Abstract
In the present work, composite materials very promising for biomedical and pharma-ceutical applications were investigated. They are composed of silver nanoparticles (Ag NPs) in a matrix constituted of calcium carbonate functionalized with hydroxyapatite (HA-FCC). The composites were obtained by different synthesis methods, starting from a mixture of the silver acetate with HA-FCC (using adsorption or mixing in wet conditions methods) and then treating them by exposure to visible light or calcination to promote the silver reduction; a synthetic procedure based on ultrasound-assisted reduction with NaBH4 or citrate was also carried out. The characterization by X-ray photoelectron spectroscopy and reflected electron energy loss spectroscopy analysis also involved the reference sample of HA-FCC matrix. Then the morphology of the Ag NPs and the crystalline structure of HA-FCC were studied by transmission electron microscopy and X-ray diffraction, respectively. To assess the effectiveness of the different methods on silver reduction, the Auger parameters α’ were calculated and compared. The use of this methodology based on the Auger parameter is neither trivial nor ordinary. We demonstrate its validity since the different values of this parameter allow to identify the oxidation state of silver and consequently to evaluate the formation yield of metallic Ag NPs in the HA-FCC matrix and the effectiveness of the different reduction methods used.
Highlights
Afterwards, the sample 1 was either irradiated with a Hg lamp equipped with a long pass filter to enable exposure to 430–800 nm radiation for 120 min or it was calcined at 300 ◦ C to produce the sample 5; A dispersion of HA-functionalized calcium carbonate (FCC) (1 g) was mixed with an aqueous almost saturated solution of silver acetate, it was heated at 37 ◦ C until dryness and irradiated as for sample 2 in order to obtain the sample 4; For the synthesis of samples 6–9, a solution of reducing agent (NaBH4, or trisodium citrate) was dropped, under high power ultrasound irradiation for 45 min at 50%
CaCO3 and HA phases in the HA-FCC composite are clearly detected, whereas the treatment with silver acetate induces the formation of a new phase identified as Ag3 PO4 by comparison with the reference spectra of cubic silver phosphate (PDF#01-084-0192)
The composites of Ag nanoparticles dispersed in hydroxyapatite HA-FCC were synthesized by using different methods and characterized by XRD, Transmission electron microscopy (TEM), reflected electron energy loss spectroscopy (REELS), and X-ray photoemission spectroscopy (XPS)
Summary
Ag nanoparticles have attracted the attention of researchers for their numerous biological activities [12,13,14,15]. For their characterization, the analytical technique of X-ray photoemission spectroscopy (XPS) results to be a tool with peculiar properties capable to provide information on surface chemical composition. By using the analytical technique of X-ray photoemission spectroscopy, it is possible to obtain the information on the surface chemical composition, and to identify
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