Controlled Terbium(III) Luminescence in Zinc Sulfide Nanoparticles: An Assessment of Competitive Photophysical Processes

The lanthanide photoluminescence in the trivalent terbium (Tb3+) incorporated zinc sulfide nanopartides [Zn(Tb)S] has been reported with the nanopartide size varying from 2.0 +/- 0.3 to 14 +/- 3 nm in diameter as a function of reaction temperature. In all the nanopartides, the Tb3+. luminescence has been sensitized by the nanopartide acting as an optical antenna. The relative contribution of different excitation bands in sensitizing Tbs luminescence in the Zn(Tb)S nanopartides has been found to be dependent on the size of the nanopartides. The observed Tb3+ luminescence efficiency in the Zn(Tb)S nanopartides has been rationalized by competing factors: (i) the sensitization efficiency that is guided by the relative energy level position of the Tbs ground and excited states with respect to the valence and conduction bands of the ZnS and (ii) the extent of incorporation of Tb3+ in the nanopartides. Additionally, it has been argued that the spectral overlap between the nanopartide (donor) emission and Tb3+ (acceptor) absorption is not a prerequisite in determining the Tb3+ emission in the Zn(Tb)S nanopartides studied.