Stearic Acid Monolayers Research Articles

Solution Processed Hybrid Lead Perovskite Films for White Light Emission and Lasing Applications

Abstract2D organic–inorganic hybrid lead halide perovskite films are fascinating optoelectronic materials for white‐light emission and lasing applications. Here, it is demonstrated that nano‐meter‐thick films of perovskites can be formed at room temperature using Langmuir–Schaefer (LS) deposition technique. In situ X‐ray measurements reveal a self‐assembly process of the 2D perovskite formation at the air–water interface. This formation process requires the presence of stearic acid monolayer on the water subphase having a solution of lead‐perovskite in dimethylformamide. Microscopy and X‐ray measurements of these nanofilms transferred onto substrates show crystalline phase formation that deviates from the known orthorhombic structure of the bulk crystals. The nanofilms exhibit novel broad optical emission with sharp band‐edge transition in temperature‐dependent photoluminescence studies. Also, their band‐edge emission is distinctly blue‐shifted compared to that of thicker 2D perovskite flakes prepared by the slow‐cooling chemical synthesis process. 2D flakes exhibit lasing that cannot be obtained in the LS nanofilms as their thicknesses are lower than the lasing wavelength prohibiting wave‐guide formation. The results show that the 2D single‐crystalline nature of the LS films and flakes are suitable materials to develop broad‐band white light emission across the entire visible range and to obtain lasing without external cavities, respectively.

The effect of gamma rays and stearic acid on calcium carbonate and its impact on the properties of epoxy-based composites

Abstract The purpose of this research is to produce composites of epoxy resin and calcium carbonate (EP/CaCO3) and investigate how treating the CaCO3 filler with stearic acid and gamma radiation affects the properties of the epoxy composites, enhancing their suitability for a range of applications. The CaCO3 powder was subjected to stearic acid treatment and later exposed to γ-radiation at various doses namely (10, 20 and 30 kGy), Different weight percentages of untreated and treated CaCO3 powder were added to epoxy resin (EP) to create EP/CaCO3 composites loaded with varying amounts of CaCO3 filler (5 %, 10 %, 20 %, 30 %, and 40 %). The influence of both stearic acid treatment and different doses of gamma radiation on CaCO3 was investigated. The composites were subjected to characterization of various properties including mechanical (splitting tensile strength, impact strength), thermal (TGA and dimensional thermal analysis) as well as morphological SEM examination. The analysis’ findings demonstrated that the stearic acid monolayer functions as a coupling agent in the EP matrix and can coat CaCO3 particles efficiently. The modification of CaCO3 by stearic acid and exposure to 30 kGy of gamma radiation shows a notable improvement in thermal stability and mechanical qualities for the epoxy composites loaded with various CaCO3 concentrations.

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.

Stearic Acid as an Atomic Layer Deposition Inhibitor: Spectroscopic Insights from AFM-IR.

Modern-day chip manufacturing requires precision in placing chip materials on complex and patterned structures. Area-selective atomic layer deposition (AS-ALD) is a self-aligned manufacturing technique with high precision and control, which offers cost effectiveness compared to the traditional patterning techniques. Self-assembled monolayers (SAMs) have been explored as an avenue for realizing AS-ALD, wherein surface-active sites are modified in a specific pattern via SAMs that are inert to metal deposition, enabling ALD nucleation on the substrate selectively. However, key limitations have limited the potential of AS-ALD as a patterning method. The choice of molecules for ALD blocking SAMs is sparse; furthermore, deficiency in the proper understanding of the SAM chemistry and its changes upon metal layer deposition further adds to the challenges. In this work, we have addressed the above challenges by using nanoscale infrared spectroscopy to investigate the potential of stearic acid (SA) as an ALD inhibiting SAM. We show that SA monolayers on Co and Cu substrates can inhibit ZnO ALD growth on par with other commonly used SAMs, which demonstrates its viability towards AS-ALD. We complement these measurements with AFM-IR, which is a surface-sensitive spatially resolved technique, to obtain spectral insights into the ALD-treated SAMs. The significant insight obtained from AFM-IR is that SA SAMs do not desorb or degrade with ALD, but rather undergo a change in substrate coordination modes, which can affect ALD growth on substrates.

Soft removal of stearic acid self-assembled monolayer for area-selective atomic layer deposition

Stearic acid (SA) self-assembled monolayer (SAM) is proposed as a soft-removal passivating agent for area-selective atomic layer deposition (AS-ALD) applications. First, the SAM formation kinetics and its thermal stability were evaluated on a copper surface. We observed a highly packed, hydrophobic, and ordered monolayer. The transition temperature from order to disorder was observed above 160 °C. Next, the SA/copper was evaluated as a non-growth surface for ZnO ALD and monitored by X-ray Photoelectron Spectroscopy (XPS). The optimal ALD parameters were found at 70 °C, dosing 25 ms of diethyl zinc precursor and water, while purge was 10 s for each. In these conditions, the attenuation growth remained for at least 40 ALD cycles; despite zinc deposition after the first three cycles. Finally, the removal of the SA monolayer was investigated with water, acetone, and ethanol at room temperature. According to infrared and water contact angle, ethanol was the most effective, showing a complete removal after 30 min immersion time (without sonication or agitation). We conclude that SA SAM is an efficient removable copper passivating agent for area-selective atomic layer deposition without exposing samples to harsh conditions, like etching or acid treatments.

Interfacial interactions in urease/stearic acid and urease/DOPC binary mixed systems at the air-water and the air-solid interfaces

In the present study, the protein-lipid interactions between water-soluble metalloenzyme urease (Urs) and insoluble stearic acid (SA) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) were investigated at the air–water interface using the Langmuir-Blodgett (LB) technique. Surface pressure (π) - molecular area (A) isotherms were measured for the pure SA and pure DOPC monolayers in the presence of urease in the water subphase. From the (π – A) isotherms of the binary system, it was found that urease strongly interacts with SA and DOPC. The compressibility of the SA monolayer was reduced with the incorporation of urease; a similar trend was also found with DOPC. Moreover, an association of urease with lipid monolayers was found to be surface pressure (π) dependent. The presence of a little hump in the mixed isotherms of Urs-SA at low surface pressure supports this observation. However, the miscibility studies and the calculations of excess Gibb’s free energy indicate an attractive interaction between urease and SA molecules. The considerable morphological variations observed by atomic force microscopy (AFM) in urease-SA deposited films onto hydrophilic and hydrophobic Si(100) surfaces suggest that urease was strongly bound with the surrounding lipid SA on the hydrophilic surfaces but the urease molecules were rigorously denatured on the hydrophobic surfaces. The AFM analysis of Urs-DOPC mixed LB films at room temperature (RT) and elevated temperature suggests substantial denaturation of urease in a hydrophobic environment leading us to speculate the exposure of tryptophan moieties of the urease molecules to the hydrophobic air phase.

New Insights into Cation- and Temperature-Driven Protein Adsorption to the Air–Water Interface through Infrared Reflection Studies of Bovine Serum Albumin

The chemistry and structure of the air-ocean interface modulate biogeochemical processes between the ocean and atmosphere and therefore impact sea spray aerosol properties, cloud and ice nucleation, and climate. Protein macromolecules are enriched in the sea surface microlayer and have complex adsorption properties due to the unique molecular balance of hydrophobicity and hydrophilicity. Additionally, interfacial adsorption properties of proteins are of interest as important inputs for ocean climate modeling. Bovine serum albumin is used here as a model protein to investigate the dynamic surface behavior of proteins under several variable conditions including solution ionic strength, temperature, and the presence of a stearic acid (C17COOH) monolayer at the air-water interface. Key vibrational modes of bovine serum albumin are examined via infrared reflectance-absorbance spectroscopy, a specular reflection method that ratios out the solution phase and highlights the aqueous surface to determine, at a molecular level, the surface structural changes and factors affecting adsorption to the solution surface. Amide band reflection absorption intensities reveal the extent of protein adsorption under each set of conditions. Studies reveal the nuanced behavior of protein adsorption impacted by ocean-relevant sodium concentrations. Moreover, protein adsorption is most strongly affected by the synergistic effects of divalent cations and increased temperature.

Langmuir-Blodgett Films of Arachidic and Stearic Acids as Sensitive Coatings for Chloroform HF SAW Sensors.

Properties of the Langmuir-Blodgett (LB) films of arachidic and stearic acids, versus the amount of the films' monolayers were studied and applied for chloroform vapor detection with acoustoelectric high-frequency SAW sensors, based on an AT quartz two-port Rayleigh type SAW resonator (414 MHz) and ST-X quartz SAW delay line (157.5 MHz). Using both devices, it was confirmed that the film with 17 monolayers of stearic acid deposited on the surface of the SAW delay line at a surface pressure of 30 mN/m in the solid phase has the best sensitivity towards chloroform vapors, compared with the same films with other numbers of monolayers. For the SAW resonator sensing using slightly longer arachidic acid molecules, the optimum performance was reached with 17 LB film layers due to a sharper decrease in the Q-factor with mass loading. To understand the background of the result, Atomic Force Microscopy (AFM) in intermittent contact mode was used to study the morphology of the films, depending on the number of monolayers. The presence of the advanced morphology of the film surface with a maximal average roughness (9.3 nm) and surface area (29.7 µm2) was found only for 17-monolayer film. The effects of the chloroform vapors on the amplitude and the phase of the acoustic signal for both SAW devices at 20 °C were measured and compared with those for toluene and ethanol vapors; the largest responses were detected for chloroform vapor. For the film with an optimal number of monolayers, the largest amplitude response was measured for the resonator-based device. Conversely, the largest change in the acoustic phase produced by chloroform adsorption was measured for delay-line configuration. Finally, it was established that the gas responses for both devices coated with the LB films are completely restored 60 s after chamber cleaning with dry air.

Superhydrophobic Stainless Steel Bipolar Plates with Fractal Structure for Fuel Cells by Nanosecond Laser Ablation

Bipolar plate (BP) is one of the crucial components in proton exchange membrane fuel cells (PEMFCs). In extreme cold weather, massive vapor condensation happens right at vehicle start‐ups, which likely causes “water flooding” and thus shortens the lifespan of PEMFCs. Herein, a superhydrophobic stainless steel bipolar plate (SH‐SS BP) that is fabricated by nanosecond laser ablation is reported. Through a repeated low‐energy processing strategy, fractal surface microstructure is fabricated, which has not been reported for SS BP. By grafting stearic acid (SA) monolayer, a robust SH‐SS BP is obtained with a contact angle of 151.74°. The fractal microstructure greatly enhances the contact area between SH‐SS BP and membrane electrode assembly (MEA), which improves interfacial contact resistance (ICR: 9.816 mΩ cm2 at 1.5 MPa). The SH‐SS BP shows significantly enhanced anticorrosion performance (= A cm−2) by effectively reducing penetration of corrosive. The ability of improving water management in PEMFC under extreme cold condition is further demonstrated in a simulated PEMFC. This study opens new opportunity to reinforce metallic BPs by a simple, low‐cost, and robust route, which is valuable in improving comprehensive weather fastness of PEMFC.

Surface-Modified and Unmodified Calcite: Effects of Water and Saturated Aqueous Octanoic Acid Droplets on Stability and Saturated Fatty Acid Layer Organization.

A profound understanding of the properties of unmodified and saturated fatty acid-modified calcite surfaces is essential for elucidating their resistance and stability in the presence of water droplets. Additional insights can be obtained by also studying the effects of carboxylic acid-saturated aqueous solutions. We elucidate surface wettability, structure, and nanomechanical properties beneath and at the edge of a deposited droplet after its evaporation. When calcite was coated by a highly packed monolayer of stearic acid, a hydrophilic region was found at the three-phase contact line. In atomic force microscopy mapping, this region is characterized by low adhesion and a topographical hillock. The surface that previously was covered by the droplet demonstrated a patchy structure of about 6 nm height, implying stearic acid reorganization into a patchy bilayer-like structure. Our data suggest that during droplet reverse dispensing and droplet evaporation, pinning of the three-phase contact line leads to the transport of dissolved fatty carboxylic acid and possibly calcium bicarbonate Ca(HCO3)2 molecules to the contact line boundary. Compared to the surface of intrinsically hydrophobic materials, such as polystyrene, the changes in contact angle and base diameter during droplet evaporation on stearic acid-modified calcite are strikingly different. This difference is due to stearic acid reorganization on the surface and transport to the water–air interface of the droplet. An effect of the evaporating droplet is also observed on unmodified calcite due to dissolution and recrystallization of the calcite surface in the presence of water. In the case where a water droplet saturated with octanoic acid is used instead of water, the stearic acid-coated calcite remains considerably more stable. Our findings are discussed in terms of the coffee-ring effect.

Stearic acid mediated growth of edge-on oriented bilayer poly(3-hexylthiophene) Langmuir films

The growth and structural evolution of stearic acid (SA) blended poly(3-hexylthiophene) [P3HT] Langmuir and Langmuir–Blodgett (LB) films were studied using complimentary surface and interface sensitive techniques to understand the possibility of ordering and layering of promising charge carrier mobility polymers, at the air–water interface and on the transferred solid substrate. SA-induced and subsequent compression-induced transitions in P3HT structure, from aggregated-3D to soft-2D and from in-plane mixed to unmixed layer, are evident at low and high pressures, respectively. The blending of SA molecules enhances the amphiphilic character of P3HT, which reduces the extent of the out-of-plane aggregation to form edge-on oriented (EO) bottom side-chain folded-bilayer (f-BL) islands (of size ~60 nm) within SA monolayer (ML), of commensurate thickness (~2.6 nm). Further compression, gradually rejects the less hydrophilic f-BL islands from the mixed layer to form EO P3HT BL islands (of coverage in-tune with starting composition) on top of SA ML. The formation of nearly covered P3HT(BL)/SA(ML) structured film on solid substrate is evident for the first time, which (even of limited P3HT thickness) has immense importance in the device properties, as the current in the bottom-gated organic thin-film transistors is known to travel only within few ML region near gate-dielectric.

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.

Unraveling interfacial properties of organic-coated marine aerosol with lipase incorporation

Marine aerosols are believed to have an organic surface coating on which fatty acids act as an important component due to their high surface activity. In addition, various kinds of enzyme species are abundantly found in seawater, some of which have been identified to exist in marine aerosols. Herein, from the perspective of marine aerosol interface simulation, we investigate the effect of Burkholderia cepacia lipase on the surface properties of stearic acid (SA) monolayer at the air-water interface by using surface-sensitive techniques of Langmuir trough and Infrared reflection-absorption spectroscopy (IRRAS). Our findings indicate that the stearic acid film undergoes a significant expansion, especially when the lipase concentration is 500 nM, because of the incorporation of lipase as observed from the surface pressure-area (π-A) isotherms. IRRAS spectra also show reduced intensities and ordering in the methylene stretching vibration region of stearic acid as a result of low surface density and disordered packing as the enzyme concentration increases. In particular, when the concentration of lipase is 500 nM, the lowest Ias/Is values are shown on both pure water subphase and artificial seawater subphase, indicating more gauche conformations for SA. Furthermore, SA films with lipase incorporation were also studied at three different pH of subphase environment, considering the decrease of pH caused by the reaction with acidic gases during the aerosol aging process. The results reflect a more pronounced expansion of SA monolayer in acidic environment at pH 2.5, suggesting that hydrophobic interaction plays an important role in the disorder of the SA monolayer. In view of the coexistence of fatty acids and enzymes in the marine environment, this study provides a further understanding of the surface organization and behavior of organic-coated marine aerosols and deepen the knowledge of lipid-enzyme interfacial interactions occurring in the atmosphere.

Extreme sensitivity of plasmon drag to surface modification

Giant enhancement of photocurrents in plasmonic structures (plasmon drag effect) provides opportunities for compact electric monitoring of plasmonic effects, and thus is promising for plasmonic-based sensing applications. In the experiment, we measure photoinduced electric signals in flat and profile-modulated systems, and test their sensitivity to small changes of the local dielectric environment, such as a presence of Langmuir–Blodgett monolayers at the metal surface. We show that the addition of a stearic acid monolayer leading to a small shift in plasmon resonance conditions can be ultimately resolved with electrical measurements as the switching in the photovoltage polarity.

Development of self-assembled monolayer of stearic acid grafted chitosan on mild steel and inhibition of corrosion in hydrochloric acid

Abstract Chitosan (CS) based systems are extensively used as a green alternative for corrosion protection of mild steel (MS) possessing good film-forming properties, chelation with metal and nontoxic nature. In this study, a self-assembled monolayer of stearic acid grafted chitosan was developed via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide mediated coupling reaction and casted on the MS surface. From the fluorescence intensity of the fluorescent probe pyrene, the critical micelle concentration (66 μg/mL) of self-aggregates in aqueous solution was determined. The purified chitosan grafted films were characterized by apposite analytical techniques. The film developed was employed for corrosion protection of MS in 0.5 and 1 N HCl via electrochemical and non-electrochemical techniques. The results showed that stearic acid grafted chitosan (CSA) films do offer better corrosion protection to MS than bare CS film.

Electrodeposition of hydroxyapatite coating on Mg alloy modified with organic acid self-assembled monolayers

Calcium phosphate coatings are used in orthopedics due to their excellent bioactivity, which improves the bonding between the metal implant and the bone. The use of self-assembling monolayers of long-chain organic acids can induce calcium phosphate growth. In this article, the self-assembling monolayers of stearic acid and octadecylphosphonic acid formed on the Mg alloy surface were additionally modified with electrodeposited hydroxyapatite coating to increase the bioactivity and biocompatibility of the Mg alloy in a physiological solution. Hydroxyapatite coating was prepared by a two-step reaction: hydrogen phosphate formed by electrodeposition at constant potential was converted into hydroxyapatite coating through an acid–base reaction. The results obtained by voltammetry and electrochemical impedance spectroscopy have shown a beneficial effect of organic acid self-assembling monolayer and especially of organic acid self-assembling monolayer modification by hydroxyapatite electrodeposition on the corrosion properties of Mg alloy in physiological solution. Fourier transform infrared spectroscopy and scanning electron microscopy were used to verify the existence of the organic acid SAM|HAp film on the Mg alloy surface and their morphology.

Alterations in the surface properties of sea spray aerosols introduced by the presence of sterols

The mixed stearic acid (SA)/sterol systems were used as sea spray aerosol mimics to get more insights into the alterations in surface properties of aerosols induced by sterols. By means of surface pressure (π)–area (A) isotherms and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS), the effect of cholesterol (chol), stigmasterol (stig) and ergosterol (erg) on the lateral packing and chain conformation of SA monolayer was explored. The fact that the excess areas of mixing of the mixed monolayers exhibit significant deviations from ideally mixed film proves that, the sterols are miscible with SA throughout all the monolayer compositions and surface pressures examined. The lift-off areas in π–A isotherms were found to increase with increasing mole fraction of sterols, indicating that expulsive interactions exist between SA and sterols, which are more pronounced when the mole fraction of sterols is 0.7. In addition, the peak intensities of νa(CH2) and νs(CH2) in IRRAS spectra decrease with increasing sterols levels, which is consistent with our findings in the π–A isotherms, that the addition of sterols leads to a looser chain packing in SA monolayer. The proportion of gauche defects in SA monolayer induced by the sterols follows the order cholesterol < stigmasterol < ergosterol at a certain sterol level, as reflected by the decreasing peak intensities of νa(CH2) and νs(CH2). Consequently, the sterols generally give rise to considerable expanding effects on SA monolayer, which are particularly pronounced for stigmasterol and ergosterol, suggesting that the additional alkyl side chains and double bonds of the sterols play a role on disordering SA monolayer. The present study is likely to shed light on many boundary processes take place at the interface of SSAs, in particular, transport processes of water and trace gases across the interface.

Establishing a model organic film of low volatile compound mixture on aqueous aerosol surface

Long chain fatty acids and alcohols are low volatile species in continental and marine aerosols. We established a surface film model by Langmuir trough to investigate the interfacial properties of sea salts droplets coated by surface active molecules—stearic acid (SA), oleic acid (OA), 1-octadecanol (C18OH) and their mixtures. The aim of this work was to verify the impact of the head group, saturation degree, mixing ratio of different surfactants on miscibility and stability between these compounds in monolayers at the air–water interface. Compared to the organic-coated water droplets, the surface properties of mixed fatty acid and alcohol-coated aqueous sea salt particles are substantially different. Mixed SA/C18OH monolayers are less stable than pure SA or C18OH monolayer at high surface pressure. From the point of view of the geometry, steric hindrance of unsaturated chain is the crucial factor in loose packing of OA monolayer. The negative values of excess mixing areas (ΔAex) for OA/C18OH monolayer on artificial seawater result from the attractive interaction between tail groups. The maximum negative value of excess Gibbs free energies (ΔGex) appears at the equimolecular OA and C18OH. Surface pressure−area (π–A) isotherm combined with equilibrium spreading pressure (ESP) confirms that the tightly packed monolayer formed by C18OH molecules can minimize water evaporation rate of the potential droplet. Different surface properties of organic films coated on aqueous aerosol must have a significant impact on interaction droplet growth. The interactions between fatty acid and alcohol at the air-water interface provide an insight into the nucleation and growth mechanism of droplets covered by film-forming species.

Structural and optical properties of two-dimensional gadolinium stearate Langmuir monolayer

Langmuir-Blodgett (LB) films having large stack of amphiphilic-fatty-acids bearing rare-earth-ions are ideal two-dimensional magnetic systems to study spin-vortex ordering as the distances of the magnetic-ions along the out-of-plane and in-plane directions differ by an order of magnitude. Here we present results of in-situ X-ray scattering measurements on Langmuir monolayer of the amphiphilic stearic acid on the water surface containing Gadolinium ions to understand the formation process of monolayer and multilayer LB films on the substrates. Infrared spectroscopy and microscopy measurements were also carried out to understand the growth and transfer mechanism of the LB films.

Self-Assembling Monolayers of Stearic Acid in Protection of Steel

Carbon steel corrodes severely in presence of sodium chloride and it needs additional protection to be used in marine environments. This work investigates the possibility of using a layer of stearic acid as protection for carbon steel. Stearic acid was applied on the steel by two types of treatments: chemical preparation - by immersion of a steel sample in the SA solution and electrochemical preparation – by imposing a corresponding potential to the system. The results have shown that although both treatments result in obtaining an ordered aliphatic monolayer and both treatments increase the hydrophobicity of the surface, protection that the electrochemical preparation offers is stable in time, while the protection the chemical preparation offers is not.