Oleic Acid Molecules Research Articles

Effect of Oleic Acid on the Dynamic Interfacial Tensions of Surfactant Solutions

The dynamic interfacial tensions (IFTs) of three different types of surfactant solutions, cationic surfactant hexadecyl trimethylammonium (CTAB), anionic surfactant sodium dodecyl benzenesulfonate (SDBS), and non-ionic surfactant Triton X-100 (TX-100), against model oil containing oleic acid (OA) have been investigated by a spinning drop interfacial tensiometer. The influences of the OA concentration and addition of alkali have been studied. The experimental results show that OA added to the oil phase has a significant effect on interfacial behaviors of surfactant solutions. An obvious synergistic effect on reducing IFT can be observed for low-concentration cationic surfactant CTAB solution because the tight mixed adsorption films will be formed through electrostatic attraction between CTAB and OA molecules. However, the synergistic effect will disappear at a high surfactant concentration by the formation of mixed micelles. For the anionic surfactant SDBS system, the mixed adsorption of SDBS and OA molecu...

A green and facile approach to the efficient surface modification of alumina nanoparticles with fatty acids

A general, green and facile approach to the efficient surface modification of alumina and other metal oxide nanoparticles with fatty acids have been proposed. In this process, only water was used as the dispersing medium, the modified metal oxide nanoparticles were automatically separated from water, and water can be recycled. The modification efficiency, using oleic acid as an example, of this water alone method was 36% higher than that of the water-ethanol method, which is a result of higher opportunity of interfacial reaction between oleic acid and Al2O3 molecules on the surface of alumina nanoparticles dispersed in water only. The modification efficiency increases with increasing chain length of the fatty acids. After modification with fatty acids, the crystalline structure of alumina remains unchanged, the agglomeration of alumina nanoparticles was largely reduced, and much better dispersion of modified alumina nanoparticles in organic matrix than the raw ones was achieved.

Mechanical and spectroscopic characterization of crosslinked zein films cast from solutions of acetic acid leading to a new mechanism for the crosslinking of oleic acid plasticized zein films

This study discovered through FTIR, FT-Raman and rheological measurements that glutaraldehyde binds to zein through the amine groups of glutamine turns by replacing the already-bonded oleic acid molecules and forming imine structures. As a secondary crosslinking mechanism, glutaraldehyde unfolds some of the α-helices and turns them into β-sheets. While crosslinking resulted in stiffer and less ductile zein films, it made the surface of the films rougher, measured using AFM, and more hydrophilic, measured using WCA. In the crosslinking conditions in this study, the number of crosslinks estimated from rubber elasticity theory were not enough to change the water vapor permeability of the films significantly. Improving the understanding of crosslinking mechanism and its effects on physical and chemical properties of zein films can be useful to develop stiffer, stronger and more durable platforms for biodegradable biosensors, microfluidic devices or scaffolds.

Probing Anisotropic Surface Properties and Surface Forces of Fluorite Crystals.

Fluorite is the most important mineral source for producing fluorine-based chemicals and materials in a wide range of engineering and technological applications. In this work, atomic force microscopy was employed, for the first time, to probe the surface interactions and adhesion energy of model oleic acid (a commonly used surface modification organics for fluorite) molecules on fluorite surfaces with different orientations in both air and aqueous solutions at different pH conditions. Fitted with the Derjaguin-Landau-Verwey-Overbeek theory, the force results during surface approaching demonstrate the anisotropy in the surface charge of different orientations, with the {111} surface exhibiting a higher magnitude of surface charge, which could be attributed to the difference in the atomic composition. The adhesion measured during surface retraction shows that model oleic acid molecules have a stronger adhesion with the {100} surface than with the {111} surface in both air and aqueous solutions. The anisotropic adhesion energy was analyzed in relation to the surface atom (especially calcium) activity, which was supported by the surface free energy results calculated based on a three-probe-liquid method. Each calcium atom on the {100} surface with four dangling bonds is more active than the calcium atom on the {111} surface with only one dangling bond, supported by a larger value of the Lewis acid component for the {100} surface. The model oleic acid molecules present in the ionic form at pH 9 exhibit a higher adhesion energy with fluorite surfaces as compared to their molecular form at pH 6, which was related to the surface activity of different forms. The adhesion energy measured in solution is much lower than that in air, indicating that the solvent exerts an important influence on the interactions of organic molecules with mineral surfaces. The results provide useful information on the fundamental understanding of surface interactions and adhesion energy of organic molecules on mineral surfaces with different orientations, and the methodology can be extended to many other crystal surfaces in various interfacial processes.

Electrochemical surface-enhanced Raman scattering measurement on ligand capped PbS quantum dots at gap of Au nanodimer

The vibrational characteristics of ligand-capped lead sulfide (PbS) quantum dots (QDs) were clarified via electrochemical surface-enhanced Raman spectroscopy (EC-SERS) using a hybridized system of gold (Au) nanodimers and PbS QDs under electrochemical potential control. Enhanced electromagnetic field caused by the coupling of QDs with plasmonic Au nanodimers allowed the characteristic behavior of the ligand oleic acid (OA) on the PbS QD surface to be detected under electrochemical potential control. Binding modes between the QDs and OA molecules were characterized using synchronous two-dimensional correlation spectra at distinct electrochemical potentials, confirming that the bidentate bridging mode was probably the most stable mode even under relatively negative potential polarization. Changes in binding modes and molecular orientations resulted in fluctuations in EC-SERS spectra. The present observations strongly recommend the validity of the QD–plasmonic nanostructure coupled system for sensitive molecular detection via EC-SERS.

Ligand-exchange TiO2 nanocrystals induced formation of high-quality electron transporting layers at low temperature for efficient planar perovskite solar cells

Exploration of low-temperature solution-processed methodology for fabricating planar perovskite solar cells (PSCs) is meaningful for simplifying manufacturing, roll-to-roll industrial mass production on flexible substrates and designing perovskite tandem devices. However, some complicated, time consuming, or even high-cost methodologies such as atomic layer deposition, magnetron sputtering, and utilizing careful interface engineering are still needed for preparing efficient planar PSCs with TiO2 electron transport layers (ETLs) at low temperature. Here, we report a simple ligand-exchange strategy to overcome the problems. We use oleic acid (OA) molecules as surface ligands for synthesis well crystalline and monodisperse TiO2 nanocrystals. Subsequently, instead of high temperature decomposition, we find that the ligand-exchange strategy can also totally peel off these insulating ligands on the TiO2 nanocrystal surfaces and form high-quality TiO2 ETLs at low temperature. The OA-free TiO2 ETLs prepared at 150°C show high conductivity, fast electron extraction and transport speeds, low series resistance and high shunt resistance in the assembled PSCs, contributing to high performance devices with slight hysteresis and good reproducibility.

Modulation of saturation and chain length of fatty acids in Saccharomyces cerevisiae for production of cocoa butter-like lipids.

Chain length and degree of saturation plays an important role for the characteristics of various products derived from fatty acids, such as fuels, cosmetics, and food additives. The seeds of Theobroma cacao are the source of cocoa butter, a natural lipid of high interest for the food and cosmetics industry. Cocoa butter is rich in saturated fatty acids that are stored in the form of triacylglycerides (TAGs). One of the major TAG species of cocoa butter, consisting of two stearic acid molecules and one oleic acid molecule (stearic acid-oleic acid-stearic acid, sn-SOS), is particularly rare in nature as the saturated fatty acid stearic acid is typically found only in low abundance. Demand for cocoa butter is increasing, yet T. cacao can only be cultivated in some parts of the tropics. Alternative means of production of cocoa butter lipids (CBLs) are, therefore, sought after. Yeasts also store fatty acids in the form of TAGs, but these are typically not rich in saturated fatty acids. To make yeast an attractive host for microbial production of CBLs, its fatty acid composition needs to be optimized. We engineered Saccharomyces cerevisiae yeast strains toward a modified fatty acid synthesis. Analysis of the fatty acid profile of the modified strains showed that the fatty acid content as well as the titers of saturated fatty acids and the titers of TAGs were increased. The relative content of potential CBLs in the TAG pool reached up to 22% in our engineered strains, which is a 5.8-fold increase over the wild-type. SOS content reached a level of 9.8% in our engineered strains, which is a 48-fold increase over the wild type.

3D superstructures with an orthorhombic lattice assembled by colloidal PbS quantum dots.

We report a new type of metamaterial comprising a highly ordered 3D network of 3-7 nm lead sulfide quantum dots self-assembled in an organic matrix formed by amphiphilic ligands (oleic acid molecules). The obtained 3D superstructures possess an orthorhombic lattice with the distance between the nanocrystals as large as 10-40 nm. Analysis of self-assembly and destruction of the superstructures in time performed by a SAXS technique shows that their morphology depends on the quantity of amphiphilic ligands and width of the quantum dot size and its distribution. Formation of the superstructures is discussed in terms of a model describing the lyotropic crystal formation by micelles from three-phase mixtures. The results show that the organic molecules possessing surfactant properties and capable of forming micelles with nanoparticles as a micelle core can be utilized as building blocks for the creation of novel metamaterials based on a highly ordered 3D network of semiconductors, metals or magnetic nanoparticles.

Facile and economical synthesis of superparamagnetic magnetite nanoparticles coated with oleic acid using sonochemical route

A facile and low cost sonochemical technique was developed to synthesize oleic coated superparamagnetic magnetite (Fe3O4) nanoparticles. A combination of precipitation of ferrous chloride and ultrasonic cavitation was employed to produce the magnetite nanoparticles. It was found that ultrasonic cavitation can reduce the average particle size and heating temperature can also affected the size distribution of the produced nanoparticles. The FTIR analysis showed that the oleic acid molecules were chemisorbed onto the Fe3O4 nanoparticles as a carboxylate. The oleic coated magnetite nanoparticles with the size of 3-11 nm and the highest magnetization of 34.38 emu/g were fabricated by this technique.

Magnetite-based nanobioplatform for site delivering Croton cajucara Benth essential oil

Surface coating magnetic nanoparticles can be realized using organic moieties, such as essential oil (EO) extracted from Croton cajucara Benth leaves, a common plant from the Brazilian Amazon region successfully used for infusion in popular medicine. Although, there are reports in the literature indicating the protective and healing actions of the EO on gastric lesions, the inclusion of the magnetic core to control (targeting and retaining) the MNPs in specific sites can improve the performance of the EO molecules for the treatment of gastric disorders. Therefore, in this work, we report on fabrication and characterization of surface-coated magnetite nanoparticles (MNPs), aiming thermal-assisted site delivering EO. Firstly, oleic acid (OA) coated MNPs (sample M1) were fabricated using a thermal decomposition route. Secondly, the OA-coated MNPs were dressed with EO (sample M2). Meanwhile, x-ray diffraction and transmission electron microscopy data confirmed formation of spherically-shaped magnetite core while successful single OA coating and double OA + EO coating of MNPs was confirmed by infrared spectroscopy and thermogravimetric analysis (TGA). TGA results indicated release of the EO at ∼50 °C, whereas the OA is released only above ∼380 °C. Blocking (TB) and irreversible (TIRR) temperatures of samples M1 (TB = 210 K; TIRR = 210 K) and M2 (TB = 35 K; TIRR = 215 K) were assessed from magnetic measurements data analysis. In sample M2, the difference TB-TIRR (180 K) was related to inhomogeneous partial shifting of OA molecules by EO molecules whereas the remarkable reduction of MS with respect to sample M1 was assigned to a dead surface layer dominated by ferrous ions in low-spin state. Moreover, the lower TB value we have found in sample M2 (∼35 K) indicates negligible particle-particle interactions due to the successful double coating (OA plus EO) of the MNPs, in contrast to that obtained in sample M1. In sample M2 weakening of particle-particle interaction warrants superparamagnetic properties which can be used to obtain magnetic resonance image and for guiding the MNPs to targeting sites using gradients of external magnetic field. Therefore, the combination of the improved magnetic properties plus the detachment of EO at ∼50 °C (while keeping stable the OA coating) via magnetohyperthermia makes the double coated system (sample M2) a very promising candidate for site delivering of EO to treat gastrointestinal disorders.

Low-Cost and Scaled-Up Production of Fluorine-Free, Substrate-Independent, Large-Area Superhydrophobic Coatings Based on Hydroxyapatite Nanowire Bundles.

To date, the scaled-up production and large-area applications of superhydrophobic coatings are limited because of complicated procedures, environmentally harmful fluorinated compounds, restrictive substrates, expensive equipment, and raw materials usually involved in the fabrication process. Herein, the facile, low-cost, and green production of superhydrophobic coatings based on hydroxyapatite nanowire bundles (HNBs) is reported. Hydrophobic HNBs are synthesised by using a one-step solvothermal method with oleic acid as the structure-directing and hydrophobic agent. During the reaction process, highly hydrophobic C-H groups of oleic acid molecules can be attached in situ to the surface of HNBs through the chelate interaction between Ca2+ ions and carboxylic groups. This facile synthetic method allows the scaled-up production of HNBs up to about 8 L, which is the largest production scale of superhydrophobic paint based on HNBs ever reported. In addition, the design of the 100 L reaction system is also shown. The HNBs can be coated on any substrate with an arbitrary shape by the spray-coating technique. The self-cleaning ability in air and oil, high-temperature stability, and excellent mechanical durability of the as-prepared superhydrophobic coatings are demonstrated. More importantly, the HNBs are coated on large-sized practical objects to form large-area superhydrophobic coatings.

PH mediated kinetics of assembly and disassembly of molecular and nanoscopic building blocks

Self-assembly occurs when building blocks of the system interact with one another through interactions existing between them. Proper temporal control of these interactions can lead to formation of transient self-assembled states. pH mediated self-assembly is one of the powerful tools to stabilize and destabilize structures consisting of different sized building blocks. Here we investigate the kinetics of pH triggered reversible transformation of two building blocks using a relaxation method, reversible vesicle–micelle transformation of oleic acid molecules and dispersion–aggregation of pH sensitive gold nanoparticles. We found significant differences in the characteristic times (two orders of magnitudes) between the disassembly processes—from an ordered structure to a less ordered structure (in the case of oleic acid molecules) or to single building blocks (in the case of nanoparticles)—and the self-assembly processes (bilayer formation or aggregation of nanoparticles). It can be explained by a sophisticated interplay between repulsive (electrostatic) and attractive (van der Waals) interactions.

Influence of nanodispersed modifications of magnetite powders on spray nozzle efficiency of diesel engine injector

The paper presents data on the impact of new environmental requirements relating to the quality of diesel fuel on the anti-wear properties of fuel. Anti-wear additive is proposed as a material for increasing the tribotechnical characteristics of diesel fuel. This additive consists of diesel fuel with micelles contained in it, formed on the basis of molecules of solid plasticity lubrication of iron oxide (Fe3O4) – magnetite, and with surrounding molecules of oleic acid (C18H34O2). The additive has low shear resistance and increased lubricity of diesel fuel when this additive is introduced into it.

Direct Sampling and Analysis of Atmospheric Particulate Organic Matter by Proton-Transfer-Reaction Mass Spectrometry.

We report on a new method for analyzing atmospheric submicrometer particulate organic matter which combines direct particle sampling and volatilization with online chemical ionization mass spectrometric analysis. Technically, the method relies on the combined use of a CHARON ("Chemical Analysis of Aerosol Online") particle inlet and a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS). Laboratory studies on target analytes showed that the ionization conditions in the PTR-ToF-MS lead to extensive fragmentation of levoglucosan and cis-pinonic acid, while protonated oleic acid and 5α-cholestane molecules remain intact. Potential problems and biases in quantitative and qualitative analyses are discussed. Side-by-side atmospheric comparison measurements of total particulate organic mass and levoglucosan with an aerosol mass spectrometer (AMS) were in good agreement. Complex and clearly distinct organic mass spectra were obtained from atmospheric measurements in three European cities (Lyon, Valencia, Innsbruck). Data visualization in reduced-parameter frameworks (e.g., oxidation state of carbon vs carbon number) revealed that the CHARON-PTR-ToF-MS technique adds significant analytical capabilities for characterizing particulate organic carbon in the Earth's atmosphere. Positive matrix factorization (PMF) was used for apportioning sources of atmospheric particles in late fall in Innsbruck. The m/z signatures of known source marker compounds (levoglucosan and resin acids, polycyclic aromatic hydrocarbons, nicotine) in the mass spectra were used to assign PMF factors to biomass burning, traffic, and smoking emission sources.

Modulation of the albumin–paraoxon interaction sites by fatty acids: Analysis by the molecular modeling methods

It is known that albumin can break the ester bonds in organophosphorus compounds (OPs). Amino acids responsible for esterase and pseudoesterase activity of albumin towards OPs are still not determined. It is assumed that Sudlow’s site I with residue Tyr150 exhibits the “true” esterase activity; and Sudlow’s site II containing residue Tyr411, a pseudoesterase one. Binding of fatty acids to albumin affects the efficiency of its interaction with xenobiotics; however, the effect of fatty acids on the interaction of albumin with OPs was not studied. The purpose of this work was to study the interaction of OPs with potential sites of albumin enzymatic activity and to examine the effect of fatty acids on the efficiency of such interaction using the molecular modeling methods by the example of paraoxon, a known inhibitor of acetylcholinesterase, and oleic acid. The structures of the protein complexes with paraoxon and oleic acid were determined by the molecular docking procedure; the conformational changes were calculated by the molecular dynamics method. It has been shown that sorption of oleic acid in one of the fatty acid-binding sites leads to the conformational changes in Sudlow’s sites I and II due to a “reversal” of the side chains of Arg410 and Arg257 residues by 90°. It has been found that this change in geometry reduces the affinity of Sudlow’s site I and increases the Sudlow’s site II affinity to paraoxon. The amino acid residue Ser193, which was previously identified as a site of possible albumin esterase activity, is not able to bind paraoxon efficiently. It is assumed that its activity can be affected by the interaction of the oleic acid molecules with other fatty acid-binding sites. It is hypothesized that the lesser toxicity of paraoxon compared to soman may be associated not only with its lower inhibitory activity against cholinesterases, but also with the increased affinity of paraoxon to albumin. It was concluded that albumin may serve as an alternative means of OP detoxification.

Disjoining Pressure in Partial Wetting on the Nanoscale.

Partial wetting on the nanoscale may result in the formation of sessile liquid nanodroplets on flat substrates. In this case, the molecular forces generate a strong interaction between nanodroplet interfaces. This interaction is expressed in the mean-field approximation by the disjoining pressure and determines an important deviation from the spherical cap shape of the nanodroplets. This deviation is observed on the atomic force microscopy images of sessile nanodroplets of oleic acid on glass. The disjoining pressure was manipulated by hydroxylation of the glass surface. This surface modification generated a strong negative disjoining pressure due to structural forces arising from the orientation of oleic acid molecules with their polar heads toward the substrate. As a result, the shape of oleic acid nanodroplets showed large deviations from the spherical cap shape, with the liquid-vapor interface tilting angle with respect to the plane substrate having a maximum (herein considered to be the contact angle) a certain distance from the substrate, followed by its decrease to zero at the droplet edge. The integration of the augmented Young-Laplace equation, where the dependence of the negative structural disjoining pressure on the interface separation distance was assumed to be an exponential decay, yielded height profiles of droplets in good agreement with the experiment.

New glycolipid biosurfactants produced by the yeast strain Wickerhamomyces anomalus CCMA 0358

In this work, biosurfactant production by several yeast strains was evaluated using different culture media. The best results were obtained with the strain Wickerhamomyces anomalus CCMA 0358 growing in a culture medium containing glucose (1g/L) and olive oil (20g/L) as carbon sources. This strain produced 2.6g of biosurfactant per liter after 24h of growth. The crude biosurfactant reduced the surface tension of water to values around 31mN/m, and its critical micelle concentration was 0.9mg/mL. This biosurfactant was characterized through mass spectrometry (MS), and nuclear magnetic resonance (NMR) as a mixture of two different glycolipids, comprising a sugar moiety linked to one or three molecules of oleic acid. To the best of our knowledge, these biosurfactants are structurally different from those previously reported. Furthermore, the crude biosurfactant exhibited antimicrobial activity against several microorganisms, including the pathogens Candida albicans, Escherichia coli, Staphylococcus epidermidis and Streptococcus agalactiae, which opens the possibility for its use in several biomedical applications.

Colloidal Nanocrystalline Semiconductor Materials as Photocatalysts for Environmental Protection of Architectural Stone

Rod-shaped TiO2 nanocrystals (TiO2 NRs), capped by oleic acid molecules (OLEA), were synthesized with controlled size, shape and surface chemistry by using colloidal routes. They were investigated for application as coating materials for preserving architectural stone of monumental and archaeological interest, in consideration of their self-cleaning and protection properties. For this purpose, two different deposition techniques, namely casting and dipping, were tested for the application of a nanocrystal dispersion on a defined stone type, as a relevant example of porous calcarenites, namely the Pietra Leccese, a building stone widely used in monuments and buildings of cultural and historic interest of the Apulia region (Italy). The physical properties of the stone surface were investigated before and after the treatment with the prepared nanostructured materials. In particular, colour, wettability, water transfer properties and stability of the coating were monitored as a function of time and of the application method. The self-cleaning properties of the TiO2 NRs coated surfaces were tested under simulated and real solar irradiation. The obtained results were discussed in the light of the specific surface chemistry and morphology of TiO2 NRs, demonstrating the effectiveness of TiO2 NRs as an active component in formulations for stone protection.

Inhibition by Multifunctional Magnetic Nanoparticles Loaded with Alpha-Synuclein RNAi Plasmid in a Parkinson's Disease Model.

Lewy bodies are considered as the main pathological characteristics of Parkinson's disease (PD). The major component of Lewy bodies is α-synuclein (α-syn). The use of gene therapy that targeting and effectively interfere with the expression of α-syn in neurons has received tremendous attention. In this study, we used magnetic Fe3O4 nanoparticles coated with oleic acid molecules as a nano-carrier. N-isopropylacrylamide derivative (NIPAm-AA) was photo-immobilized onto the oleic acid molecules, and shRNA (short hairpin RNA) was absorbed. The same method was used to absorb nerve growth factor (NGF) to NIPAm-AA to specifically promote neuronal uptake via NGF receptor-mediated endocytosis. Additionally, shRNA plasmid could be released into neurons because of the temperature and pH sensitivity of NIPAm-AA interference with α-syn synthesis. We investigated apoptosis in neurons with abrogated α-syn expression in vitro and in vivo. The results demonstrated that multifunctional superparamagnetic nanoparticles carrying shRNA for α-syn could provide effective repair in a PD model.

Experimental and simulation-based understanding of morphology controlled barium titanate nanoparticles under co-adsorption of surfactants

Well dispersed single-crystalline BaTiO3 nanoparticles with controlled morphologies were synthesized using a thermohydrolysis route. The nanoparticles were tuned from spherical to cubic upon changing the NaOH concentration under a critical molar ratio of oleic acid to hydrazine. Density functional theory (DFT) and molecular dynamics (MD) calculations indicated that hydrazine molecules adsorbed preferably on the Ti position of the Ti–O terminated surface; meanwhile, oleic acid molecules tended to adsorb on the Ba position of the Ba–O terminated surface. The added hydrazine changed the formation mechanism of BaTiO3 nanoparticles from an in situ growth to a dissolution–precipitation growth. Excellent dispersibility in aqueous solution was achieved for the BaTiO3 nanoparticles under the assistance of hydrazine. Meanwhile, a high-quality self-assembled film with a stable dielectric constant of 30 in the frequency range from 0 Hz to 1 MHz was prepared using the well dispersed BaTiO3 nanoparticles, providing a novel low-temperature route for the fabrication of perovskite films.