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...

Post-synthetic modification of inorganic nanoparticles (NPs) provides a unique lesser synthetically demanding opportunity to access nanomaterials those are oftentimes not directly realizable by conventional synthetic routes. Trivalent lanthanide (Ln3+) incorporated (doped) semiconductor NPs can benefit from individual properties of the NPs and Ln3+ moieties. This work summarizes key outcomes from experiments when (a) ZnS /CdS /CdSe NPs are post-synthetically treated with Ln3+ to generate ZnS/Ln or CdSe/Ln [Ln = Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb] and CdS/Ln [Eu, Tb] NPs, (b) synthetically Tb3+ doped Zn(Tb)S NPs are post-synthetically modified with varying concentration of heavy metals like Pb2+/Cd2+ to generate Zn(Tb)S/M [M = Pb, Cd] NPs, and (c) the pH of Zn(Tb)S NPs aqueous dispersion is varied post-synthetically. Key observations from these experiments include (a) incorporation of Ln in all the post-synthetically prepared CA/Ln NPs, with presence of host sensitized dopant emission in select cases that can be rationalized by a charge trapping mediated dopant emission sensitization processes, (b) existence of rich photophysics in the sub-stoichiometric reactant concentration ratio, and (c) identifying the alteration of surface capping ligand structure as an important variable to control the Ln3+ emission. In summary, these experimental observations provide an easy control of reaction conditions either to generate Ln3+ inorganic NP luminophores or to control their electronic properties by modulating either the NP’s core or surface properties, and are of potential usefulness in various luminescence based applications.

This work investigates the tuning of electronic interaction between excited Tb3+ (Tb3+*) and Eu3+ by varying the excitation wavelengths, which consist of different electronic origins spanning the entire range of excitation spectra. Direct excitation bands of trivalent lanthanide cations (Ln3+) are accessed in the Ln-doped calcium fluoride, Ca(Ln)F2, nanoparticles (NPs). The experimental outcomes from the NPs are compared to that in the bulk solvent with freely floating entities. Remarkable excitation wavelength-dependent Tb3+–Eu3+ electronic interaction is observed in the NPs, with 370 nm excitation of Tb3+ being found to provide the optimum energy to maximize the Eu3+ emission. This excitation energy dependence is found to be less prominent in the bulk medium. Different mechanisms for Tb3+–Eu3+ electronic interaction are argued to be operative in the confined NP and bulk environments. The energy transfer efficiency from Tb3+* to Eu3+ in NPs can be maximized by (i) sole excitation of Tb3+ and (ii) maintaining the energy difference between the excitation energy and the Eu2+ ground energy level in the range of 4500–7500 cm–1. Additionally, we suggest the necessity of concomitant consideration of the steady-state and time-resolved response of both Tb3+ and Eu3+ emissions to decipher the Tb3+* → Eu3+ electronic interactions, instead of considering a single parameter to gauge such a process. These findings collectively provide important insights to design Tb–Eu-containing luminophores for their potential use in multiplex assays.

SummaryThe extraction behaviour of U (VI) from an aqueous nitric acid medium employing a 2-hydroxy-1-naphthaldehyde thiosemicarbazone in ethyl acetate has been studied in presence of different neutral donors like trioctyl phosphine oxide (TOPO), dimethyl sulphoxide (DMSO) and trioctyl amine (TOA). The extraction constant (log