The effect of stabilizers on reduction of silver(I) ions in ethyl acetate

Article abstract of DOI:10.1134/S0036023614090216

The effects of polyethylene glycol and polymethyl methacrylate on reduction of silver(I) ions in the CF₃COOAg-Q_r-EA system (where Q_r is quercetin and EA is ethyl acetate) were studied spectrophoto-metrically. The introduct

Full text of DOI:10.1134/S0036023614090216

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2014, Vol. 59, No. 9, pp. 998–1003. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © V.P. Smagin, O.V. Larina, 2014, published in Zhurnal Neorganicheskoi Khimii, 2014, Vol. 59, No. 9, pp. 1231–1236.
PHYSICAL METHODS
OF INVESTIGATION
The Effect of Stabilizers on Reduction
of Silver(I) Ions in Ethyl Acetate
V. P. Smagin and O. V. Larina
Altai State University, Barnaul, Russia
eꢀmail: smaginV@yandex.ru
Received February 17, 2014
Abstract—The effects of polyethylene glycol and polymethyl methacrylate on reduction of silver(I) ions in
the CF COOAg–Q –EA system (where Q is quercetin and EA is ethyl acetate) were studied spectrophotoꢀ
3
r
r
metrically. The introduction of these stabilizers to the system inhibits the redox process. The inhibition of
reduction of silver(I) ions is attributed to the predominance of complexation or to the diffusion factor at high
molecular weights and concentrations of compounds.
DOI: 10.1134/S0036023614090216
Metal nanoparticles and functional materials modꢀ
ified by them play a significant role in modern techꢀ
nology. They are distinguished by unique physical and
chemical properties and used to manufacture cataꢀ
lysts, magnetic and electric materials, and optical eleꢀ
ments [1–4]. Metal (in particular, silver) nanopartiꢀ
cles show promise for biology and medicine [5, 6].
Metal nanoparticles can be manufactured chemically.
Under certain conditions, the synthesis is accompaꢀ
nied by formation of colloidal solutions. Colloidal
solutions of metals are either used directly or as preꢀ
cursors for powder, film, and other materials, in parꢀ
ticular, optical quantum dots immobilized in solid
organic matrices [7–9]. Significant problems associꢀ
ated with colloidal systems are due to their low stabilꢀ
ity, which can be enhanced using stabilizers. Stabilizꢀ
ers inhibit degradation of colloidal systems, thus havꢀ
ing a direct effect on the formation of colloidal
particles and considerably modifying the technologiꢀ
cal processes of synthesizing the products. Hence,
searching for efficient stabilizers and optimal condiꢀ
tions for the stabilization of colloidal systems is quite
topical.
EXPERIMENTAL
Silver trifluoroacetate was synthesized by interacꢀ
tion of freshly precipitated Ag O nH O with trifluoꢀ
⋅
2
2
roacetic acid in water, isolated by evaporation of the
solvent, dried, and identified by IR spectroscopy using
data from [15, 16] as described in [17]. Quercetin of
pure grade (C H O7, Lachema), commercial stanꢀ
15
10
dardized polyethylene glycol samples of chemically
pure grade with molecular weight 1500 (PEG1500) and
6
(
000 amu (PEG6000), and polymethyl methacrylate
PMMA) synthesized by thermal radical polymerizaꢀ
tion in the presence of benzoyl peroxide at 70 C (Мr
10 amu, viscometry) were also used in this study.
The IR spectrum of the salt was recorded on an
Infralum FT 801 Fourierꢀtransform spectrometer in
°
~
6
1
×
–1
the range 4000–400 cm . Electronic absorption specꢀ
tra were recorded on a Specord UV Vis spectrophoꢀ
tometer in the range 200–800 nm. Absorbance at the
maximum of the absorption band was measured on an
SFꢀ46 spectrophotometer with respect to ethyl aceꢀ
tate. The photometric scale of SFꢀ46 was calibrated
using the procedure described in [18].
This study was aimed at elucidating the effect of
stabilizers of colloidal solutions on the reduction of
silver(I) ions in ethyl acetate.
RESULTS AND DISCUSSION
Stock solutions of silver trifluoroacetate and querꢀ
–3
Silverꢀcontaining systems were selected due to the cetin (at a concentration of 1.00 10 mol/L) in ethyl
×
properties of silver and silverꢀcontaining functional acetate were prepared using weighed portions of the
materials [6, 9–11]. Silver trifluoroacetate is well solꢀ compounds. The working solutions of silver trifluoroꢀ
uble in lowꢀpolarity organic solvents (in particular, in acetate and quercetin were prepared by diluting the
ethyl acetate whose physical properties are similar to stock solutions. Concentrations of the compounds
–4
those of acrylic monomers and polymers) [12]. Querꢀ were 4.00
×
10 mol/L. The concentrations and the
cetin has moderate reducing properties with respect to equimolar ratio correspond to the conditions for fabꢀ
silver ions in organic mixtures [11]. Polyethylene glyꢀ rication of the most stable colloidal solutions in this
col and polymethyl methacrylate are used as stabilizꢀ system [17]. When the quercetin solution was added to
ers of colloidal solutions of elemental metals and their the silver trifluoroacetate solution (or vice versa), the
derivatives [8, 13, 14].
resulting solution gradually became pink. The elecꢀ
998

THE EFFECT OF STABILIZERS ON REDUCTION
999
3
A
y
r
= 0.2 + 0.0194
= 0.994
x
1.0
2
0
.5
0
1
10
20
30
40
50
60
70
80
, min
τ
Fig. 1.
A
=
f(
τ
)
for the СF COOAg–Qr–EA system, cAg
:
cQr = 1 : 1, cAg
=
cQr
=
4.00
×
10–4 mol/L.
3
A
1
.0
.5
0
y
r
= –0.4 + 0.0117
= 0.997
x
0
y
r
= 0.0 + 0.0008
= 0.980
x
20
40
60
80
100
120
140
, min
τ
Fig. 2.
with PEG1500 added before the reaction was started (the compounds were added to the system in the following order:
CF COOAg, PEG1500, Qr).
A
=
f(
τ
) for the СF COOAg–Qr–PEG1500–EA system, cAg : cQr : cPEG = 1 : 1 : 1 (cAg = cQr = cPEG = 4.00 ×
10–4 mol/L)
3
3
tronic absorption spectrum featured a band with the added to the solutions containing silver trifluoroaceꢀ
maximum at 529 nm. Its intensity increased with time. tate and quercetin at different stages of the redox proꢀ
The solution was gradually becoming red. The funcꢀ cess.
tion
A
=
f( ) obtained for this system (Fig. 1) is similar
τ
Figure 2 shows an exemplary curve recorded after
PEG1500 was added to the system at the molle ratio 1 :
to that reported in [17]. It consists of three regions.
The first one (1, Fig. 1) corresponds to product accuꢀ
mulation with gradually increasing reaction rate. A
1
: 1 before the redox reaction was started. This curve
is significantly different from the original function. The
duration of the induction period increased to ~30 min.
The third region, typical of the initial curve (3, Fig. 1),
did not appear during the time that absorbance was
measured. Another order of adding the reagents and
the stabilizer to the system (e.g., silver trifluoroaceꢀ
tate–stabilizer–quercetin or quercetin–stabilizer–
silver trifluoroacetate) had no effect on the reaction
course.
~
5ꢀminꢀlong induction period can be distinguished in
this region. The second region is ~50 min long and feaꢀ
tures a linear rise of absorbance with time (2, Fig. 1). The
run of the function indicates that the reaction rate is
constant in this region. The third region (3, Fig. 1)
characterizes the completion of the redox process with
a gradual decrease in reaction rate due to the eliminaꢀ
tion of reagents from the system.
The effect of PEG1500, PEG6000, and PMMA on the
Figure 3 shows an exemplary curve recorded for the
reduction of silver(I) ions was detected as changes that system with PEG1500 added 20 min after the redox
occur in kinetic curves after these compounds had reaction had been started. This moment corresponds
been added to the systems. Polyethylene glycol and to the end of the induction period and of the period
polymethyl methacrylate were preliminarily dissolved when the reaction rate increases and reaches the linear
in a minimal amount of the corresponding solvent and region of the
A
=
f( ) function. The resulting depenꢀ
τ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 59 No. 9 2014

1000
SMAGIN, LARINA
A
y
r
= 0.2 + 0.0078
= 0.999
x
1.0
0
.5
0
0
20
40
60
80
100
120
140
, min
τ
Fig. 3.
A
=
f
(
τ
)
for the СF COOAg–Qr–PEG1500–EA system, cAg
:
cQr
:
cPEG = 1 : 1 : 1 (cAg
=
cQr
=
cPEG
=
4.00
10–4 mol/L)
×
3
with PEG1500 added 20 min after the reaction was started.
A
y
r
= 0.3 + 0.0077
= 0.995
x
1
.0
.5
0
y
r
= 0.0 + 0.019
= 0.998
x
0
0
20
40
60
80
100
120
, min
τ
Fig. 4.
A
=
f
(
τ
)
for the СF COOAg–Qr–PEG1500–EA system, cAg
:
cQr
:
cPEG = 1 : 1 : 1 (cAg
=
cQr
=
cPEG
=
4.00
10–4 mol/L)
×
3
with PEG1500 added on the 55th min after the reaction was started.
dence is a combination of the curves shown in Fig. 1
Figures 5 and 6 show the functions obtained for the
(
before 20 min) and Fig. 2 (after 20 min). The differꢀ systems where PEG1500 was added at different ratios
ence is in that the reaction rate decreases within the with respect to the reagents before the redox reaction
period of time corresponding to the linear region of and 20 min after it had been started. An increase in the
the curve, which is indicated by a decreased slope ratio reagents : PEG1500 molar ratio to 1 : 4 increased the
in the equation.
induction period to ~50 min. The reaction rate
increased at the second stage in accordance with the
Figure 4 shows an exemplary curve for the system
with PEG1500 added 55 min after the reaction was
started. This time corresponds to the end of the region
slope ratio in the function
A
=
f(τ) (Fig. 6).
Comparison of the resulting dependences (Figs. 1–
) shows that the strongest effect on reduction of silꢀ
6
of the function
A
=
f( ) that is characterized by a conꢀ
τ
ver(I) ions with quercetin in the system containing the
reagents and PEG1500 was observed after polyethylene
glycol had been added before the reaction started at a
stant rate of the redox reaction (2, Fig. 1). The result is
a combination of the curves shown in Fig. 1 (before
PEG1500 was added to the system) and Fig. 3 (after
PEG1500 was added to the system).
1
: 1 : 4 CF COOAg : Q : PEG molar ratio. A similar
3 r
effect was observed in the system with the 1 : 1 : 1
The systems containing PEG
and PEG
6000
in molar ratio between the components. In our opinion,
1
500
–4
–4
concentrations of 1.00
×
10 , 8.00
mol/L, which corresponds to the molar ratio components can be caused by the predominant comꢀ
CF COOAg : Qr : PEG = 1 : 1 : 0.25, 1 : 1 : 2, and 1 : 1 : 4 plexation of polyethylene glycol with silver trifluoroꢀ
×
10 , and 16.00
×
the effect observed at an equimolar ratio between the
–4
10
3
were further studied in a similar manner.
acetate in lowꢀpolarity ethyl acetate. Increasing polyꢀ
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 59 No. 9 2014

THE EFFECT OF STABILIZERS ON REDUCTION
1001
A
1
1
1
0
0
0
0
.4
1
.2
.0
.8
.6
.4
.2
y
r
= –0.3 + 0.012
= 0.999
x
2
y
r
= 0.1 + 0.0035
= 0.996
x
0
20
40
60
80
100
120
, min
τ
Fig. 5.
A
=
f
(
τ
)
for the CF COOAg–Qr–PEG1500–EA system, cAg
:
cQr
:
cPEG = 1 : 1 : 2 (cAg
=
cQr
=
4.00
×
10–4 mol/L; cPEG = 8.00
×
3
–
4
10
mol/L) with PEG1500 added (
1
) before the reaction was started and (
2
) 20 min after the reaction was started.
2
A
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
y
r
= 0.2 + 0.006
= 0.999
x
1
y
r
= –0.2 + 0.005
= 0.998
x
y
r
= 0.0 + 0.0002
= 0.96
x
0
20
40
60
80
100
120
, min
τ
Fig. 6.
A
=
f
(
×
τ
)
for the CF COOAg–Qr–PEG1500–EA system, cAg
:
cQr
:
cPEG = 1 : 1 : 4 (cAg
=
cQr
=
cPEG
=
4.00
×
10–4 mol/L;
3
–4
cPEG = 16.0
10 mol/L) with PEG1500 added (
1
) before the reaction was started and (2
) 20 min after the reaction was started.
ethylene glycol concentration increases the viscosity for PEG added to the solutions before the redox reacꢀ
of solutions; the diffusion factor starts having an addiꢀ tion was started. Increasing molecular weight of PEG
tional effect at 1 : 1 : 4 molar ratio between the reagents
and polyethylene glycol, which enhances the effect
observed.
is expected to enhance the effect of the diffusion facꢀ
tor. Increasing PEG6000 concentration in the solutions
(
the reagents : PEG6000 molar ratio from 1 : 1 : 0.25 to
Figure 7 shows the curves recorded for the systems 1 : 1 : 4) led to an almost complete attenuation of the
containing PEG6000 a different PEG–reagent ratios induction period and reduced the reaction rate. The
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 59 No. 9 2014

1002
SMAGIN, LARINA
A
1
1
1
1
0
0
0
0
.6
2
1
.4
.2
.0
.8
.6
.4
.2
y
r
= 0.1 + 0.0115
= 0.980
x
y
r
= 0.0 + 0.0126
= 0.991
x
y
r
= 0.0 + 0.00223
= 0.999
x
3
0
20
40
60
80
100
120
, min
τ
Fig. 7.
cQr cPEG = 1 : 1 : 0.25 (cAg
cPEG = 4.00
A
=
f
(
τ
)
for the CF COOAg–Qr–PEG6000–EA system when PEG6000 was added before the reaction was started. (
1
)
cAg
cQr
×
10–4 mol/L, cPEG = 16.0 10–4 mol/L).
:
3
:
=
cQr
=
4.00
cAg
×
10–4 mol/L; cPEG = 1.00
×
10–4 mol/L); (
2)
cAg
=
cQr
=
cPEG = 1 : 1 : 1 (cAg
=
=
×
10–4 mol/L); and (
3)
:
cQr cPEG = 1 : 1 : 4 (cAg
:
=
cQr = 4.00
×
A
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
2
1
y
r
= –0.2 + 0.0143
= 0.998
x
y
r
= –0.1 + 0.0092
= 0.999
x
0
20
40
60
80
100
120
, min
τ
Fig. 8.
СAg
A
=
f( ) for the CF COOAg–Qr–PMMA–EA system when PMMA was added before the reaction was started. CAg : СQr = 1 : 1
3
×
τ
–4
(
=
СQr
=
4.00
10 mol/L); weight of PMMA, g/25 mL: (1) 0.240 and (2) 0.015.
result shows good agreement with the proposed interꢀ
Thus, the effect of PEG and PMMA on the formaꢀ
pretation of the effects observed. However, it follows tion of colloids of elemental silver in lowꢀpolarity ethyl
acetate has been demonstrated. The effects observed
are caused by complexation of the compounds with
silver trifluoroacetate and increasing viscosity of soluꢀ
tions when their concentrations and molecular
weights were increased.
from the slope ratios (Figs. 6, 7) that addition of
PEG1500 to the system causes a more significant
decrease in the reaction rate than addition of PEG6000
under identical conditions. Hence, a conclusion can
be drawn that complexation plays a rather significant
role.
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cant than when polyethylene glycol was added. The
resulting curves are shown in Fig. 8.
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Translated by D. Terpilovskaya
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 59 No. 9 2014