Synthesis and characterization of Ag-loaded hematite nanocomposites

Hematite (α-Fe2O3) nanoparticles have been synthesized by thermal decomposition of iron(III)acetylacetonate precursor. The structure and morphology of the resulting powder were investigated by X-ray powder diffraction (XRPD), Fourier transformation IR (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). Hematite-loading with silver was conducted using the reduction of silver nitrate by ascorbic acid realized by three different synthetic procedures – simple reduction process, ultrasonically supported reduction, and reduction after pre-treatment of hematite in Lugol's iodine. All synthesized hematite/silver samples were characterized withSEM, supported by EDS maps. Silver content was determined by Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES). The development of Ag-doped hematite nanocomposites, hetero-structures containing Ag and magnetic iron oxide,is indispensable in orderto take advantage of Ag containing nanocomposites in the field of biomedicine

The influence of the addition of brushite on the mechanical properties of geopolymer binder

The growing need to protect the environment and reuse abandoned raw materials is increasingly used in the construction industry to make in addition to cementitious materials and geopolymer materials. Geopolymers are alkali-activated materials, in which the starting material is mainly some residual material such as: clay, fly ash, slag or red sludge [1,2]. There is growing need to create new binders which can replace portland cement and geopolymer materials are increasingly being used for this purpose. For geopolymerization reaction process high concentration basic solution with alkaline activators are adding and the process itself leads to modifications of the structures of the starting raw materials [1]. Due to growing needs to improve mechanical properties of geopolymer binders, different calcium sources can be added and one of them is brushite-dicalcium phosphate dihydrate [3]. The aim of this paper is synthesis and characterization of Brushite-metakaolin-based geopolymer material samples, with different percentages of pure Brushite material added. Brushite, was obtained by solution precipitation reaction from appropriate acetate salts solution, by green chemistry process. Raw kaolinite clay from the Rudovci deposit (Serbia) was used as Al and Si source for geopolymer binder production. Kaolinite was thermally treated at 750°C for three hours, to produce metakaolin and remove residual organic matter. In order to investigate the influence of calcium phosphate compound on mechanical and microstructural properties geopolymer material samples were synthesized using metakaolin mixed with activator solution prepared from sodium silicate and sodium hydroxide (6M) in relation 1,6 with addition of 2%, 4%, 6%, 8%, 10%, of pure brushite. Phase, structural, and microstructural characterisation were preformed in a mening of XRPD and SEM analysis. Difference between diffractograms of starting materials and Brushite-metakolin analogues indicates that geopolymerization process was successful in all samples. DRIFT technique was used to obtain characteristic vibrations of functional groups in obtained materials. The compressive strenghts of geopolymer binders containing brushite were in a range of 15-55 Mpa. The the highest hardness was achieved by a geopolymer with 10% of brushite

Effect of Sintering Temperature and Calcium amount on Compressive Strength of Brushite-Metakaolin Polymer Materials

The effect of Ca2+ amount and sintering temperature on mechanical properties of geopolymer-brushite (GPB) binders was investigated. Brushite and raw abandoned kaolinite clay thermally transformed into metakaolin were used for GPB synthesis. The complete phase and structural analyses were performed by X-ray powder diffraction, and Fourier transforms infrared spectroscopy (FT-IR). The pore-filling effect as a consequence of Ca2+ ions incorporation into the hybrid geopolymer networks improved the compressive strength. On the other hand, the chosen biscuit sintering at 800 and 900oC caused the phase transformation of brushite into calcium pyrophosphate, which negatively affected the compressive strength of such materials. The obtained results indicate that the usage of relatively high sintering temperatures is not always the necessary step for producing geopolymer-based types of cement with prominent mechanical properties

Mechanical activation and silver supplementation as determinants of the antibacterial activity of titanium dioxide nanoparticles

Metals and metal oxides have subpar antibacterial activities compared to those of small-molecule antibiotics, yet there are hopes that with proper compositional and structural adjustments this gap might be bridged. In this study, titanium dioxide (TiO2) nanoparticles were mechanically activated and combined with particulate silver through simple reduction process elicited by UV irradiation and assisted with the ultrasound. The resulting powders in various combinations (Ag vs. no Ag, activated vs. non-activated) were characterized using a range of experimental techniques and assessed for their antibacterial activities. The preparation procedure presented in this work prevails over the disadvantages of many chemical routes, most critically by avoiding the use of toxic substances. The mechanical activation did not reduce the particle size or crystallinity of TiO2 nor did it consistently alter the bandgap, yet it enabled the doubling of the amount of silver incorporable into the material. Further, while both mechanical activation and the addition of silver in the amount not exceeding 0.5 wt% produced barely detectable structural changes in the material, they both augmented its antibacterial activity. The precursor TiO2 powder produced no inhibition zone against any of the four bacterial species tested, while the mechanical activation of TiO2 led to the formation of distinct inhibition zones against each of the four bacterial species tested. The addition of silver to activated TiO2 further widened the inhibition zones and it also imparted the antibacterial activity to non-activated TiO2. The boost in the antibacterial activity achieved by the short mechanical activation was of a similar magnitude as the boost obtained after the addition of silver. The antibacterial activity was not different for different species when no silver was added to the system. However, with the addition of silver, species selectivity was obtained, as the composites were more effective against the two Gram-negative species (Escherichia coli and Klebsiella pneumoniae) than against the two Gram-positive ones (Staphylococcus aureus and Bacillus subtilis). The antibacterial activity increased with the addition of silver in the broth assay, but it was mediocre compared to that detected in the agar assay, attesting to the poor dispersability of the powders and their best performance when the bacterial cells migrate to the composite surface than vice versa. The findings of this study give hope that with appropriate microstructural or compositional alterations, the antibacterial activity of metal oxide powders and inorganic materials in general can be made comparable to that of small-molecule antibiotics

Sinteza, karakterizacija i antimikrobna svojstva gvožđe-oksid/srebro nanokompozita

Rezistencija bakterija na antibiotike predstavlja jedan od glavnih izazova biomedicinskih nauka, a neorganski materijali mogu biti efikasna alternativa za lečenje infektivnih bolesti izazvanih multirezistentnim sojevima. U okviru ovog rada urađena je sinteza i karakterizacija polifaznih nanokompozita na bazi gvožđe-oksida (Fe2O3) i srebra (Ag) u cilju ispitivanja antimikrobnih svojstava. Gvožđe-oksid je sintetisan termalnom dekompozicijom gvožđe(III)-acetilacetonata, dok je srebro deponovano na površini oksidnih čestica redukcijom rastvora srebro-nitrata askorbinskom kiselinom na tri različita načina. Detaljno je prikazan uticaj uslova sinteze na strukturu i morfologiju dobijenih nanokompozita. Utvrđeno je da količina srebra nije odlučujući faktor za antimikrobnu aktivnost, već njegova raspodela i dostupnost na površini oksida

Sinteza, karakterizacija i antimikrobna svojstva titanijum-dioksid/srebro nanomaterijala

Razvoj novih materijala koji služe u borbi protiv multirezistentnih sojeva je od velikog značaja. Titanijum-dioksid je u ove svrhe izučavan kao netoksični antimikrobni agens koji tu funkciju ispoljava zahvaljujući svojoj fotokatalitičkoj aktivnosti. Kako bi se unapredila svojstva ovog materijala, napravljen je kompozitni materijal sa srebrom. Dobijeni materijal pokazao je izrazitiju fotokatalitičku aktivnost u uslovima niske osvetljenosti. U ovom radu predstavljena je sinteza titanijum-dioksid/srebro nanokompozita dobijenog metodom ultrazvukom potpomognute fotoredukcije. Detaljno je opisana morfologija proizvoda, kao i ispitana antimikrobna svojsta

Silver distribution and binding mode as key determinants of the antimicrobial performance of iron oxide/silver nanocomposites

The emerging threat of bacterial resistance to antibiotics prompts the urgent search for biomaterials for the treatment of infectious disease. Here we report on the synthesis and characterization of a multiphasic nanocomposite comprising magnetic iron oxide and silver nanoparticles. The method of synthesis involved the combustion of a metalorganic complex and reduction of the silver ions that were exchanged and/or adsorbed on the surface of iron oxide. Different physical and chemical treatments coupled to the reduction process, including ultrasound and Lugol's iodine solution, respectively, homogenized the distribution of the silver nanoparticles on the iron oxide phase. Remarkably, using ascorbic acid as a reductant enhanced the magnetic properties of the material as a result of the reduction of the magnetic matrix alongside the silver cations. The treatment with ultrasound detached large amounts of silver from the iron oxide phase and resulted in the lowest amount of silver incorporated in the nanocomposite. Despite that, this treatment led to the highest antibacterial activity against both Gram-positive and Gram-negative strains, indicating that the homogeneity of the distribution of silver on the iron oxide matrix is a more important determinant of the antibacterial performance than the amount of silver incorporated in the material. At the same time, the treatment with Lugol's iodine equally increased the distribution homogeneity, but induced excessive ion exchange and crystal lattice substitutions, thereby adversely affecting the antibacterial performance. This has indicated that the mode of binding silver to iron oxide can compensate for the positive effects of homogeneous distribution with respect to the antibacterial performance