Plasmonic-Multichromatic Sensor for Gallic Acid Assay Utilizing Ag-Coated Au Nanobipyramids

Gallic acid (GA) is known for its valuable properties as an antioxidant, anti-cancer, and anti-mutagenic compound, making its detection in foods and drugs of paramount importance. In this research, we introduce a novel multichromatic sensor for GA detection, which employs the controlled growth of silver nanoparticles (AgNPs) on the surface of gold nanobipyramids (AuNBPs). The sensor exploits GA's capability to reduce AgNO₃, resulting in the growth of AgNPs and a subsequent blue shift of localized surface plasmon resonance (LSPR) as large as 195 nm. This unique multicolor response ranges from light gray to green, blue–violet, and pink, allowing for distinctive visual identification of GA concentrations. The sensor's performance demonstrates a wide dynamic range of 0–175 μM, and a detection limit (LOD) as low as 0.139 μM. Notably, the applicability of this multichromic plasmonic probe was successfully tested for GA assay in both Black and Green tea, showcasing highly satisfactory recovery efficiencies and affirming its potential for food quality control applications. The presented multichromatic sensor offers a promising approach for rapid and sensitive GA detection in various food and pharmaceutical products, enhancing the monitoring and assessment of GA content for improved product quality and safety.