Effect of Aluminum Salt Precursor on the Crystalline Structure of Alumina Nanoparticles (Al2O3) Synthesized by Green Chemistry Using Cymbopogon citratus Extract

Abstract

Alumina nanoparticles have broad applications in catalysis, electronics, and the construction sector, and are widely incorporated as additives in coating formulations to enhance mechanical durability and functional performance. This work focuses on the green synthesis of aluminum oxide (Al2O3) nanoparticles using lemongrass (Cymbopogon citratus) extract. Aluminum nitrate [Al(NO3)3] and aluminum chloride (AlCl3) were used with extract. The reaction was carried out at 70 °C for 1 h at 250 rpm and then thermal treatments at 700 °C and 900 °C were applied. The results showed that nanoparticles synthesized from the AlCl3 and calcined at 700 °C exhibited a smaller particle size (36 ± 14 nm) as compared with those synthesized from the [Al(NO3)3] and calcined at 700 °C (49 ± 25 nm). Despite both precursors yielding nanoparticles, the peaks related to the γ-Al2O3 crystal phase were observed in the AlCl3 at 700 °C calcination. Conversely, the nanoparticles synthesized from the [Al(NO3)3] required a high temperature treatment at 900 °C to display this stable crystal phase. This study reports an easy and cost-effective green chemistry route to obtain γ-Al2O3 nanoparticles, highlighting the importance of the selection of precursors as a critical step to achieve a sustainable and low-energy process, suggesting the potential applications in paints with multifunctional properties.