In the present study, the ratio of reducing to oxidizing (F/O) elements as an indicator for maximum oxygen interference during the solution combustion synthesis (SCS) process of ZnO particles was determined using simple mathematical calculations. The obtained result was called special point (S.P). To interpret the role of S.P in the SCS reactions, ZnO particles were synthesized in the presence of citric acid, hexamine, hydrazine, and urea with various F/O values (0.75, 1, 1.25). The correlations between the S.P, physicochemical properties of the synthesized ZnO powders, and density functional theory (DFT) predictions were investigated. X-ray diffraction results, band-gap values, oxygen vacancy data, DFT results, and S.P points demonstrated the direct relation of these parameters. According to the S.P idea, it can be affirmed that the structural defects, particle size, optical band-gap (Eg = 3.06), the color of the products, the magnetic properties (0.2 emu/g), and the antibacterial inhibitory (15.625 µg/mL) of the synthesized particles were controlled via the interference of O2 during the synthesis process. In fact, the S.P investigation was suggested that the reaction rate of the combustion synthesis process could regulate the properties of ZnO particles.

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