| dc.description.abstract | This study explores the impact of defects on the structural, photoluminescent, and
photocatalytic behaviors of ZnS nanoparticles synthesized by two methods:
hydrothermal and microwave-assisted co-precipitation method. The defects are
induced by varying stoichiometric ratio and by doping rare earth elements.
In the hydrothermal synthesis method, point defects were introduced by varying the
S/Zn molar ratio and doping with Ce, La, and Y. These modifications led to the
formation of sulphur vacancies and sulphur dangling bonds, which play a crucial
role in enhancing photocatalytic activity under visible light. The sulphur defect
states and dangling bonds act as trapping sites for charge carriers, facilitating their
separation and prolonging their lifetimes, thereby significantly improving
photocatalytic efficiency. Photoluminescence (PL) measurements revealed an
emission peak around 470 nm, attributed to these sulphur-related defects, further
confirming their presence. However, the PL transitions corresponding to La, Ce, and
Y dopants were absent in the hydrothermal samples, likely due to the overlapping of
emission from the host material, masking the dopant-related emissions but the
luminescence intensity tuning is possible by doping. Additionally, the doping
process induced a phase transition from cubic to hexagonal structure, which also
contributed to the observed changes in material properties.
In contrast, ZnS nanoparticles synthesized using the microwave-assisted method did
not exhibit photocatalytic activity despite their smaller crystallite size. The absence
of sulphur-related PL emission peaks in these samples indicates lack of active
sulphur defects, which explains their inactivity in photocatalysis. However, the PL
spectra showed transitions corresponding to the dopants Er and Pr, reflecting the
influence of the synthesis method on the nature and distribution of defects.
This study highlights the importance of synthesis methods and conditions in defect
engineering, which enhance the photocatalytic and photoluminescence activity.
These findings provide a foundation for optimizing ZnS nanoparticles for targeted
applications in photocatalysis and optoelectronics. | |
