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The advances of iron based magnetic nanoparticles are extensively increasing due to the number of sources related to the synthesis process, the control on the particle dispersion and the interactions of ferrofluids that can be provide with different surface modifications. The wide range of uses granted to them are based on the physical, chemical stability and interaction properties in the different yields of material science. In this work, ferromagnetic iron carbide@iron oxide core@shell nanoparticles were synthesized with hydrophobic nature. Water dispersity was controlled by modifying the surface with a synthesized molecule of oleic acid with ethylenediamine by bioconjugation reaction obtaining a conjugated amide-amine modified oleic acid coating 6 nm magnetic nanoparticles with the capacity of being water dispersable. The synthesized nanoparticles, with modified organic acid and surface modified nanoparticle were characterized by TEM, DLS, zeta potential, mass spectrometry, FTIR and NMR.

Nowadays, new technologies are being developed for the removal of heavy metals, which are intended to have low operating costs and easy to implement. The copper and zinc bioadsorption in batch system was studies in pre-treated, with sodium hydroxide, and untreated Escherichia coli dried biomass . The E. coli was isolated and identified from water samples from the San Pedro river, Sonora, Mexico. The dry biomass of E. coli was pretreated with 0.1 N sodium hydroxide. The optimal biosorption conditions were at pH 5, 30 oC and 100 rpm. These studies demonstrated the effectiveness of the pre-treated biomass in determining the maximum bioadsorption capacity using the Langmuir model, and they were for copper of 204.49 mg/g and zinc of 151.97 mg/g, and for biomass untreated with copper and zinc were 107.52 mg/g and 125 mg/g, respectively. In addition, with the characterization by scanning electron microscopy and dispersive energy spectroscopy, the presence of copper and zinc were observed. The absorption bands by Fourier transform infrared spectrophotometry confirmed carboxyl, hydroxyl, amino and phosphate groups on the surface of E. coli . The use of dry biomass of pre-treated Escherichia coli in this study, showed to be effective in the bioadsorption process.

One of the main challenges facing materials science today is the synthesis of new biodegradable and biocompatible materials capable of improving existing ones. This work focused on the synthesis of new biomaterials from the bioconjugation of oleic acid with L-cysteine using carbodiimide. The resulting reaction leads to amide bonds between the carboxylic acid of oleic acid and the primary amine of L-cysteine. The formation of the bioconjugate was corroborated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and nuclear magnetic resonance (NMR). In these techniques, the development of new materials with marked differences with the precursors was confirmed. Furthermore, NMR has elucidated a surfactant structure, with a hydrophilic part and a hydrophobic section. Ultraviolet-visible spectroscopy (UV-Vis) was used to determine the critical micellar concentration (CMC) of the bioconjugate. Subsequently, light diffraction (DLS) was used to analyze the size of the resulting self-assembled structures. Finally, transmission electron microscopy (TEM) was obtained, where the shape and size of the self-assembled structures were appreciated.

The freezing-thawing is an advantageous method to produce hydrogels without crosslinking agents. In this study chitosan-poly(vinyl alcohol) (CS-PVA) hydrogels were prepared by varying the freezing conditions and composition, which affect the final characteristics of the products. The swelling degree, morphology, porosity, and diflunisal drug loading, as well as the drug release profiles were evaluated. The hydrogel swelling ratio was found to be mainly affected by the CS content, the number of freezing cycles and the temperature. SEM micrographs and porosity data confirm that pore size increases with the chitosan content. However, the use of either lower temperatures or longer freezing times, results in higher porosity and smaller pores. The drug release times of the CS-PVA hydrogels were as long as 30 h, and according to the mathematical fitting, a simple diffusion mechanism dominates the process. Moreover, a mathematical model predicting the hydrogels physical and structural behavior is proposed.

A core-shell of colloidal metal-responsive polymer provides an innovative model in functional materials. These core-shell nanocomposites offer the possibility to control some properties, such as particle size, surface plasmon resonance and morphology. In this research, we demonstrate the successful synthesis and functionality of gold nanorods (GNR) coated with the polymers chitosan (Ch) and poly(N-isopropylacrylamide) (PNIPAM). The polymer coatings are performed using a two-step method. First, GNR were coated with a thiolated chitosan (GNR-Ch) by replacing hexadecyltrimethylammonium bromide with a chitosan thiomer. Structural modification of GNR-Ch was monitored by Fourier transform infrared spectroscopy. Then a second polymeric coating was done by in situ free radical polymerization of N-isopropylacrylamide (NIPAM) on GNR-Ch to obtain the nanocomposite GNR-Ch-PNIPAM. The nanocomposite average size was analyzed by dynamic light scattering. The evolution of ζ potentials during the coatings was measured using electrophoretic mobility. GNR-Ch-PNIPAM presented a collapsed structure when heated above the lower critical solution temperature. The particle size of GNR-Ch-PNIPAM was manipulated by changing the pH. Plasmonic properties were evaluated by UV-Vis spectroscopy. Results showed an important blue shift due to the PNIPAM coating thickness. Thermo- and pH-responsive properties of the nanocomposite GNR-Ch-PNIPAM could be used as a drug delivery system.

The delivery of photosensitizer compounds using biodegradable nanoparticles could improve dosage, controlled release and its bioavailability. In this study, methylene blue (MB) loaded PLGA nanoparticles (MB-PNP) are prepared by a new approach combining single and double emulsification techniques. Comparisons of MB-PNP obtained with the combined and the individual techniques are presented. Nanoparticles are characterized by dynamic light scattering, laser Doppler electrophoresis and scanning electron microscopy. Particles prepared by the combined technique presented hydrodynamic diameters of 186 nm. The sizes of MB-PNP obtained from the single emulsion technique are similar to the combined technique, while the diameter of particles prepared by double emulsion increased from 201 nm to 287 nm as the TDL increased. MB-PNP displayed an average zeta potential between −21 mV and −28 mV for all formulations. MB loading ranges between 0.3–1.4%, while the encapsulation efficiency ranges from 8–14%, both depending on the TDL and the preparation technique. In vitro release studies show a monophasic release profile that was analyzed by considering the mechanisms of initial burst, drug diffusion and a combination of them. Experimental results could be better described using a mathematical model of release that simultaneously combines the mechanisms of initial burst and drug diffusion. The approach presented to encapsulate MB and also to analyze the drug release could be extended to other drugs with partial solubility.

This study presents the influence of the primary formulation parameters on the formation of poly-DL-lactic-co-glycolic nanoparticles by the emulsification-solvent evaporation, and the nanoprecipitation techniques. In the emulsification-solvent evaporation technique, the polymer and tensoactive concentrations, the organic solvent fraction, and the sonication amplitude effects were analyzed. Similarly, in the nanoprecipitation technique the polymer and tensoactive concentrations, the organic solvent fraction and the injection speed were varied. Additionally, the agitation speed during solvent evaporation, the centrifugation speeds and the use of cryoprotectants in the freeze-drying process were analyzed. Nanoparticles were characterized by dynamic light scattering, laser Doppler electrophoresis, and scanning electron microscopy, and the results were evaluated by statistical analysis. Nanoparticle physicochemical characteristics can be adjusted by varying the formulation parameters to obtain specific sizes and stable nanoparticles. Also, by adjusting these parameters, the nanoparticle preparation processes have the potential to be tuned to yield nanoparticles with specific characteristics while maintaining reproducible results.

In this work, the synthesis and characterization of core/shell nanoparticles of iron carbide@iron oxide (Fe3C/&gamma, Fe2O3) encapsulated into micelles of sodium dodecylsulfate and oleic acid and stabilized with chitosan was developed. The materials were sonosynthesized at low intensities using standard ultrasonic baths with iron pentacarbonyl (Fe(CO)5) and oleic acid as iron source and hydrophobic stabilizer, respectively, obtaining nanoparticles with a hydrodynamic diameter of 19.71 nm and polydispersive index (PDI) of 0.13. The iron carbide@iron oxide nanoparticles (ICIONPs) in oleic acid were used as the organic phase during the self-assemble of nanoemulsion with sodium dodecylsulfate in water to obtain the metastable micelles. The final step involved the stabilization of the micelles using low molecular weight chitosan solution at 2% in acetic acid by ultrasonication bath. The nanosystem showed a hydrodynamic diameter of 185.30 nm, a PDI of 0.15 with a superficial charge &zeta, of 36.70 mV. Due to the magnetic, physical and chemical properties previously measured of the ICIONPs, it is believed that this type of nanoparticles can be used as a possible nanomedicine agent.

Here we demonstrate a simple method for the organic sonosynthesis of stable Iron Carbide@Iron Oxide core-shell nanoparticles (ICIONPs) stabilized by oleic acid surface modification. This robust synthesis route is based on the sonochemistry reaction of organometallic precursor like Fe(CO)5 in octanol using low intensity ultrasonic bath. As obtained, nanoparticles diameter sizes were measured around 6.38 nm ± 1.34 with a hydrodynamic diameter around 25 nm and an estimated polydispersity of 0.27. Core-Shell structure of nanoparticles was confirmed using HR-TEM and XPS characterization tools in which a core made up of iron carbide (Fe3C) and a shell of magnetite (γ-Fe2O3) was found. The overall nanoparticle presented ferromagnetic behavior at 4 K by SQUID. With these characteristics, the ICIONPs can be potentially used in various applications such as theranostic agent due to their properties obtained from the iron oxides and iron carbide phases.

A synthetic route is demonstrated to build purely polymeric nanostructured multilayer coatings, adaptable to arbitrary surfaces, and capable of effi ciently blocking by refl ection a targeted and tunable ultraviolet (UV) range. Refl ection properties are determined by optical interference between UV light beams refl ected at the interfaces between polystyrene layers of different porosity and hence refractive index. As no dopant absorber intervenes in the shielding effect, polymer degradation effects are prevented. Alternated porosity results from the modulation of photochemical effects at the few tens of nanometers length scale, combined with the collective osmotic shock induced during the processing of the precursor diblock copolymer fi lm. Experimental evidence of the application of this method to coat rough surfaces with smooth and conformal UV protecting fi lms is provided

The handling of metallic nanoparticles often requires their dispersion into several polar and nonpolar solvents. Solid-phase stages or polymer-based ligands are commonly required to complete the transfer. The construction of a thiol ligand based in oleic acid, and its ability to efficiently assist in gold and silver nanoparticle aqueous–organic phase transfer is reported. After the transfer, the particles are completely dispersed in an organic solvent, preserving their diameter and morphology, as confirmed by ultraviolet–visible spectroscopy and scanning transmission electron micrographs.

National Council of Science and Technology (CONACyT) [INFR-226208-2014, INFR-255791-2015]; CONACYT

The use of ceramic surfaces for thermal solar concentrators are not new, but the high costs of fabrication and limited thermal properties have banned the application of such at large scale. Silicon carbide (SiC) is well known due to its high thermo-mechanical properties and spectral absorbance. Because of its capacities to enhance the energy transfer and its resistance to high temperatures silicon carbide have been recognized in our group as a possible improvement to increase the efficiency of electric energy production. At nano-scale SiC shows high surface area and porosity that could be tuned, making it a state-of-the-art material to be used in the application of thermal solar receptors in “Central Tower” power plants. Although the advantages are favorable, the high temperature needs for its synthesis have been an issue for its spread. In the present work, we introduce a novel method to synthesize SiC powders at lower temperature (650 °C) we present also its characterization for the potential application in the concentration of thermal solar energy at high temperatures.