Reverse Microemulsion Method Research Articles

Pt-Au nanoparticles on graphene for oxygen reduction reaction: Stability and performance on proton exchange membrane fuel cell

Pt and Pt-Au nanoparticles supported on reduced graphene oxide (rGO) were synthesized by reverse microemulsion method with metal loading of 20 wt% and 10: 10 wt%, respectively. The nanomaterials were characterized by Raman, X-ray diffraction, thermogravimetric analysis and transmission electronic microscope. The obtained materials were evaluated as electrocatalysts for Oxygen Reduction Reaction (ORR), obtaining the highest catalytic activity with Pt-Au/rGO compared to Pt/rGO; besides, the stability of the catalyst is determined until 50,000 cycles. Pt-Au/rGO was used to prepare membrane electrode assembly (MEA), in order to study the performance of this nanomaterial in the proton exchange membrane fuel cell (PEMFC). The maximum power density is 20 mW cm−2 and 70 mW cm−2 for Pt/rGO and Pt-Au/rGO, respectively, those values increased up to 365 mW cm−2, when Pt-Au nanoparticles supported on multiwall carbon nanotubes (CNT) was used as spacer.

High‐Quality Single‐Mode Lasers Based on Zero‐Dimensional Cesium Lead Halide Perovskites

Zero‐dimensional (0D) perovskites are emerging as a class of optoelectronic materials due to their unprecedented strong excitonic properties and high stability. Although the photoluminescence properties of 0D perovskites (Cs4PbX6) are investigated, the origin of green emission is still opaque, and their lasing performances are not reported. Herein, using the femtosecond transient absorption measurements to study the photophysical properties of Cs4PbBr6, the presence of polarons in Cs4PbBr6 is revealed, which provides the evidence that the green emission is contributed from the intrinsic behavior of Cs4PbBr6 rather than CsPbBr3 impurities. The successful lasing achieved from Cs4PbBr6 microdisks (MDs) by a room‐temperature reverse microemulsion method is demonstrated. The as‐prepared MDs with a smooth surface and a regular geometric structure can act as ideal whispering‐gallery‐mode microcavities. Optically pumped single‐mode lasing with a low threshold and high‐quality factor is successfully achieved from MDs under both one‐ and two‐photon excitation at room temperature. The MDs display an excellent stability while stored under ambient conditions for several months. In addition, the phase transformation between CsPbBr3 and Cs4PbBr6 can be easily achieved via tuning the amounts of surfactants. This work suggests that 0D perovskites can be promising materials toward the development of miniaturized lasers and other optoelectronic devices.

Controlled synthesis of ammonium manganese tri-fluoride nanoparticles with enhanced electrochemical performance

Herein, ammonium manganese tri-fluoride (NH4MnF3) nanoparticles (∼20–80 nm) were synthesized via easy, non-sophisticated and environment friendly reverse micro-emulsion method for the first time. Two type i.e. sintered and non-sintered NH4MnF3 nanoparticles were prepared with different ratio by changing water to surfactant percentage while keeping the temperature constant at 22 °C. The structural, morphological and optical properties of as-prepared nanoparticles were investigated by x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), UV–vis spectroscopy and Fourier-Transform infrared (FTIR) spectroscopy. The electrochemical performances were measured by using cyclic voltammetry and the result shows that after sintering the performance are significantly improved up to ∼0.079 mA g−1. We hope, our approach will opens up a new opportunity for such materials in energy storage devices.

Ultrathin, Core-Shell Structured SiO2 Coated Mn2+ -Doped Perovskite Quantum Dots for Bright White Light-Emitting Diodes.

All-inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion-exchange reactions, and unsatisfactory stability. Here, the ultrathin, core-shell structured SiO2 coated Mn2+ doped CsPbX3 (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX3 core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well-controlled within 2 nm, which gives the CsPbMnX3 @SiO2 QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr3 QDs with green emission and CsPbMnX3 @SiO2 QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light-emitting diode (LED) is successfully prepared by the combination of a blue on-chip LED device and the above perovskite mixture. The as-prepared white LED displays a high luminous efficiency of 68.4 lm W-1 and a high color-rendering index of Ra = 91, demonstrating their broad future applications in solid-state lighting fields.

Synthesis of LaMgAl11O19 powders by reversed microemulsion method

The phase behavior of the system employing TritionX-100 as surfactant was investigated with setting different rea-gents as cosurfactant and oil phase at various temperatures and mass ratios of TritionX-100 to cosurfactant. The pseudo-ternary phase diagrams were drawn by using conductivity method. The results indicate that the microemulsion is the most stable and has the best water solubility when the mass ratio of TritionX-100 to hexylalcohol is 1:1. Based on that, LMA powder was synthesized via reversed-microemulsion method using nitrate and ammonia as raw materials. The surface area of LMA powders increases to 53.41m2/g with the increasing water content of the system.

Efficient and Selective Ni/Al2O3–C Catalyst Derived from Metal–Organic Frameworks for the Hydrogenation of Furfural to Furfuryl Alcohol

Currently, precious metal catalysts or toxic copper-chromium catalysts are widely used in the catalytic hydrogenation of furfural. In this study, the selective hydrogenation of furfural to furfuryl alcohol was performed over alumina-carbon matrix embedded Ni nanoparticles catalyst. The Ni-loaded metal organic framework precursors were synthesized by reverse microemulsion method (water in oil), then the Ni/Al2O3–C catalysts were obtained by pyrolysis under a nitrogen atmosphere. Various characterizations including XRD, XPS, SEM, TEM, TPR, TPD and TG were carried out to reveal the microstructure and chemical composition of the prepared samples. The results showed that the hexagonal platelet structure and the smaller nickel nanoparticle size(~ 8 nm) benefits from the alumina–carbon matrix support, which helped the uniform dispersion and prevented it from accumulation at high temperatures. In addition, the catalyst performance was greatly affected by the calcination conditions and metal loading. At optimized operating conditions, 98.7% conversion of furfural and 92% yield of furfuryl alcohol could be achieved over Ni0.15/Al2O3–C catalyst in the liquid phase hydrogenation reaction with a good reusability.

Effect of Magnetic Anisotropy on Magnetic Thermal Induction of Mn0.3Zn0.3CoxFe2.4−xO4 Nanoparticles**Supported by the National Natural Science Foundation of China under Grant Nos 51571146, 51771124 and 51701130.

Mn0.3Zn0.3CoxFe2.4−xO4 series magnetic nanoparticles are prepared by the high-temperature organic solvent method, and Mn0.3Zn0.3CoxFe2.4−xO4@SiO2 composite nanoparticles are prepared by the reverse microemulsion method. The as-prepared samples are characterized, and the results show that the magnetic anisotropy constant of nanoparticles increases with the cobalt content, and the magnetic thermal induction shows a trend of increasing first and then decreasing. The optimal magnetic thermal induction is obtained at x = 0.12 with a specific loss power of 2086 w/gmetal, which is a bright prospect in clinical magnetic hyperthermia.

The impact of yttrium cations (Y3+) on structural, spectral and dielectric properties of spinel manganese ferrite nanoparticles

New yttrium substituted manganese ferrite (MnYxFe2-xO4) nanoparticles (NPs) were prepared by low cost reverse micelle micro-emulsion method by utilizing cheap raw materials like Paraffin, Triton X-100, and 1-butanol and corresponding metal salts. The Y3+content (x) range was kept 0 ≤ x ≤ 0.16. Thermogravimetric analysis (TGA) of un-annealed precipitates was carried out to probe the phase formation temperature. The annealing of precipitates of all compositions of MnYxFe2-xO4 nanoparticles was carried at 400 °C for 4 h (h). The annealing was carried out under vacuum to control the oxidation of manganese. The effect of Y3+ cations on structural, spectral and dielectric properties was investigated by X-ray diffraction (XRD), Fourier Transform Infra-Red (FTIR) spectroscopy and impedance analyzer measurements at room temperature. XRD patterns confirmed the formation of MnFe2O4 and its derivatives with yttrium. Site radii and bond lengths were calculated from XRD data. FTIR spectra confirmed the tetrahedral (A) and octahedral (B) sites in all compositions of MnYxFe2-xO4 nanoparticles, which is characteristic of spinel ferrites having FCC (face centered cubic) structure. Scanning electron microscopic (SEM) analysis confirmed the spherical morphology of ferrite particles. Dielectric parameters analysis in the frequency range from 1 × 106 Hz to 3 × 109 Hz suggested that these ferrite particles may find their potential applications in high frequency devices fabrication.

Synthesis and properties of BaWO4 nanocrystals prepared using a reverse microemulsion method

Barium tungstate (BaWO4) nanocrystals were successfully synthesized using a reverse microemulsion method. The effects of the molar ratio of water to surfactant (ωo), reactant concentration, and aging time on the size and morphology of the BaWO4 nanocrystals were investigated. The obtained products were characterized by scanning electron microscopy and X-ray diffraction (XRD). The experimental results showed that the morphology and size of the as-prepared BaWO4 nanocrystals were greatly affected by the ωo and the initial concentration, but no obvious effect by the aging time. XRD analysis showed that the BaWO4 nanocrystals synthesized had the high purity under conditions of initial reactant concentration of 0.2 mol/L, ωo of 40, at temperature of 50 °C and aging time of 24 h. Photoluminescent spectra revealed that BaWO4 crystallites displayed a very strong peak at 351 nm under different aging time.

New doubly doped cerium oxide Ce1-x-yYbyPdxO2-δ: The effect of ytterbium doping on stabilization of reduced palladium species on doped ceria oxide

Abstract The doubly and mono doped nanocrystalline mixed oxides Ce1-x-yYbyPdxO2-δ (y up to 0.4, x up to 0.2) were synthesized with the reversed microemulsion method. The morphology, microstructure and composition of the samples were investigated by TEM, EDS, XRD, XAFS, and DFT calculations of XANES spectra. The main aim of the study was the determination of the influence of an additional ytterbium content on structural and electronic properties of the Pd-doped ceria mixed oxide, i.e., the comparative discussion of the results obtained for Ce1-xPdxO2-δ and Ce1-x-yYbyPdxO2-δ. All samples were homogeneous fluorite-type nanocrystallites with very small size (3–5 nm). Reducibility studies revealed strong hydrogen consumption in these systems at low temperatures without any changes of their structure. The XANES and EXAFS spectra for Ce1-x-yYbyPdxO2-δ indicate a partial reduction of palladium at 200 °C and almost complete (90%) at 500 °C in hydrogen. The presence of ytterbium in Ce1-x-yYbyPdxO2-δ prevents the formation of metallic particles in reducing atmosphere (up to 500 °C) and strongly inhibits crystal growth of the mixed oxide.

A Novel Preparation of Blankophor R Nanoparticles by Reverse Microemulsion Method

Blankophor R is an organic compound and a stilbene type of fluorescent whitening agent (FWA). In this research, the preparation of Blankophor R was successfully synthesized using a nucleophilic substitution reaction withphenyl-isocyanate based on 4,4′-diamino-stilbene-2,2′-disulfonic acid. The structure of Blankophor R and its intermediates were characterized by spectroscopy techniques. In addition we reported a Blankophor R synthesis of Blankophor R nanoparticles in Reverse microemulsion method. The optimized formulation contains (w/w): water 20%, n-butyl acetate 50%, cetyltrimethylammonium bromide 10%, and isopropanol 20% and Blankophor R in water (%): 0.5. As a result, the microemulsion system was prepared clear, homogeneous and thermodynamically stable. The obtained Blankophor R nanoparticles showed spherical shape with an average diameter 60 nm, based on SEM and TEM images. In this work, the effect of Blankophor R NPs on dye transfer inhibition (DTI) were showed a high stability, leading to excellent DTI effects.

Silica Coated ZnFe2O4 Nanoparticles as Cathode Catalysts for Rechargeable Lithium‐Air Batteries

AbstractIn this work, the preparation and structural characterization of a novel material consisting of silica‐coated zinc ferrite (ZnFe2O4) nanoparticles as cathode catalysts for nonaqueous lithium‐air batteries (LABs) are presented for the first time. ZnFe2O4 nanoparticles (NPs) were prepared by the normal micelles method, using oleic acid as the capping agent and then coating them with silica, via a reverse microemulsion method, with various thicknesses. The colloidal ZnFe2O4 NPs and silica‐coated ZnFe2O4 NPs were characterized by TEM and powder XRD. The particle size of bare ZnFe2O4 NPs was calculated to be 5.8 nm by both TEM image and XRD pattern. They were then coated by silica with layer thicknesses of 9, 11, and 13 nm. The performances of bare and silica‐coated ZnFe2O4 NPs were evaluated as cathode catalysts for LABs using 1 M lithium trifluoromethanesulfonate (TFMS) in tetraethylene glycol dimethyl ether (TEGDME) as the electrolyte. The primary discharge/charge capacities of bare ZnFe2O4 NPs and ZnFe2O4 NPs with silica‐shell thicknesses of 9, 11, and 13 at 0.1 mA cm−2 were found to be 3300, 4300, 6200 and 5000 mAh g−1, respectively. The overpotential is almost 0.5 V, decreased by silica coating with a thickness of 11 nm, whereas there was no difference at other thicknesses. Cyclability with a discharge capacity of 1000 mAh g−1 was observed for at least 45 cycles for silica‐coated ZnFe2O4 NPs with a shell thickness of 11 nm.

Influence of organic solvents in the Pt nanoparticle synthesis on MWCNT for the methanol oxidation reaction

We studied the effect of the organic solvent on the synthesis of platinum nanoparticles anchored on the surface of multi-wall carbon nanotubes (Pt NPs/MWCNT) by the reverse microemulsion method. For oil phase, three organic solvents of the same alkane chain length (six carbon atoms) were tested: hexane, cyclohexane, and 2,2,4-trimethylpentane. The total metallic content was characterized by thermogravimetric analysis (TGA), and Pt NPs were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The chemical structure of the oil phase influences the Pt loading and crystallite size. The catalyst prepared with 2,2,4-trimethylpentane showed the highest electrochemical active surface area, enhancing the mass and specific activity compared to the commercial electrocatalyst (Pt/C) in the methanol oxidation reaction (MOR).

Fe3O4-TiO2 and Fe3O4-SiO2 Core-shell Powders Synthesized from Industrially Processed Magnetite (Fe3O4) Microparticles

The interest for core-shells has been increased in the recent years due to their improved and modifiable properties. In this work, Fe3O4-TiO2 and Fe3O4-SiO2 core-shells were successfully synthesized from an industrially produced magnetite-rich powder with micro- and nanometric particle sizes, superparamagnetic behavior and saturation magnetization of 49 emu/g. The reverse microemulsion method was used to the synthesis of these core-shells. X-ray diffraction, energy dispersive X-ray analysis, electron microscopy (SEM-TEM), and magnetization curves were used to characterize the solids. Core-shells with different morphology and size, coating of crystalline TiO2 (anatase) or amorphous silica, and superparamagnetic performance at room temperature (300 K) were obtained.

Polydopamine coated multifunctional lanthanide theranostic agent for vascular malformation and tumor vessel imaging beyond 1500 nm and imaging-guided photothermal therapy.

The optical imaging guided tumor vessels and vascular malformation visualization by using the second near infrared emission beyond 1500 nm (NIR-II) is emerged as the next generation fluorescence imaging technique for early tumor diagnosis and identification of tumor-associated vascular features. On the other hand, developing theranostic probes for NIR-II imaging guided photothermal therapy (PTT) is of great significance, which is rarely explored. Herein, a high performance theranostic nanoplatform based on the core-shell structured NaLuF4 nanorods@polydopamine (denoted as NRs@PDA) by integrating the new advanced NIR-II imaging beyond 1500 nm with PTT function was developed for tumor-associated vascular malformation visualization and imaging-guided PTT.Methods: In this work, the hydrophilic NaLuF4 NRs@PDA therapeutic probe was synthesized by using a reverse microemulsion method. The crystal phase, morphology, emission spectra and photothermal performance of the synthesized samples were systematically characterized. The NIR-II optical imaging and photothermal properties were investigated by in vitro and in vivo experiments.Results: The NaLuF4 NRs@PDA therapeutic probe possessed efficient NIR-II emission centered at 1525 nm with high quantum yield (QY), good photo-stability and high biocompatibility. In vivo NIR-IIb imaging based on the designed probe can clearly visualize the whole-body vessel and brain vessel with high spatial resolution, especially tumor-associated vessels. In addition, in vitro and in vivo experiments also demonstrated that the designed NaLuF4 NRs@PDA probe possessed efficient photothermal conversion efficiency (40.18%) for PTT ablation of tumor.Conclusion: With the excellent NIR-II imaging ability and PTT of tumor, the designed theranostic nanoplatform successfully realize the simultaneous tumor vessel diagnosis and tumor therapy, which may provide the opportunity of designing new theranostic bioprobes with combination of the NIR-II optical imaging technique and PTT function for tumor diagnosis and therapy.

Enhancement of cisplatin efficacy by lipid-CaO2 nanocarrier-mediated comprehensive modulation of the tumor microenvironment.

Hypoxia, acidosis and high level of glutathione (GSH) are characteristic abnormalities of the tumor microenvironment (TME), which promote tumor progression, metastasis, and resistance to therapies. Previous attempts to improve therapeutic efficacy were limited to modifying individual TME elements. In this study, we proposed a comprehensive TME modulation strategy that modifies multiple elements of the TME in order to enhance cisplatin anticancer efficacy. To do so, we prepared biocompatible lipid-coated CaO2/cisplatin nanoparticles (LipoCaO2/DDP) by the reverse microemulsion method. We imbued CaO2 with the following reverse-TME properties: O2 generation, increased pH value in tumor cells, and oxidation of intracellular glutathione. In vitro experiments showed that LipoCaO2/DDP could deplete GSH for preventing the binding of GSH to cisplatin. Simultaneously, CaO2 could significantly downregulate multidrug resistance-associated protein 2 (MRP2) by O2-dependent hypoxia-inducible factor 1 (HIF-1) inactivation. Hence, the complete drug-efflux pathway was blocked, and the anticancer effect of cisplatin was enhanced both in vitro and in vivo. Herein, we not only demonstrated the GSH depletion capacity of CaO2 for the first time, but also provided a new comprehensive therapeutic strategy to overcome therapeutic resistance caused by multiple factors in the TME.

Thermal stability and propane combustion activity of RhxCe1−xO2−y nanoparticles deposited on functionalized alumina

A new, effective method for stabilization of RhxCe1−xO2−y nanoparticles synthesized by the reverse microemulsion method by their deposition on functionalized alumina has been successfully applied for systems in a wide range of Rh contents (x ≤ 0.15).

Fabrication of highly fluorescent multiple Fe3O4 nanoparticles core-silica shell nanoparticles

The synthesis of hybrid nanoparticles with multiple functions from the economical and scalable perspective is an important issue in nanoparticle engineering. Herein, we report a representative example of multi-functional nanosystems simultaneously possessing fluorescence and magnetism as well as the excellent structural properties of nanosilica. Highly fluorescent multiple Fe3O4 nanoparticles core-silica shell nanoparticles (FL multi-Fe3O4@SiO2 NPs) are successfully synthesized and fully characterized. The multiple Fe3O4 nanoparticles can be uniformly and collectively encapsulated within a silica matrix using a reverse microemulsion (RM) method. Fluorescent dyes are successfully functionalized through the sequential hydrolysis and condensation of tetraethylorthosilicate (TEOS) and 3-(aminopropyl) triethoxysilane (APTES). Both organic (fluorescein) and inorganic (Rubpy) dyes can be used to generate the FL multi-Fe3O4@SiO2 NPs. These synthetic paradigms for multi-functional nanoparticles can significantly facilitate the fabrications of unique nanomaterials widely applied in a variety of areas.

Facile Synthesis of Silver Nanoparticles with High Antibacterial Activity.

We report on a reverse microemulsion method for the synthesis of silver nanocrystals and examine their antibacterial activities. As the molar ratio of water to sodium bis(2-ethylhexyl) sulfosuccinate (AOT) increases to 25, a morphology transition from a sphere-like nanocrystal to a wire-like one was observed. For both the gram-negative and gram-positive bacteria, the wire-like silver nanocrystal showed higher antibacterial activities. We conclude that the morphology of silver nanocrystals dominates their antibacterial activity.

An improved class of fluorescent silica nanoparticles for indirect immunofluorescence detection of MCF-7 cells

In this work, we have developed an efficient method based on silica fluorescent dye-doped nanoparticles and second antibody for cancer cell labeling. The dye-doped silica nanoparticles were synthesized by the reverse microemulsion method with the conjugate of 3-aminopropyltriethoxysilane and rhodamine B isothiocynate. A PEG with flexible long chain as the bridge was introduced onto the surface of the nanoparticle via cyanogens bromide method. The second antibody, goat anti-rabbit IgG, was conjugated on the surface of the PEG-terminal modified silica fluorescent nanoparticles by covalent binding to the PEG linkers via the EDC/sulfo-NHS method. The concentrations of goat anti-rabbit IgG covering the nanoparticles were quantified via the Bradford method. The silica fluorescent nanoparticles functionalized with rabbit anti-MUC1 antibody were employed as bioprobes for the recognition of MUC1 protein in human breast carcinoma molecules MCF-7 cells. Compared with fluorescent dye labeled IgG, the fluorescent nanoprobes display dramatically increased photostability.