A drug delivery system based on mesoporous particles MCM-41 was post-synthetically modified by photo-sensitive ligand, methyl-(2E)-3-(4-(triethoxysilyl)-propoxyphenyl)-2-propenoate (CA) and the pores ...of MCM-41 particles were loaded with Naproxen sodium salt (NAP). The CA was used as a photoactive molecule that can undergo a reversible photo-dimerization by 2π + 2π cycloaddition when irradiated with UV light of specific wavelengths. Thus, it has a function of gate-keeper that is responsible for opening/closing the pores and minimizing premature release of NAP. The physicochemical properties of the prepared system were studied by infrared spectroscopy (IR), nitrogen adsorption measurements, thermogravimetric analysis (TGA), scanning transmission electron microscopy (STEM) and energy dispersive X-ray spectroscopy (EDX). The mechanism of the opening/closing pores was confirmed by UV measurements. In vitro and in vivo drug release experiments and the concentration of released NAP was determined by UV spectroscopy and high-performance liquid chromatography (HPLC). In vivo drug release in the blood circulatory system of rats has demonstrated the effective photo-cleavage reaction of CA molecules after UV-light stimulation. The localization and morphological changes of the particles were studied in the blood and liver of rats at different time intervals. The particles in the blood have been shown to retain their original rod-like shape, and the particles in the liver have been hydrolysed, which has resulted in spherical shape with a reduced size.
The Fe3O4@SiO2@ZnO composite was synthesized via the simultaneous deposition of SiO2 and ZnO onto pre-prepared Fe3O4 nanoparticles. Physicochemical methods (TEM, EDXS, XRD, SEM, FTIR, PL, zeta ...potential measurements, and low-temperature nitrogen adsorption/desorption) revealed that the simultaneous deposition onto magnetite surfaces, up to 18 nm in size, results in the formation of an amorphous shell composed of a mixture of zinc and silicon oxides. This composite underwent modification to form Fe3O4@SiO2@ZnO*, achieved by activation with H2O2. The modified composite retained its structural integrity, but its surface groups underwent significant changes, exhibiting pronounced catalytic activity in the photodegradation of methyl orange under UV irradiation. It was capable of degrading 96% of this azo dye in 240 min, compared to the initial Fe3O4@SiO2@ZnO composite, which could remove only 11% under identical conditions. Fe3O4@SiO2@ZnO* demonstrated robust stability after three cycles of use in dye photodegradation. Furthermore, Fe3O4@SiO2@ZnO* exhibited decreased PL intensity, indicating an enhanced efficiency in electron-hole pair separation and a reduced recombination rate in the modified composite. The activation process diminishes the electron-hole (e−)/(h+) recombination and generates the potent oxidizing species, hydroxyl radicals (OH˙), on the photocatalyst surface, thereby playing a crucial role in the enhanced photodegradation efficiency of methyl orange with Fe3O4@SiO2@ZnO*.
A chemical method was successfully used to synthesize silver nanoparticles (AgNPs) with various shapes. The shape of the nanoparticles affects the color of the colloid (spherical—yellow solution, ...triangular—blue, a mixture of spherical and triangular—green). The NaBH4, which acts as the main reducing agent and H2O2 have a significant impact on the shape of AgNPs. It has also been shown that the ratio between precursor, reducing, and the stabilizing agent is crucial for the formation of the required nanoparticles. The light sensitivity of AgNPs and the presence of H2O2 lead to a significant change in AgNPs’ shape and size with time and to the formation of the dichroic effect. UV–vis spectrophotometry, TEM, SEM/FIB, and EDX methods were used to analyze the shape, size, and composition of the nanoparticles. Polymer matrix composite with AgNPs was prepared by the “ex-situ” method.
The aim of the work was to prepare a polymer matrix composite doped by silver nanoparticles and analyze the influence of silver nanoparticles (AgNPs) on polymers' optical and toxic properties. Two ...different colloids of AgNPs were prepared by chemical reduction. The first colloid, a blue one, contains stable triangular nanoparticles (the mean size of the nanoparticles was ~75 nm). UV-vis spectrophotometry showed that the second colloid, a yellow colloid, was very unstable. Originally formed spherical particles (~11 nm in diameter) after 25 days changed into a mix of differently shaped nanoparticles (irregular, triangular, rod-like, spherical, decahedrons, etc.), and the dichroic effect was observed. Pre-prepared AgNPs were added into the PVA (poly(vinyl alcohol)) polymer matrix and PVA-AgNPs composites (poly(vinyl alcohol) doped by Ag nanoparticles) were prepared. PVA-AgNPs thin layers (by a spin-coating technique) and fibers (by electrospinning and dip-coating techniques) were prepared. TEM and SEM techniques were used to analyze the prepared composites. It was found that the addition of AgNPs caused a change in the optical and antibiofilm properties of the non-toxic and colorless polymer. The PVA-AgNPs composites not only showed a change in color but a dichroic effect was also observed on the thin layer, and a good antibiofilm effect was also observed.
Acute respiratory distress syndrome (ARDS) is a life-threatening condition characterized by the rapid onset of lung inflammation Therefore, monitoring the spatial distribution of the drug directly ...administered to heterogeneously damaged lungs is desirable. In this work, we focus on optimizing the drug
-acetylcysteine (NAC) adsorption on poly-l-lysine-modified magnetic nanoparticles (PLLMNPs) to monitor the drug spatial distribution in the lungs using magnetic resonance imaging (MRI) techniques. The physicochemical characterizations of the samples were conducted in terms of morphology, particle size distributions, surface charge, and magnetic properties followed by the thermogravimetric quantification of NAC coating and cytotoxicity experiments. The sample with the theoretical NAC loading concentration of 0.25 mg/mL was selected as an optimum due to the hydrodynamic nanoparticle size of 154 nm, the surface charge of +32 mV, good stability, and no cytotoxicity. Finally, MRI relaxometry confirmed the suitability of the sample to study the spatial distribution of the drug in vivo using MRI protocols. We showed the prevailing transverse relaxation with high transverse relaxivity values and a high
*
/
ratio, causing visible hypointensity in the final MRI signal. Furthermore, NAC adsorption significantly affects the relaxation properties of PLLMNPs, which can help monitor drug release in vitro/in vivo.
The research aimed to observe the influence of the storage conditions of silver colloidal solutions prepared by biological (green) and chemical methods on their long-term stability. Green methods for ...reducing and stabilizing silver nanoparticles (AgNPs) use natural substances. The rosemary leaf extract was used for AgNPs synthesis, and prepared nanoparticles were spherical (average size of 12 nm). In the chemical method, commercial chemicals (NaBH4, TSC, PVP, and H2O2) were used, and two colloids were prepared; the first contained spherical nanoparticles with an average size of 8 nm, and the second triangular prisms with an average size of 35 nm. The prepared colloids were stored under four conditions: at room temperature in the light and the dark, and at a temperature of 5 °C (refrigerator) in the light and the dark. The results confirmed the influence of storage conditions on the stability of nanoparticles. Colloids stored at 5 °C in the dark show the best stability. However, differences in stability dependent on the shape of nanoparticles prepared by chemical method were also observed; triangular nanoparticles showed the least stability. Methods such as UV–vis spectrophotometry, TEM, and EDX were used to analyze the nanoparticles before and after storage.
This study focuses on the preparation and characterization of zinc-based alloys containing magnesium, calcium, and manganese. The alloys were prepared by the melting of pure elements, casting them ...into graphite molds, and thermo-mechanically treating them via hot extrusion. The phase compositions of the samples were analyzed using X-ray diffraction technique and SEM/EDX analysis. The analysis confirmed that in addition to the Zn matrix, the materials are reinforced by the CaZn
, MgZn
and Mn-based precipitates. The mechanical properties of the alloys were ascertained by tensile, compressive, and bending tests, measurement of the samples microhardness and elastic modulus. The results indicate that an increase in Mn content leads to an increase in the maximum stress experienced under both tension and compression. However, the plastic deformation of the alloys decreases with increasing Mn content. This study provides valuable insights into the microstructural changes and mechanical behavior of zinc-based alloys containing magnesium, calcium, and manganese, which can be used to design alloys for specific biomedical applications.
Fabrication and characterization of high entropy pyrochlore ceramics Matović, Branko; Zagorac, Dejan; Cvijović-Alagić, Ivana ...
Boletín de la Sociedad Española de Cerámica y Vidrio (1983),
January-February 2023, 2023-01-00, 2023-01-01, Volume:
62, Issue:
1
Journal Article
Peer reviewed
Open access
Display omitted
High-entropy rare-earth (RE) zirconates with pyrochlore structure were successfully fabricated by pressureless and spark plasma sintering. RE2Zr2O7 compound with nominal composition ...(La0.2Y0.2Gd0.2Nd0.2Sm0.2)Zr2O7 was prepared by simple glycine nitrate procedure (GNP). GNP process yielded powders with low crystallinity and after subsequent calcination, well crystalline ceramics were formed. During calcination defective fluorite (F-RE2Zr2O7) and crystal pyrochlore (Py-RE2Zr2O7) structures coexist. Formation of pure crystalline pyrochlore occurs after sintering at 1450°C. High-density ceramics, free of any additives, were obtained after powders compaction and pressureless (PS), as well as field assisted sintering technique (FAST) at 1450°C. Theoretical investigations of the high-entropy RE2Zr2O7 pyrochlore systems were performed. Unit cell parameter of the obtained Py-RE2Zr2O7 is 10.5892(2)Å and 10.5999(2)Å for PS and FAST sintering, respectively, which is in good agreement with the results of Density Functional Theory (DFT) calculations. The thermal diffusivity of sintered samples at room temperature was ∼0.7mm2/s for both sintering methods.
Se fabricaron con éxito, mediante sinterización por plasma sin presión y por chispa, los circonatos de tierras raras (RE) de alta entropía con estructura de pirocloro. El compuesto RE2Zr2O7 con composición nominal (La0,2Y0,2Gd0,2Nd0,2Sm0,2)Zr2O7 se preparó mediante un procedimiento simple de nitrato de glicina (GNP). El proceso GNP produjo polvos con baja cristalinidad y después de la posterior calcinación, se formaron cerámicas bien cristalinas. Durante la calcinación coexisten estructuras defectuosas de fluorita (F-RE2Zr2O7) y pirocloro cristalino (Py-RE2Zr2O7). La formación de pirocloro cristalino puro se produce después de la sinterización a 1.450°C. Después de la compactación de polvos y sin presión (PS), así como por la técnica de sinterización asistida en campo (FAST) a 1.450 oC, se obtuvieron cerámicas de alta densidad, libres de aditivos. Se realizaron investigaciones teóricas de los sistemas de pirocloro RE2Zr2O7 de alta entropía. El parámetro de celda unitaria del Py-RE2Zr2O7 obtenido es 105.892(2) Å y 105.999(2) Å para la sinterización PS y FAST, respectivamente, lo que está de acuerdo con los resultados de los cálculos de la teoría funcional de la densidad (DFT). La difusividad térmica de las muestras sinterizadas a temperatura ambiente fue de ∼ 0,7 mm2/s para ambos métodos de sinterización.
The aim of this work was to propose a simple method for synthesizing differently shaped AgNPs and to find a suitable stabilizing/capping agent to ensure the non-toxicity of AgNPs. Using a chemical ...method, by simply changing the volume of reducing agents, we successfully prepared colloids of differently shaped AgNPs (spherical (~10 nm), triangular (~40 nm), rodlike (~30 nm), and a mixture of these shapes). The nanoparticle sizes and shapes affect the solution color. UV-VIS spectroscopy was used to evaluate the colloidal solutions, and transmission electron microscopy was used to analyze the shape and size of the nanoparticles. To create non-toxic and stable AgNPs, it is necessary to modify the surface properties of the nanoparticles; one possibility is to create a biocompatible layer on the nanoparticle surface. We successfully applied a combination of trisodium citrate and polyvinylpyrrolidone, thereby preventing the release of silver ions, which are responsible for the toxic effects of AgNPs. The synthesized nanoparticles show very low, mostly negligible antibiofilm activity against the green algae Chlorella kessleri. AgNPs were used to prepare polymer-AgNP composite thin layers and fibers. It was proved that AgNPs can influence polymer matrix properties.
The properties of planar sensors based on tin dioxide and indium oxide used for the determination of acetone vapors have been studied. Sensors based on synthesized SnO2 and In2O3 nanopowders showed ...high sensitivity to low concentrations of acetone in a humid environment which simulates human exhalation. The addition of a small amount of AuIII ions to hydroxide sols significantly increases the threshold sensitivity and the sensor response in a wide range of acetone concentrations. In2O3–Au sensors have the maximum sensitivity at an operating temperature of 325 °C. The In2O3–Au-sensors reliably record the change in acetone concentration in the concentration range from a minimum of 0.1 to 5 ppm with high accuracy, which is necessary for rapid diagnostics of the condition of patients with diabetes (1.8–5.0 ppm). The high sensitivity of the obtained sensors is explained by the structural features and the surface conditions of oxides and gold nanoparticles, which depend on the sample synthesis conditions.
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