Reverse Micelle Method Research Articles

Extraction and Purification of Chymotrypsin from the Intestine of Red Perch (Sebastes marinus) Using Reverse Micelles: Optimization of the Forward Extraction Step

Fish processing waste can be used to produce valuable by-products, such as chymotrypsin which has application in the food, leather, chemical and clinical industries. Chymotrypsin is an endopeptidase secreted by the pancreatic tissues of vertebrates and invertebrates. Reverse micelles (RM) systems consisting of AOT/isooctane were used for the purification of chymotrypsin from crude aqueous extract of red perch intestine. The effects of pH and AOT concentration in the forward extraction step on the Total Volume (TV), Volume Ratio (VR), protein concentration (Cp), enzyme activity (AE), Total Activity (TA), Specific Activity (SA), Purification Fold (PF) and Recovery Yield (RY) were studied. The TV decreased with increases in the AOT concentration and decreases in pH. The VR slightly decreased with increases in the pH but was not affected by the AOT concentration. The highest AE, Cp, SA, PF and RY were achieved with pH 7.0 and 20 mM AOT concentration. Higher amount of surfactant formed a stable oil-water mixture structure and caused difficulties in the backward extraction step. When the pH was increased from 6.0 to 7.0 and/or the AOT concentration was increased from 1 to 20 mM, the AE, Cp, SA and RY initially increased and then decreased with further increases in the pH and/or the AOT concentration. The increases in these parameters were due to the increased electrostatic interaction between the net charge on the surface of protein molecule and reverse micelles inner layer charge caused by increasing pH and the increased reverse micelles structure caused by increased AOT concentration. The decreases in these parameters were due to the decreased net charge on protein molecules which weakened the electrostatic interaction between chymotrypsin and reverse micelles. The AE, TA, SA, PF and RY obtained with RM method were higher than those obtained with Ammonium Sulphate (AS) method by 2.16-2.82 folds.

Synergistic catalysis of Au-Co@SiO2 nanospheres in hydrolytic dehydrogenation of ammonia borane for chemical hydrogen storage

Core–shell structured Au-Co@SiO2 nanospheres have been synthesized using a reverse-micelle method. During heat treatment in vacuum, multiple Au-Co nanoparticles (NPs) embedded in SiO2 nanospheres (Au-Co@SiO2-RT) merged into single Au-Co NPs in SiO2 (Au-Co@SiO2-HT), resulting in a size increase of the Au-Co NPs. The Au-Co@SiO2-HT nanospheres showed better catalytic activity than that of Au-Co@SiO2-RT. The higher catalytic activity of Au-Co@SiO2-HT could be attributed to the decrease in the content of basic ammine by the decomposition of metal ammine complexes during the heat treatment. Compared with their monometallic counterparts, the bimetallic Au-Co NPs embedded in a SiO2 nanosphere show higher catalytic activity for the hydrolytic dehydrogenation of NH3BH3 to generate a stoichiometric amount of hydrogen at room temperature for chemical hydrogen storage. The synergistic effect between Au and Co inside the silica nanospheres plays an important role in the catalytic hydrolysis of NH3BH3.

Sol–gel zirconia nanopowders with α-cyclodextrin as organic additive

Nanomaterials present unique structural and physicochemical properties due to their ultra fine size of particles that make them very useful in many domains. The most spectacular applications of nanosized zirconia include ceramics, piezoelectrics, refractories, pigments, solid electrolytes, oxygen sensors, catalysts, ultrafiltration membranes, and chromatography packing materials. Nanostructured zirconia powders can be prepared using various methods, such as sol–gel process, coprecipitation, hydrothermal synthesis, and reverse micelle method. The aim of the present work was to prepare zirconia nanopowders through the sol–gel method, using α-cyclodextrin as organic additive and to establish its influence on the structural and textural properties of the obtained product. A white, amorphous ZrO2 powder containing α-cyclodextrin was prepared, which became a crystalline, stable one, after removing the organic matter by thermal treatment. The resulted nanocrystalline powder contains both monoclinic and tetragonal zirconia phases and is very stable. It presents a relatively reduced tendency of agglomeration of particles and contains closed pores which are embedded in the zirconia matrix. The zirconia powders were characterized using the following methods: thermal analysis, IR spectroscopy, UV–vis spectroscopy, X-ray diffraction, and electron microscopy (SEM, TEM, and HRTEM coupled with SAED).

Influence of processing methodology on the structural and magnetic behavior of MgFe2O4 nanopowders

Three different wet chemistry routes namely reverse micelle, citrate gel and co-precipitation methods were used to synthesize magnesium ferrite nanopowders. The synthesized spinel was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Raman spectroscopy techniques, transmission electron microscopy (TEM) and Superconducting Quantum Interference Device magnetometry (SQUID). The gel combustion method yield comparatively pure crystalline phase of MgFe2O4 and relatively higher saturation magnetization of 22.7emu/g. The material synthesized using co-precipitation method yield other phases in addition to the targeted phase. The average diameter of nanoparticles obtained from reverse microemulsion route was about 19.6±2nm, and for those obtained from gel combustion and co-precipitation route are highly agglomerated. The reverse micelle process produces fine nanosized particles compared with other methods reported in the literature. Superconducting Quantum Interference Device (SQUID) magnetometer reveals that the ferrite nanopowders obtained from the reverse micelle, gel combustion and co-precipitation route exhibit superparamagnetism. The selection of MgFe2O4 synthesis method largely depends on the targeted applications and desired properties. The results reported in this study are useful for establishing a simple method for the preparation of MgFe2O4 nanopowders.

Effect of Mn low concentration on the optical properties of ZnO nanocrystals

ZnO and ZnO:Mn nanocrystals synthesized via reverse micelle method. The size, band gap, Urbach energy, optical constants and penetration depth of nanocrystals were calculated by UV-vis spectroscopy data. The surface morphology was studied with the use of scanning electron microscope (SEM). Moreover the samples exposed to Gama ray source of 60 Co and their thermoluminescence properties were

A novel fluorescent nanoparticle composed of fluorene copolymer core and silica shell with enhanced photostability

A variety of fluorescent nanoparticles have been developed for demanding applications such as optical biosensing and fluorescence imaging in live cells. Silica-based fluorescent nanoparticles offer diverse advantages for biological applications. For example, they can be used as labeling probes due to their low toxicity, high sensitivity, resolution, and stability. In this research, a new class of highly fluorescent, efficient nanoparticles composed of a newly synthesized poly[di(2-methoxy-5-(2-ethylhexyloxy))-2,7-(9,9-dioctyl-9 H-fluorene)] (PDDF) core and a silica shell (designated as PDDF@SiO 2) were prepared using a simple reverse micelle method, and their fluorescent properties were evaluated using methods such as single-dot photoluminescence measurements. The enhanced photostability of the particles and their potential applications for bioanalysis are discussed in this article. The morphology, size, and fluorescent properties for prepared PDDF@SiO 2 nanoparticles were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and photoluminescence spectroscopy. The prepared particles size, which was approximately 60 nm, resulted in an excellent colloidal stability in a physiological environment. The photobleaching dynamics, total numbers of emitted photons (TNEP) and statistical measurements of individual nanoparticles were observed using laser scanning fluorescence microscopy to assess the structure and photostability of PDDF@SiO 2 nanoparticles. Additionally, PDDF@SiO 2 nanoparticles were used in cell toxicity and permeation tests for biological analyses, demonstrating a great potential for use as powerful, novel materials within the emerging fields of biosensing and biomedical engineering.

A detailed study of physical properties of ZnS quantum dots synthesized by reverse micelle method

In this article, zinc sulfide nanocrystal quantum dots were synthesized by reverse micelle method using polyvinyl pyrrolidone as surfactant. The various crystallite properties of these nanocrystals such as, size, d-spacing, lattice parameter, microstrain, intrinsic stress, X-ray density, specific surface area, dislocation density, porosity, and agglomeration number have been analyzed using X-ray diffraction spectrum. The transmission electron microscopy was used to calculate the size and monitoring morphology of the nanocrystals, while the scanning electron microscopy was utilized to investigate the surface morphology of nanoclusters. The various optical properties of zinc sulfide quantum dots such as absorption coefficient, extinction coefficient, optical band gap energy, Urbach energy, and threshold wavelength have been analyzed using UV-visible data. The photoluminescence was used to study the emission spectra of produced ZnS quantum dots. Moreover, Furrier Transform-Infrared studies revealed that ZnS quantum dots are pure.

Sol–gel reverse micelle preparation and characterization of N-doped TiO 2: Efficient photocatalytic degradation of methylene blue in water under visible light

A series of N-substituted titanium (IV) 2-ethyl-1,3-hexanediolate Ti(C 32H 68O 8) precursor were synthesized by the sol–gel reverse micelle (SGRM) method. The ethylene diaminetetraacetic acid (Na 2EDTA) has been used as a source of nitrogen n species. The obtained solids were calcined at 500 ̊C for 1 h to obtain photoactive phases. The effect of nitrogen content (N/Ti = 0.025; 0.03; 0.05 atomic ratios) is examined. The materials were characterized by XRD, BET, TG/DTA and UV–vis reflectance spectroscopy (DRS). Photocatalytic decolourisation of methylen blue (MB) in aqueous solution was carried out using nano, doped TiO 2. Experimental results revealed that N/Ti = 0.05 atomic ratio N-doped TiO 2 required shorter irradiation time for complete decolourisation of MB than pure nano TiO 2 and commercial (Degussa P-25) TiO 2.

Heterogeneous immunoassay for soy protein determination using nile blue-doped silica nanoparticles as labels and front-surface long-wavelength fluorimetry

A long-wavelength fluoroimmunoassay for the determination of soy protein is reported for the first time using a conjugate composed of anti-soy protein antibodies bound to nile blue-doped silica nanoparticles (NPs). These NPs have been synthesized by a reverse-micelle microemulsion method and functionalized by using 3-(aminopropyl)triethoxysilane (APS) and 3-(trihydroxysilyl)propyl methylphosphonate (THPMP) to avoid NP aggregation. The tracer has been obtained by linking the functionalized NPs with anti-soy protein antibodies previously oxidised with sodium periodate. The immunoassay has been developed in 96-well microplates using a heterogeneous competitive format with antibody capture. Soy proteins are immobilised onto the wells and bovine serum albumin is added to block the surface, thus minimising non-specific binding. After washing, the microplates can be stored ready to use. At the analysis time, soy protein standards or sample and tracer are added and incubated and, after the corresponding washing and drying steps, the fluorescence is measured onto the solid surface at λ ex 620 and λ em 680 nm. The method features a dynamic range of 0.1–10 mg L −1 and a detection limit of 0.05 mg L −1. The precision of the method has been assayed at 0.5 and 5 mg L −1 protein concentrations, obtaining the values of relative standard deviation of 9.6% and 6.1%, respectively. This new immunoassay has been applied to the analysis of food containing soy protein and the results obtained have been compared to those provided by a commercial ELISA kit with no statistically differing results. Also, a recovery study has been performed, providing percentages in the range of 81.5–111.0%.

Analysis of the Amino Acids of Soy Globulins by AOT Reverse Micelles and Aqueous Buffer

The 7S and 11S globulins from soybean proteins using reverse micelle and aqueous buffer extraction methods were characterized by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and scanning electron microscope (SEM), and their amino acid compositions were also evaluated. SDS-PAGE did not show electrophoretic differences between 7S and 11S globulin subunits with two extraction methods. SEM analysis showed that the AOT reverse micelle processing of 7S and 11S globulins induced a reduction of droplet size. Some individual amino acid contents of 7S and 11S globulins using two extraction methods were different, some were similar. In all the samples, the glutamic acid, aspartic acid, and leucine were the dominant amino acids while the cystine and methionine were the first-limiting amino acids. The proportion of essential amino acids to the total amino acids (E/T) of the 7S globulin from aqueous buffer and reverse micelles was similar. While significant differences were obtained in the proportion of E/T of the 11S globulin.

Magneto-Controlled Graphene Immunosensing Platform for Simultaneous Multiplexed Electrochemical Immunoassay Using Distinguishable Signal Tags

A novel flow-through multiplexed immunoassay protocol for simultaneous electrochemical determination of carcinoembryonic (CEA) and alpha-fetoprotein (AFP) in biological fluids was designed using biofunctionalized magnetic graphene nanosheets (MGO) as immunosensing probes and multifunctional nanogold hollow microspheres (GHS) as distinguishable signal tags. The probes were fabricated by means of co-immobilization of primary anti-CEA (Ab(1)) and anti-AFP (Ab(2)) antibodies on the Fe(3)O(4) nanoparticle-coated graphene nanosheets (MGO-Ab(1,2)). The reverse-micelle method was used for the synthesis of distinguishable signal tags by encapsulation of horseradish peroxide (HRP)-thionine and HRP-ferrocene into nanogold hollow microspheres, respectively, which were utilized as labels of the corresponding GHS-Ab(1) and GHS-Ab(2). A sandwich-type immunoassay format was employed for the online detection of CEA and AFP by coupling a flow-through detection cell with an external magnet. The assay was based on the catalytic reduction of H(2)O(2) at the various peak potentials in the presence of the corresponding mediators. Experimental results revealed that the multiplexed electrochemical immunoassay enabled the simultaneous monitoring of AFP and CEA in a single run with wide working ranges of 0.01-200 ng mL(-1) for AFP and 0.01-80 ng mL(-1) for CEA. The detection limits (LODs) for both analytes at 1.0 pg mL(-1) (at 3s(B)) were very low. No obvious nonspecific adsorption and cross-talk were observed during a series of analyses to detect target analytes. Intraassay and interassay coefficients of variation were <10%. Importantly, the methodology was evaluated for the analysis of clinical serum specimens, receiving a good correlation between the flow-through multiplexed electrochemical immunoassay and an electrochemiluminescence method as a reference.

Analysis on the characteristic properties of PEDOT nano-particle based on reversed micelle method

Based on the study of a new type of conducting polymer poly (3, 4-ethylenedioxythiophene) (PEDOT), we focussed on the preparation and characteristics of PEDOT nanoparticles made by reversed micelle method. Moreover, we deeply investigated the optical, electrical and the thermal stability of PEDOT nanoparticles. The main results are as follows: the small-sized PEDOT nanoparticles were prepared and utilized by different methods, such as ultraviolet/visible (UV-Vis) spectroscopy, Fourier-transform infrared (FTIR) spectrum, scanning electron microscopy(SEM) and so on. The results show that the amount of oxidizer, ultrasonic treatment, polymerizing temperature and doping degree can influent morphology, electrical ability and gas sensitivity of PEDOT nanoparticles. The Bragg peaks of nanoparticles at 6.7°, 12.7°, 25° were observed by XRD and the better orientation of molecular chain was attributed to the effective doping of toluene-p-sulfonic acid, which also resulted in an enhancement of thermal stability of nanoparticles than conventional PEDOT.

Preparation of blue-emitting CaMgSi 2O 6:Eu 2+ phosphors in reverse micellar system and their application to transparent emissive display devices

Blue-emitting Eu 2+-doped CaMgSi 2O 6 phosphors were prepared by the reverse micelle method. The resultant particles were nanocrystalline with a grain size of about <300 nm and exhibited a characteristic blue emission spectrum centered at 445 nm induced by the oxygen coordinated Eu 2+ ions. By using the corresponding nanophosphors followed by the formation of a uniform phosphor layer, we have demonstrated the mini-sized transparent plasma-discharge panels and investigated their luminance characteristics. Phosphor coated panel is properly transparent, ≥65%, at the visible wavelength region and illuminates a characteristic blue emission under Ne/Xe plasma discharge conditions. Thus, we can obtain a fast decaying, robust blue-emitting silicate phosphor layer under excited plasma radiation for upcoming emissive display devices like as transparent and three-dimensional plasma display panels.

Synthesis, optical, structural and thermal characterization of Mn 2+ doped ZnS nanoparticles using reverse micelle method

Mn 2+­doped ZnS nanoparticles have been prepared through the reverse micelles method using sodium bis (2–ethylhexyl) sulfosuccinate (AOT) as a surfactant. The prepared particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectrometer (FT-IR), UV–vis spectrometry, photoluminescence (PL), electron spin resonance (ESR) and thermogravimetry–differential scanning calorimetry (TG–DSC).

Bi-Functional Oxygen Electrodes Using LaMnO3/LaNiO3 for Rechargeable Metal-Air Batteries

Carbon supported-electrocatalysts are principally used as catalytic layers for air electrodes of metal air batteries. However, these types of air electrodes are problematic because the carbon support can be oxidized to water soluble organic compounds under anodic polarization for a charge process. In this study, we have investigated to use LaNiO3 as a possible electrode material to replace the carbon support because LaNiO3 has both high electric conductivity and high oxygen evolution activity. LaNiO3 was prepared by a reverse homogeneous precipitation method, and then LaMnO3, which is active for oxygen reduction reactions, was successfully loaded onto the LaNiO3 by using a reverse micelle method. LaNiO3 had a much higher stability against anodic polarization as compared to carbon support. The LaMnO3/LaNiO3 composite electrode showed excellent bi-functional oxygen reduction/evolution activity in an alkaline solution and this makes it a highly potential candidate for use in rechargeable metal-air batteries.

Synthesis and characterization of gold cubic nanoshells using water-solubleGeO2 templates

Size-tunable GeO2 nanocubes were initially prepared by a modified sono-assisted reverse micelle method and thenfunctionalized with an amino-terminated silanizing agent. Subsequently, gold decoratedGeO2 nanocomposites wereprepared at pH ≈ 7 and 80 °C. It was found that well-dispersed gold nanoparticles onGeO2 nanocubes could be obtained only if gold salt is abundant to favor simultaneous,homogeneous nucleation of gold particles. Additional gold ions were reduced onto theseattached ‘seed’ particles accompanied by synchronous dissolution of water-solubleGeO2 cores, resulting in gold hollow cubic shells. TheGeO2 nanocubesand Au/GeO2 nanocomposites as well as gold hollow cubic shells were characterized by transmissionelectron microscopy, scanning electron microscopy, x-ray diffraction and UV–visiblespectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peakat above 900 nm, which renders it quite promising in biochemical applications.

Durability of Carbon-Supported La-Mn-Based Perovskite-Type Oxides as Oxygen Reduction Catalysts in Strong Alkaline Solution

The durability of carbon-supported La-Mn-based perovskites for the oxygen reduction reaction in strong alkaline solutions was investigated. Carbon-supported perovskite-type oxide nanoparticles were prepared by using a reverse micelle method. The durability of the carbon-supported LaMnO3 nanoparticles was compared with that of carbon-supported LaMnO3 prepared by the mechanical mixing of LaMnO3 with the carbon support. As a result, the durability of the carbon-supported LaMnO3 nanoparticles was less than that of the carbon-supported LaMnO3 prepared by the mixing method due to a difference in the surface area of LaMnO3, which has an effect on the oxygen reduction reaction. In order to improve the durability of the carbon-supported LaMnO3 nanoparticles, Ca and Fe were substituted at the A-sites and B-sites of the perovskite lattice, respectively. As a result, it was found that the partial substitution of Ca and Fe is effective in improving the durability of LaMnO3 under cathodic polarization in strong alkaline solutions. In particular, the substitution of Ca at the A-site not only improved the durability of the oxide but also enhanced the oxygen reduction activity owing to an increase in the average valence state of the B-sites of the perovskite lattice.

Solid state morphology and band gap studies of ETS-10 supported CdS nanoparticles

Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar roperties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) hν]2 and hν. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10.

Structural and Magnetic Properties of CoPt@Au Core-Shell Nanoparticles Prepared Under Ambient Pressure

In this study, cobalt platinum alloy-core/gold-shell (CoPt@Au) nanoparticles are prepared by reverse micelle method under ambient pressure, and investigated by X-ray diffraction, transmission electron microscopy (TEM), ultraviolet-visible absorption spectra, and superconducting quantum interference device (SQUID) analyses. Cobalt platinum alloy (CoPt) nanoparticles are synthesized via chemical assembly, and achieved by reducing 0.1 M aqueous metal salts confined in the polar portions of inverse micelles of cetyltrimethylammonium bromide (CTAB) with borohydride. Gold-coated nanocomposites are prevented CoPt oxidation and allowed the samples to be manipulated without additional precautions to prevent oxidation. X-ray diffraction shows that the pattern of CoPt is hidden under the pattern of gold. TEM image reveals that the core-shell structure is obviously observed and the average size of CoPt@Au nanoparticles is about 6∼7 nm. The absorption band of CoPt@Au nanoparticles shifts to a longer wavelength and broadens relative to that of the pure gold. The results of magnetization for CoPt@Au nanoparticles reveal that they are super-paramagnetic, and the blocking temperatures is 75 K. In addition, there is an weak ferromagnetism observed in the results of magnetization for CoPt@Au nanoparticles under −1000 Oe ∼ 1000 Oe at 5K, and the coercive fields is 20 Oe.

Synergistic effects of transition metal substitution in conversion electrodes for lithium-ion batteries

Different solid solutions in the FexCo1−xC2O4·2H2O system have been prepared in the form of nanoribbons by a reverse micelles method. The orthorhombic crystallographic structure differs from the monoclinic massive products FeC2O4·2H2O and CoC2O4·2H2O. The dehydration process is studied by thermal analysis to prepare the anhydrous solid solution oxysalts, in which the nanoribbon-shaped particles are preserved and a porous system is developed. Anhydrous mixed oxalates are used for the first time as high-capacity lithium storage materials with improved rate performance, and display synergistic effects as compared with the end members. Fe0.75Co0.25C2O4 displays a reversible capacity ca. 600 mA h g−1 at 5C rate with a very good capacity retention after 75 cycles by a hybrid mechanism. The solids display faradaic capacities due to a novel conversion reaction that produces nanodispersed transition metals, which is responsible for the high energy density, and a capacitive response that leads to high power densities in Li-ion batteries. The low temperature synthesis of these materials makes them an inexpensive option for this purpose.