ISSN 0020-1685, Inorganic Materials, 2006, Vol. 42, No. 5, pp. 487–490. © Pleiades Publishing, Inc., 2006.
Original Russian Text © Yu.F. Kargin, S.N. Ivicheva, E.Yu. Buslaeva, T.B. Kuvshinova, V.D. Volodin, G.Yu. Yurkov, 2006, published in Neorganicheskie Materialy, 2006, Vol. 42,
No. 5, pp. 547–550.
Preparation of Bismuth Nanoparticles in Opal Matrices
through Reduction of Bismuth Compounds
with Supercritical Isopropanol
Yu. F. Kargin, S. N. Ivicheva, E. Yu. Buslaeva, T. B. Kuvshinova,
V. D. Volodin, and G. Yu. Yurkov
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
e-mail: yu.kargin@rambler.ru
Received October 19, 2005; in final form, November 21, 2005
Abstract—Bismuth nanoparticles have been produced in pores of opal matrices by reducing bismuth salts and
oxide compounds with supercritical isopropanol. According to transmission electron microscopy data, the
diameter of the SiO2 spheres in the opal matrices is about 260 nm, and that of the bismuth nanoparticles does
not exceed 80 nm.
DOI: 10.1134/S0020168506050074
There is wide research interest in nanoparticles as length scale of the chemical processes in its pores and
structural units of novel materials because they offer the physicochemical properties of the resulting sub-
properties missing in bulk solids and allow one to con- stances. Bismuth compounds are widely used in the
trol the lattice parameters, atomic dynamics, and ther- production of ferroelectric materials, scintillators,
mal, electrical, and magnetic properties of materials. semiconductors, and superconductors. When filling
All of these effects are related to the small size of nano- nanoscale pores in three-dimensional dielectric opal
particles and are highly dependent on their surface con- matrices, bismuth may exhibit unusual electrical prop-
dition and nanoparticle–matrix interaction. Isolated erties.
nanoparticles differ in properties from clusters forming
nanosystems. In connection with this, synthesis meth-
ods play an important role in determining the qualita-
tive characteristics of nanoparticles and nanostructures.
The process we used to produce bismuth–opal nano-
composites involved four main steps: (1) synthesis of
an opal matrix, (2) impregnation of the matrix with a
concentrated bismuth nitrate solution, (3) heat treat-
ment of the salt-impregnated matrix, and (4) reduction
of the decomposition products of bismuth nitrate in the
pores of the opal matrix to metallic bismuth with SC
isopropanol.
The chemical and phase compositions of the bis-
muth–opal nanocomposites were determined by x-ray
diffraction (XRD) (CuKα radiation, Geigerflex diffrac-
tometer), differential thermal analysis (DTA) (Netzsch
STA 409 thermal analyzer), chemical analysis, and
x-ray microanalysis (Cameca MS-46). The size of bis-
muth-containing nanoparticles was determined by
transmission electron microscopy (TEM) on a JEOL
JEM-100B. The specimen was dispersed in an alcohol-
in-water solution by sonication, and the dispersion was
applied to a copper grid coated with poly(vinyl formal)
and carbon.
Isolated nanoparticles can be prepared by a variety
of processes [1–5]. Yurkov et al. [4] have recently pro-
posed a technique for producing isolated bismuth-con-
taining nanoparticles (in oxide, chloride, or oxychlo-
ride form) via thermal decomposition of appropriate
salts in a high-temperature solution of high-pressure
polyethylene. They have shown that the composition of
the bismuth-containing nanoparticles stabilized in a
polyethylene matrix can be varied, e.g., using well-
known reactions (with KOH, O2, H2O2, and Cl2)
and also reactions of supercritical (SC) isopropanol
with the nanoparticles. Nanoparticles can also be stabi-
lized on the surfaces of various microgranules, includ-
ing SiO2.
In this paper, we report the preparation of bismuth
nanoparticles in pores of three-dimensional opal matri-
ces through the reduction of bismuth compounds with
SC isopropanol.
Opal matrices were prepared by hydrolytic polycon-
densation of tetraethyl orthosilicate (TEOS) in an alco-
hol–ammonia medium [6, 7], followed by sedimenta-
tion of the resultant silica spheres with no thermal or
An opal matrix, made up of monodisperse SiO2
spheres in a cubic close-packed arrangement, may mechanical influences. TEOS hydrolysis may lead to
function as a set of nanoreactors, determining the the formation of different polymer chains, which would
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