Mixture Of Oleylamine Research Articles

Structural Size Effect in Capped Metallic Nanoparticles

The surfactant used during a colloidal synthesis is known to control the size and shape of metallic nanoparticles. However, its influence on the nanoparticle (NP) structure is still not well understood. In this study, we show that the surfactant can significantly modify the lattice parameter of a crystalline particle. First, our electron diffraction measurements reveals that NiPt nanoparticles around 4 nm in diameter covered by a mixture of oleylamine and oleic acid (50:50) display a lattice parameter expansion around 2% when compared to the same particles without surfactant. Using high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDX) techniques, we show that this expansion can not be explained by crystal defects, twinning, oxidation, or atoms insertion. Then, using covered NPs in the 4-22 nm size range, we show that the lattice parameter evolves linearly with the inverse of the NP size, as it is expected when a surface stress is present. Finally, the study is extended to pure nickel and pure platinum NPs, with different sizes, coated by different surfactants (oleylamine, trioctylphosphine, polyvinylpyrrolidone). The surfactants induce lattice parameter variations, whose magnitude could be related to the charge transfer between the surfactant and the particle surface.

Tuning specific loss power of CoFe2O4 nanoparticles by changing surfactant concentration in a combined co-precipitation and thermal decomposition method

New synthetic approaches of nanoparticles (NPs) can be used for magnetic hyperthermia, destroying malignant cells without damaging healthy tissues. Here, a combination of co-precipitation and thermal decomposition techniques was employed to synthesize monodisperse CoFe2O4 NPs. A mixture of oleylamine and oleic acid with different concentrations was utilized as a surfactant, significantly changing magnetic, morphological and structural properties of the NPs. Increasing the surfactant concentration from 1 to 7.5 mmol resulted in maximum and minimum coercivity and saturation magnetization of 420.0 Oe 73.6 emu/g, and 67.2 Oe and 48.3 emu/g, respectively, arising from the prevention of agglomeration and reduction in crystallite size. The first-order reversal curve analysis was employed to clarify the role of the surfactant in magnetic distributions and detailed characteristics. The specific loss power of the NPs was found to be tuned for the different surfactant concentrations, achieving a maximum of 268.5 W/g at 7.5 mmol for CoFe2O4 NPs with enhanced superparamagnetic contribution in Néel and Brownian mechanisms. MTT assay of the NPs was also carried out, indicating their low cytotoxicity.

Selective syntheses of kuramite (Cu2SnS3) and petrukite (Cu3SnS4) phases of copper tin sulphide, and their electrochemical and photocatalytic properties

Semiconductor materials of the type Cu–Sn–S (CTS) have recently been the focus of intense research due to their unique optical and thermoelectric properties. Their properties are also tunable by varying reaction parameters such as precursor concentration, solvent chemistry and reaction temperature. In this study, two phases of CTS: Cu2SnS3 and Cu3SnS4, were synthesized by the co-thermolysis of two dithiocarbamate complexes through the tuning of reaction temperature and solvent type. Cu2SnS3 nanoparticles with average crystalline size of 13.1 nm and band gap energy of 1.16 eV were synthesized in oleylamine at 220 ̊C, while Cu3SnS4 nanoparticles with average size of 12.3 nm and band gap energy of 1.57 eV was obtained in a mixture of oleylamine and dodecanthiol at 180 ̊C. The electrochemical and photocatalytic properties of the two CTS phases were further studied, with the Cu2SnS3 phase showing better properties compared to the Cu3SnS4 phase. The ability to achieve phase selectivity in synthesizing CTS with different crystal structures and band gap energies in a facile solvothermal process could be valuable in developing semiconductor materials with unique properties.

Highly ordered CuSbS2 nanotube arrays: Controlled synthesis and electrochemical properties

CuSbS2 nanotubes (NTs) were prepared via a hot-injection method using an anodic aluminum oxide (AAO) template, and a mixture of oleylamine (OLA) and dichlorobenzene (DB) as solvent. Structural characterization of the powder indicated formation of high purity well-aligned CuSbS2 NTs with an average diameter of 200 nm and an average wall thickness of 40 nm. Optical and electrochemical characterizations indicated that the obtained CuSbS2 NTs exhibit p-type conductivity with a suitable band gap (1.53 eV), as well as valence band (VB), and conduction band (CB) positions, comparable to conventional materials utilized in solar cell.

Acid-Base Mediated Ligand Exchange on Near-Infrared Absorbing, Indium-Based III-V Colloidal Quantum Dots.

Colloidal quantum dots (QDs) made from In-based III-V semiconductors are emerging as a printable infrared material. However, the formulation of infrared inks and the formation of electrically conductive QD coatings is hampered by a limited understanding of the surface chemistry of In-based QDs. In this work, we present a case study on the surface termination of IR active III-V QDs absorbing at 1220 nm that were synthesized by reducing a mixture of indium halides and an aminoarsine by an aminophosphine in oleylamine. We find that this recently established synthesis method yields In(As,P) QDs with minor phosphorus admixing and a surface terminated by a mixture of oleylamine and chloride. Exposing these QDs to protic surface-active compounds RXH, such as fatty acids or alkanethiols, initiates a ligand exchange reaction involving the binding of the conjugate base RX- and the desorption of 1 equiv of alkylammonium chloride. Using density functional theory simulations, we confirm that the formation of the alkylammonium chloride salt can provide the energy needed to drive such acid/base mediated ligand exchange reactions, even for weak organic acids such as alkanethiols. We conclude that the unique surface termination of In(As,P) QDs, consisting of a mixture of L-type and X-type ligands and acid/base mediated ligand exchange, can form a general model for In-based III-V QDs synthesized using indium halides and aminopnictogens.

A New Approach to the Synthesis of Lead Sulfide Colloidal Quantum Dots in a Mixture of Oleylamine and Oleic Acid

A new approach to the synthesis of lead sulfide colloidal quantum dots has been proposed, which uses a mixture of oleic acid and oleylamine. Colloidal quantum dots of PbS with a long-wavelength excitonic peak in the range from 1.7 to 2.05 μm have been obtained. The effects of temperature, reaction time, and the ratio of lead and sulfur precursors on the spectral characteristics of PbS quantum dots obtained have been studied.

Anisotropic CuInSe2 nanocrystals: synthesis, optical properties and their effect on photoelectric response of dye-sensitized solar cell

CuInSe2 I–III–VI2 ternary semiconductor considered as one of the most promising semiconductor material which considers a very efficient solar energy conversion material. An organometallic pyrolysis method is used to prepare monodisperse CuInSe2 nanoparticles using a mixture of oleylamine, and trioctylphosphine (TOP) as capping materials. Controlling the particle shape dot, rods or flowers occurs via varying the reaction temperatures (160, 200, 220°C) respectively. The obtained particles have been characterized to determine the shape and size of CuInSe2 nanoparticles using HR-TEM and XRD. The optical and the electronic properties of these particles have been investigated and discussed in details. Then the different shapes of CIS nanoparticles (nanodots, nanorods, and nanoflowers) were introduced to the DSSC to study their effect on the optical switching properties. It was found that the nanoflowers provide better photovoltaic performance than the other shapes; since it reduces the settling time to 50 milliseconds after it was more than 17 second before adding CIS nanoparticles to the cells.

Thermal Stability of Oleate‐Stabilized Gd2O2S Nanoplates in Inert and Oxidizing Atmospheres

AbstractCapping ligands play an important role in the chemistry of nanoparticles synthesized with organic surfactants. This is relevant to a number of device applications where heating may cause major modifications of crystalline nanoparticles including amorphization, surface rearrangements or sintering. Ultrathin monodisperse Ln2O2Sx oxysulfide nanoparticles (Ln=lanthanide) obtained in a mixture of oleylamine, oleic acid and 1‐octadecene show promising luminescence and light absorption properties. In view of applications, one open question concerns the thermal behavior and the role of the ligands on the thermal reactivity of the nanoparticles. In this report, we show that the thermal stability of Gd2O2Sx nanocrystals is limited because of their non‐stoichiometric composition and strongly depends on the annealing atmosphere. The sintering temperature of the nanoparticles is lower in air than in inert atmosphere because of a rapid degradation of the ligands. Annealing the nanoparticles in air enables removing the ligands without altering the nanocrystals structure. The decomposition of the Gd2O2Sx nanocrystals in inert atmosphere exhibits a complex multi‐step behavior that was precisely modeled. This work gives a comprehensive description of the stability conditions of lanthanide oxysulfide nanoparticles. It establishes the conditions for their practical use and opens the way to major improvements of the surface activity of Ln2O2S nanoparticles and related nanocrystals.

Advances in the Synthesis and Long‐Term Protection of Zero‐Valent Iron Nanoparticles

AbstractCore@shell Fe@Fe3O4 nanoparticles (NPs) are synthesized via the thermal decomposition of iron pentacarbonyl (Fe(CO)5) in the presence either of oleylamine (OAm) or a mixture of OAm and oleic acid (OA). The heterostructured nanocomposites formed do so by a postsynthetic modification of isolated Fe seeds. This proves the versatility of the coating procedure and represents a significant advantage over previous work with Co seeds owing to the higher magnetic susceptibility, reduced toxicity, and excellent biocompatibility of Fe. Furthermore, the latter system allows the synthetic methodology to be developed from a two‐pot scenario where seeds are isolated then coated, to an easier and more efficient direct one‐pot scenario. The two‐pot method yields proportionately larger cores. However, in both cases, the monodisperse product reveals a carbonaceous interface between the Fe core and oxide shell. Meanwhile for the one‐pot synthesis, the OA:OAm ratio influences both the morphology and dispersity of the product. This is interpreted in terms of competing interactions of the ligands with the iron precursor. Superparamagnetism (SPM) is observed, and microscopic studies reveal oxidative stability of the Fe(0) cores achieved by either method for >6 months. It is proposed that the carbonaceous interface is critical to this sustained oxidative stability.

Synthesis, Spray Deposition, and Hot-Press Transfer of Copper Nanowires for Flexible Transparent Electrodes.

We report a solution-phase approach to the synthesis of crystalline copper nanowires (Cu NWs) with an aspect ratio >1000 via a new catalytic mechanism comprising copper ions. The synthesis involves the reaction between copper(II) chloride and copper(II) acetylacetonate in a mixture of oleylamine and octadecene. Reaction parameters such as the molar ratio of precursors as well as the volume ratio of solvents offer the possibility to tune the morphology of the final product. A simple low-cost spray deposition method was used to fabricate Cu NW films on a glass substrate. Post-treatment under reducing gas (5% H2 + 95% N2) atmosphere resulted in Cu NW films with a low sheet resistance of 24.5 Ω/sq, a transmittance of T = 71% at 550 nm (including the glass substrate), and a high oxidation resistance. Moreover, the conducting Cu NW networks on a glass substrate can easily be transferred onto a polycarbonate substrate using a simple hot-press transfer method without compromising on the electrical performance. The resulting flexible transparent electrodes show excellent flexibility ( R/ Ro < 1.28) upon bending to curvatures of 1 mm radius.

Solvent Effects on Growth, Crystallinity, and Surface Bonding of Ge Nanoparticles.

Solvent effects on the microwave-assisted synthesis of germanium nanoparticles are presented. A mixture of oleylamine and 1-dodecene was used as the reaction solvent. Oleylamine serves as a reducing agent in the synthesis while both molecules act as binding ligands. Increased concentrations of 1-dodecene in the solvent mixture were found to increase the size of the formed nanoparticles. Crystallinity was also dependent on the solvent mixture. Amorphous nanoparticles were obtained at lower 1-dodecene concentrations, whereas, at higher concentrations, particles contained crystalline and amorphous domains. 11-Methoxyundec-1-ene was synthesized to replace 1-dodecene in the reaction mixture for nuclear magnetic resonance (NMR) studies. 1H NMR of the reaction products shows that both solvent molecules in the system act as binding ligands on the nanoparticle surface. Nanoparticles were characterized using powder X-ray diffraction, scanning transmission electron microscopy, and spectroscopy techniques (Raman, UV-vis, FT-IR, and NMR).

Role of Localized States in Photoluminescence Dynamics of High Optical Gain CsPbBr3 Nanocrystals

AbstractTemperature‐dependent time‐resolved photoluminescence (TRPL) spectroscopy of high optical gain CsPbBr3 nanocrystals (NCs) films along with temperature‐dependent steady‐state absorption and photoluminescence (PL) spectra is studied. A red shift in the optical band edge and the corresponding PL peak is observed by lowering the temperature from room temperature, analogous to hybrid perovskite semiconductors. However, the faster PL decay of CsPbBr3 NCs film at a low temperature as compared to room temperature is in contrast with many other traditional colloidal quantum dots. The TRPL spectroscopy as a function of temperature suggests the presence of a red‐shifted (≈75 ± 15 meV) defect‐induced emission peak at longer times. Temperature‐dependent PL intensity study shows an Arrhenius type of character with two activation energies: ≈77 ± 18 and ≈12 ± 3 meV. A qualitative model is developed where interaction between the excitonic level and these observed localized states as a function of temperature can qualitatively explain the contrasting PL decay mechanism of CsPbBr3 NCs film. To ensure the quality of in‐house synthesized CsPbBr3 NCs with a mixture of oleylamine and octylamine ligands, the amplified spontaneous emission from CsPbBr3 NCs film as a planar waveguide medium is studied, which shows state‐of‐art optical gain coefficient of ≈51cm−1 and a loss coefficient of ≈15cm−1 at room temperature.

Synthesis of CuFeS2 Nanoparticles by One-pot Facile Method

Monodisperse copper-iron-sulfide (CuFeS2) nanoparticles as the infrared light absorbing material (chalcopyrite, 0.65 eV), were synthesized based on facile, one step heating up method, by dissolving of CuCl, FeCl3 and SC(NH2)2 as precursors in oleylamine (OLA) alone or in combination with oleic acid (OA) and 1-octadecene (ODE) as solvent. The phase, size, morphology, and size distribution were controlled by the reaction conditions and temperature. The CuFeS2 nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectrum and ultraviolet-visible-near infrared. The three main absorbance region was observed in the ultraviolet, visible and infrared as a hybridization of Fe 3d-S 3p among the valence band (Cu 3d-S 3p) and conduction band (Cu 4s-Fe 4s). Well controlled CuFeS2 triangular pyramidal along with semi-hexagonal and hexagonal shape (~ 20-25 nm) was obtained by using OLA or a mixture of OLA along with OA and ODE, respectively, with 210 °C heating up and 4 h annealing time.

Monodisperse Ag/Pd core/shell nanoparticles assembled on reduced graphene oxide as highly efficient catalysts for the transfer hydrogenation of nitroarenes

Addressed herein is a facile seed-mediated synthesis of Ag/Pd core/shell nanoparticles (NPs) and their assembly on reduced graphene oxide (rGO) to catalyze the transfer hydrogenation of nitroarenes to anilines using ammonia borane (AB) as a hydrogen donor under ambient conditions. Monodisperse Ag/Pd core/shell NPs with controllable Pd shell-thickness were synthesized by the means of thermal decomposition of palladium(II) bromide over as-prepared Ag NPs in the mixture of oleylamine and oleic acid at 220°C. As-synthesized Ag/Pd core/shell NPs were characterized by TEM, HR-TEM, XRD, XPS, UV–Vis spectroscopy and ICP-MS and then they were assembled on reduced graphene oxide (rGO). Next, rGO@Ag/Pd catalysts were tested in the transfer hydrogenation of nitroarenes in which ammonia borane (AB) was used as a hydrogen donor at room temperature. It was demonstrated that the thickness of the Pd shell has a significant effect on the catalytic activity of rGO@Ag/Pd catalysts and the 1.75nm Pd shell provided the highest performance in the transfer hydrogenation reactions. The rGO@Ag/Pd catalyzed transfer hydrogenation reactions were tested over a variety of nitroarenes (total 16 examples) and they were all converted to the corresponding aniline derivatives with high yields in 5–15min under ambient conditions.

Influence of co-ordinating and non-coordinating solvents in structural and morphological properties of Cu2ZnSnS4 (CZTS) nanoparticles

Copper zinc tin sulphide Cu2ZnSnS4 (CZTS) nanoparticles were synthesized using different solvents including 1-octadecene (1-ODE), oleylamine (OLAM), oleic acid (OLA) and 1-dodecanethiol (1-DDT). Pure oleylamine based synthesis of nanoparticles results formation of nearly spherical like particles, while the pure oleic acid and mixture of oleylamine and oleic acid lead to the formation of hierarchical microspheres and nanodisc like structures. In addition to different morphologies, 1-dodecanethiol (1-DDT) based synthesis of Cu2ZnSnS4 nanoparticles posses wurtzite structure while rest of them exhibit pure kesterite phase. Further, the low volume of oleylamine in the reaction system motivates formation of sheet like structure. The mechanism involved in this structural direction of the nanoparticles into various morphologies was discussed. The synthesized CZTS nanoparticles were characterized using XRD, SEM, TEM and ATR-FTIR.

Role of phosphine free solvents in structural and morphological properties of CuInSe2 nanoparticles

Copper indium di selenide (CuInSe2) nanoparticles were synthesized using a facile colloidal non-phosphine solvent strategy. Mixture of oleylamine (OLAM), oleic acid (OLA), 1-octadecene (1-ODE) with different proportions were employed as solvents and as well as capping agents. Influence of these solvents on the structure and morphological properties of the synthesized CuInSe2 NPs was analysed. It was found that the solvents considerably play important role on the final morphology of the nanoparticles. OLAM assisted synthesis of CuInSe2 nanoparticles results nanoplate like morphology whereas replacing certain volume of OLAM by OLA and 1-ODE provide a bunch of hierarchical structures. The optical bandgap of the synthesized nanoparticles vary with the nature of the solvents. XRD analysis of the synthesized nanoparticles confirms the presence of chalcopyrite structure. Raman analysis shows the appearance of peak at 171 cm−1 due to the A1 mode of CuInSe2. SEM analysis clearly reveals the influence of solvents on the determination of morphology of the synthesized nanoparticles. EDX and elemental mapping analysis shows presence of nearly stoichiometric composition which was dependent on the nature of solvents used.

Fast Near-Infrared Electrochromism of Redox-Active Plasmonic Copper Sulfide Nanoparticles

Metal nanoparticles absorb and scatter light strongly on the basis of resonance of free electron oscillation with incident light, which is denoted as localized surface plasmon resonance (LSPR). Especially, gold and silver nanoparticles are known to exhibit LSPR in the visible and near-infrared (NIR) regions and applied to sensors,1 photovoltaics and photocatalysis,2 and photochromic materials.3 The LSPR properties such as resonant wavelength and intensity depend significantly on particle size and shape, local refractive index, and interparticle distance. Those are also dependent on electron density of the nanoparticles, which can be controlled electrostatically.4-6 However, it is difficult to induce large changes in resonant wavelength and intensity by the electrostatic means. Here, we focus on plasmonic copper sulfide nanoparticles as an electrochromic material. Nanoparticles of copper sulfide, represented by Cu2-x S, have sufficient holes to exhibit LSPR in the NIR region.7 In addition, copper valence can be controlled reversibly by chemical redox reactions,8 suggesting that reversible electrochemical tuning of their LSPR properties is possible. However, such a redox reaction-based control of LSPR has not been reported so far. Covellite (CuS) nanoparticles were prepared by heating copper(I) chloride and elemental sulfur in a mixture of oleylamine and oleic acid under N2 atmosphere9 and deposited on an ITO electrode. The figure shows absorption spectra of the electrode at different potentials (vs. Ag|AgCl) in deuterated water containing 0.1 M Na2S. Broad absorption due to LSPR is observed in the NIR region at -0.6 V while that gradually disappears as the applied potential is shifted negatively, indicating that plasmonic copper(II) sulfide is reduced to non-plasmonic copper(I) sulfide.10 It is noteworthy that reductive disappearance and oxidative reappearance of LSPR can be repeated at least 12 cycles and the response time is a few seconds. These results indicate that copper sulfide nanoparticles can be applied to fast NIR electrochromic devices that are driven in a narrow potential range (~0.4V). 1. K. M. Mayer, J. H. Hafner, Chem. Rev. 2011, 111, 3828. 2. Y. Tian, T. Tatsuma, J. Am. Chem. Soc. 2005, 127, 7632. 3. Y. Ohko, T. Tatsuma, T. Fujii, K. Naoi, C. Niwa, Y. Kubota, A. Fujishima, Nat. Mater. 2003, 2, 29. 4. T. Ung, M. Giersig, D. Dunstan, P. Mulvaney, Langmuir 1997, 13, 1773. 5. A. H. Ali, R. J. Luther, C. A. Foss, Jr, Nanostruct. Mater. 1997, 9, 559. 6. H. Nishi, S. Hiroya, T. Tatsuma, ACS Nano 2015, 9, 6214. 7. J. M. Luther, P. K. Jain, T. Ewers, A. P. Alivisatos, Nature 2011, 10, 361. 8. P. K. Jain, K. Manthiram, J. H. Engel, S. L. White, J. A. Faucheaux, A. P. Alivisatos, Angew. Chem. Int. Ed. 2013, 52, 13671. 9. H. Nishi, K. Asami, T. Tatsuma, Opt. Mater. Express 2016, 6, 1043. 10. I. Kriegel, C. Jiang, J. Rodríguez-Fernandez, R. D. Schaller, D. V. Talapin, E. da Como, J. Feldmann, J. Am. Chem. Soc. 2012, 134, 1583. Figure 1

Synthesis of Pt-Ni Octahedra in Continuous-Flow Droplet Reactors for the Scalable Production of Highly Active Catalysts toward Oxygen Reduction.

A number of groups have reported the syntheses of nanosized Pt-Ni octahedra with remarkable activities toward the oxygen reduction reaction (ORR), a process key to the operation of proton-exchange membrane fuel cells. However, the throughputs of those batch-based syntheses are typically limited to a scale of 5-25 mg Pt per batch, which is far below the amount needed for commercial evaluation. Here we report the use of droplet reactors for the continuous and scalable production of Pt-Ni octahedra with high activities toward ORR. In a typical synthesis, Pt(acac)2, Ni(acac)2, and W(CO)6 were dissolved in a mixture of oleylamine, oleic acid, and benzyl ether, and then pumped into a polytetrafluoroethylene tube. When the solution entered the reaction zone at a temperature held in the range of 170-230 °C, W(CO)6 quickly decomposed to generate CO gas, naturally separating the reaction solution into discrete, uniform droplets. Each droplet then served as a reactor for the nucleation and growth of Pt-Ni octahedra whose size and composition could be controlled by changing the composition of the solvent and/or adjusting the amount of Ni(acac)2 added into the reaction solution. For a catalyst based on Pt2.4Ni octahedra of 9 nm in edge length, it showed an ORR mass activity of 2.67 A mgPt(-1) at 0.9 V, representing an 11-fold improvement over a state-of-the-art commercial Pt/C catalyst (0.24 A mgPt(-1)).

CdS nanoparticles with high photocatalytic property synthesized by a new liquid–liquid method

CdS nanoparticles with high uniformity have been synthesized through a new liquid–liquid approach, using dimethyl sulfoxide and the mixture of oleyl amine and oleic acid as separate solvents, more convenient inorganic cadmium salt as cadmium source, and sulfur powder as sulfur source. The process can be conducted under mild conditions. It is found that the initial Cd/S molar ratio of precursor plays important role in controlling particle size. Higher concentration of sulfur precursor results in the larger particle size. The obtained colloidal CdS nanocrystals show obvious absorption and fluorescence in visible light region. When using methylene blue as degradation agent, the obtained CdS nanoparticles exhibit high photocatalytic ability.

A new two-liquid-phase system to synthesize PbS nanoparticles with narrow size distribution

A new liquid–liquid system, employing dimethyl sulfoxide and the mixture of oleyl amine and oleic acid as separate solvents, inorganic lead salt as lead source, and sulfide as sulfur source has been developed to synthesize PbS nanoparticles with a narrow size distribution. The process can be conducted under mild conditions. The obtained PbS nanoparticles exhibit high crystallinity and uniformity. The initial Pb/S molar ratio of precursor has great effect on the particle size and optical properties of product. Larger proportion of sulfur precursor, which results in the larger particle size, is more likely to restraint crystal nucleation, rather than promote crystal growth.