Oleic Acid Surfactant Research Articles

Dicephalic ionic surfactants in fabrication of biocompatible nanoemulsions: Factors influencing droplet size and stability

The present work has been carried out to explore the potential of two novel ionic dicephalic-type surfactants, i.e., positively charged N,N-bis[3,3′-(trimethylammonio)propyl]-dodecanamide dimethylsulphate, C12(TAPAMS)2 and anionic disodium N-dodecyliminodiacetate, C12(COONa)2 for spontaneous formation of biocompatible and stable oil-in-water (o/w) nanoemulsions. Initially, we examined ternary phase diagrams of surfactant–oil–water (SOW) systems containing different ratios of C12(TAPAMS)2 or C12(COONa)2 as the surfactant entity (S), oleic acid, isopropyl palmitate or isopropyl myristate as the oil phase (O) and the water phase (W) by the titration method. Then, all obtained nanoemulsions were characterized by visual and microscopic observations, as well as dynamic light scattering (DLS) measurements of particle sizes and size distributions. Results of cryo-TEM and DLS showed that the studied droplets making up the nanoemulsions have a nearly monodisperse size distribution (DH<100nm, PdI<0.2). Backscattered profiles obtained by the turbidimetric technique proved high kinetic stability of the obtained systems whereas Doppler electrophoresis revealed their large positive or negative ζ-potential. In order to test the nanoemulsions biocompatibility under the surfactants concentration, cytotoxicity of the optimized formulations was evaluated in vitro upon two normal human skin cell lines, i.e., cutaneous keratinocytes (HaCaT) and gingival fibroblasts (HGF). The analyzed parameters – oil composition, surfactant type, and surfactant-to-oil ratio – were all found to influence the droplet size, charge and stability of the systems produced. Our results prove that the studied nanoemulsions, stabilized by dicephalic ionic surfactants, may provide new biocompatible colloidal systems, designated mainly for cosmetics, personal and household care products.

Separation via Flotation and Spectrometric Determination of Copper(II) in Environmental Samples using a Newly Synthesized Girard T Derivative

A simple, highly sensitive and selective spectrophotometric procedure was developed for the determination of copper(II) ions. The procedure is based on the reaction at pH 4-7 between the newly synthesized Girard T derivative N-{[(phenylamino)thioxo methyl] hydrazino carbonyl methyl}trimethyl ammonium chloride (PTHAC) and Cu(II) to form an intense green Cu(II):PTHAC (1:1) complex that floats quantitatively with oleic acid (HOL) surfactant. The different analytical factors affecting the flotation and determination processes were examined viz. pH, temperature, concentration of metal, ligand and HOL, etc. The Cu-PTHAC complexes were characterized by elemental analysis, infrared, mass and electronic spectral studies. The formed Cu(II)-PTHAC complex shows a constant and maximum absorbance at 650 nm in the aqueous and scum layers. Beers’ law is obeyed over the concentration rang 0.1-6 mg l-1 with a detection limit of 0.03 mg l-1 and molar absorptivities (at λmax 650 nm) of 0.27×104 and 0.20×105 l mol-1cm-1 in aqueous and surfactant layers, respectively. Sandell’s sensitivity is calculated to be 3.2×10-3 μg cm2 and the relative standard deviation (n=5) is <3.72%. The suggested procedure has been successfully applied to the analysis of copper in different natural waters and ore samples. Moreover, the flotation mechanism is recommended based on some physical and chemical studies of the solid complex isolated from the aqueous and scum layers.

Thermogravimetric study of the surfactant–diethanolamine–titanium isopropoxide system behavior

Mesoporous anatase TiO2 materials with specific surface areas between 70 and 110 m2 g−1 were prepared via sol–gel technique using surfactants oleic acid and Triton-X (TX), in the presence or absence of diethanolamine, in methanol. Surfactants like TX or oleic acid (OA), as well as a gelating and chelate agent like diethanolamine (DEA) are commonly used in TiO2 formation from a titanium isopropoxide solution. Thermogravimetric methods were applied in order to evaluate the effect of the addition of such molecules in a precursor suspension before TiO2 materials preparation. The in situ investigation of such systems showed that numerous interactions occur between large molecules such as TX and OA that attributed on both steric effects and hydrogen bond formation. Materials prepared through modified sol–gel technique seem to be stabilized through DEA addition in the precursor suspension.

Synthesis of &lt;I&gt;α&lt;/I&gt;-Fe&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Templates via Hydrothermal Route and Fe&lt;SUB&gt;3&lt;/SUB&gt;O&lt;SUB&gt;4&lt;/SUB&gt; Particles Through Subsequent Chemical Reduction

FeCl3–NH4H2PO4 system was employed to fabricate -Fe2O3 nanoparticles by a hydrothermal method. The results showed that the most important factors affecting the size and morphology of as-prepared -Fe2O3 particles were the reactant concentration and the molar ratio of iron precursor to additives, i.e., [Fe]/[H2PO4 ]. Besides -Fe2O3 rings and tubes, single-crystalline -Fe2O3 rods with controllable size were successfully fabricated by adjusting the [Fe]/[H2PO4 ] ratio. The formation mechanism for -Fe2O3 nanocrystals with different shapes was studied. In order to produce Fe3O4 particles (in ring, tube or rod shapes), the as-prepared -Fe2O3 particles were employed as templates. Phase conversion from hematite to magnetite was achieved via a chemical reduction method. In this reduction process, both surfactants (oleic acid) and protective gas (5% H2/95% Ar gas mixture) were used as reduction agents. The effect of oleic acid and H2 gas on the reduction process of -Fe2O3 particles was studied through a series of experiments. The results indicated that the chemical reduction method was convenient and feasible to reduce various hematite templates to corresponding magnetite nanostructures.

Silver Nanofluid Containing Oleic Acid Surfactant As Working Fluid In The Two-Phase Closed Thermosyphon (TPCT): A Thermodynamic Study

The effect of using a surfactant on heat transfer rates in a two-phase closed thermosyphon (TPCT) in an operating state was investigated. A TPCT was made from copper tubes with 7.5, 11.1, and 25.4 mm international diameters and aspect ratios of 5, 10, and 20 . The filling ratios chosen were 30, 50, and 80% with respect to the evaporator length. Three working fluids were investigated: a silver nanofluid with a concentration of 0.5 wt% containing 0.5, 1, and 1.5 wt% of oleic acid. The operating temperatures were 40, 50, and 60°C. This research reports the effect of the following dimensionless parameters on heat transport: , Pr, Bo, Ja, Pe, Co, Cd, Ar, Z, and Ku. It was further found that the filling ratio had no effect on the ratio of heat transfer rates in the vertical position, but the properties of the working fluid affected the heat transport. In addition, a correlation for predicting the heat flux for the two-phase closed thermosyphon in the vertical position was established.

Synthesis, characterization and biofunctionalization of magnetic gold nanostructured particles

Magnetic Fe3O4@Au nanocomposite, nanostructured particles were prepared by depositing gold onto seeds of superparamagnetic iron oxide nanoparticles (SPION). The particles were characterized by SEM, TEM, XRD, visible and near infrared spectroscopy, and magnetic measurements. They were also functionalized and employed as enzymatic carriers for electrochemical biosensing. The nanostructured particles showed an urchin-like, roughly spherical morphology whose surface was covered with nanometric protuberances. The average diameter of the particles could be controlled in the 100–500nm range by changing the concentration of surfactants (oleylamine and oleic acid) employed in the synthesis. XRD showed a preferential growth of {111} facets. 3-Mercaptopropionic acid was used to chemically modify the surface of the nanostructured particles and horseradish peroxidase was immobilized onto the gold surface. Attached enzymes showed good activity even after several cycles of magnetic collection, drying, and redispersion.

Experimental and First‐Principles Characterization of Functionalized Magnetic Nanoparticles

Magnetic iron oxide nanoparticles synthesized by coprecipitation and thermal decomposition yield largely monodisperse size distributions. The diameters of the coprecipitated particles measured by X-ray diffraction and transmission electron microscopy are between approximately 9 and 15 nm, whereas the diameters of thermally decomposed particles are in the range of 8 to 10 nm. Coprecipitated particles are indexed as magnetite-rich and thermally decomposed particles as maghemite-rich; however, both methods produce a mixture of magnetite and maghemite. Fourier transform IR spectra reveal that the nanoparticles are coated with at least two layers of oleic acid (OA) surfactant. The inner layer is postulated to be chemically adsorbed on the nanoparticle surface whereas the rest of the OA is physically adsorbed, as indicated by carboxyl O-H stretching modes above 3400 cm(-1). Differential thermal analysis (DTA) results indicate a double-stepped weight loss process, the lower-temperature step of which is assigned to condensation due to physically adsorbed or low-energy bonded OA moieties. Density functional calculations of Fe-O clusters, the inverse spinel cell, and isolated OA, as well as OA in bidentate linkage with ferrous and ferric atoms, suggest that the higher-temperature DTA stage could be further broken down into two regions: one in which condensation is due ferrous/ferrous- and/or ferrous/ferric-OA and the other due to condensation from ferrous/ferric- and ferric/ferric-OA complexes. The latter appear to form bonds with the OA carbonyl group of energy up to fivefold that of the bond formed by the ferrous/ferrous pairs. Molecular orbital populations indicate that such increased stability of the ferric/ferric pair is due to the contribution of the low-lying Fe(3+) t(2g) states into four bonding orbitals between -0.623 and -0.410 a.u.

Enhanced thermophysical properties of copper nanoparticles dispersed in gear oil

Stable and well dispersed Cu-gear oil (IBP Haulic-68) nanofluids having Cu nanoparticles volume concentration between 0.11 and 2% are prepared with oleic acid surfactant. Presence of agglomerated Cu nanoparticles in the prepared nanofluids is confirmed from Dynamic Light Scattering (DLS) data. Thermal conductivity and viscosity measurements are performed both as function of nanoparticle concentration and temperature between 10 and 80 °C. Thermal conductivity enhancement of 24% is observed with 2 vol% of Cu nanoparticle loading at room temperature. The formation of interfacial layer at the nanoparticle–liquid boundary and the ballistic transport of phonons across the percolating aggregates are believed to be responsible for the observed thermal conductivity enhancement. Viscosity of Cu (2 vol%)–gear oil nanofluids shows ∼71% enhancement at 30 °C. Newtonian behavior of gear oil changes to non-Newtonian behavior with the appearance of shear thinning for higher loading of Cu nanoparticles. Modified Krieger–Dougherty equation considering the role of aggregation predicts reasonably well Cu vol% dependence of viscosity of Cu-gear oil nanofluids and its temperature dependence is well accounted by the modified Andrade equation.

Surface functionalized LSMO nanoparticles with improved colloidal stability for hyperthermia applications

LSMO (La0.7Sr0.3MnO3) magnetic nanoparticles (MNPs) coated with double layer oleic acid (OA) surfactant are prepared to make a water based magnetic nanofluid for hyperthermia application. Various experimental techniques are used for bilayer coating analysis. The effect of the bilayer coating on magnetic properties is studied by superconducting quantum interface device (SQUID). Colloidal behaviour of coated MNPs in aqueous medium is studied by the zeta potential and dynamic light scattering. The effects of pH and ionic strength on the colloidal stability of the MNPs are studied in detail. For the bilayer-coated LSMO MNPs aggregation is not observed even in high ionic strength and at physiological pH (7.4). For making the nanofluid of the bilayer-coated MNPs the colloidal stability is studied in physiological media like phosphate buffer solution. Under induction heating experiment, hyperthermia temperature (42–43 °C) could be achieved by the bilayer-coated sample at a magnetic field of 168–335 Oe and frequency of 267 kHz. The bilayer OA coating can hinder the agglomeration of MNPs significantly and produce stable suspension with improved hyperthermia properties. The bilayer OA coating also improves the specific absorption rate (SAR) of LSMO MNPs from 25 to 40 W g−1.

A new approach to follow the formation of iron oxide nanoparticles synthesized by thermal decomposition

A novel way has been proposed to follow the formation of nanocrystalline magnetite. Iron oxide nanoparticles were synthesized by the thermal decomposition of Fe(acac)3 in the presence of oleic acid and oleylamine surfactants at high temperature. The species produced during the synthetic process are characterized through their effects on the proton nuclear magnetic relaxation of the reaction medium and their sizes. As shown by transmission electron microscopy, photon correlation spectroscopy and x-ray diffraction, the diameter of nano-objects increases when the time synthesis is longer. Magnetic properties evaluated by nuclear magnetic resonance (NMRD profiles, T1 and T2 measurements) were correlated with the size parameters.

One-pot synthesis of ultra-small cerium oxide nanodots exhibiting multi-colored fluorescence

CeO2 nanodots of diameter 2nm have been synthesized by the thermolysis of cerium acetate in diphenylether in the presence of an oleic acid surfactant. The surfactant coating enabled them to be easily dispersible in nonpolar solvents. The CeO2 dots exhibited size dependant optical properties such as a red shift in absorption and band gap. As a result, the surfactant coated CeO2 nanocrystals emit photons in the visible region with broad photoluminescence spectra resulting in multi-colored fluorescence, which originates from defects associated with CeO2 nanocrystals approaching molecular dimensions.

Surfactant Effects on Dispersion Characteristics of Copper-Based Nanofluids: A Dynamic Light Scattering Study

We present a study of powder agglomeration and thermal conductivity in copper-based nanofluids. Synthesis of the copper powders was achieved by the use of three different surfactants (polyvinylpyrrolidone, oleic acid, and cetyl trimethylammonium bromide). After careful determination of morphology and purity, we systematically and rigorously compared all three of the surfactants for the production of viable copper-based nanofluids using dynamic light scattering. Our results show that the use of surfactants during synthesis of copper nanopowders has important consequences on the dispersion of the powders in a base fluid. The oleic-acid-prepared powders consisted of small particles of ∼100 nm that did not change with the addition of dispersant. The CTAB-prepared powders exhibited the best dispersion characteristics, as they formed small particles of approximately 80 nm in the presence of SDBS. The thermal conductivity enhancement in our nanofluids exhibited a linear relationship with powder loading for an av...

Synthesis, characterization and photocatalytic evaluation of visible light activated C-doped TiO2 nanoparticles

We have demonstrated heterogeneous photocatalytic degradation of microcystin-LR (MC-LR) by visible light activated carbon doped TiO2 (C–TiO2) nanoparticles, synthesized by a modified sol–gel route based on the self-assembly technique exploiting oleic acid as a pore directing agent and carbon source. The C–TiO2 nanoparticles crystallize in anatase phase despite the low calcination temperature of 350 °C and exhibit a highly porous structure that can be optimized by tuning the concentration of the oleic acid surfactant. The carbon modified nanomaterials exhibited enhanced absorption in the broad visible light region together with an apparent red shift in the optical absorption edge by 0.5 eV (2.69 eV), compared to the 3.18 eV of reference anatase TiO2. Carbon species were identified by x-ray photoelectron spectroscopy analysis through the formation of both Ti–C and C–O bonds, indicative of substitution of carbon for oxygen atoms and the formation of carbonates, respectively. Electron paramagnetic resonance spectroscopy revealed the formation of two carbon related paramagnetic centers in C–TiO2, whose intensity was markedly enhanced under visible light illumination, pointing to the formation of localized states within the anatase band gap, following carbon doping. The photocatalytic activity of C–TiO2 nanomaterials was evaluated for the degradation of MC-LR at pH 3.0 under visible light (λ > 420 nm) irradiation. The doped materials showed a higher MC-LR degradation rate than reference TiO2, behavior that is attributed to the incorporation of carbon into the titania lattice.

Two step growth process of iron-platinum (FePt) nanoparticles

In this paper, FePt nanocrystals have been prepared by adding LiBEt3H to the phenyl ether solution of FeCl 2. 4H 2O and Pt(acac) 2 precursors in the presence of oleic acid and oleylamine surfactants and 1,2hexadecanediol as the reducing reagent at 195°C, followed by refluxing at 245°C by sol process. Similarly, Pt nanoparticles were made by adding 1, 2-hexadecanediol as the reducing reagent to the phenyl ether solution of Pt (acac) 2. The results of Transmission electron microscopy (TEM) images showed that 2 to 7 nm Pt nanoparticles are formed via one step growth whereas, bimetallic 4 nm magnetic FePt nanocryctals are formed by two step growth as core-shell with good uniformity in size and shape. The size measurement results indicated that the standard deviation of FePt nanoparticles improves to 8% because of two step growth process. In order to phase transition from fcc to L1 0 structure , the FePt nanoparticles were annealed at 750°C for 4 h. The structural properties of FePt nanoparticles were analyzed by XRD spectra. To prevent FePt nanoparticles from sintering, NaCl particles were used as the separating media. SEM and TEM observations of FePt show the salt-matrix FePt nanoparticles with size of 40 nm after annealing.

Properties of composite magnetic abrasive powders with surfactants

Magnetic abrasive powders produced by mechanical mixing of abrasives (electrocorundum, silicon and vanadium carbides) and iron powders in the presence of surfactants (oleic acid) and binding organics (epoxy resin) are proposed. The content of surfactants and binding organics does not exceed 8–10%. The dependence of the magnetic properties of composite powder on its abrasive content is studied. The effect of the type of abrasive on the cutting ability of the magnetic abrasive material and on the surface roughness is determined. The roughness (Ra) reached on steel 45 (HRC = 44–46) with the use of Fe–50% SiC abrasive is 0.08–0.12 μm.

Effect of Oleic Acid and Oleylamine Surfactants on the Size of FePt Nanoparticles

FePt magnetic nanoparticles have been synthesized by superhydride reduction of FeCl2 and Pt(acac)2 at high temperature. Adding superhydride (LiBEt3H) to the phenyl ether solution of FeCl2 and Pt(acac)2 in the presence of oleic acid, oleylamine, and 1,2-hexadecanediol at 190 ∘C, followed by refluxing at 245 ∘C, led to monodisperse 3.5 nm FePt nanoparticles. The effect of oleylamine and oleic acid surfactants on the nucleation and growth of FePt nanoparticles were studied. The size of Pt was controlled by oleylamine surfactant in nucleation stage. To prevent sintering of the FePt nanoparticles, oleic acid surfactant was used in growth stage. The energy dispersive spectroscopy results revealed that the particle composition was first Fe11Pt89 in nucleation stage and after adding superhydride the composition changed to Fe63Pt37 in growth stage. The structural and magnetic measurements indicated that the L10 structure of FePt nanoparticles is formed after annealing and the coercivity of superlattice FePt nanoparticles increases to 7.5 kOe after heat treatments.

Highly Luminescent and Quantum-Yielding CdSe/ZnS Core/Shell Quantum Dots Synthesized by a Kinetically Controlled Succession Route In 18DMA

Highly luminescent and quantum-yielding (QY) CdSe/ZnS core/shell quantum dots (CS QDs) were synthesised via a new succession route in a non-toxic solvent, N,N-Dimethyl-octadecyl-tertiary-amine(18DMA) at a mild temperature. The CS QDs were also proven to be as efficient in reaching high quantum yields (up to 74%) as their reported high-temperature synthesis with organic phosphine ligands. It was demonstrated that the synthesis temperatures directly determine the size by controlling the rate of the monomer diffusion and adsorption. It was also found that the amount of surfactant oleic acid determined the QY of the QDs, whereas it had little influence on the crystallisation.

Oleic-acid-coated CoFe2O4 nanoparticles synthesized by co-precipitation and hydrothermal synthesis

Oleic-acid-coated CoFe2O4 nanoparticles were synthesized by co-precipitation and hydrothermal synthesis. The coprecipitation of the nanoparticles was achieved by the rapid addition of a strong base to an aqueous solution of cations in the presence of the oleic acid surfactant, or without this additive. The nanoparticles were also synthesized by a hydrothermal treatment of suspensions of the precipitates, coprecipitated at room temperature in the presence of the oleic acid, or without it. The influence of the synthesis conditions, such as the valence state of the iron cation in the starting aqueous solution, the temperature of the treatment and the presence of oleic acid, on the particles size was systematically studied. X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) revealed that, although spinel forms at room temperature, a substantial amount of Co was incorporated within the secondary, feroxyhyte-like phase when the iron cation was in the 2+ state. In contrast, when iron was in the 3+ state, the spinel forms at elevated temperatures of approximately 60°C. The presence of the oleic acid further increased the formation temperature for the stoichiometric spinel. Moreover, the oleic acid impeded the particles’ growth and enabled the preparation of colloidal suspensions of the nanoparticles in non-polar organic solvents. The nanoparticles’ size was successfully controlled by the temperature of the synthesis in the region where superparamagnetism dominates to the region where mono-domain ferrimagnetism dominates the magnetic properties.

Formulation of LDL Targeted Nanostructured Lipid Carriers Loaded with Paclitaxel: A Detailed Study of Preparation, Freeze Drying Condition, and In Vitro Cytotoxicity

In the present study, cholesterol nanostructured lipid carriers with various oleic acid content loaded with paclitaxel (PTX) were prepared by solvent emulsification‐diffusion method using a Taguchi design. Size, zeta potential, entrapment efficiency, drug loading, and release percent of NLCs were measured. The results indicated that the most effective factors on the size were oleic acid content and surfactant percent. Zeta potential was more affected by the drug content. Drug to‐ lipid weight ratio was the most effective factor on entrapment efficiency and drug release from NLC. In the present work, the effect of lyophilization on the particle size and release properties of NLCs was also evaluated. The results revealed no differences between the characteristics of NLCs before and after freeze drying by using 25% w/w sorbitol as cryoprotectant. Cytotoxicity studies indicate that PTX associated with the NLC is also effective in HT‐29 cell lines and enters the cancer cells selectively through the LDL receptor endocytic pathway. The IC50 values of free PTX solubilized in Cremophor EL and NLC‐born PTX after 72 h exposure were 8.32 ± 1.35 ng/mL and 5.24 ± 0.96 ng/mL, respectively.

Improving the electron mobility of TiO2 nanorods for enhanced efficiency of a polymer–nanoparticle solar cell

The poly(3-hexyl thiophene):TiO2 nanorod (P3HT:TiO2) solar cell has a better thermal stability than the P3HT:PCBM solar cell; however, the former has a lower power conversion efficiency (PCE) than the latter. We would like to enhance the PCE of P3HT:TiO2 solar cell by improving the electron mobility of anatase TiO2 nanorods. Two novel approaches: (1) ripening and (2) boron doping for TiO2 nanorods were explored. TiO2 nanorods were synthesized first by sol–gel process in the presence of an oleic acid surfactant at 98 °C for 10 h. The size of the TiO2 nanocrystal is about 35 nm in length and 5 nm in diameter. The insulating oleic acid on the TiO2 nanorods was replaced by pyridine (as-synthesized TiO2) for good compatibility and charge transport between P3HT and TiO2 in the application of hybrid P3HT:TiO2 nanorod solar cells. The crystallinity of the as-synthesized TiO2 nanorods was increased through ripening (120 °C, 24 h) by using an autoclave reactor while the size of the nanocrystals was not significantly changed. Boron doped TiO2 nanorods (B-doped TiO2) were synthesized using the same sol–gel process of as-synthesized TiO2 nanorods but by replacing 0.7 at.% Ti with B using boron n-butoxide instead of titanium tetraisopropoxide. The UV-Vis spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses indicate the B is present in TiO2 nanorods as substitutional defects which can be either Ti–O–B or O–Ti–B bonding, with a B 1 s binding energy of 192.1 eV. The ripening process is more effective at increasing the crystallinity of TiO2 nanorods than boron doping, as shown by XRD and Raman spectroscopy. The electron mobility of the TiO2 nanorods is improved from 6.21×10−5 to 2.33×10−4 (cm2 V−1 s) and 5.27×10−4 (cm2 V−1 s) for ripened TiO2 and B-doped TiO2, respectively, as compared with as-synthesized TiO2. The PCE of P3HT:TiO2 solar cells was increased by 1.31 times and 1.79 times under A. M. 1.5 illumination for ripened and B-doped TiO2, respectively, as compared with as-synthesized TiO2. The B-doped TiO2 has the highest mobility and PCE, mainly due to the presence of partially reduced Ti4+ by boron atom with delocalized electrons.