ISSN 1070-4272, Russian Journal of Applied Chemistry, 2015, Vol. 88, No. 6, pp. 914−920. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © O.E. Zhuravlev, I.A. Presnyakov, L.I. Voronchikhina, 2015, published in Zhurnal Prikladnoi Khimii, 2015, Vol. 88, No. 6, pp. 848−854.
INORGANIC SYNTHESIS AND INDUSTRIAL
Synthesis of Zinc Sulﬁ de Nanoparticles
in an Ionic Liquid, N-Decylpyridinium Tetraﬂ uoroborate
O. E. Zhuravlev, I. A. Presnyakov, and L. I. Voronchikhina
Tver State University, ul Zhelyabova 33, Tver, 170100 Russia
Received June 26, 2015
Abstract—Method for obtaining zinc sulﬁ de nanoparticles, “quantum dots,” in an ionic liquid, N-decylpyridinium
tetraﬂ uoroborate, is suggested. The average size and shape of the nanoparticles were determined by UV spec-
troscopy, dynamic light-scattering method, and scanning probe microscopy. It is shown that a high threshold
concentration of nanoparticles is reached in the ionic liquid, and raising the concentration of precursors in the
reaction mixture leads to an increase in the average size of nanoparticles. It is found that ultrasonic treatment
affects the nanoparticle size.
Semiconductor nanocrystals with sizes in the range
2–15 nm, composed of 10
atoms, fabricated on the
basis of inorganic semiconductor materials, such as Si,
InP, CdSe, ZnS, etc., and coated with a monolayer of a
stabilizer, have been named “quantum dots” (QDs).
The unique optical properties of QD make these
objects a promising material for application in a wide
variety of ﬁ elds. Among the most promising application
ﬁ elds of QDs are biology and medicine. For example, QDs
serving as tracers or markers attached to biomolecules
and antibodies can serve to trace their motion within an
organism and biologically bound QDs can be “tuned” to
detection of biomolecules.
The ﬂ uorescence peak of nanocrystals is narrow and
symmetrical, which makes it possible to reliably discern
the nanocrystal ﬂ uorescence signals of different colors
(up to ten colors in the visible spectral range). These
properties and the high photostability make QDs ideal
ﬂ uorophors for multi-color spectral coding of objects,
similarly to the bar code, but with multiple colors
and “invisible” codes fluorescent in the IR spectral
range . Semiconductor nanoparticles can ﬁ nd use in
optoelectronic systems, such as light-emitting diodes
and planar light-emitting arrays [2–4], lasers , solar
cell arrays and photovoltaic converters, i.e., in all cases
requiring variable, wavelength-tunable optical properties.
The technique suggested in 1993 by Bawendi and
co-authors  can be regarded as a basis for modern
methods for colloid synthesis of QDs. A coordinating
solvent, trioctylphosphine oxide, is placed in a reaction
vessel is charged and heated to 300°C in the atmosphere
of argon, and then a mixture of dimethylcadmium and
trioctylphosphine selenide is introduced with a syringe
through a septum.
Also known are other methods for obtaining zinc
sulﬁ de nanoparticles, e.g., from elementary sulfur, zinc
chloride, and oleylamine at 320°C in trioctylphosphine
oxide , from sodium thiosulfate and zinc nitrate in the
atmosphere of argon with the use of isopropanol , and
a number of other techniques [9–11].
The shortcomings of the above synthesis methods
are the low quantum efﬁ ciency of ﬂ uorescence due to
the surface defectiveness of nanocrystals, as well as the
necessity for using toxic organometallic and organic
reagents capable of spontaneous ignition in air and the
high synthesis temperature (200 to 350°C).
The method of colloid synthesis has a number of
advantages: possibility of controlling the nanoparticle
growth process by, e.g., variation of temperature
parameters, and obtaining nanoparticles in a powdered
form; comparatively low synthesis temperatures;