UV Light as an Efficient Tool for Reducing Surface Defects of ZnSe-MSA Quantum Dots

Defects in ZnSe quantum dots are responsible for increasing the trap states, which can lead to the drastic reduction of their fluorescence output, being one of the major drawbacks of these materials. As surface atoms become more relevant in these nanoscale structures, energy traps due to surface vacancies, play a very definite role in the final emission quantum yield. In the present study, we report the use of photoactivation procedures to decrease surface defects of ZnSe QDs stabilized with mercaptosuccinic acid (MSA), in order to improve the radiative pathways. We applied the colloidal precipitation procedure in a hydrophilic medium and evaluated the role of Zn/Se molar ratios as well as the Zn2+ precursors (nitrate and chloride salts) on their optical properties. Best results (i.e. increment of 400% of the final fluorescence intensity) were obtained for nitrate precursor and a Zn/Se = 1.2 ratio. Thus, we suggest that the chloride ions may compete more efficiently than nitrate ions with MSA molecules decreasing the passivation capability of this molecule. The improvement in ZnSe QDs fluorescence can potentialize their use for biomedical applications.

Automated summary

Defects in ZnSe quantum dots increase trap states, leading to a drastic reduction in fluorescence output, a major drawback. Surface vacancies causing energy traps play a significant role in emission quantum yield. This study uses photoactivation procedures to decrease surface defects of ZnSe QDs and improve radiative pathways. The best results were obtained with a nitrate precursor and a Zn/Se ratio of 1.2, showing a 400% increase in fluorescence intensity. Potential applications in biomedicine can be enhanced by improving ZnSe QDs fluorescence.