Microemulsion Synthesis Research Articles

Synthesis of Nanostructured Catalytic Materials from Microemulsions

Since the 1980s [1,2], colloidal systems such as microemulsions (ME) have been widely investigated, especially for the synthesis of nanomaterials for various applications.[...]

A new one-pot reverse microemulsion synthesis of ZnS nanoparticle using olive oil as organic solvent and surfactant and their application in remove heavy metal ions

In current study, ZnS nanoparticles were successfully synthesized with the aid of C2H5NS and Zn(NO3)2·6H2O as the starting reagents in the presence of olive oil as surfactant and oil (organic solvent). Besides, the effects of preparation parameters such as magnetic stirring time and its rpm on the morphology of ZnS nanoparticles, removal of heavy metals (Hg+2, Pb+2) were studied by SEM images and batch adsorption mode. ZnS nanoparticles are synthesized by this method have more efficiency for remove heavy metal because of their modified surface (with olive oil).The as-synthesized products were characterized by several technics such as powder X-ray diffraction, scanning electronic microscopy, spectra energy dispersive analysis of X-ray (EDS), and ultraviolet–visible (UV–Vis) technic.

One-Pot Synthesis of Cy5-Encapsulated Photostable Fluorescent Silica Nanoparticles for Bioimaging

A new type of Cy5-encapsulated photostable fluorescent silica nanoparticles (FSNPs) bearing positive charges have been successfully fabricated by a reverse microemulsion synthesis in one-pot. The Cy5 dye containing four primary amines are embedded into silica via covalent bonds through a silane coupling agent (GPTMS), followed by co-condensation with tetraethylorthosilicate. The uniform-sized, spherical and monodispersed FSNPs have high fluorescence intensity and photostability. The FSNPs exhibit high stability, good biocompatibility as well as low cytotoxicity. These FSNPs can be internalized into live cells and thus fluorescently label the cells. This study provides a simple synthesis approach that can be applied to other water-soluble and amino-modified organic dye molecules for biological targeting and fluorescent cell imaging.

Effect of Metals Oxides Loading on the Modification of Microstructure and Phase Transformation of Nanocrystalline CeZrO2 Synthesized Using Water-in-oil-Microemulsion

In this paper, the microstructural and textural characteristics of a series of nanocrystalline CeZrFeO2 (CZF) loaded with different concentration of Fe were reported. Nanocrystalline CZF was synthesized at room temperature using water-in-oil microemulsion method. The microstructure and textural properties of CZF nanocrystal were investigated using dynamic light scattering, x-ray diffraction (XRD), and N2 adsorption–desorption analysis. The micelles size distribution of CZF samples, measured by dynamic light scattering, was found to be revealed almost similar trend of distribution pattern. More small size of micelles was formed at higher Fe concentration. The micelles were distributed in a narrow distribution size, in the range of 6 to 44nm. Xrd analysis proved that the face centered cubic of nanocrystalline CZF was successfully produced through the microemulsion synthesis, with the exposure of the samples at high calcination temperature for reduction was unnecessary. The influence of Fe loading on the modification of the microstructure and textural characteristics of CZF was clearly observed. Fe ions contributed in making the degree of crystal lattice shrinking and provided a larger surface area with the increasing of Fe concentration. XRD patterns of CZF tended to shift toward lower 2θ value with increasing Fe concentration which attributed to the replacement of Ce or Zr ions with the smaller Fe ions in Ce-Zr structure. The clearer effect of Fe loading was observed in modification of Ce-Zr textural. The surface area and average pores size of CZF increased with increasing Fe concentration, while the particle diameter decreased. All of CZF samples revealed the mesoporous profile (type IV) materials.

ChemInform Abstract: SnO2: A Comprehensive Review on Structures and Gas Sensors

AbstractReview: 886 refs.

Reverse Microemulsion Synthesis and Characterization of Nano Nickel Sulfide Catalyst for Residue Slurry-Phase Hydrocracking

Nano nickel sulfide catalysts (NSCs) were successfully prepared for residue slurry-phase hydrocracking, which were synthesized by precipitation reaction in cetyltrimethylammonium bromide (CTAB) or mixed-surfactant (CTAB and Tween-80)/1-butanol/toluene/water reverse microemulsion in the presence of NiCl2 as the nickel resource and (NH4)2S as the sulfiding reagent. The prepared catalysts were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Experimental data revealed that both the kind and content of surfactants play a significant role in the morphology and size of NSCs. The particle size and crystallinity of NSC increased by thermal sulfiding at 300 °C in Karamay vacuum gas oil (KLVGO). Optical micrographs showed that NSCs could be well-dispersed in Karamay atmospheric residue (KLAR) without obvious aggregation. On the basis of the lower yields of gas, atmospheric residue (AR), and coke, the NSCs showed higher catalytic activity than a conventional water/oil-soluble Ni catalyst. NSCs had excellent coke suppression performance (coke yield is less than 0.65 wt %), and the produced coke mainly dispersed in liquid products. With the decrease of NSC particle size, the coke suppression performance enhanced and the size of toluene-insoluble fraction in liquid products (TI-LP) decreased. NSCs provided location for coke generation and deposition during the slurry-phase hydrocracking process. The crystal form of NSCs dispersed in the TI-LP was Ni3S2, which was confirmed by XRD analysis.

Synthesis of Hollow Tadpole-Like Silica Particles

Hollow tadpole-like silica particles were successfully synthesized via the microemulsion synthesis method using polyvinylpyrrolidone (PVP), tetraethyl orthosilicate (TEOS), and sodium citrate as starting materials in the presence of isopropanol as a solvent. The effects of TEOS/ammonia (T/A) ratio, PVP molecular weight, synthesis temperature, and sodium citrate concentration on the morphology of particles were investigated. The results demonstrated that synthesis temperature has a vital effect on the morphology of particles. Also, microstructure analysis showed that the length of the silica rods was tunable in the range 1.2–5.2 µm. Control of the length was obtained by adjusting the synthesis temperature and PVP molecular weight. The transmission electron microscopy results clearly confirmed that the tadpole-like particles were surprisingly hollow and they provided an open side that was completely different from the previous reports. The inner diameter of the silica rods could be adjusted in the range 50–200 nm. The existence of such a considerable open side may be practically appreciated in many potential applications such as bio-immobilization.

Microemulsion synthesis and magnetic properties of hydroxyapatite-encapsulated nano CoFe2O4

Hydroxyapatite-encapsulated cobalt ferrite (CoFe2O4) nanopowders were synthesized by one step microemulsion method. The powders were characterized by X-ray Diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and vibrating sample magnetometer. TEM results showed that nanoparticles calcined at 700°C have core–shell morphology. It was found that the resultant phases, morphology and magnetic properties of the samples depend on calcining temperature. The synthesized nanoparticles showed a maximum saturation magnetization of 7.8emu/g with a wasp-waisted hysteresis loop. The magnetion was reduced by increasing calcining temperature to 900°C. This reduction is due to the reaction of cobalt ferrite with hydroxyapatite which leads to CaFe12(PO4)8(OH)12 phase.

Colloidal and microemulsion synthesis of rhenium nanoparticles in aqueous medium

Abstract Rhenium nanoparticles (Re NPs) were synthesized by simple colloidal and microemulsion methods in aqueous medium under air and inert atmosphere. Colloidal synthesis using PVP as protective agent and NaBH4 as reducing agent led to pseudo-spherical Re NPs with mean size in the range of 0.7–2.8 nm. The effect of the synthesis temperature, the reducing agent addition rate, and the capping and reducing agent to Re ratio on the particle size and particle distribution was studied. In the presence of air, the synthesis at 60 °C provided faster and more complete reduction, however reoxidation was observed once the reducing agent was consumed. The reoxidation was avoided removing the oxygen dissolved in the water medium by bubbling N2 or H2. The increase of the synthesis temperature in the range studied (10–80 °C) resulted in a higher mean particle size and a more heterogeneous particle size distribution. A slower addition rate of the reducing agent produced Re NPs with more homogeneous size, together with some reduction of the mean particle size. An increase in the amount of reducing agent at high temperature, 70–80 °C, resulted in the formation of agglomerates of large size, apparently formed by smaller nanoparticles. The increase of the PVP to Re molar ratio from 10 to 40 resulted in some narrowing of the particle size distribution. The synthesis of Re NPs was also achieved for a water-in-oil microemulsion system (n-heptane/AOT) under inert atmosphere using NaBH4 as reducing agent. The mean size (0.8–1.4 nm) and size distribution of the pseudo-spherical Re nanoparticles were found to be affected mainly by the water to surfactant ratio. Under all the conditions and synthesis procedure tested Re showed a trend to produce rather small nanoparticles in comparison to other metals.

Metallic Clusters: Theoretical Background, Properties and Synthesis in Microemulsions

Reducing the size from the bulk material to nanoparticles produces a scaling behavior in physical properties in the later ones, due to the large surface-to-volume fraction. By further size reduction, entering into the subnanometric cluster region, physical properties are largely affected by strong quantum confinement. These quantum size effects (HOMO-LUMO gap), the small size and the specific geometry award subnanometric clusters with totally new and fascinating properties, including cluster photoluminescence, enhanced catalytic activity, etc. In this review, we report an introduction to the physical properties of clusters based on the jellium model; the controlled synthesis by microemulsion methods and the catalytic properties in different areas as heterogeneous catalysis, photocatalysis or electrocatalysis among others.

Spectrally Resolved Dynamics of Synthesized CdSe/ZnS Quantum Dot/Silica Nanocrystals for Photonic Down-Shifting Applications

Photonic structures capable of luminescence down-shifting (LDS) have strong application potential in several areas of optoelectronics. Such structures can be formed by overcoating quantum dots (QDs) with integrable, transparent layers. In this paper, silica was grown on CdSe/ZnS QDs to form QD/silica nanocrystals (NCs) in a microemulsion synthesis process. The synthesized structures were structurally and optically characterized to understand the growth mechanism, luminescence properties, and the influence of process parameters on excitonic decay and lifetime. Process conditions were established to have single QDs at the centers of the silica particles. The effects of temperature, excitation duration, size of QDs, and type of ligands on decay dynamics were established. Temperature- and time-resolved excitonic decay study of QD/silica NCs suggested carrier-trapping at the QD/silica interface and the exciton-phonon coupling to be the two main nonradiative processes limiting the luminescence efficiency. The synthesized NCs displayed intense photoluminescence (PL) with slight decrease in lifetime. The PL efficiency of the NCs improved for longer illumination. The NC structures that safely embed QDs in transparent medium are good candidates for LDS applications in photovoltaic, imaging, and detection devices.

Improvement in conductivity and thermal stability of polystyrene with two-step reduced graphene oxide based nanocomposite Graphene /polystyrene

In insitu microemulsion synthesis, we have synthesized successfully nanocomposite based on polystyrene (PS) and two-step reduced graphene oxide sheets with heat and NaBH4 agent after they had been treated by monoglyceride. Resulted Nanocomposite has been better in electrical conductivity (approximately 2,01 × 10-2S / cm), thermal stability (increased about 120 oC) and physical properties (glass transition temperatureincreasesof over 6.40 oC, elastic modulus increases by 45 %) than the pure PS properties.

Effect of particle size on thermal decomposition of alkali metal picrates

Three alkali metal picrates, KPA, RbPA and CsPA, were prepared into three micron sizes by microemulsion synthesis, and their thermal decomposition behaviors were investigated by DPTA at different temperatures and by DSC at different heating rates. The smaller-sized picrate has greater gas emission and smaller kinetic and thermodynamic parameters than do its larger counterpart. It can be attributed to the decreasing particle size which leads to the high surface energy, the fast mass and heat transfer, and the increasing active sites on the reaction interface. The small size effect and surface effect cause the autocatalysis which reduces the activation energy and promotes the reaction activity. The particle size does not affect the reaction mechanism. However, the picrates with different central alkali metals exhibit different reaction mechanisms even though they are of the same size. This is because the central metal determines the bond energy and consequently affects the stability of picrate.

Reverse microemulsion synthesis and characterization of CaSnO3 nanoparticles

CaSnO3 nanopowders had been successfully synthesized via a reverse microemulsion method. The effects of hexadecyltrimethylammonium bromide and polyoxyethylene octyl phenyl ether as surfactants on the size and morphology of the particles were also investigated. The synthesized products were systematically studied by X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (DTA–TG), Fourier transform infrared spectroscopy (FTIR), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The results showed that the kind of surfactants has an important effect on the average size and morphology of the particles.

Cage-like effect in Au-Pt nanoparticle synthesis in microemulsions: a simulation study.

The different distributions of metals in bimetallic nanoparticles synthesized in microemulsions were studied by computer simulation. The simulations demonstrated that if the difference between the reduction potentials of both metals is about 0.15-0.3 V, the compartmentalization of the reaction media causes the accumulation of slower reduction reactants in the microemulsions droplets, which favours the chemical reaction like a cage effect: increasing the local concentration of the slower reduction metal salt gives rise to a faster reduction, so the differences in reduction rates of both metals are attenuated. A more coincidental reduction of both metals deeply affects the nanoparticle structure, causing a better mixed alloy. This effect will be more pronounced when the concentration is higher and the intermicellar exchange rate is faster. This means that for any fixed microemulsion the nanoparticle structure can be modified by changing the reactant concentration: the core can be enriched in the faster reduction metal by lower concentrations, and the shell can be enriched in the slower metal by higher concentrations. Based on these observations, this study suggests a route to help experimentalists better create nanoparticles with a pre-defined structure.

Microemulsion synthesis and electromagnetic wave absorption properties of monodispersed Fe3O4/polyaniline core–shell nanocomposites

Monodispersed Fe3O4/PANI core–shell nanocomposites were synthesized by microemulsion polymerization. Before the polymerization of aniline, Fe3O4 nanoparticles were prepared by thermal decomposition of iron acetylacetonate using benzyl alcohol as the solvent and were surface-modified by oleic acid. Then aniline monomer was polymerized on the surface of Fe3O4 nanoparticles by microemulsion polymerization with sodium dodecyl benzene sulfonate as the surfactant and ammonium persulfate as the oxidant. Fourier transform infrared (FT-IR) spectra indicated that the oleic acid was chemisorbed on the surface of Fe3O4 nanoparticles. Transmission electron microscopy (TEM) analysis showed that the oleic acid modified Fe3O4 nanoparticles had a better dispersity with a diameter around 10nm. The Fe3O4/PANI nanocomposites were monodisperse with Fe3O4 as the magnetic core and PANI as the conductive shell. The as-prepared Fe3O4/PANI nanocomposites showed a superparamagnetic behavior. The paraffin composites with 70wt.% Fe3O4/PANI powders provided good electromagnetic wave absorption performance (RL<−20dB) in the range of 10.01–16.98GHz with absorber thicknesses of 3–4mm. A minimum RL value of −25.40dB was observed at 10.52GHz with a thickness of 3mm.

Synthesis of β-Phase GeO2 Nanoparticles and their High Pressure Studies

We fabricated mono-dispersed β-quartz GeO2by microemulsion synthesis at room temperature. The obtained particles were 300 nm sized GeO2walnut and hollow waxberry shaped GeO2which were consisted of nanosphere with average size of 20 nm. The evolution of high pressure studies were devoted in a diamond anvil (DAC) cell by Angle Dispersed X-ray Diffraction (ADXD) at room temperature. A phase transformation of β-GeO2to amorphous GeO2was detected in walnut GeO2, while the waxberry GeO2was found to transform to monoclinic phase directly. It is strongly suggested that size effect played a key role in the high-pressure transformation from the amorphous and monoclinic phase. By fitting the compression data to the BirchMurnaghan equation of state, the bulk moduli of the walnut and waxberry shaped β-GeO2particles were determined to be 33±5, and 38±4 GPa with B0= 3, respectively.

Facile microemulsion synthesis of porous CuO nanosphere film and its application in lithium ion batteries

Porous CuO nanosphere films have been successfully prepared through post-heat treatment of Cu2(OH)2CO3 nanosphere films, which were formed on copper foil immersed in a water-in-oil (W/O) microemulsion. The electrochemical performance of the porous CuO nanosphere film as anode materials for lithium ion batteries indicates that at the current density of 0.1C, it exhibits higher initial coulombic efficiency (70.4%) and reversible discharge capacity (799.7mAhg−1 after 100cycles) than the CuO nanorod film on copper foil, which was obtained via aqueous solution oxidation reaction followed by post-heating in N2 flow. The excellent performance can be attributed to the novel porous nanosphere structure grown on the current collecting substrate, which could not only shorten the diffusion path of lithium ion and provide appropriate contact area between electrode and electrolyte, but also increase the electrical conductivity of the electrode. More generally, the strategy based on synthesis within confined reaction media, rather than direct synthesis in bulk solution, offers a new approach to the design of micro/nanostructured transition metal oxides grown on the current collecting substrate used as anodes in lithium ion batteries with enhanced electrochemical performance.

Polymer template-assisted microemulsion synthesis of large surface area, porous Li2MnO3 and its characterization as a positive electrode material of Li-ion cells

Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge–discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g−1 is obtained. When the acid-treated sample is heated at 300 °C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g−1. The rate capability study suggests that the sample provides about 150 mAh g−1 at a specific discharge current of 1.25 A g−1. Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.

Modified reverse microemulsion synthesis for iron oxide/silica core–shell colloidal particles

Iron oxide/silica core–shell colloidal particles were prepared by basic reverse microemulsion (RM) method and two modified RM methods. By basic RM method, maximum particle size obtained was mere 40 nm. For building photonic crystals working in the visible range, the colloidal particles must be larger than 100 nm. Thus two modified RM methods were used. By alcohol modified RM method, short chain alcohols were used as co-surfactant. The particle size rose to near 100 nm, but the core–shell structure was comparatively poor. By emulsifier pair modified RM method, the particle size leapt to over 200 nm and a narrow growth window was found favorable to enhance the stability and rigidity of the surfactants layers. The core–shell mechanism was also discussed and a new four-step mechanism was proposed.