Sonochemical Synthesis of Gold Nanoparticles as A Digital Image-Based Colorimetric Probe for Aluminum Ion Detection

Eduwin Saputra (Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Bengkulu, Jl. Wr. Supratman Kandang Limun, Muara Bangka Hulu 38371, Bengkulu, Indonesia)
Sri Juari Santosa (2Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Bulaksumur, Caturtunggal, Sleman 55281, Yogyakarta, Indonesia)

Jurnal Kimia Riset
Vol. 11 No. 1 (2026): June

Gold nanoparticles functionalized with ethylenediaminetetraacetic acid (EDTA-AuNPs) were successfully synthesized using a sonochemical approach. The synthesis results show a characteristic red color with a SPR peak at 524 nm. The addition of Al³⁺ ions induces a color change in EDTA-AuNPs to blue with a new absorption peak at 700 nm, indicating nanoparticle aggregation. Transmission electron microscopy data confirmed that EDTA-AuNPs particles were dispersed and aggregated after reacting with Al³⁺. Particle size analysis (PSA) confirmed an increase in particle diameter from 27 nm to 161 nm after the addition of Al³⁺. The colorimetric sensor exhibited high selectivity toward Al³⁺ ions. The quantitative analysis was conducted using both UV-Visible spectrophotometry and colorimeter methods. The UV-Visible spectrophotometer method has a detection limit of 0.15 mM, while the colorimeter shows a sensitivity of 0.07 mM. The integration of digital image-based colorimeter methods enables the development of a portable, sensitive, low-cost, and simple platform for on-site detection of Al³⁺ ions.