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

Abstract

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.