Red emissive Ag2Se quantum dots (QDs) with room-temperature synthesis of both orthorhombic and superionic cubic phases via stirring approach

In this research Ag2Se quantum dots (QDs) were synthesized with just a stirring room-temperature approach, using AgNO3 and Na2SeO3 as precursors and thioglycolic acid (TGA) as capping agent molecule. Synthesized QDs were characterized by means of XRD, FTIR, FESEM, EDS, HRTEM, UV-Vis and PL analyses. Synthesized QDs were in orthorhombic phase of Ag2Se (β-Ag2Se) with a uniform size distribution histogram between 1.8 and 2.5 nm. Synthesized QDs indicated two sharp exciton absorption peaks at 440 and 607 nm at room temperature and a narrow red emission between 600 and 800 nm with a peak at about 673 nm and FWHM of about 57 nm. The quantum yield was obtained about 4.48% which is highest among reported values. It was found that orthorhombic (β-Ag2Se) and superionic cubic (α-Ag2Se) phases can simply be formed at room temperature only by changing the sequence of addition of TGA capping agent. The cubic phase co-exists with orthorhombic phase was identified by XRD and it revealed also exciton absorption bands at room temperature due to strong quantum confinement effects.