Role of silver ions in Na2O-CaF2-P2O5 host glass and its corresponding glass-ceramic: Searching for antibacterial behaviour-supplemented by spectral, optical, FTIR and SEM investigations

Abstract

Glasses based on the base host Na2O-CaF2-P2O5 system with increasing Ag2O as additives or loading (0.2 to 1 wt%) were prepared by melting-annealing technique. Multiple characterizations of the prepared glasses were carried out. Heat- treatment of the glasses was done through a two-step protocol to convert them to their corresponding glass-ceramics derivatives. The state of silver ions was analyzed by additional optical and FTIR spectral beside SEM measurements. Antibacterial behavior of the Ag2+ ions in the studied glasses and their glass-ceramic derivatives was conducted by their response towards two G+ve strains (Staphylococcus aureus, Bacillus cereus), one G-ve bacterial strain (Escherichia coli), one yeast (Candida albicans) and one fungi (Aspergillus niger). Optical spectra show distinct UV absorption in the undoped glass spectrum and extend to near visible with increasing Ag2O content. This distinct UV absorption is assumed to originate from unavoidable trace iron (Fe3+) impurities while the peak at 420 nm is related to nanocrystalline (Ag0)n . FTIR spectra show vibrational spectra within the mid region 400-1650 cm-1which are characteristic for phosphate (PO4) groups with some suggested (PO3F) groups. The dopant silver ions show no distinct effect on the FTIR spectra. After immersion in phosphate solution FTIR spectra of the glass-ceramic reveal the formation of hydroxyapatite layer. X-ray diffraction results indicate the formation of crystalline phosphate phases for the undoped glass-ceramic. Two silver crystalline phases are identified after addition of Ag2+ ions. SEM images confirm the formation of apatite layer with different additions of silver ion. The antibacterial analysis also indicate the promising effect of the glass-ceramics than their parent glass in the bioactivity applications.