Role of Synthesis Parameters in Optoelectronic and Antibacterial Properties of Microcrystalline β-Ga₂O₃ and GaO(OH)


β-Ga2O3, a wide band gap semiconductor, has been attracting interest recently due to its applications in high-power/high frequency telecommunications, next generation solar cells, sensors, etc. Nano- and microcrystalline β-Ga2O3 is gaining significance for its potential us-es, including antimicrobial. However, the fundamental nature of the antibacterial action by Ga2O3 remains not well established. In particular, the role of surface phenomena in this re-gard is not understood. Moreover, while Ga2O3 is known for its antibacterial efficacy, there is almost no research reported on the antibacterial properties of GaO(OH), the synthesis pre-cursor of Ga2O3. Thus, there is a need for a simple synthesis protocol and a thorough charac-terization of these materials. We synthesized β-Ga2O3 microcrystals with controlled mor-phologies via a hydrothermal method. Deionized water, ammonium hydroxide, and gallium nitrate salt were mixed with pH levels ranging from 5 to 10 to create the samples. The GaO(OH) samples were then produced by annealing, followed by a high-temperature calci-nation, leading to β-Ga2O3, the final product. Analysis of the optoelectronic properties (elec-tronic structure and charge dynamics) of the obtained materials was performed using pho-toluminescence spectroscopy as well as time- and energy-dependent surface photovoltage before and after a remote plasma treatment (RPT). The samples were also characterized by electron microscopy, Fourier-transform infrared (FTIR) and X-ray diffraction spectroscopies. The biological assays of our samples in a DMSO broth were cultured with Staphylococcus au-reus and Escherichia coli and then light absorption was used to determine the minimum in-hibition concentrations. One of our goals was to addresses the impact of the precursors’ pH on the properties of β-Ga2O3 and GaO(OH). Systematic analysis revealed that the pH control-lably affected the morphology of the particles and strongly impacted the crystal lattice de-fects. Our results agree with theoretical calculations for sub-bandgap states and explicate the related surface charge dynamics. We also demonstrate a successful modification of the surface properties following RPT. The correlation between the surface chemistry and pH was confirmed by FTIR experiments. Antibacterial assays established an increased inhibition of the E. coli bacteria growth at higher precursor pH, while no conclusive correlation was ob-served in similar assays of S. aureus.

2nd International Conference on Advanced Materials for Bio-Related Applications