Solvothermal synthesis of ZnO spheres: Tuning the structure and morphology from nano- to micro-meter range and its impact on their photocatalytic activity

Nano- and micro-sized ZnO spheres were fabricated via a simple solvothermal synthesis using two different precursors, while diethanolamine was used to control the morphology. The applied solvent composition, pre- cursor ratio and solvothermal treatment temperature were mathematically correlated with the diameter of spheres. The crystallite size could be easily controlled by adjusting the temperature, providing flexibility during synthesis. The photocatalytic activity and its dependence on the unique morphology were investigated via the decomposition of phenol model pollutant. It was revealed that the surface proprieties were more defining than the secondary particle size in this regard. A surprising synergic effect was observed between the ratio of exposed crystallographic planes of (100) and (002) and crystallite size upon the activity, while the size of the spheres shows little influence. The presented method enables the flexible design of ZnO photocatalysts with spherical morphology in a tunable size range

Utilization of Carbon Nanospheres in Photocatalyst Production: From Composites to Highly Active Hollow Structures

Titanium dioxide–carbon sphere (TiO2–CS) composites were constructed via using prefabricated carbon spheres as templates. By the removal of template from the TiO2–CS, TiO2 hollow structures (HS) were synthesized. The CS templates were prepared by the hydrothermal treatment of ordinary table sugar (sucrose). TiO2–HSs were obtained by removing CSs with calcination. Our own sensitized TiO2 was used for coating the CSs. The structure of the CSs, TiO2–CS composites, and TiO2–HSs were characterized by scanning electron microscopy (SEM), infrared spectroscopy (IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). The effect of various synthesis parameters (purification method of CSs, precursor quantity, and applied furnace) on the morphology was investigated. The photocatalytic activity was investigated by phenol model pollutant degradation under visible light irradiation (λ > 400 nm). It was established that the composite samples possess lower crystallinity and photocatalytic activity compared to TiO2 hollow structures. Based on XPS measurements, the carbon content on the surface of the TiO2–HS exerts an adverse effect on the photocatalytic performance. The synthesis parameters were optimized and the TiO2–HS specimen having the best absolute and surface normalized photocatalytic efficiency was identified. The superior properties were explained in terms of its unique morphology and surface properties. The stability of this TiO2–HS was investigated via XRD and SEM measurements after three consecutive phenol degradation tests, and it was found to be highly stable as it entirely retained its crystal phase composition, morphology and photocatalytic activity

Arany nanorészecskéket tartalmazó bioaktív üveg – biopolimér kompozítok előállítása, jellemzése és alkalmazhatósága: Synthesis, characterization and applicability of bioactive glass – biopolymer composites with gold nanoparticles

Considering that the median age of our population is increasing, bone disorders or skin regeneration problems are of significant concern. The bioactive glass-biopolymer composites are materials with real potential to be used in tissue engineering. It is well-known, that the bioactive glasses (BG) can lead the promotion of growth of granulation tissue. The gold nanoparticles (AuNPs; ~20 nm) can induced the acceleration of wound healing including tissue regeneration, connective tissue regeneration and angiogenesis. It was demonstrated that the AuNPs in the sol-gel derived glass structure retain their properties. Alginate-pullulan (Alg-Pll) composites have good bioactivity and in vivo qualities in terms of bone regeneration. The goal of this study was to obtain the functional composites for future tissue engineering applications using BG with AuNPs introduced in Alg-Pll composites. After structural and morphological characterization of the composites, in vitro and in vivo bioactivity and biocompatibility were evaluated. The obtained results suggest that the obtained composites are materials for future soft tissue and bone engineering applications.  Kivonat A várható élettartam növekedésével egyre növekszik azon betegek száma, amelyek ortopédiai vagy bőr rekonstrukcióra szorulnak. A bioaktív üveg-biopolimer kompozitok potenciálisan alkalmazható anyagok a szövettani sebészetben. Ismert dolog, hogy a bioaktív üvegek (BG) elősegítik a granulációs szövetek növekedését. Az arany nanorészecskék (AuNPs; ~20 nm) gyorsítják a sebgyógyulást beleértve angiogenézist, a szövetek és kötőszövet regenerálódását. Tudjuk, hogy a szól-gél módszerrel előállított üveg szerkezetben bevitt AuNPs képes megőrizni ezen tulajdonságait. Az alginát-pullulán (kompozitok) remek bioaktivitásuknak köszönhetően aktívan részt vesznek az in vivo csont regenerálódásban. A tanulmány célja, hogy olyan funkcionális kompozitokat hozzunk létre, amelyek alkalmazhatók a szövettani sebészetben. Ehhez az Alg-Pll kompozitokban AuNPs tartalmazó BG vittünk be, majd szerkezeti és morfológiai jellemzéseket végeztünk. Ezt követtően az in vitro és in vivo bioaktivitás, valamint biokompatibilitást vizsgáltuk. A kapott eredmények azt sugallják, hogy az előállított kompozitok megfelelnek a lágyrész- és csonttechnikai alkalmazás elvárásainak

Shape tailoring of AgBr microstructures: effect of the cations of different bromide sources and applied surfactants

Investigations regarding AgBr-based photocatalysts came to the center of attention due to their high photosensitivity. The present research focuses on the systematic investigation regarding the effect of different alkali metal cation radii and surfactants/capping agents applied during the synthesis of silver-halides. Their morpho-structural and optical properties were determined via X-ray diffractometry, diffuse reflectance spectroscopy, scanning electron microscopy, infrared spectroscopy, and contact angle measurements. The semiconductors' photocatalytic activities were investigated using methyl orange as the model contaminant under visible light irradiation. The correlation between the photocatalytic activity and the obtained optical and morpho-structural properties was analyzed using generalized linear models. Moreover, since the (photo)stability of Ag-based photoactive materials is a crucial issue, the stability of catalysts was also investigated after the degradation process. It was concluded that (i) the photoactivity of the samples could be fine-tuned using different precursors and surfactants, (ii) the as-obtained AgBr microcrystals were transformed into other Ag-containing composites during/after the degradation, and (iii) elemental bromide did not form during the degradation process. Thus, the proposed mechanisms in the literature (for the degradation of MO using AgBr) must be reconsidered