networked nanoparticle films. The limitations of the EHT model, and how it differs from the commonly cited antenna model, are discussed along with the relevance of these findings with regard to self-cleaning glass.

Hydrophobicity improvement of cellulose nanofibrils films by stearic acid and modified precipitated calcium carbonate coating

The development of a cellulose nanofibrils film with permanent hydrophobicity using green processes, avoiding hazardous solvents, through easy procedures, is a great challenge. The hydrophobicity of a layer of calcium carbonate modified with stearic acid has already been presented. However, the combination of a cellulose nanofibrils film with a layer of modified calcium carbonate to develop a permanent hydrophobic cellulose-based material rises the additional issue of adhesion between layers. In the present study, a set of cellulose nanofibrils films was coated with a layer of stearic acid and another set was additionally covered with modified precipitated calcium carbonate (0.4–6 µm sized particles with above 50% aragonite crystalline form), previously modified with a stearic acid suspension using ultrasounds. To investigate the issue of adhesion between layers, some films were subjected to heat treatments at 68 and 105 °C. Structural and physical analysis of the films, as well as barrier properties and static/dynamic contact angle measurements were performed. Results show that overall mechanical performance of the films was not substantially affected by the coating and posterior heat treatments. Heat treatments decreased the water vapor transmission rate of stearic acid coated films from 91.9 to 31.6 g m−2 day−1 and the oxygen permeability of stearic acid and modified calcium carbonate coated films from 26.4 to 2.6 cm3 µm/(m2 day kPa). The double layered coated cellulose nanofibrils films attained contact angle hysteresis of 3.1° and 5° and static contact angles of 150° and 140° with no heat treatment and with a heat treatment of 68 °C, respectively. The heat treatment enabled to permanently adhere modified calcium carbonate particles on the film, providing it with persistent hydrophobicity.

Nanoscale Wear and Mechanical Properties of Calcite: Effects of Stearic Acid Modification and Water Vapor.

Understanding the wear of mineral fillers is crucial for controlling industrial processes, and in the present work, we examine the wear resistance and nanomechanical properties of bare calcite and stearic acid-modified calcite surfaces under dry and humid conditions at the nanoscale. Measurements under different loads allow us to probe the situation in the absence and presence of abrasive wear. The sliding motion is in general characterized by irregular stick-slip events that at higher loads lead to abrasion of the brittle calcite surface. Bare calcite is hydrophilic, and under humid conditions, a thin water layer is present on the surface. This water layer does not affect the friction force. However, it slightly decreases the wear depth and strongly influences the distribution of wear particles. In contrast, stearic acid-modified surfaces are hydrophobic. Nevertheless, humidity affects the wear characteristics by decreasing the binding strength of stearic acid at higher humidity. A complete monolayer coverage of calcite by stearic acid results in a significant reduction in wear but only a moderate reduction in friction forces at low humidity and no reduction at 75% relative humidity (RH). Thus, our data suggest that the wear reduction does not result from a lowering of the friction force but rather from an increased ductility of the surface region as offered by the stearic acid layer. An incomplete monolayer of stearic acid on the calcite surface provides no reduction in wear regardless of the RH investigated. Clearly, the wear properties of modified calcite surfaces depend crucially on the packing density of the surface modifier and also on the air humidity.

Friction Laws for Saturated/Unsaturated Fatty Acid Layers

The presence or absence of unsaturation in the carbon chain of carboxylic acids was examined on the friction response of boundary films according to normal force. Friction laws were established as a function of the normal force at the nanoscale with a molecular tribometer derived from a surface force apparatus. While the shear plane is mainly composed of methyl groups in all the cases investigated, the molecular organization differs within the shear plane, as suggested by the simultaneous film thickness evolution. This gave rise to dissipation modes within the interface, resulting in a wide range of shear stress levels and dependence with contact pressure. The friction laws were discussed, highlighting the combined role of nanometric surface roughness and molecule unsaturation.Graphic Abstract Friction laws for stearic acid ( ), elaidic acid ( ), and oleic acid ( ) boundary layers and schematic diagrams of the corresponding sheared interfaces

Natural henequen fibers functionalized with a magnetic fatty acid mixture

Herein henequen fibers have been functionalized by coating with a mixture containing stearic acid and ferrofluid. The surface coating was done using a one step immersion method giving as a result fibers with a surface layer having a magnetic response. Scanning electron microscopy shows that henequen has a regular porous structure, which makes it compatible with ferrofluid and allows setting a layer of magnetic nanoparticles and stearic acid on the surface of the fiber. The X-ray and infrared analyses as well as the hysteresis loops are consistent with separated phases of ferrofluid and stearic acid. The main advantage of these magnetic fibers is that it can be easily manipulated with an applied magnetic field.

Biomimetic highly hydrophobic stearic acid functionalized MOF sponge for efficient oil/water separation

The field of oil/water separation has become a global concern with increase in oil/water pollution. Fabrication of highly hydrophobic surfaces by bio mimicking the ‘Lotus effect’ is turning out to be an area of active research in this regard. In current work ZIF-8 functionalized, stearic acid functionalized and composite, incorporation ZIF-8 and stearic acid in different deposition sequences, functionalized hydrophobic sponges were fabricated by changing the surface roughness and surface chemistry. The prepared sponges were analyzed by X-ray diffraction, scanning electron microscopy, fourier transmission infrared spectroscopy and sessile drop technique to conform the prerequisite of ‘lotus effect’. The important parameters i.e. water contact angle, oil absorption capacity and reusability of all prepared sponges were compared and it was found that the composite sponge that have first layer of ZIF-8 followed by second layer of stearic acid (S1Z8S) well inherited all properties of its parent components, showed high hydrophobicity with water contact angle of 140.8° and high absorption capacity for different oils/organic solvents ranging from 30.26 to 115.35 times its own weight as compared to other sponge samples and the this value of absorption capacity remained constant for 10 absorption/desorption cycles. Furthermore, it was found that coating another layer of stearic acid (S1S1Z8S) on this hydrophobic sponge increases hydrophobicity to 143.2° because of increase in surface micro-bumps but decreases oil absorption capacity. Being a three in one package with high hydrophobicity, high oil absorption capacity and excellent reusability S1Z8S can be an optimum candidate for large scale practical applications.

Release and fate of nanoparticulate TiO2 UV filters from sunscreen: Effects of particle coating and formulation type.

Nanoparticulate mineral UV filters, such as titanium dioxide (TiO2) nanocomposites, are being increasingly used in sunscreens as an alternative to organic UV filters. However, there is still a lack of understanding regarding their fate and behavior in aquatic environments and potential environmental impacts after being released from a bather's skin during recreational activities. In this work, we assessed the release, fate, and transformation of two commercial nanocomposite TiO2 UV filters, one hydrophobic and one hydrophilic, in ultrapure water and simulated fresh- and seawater. The hydrophobic TiO2 nanocomposite, T-SA, was coated with a primary Al2O3 photopassivation layer and a secondary stearic acid layer, while the hydrophilic TiO2 nanocomposite, T-SiO2, was coated with a single SiO2 photopassivation layer. The influence of the sunscreen formulation was examined by dispersing the TiO2 nanocomposites in their typical continuous phase (i.e., oil for T-SA and water for T-SiO2) before introduction into the aqueous system. After 48h of aqueous aging and 48h of settling, 88-99% of the hydrophobic T-SA remained floating on top of the water column in all aqueous systems. On the other hand, 100% of the hydrophilic T-SiO2 settled out of the water column in the fresh- and seawaters. With respect to the photopassivation coatings, no loss of the T-SA Al2O3 layer was detected after aqueous aging, but 99-100% dissolution of the SiO2 layer on the T-SiO2 nanocomposite was observed after 48h in the fresh- and seawaters. This dissolution left behind T-SiO2 by-products exhibiting a photocatalytic activity similar to that of bare rutile TiO2. Overall, the results demonstrated that the TiO2 surface coating and sunscreen formulation type drive environmental behavior and fate and that loss of the passivation layer can result in potentially harmful, photoactive by-products. These insights will help guide regulations and assist manufacturers in developing more environmentally safe sunscreens.

Durability of superhydrophobic duplex coating systems for aerospace applications

In-flight icing, caused by the collision of supercooled water droplets with exposed aircraft surfaces, is an important safety hazard and a major issue in aviation. Superhydrophobic surfaces (SHS) have been shown to offer improvements to heating-based anti-icing and de-icing systems, reducing energy requirements for ice prevention and facilitating ice removal. A common SHS fabrication technique is to develop a surface with hierarchical roughness, and to then coat this surface with a hydrophobic topcoat. From this arises an issue: the durability of the entire system is fundamentally limited to the durability of this topcoat. In the present study, we develop a superhydrophobic duplex coating system with an emphasis on the environmental durability of the thin hydrophobic layer. The system consists of a thick TiO2 coating deposited by suspension plasma spraying, and a thin coating stack deposited by plasma enhanced chemical vapor deposition. The thin coating stack is based on DLC:SiOx—diamond-like carbon networked with silicon oxide—which exhibits a water contact angle of up to 95° and a hardness of up to 11 GPa, while the full coating system offers a contact angle of 159° and a contact angle hysteresis of 3.8°. The coating system is exposed to icing/deicing cycling, as well as rain erosion and accelerated aging tests; the results are compared with TiO2 coatings using stearic acid and fluoropolymer hydrophobic layers, as well as a commercially available superhydrophobic spray. The duplex coating system is shown to maintain water droplet mobility after 170 icing/deicing cycles, is resistant to prolonged UV and high-temperature exposure and offers a 300-fold improvement over the stearic acid in rain erosion tests.

Sustainable, Fluorine-Free, Low Cost and Easily Processable Materials for Hydrophobic Coatings on Flexible Plastic Substrates.

Zinc oxide nanoparticles (ZnONPs) and stearic acid are herein used for the preparation of hydrophobic coatings with good moisture barrier property on flexible plastic substrates. Fast, high throughput, mild and easy-to-run processing techniques, like airbrushing and gravure printing, are applied for thin films deposition of these materials. The results of this study indicated that the best hydrophobic coating in terms of water contact angle (115°) is obtained through a two-steps printing deposition of a ZnONPs layer followed by a stearic acid layer. All the deposition procedures proved to be effective in terms of water vapor barrier properties, reaching values of 0.89 g/m2/day, with a 45% reduction with respect to the bare substrate. These preliminary data are very encouraging in the perspective of a low cost and green approach for the realization of functional coatings for packaging applications.

Protection of aluminum alloy AD31 from corrosion by adsorption layers of trialkoxysilanes and stearic acid

The effectiveness of protection of technical aluminum AD31 by its hydrophobization and superhydrophobization (SHP) with ethanol solutions of trialkoxysilanes and stearic acid was evaluated. The stability of SHP coatings in distilled water and chloride solution was studied. The thickness of the formed SHP layers is determined by the ellipsometric method. Polarization measurements, electrochemical impedance spectroscopy, and corrosion tests have shown that SHP coatings have a protective ability in 3% NaCl and under the impact of salt spray.

Super-hydrophobic stearic acid layer formed on anodized high purified magnesium for improving corrosion resistance of bioabsorbable implants

Abstract Magnesium and its alloys are ideal candidates for bioabsorbable implants. However, they can dissolve too rapidly in the human body for most applications. In this research, high purified magnesium (HP-Mg) was coated with stearic acid (SA) to slow the corrosion rate of magnesium in simulated body fluid at 37 ± 1 °C. HP-Mg was anodized (AC and DC voltages) to form an oxide/hydroxide layer, and then it was immersed in a SA solution. The SA coated layer surface, anodized layer, and the thickness of the oxide/hydroxide layer were investigated with Scanning Electron Microscopy (SEM). Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were used to estimate the corrosion rate of HP-Mg specimens. The results confirm that the hydrophobic coating can decrease the corrosion rate of HP-Mg by more than 1000x. The protectiveness of coated layer for anodized specimens with AC voltage continue for 2 and 3 weeks. For the HP-Mg coated anodized with DC voltage, the coated layer could improve the corrosion resistance for only a few days.