Structural Evolution Controls Photoluminescence of Post-Synthetically Modified Doped Semiconductor Nanoparticles
journal contribution
posted on 2019-11-20, 13:06 authored by Saoni Rudra, Madhumita Bhar, Prasun MukherjeeThis 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 Cd2+, with [Zn(Tb)S]/[Cd2+] = 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]/[Cd2+] = 1:50. Remarkable differences in both broad and sharp emissions
of nanoparticles and Tb3+, 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 Cd2+ content results in a red shift. Tb3+ 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 Tb3+ emission support the exchange
of cations and the role of competitive non-radiative deactivation
pathways, respectively. Collectively, nanoparticles with [Zn(Tb)S]/[Cd2+] = 1:10–4 to 1:10–3,
1:10–2, 1:10–2 to 1:10, and 1:50
are argued to form Cd2+-induced surface trap-passivated
Zn(Cd)(Tb)S, onset of Zn1–xCdx(Tb)S alloy formation, Zn1–xCdx(Tb)S alloys of varying
compositions, and Zn1–xCdxS 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.
