Metal-surfactant Complexes Research Articles

The investigation of the binding ability between sodium dodecyl sulfate and Cu (II) in urban stormwater runoff

The simultaneous presence of heavy metals and surfactants in runoff induces complexation and ecological harm during migration. However, interactions between these pollutants are often overlooked in past studies. Thus, investigating heavy metal-surfactant complexes in runoff is imperative. In this work, Cu (II) and sodium dodecyl sulfate (SDS) were selected to investigate the interaction between heavy metals and surfactants due to the higher detected frequency in runoff. Through 1H NMR and FTIR observation of hydrogen atom nuclear displacement and functional group displacement of SDS, the change of SDS and Cu (II) complexation was obtained, and then the complexation form of Cu (II) and SDS was verified. The results showed that solution pH values and ionic strength had significant effects on the complexation of Cu (II). When the pH values increase from 3.0 to 6.0, the complexation efficiency of SDS with Cu (II) increased by 12.12% at low concentration of SDS, which may be attributed to the excessive protonation in the aqueous solution at acidic condition. The increase of ionic strength would inhibit the complexation reaction efficiency by 19.57% and finally reached the platform with concentration of NaNO3 was 0.10 mmol/L, which was mainly due to the competitive relationship between Na (I) and Cu (II). As a general filtering material in stormwater treatment measures, natural zeolite could affect the interaction between SDS and Cu (II) greatly. After the addition of SDS, the content of free Cu (II) in the zeolite-SDS-Cu (II) three-phase mixed system was significantly reduced, indicating that SDS had a positive effect on the removal of Cu (II) from runoff. This study is of great significance for investigating the migration and transformation mechanism of SDS and Cu (II) in the future and studying the control technology of storm runoff pollution.

Synthesis of nano-sized urchin-shaped LiFePO4 for lithium ion batteries.

In this article, the facile synthesis of sea urchin-shaped LiFePO4 nanoparticles by thermal decomposition of metal-surfactant complexes and application of these nanoparticles as a cathode in lithium ion secondary batteries is demonstrated. The advantages of this work are a facile method to synthesize interesting LiFePO4 nanostructures and its synthetic mechanism. Accordingly, the morphology of LiFePO4 particles could be regulated by the injection of oleylamine, with other surfactants and phosphoric acid. This injection step was critical to tailor the morphology of LiFePO4 particles, converting them from nanosphere shapes to diverse types of urchin-shaped nanoparticles. Electron microscopy analysis showed that the overall dimension of the urchin-shaped LiFePO4 particles varied from 300 nm to 2 μm. A closer observation revealed that numerous thin nanorods ranging from 5 to 20 nm in diameter were attached to the nanoparticles. The hierarchical nanostructure of these urchin-shaped LiFePO4 particles mitigated the low tap density problem. In addition, the nanorods less than 20 nm attached to the edge of urchin-shaped nanoparticles significantly increased the pathways for electronic transport.

Seed-mediated synthesis of ultra-long copper nanowires and their application as transparent conducting electrodes

Owing to a recent push toward one-dimensional nanomaterials, in this study, we report a seed-mediated synthetic strategy for copper nanowires (Cu NWs) production involving thermal decomposition of metal-surfactant complexes in an organic medium. Ultra-long Cu NWs with a high aspect ratio and uniform diameter were obtained by separating nucleation and growth steps. The underlying mechanism for nanowire formation was investigated, in addition, properties of the obtained Cu NWs were also characterized using diverse analysis techniques. The performance of resulting Cu NWs as transparent electrodes was demonstrated for potential application. This article can provide information on both new synthetic pathway and potential use of Cu NWs.

Surface engineered gold nanoparticles through highly stable metal–surfactant complexes

Monodispersed Au nanoparticles were synthesized by the reduction of Au-decyltrimethylammonium bromide (Au-DTAB), which was easily prepared via the reaction of HAuCl4 and DTAB. This Au-DTAB complex is highly stable in air and moisture, and suitable for large-scale synthesis of uniform-sized Au nanoparticles. The nanoparticles were characterized by transmission electron microscopy, optical absorption spectrometry, X-ray diffraction, and Fourier Transform infrared spectroscopy. The size of Au nanoparticles was controlled in the range of 5–10nm by changing the concentrations of reducing agent and Au precursor. The resulting Au nanoparticles were transferred to the aqueous phase after surface engineering using multidentate polymeric ligands with multiple imidazole functional groups. Polymeric imidazole ligands (PILs) demonstrated enhanced binding stability with the Au surface, and overcame the disadvantage of multidentate thiol ligand systems which have oxidative cross-linking and the formation of disulfide bonding. The colloidal stability of surface engineered Au nanoparticles with PILs was investigated by dynamic light scattering (DLS) characterization.

Structure Characterization and Properties of Metal-Surfactant Complexes Dispersed in Organic Solvents.

This work describes the synthesis and characterization of metal-surfactant complexes. Dioctyl sulfosuccinate and dodecylbenzenesulfonate are associated with multivalent aluminum, iron, and vanadium ions using an ion exchange reaction. The metal complexes are dispersible in various organic solvents. In solvents with low polarity, the complexes form "inverse" macromolecular structures with multiple metal ions. In contrast, in alcohols, the complex size is reduced, showing a more disperse conformation. The metal and surfactant ions are still strongly bonded to each other in all the solvents probed. Small-angle X-ray and neutron scattering (SAXS and SANS) are used to characterize the structures. Simultaneous fitting of neutron and X-ray scattering spectra is performed in order to obtain an accurate description of the system. Scattering results are also validated by performing molecular dynamics (MD) simulations. The conductive and electrochemical properties of the complexes in solution are also evaluated. The dispersion of metal-organic complexes significantly increases electric conductivity, and some metal ions in the core of the complexes are shown to be electrochemically active in apolar solvents.

Thermal analysis, decomposition kinetics, and molecular modeling of transition metal (Fe, Co) surfactant complexes

A detailed thermal analysis of iron and cobalt surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3 +]2 has been carried out using Thermogravimetric (TG) analysis at different heating rates (i.e., 5, 10, 15, and 20 °C min−1). It has been observed that iron complex decomposes by a different mechanism compared to other transition metal complexes. Metal is the final product instead of metal oxide. Combining the results from our previous study, first row transition metal complexes exhibit an order of stability in agreement with the famous Irving Williams series, i.e., the apparent activation energy, E for thermal decomposition varies as: E Fe > E Co < E Ni < E Cu > E Zn (exception being iron because of different decomposition mechanism). Thermal decomposition parameters have been measured and compared using the multiple heating rate method of Flynn–Wall–Ozawa. Further, molecular modeling calculations have been carried out to compare the experimental TG data with theoretical computations for the synthesized metal surfactant complexes. Minimum energy optimized structures for the complexes have been obtained using Gaussian software.

Self-aggregation and solution behavior of synthesized organo transition metal (Co, Fe, Zn) amphiphilic complexes

We report the aggregation behavior for the complexes of first row transition elements namely iron, cobalt, and zinc. Metal surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3+]2 have been synthesized, keeping the hydrophobic dodecyl chain same. The change in the thermal and redox behavior upon metal complexation with conventional surfactants has been analyzed. The influence of different metal ions on the physicochemical and solution properties of metal surfactant complexes has been explored by using techniques such as conductivity, surface tension, ultrasonic velocity, and cyclic voltammetry. The different metal surfactant complexes synthesized show different properties, which can be attributed solely to the change of metal (namely, cobalt, iron, and zinc) only.

Self aggregation and solution behavior of copper and nickel based surfactants

Introduction of new functionalities into the structure of amphiphilic molecules has always been the focus of widespread interest. An attempt has been made to study the self aggregation properties of surface active complexes involving hydrophilic transition metal (viz., nickel and copper) in the head group, and hydrophobic alkylammonium tail. The systems have been characterized by spectroscopic, thermal and physicochemical techniques, to gain an insight into the inter relationship between the structure, and surfactant properties. The two surfactants synthesized have similar tails; however, the different transition metal ions show a significant effect on the colloidal behavior. The cmc values of the metal surfactant complexes have been estimated using cyclic voltammetry, conductivity, surface tension, ultrasonic speed and density measurements. Thermogravimetric analysis and physicochemical studies certify that a minute change in the structure leads to a significant change in the properties of these surfactants.

Thermogravimetric evaluation of decomposition kinetics of metal surfactant complexes

Thermal behavior of various synthesized transition metal surfactant complexes of the type [M(CH3COO)4]2−[C12H25NH3 +]2 where M: Cu(II), Ni(II), Co(II) has been investigated using Thermogravimetric Analysis (TGA). It was found that pyrolytic decomposition occurs with melting in metal complexes, and that metal oxides remain as final products. The activation energy order obtained, E Cu > E Ni > E Co, could be explained on the basis of size of transition metal ion and metal ligand bond strength. In the course of our investigation on the decomposition of complexes, we carried out a comparative study of different measurement and calculation procedures for the thermal decomposition. A critical examination was made of the kinetic parameters of non-isothermal thermoanalytic rate measurement by means of several methods such as Coats–Redfern (CR), Horowitz–Metzger (HM), van Krevelen (vK), Madhusudanan–Krishnan–Ninan (MKN), and Wanjun–Yuwen–Hen–Cunxin (WYHC). The most appropriate method among these was determined for each decomposition step according to the least-squares linear regression. It was found that the results obtained using CR method differ considerably from HM method, as the former method involves a lot of approximations and is not much reliable. The application of thermoanalytic techniques to the investigation of rate processes has also been discussed.

Colloidal metal nanoparticles as a component of designed catalyst

Recent advances in the synthesis of colloidal metal nanoparticles of controlled sizes and shapes that are relevant for catalyst design are reviewed. Three main methods, based on colloid chemistry techniques in solution, i.e., chemical reduction of metal salt precursors, electrochemical synthesis, and controlled decomposition of organometallic compounds and metal-surfactant complexes, are used to synthesize metal nanoparticles. Their catalytic activity and selectivity depend on the shape, size and composition of the metal nanoparticles, and the support effect, as shown for many reactions in quasi-homogeneous and heterogeneous catalysis. A specially designed type of thermally stable catalysts--"embedded" metal catalysts, in which metal nanoparticles are isolated by porous support shells so that metal sintering is effectively avoided at high temperatures, are also introduced. The utilization of pre-prepared colloidal metal nanoparticles with tuned size, shape and composition as components of designed catalysts opens up new field in catalysis.

Synthesis of Monodisperse Spherical Nanocrystals

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Synthesis of Monodisperse Spherical Nanocrystals

Much progress has been made over the past ten years on the synthesis of monodisperse spherical nanocrystals. Mechanistic studies have shown that monodisperse nanocrystals are produced when the burst of nucleation that enables separation of the nucleation and growth processes is combined with the subsequent diffusion-controlled growth process through which the crystal size is determined. Several chemical methods have been used to synthesize uniform nanocrystals of metals, metal oxides, and metal chalcogenides. Monodisperse nanocrystals of CdSe, Co, and other materials have been generated in surfactant solution by nucleation induced at high temperature, and subsequent aging and size selection. Monodisperse nanocrystals of many metals and metal oxides, including magnetic ferrites, have been synthesized directly by thermal decomposition of metal-surfactant complexes prepared from the metal precursors and surfactants. Nonhydrolytic sol-gel reactions have been used to synthesize various transition-metal-oxide nanocrystals. Monodisperse gold nanocrystals have been obtained from polydisperse samples by digestive-ripening processes. Uniform-sized nanocrystals of gold, silver, platinum, and palladium have been synthesized by polyol processes in which metal salts are reduced by alcohols in the presence of appropriate surfactants.

Mesostructured Silica Films with Metal Oxide Doped Pore Walls

ABSTRACTIn this work, novel approaches towards mixed metal oxide mesostructured films by a combination of evaporation-induced self-assembly and sol-gel processing of deliberately designed precursor molecules (from single source precursors to metal-surfactant complexes) are reported. The focus lies on Ti-oxide doped silica films with in a wide range variable Ti to Si ratios. The ligand-assisted templating based on metal-coordinated surfactants allows a selective positioning of the metal species in the silica wall which is advantageous for many catalytic applications. For the synthesis of these metal doped silica films, a non-ionic polyether-based surfactant (Brij56) was simultaneously used as the structure-directing agent and ligand for the respective metal-alkoxide, such as titanium isopropoxide. These metal-coordinated surfactants were mixed with a prehydrolyzed silica-solution based on tetraethoxysilane and ethanol and spin- or dip coated. In the second approach, a single source precursor for network formation based on 3-acetyl-6-trimethoxysilylhexane-2-one that was coordinated to titanium isopropoxide was synthesized. This precursor was either used as network forming agent in the presence of tetraethoxysilane and a surfactant (Brij56) or in combination with the metal-coordinated surfactant to broaden the accessible range of the Si:Ti ratios. The final films were characterized by XRD, XPS, nitrogen porosimetry and TEM.

Synthesis and characterization of orthorhombic, 2d-centered rectangular and lamellar iron oxide doped silica films

Iron oxide doped silica films and powders with highly ordered mesostructures of extraordinary temperature stability (up to 1000 °C) and iron loading of up to 6 atom% were produced by the use of novel iron alkoxide-coordinated surfactants. Wormhole-like, 2d-centered rectangular, orthorhombic and lamellar mesostructures were obtained by variation of the molar ratios of the metal–surfactant complexes. The influence of a subsequent heat treatment was studied by GI-SAXS, TEM, XRD, and nitrogen sorption techniques. The molecular composition of the films was studied by XPS and EXAFS.

Sorption Competition and Mechanisms of Desorption of Heavy-Metal Contaminants from Kaolin Clays Using Surfactant Solutions of Sodium Dodecyl Sulfate

A new mechanism based on a combination of acid-base interactions and hydro- phobic attraction at the solid-water interface is proposed for the surfactant-enhanced washing of heavy-metal-contaminated kaolin clays. Batch washing mechanisms for kaolin clay suspension, which was chosen as a model system for the environmentally friendly separation of copper (Ⅱ) and nickel (Ⅱ) metal ions, were studied with respect to the sorption competition at the clay interface via acid-base interactions and hydrophobic attraction, transformation of the micellar structure of sodium dodecyl sulfate surfactants, and desorption of heavy metals off the particle surfaces. The sorption onto kaolin clays of heavy-metal ions from single- and binary-metal solutions was observed through isotherm tests conducted at 20℃ and pH 6.5. In binary systems, the adsorption of acidic Cu(superscript 2+) onto the basic surface sites of kaolin clays is four times higher than that of Ni(superscript 2+). Metal-spiked kaolin clays containing both 0.447 mg copper/g kaolin and 0.137 mg nickel/g kaolin were washed out less than 1% of each metal contaminant with water alone at pH 6.5. Experimental results of metal removal were compared under variation of operating conditions, including the surfactant dose, pH, temperature, time, and solid content. A single washing at pH 6.5 with 5000 mg/L of sodium dodecyl sulfate above the critical micelle concentration (cmc) could remove 60% of the nickel and 23% of the copper from kaolin clays. The combination of 5000 mg/L of basic surfactant and 10 mg/L of nitric acid at pH 5.5 was able to remove 63% of the nickel and 60% of the copper. It was then postulated that a three-step washing mechanism for metal removal using the sodium dodecyl sulfate surfactants could proceed through adsorption of basic, anionic surfactant molecules from dissociating micelles onto metal-spiked kaolin clay and self-reassembling into micelles via hydrophobic attraction. In this way, metal-surfactant complexes would be formed with acidic metal cations via acid-base interactions, followed by desorption of micellar metal-surfactant complexes from the kaolin clay into the solution via electrostatic repulsion.

Direct Synthesis of Highly Crystalline and Monodisperse Manganese Ferrite Nanocrystals

Highly crystalline and monodisperse manganese ferrite nanocrystals were synthesized via the thermal decomposition of metal-surfactant complexes followed by mild chemical oxidation. Particle sizes could be varied from 5 to 13 nm by changing the experimental parameters. The uniformity of the nanocrystals was demonstrated by the formation of two- and three-dimensional superlattices. Electron diffraction, X-ray diffraction, and high-resolution TEM images confirmed the high crystallinity of the manganese ferrite nanocrystals. Elemental analysis and energy-dispersive X-ray spectroscopy confirmed that the molar ratio of Mn:Fe was 1:2. The nanocrystals were found to exhibit the typical behaviors of magnetic nanocrystals with the characteristic narrow energy barrier distributions of magnetic anisotropy, confirming the uniformity of the nanocrystals.

Designed synthesis of atom-economical pd/ni bimetallic nanoparticle-based catalysts for sonogashira coupling reactions.

We synthesized Ni/Pd core/shell nanoparticles from the consecutive thermal decomposition of metal-surfactant complexes. The nanoparticle catalyst was atom-economically applied for various Sonogashira coupling reactions.