Investigation of AOT-based microemulsions for the controlled synthesis of MoSx nanoparticles : an electron microscopy study

Exploring the Versatility of Microemulsions in Cutaneous Drug Delivery: Opportunities and Challenges

Microemulsions are novel drug delivery systems that have garnered significant attention in the pharmaceutical research field. These systems possess several desirable characteristics, such as transparency and thermodynamic stability, which make them suitable for delivering both hydrophilic and hydrophobic drugs. In this comprehensive review, we aim to explore different aspects related to the formulation, characterization, and applications of microemulsions, with a particular emphasis on their potential for cutaneous drug delivery. Microemulsions have shown great promise in overcoming bioavailability concerns and enabling sustained drug delivery. Thus, it is crucial to have a thorough understanding of their formulation and characterization in order to optimize their effectiveness and safety. This review will delve into the different types of microemulsions, their composition, and the factors that affect their stability. Furthermore, the potential of microemulsions as drug delivery systems for skin applications will be discussed. Overall, this review will provide valuable insights into the advantages of microemulsions as drug delivery systems and their potential for improving cutaneous drug delivery.

Direct Observation of Emulsion Morphology, Dynamics, and Demulsification

Herein, we present the direct observation and quantification of a water-in-oil (w/o) emulsion, its destabilization, and the effect of additives on such processes at the nanoscale. This is achieved via liquid phase transmission electron microscopy (LPTEM), wherein a small volume of emulsion is encapsulated against vacuum in its liquid state to allow observation of its initial morphology and its evolution over time at excellent spatial and temporal resolution. Emulsions of this class are useful for delivering payloads of materials insoluble in their delivery medium and are currently widely used across food science, pharmaceuticals, and environmental applications. However, their utility is inherently limited by their thermodynamic tendency to demulsify, eventually leading to bulk phase separation. This occurs via several degradation mechanisms, operating at times collectively, and which are difficult to differentiate via traditional ensemble methods (e.g., light scattering), obscuring mechanistic nuances. LPTEM as a characterization technique has the potential to augment our understanding of emulsion behavior and improve performance and formulations. In this work, we also emphasize the importance of the included videographic Supporting Information data in demonstrating the behavior of the studied materials.

A Review of The Lesser-Studied Microemulsion-Based Synthesis Methodologies Used for Preparing Nanoparticle Systems of The Noble Metals, Os, Re, Ir and Rh

This review focuses on the recent advances in the lesser-studied microemulsion synthesis methodologies of the following noble metal colloid systems (i.e., Os, Re, Ir, and Rh) using either a normal or reverse micelle templating system. The aim is to demonstrate the utility and potential of using this microemulsion-based approach to synthesize these noble metal nanoparticle systems. Firstly, some fundamentals and important factors of the microemulsion synthesis methodology are introduced. Afterward, a review of the investigations on the microemulsion syntheses of Os, Re, Ir, and Rh nanoparticle (NP) systems (in all forms, viz., metallic, oxide, mixed-metal, and discrete molecular complexes) is presented for work published in the last ten years. The chosen noble metals are traditionally very reactive in nanosized dimensions and have a strong tendency to aggregate when prepared via other methods. Also, the particle size and particle size distribution of these colloids can have a significant impact on their catalytic performance. It is shown that the microemulsion approach has the capability to better stabilize these metal colloids and can control the size of the synthesized NPs. This generally leads to smaller particles and higher catalytic activity when they are tested in applications.

Effect of Particle Size on the HDS Activity of Molybdenum Sulfide

More than half of the total world oil reserves are heavy oil, extra heavy oil, and bitumen; however their catalytic conversion to more valuable products is challenging. The use of submicronic particles or nanoparticles of catalysts suspended in the feedstock may be a viable alternative to the conversion of heavy oils at refinery level or downhole (in situ upgrading). In the present work, molybdenum sulfide (MoS2) particles with varying diameters (10000–10 nm) were prepared using polyvinylpyrrolidone as capping agent. The prepared particles were characterized by DLS, TEM, XRD, and XPS and tested in the hydrodesulfurization (HDS) of a vacuum gas oil (VGO). A correlation between particle size and activity is presented. It was found that particles with diameters around 13 nm show double the HDS activity compared with the material with micrometric particle sizes (diameter ≈ 10,000 nm).

Microemulsion-based synthesis and electrochemical evaluation of different nanostructures of LiCoO2 prepared through sacrificial nanowire templates

For the first time, we demonstrate the use of a microemulsion reaction to synthesize different nanostructures of LiCoO2 cathode material. By varying the annealing temperature and time, porous nanowires and nanoparticles of LiCoO2 are obtained. The electrochemical performances of these different nanostructures obtained under the respective annealing conditions are evaluated. It is shown that nanoparticles formed under the annealing condition of 700 °C, 1.5 h perform the best, delivering an initial capacity of around 135 mA h g(-1), which is close to the theoretical capacity of LiCoO2, 140 mA h g(-1). They also exhibit a capacity retention of around 93% by 100 cycles at 0.1 C. Comparisons are made between our LiCoO2 material obtained under different annealing conditions and those in the literature.

Effect of Conductivity of the Aqueous Solution on the Size of Printable Nanoparticle

Direct writing technology using nano/microsize particles in aqueous solution is currently one of the leading candidates to bring a substantial advancement to the technical arena. However, little is known about an effect of conductivity of the solution including metal ions on nanoparticle size for the direct writing technology. It is believed that conductivity of solution can influence the size of particles in reducing environmental of aqueous solutions. In this study parameters which affect electric conductivity in solution were characterized by changing concentration of copper ion, concentration of surfactants, and anion of metal compounds. The mobility of ion in aqueous media with respect to copper ion concentration was the most pronounced factor to control the size of created copper nanometals in water. However, due to the high reactivity on large surface area, the nanocopper metal was oxidized in water. The electric conductivity varied in the range of 7 to 360 mS/cm when Cu(NO3)2⋅3H2O dissolved in water from 0.03–3.0 mol/dm3. In this condition, the size of nano particles can vary from 10 to 500 nm. Various concentrations of surfactants and two anion Cu compounds used to vary the conductivity of the solution to verify the effect of electric conductivity of solution on the particle size. Decreasing the conductivity had a corresponding effect on the particle size. The electric conductivity was decreased from 67 to 56 mS/cm by adding surfactant from 0.1 to 0.5 mol/dm3consequently, the particle sizes were decreased from 89 to 21 nm. Copper nitrate and copper chloride were used to verify the anion effect on electrical conductivity and particle sizes. This effect was not dependent on the kind of ions chosen to change the conductivity. However, when Cu(NO3)2⋅3H2O was used, the size of the particles was 89 nm, while it was 91 nm when CuCl2⋅2H2O was used.

Synthetic Fabrication of Nanoscale MoS2-Based Transition Metal Sulfides

Transition metal sulfides are scientifically and technologically important materials. This review summarizes recent progress on the synthetic fabrication of transition metal sulfides nanocrystals with controlled shape, size, and surface functionality. Special attention is paid to the case of MoS₂ nanoparticles, where organic (surfactant, polymer), inorganic (support, promoter, doping) compounds and intercalation chemistry are applied.

Formation of organic nanoparticles from volatile microemulsions

A method for preparation of nanoparticles of poorly water-soluble organic materials is presented. By this method, an oil-in-water microemulsion containing a volatile solvent with dissolved model material, propylparaben, undergoes solvent evaporation and conversion into nanoparticles by spray drying. The resulting powder can be easily dispersed in water to give a clear, stable dispersion of nanoparticles with a high loading of propylparaben. By filtration of this dispersion it was found that more than 95wt.% of the dispersed propylparaben is in particles of less than 450nm. X-ray diffraction revealed that propylparaben is present as nanocrystals of 40-70nm. After dispersion of the powder in water, formation of large crystals rapidly occurs. Addition of polyvinylpyrrolidone (PVP) prevented crystal growth during dispersion of the powder in water. The inhibition of propylparaben crystal growth by PVP was studied by molecular dynamic simulations that addressed the binding of PVP to the propylparaben crystal. A comparison was made between PVP and polyvinylalcohol, which did not display crystal inhibition properties.

Generation of metal oxide nanoparticles in optimised microemulsions

The phase behavior and structure of aqueous-in-n-heptane microemulsions, stabilized by surfactant mixtures of di-n-didodecyldimethylammonium bromide, DDAB, and Brij(R)35 were studied by small angle (neutron or X-ray) scattering techniques. The aqueous nanodroplets contain either a precursor reactive salt or a precipitating agent, so that simple mixing induces nanoparticle formation. These formulated microemulsions display good phase stability against added polar additives such as monovalent, divalent, trivalent metal ions, ammonia solution, tetrabutylammonium hydroxide, and their mixtures. Nanoparticle formation was demonstrated via precipitation of metal oxides inside the water nanodroplets, affording control over the resulting particle size. Nanoparticle characteristic size (XRD- and HR-TEM derived sizes) and specific surface areas (S(BET) (m(2)g(-1))) for iron oxide and CeO(2) prepared in these mixed microemulsions, are compared with those stabilized by single surfactants DDAB and Pure AOT.

Optimization of dye-doped silica nanoparticles prepared using a reverse microemulsion method

Fluorescent labeling based on silica nanoparticles facilitates unique applications in bioanalysis and bioseparation. Dye-doped silica nanoparticles have significant advantages over single-dye labeling in signal amplification, photostability and surface modification for various biological applications. We have studied the formation of tris(2,2'-bipyridyl)dichlororuthenium(II) (Ru(bpy)) dye-doped silica nanoparticles by ammonia-catalyzed hydrolysis of tetraethyl orthosilicate (TEOS) in water-in-oil microemulsion. The fluorescence spectra, particle size, and size distribution of Ru(bpy) dye-doped silica nanoparticles were examined as a function of reactant concentrations (TEOS and ammonium hydroxide), nature of surfactant molecules, and molar ratios of water to surfactant (R) and cosurfactant to surfactant (p). The particle size and fluorescence spectra were dependent upon the type of microemulsion system chosen. The particle size was found to decrease with an increase in concentration of ammonium hydroxide and increase in water to surfactant molar ratio (R) and cosurfactant to surfactant molar ratio (p). This optimization study of the preparation of dye-doped silica nanoparticles provides a fundamental knowledge of the synthesis and optical properties of Ru(bpy) dye-doped silica nanoparticles. With this information, these nanoparticles can be easily manipulated, with regard to particle size and size distribution, and bioconjugated as needed for bioanalysis and bioseparation applications.