The effect of the addition of gallium on the structure of zinc borate glass with controlled gallium ion release

Gallium ion released from bioactive glasses can perform therapeutic functions depending on its concentration. In this study, zinc borate based glasses with increasing gallium content (0, 2.5, 5,10, and 15 wt.% Ga) were synthesized and their structural properties and gallium ion release capabilities were investigated in order to understand how the substitution of gallium for boron affects the glass network. X-ray diffraction verified the amorphous state of the synthesized glasses. Thermal and spectroscopic analyses recorded a steady decline in both glass transition and crystallization temperatures of the glasses alongside small shifts in the position of borate triangles' peaks, indicating short-range order rearrangements, and a rise in the number of pentaborate and loose BO3 units by the addition of gallium. B-11 Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) analysis showed incremental addition of gallium reduces the BO4/BO3 ratio which indicates an increase in the non-bridging oxygens in the glasses with higher gallium content, and P-31 MAS NMR analysis revealed the presence of orthophosphate units with one and two bridging oxygens and that the introduction of gallium overall lowers the fraction of units with two bridging oxygens. The released gallium ion was considerably more in glasses with higher gallium content. (C) 2015 Elsevier Ltd. All rights reserved.