Rapid wet chemical synthesis of bioactive glass with high yield by probe sonication

Bioactive glasses (BGs) are inorganic biomaterials which possess favourable properties for bone repair and regeneration. The biological properties of the BGs depend on their physical features. This manuscript describes a simple methodology for rapid synthesis of BG nanoparticles (NPs) with tailored physical properties using ultrasonic disruption produced by an ultrasonic probe. The ultrasonic probe generates stable and transient cavitation which increases the mass transfer and accelerates the chemical reaction. This approach is relatively green as it evades the use of the drastic acidic conditions required for hydrolysis. The prepared BG NPs were characterized by Fourier transform infra-red (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), particle size analysis (PSA), nitrogen adsorption/desorption and BET surface area analysis, X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectrometry (ICP-OES), and in situ high temperature synchrotron XRD. The effects of ultrasonic irradiation time, and amplitude on the surface properties were investigated and the results confirmed that both parameters, especially amplitude, have significant effects on the physical properties of the prepared BG NPs. The XPS results showed that both, amplitude and time have a pronounced effect on the bridging and non-bridging oxygen atoms bonded to the Si centre in the BG samples, which play an important role in the bioactivity of the BG NPs. The in situ high temperature XRD patterns indicated a gradual phase transformation for the BG samples synthesized at different ultrasonic irradiation times and amplitudes. The TEM images showed that uniform nano-sized BG particles were obtained at 50% amplitude in only 10 minutes. A bimodal particle size distribution was observed with an increasing reaction time, up to 30 minutes, due to an increase in the formation of vortices at the interface where nucleation starts. All the prepared samples exhibited a glassy structure with the composition 70SiO₂ : 25CaO : 5P₂O₅ and were highly bioactive. The proposed method would give a quick route for the synthesis of bioactive glasses and other ceramics with controlled physical properties.