3. Results and discussion
Olibanum gum is sparingly soluble in water, the solubility of olibanum gum can be increased by converting to sodium salt of olibanum gum by the addition of specific amount of sodium hydroxide. This sodium salt of olibanum gum can act as reducing agent as well as a stabilizing agent for the formation of AuNPs which has been reported in the present work for the first time. In our synthetic procedure, this olibanum gum has a dual role as a reducing agent and capping agent. The major advantage of using microwave is the fast synthesis with controlled size of AuNPs. Furthermore, olibanum gum has preferred as it is eco-friendly polysaccharide, easily available, and low cost that motivated the researchers in the preparation
The absorption spectra still showed one absorption peak located at 530 nm due to the SPR of the AuNPs and no other peak was detected in the range between 540-700 nm. This result clearly indicates that no aggregation occurs in this reactive system and the nanoparticles are well dispersed [42]. The efficacy of formation of AuNPs increased with increase in the concentration of HAuCl4, reflecting the formation of more and more AuNPs. The prepared NPs are not bigger in size due to the capping effect of olibanum gum. Therefore, it is possible that a huge amount of AuNPs with small particle size can be achieved using olibanum gum as a capping and reducing
This feature was studied by monitoring the SPR under different pH and electrolytic conditions over a reasonable period of time. The blue shift normally observed in UV-visible spectra is an indication of an agglomeration of nanoparticles or increase in the size of the particle or both. The synthesized AuNPs did not show any shift in the SPR peak and the peak intensity was decreased due to the dilution with varying concentrations (1–5M) of sodium chloride (NaCl) (Figure 7A) and varying the pH of the solution between 2–9 did not alter the size of NPs and no major agglomeration was observed (Figure 7B). The stability of as synthesized AuNPs were stable up to three months at room temperature (Figure 7C) due to the protection of olibanum gum on the nanoparticles