This work discusses the photoluminescence properties of doped semiconductor nanoparticles by adding cadmium(II) nitrates post-synthetically to the terbium cation incorporated zinc sulfide [Zn(Tb)S] nanoparticles at room temperature to generate the Zn(Tb)S/Cd nanoparticles. The evolution of nanoparticle's emission is monitored as a function of amount of Cd 2+ , with [Zn(Tb)S]/[Cd 2+ ] = 1:10 −4 to 1:10, providing an opportunity to access materials of different chemical compositions. Structural features, as evaluated by X-ray diffraction and energy-dispersive X-ray spectroscopy, indicate a partial cation exchange of zinc by cadmium. No apparent replacement of terbium is noticed throughout the post-synthetic modification of the Zn(Tb)S nanoparticles until the relative reactant ratio reaches 1:10, and this only becomes noticeable with [Zn(Tb)S]/[Cd 2+ ] = 1:50. Remarkable differences in both broad and sharp emissions of nanoparticles and Tb 3+ , respectively, have been observed in the post-synthetic modification. The reaction initiates with a blue shift of nanoparticle's broad emission, and a further increase in Cd 2+ content results in a red shift. Tb 3+ emission, despite its insensitivity in the spectral band position due to the intra-configurational 4f transitions, shows a decrease in emission efficiency following post-synthetic modification. Formation of alloyed particles, however, significantly improved excitation contribution approaching the visible spectral region. Lifetime measurements of nanoparticles and Tb 3+ emission support the exchange of cations and the role of competitive nonradiative deactivation pathways, respectively. Collectively, nanoparticles with [Zn(Tb)S]/[Cd 2+ ] = 1:10 −4 to 1:10 −3 , 1:10 −2 , 1:10 −2 to 1:10, and 1:50 are argued to form Cd 2+ -induced surface trap-passivated Zn(Cd)(Tb)S, onset of Zn 1−x Cd x (Tb)S alloy formation, Zn 1−x Cd x (Tb)S alloys of varying compositions, and Zn 1−x Cd x S nanoparticles, respectively. Finally, this work provides a foundation to tune the properties of any emissive doped semiconductor nanoparticles in a lesser synthetically demanding fashion and has important implications in developing such materials.

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The role of surface capping ligands in controlling dopant photoluminescence in semiconductor nanoparticles is examined by monitoring emission in terbium cation incorporated zinc sulfide [Zn­(Tb)­S] nanoparticles, as a function of [H+] that is varied postsynthetically. Increases in Tb3+ emission of ∼6 and ∼1.3 times are observed on changing the pH from 4 to 7 and from 7 to 11, respectively. An increased contribution of host sensitization over direct excitation is observed under basic conditions. Subtle structural modification of the capping ligand is argued to be solely responsible for the dopant emission in the acidic–neutral range. The neutral–basic range in addition to this effect has a minor contribution from alteration in band alignment as well. A major outcome from this work relates to identifying the role of the terminally placed functional group in the capping ligand to control emissions from both the host (zinc sulfide nanoparticles) and guest (Tb3+), with a pronounced effect on dopant Tb3+ emission in the 1-thioglycerol capped Zn­(Tb)S nanoparticles. These results identify surface engineering as an important modulator, in addition to the primary criteria of (a) band gap engineering and (b) breaking (or optimizing) dopant local site symmetry in maximizing (or guiding) dopant emission in doped semiconductor nanoparticles.

Postsynthetic modification of inorganic nanoparticles (NPs) involving appropriate cation pairs at or near ambient conditions can exchange their spatial positions. The characterization of final products from these reactions although attracted...

Cation exchange by post-synthetic modification of inorganic nanoparticles (NPs) are commonly monitored by probing alterations of NP’s core, and not much is known on surface capping ligand’s ability to probe...