Ag-AgCl nanoparticles fixation on electrospun PVA fibres: Technological concept and progress

Polymer-metal based material with unique 3D structure is an attractive substrate for the development of biomedical applications. A novel preparation of the composite from polymer fibres and silver nanoparticles has been designed through: (1) preparation of silver nanoparticles by phytosynthesis and (2) incorporation of these nanoparticles in a fibrous membrane prepared by electrospinning. The nanoparticle biosynthesis was performed in a pure environmental-friendly, easy, static, bottom-up in vitro regime using Tilia sp. leachate. TEM and XRD depict the formation, stabilisation and encapsulation of crystalline silver (14 +/- 9 nm) nanoparticles (NPs) in one simple step with low tendency to aggregate. We achieved successful incorporation in the uniform electrospun 221 +/- 24 nm poly(vinylalcohol) fibres, and this confirms the possibility of its use in the biomedical field. Both SEM with EDX and TEM analysis determined fibre uniformity with the presence of silver NPs, and ICP-AES confirmed the relatively similar metal concentration throughout the triplicate measurement of fibre structures on the 2 x 2 cm area in the following manner: 0.303 +/- 0.018 wt. %, 0.282 +/- 0.017 wt. %, and 0.281 +/- 0.017 wt. %. Our hypothesis is based on previously verified preparation of active silver NPs and the easily prepared PVA electrospun fibres which act as a water soluble matrix. The simple methodology of incorporating biosynthetically prepared NPs in the PVA fibers highlights the effectiveness of this material, with simple release from water-soluble PVA and final activation of the prepared NPs.Web of Science9art. no. 1552

Colloidal stability of phytosynthesised gold nanoparticles and their catalytic effects for nerve agent degradation

Herein, Tilia sp. bract leachate was used as the reducing agent for Au nanoparticles (Au NPs) phytosynthesis. The colloidal properties of the prepared Au NPs were determined to confirm their stability over time, and the NPs were then used as active catalysts in soman nerve agent degradation. The Au NPs characterisation, reproducibility and stability studies were performed under transmission electron microscopy, ultraviolet visible spectroscopy and with zeta -potential measurements. The reaction kinetics was detected by gas chromatography coupled with mass spectrometry detector and solid-phase micro-extraction to confirm the Au NPs applicability in soman hydrolysis. The 'green' phytosynthetic formation of colloidal crystalline Au NPs with dominant quasi-spherical shape and 55 +/- 10 nm diameter was successfully achieved, and there were no significant differences in morphology, zeta -potential or absorbance values observed during the 5-week period. This verified the prepared colloids' long-term stability. The soman nerve agent was degraded to non-toxic substances within 24 h, with 0.2156 h(-1) reaction rate constant. These results confirmed bio-nanotechnology's great potential in preparation of stable and functional nanocatalysts for degradation of hazardous substances, including chemical warfare agents.Web of Science111art. no. 407

Synthesis and characterization of globular composite nanoparticles C60 using the microemulsion method

Import 26/06/2013Práce se zabývá problematikou přípravy nanočástic novou metodou emulzní krystalizace. V teoretické části je rozebraná problematika přípravy nanočástic, obzvláště mikroemulzní metoda, růstu a nukleace částic, část pojednává o molekule fullerenu a část se zabývá předpokládaným modelem předpovídajícím závislost velikosti nanočástic na koncentraci fullerenů v disperzním prostředí. Tento jednoduchý model se ovšem neshodoval s experimentálními daty, a proto musel být vytvořen nový a komplexnější model. V praktické části jsou shrnuty výsledky analýzy připravených nanočástic. Vlastnosti nanočástic byly zjišťovány metodami DLS, TEM a FTIR spektroskopií.This work is about preparation of nanoparticles using new metod of crystalization in emulsion. In theoretical part there are described methods of preparations of nanoparticles especially microemulsion method, growth and nucleation of particles, part is about fullerene molecule and part is about model of dependence of size on concentration of fullerenes. This simple model did not match the experimantal data so new, more complex model wac created. In experimental part are summarized results of analysis of prepared nanoparticles. Properties of nanoparticles was analyzed by DLS method, transmission electron microscopy (TEM) and FTIR spectroscopy.516 - Institut fyzikyvelmi dobř

Preparation and characterization of carbon-silicate nanosorbents with a high specific surface area

Disertační práce se zabývá přípravou a charakterizací karbon-silikátových nanosorbentů s vysokým specifickým povrchem a možností jejich fotokatalytické regenerace se současnou degradaci sorbátu. Úvodem je shrnuta základní teorie, související s řešenou problematikou. Jedná se o strukturu pevných látek a vazeb, které se v nich vyskytují. Podstatná část je věnována van der Waalsovým interakcím, které se uplatňují ve fyzikální sorpci, a dále pak struktuře povrchu, která má velký význam pro sorpční kapacity a distribuci adsorpčních pozic. Dále je diskutována problematika adsorpce a matematických modelů používaných pro popis adsorpčních procesů. Jsou zde analyzovány hlavní výhody a nevýhody jednotlivých modelů. Následně je popsán proces fotokatalytických reakcí, jejich environmentální aplikace a jejich využití v odstraňování látek z nasyceného sorbentu. V sekci regeneračních procesů jsou rozebrány mechanismy a činidla jednotlivých metod. Pro měření sorpčních a fotokatalytických vlastností byl použit experimentální reaktor pro kontinuální měření fotokatalytických procesů vyvíjený v Laboratoři nanopartikulárních materiálů centra nanotechnologií. Výhodou reaktoru je měření in situ, takže není potřeba zasahovat do systému a narušovat proces. Metoda vakuového vymrazování byla použita pro převod vzorků z vodní disperze na práškovou formu z důvodu lepší manipulace a zachování vysokého specifického povrchu. Proces vývoje sorpčního materiálu se schopností fotokatalytické regenerace se skládal z několika kroků. Nejdříve byly připraveny a charakterizovány fotokatalytické materiály s vysokým specifickým povrchem na bázi síťové silikátové struktury obsahující zinek a grafen. Struktura byla deponována na sorpční vláknitou strukturu z důvodu lepší manipulace. Materiál vykazoval relativně vysoký specifický povrch s hodnotou 410 m2/g a o mnoho lepší výsledky v testech fotokatalytické aktivity než standard P25. Další testovaný materiál, modifikovaný grafitický nitrid uhlíku g-C3N4, už vykazoval schopnost fotokatalytické regenerace. Protože není komerčně dostupný žádný standard sorbentů s fotokatalytickými účinky byl pro srovnání použit oxid titaničitý. Nanokompozit vykazoval vyšší sorbované množství methylenové modři, specifický povrch a rychlostní konstanty sorpčního procesu. Podařilo se u něj provést úspěšně regeneraci sorpčního povrchu pomocí UV záření, ale následující cykly výrazně snižovaly sorpční kapacitu sorbentu. Díky vynechání procesu lyofilizace došlo ke snížení ztrát, ovšem došlo ke ztrátě možnosti kontrolovat množství použitého sorbentu. Dalším krokem bylo zvětšení sorpčních kapacit a vylepšení regeneračních vlastností vzorku úpravou metodiky přípravy. Byl připraven sorbent s vysokým specifickým povrchem a schopností opakované fotokatalytické regenerace ve dvou variantách, a to silikátová struktura s obsahem 10 hm.% g-C3N4 a 20 hm.% g-C3N4. Materiál byl testován na sorpci methylenové modři. Fotokatalytický rozklad probíhal působením LED zdrojem UV záření a přirozeným difúzním slunečním zářením. Efektivita regenerace u obou vzorků přesahovala 84 % po třetím cyklu regenerace UV zářením a 94 % po třetím cyklu regenerace přirozeným slunečním zářením. Regenerace přirozeným slunečním zářením dopadla lépe, díky zapojení grafitizovaného nitridu uhlíku do procesu fotokatalytického rozkladu. Při použití LED zdroje vyzařujícím v oblasti viditelného spektra byly výsledky fotokatalýzy a regenerace nereprodukovatelné.Thesis studied preparation and characterization of carbon-silicate nanosorbents with high specific surface area and with the possibility of photocatalytic regeneration of saturated sorbent. Theoretical part begins with the structure of solids state and the bonds that occur in them. An important part is devoted to the van der Waals interactions that are present in physical sorption and the surface structure which is of great importance for the sorption capacities and the distribution of adsorption positions. The work deals with adsorption and mathematical models used for the description of adsorption processes. The main advantages and disadvantages of each model are highlighted. The process of photocatalytic reactions, their environmental applications and their use in removal of saturated sorbent materials are described next. In the regeneration process section, the mechanisms and reagents of the individual methods are analyzed. For the measurement of sorption and photocatalytic properties, an experimental reactor for the continuous measurement of photocatalytic processes developed in the Laboratory of Nanoparticulate Matter of nanotechnology center was used. The advantage of the reactor is in-situ measurement, so there is no need to interfere with the system. The vacuum freeze-drying method was used to convert samples from a water dispersion to a powder form for better handling and preservation of a high specific surface area. The developing process of sorption material with possibility of photocatalytic regeneration consisted of several steps. First, photocatalytic materials with a high specific surface based on a porous silicate structure containing zinc and graphene were prepared and characterized. The structure was deposited on the fiber structure for better handling. The material exhibited a relatively high specific surface area of 410 m2/g and much better results in photocatalytic activity than the P25 standard. Next prepared material, modified with g-C3N4, exhibited the capability of photocatalytic regeneration. Since no sorbent standard with photocatalytic regeneration effect is commercially available, titanium dioxide was used for comparison. The nanocomposite exhibited higher sorption capacities, the specific surface and rate constants of the sorption process. The sorption surface was successfully regenerated by UV irradiation, but the following cycles significantly reduced sorption capacity of the sorbent. By omitting the lyophilization process, the loss of samples was. However, the possibility of controlling the amount of used sorbent was lost. The next step was to increase the sorption capacities and to improve the regeneration properties of the sample by adjusting the preparation methodology prepared nanocomposite exhibited a high specific surface and ability of repetitive photocatalytic regeneration. Two variants were prepared, namely silicate structure containing 10 wt.% g-C3N4 and 20 wt.% g-C3N4. The material was tested for sorption of methylene blue. Photocatalytic decomposition was performed by irradiating the saturated sample with a LED source of UV radiation and natural diffuse sunlight. The regeneration efficiency for both samples exceeded 84% after the third cycle of UV regeneration and 94% after the third regeneration cycle with natural sunlight. When using a LED source emitting in the visible spectrum, the results of photocatalysis and regeneration were unproducible.9360 - Centrum nanotechnologiívyhově

Preparation and characterization of composite core-shell nanoparticles by binary dispersion method

Import 23/07/2015Práce se zabývá problematikou přípravy kompozitních nanočástic core-shell novou metodou binární aerosolové disperze. V teoretické části jsou rozebrány základy teorie polovodičů, fotokatalytických procesů, přehled známých metod přípravy nanočástic a parametry, jenž mají vliv na fotokatalytickou účinnost polovodivých nanočástic. Dále je popsána metoda binární aerosolové disperze přípravy core-shell nanostruktur SiO2-ZnS, charakterizace připravených nanočástic metodami DLS, TEM a UV-VIS spektrální fotometrií a měření fotokatalytické účinnosti degradací methylenové modři.This work is about preparation of composite core-shell nanoparticles using new binary aerosol dispersion method. In theoretical part there are discussed basics of semiconductors, photocatalytic processes, summary of known methods of preparation of nanoparticles and influence of different parameters on photocatalytic efficiency of semiconductor nanoparticles. Further there is described binary aerosol dispersion method used for preparation of core-shell nanostructures SiO2-ZnS, characterization of prepared nanoparticles using DLS, TEM and UV-VIS spectral photometry methods and measurement of photocatalytic efficiency by degradation of methylen blue.9360 - Centrum nanotechnologiívelmi dobř

Synthesis of ZnS nanoparticles of required size by precipitation in aerosol microdroplets

Zinc sulphide (ZnS) nanoparticles were prepared by an aerosol method from zinc acetate and sodium sulphide (Na2S) aqueous solutions. Aqueous solution of zinc acetate was dispersed into the form of microdroplets, which were introduced by airflow to vigorously stirred aqueous solution of Na2S, which was in excess. Microdroplets served as microreactors, so the reaction took place only in limited volume. Particle size distribution was studied by transmission electron microscopy and by dynamic light scattering measurements. In this work, the equation that allows us to predict the final size distribution of ZnS nanoparticles using exact concentration of zinc acetate was derived and ZnS nanoparticles with predicted mean particle diameter around 50 and 70 nm were successfully synthetised.Web of Science35778177

Mathematical modelling of lamellar aggregation of dispersed globular nanoparticles nC(60) on the interface upon sublimation of water molecules from rapid frozen dispersion

The publication is focused on the problem of nanoparticle aggregation on the sublimation interface between vacuum and rapid frozen liquid dispersion. The main aims are simulation experiments of mathematical modelling of these processes. During lyophilization of rapid frozen liquid dispersion of nanoparticles, a self-organization of nanoparticles occurs. The resulting structure depends on setting the process parameters. According to the current knowledge, they include temperature, vacuum depth, and nanoparticle fraction in the dispersion liquid. On the free sublimation interface, a streamlined flow of dispersion liquid molecules, also referred to as sublimation wind, flows into the vacuum. Lamellar nanoparticle aggregates are formed on the interface surface in this mode, which are gradually torn by the pressure of the sublimation wind. Aggregated materials with very high specific surface area may be formed by these processes. Mathematical modelling of nanoparticle dynamics on two-dimensional sublimation layer is employed to deepen the understanding of basic mechanisms of these aggregation processes. The simulation results are in good agreement with the experimental results of lamellar nanostructure aggregation of bonded globular nanoparticles nC(60). Further refinements based on the simulation experiments will allow active control of the process and quality of aggregated nanostructures.Web of Science1952677267

Experimentally verified physical model of ferromagnetic microparticles separation in magnetic gradient inside a set of steel spheres

In this work, we describe the model of magnetic Fe2O3 submicroparticles separation during transit of their water dispersion through separation pipe based on matrix of closely organized steel spheres. The fundamental idea originates from detailed field analysis of gradient magnetic field in spheres contacts ambient generated by external magnetic field and its influence on flowing submicroparticles. During the model derivation, the fundamental physical principles have been applied to minimise the influence of the phenomenological members. The determined result formula related to the separation model determines exit dispersion particles concentration and equivalent form of device efficiency. In its fundamental shape, this formula is the function of nine independent physical parameters. In the frame of its experimental verification, most of these parameters have been fixed. The experimental data have been correlated with our model prediction, where only the following three independent variables have been implemented: separation tube length, particles size, and external magnetic field intensity. The theory and experiment comparison have shown that the coefficient of determination R-2 is over 0.997. At the same time, the described theoretical model specifies the approach for optimal parameters selection to achieve the requested separation efficiency in concrete conditions.Web of Science239art. no. 11646

Preparation of sorbent with a high active sorption surface based on blast furnace slag for phosphate removal from wastewater

A new method has been presented, which leads to a significant improvement of the adsorption ability of blast furnace slag (BFS). An ultra-high pressure water jet mill cavitation disintegrator and a controlled vacuum freeze dryer were used to disintegrate amorphous BFS. Specific surface areas of both BFS and disintegrated slag (BFS-D) were measured using the SBET method. BFS-D was obtained with an average particle size of 198 nm and with 27-times bigger free specific surface area than that of original BFS. The BFS-D was tested as an adsorbent of phosphate from aqueous solutions. Adsorption data were analysed using the Freundlich and Langmuir adsorption isotherms. The BFS-D after phosphate adsorption was characterized using FTIR. The theoretical adsorption capacity of the BFS-D was 30.49 mg P/g, which represents an increase by 126.7% compared to the original BFS. Surface precipitation of hydroxyapatite was dominant retention mechanism.Web of Science43116816