Ag3PO4 tartalmú bioaktív üveg kompozitok előállítása, jellemzése és antibakteriális hatásának a vizsgálata: Synthesis, characterization, and antibacterial behavior analysis of the Ag3PO4 containing bioactive glass

Based on the low stability of the Ag nanoparticles and the high biocompatibility of phosphate-ion, this work deals with a combination of the above-mentioned two ions (Ag3PO4), and their application in biological systems. The precipitation synthesis method was used for Ag3PO4 synthesis. The microcrystals were analyzed by using scanning electron microscopy; X-ray diffractometry; infrared spectroscopy; and diffuse reflectance spectroscopy. The sol-gel method was used for the synthesis of bioactive glass, where the silver-phosphate was added in 3 different proportions (0; 0.1; 0.2; 0.4 mol%). Afterward, as-prepared samples were characterized by the above-mentioned methods and X-ray photoelectron spectroscopy. Antibacterial behavior of the samples was analyzed by using two different bacterial strains, where the composite, with 0.4% of Ag3PO4 resulted in the highest antibacterial character. Kivonat Az ezüst nanorészecskék gyenge stabilitását és a foszfát-ion erős biokompatibilitását alapul véve célunk volt ezen két ion együttes alkalmazása (Ag3PO4) és azok biológiai közegben való felhasználása. Az ezüst-foszfátok előállításakor csapadékképző reakciót alkalmaztunk. A mikrokristályokat pásztázó elektronmikroszkóp, röntgendiffraktométer, infravörös spektrométer és diffúz reflexiós spektrofotométer segítségével jellemeztünk. Az ezüst-foszfátot 3 különböző mennyiségben (0; 0,1; 0,2; 0,4 mol%) adagoltuk a bioaktív üveg rendszerébe, szol-gél módszert alkalmazva. Majd a fent említett műszerek segítségével és röntgen fotoelektron spektroszkóppal vizsgáltuk a szerkezeti, optikai és morfológiai változásokat. A minták antibakteriális hatását két különböző baktériumtörzsön vizsgáltuk, ahol azt vettük észre, hogy a 0,4% Ag3PO4-t tartalmazó minta rendelkezett a legmagasabb antibakteriális hatással.&nbsp

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

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

Tungsten Oxide Morphology-Dependent Au/TiO₂/WO₃ Heterostructures with Applications in Heterogenous Photocatalysis and Surface-Enhanced Raman Spectroscopy

Developing highly efficient Au/TiO2/WO3 heterostructures with applications in heterogeneous photocatalysis (photocatalytic degradation) and surface-enhanced Raman spectroscopy (dye detection) is currently of paramount significance. Au/TiO2/WO3 heterostructures were obtained via heat or time-assisted synthesis routes developed by slightly modifying the Turkevich–Frens synthesis methods and were investigated by TEM, SEM, XRD, Raman spectroscopy, XPS, photoluminescence, and UV–vis DRS techniques. Structural features, such as WO3 crystalline phases, TiO2 surface defects, as well as the WO3 (220) to TiO2-A (101) ratio, were the key parameters needed to obtain heterostructures with enhanced photocatalytic activity for removing oxalic acid, phenol, methyl orange, and aspirin. Photodegradation efficiencies of 95.9 and 96.9% for oxalic acid; above 96% (except one composite) for phenol; 90.1 and 97.9% for methyl orange; and 81.6 and 82.1% for aspirin were obtained. By employing the SERS technique, the detection limit of crystal violet dye, depending on the heterostructure, was found to be between 10−7–10−8 M. The most promising composite was Au/TiO2/WO3-HW-TA it yielded conversion rates of 82.1, 95.9 and 96.8% for aspirin, oxalic acid, and phenol, respectively, and its detection limit for crystal violet was 10−8 M. Au/TiO2/WO3-NWH-HA achieved 90.1, 96.6 and 99.0% degradation efficiency for methyl orange, oxalic acid, and phenol, respectively, whereas its limit of detection was 10−7 M. The Au/TiO2/WO3 heterojunctions exhibited excellent stability as SERS substrates, yielding strong-intensity Raman signals of the pollutant molecules even after a long period of time

Insights into the Stability of Graphene Oxide Aqueous Dispersions

Understanding graphene oxide’s stability (or lack thereof) in liquid solvents is critical for fine-tuning the material’s characteristics and its potential involvement in future applications. In this work, through the use of structural and surface investigations, the alteration of the structural and edge-surface properties of 2D graphene oxide nanosheets was monitored over a period of eight weeks by involving DLS, zeta potential, XRD, XPS, Raman and FT-IR spectroscopy techniques. The samples were synthesized as an aqueous suspension by an original modified Marcano-Tour method centred on the sono-chemical exfoliation of graphite. Based on the acquired experimental results and the available literature, a phenomenological explanation of the two underlying mechanisms responsible for the meta-stability of graphene oxide aqueous dispersions is proposed. It is based on the cleavage of the carbon bonds in the first 3–4 weeks, while the bonding of oxygen functional groups on the carbon lattice occurs, and the transformation of epoxide and hydroxyl groups into adsorbed water molecules in a process driven by the availability of hydrogen in graphene oxide nanosheets