Reverse Micelles Research Articles

Investigated the effects of surfactant concentration on cobalt ferrite nanoparticles synthesized in reverse micelles

The use of reverse micelles as nanoscale hydrophilic voids of microemulsions in the manufacture of ferrites has been recognized since the 1960s, but there has been very little attention on the structural and magnetic properties with respect to surfactant concentration. This paper investigates the influence of surfactant sodium dodecyl sulphate (SDS) concentrations on cobalt ferrite (CoFe2O4) nanoparticles prepared by reverse micelles at annealing temperatures 250°C and 500°C. Samples with varied cobalt to SDS ratios (Co: SDS = 1: 0.33, 1: 0.5, 1: 0.66) were subjected to XRD, TGA, TEM, FTIR and VSM Studies. All the samples exhibited single-phase spinel structures with crystalline diameters ranging from 10 to 18 nm. As the SDS concentration increased the crystallite size decreased. The TEM images showed the particle size in the range of 7.6 -17.7 nm. VSM investigations show the ferromagnetic behavior of the sample. The observed increase in coercivity with respect to annealing temperature for the same concentration reflects the single-domain nature of the nano particles. This underscores the crucial role of annealing conditions in customizing cobalt ferrite nanoparticles as a suitable application in longitudinal magnetic recording media.

Alginate nanoparticle synthesis using n-heptane and isopropyl myristate/AOT reverse micelles: the impact of the non-polar solvent, water content, and pH on the particle size and cross-linking efficiency

The synthesis of monodisperse and stable alginate nanoparticles (ALG-NPs) was achieved through the crosslinking of sodium alginate with Ca2+ ions within sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles (RMs) as nano-templates.

Vortex flow induced self-assembly in CsPbI3 rods leads to an improved electrical response towards external analytes.

We present a facile and versatile strategy for enabling CsPbI3 rods to self-assemble at an air-water interface. The CsPbI3 rods, which float at the air-water interface, align under the influence of the rotational flow field due to the vortex motion of a water subphase. The aligned CsPbI3 rods could be transferred onto various substrates without involving any sophisticated instrumentation. The temperature of the subphase, the concentration of the CsPbI3 aliquot, the rotational speed inducing vortex motion, and the lift-off position and angle of the substrate were optimized to achieve high coverage of the self-assembled rods of CsPbI3 on glass. The Rietveld refinement of the XRD profile confirms that the aligned CsPbI3 is in the pure orthorhombic phase ascribed to the Pnma space group. The hydrophilic carboxylic group of the oleic acid attaches to the Pb atoms of the halide perovskite rods, while their hydrophobic tails encapsulate the rods within their shell, creating a shielding barrier between the water and the perovskite surface like a reverse micelle. The aligned CsPbI3 rods exhibit a nearly 47-fold increment in current upon exposure to ammonia gas (amounting to 5.6 times higher sensitivity in ammonia sensing) compared to the non-aligned CsPbI3 rods.

Experimental and simulation study of self-assembly and adsorption of glycerol monooleate in n-dodecane with varying water content onto iron oxide.

The self-assembly and surface adsorption of glycerol monooleate (GMO) in n-dodecane are studied using a combination of experimental and molecular dynamics simulation techniques. The self-assembly of GMO to form reverse micelles, with and without added water, is studied using small-angle neutron scattering and simulations. A large-scale simulation is also used to investigate the self-assembly kinetics. GMO adsorption onto iron oxide is studied using depletion isotherms, neutron reflectometry, and simulations. The adsorbed amounts of GMO, and any added water, are determined experimentally, and the structures of the adsorbed films are investigated using reflectometry. Detailed fitting and analysis of the reflectometry measurements are presented, taking into account various factors such as surface roughness, and the presence of impurities. The reflectometry measurements are complemented by molecular dynamics simulations, and good consistency between both approaches is demonstrated by direct comparison of measured and simulated reflectivity and scattering length density profiles. The results of this analysis are that in dry systems, GMO adsorbs as self-assembled reverse micelles with some molecules adsorbing directly to the surface through the polar head groups, while in wet systems, the GMO is adsorbed onto a thin layer of water. Only at high surface coverage is some water trapped inside a reverse-micelle structure; at lower surface coverages, the GMO molecules associate primarily with the water layer, rather than self-assemble.

Insights into water extraction and aggregation mechanisms of malonamide-alkane mixtures.

Structure at the nanoscale in the organic phase of liquid-liquid extraction systems is often tied to separation performance. However, the weak interactions that drive extractant assembly lead to poorly defined structures that are challenging to identify. Here, we investigate the mechanism of water extraction for a malonamide extractant commonly applied to f-element separations. We measure extractant concentration fluctuations in the organic phase with small angle X-ray scattering (SAXS) before and after contact with water at fine increments of extractant concentration, finding no qualitative changes upon water uptake that might suggest significant nanoscopic reorganization of the solution. The critical composition for maximum fluctuation intensity is consistent with small water-extractant adducts. The extractant concentration dependence of water extraction is consistent with a power law close to unity in the low concentration regime, suggesting the formation of 1 : 1 water-extractant adducts as the primary extraction mechanism at low concentration. At higher extractant concentrations, the power law slope increases slightly, which we find is consistent with activity effects modeled using Flory-Huggins theory without introduction of additional extractant-water species. Molecular dynamics simulations are consistent with these findings. The decrease in interfacial tension with increasing extractant concentration shows a narrow plateau region, but it is not correlated with any change in fluctuation or water extraction trends, further suggesting no supramolecular organization such as reverse micellization. This study suggests that water extraction in this system is particularly simple: it relies on a single mechanism at all extractant concentrations, and only slightly enhances the concentration fluctuations characteristic of the dry binary extractant/diluent mixture.

A deeper insight into the evaluation of water-in-oil amicroemulsion templated samarium sulfide nanospheres: exploring its role in pickering emulsion formulation for photocatalytic dye degradation and synthesis of PANI@Sm2S3 nanocomposites.

This study examines the effectiveness of W/O microemulsion-mediated Sm2S3 nanospheres in pickering emulsion-based crystal violet (CV) dye degradation and PANI@Sm2S3 nanocomposite synthesis. The evaluation of nanospheres inside the core of reverse micelles was performed through DLS, TEM and FESEM analyses. The formation of nanospheres involve two phases: a nucleation phase (5-30 min) and growth phase (30-120 min). Through in situ hydrophobization of negatively charged (with a zeta value of -4.47 mV at neutral pH) Sm2S3 nanoparticles (0.1 wt%) with a suitable amount of a cationic CTAB surfactant, a stable O/W pickering emulsion was developed. 0.1 wt% Sm2S3in situ hydrophobized with 2.7 mM CTAB offered a stable pickering emulsion with a diameter of 23 μm after 1 day of storage. This pickering emulsion improves the local concentration of CV by efficiently encapsulating dye molecules inside the core of emulsion droplets. Therefore, dye molecules get numerous opportunities to interact with the Sm2S3 photocatalyst and efficiently degrade. The pickering emulsion stabilised by 0.1 wt% of Sm2S3 nanoparticles in situ hydrophobized with 2.7 mM of CTAB results in almost 100% degradation. Moreover, using only solid Sm2S3 (having wt% of 0.025 or 0.075) as a pickering stabiliser, new PANI@Sm2S3 spherical nanocomposites were synthesised via pickering emulsion polymerization. The formation of PANI@Sm2S3 composites was identified via UV-vis, IR, and 1H-NMR investigations. The analysis of FESEM images showed that the amount of nanoparticles used in the dispersion (for 0.025 wt%, 35 nm and 0.075 wt%, 29 nm) strongly influences the size and shape of the composites.

Steric effects stabilize reverse micelle domains in supercritical CO2 by determined conformation: restrictions of water and cations

Previous research into designing CO2-philic surfactants has certain limitations, necessitating the exploration of effective design concepts for hydrocarbon surfactants, which are far less expensive and less toxic than fluorocarbon surfactants.

Electrodeposition of Au and AgAu Nanoparticles from Reverse Micelles – Tuning Particle Properties and Understanding Solvent and Confinement Effects by Ensemble and Single Entity Approaches

The synthesis and reactivity of nanoparticles (NPs) has vastly been studied for years,[1-3] yet still there are several open questions about how a synthesis method and its parameters influence the final properties of the obtained NPs. In the classical wet-chemical synthesis, capping agents are widely used to adjust the morphology and size, preventing further growth of NPs. However, their presence can be disadvantageous for some applications, e.g. electrocatalysis, where they decrease reaction kinetics. To overcome this issue, we use electrodeposition as synthetic route, and the size of the obtained NP is tuned by the amount of precursor that is loaded inside a reverse micelle. The NP formation is induced by applying a suitable potential to reduce the entrapped precursor at the electrode. This deposition can be done by ensemble or single entity approaches.Experimentally speaking, both approaches consist of an electrode immersed in a media with suspended precursor-loaded reverse micelles. However, for ensemble electrodeposition a macroelectrode is used, a standard chronoamperometry is recorded and average information about the system is provided. On the other hand, single entity approach relies on random collision of reverse micelles at a micro- or nanoelectrode, which appears as spikes on the chronoamperometric response, and data can be determined based on statistical analysis of single particle events.[4,5] It has been used to characterize different types of NPs, their size, composition and kinetic reaction parameters.[6,7] Focusing on the electrosynthesis, this work investigates the formation of Au and AgAu NPs by both ensemble and single entity approaches. Besides the synthesis method, the effect of the solvent and the 0D confinement is also under evaluation to better understand how one can tune NPs’ shape and structure, i.e. core-shell vs alloy arrangements. The solvent effect is investigated by using room temperature ionic liquid or organic solvents during electrodeposition. The reverse micelles act as a nanoreactor cage, confining the precursors, and therefore changing the type of this cage helps us to understand the influence of the 0D confinement. For this, reverse micelles of two different materials were used: SDS (sodium dodecyl sulphate) and PS-P2VP (polystyrene-b-poly(2-vinylpyridine)), with the former forming nanodroplets of an aqueous phase protected by a thin wall, and the latter assembling to a sphere with a polymeric core, completely binding the precursor.The resulting NPs were imaged by AFM, SEM and TEM and their composition resolved by EDX. Initial catalytic CV and LSV measurements towards hydrogen evolution reaction were done to provide further insights about the NPs’ properties. From these characterizations of the NPs, it has been demonstrated that the synthesis approach, the applied potential, the solvent, and the type of RM influence the final NPs’ properties. Hence, the size, composition, structure and catalytic activity of the resulting NPs can by tuned by electrochemical parameters, avoiding the necessity to select different capping and reducing agents as done in wet-chemical synthesis.[1] D. V. Talapin, E. V. Shevchenko. Chem. Rev. 2016, 116, 18, 10343–10345. doi: 10.1021/acs.chemrev.6b00566.[2] H. Duan, D. Wang, Y. Li. Chem. Soc. Rev., 2015, 44, 5778-5792. doi: 10.1039/C4CS00363B.[3] M. Grzelczak, J. Pérez-Juste, P. Mulvaney, L. M. Liz-Marzán. Chem. Soc. Rev., 2008, 37, 1783-1791. doi: 10.1039/B711490G[4] K. J. Stevenson, K. Tschulik. Curr. Opin. Electrochem. 2017, 6, 38–45. doi:10.1016/j.coelec.2017.07.009.[5] M. V. Evers, M. Bernal, B. Roldán Cuenya, K. Tschulik. Angew. Chem. 2019, 58, 8221-8225. doi: 10.1002/anie.201813993[6] E. N. Saw, M. Kratz, K. Tschulik. Nano Res. 2017, 10, 3680–3689. doi:10.1007/s12274-017-1578-3.[7] K. Shimizu, K. Tschulik, R. G. Compton. Chem. Sci. 2016, 7, 1408–1414. doi:10.1039/C5SC03678J.

(Invited) Zn Batteries: Stable Anode and High Energy Cathodes

Our research focuses on a stable aqueous Zn-based battery with long cycling stability, decent energy density, and ultimate safety performance for large-scale energy storage. To achieve this purpose, we did systematic studies on the Zn metal anode, electrolytes, and new cathode development.For the anode side, we developed a few strategies, including pH value manipulation, ion redistribution coating, gradient coating, etc to induce stable stripping and plating of Zn. Moreover, we also found that a Zn initially plated can be much more stable than the one initially stripped during the subsequent deposition. We further utilize this observation to develop a pre-deposited Zn for Zn batteries with improved stability.For the electrolyte, we develop a reverse micelle electrolyte, with it, the Zn anode exhibits balanced merits including strong H2 coevolution suppression, prevention of dendritic and dead Zn, inhibition of corrosion, as well as relatively fast reaction kinetics. In a more extensive context, the new reverse micelle structure of electrolytes is expected to benefit other emerging battery chemistries, where a balance between fast ion transport and sufficient stabilization against side reactions is required.For the cathode with high energy density, we studied the critical research concerns and further potential developments of chalcogen/halogen-based batteries, primarily focusing on the electrochemically active chalcogen/halogen sources, reaction modes, soluble products, and electrolyte adaptability.For the cathode, we use iodine as the fixing agents working in highly concentrated electrolytes to successfully enable reversible Cl-based redox electrode. The interhalogen coordinating chemistry fixes Cl in a configuration of ICl3 -. Furthermore, we simultaneously exploit two redox centers of Cl and I to realize a novel three-electrons transfer electrode, in which the Cl-I electrode can deliver remarkably high capacity up to 612.5 mAh gI -1 and energy density as 905 Wh kgI -1. The as-obtained energy density is 387% higher compared to the traditional one-electrons transfer of ZnǁI2 battery system and superior cycling stability with capacity retention as 95.7% after 2,000 cycles.

Impact of lipid matrix composition on the activity of membranotropic enzymes galactonolactone oxidase from Trypanosoma cruzi and L-galactono-1,4-lactone dehydrogenase from <i>Arabidopsis thaliana</i> in the system of reverse micelles

The study of many membrane enzymes in an aqueous medium is difficult due to the loss of their catalytic activity, which makes it necessary to use membrane-like systems, such as reverse micelles of surfactants in nonpolar organic solvents. However, it should be taken into account that micelles are a simplified model of natural membranes, since membranes contain many different components, a significant part of which are phospholipids. In this work, we studied the impact of the main phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), on the activity of membrane enzymes using galactonolactone oxidase from Trypanosoma cruzi (TcGAL) and L-galactono-1,4-lactone dehydrogenase from Arabidopsis thaliana (AtGALDH) as an examples. Effect of the structure (and charge) of the micelle-forming surfactant itself on the activity of both enzymes has been studied using an anionic surfactant (AOT), a neutral surfactant (Bridge-96), and a mixture of cationic and anionic surfactants (CTAB and AOT) as an examples. The pronounced effect of addition of PC and PE lipids on the activity of AtGALDH and TcGAL has been detected, which manifests as increase in catalytic activity and significant change in the activity profile. This can be explained by formation of the tetrameric form of enzymes and/or protein-lipid complexes. By varying composition and structure of the micelle-forming surfactants (AOT, CTAB, and Brijdge-96 and their combinations) it has been possible to change catalytic properties of the enzyme due to effect of the surfactant on the micelle size, lipid mobility, charge, and rigidity of the matrix itself.

Reverse micelle strategy for effective substitutional Fe-doping in small-sized CeO2 nanocrystals: Assessment of adsorption and photodegradation efficiency of ibuprofen under visible light

Reverse micelle nanoreactors were successfully designed to synthesize small-sized ceria nanocrystals (3.5–4.2 nm) with a sizeable amount of substitutional iron. Undoped and doped CeO2 catalysts with an iron content (0.50–10 mol %) compliant with the nominal value were prepared and tested for the first time for the removal of ibuprofen both in the dark and under UV or visible light irradiation.The effective inclusion and distribution of iron in the ceria lattice were ascertained through in-depth physicochemical characterization. In particular, X-ray diffraction suggested the formation of an F-type crystal structure, ruling out the formation of separate iron-containing crystalline phases. On the other hand, substitutional doping of CeO2 with Fe atoms favoured the formation of Ce3+ defects and vacancy sites (VOs) with a maximum for the sample with 2.5 mol % iron (Fe2.5), as evidenced by X-ray photoelectron spectroscopy (XPS) measurements and Raman spectroscopy. UV–Vis spectroscopy showed that the optical properties were successfully modified by the presence of iron, which causes a gradual decrease in band gap as iron content increases. The experimental evidence was further verified and supported by density functional theory calculations. DFT calculations also revealed that the surface iron and oxygen vacancies are the preferential sites for ibuprofen adsorption. Nevertheless, it was found under dark conditions that adsorption capacity does not monotonically increase with iron content, revealing contrasting roles of surface characteristics. Indeed, catalytic experiments have identified a trade-off between adsorption and photodegradation, identifying Fe2.5 as the best-performing catalyst for ibuprofen removal under visible light irradiation. These results were discussed by considering the key properties of the catalysts as well as their different surface charge determined by ζ potential measurements. The best catalyst was tested through reuse experiments that proved its stability over 4 cycles. Finally, an attempt was made to identify the photodegradation by-products, allowing the detection of 1-ethenyl-4-(2-methylpropyl)benzene as the main by-product.

Impact of Lipid Matrix Composition on Activity of Membranotropic Enzymes Galactonolactone Oxidase from Trypanosoma cruzi and L-Galactono-1,4-Lactone Dehydrogenase from Arabidopsis thaliana in the System of Reverse Micelles.

The study of many membrane enzymes in an aqueous medium is difficult due to the loss of their catalytic activity, which makes it necessary to use membrane-like systems, such as reverse micelles of surfactants in nonpolar organic solvents. However, it should be taken into account that the micelles are a simplified model of natural membranes, since membranes contain many different components, a significant part of which are phospholipids. In this work, we studied impact of the main phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), on activity of the membrane enzymes using galactonolactone oxidase from Trypanosoma cruzi (TcGAL) and L-galactono-1,4-lactone dehydrogenase from Arabidopsis thaliana (AtGALDH) as examples. Effect of the structure (and charge) of the micelle-forming surfactant itself on the activity of both enzymes has been studied using an anionic surfactant (AOT), a neutral surfactant (Brij-96), and a mixture of cationic and anionic surfactants (CTAB and AOT) as examples. The pronounced effect of addition of PC and PE lipids on the activity of AtGALDH and TcGAL has been detected, which manifests as increase in catalytic activity and significant change in the activity profile. This can be explained by formation of the tetrameric form of enzymes and/or protein-lipid complexes. By varying composition and structure of the micelle-forming surfactants (AOT, CTAB, and Brij-96) it has been possible to change catalytic properties of the enzyme due to effect of the surfactant on the micelle size, lipid mobility, charge, and rigidity of the matrix itself.

Models for Stabilization of Charged Particles with Surfactants in Nonpolar Media

Stabilization of charged particles in nonpolar media is one of the most complicated problems in modern colloid chemistry. The attribution to colloid chemistry is absolutely justified in this case: in nonpolar media, charged particles have, as a rule, a supramolecular nature. Low dielectric permittivity of a medium makes the existence of ions in the classical interpretation energetically disadvantageous. The key condition for the presence of charged particles in nonpolar media is their steric stabilization, which requires some revision of the classical concepts of the structure of the electrical double layer, primarily, its diffuse part. Detailed analyzing the structure of the electrical double layer in nonpolar media is of importance because of the high practical significance of electrokinetic phenomena in such systems. This review considers the main models for steric stabilization of charged particles with surfactants in dispersion media having dielectric permittivities lower than 5. The main attention is focused on not only the concentrations corresponding to the formation of reverse micelles, but also on the concentrations below the critical micelle concentration. In addition, nontypical examples of electrokinetic phenomena in organosols are considered.

Molecular-Level investigation of AOT reverse micelle water content for preserving chymotrypsin's native structure using MD simulation

The molecular dynamics simulation approach has been effectively employed to determine suitable activity conditions of chymotrypsin (α-CT) within a range of nano-pools. Results from eleven molecular dynamics simulations were presented, which were performed in ten water-AOT-isooctane reverse micelles and a bulk aqueous solution. Half of the RMs are empty, and the other half are loaded with α-CT in their water pools. Each batch of five RMs is studied in five different compositions of 3, 5, 10, 15 and 20 water-to-surfactant concentration ratios (W0) at ambient temperature and pressure. The simulation is not started from generally predefined geometric structures. Our simulations all started from random molecular configurations and then allowed sufficient simulation time for the system to reach equilibrium. The general shapes of RMs without protein cores are elongated ellipsoids at low W0 values and quasi-spherical at higher W0 values, while the overall shapes of RMs with protein cores are quasi-spherical and almost independent of W0 values. Previously published experimental data strongly support the results of our predicted simulated structures and analyzed dynamics. In both the simulated RM and the experimentally well-studied α-CT protein within RM at W0 15, the dynamics and structure closely mirror those of the actual bulk water environment. The shift in behavior was identified that led to the alteration of the protein structure's activity during the increase in water content of reverse micelles between W0 15 and 20. Overall, the rise in surface area interaction between the protein and nonpolar iso-Octane can be attributed to the reduction in surfactant coverage, causing the transition from W0 15 to 20.

Effect of swelling on dyeing of cotton fabric in supercritical CO2 with ionic liquid domain reverse micelles

Effect of swelling on dyeing of cotton fabric in supercritical CO2 with ionic liquid domain reverse micelles

Unusual Phase Behaviour for Organo-Halide Perovskite Nanoparticles Synthesized via Reverse Micelle Templating

Micelle templating has emerged as a powerful method to produce monodisperse nanoparticles. Herein, we explore unconventional phase transformations in the synthesis of organo-halide perovskite nanoparticles utilizing reverse micelle templates. We employ diblock-copolymer reverse micelles to fabricate these nanoparticles, which confines ions within micellar nanoreactors, retarding reaction kinetics and facilitating perovskite cage manipulation. The confined micellar environment exerts pressure on both precursors and perovskite crystals formed inside, enabling stable phases not typically observed at room temperature in conventional synthesis. This provides access to perovskite structures that are otherwise challenging to produce. The hydrophobic shell of the micelle also enhances perovskite stability, particularly when combined with anionic exchange approaches or large aromatic cations. This synergy results in long-lasting stable optical properties despite environmental exposure. Reverse micelle templates offer a versatile platform for modulating perovskite structure and behavior across a broad spectrum of perovskite compositions, yielding unique phases with diverse emission characteristics. By manipulating the composition and properties of the reverse micelle template, it is possible to tune the characteristics of the resulting nanoparticles, opening up exciting opportunities for customizing optical properties to suit various applications.

Effect of AOT/Heptane Reverse Micelles on Oxidation of Ferroin by Metaperiodate: Kinetic and Mechanistic Aspects

A kinetic study of the oxidation of Ferroin, [Fe(phen)3]2+ by metaperiodate (IO4-) has been carried out in AOT/heptane reverse micelles by changing W = ([H2O]/[AOT]) and AOT concentration. The reaction order is first order with respect to Ferroin, while zero order with respect to IO4-. The reaction rate is faster in aqueous medium compared to AOT reverse micelles by eight times. The oxidation rate increases with an increase in the value of W (at fixed surfactant concentration, [AOT]) and decreases with AOT concentration. The effect of W on rate is elucidated based on the low dielectric constant of the water pool. Berezin's pseudo-phase model has been applied to explain the effect of AOT on rate.

New Insights into the Loss of Antioxidant Effectiveness of Phenolic Compounds in Vegetable Oils in the Presence of Phosphatidylcholine.

It has been proposed that lipid oxidation reactions in edible oils primarily occur in reverse micelles (RM) of amphiphilic components. While the prooxidative effect of RM has been demonstrated, the mechanism involved is not fully understood. Both reductions and enhancements in the antioxidant efficacy (AE) of α-tocopherol and Trolox have been observed in different studies when phosphatidylcholine (PC) was added and PC RM were formed. However, most of these investigations employed lipid systems consisting of stripped vegetable oil diluted in saturated medium-chain triacylglycerols (MCT) and utilized antioxidant concentrations well below those found in edible oils. These two specific factors were investigated in the present study. The effect of RM of purified egg yolk PC on the AE of 1.16 mmol kg-1 α-tocopherol or Trolox in stripped sunflower oil (SSO) was studied by the Rancimat (100 °C) and oven (50 °C) tests. Increasing PC concentrations (50-1000 ppm) had no significant impact on α-tocopherol, but substantial reductions in AE were observed for Trolox. This phenomenon may be attributed to the partitioning of Trolox into the pre-existing PC micelles, suggesting that primary oxidation reactions occurred in the continuous lipid phase. In addition, the effectiveness of both antioxidants decreased significantly in the presence of PC when a low antioxidant concentration (0.06 mmol kg-1) was assayed in SSO:MCT (1:3, w/w).

Probing the effect of lightly doped Iron in Bi2S3 nanostructures on Physiochemical properties and efficacy in anti-microbial activity

In this study, Bi2S3 nanostructures doped with Iron (Fe) at various concentrations i.e., FexBi2-xS3 (x = 0.0, 0.4, 0.6, 0.8 wt%) were synthesized using the reverse micelle method. EDAX (Energy Dispersive Analysis of x-rays) has shown that the prepared samples are in stoichiometry without any kind of impurities. Rietveld refinement XRD (x-ray diffraction) pattern confirmed the orthorhombic crystal structure and showed good crystallinity of all the samples with increase in Fe content. The unit cell volume is found to be varied from 12.34 nm to 19.39 nm. HRTEM (High Resolution Transmission Electron Microscopy) has shown that the prepared nanostructures are nanorods and nanocylinders with high crystallinity and corroborates with our XRD results. Diffuse reflectance spectroscopy analysis indicated that the band gap has increased from 1.550 eV for pure Bi2S3 to 1.592 eV for Fe0.08Bi1.92S3 nanostructures reflecting the blue shift compared to bulk sample. The photoluminescence spectra (PL) recorded with 250 nm excitation wavelength for powder samples has shown that with increase in Iron concentration the intensity of 440 nm peak increases whereas the peaks at 470 nm and 510 nm decreases. The PL spectra is also recorded for nanostructures dispersed in liquid media and has shown that the peaks at 501 nm is observed while rest of the two peaks are quenched. Raman spectra dependent on temperature is obtained for FexBi2-xS3 (x = 0.0, 0.4, 0.6, 0.8 wt%) samples in pellet form in the range of 80 K to 280 K. All samples have shown B1g and Ag phonon modes with higher intensity. The Gruneisen parameter determined for B1g mode varies from 1.21 to 14.13 whereas for Ag mode it varies from 0.60 to 7.91 with the exception of a negative value of −3.10 for Fe0.06Bi1.94S3 sample. VSM (vibrating sample magnetometer) showed the diamagnetic behavior of Bi2S3 and ferromagnetic behaviour of FexBi2-xS3 (x = 0.0, 0.4, 0.6, 0.8 wt%) samples. The saturation magnetization is found to be reaching to a value of 127.5 emu gm−1 for 0.6 wt% of Fe doping in Bi2S3 and then decreases drastically to 40.34 emu gm−1 for 0.8 wt% Fe doping. The antibacterial efficacy showed that as Fe concentration increases, the MIC (minimal inhibitory concentration) fluctuates between 60 to 70 μg ml−1 and is found to be maximum for Fe0.08Bi1.92S3 sample. It is also found that Fe0.04Bi1.96S3 nanostructures show the lowest MIC value for Gram +ve and Gram –ve bacteria in comparison to Bi2S3 nanostructures.

A novel reverse micelle based cationic double nanoemulsion as a potential nanoplatform for enhancing the anitglucomal activity of betaxolol hydrochloride; formulation, in vitro characterization, ex vivo permeation and in vivo pharmacodynamic evaluation in glaucomatous rabbits’ eyes

Glaucoma is one of the most common causes of irreversible vision loss worldwide. The hydrophilic nature of the anti-glaucoma drug Betaxolol hydrochloride (BH) limits its ocular permeation necessitating repeated dosing. This can reduce patient compliance and increase the risk of experiencing adverse side effects. Our research is the first to encapsulate BH into reverse micelle-based cationic double W1/O/W2 nanoemulsions (RM-CDNEs) as a new platform capable of enhancing both the corneal permeability and IOP lowering efficacy of this drug. BH-loaded RM-CDNEs were prepared by a modified two-step emulsification method using sonication technique and applying 24 full factorial design to assess the impact of formulation variables and select the optimal delivery system. The in vitro drug-release, ex vivo permeation and in vivo performance of this novel nanocarrier were also assessed. The optimal delivery system (RM-CDNE 10) has mean DS, PDI, ZP and entrapment efficiency of 46.53 ± 1.30 nm, 0.217 ± 0.02, +40.9 ± 5.04 mV and 95.1 ± 2.44 %, respectively. A 90.77 % of drug was released over 7h. RM-CDNE 10 showed 2.5-fold increase in ex vivo corneal BH permeation with a prolonged IOP reduction of 58.77 % ± 1.18 % and AUC0-48 of 2537.82 ± 12.8%h. While, the marketed product (Epitaxol®) had only 33.63 ± 1.54 % IOP reduction with AUC0–48 h of 823.14 ± 3.67%h when tested in rabbits (P ≤ 0.05). Histopathological and Draize irritation studies confirmed that RM-CDNEs were non-irritant. These findings proved that the novel BH-loaded RM-CDNEs system improved the outcomes for patients suffering from glaucoma and thus decreasing the liability for disease progression into blindness.