Fluorescein (FL) is a versatile organic dye known for its bright green fluorescence under blue or ultraviolet light. Its unique properties make it a valuable tool in various scientific fields, especially bioimaging and forensics. By combining fluorescein with nanomaterials, researchers can significantly modify its optical characteristics (photostability and photocatalytic degradation). This study investigates the effects of gold, silver, and gold-silver bimetallic nanoparticles on fluorescein. These interactions could alter fluorescence emission, enhance light absorption, or induce quenching. The synthesis of fluorescein was achieved using phthalic anhydride, resorcinol, and sulfuric acid as catalyzer. Fluorescein characterization was conducted using Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), UV-Vis spectroscopy, and fluorescence spectroscopy. Gold (Au), silver (Ag), and bimetallic (Au-Ag) nanoparticles (Np) were synthesized using traditional chemical methods involving sodium citrate (Na₃C₆H₅O₇), ascorbic acid (C₆H₈O₆), and the salts (AgNO₃, HAuCl₄ and the combination of both for the bimetallic). Nanoparticle characterization was performed using Dynamic Light Scattering (DLS), Localized Surface-Plasmon Resonance (LSPR) absorption and Scanning Electron Microscopy (SEM) analysis. To study the fluorescein-nanoparticle interaction, fluorescein samples at pH 5, 7, and 9 were subjected to sunlight for 3, 6, and 9 hours. Absorption properties were evaluated using UV-Vis Spectroscopy. Results showed that degradation percentages (%De) at pH 5 were 62.72% for the FL control sample and 54.12% for the AgNp-FL system. At pH 7, the FL control was 54.90%, while the Au-AgNp-FL system decreased degradation to 39.63%. Finally, at pH 9, the FL control was 59.35%, and the Au-AgNp-FL system was 48.82%. All three nanoparticles stabilized fluorescein emission at 522 nm, but Au nanoparticles demonstrated decreased stability after two hours. Further studies will be conducted to compare the behavior of bimetallic nanoparticles synthesized biologically to the conventional chemical method.

Bryan De Jesús Medina

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