Formation and Stabilization of Noble Metal Nanoparticles

The kinetics of homogeneous and heterogeneous nucleation processes of metal (Ag, Pd) nanoparticles was studied by UV-VIS spectrometry. Silver nanoparticles were prepared in aqueous solution by homogeneous nucleation using poly(vinylpyrrolidone) (PVP) and sodium citrate as sterical stabilizers. Reduction was ensured by adding hydroquinone. According to kinetic functions, reduction is an autocatalytic process: a slow, continuous nucleation is followed by a fast, autocatalytic growth. The presence of polymer inhibits nucleation and retards the rate of particle growth. Formation of palladium nanoparticles was investigated in aqueous medium via reduction by hydrazine, using PVP and the clay mineral hectorite as stabilizers. Effects of the polymer and concentration of silicate and palladium ions on the particle formation rate were analyzed. The rate of reduction is decreased by increasing amounts of stabilizing agents and increased by increasing concentrations of precursor ions. The kinetics of heterogeneous nucleation was determined based on the adsorption of the palladium species at the clay mineral particles and the viscosity of the hectorite dispersion

Formation and Stabilization of Noble Metal Nanoparticles

The kinetics of homogeneous and heterogeneous nucleation processes of metal (Ag, Pd) nanoparticles was studied by UV-VIS spectrometry. Silver nanoparticles were prepared in aqueous solution by homogeneous nucleation using poly(vinylpyrrolidone) (PVP) and sodium citrate as sterical stabilizers. Reduction was ensured by adding hydroquinone. According to kinetic functions, reduction is an autocatalytic process: a slow, continuous nucleation is followed by a fast, autocatalytic growth. The presence of polymer inhibits nucleation and retards the rate of particle growth. Formation of palladium nanoparticles was investigated in aqueous medium via reduction by hydrazine, using PVP and the clay mineral hectorite as stabilizers. Effects of the polymer and concentration of silicate and palladium ions on the particle formation rate were analyzed. The rate of reduction is decreased by increasing amounts of stabilizing agents and increased by increasing concentrations of precursor ions. The kinetics of heterogeneous nucleation was determined based on the adsorption of the palladium species at the clay mineral particles and the viscosity of the hectorite dispersion

Önszerveződő hibrid filmek előállítása nanoszerkezetű anyagokból = Preparation of self-assembled hybrid films from nanostructured materials

Önszerveződő hibrid nanofilmek előállítását, szerkezeti és optikai tulajdonságait vizsgáltuk különböző kolloidokból felépíthető ultravékony rétegekben. Funkcionált felületű nanorészecskékből szabályozott szerkezetű nanohibrid ultravékony filmeket készítettünk. A félvezető-oxidok közül a cink-oxid részecskéket alkalmaztuk önszerveződő filmek építéséhez és szenzorok előállításához. Réteges szerkezetű nanolamellás rendszerek kiváló önszerveződő tulajdonságokkal rendelkeznek a lamellák anizometrikus dimenziói miatt. A hibrid rétegek további komponensei lehetnek polimerek, peptidek és fehérjék is. Az önrendeződés folyamatát kétdimenziós kísérletekben Langmuir-mérleggel is követtük és jellemeztük a filmek kompresszibilitását. Az ezüst plazmonikus tulajdonságait kihasználva a látható fényben gerjeszthető fotokatalizátorokat készítettünk és azok hatékonyságát fotooxidációs reakciókkal minősítettük. Kvázi-kétdimenziós optikai reflexiós spektroszkópiával tanulmányoztuk a hidrofil és hidrofób nanohibrid filmeket. Funkcionalizált arany részecskékkel gőzök adszorpciójára szenzitív interdigitális szenzorokat fejlesztettünk ki. Aminosavak funkcionalizáló hatását tanulmányoztuk, és a plazmonikus anyagok felületén bekövetkező szorpciós folyamatok alkalmasak az ezüst valamint az arany nanorészecskék felületén megkötött biokolloidok tulajdonságainak optikai jelzésére. Ez a módszer kifejleszthető gyógyszer hatóanyagok megkötésének kvantitatív detektálására protein szupramolekulákra. | Structural and optical properties of self-assembled hybrid nanofilms prepared from different colloids were investigated. The nanohybrid ultrathin films with tailored structure were prepared from functionalized nanoparticles. Semiconductor metal oxide (zinc oxide) nanoparticles were applied for the construction of self assembled films for sensor application. The layered structured nanolamellar systems exhibit excellent self assembled properties because of the anisometric dimensions of the lamellae. Further components of the hybrid layers may also involve polymers, peptides and proteins as well. The self-assembly process was controlled by two dimensional Langmuir-balance measuring the compressibility of the films. The plasmonic properties of silver were exploited for photocatalysis. The catalysts can be excited in visible light and their efficiency in photooxidation reactions was determined. Quasi-two dimensional optical reflection spectroscopy on hydrophilic and hydrophobic nanohybrid films were studied using setup developed in our laboratory. Gold nanoparticles were deposited on interdigital sensor surfaces measuring the vapours adsorption. The effect of surface functionalization by amino acids were also studied. The sorption processes are able to modify the optical signal on the surface of plasmonic materials for biocolloids on plasmonic surfaces. This method can be developed for quantitative characterization of pharmaceutical drug materials binding on supramolecules

Amino Acid Complexes of Zirconium in a Carbon Composite for the Efficient Removal of Fluoride Ions from Water

Amino acid complexes of zirconia represent an entirely new class of materials that were synthesized and studied for the first time for the decontamination of fluoride ion containing aqueous solutions. Glutamic and aspartic acid complexes of zirconia assembled with thin carbon (stacked graphene oxide) platelets deriving from graphite oxide (GO) were synthesized by a two-step method to prepare adsorbents. The characterization of the complexes was carried out using infrared spectroscopy to determine the functional groups and the types of interaction between the composites and fluoride ions. To reveal the mechanisms and extent of adsorption, two types of batch adsorption measurements were performed: (i) varying equilibrium fluoride ion concentrations to construct adsorption isotherms at pH = 7 in the absence of added electrolytes and (ii) using fixed initial fluoride ion concentrations (10 mg/L) with a variation of either the pH or the concentration of a series of salts that potentially interfere with adsorption. The experimental adsorption isotherms were fitted by three different theoretical isotherm equations, and they are described most appropriately by the two-site Langmuir model for both adsorbents. The adsorption capacities of Zr-glutamic acid-graphite oxide and Zr-aspartic acid-graphite oxide are 105.3 and 101.0 mg/g, respectively. We found that two distinct binding modes are combined in the Zr-amino acid complexes: at low solution concentrations, F(−) ions are preferentially adsorbed by coordinating to the surface Zr species up to a capacity of ca. 10 mg/g. At higher concentrations, however, large amounts of fluoride ions may undergo anion exchange processes and physisorption may occur on the positively charged ammonium moieties of the interfacially bound amino acid molecules. The high adsorption capacity and affinity of the studied dicarboxylate-type amino acids demonstrate that amino acid complexes of zirconia are highly variable materials for the safe and efficient capture of strong Lewis base-type ions such as fluoride

Béta-amiloid peptidek aggregációja és kölcsönhatása fehérjékkel; új neuroprotektív vegyületek alkalmazása az Alzheimer-kór megelőzésére = Beta-amyloid aggregation and interaction with proteins; novel neuroprotective compounds for prevention of Alzheimer's disease

Új, standardizálható módszert dolgoztunk ki toxikus �béta-amiloid (Abéta) 1-42 peptid oligomerek előállítására, a preparált oligomereket fiziko-kémiai módszerekkel jellemeztük. Két új neuroprotektív peptidmimetikum vegyületcsaládot találtunk, ezek az anyagok megvédik a neuronokat az Alzheimer-kór (AK) állatmodelljében az Abéta neurotoxikus hatásától. Mindkét vegyületcsoportot szabadalmilag védjük, mint az AK potenciális gyógyszerjelölt vegyületeit. Új ex vivo módszert dolgoztunk ki az Abéta peptidek toxicitásának mérésére (patkány hippocampus szelet, MTT-teszt), a módszer alkalmas az új neuroprotektív vegyületeink aktivitásmérésére is. Az ex vivo hippocampus szeleteket sikerrel alkalmaztuk a neuronális plaszticitás (LTP) mérésére, az Abéta-toxicitás meghatározására, multielektród array (MEA) technikával. In vivo, egysejt-elvezetéses elektrofiziológiai mérésekkel bizonyítottuk az új peptidmimetikumaink neuroprotektív hatását. Proteomikai módszerekkel azonosítottuk az Abéta peptidekkel kölcsönhatásba lépő fehérjéket, ezek elsősorban plazmamembrán, ill. intraneuronális fehérjék (mitokondrium, endoplazmás reticulum, mikrotubuláris rendszer). Az intraneuronális fehérjék és az Abéta peptidek kölcsönhatásai kulcsszerepet játszhatnak az AK patogenezisében. Igazoltuk, hogy a Zn2+ ionok toxikus Abéta-aggregátumok képződését indukálják. Az AK transzgén állatmodelljén bizonyítottuk, hogy a Zn-kelátorok (pl. Perindopril) neuroprotektív hatásúak. Új AK-állatmodellt dolgoztunk ki az Abéta oligomerek icv bevitelével. | A new method was introduced for the preparation of toxic beta-amyloid (Abeta) 1-42 oligomers, these assemblies were characterized with physicochemical methods. Two families of novel neuroprotective peptidomimetics were found, these substances protect neurons against the toxic effect of Abeta in tg mouse models of Alzheimer’s disease (AD). Both groups of the novel substances will be patented as putative drug candidates for AD treatment. A new ex vivo method was introduced for toxicity measurement of Abeta peptides (rat hippocampal slices, MTT-assay); this method proved to be suitable for activity measurement of the novel neuroprotective substances. Hippocampal slices were successfully used for measurement of neuronal plasticity (LTP) for demonstrating neurotoxicity of Abeta aggregates, applying multielectrode array (MEA) technique. The neuroprotective effect of our novel peptidomimetics was demonstrated also in vivo, using one-cell electrophysiology. Proteomic methods were used for identification of proteins interacting with Abeta peptides; these are mainly plasma membrane and intraneuronal (mitochondrial, endoplasmatic reticular and microtubular) proteins. Interaction of intracellular proteins with Abeta may play key role in AD pathogenesis. The role of Zn2+ ions in formation of toxic Abeta-aggregates was demonstrated. Zn2+-chelators (e.g. Perindopril) were neuroprotective in a tg-mouse model of AD. A new AD rat model was introduced using icv administration of synthetic Abeta oligomers

Caracteres anatómicos y fitoquímicos del tallo y raíz de Mammillaria uncinata (Cactaceae)

Background and Aims: Members of the Cactaceae family persist through anatomical and metabolic adaptations that allow them to develop in arid and semi-arid areas, including the synthesis of primary and secondary metabolites with specific functions. Mammillaria is a genus belonging to the Cacteae tribe and the literature on its anatomical and phytochemical characters is scarce, particularly for the species Mammillaria uncinata. Therefore, the objectives of this study were to describe the anatomical-histochemical structure and phytochemical profile of the stem and root of Mammillaria uncinata, in order to contribute to the knowledge of biology and chemical composition of the species. Methods: The study was conducted with specimens collected in their natural distribution area in the Altos Norte region of Jalisco, Mexico. The standard paraffin microtechnique and histochemical techni¬ques were used for the description of the anatomical and histochemical characters, whereas qualitative techniques were applied to study the phytochemical profile. Key results: Laticifers and crystals of variable morphology in the stem are some of the most distinctive characters. The phytochemical profile analysis revealed the presence of abundant metabolites in the stem, including alkaloids, sterols, flavonoids and saponins, whereas in the root only the presence of sterols and saponins was detected in low amounts. Conclusions: The study showed anatomical features in Mammillaria uncinata to be similar to other Cactaceae species, as well as abundance of phytochemicals with potential application in different areas.Antecedentes y Objetivos: Los integrantes de la familia Cactaceae subsisten a través de adaptaciones anatómicas y metabólicas como la síntesis de metabolitos primarios y secundarios con funciones específicas que les permiten desarrollarse en regiones áridas y semiáridas. Mammillaria es un género perteneciente a la tribu Cacteae y la literatura con respecto a sus caracteres anatómicos y fitoquímicos es escasa. Particularmente para la especie Mammillaria uncinata los estudios con ese tipo de enfoque son ausentes, por lo que los objetivos del presente trabajo fueron describir la estructura anatómica-histoquímica y el perfil fitoquímico del tallo y la raíz de la especie con la finalidad de contribuir al conocimiento de su biología y composición química. Métodos: El estudio se realizó con ejemplares recolectados en la región Altos Norte de Jalisco, México. Se emplearon la microtécnica convencional de inclusión en parafina y técnicas histoquímicas para la descripción de los caracteres anatómicos e histoquímicos, así como técnicas cualitativas para el estudio del perfil fitoquímico. Resultados clave: Algunos de los caracteres anatómicos más distintivos son laticíferos que producen un látex lechoso y cristales de morfología variable en el tallo. El análisis del perfil fitoquímico reveló la presencia abundante de metabolitos secundarios en el tallo, incluyendo alcaloides, esteroles, flavonoides y saponinas, mientras que en la raíz únicamente se detectó, de manera escasa, la presencia de esteroles y saponinas. Conclusiones: El estudio mostró la presencia, en Mammillaria uncinata, de caracteres anatómicos similares a otras especies de Cactaceae, así como la abundancia de fitoquímicos con potencial aplicación en diferentes áreas

Caracteres anat\uf3micos y fitoqu\uedmicos del tallo y ra\uedz de Mammillaria uncinata (Cactaceae)

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