Background: Chalcogenide nanoparticles (NPs), such as silver selenide NPs (Ag2Se NPs), are used as quantum dots in pharmaceutical formulations for the detection of cancer cells, as well as in solar cells, sensors, and electrical, optical, and magnetic instruments. Objectives: The physical-chemical production of metal NPs is expensive and difficult and pollutes the environment due to the use of dangerous chemicals and by-products. Hence, green chemistry-based processes must be developed as a reliable alternative. This study investigated indigenous aquatic fungal isolates for Ag2Se NP synthesis. Methods: Visual examination, UV-Vis spectroscopy, scanning electron microscopy (SEM), dynamic light scattering (DLS) analysis, and energy-dispersive X-ray spectroscopy (EDX) tests confirmed the synthesis of Ag2Se NPs. Based on the characteristics of the colony, the microscopic features, and the polymerase chain reaction (PCR) amplification of the ITS1-5.8S-ITS2-ITS4 areas, the selected fungal isolate’s identity was established. Results: The SEM analysis revealed that Cladosporium species ssf15 produced spherical Ag2Se NPs with an average diameter of 37.84 nm. The average size of NPs synthesized by the fungal isolate was determined to be 40.92 nm using the DLS analysis, and the polydispersity index (PDI) was determined to be 0.26. Based on the results, regular spherical Ag2Se NPs with correct dispersion distribution were produced using 2 mM AgNO3 and 1mM selenious acid (H2SeO3). Conclusions: The results of this research have the potential to contribute to the development of a biocompatible approach and innovative research methods for investigating the green synthesis of Ag2Se NPs using fungal isolates.
