Synthesis of anisotropic silver nanoparticles and investigation of their sensory properties

Article abstract of DOI:10.1134/S0036023612020283

A simple procedure has been proposed for synthesis of planar triangular silver nanoparticles. Optimal conditions have been determined for particles to form, and the particles have been characterized by physicochemical methods. The halide-ion-sensory properties of sols of anisotropic silver nanoparticles prepared in different ways have been studied; sensitivity to halide ions is based on the changes in positions and intensities of longitudinal surface plasmon resonance (SPR) peaks in the range 500-800 nm in the optical absorption spectra of solutions. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0036023612020283

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 2, pp. 152–159. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.A. Vishnyakova, S.V. Saikova, R.B. Nikolaeva, Yu.L. Mikhlin, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 2, pp. 192–200.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Synthesis of Anisotropic Silver Nanoparticles
and Investigation of Their Sensory Properties
E. A. Vishnyakovaa, S. V. Saikovaa, R. B. Nikolaevaa, and Yu. L. Mikhlinb
a Siberian Federal University, Krasnoyarsk, Russia
b Institute of Chemistry and Chemical Technology, Siberian Branch, Russian Academy of Sciences, Krasnoyarsk, Russia
Received June 25, 2010
Abstract—A simple procedure has been proposed for synthesis of planar triangular silver nanoparticles. Optiꢀ
mal conditions have been determined for particles to form, and the particles have been characterized by physꢀ
icochemical methods. The halideꢀionꢀsensory properties of sols of anisotropic silver nanoparticles prepared
in different ways have been studied; sensitivity to halide ions is based on the changes in positions and intenꢀ
sities of longitudinal surface plasmon resonance (SPR) peaks in the range 500–800 nm in the optical absorpꢀ
tion spectra of solutions.
DOI: 10.1134/S0036023612020283
Great attention has been given to nanoparticles of SPR peak position correlate with the interaction
metals and their compounds in recent years largely strength of surface silver atoms with aqueous anions.
Tang et al. [6] suggested that halide ions affect the
morphology of silver nanoparticles: initial nanoprisms
are transformed into nanodisks, and this is responsible
for the blue shift of the SPR peak.
due to their sensory properties. Of particular interest
are nanoparticles of nonspherical shapes (planar
nanoparticles, nanorods, and so on), for they feature
an anisotropy of optical properties, which are conꢀ
trolled by particle morphology and particle sizes and
also depend on the condition of their surfaces [1, 2].
For example, nonspherical gold and silver nanopartiꢀ
cles are a very efficient medium for surfaceꢀenhanced
Raman scattering, thereby holding great promise for
the Raman spectroscopy of adsorbate compounds and
individual molecules [3, 4].
In recent decades silver nanoparticles have been
manufactured in diverse shapes: cubes, prisms, planar
hexagons, disks, rods, fibers, and others [7–9]. Particꢀ
ular attention has been paid to the synthesis of nanoꢀ
particles in aqueous solutions, which provides, via easꢀ
ily varying reaction parameters, tailored sizes and
shapes of the resulting nanoparticles. Search for cheap
and environmentally friendly reagents is still relevant;
these reagents are to be admissible in subsequent use of
the nanoparticles and to provide high yields and simꢀ
ple processes for manufacturing nanoparticles.
One of the most pressing challenges, in particular,
in the need for environmental monitoring, is the creꢀ
ation of optical sensors with high sensitivity and resoꢀ
lution for the detection and quantitative analysis of
inorganic ions. It has recently been shown that in the
presence of these ions, the optical spectra of sols conꢀ
taining planar silver nanoparticles feature a characterꢀ
istic shift of longitudinal surface plasmon resonance
(SPR) peaks in the plane of nanoparticles. Usually,
these peaks appear in the visible and nearꢀIR ranges
(600–900 nm); in the presence of some ions, however,
they shift to short wavelengths, and the value of the
shift depends on the nature and concentrations of the
ions. Nabiev et al. [5] observed similar changes in the
spectra of sols of silver nanoplates (edge length: 70 nm;
thickness: 2 nm) in the presence of halide, dihydroꢀ
phosphate, and thiocyanate ions in concentrations of
2−
Based on the analysis of related literature, we can
distinguish two main ways of manufacturing anisotroꢀ
pic silver nanoparticles in aqueous solutions: a oneꢀ
step process, which employs considerable concentraꢀ
tions of surfactants to control the nanoparticle growth
direction [10, 11]; and a twoꢀstep process, which proꢀ
vides small spherical silver particles, soꢀcalled nuclei,
and their subsequent growth under certain conditions
[12–15]. The parameters of nuclei synthesis have been
found to largely influence the properties of more comꢀ
plex structures formed on their basis. In preparing silꢀ
ver nuclei, for example, environmentally unsafe
reducing agent (sodium borohydride) is used in the
presence of citrate ions and surfactants. Earlier [16] we
demonstrated the usefulness of glucose (a green bioꢀ
compatible reagent) instead of the borohydrides, withꢀ
out any additional stabilizers [16].
(4–20)
×
10–6 mol/L. Meanwhile, F–
,
CH COO–,
SO4 ,
3
−
−
and
anions and inorganic cations (e.g.,
ClO4
NO3 ,
Zn2+, Cd2+, and Cu2+) had no effect on the spectral
pattern. The mechanism of this phenomenon is yet
This study was intended to manufacture anisotroꢀ
unclear. Nabiev et al. [5] believe that the changes in pic silver nanoparticles using nuclei that were syntheꢀ
152

SYNTHESIS OF ANISOTROPIC SILVER NANOPARTICLES
153
sized using sodium borohydride or glucose and comꢀ was spread over an amorphous carbon film fastened to
pare the halideꢀionꢀsensory properties of the nanoparꢀ a copper grid and dried at room temperature.
ticles prepared in these ways.
Further, the halideꢀionꢀsensory properties of the
asꢀprepared silver nanoparticles (sets 1 and 3) were
studied. For this purpose, to 4 ml of nanoparticle sols
were added sodium fluoride, sodium chloride, sodium
bromide, and sodium iodide solutions (0.5 mL each)
EXPERIMENTAL
All chemicals were of at least pure for analysis grade
and were used as received. Hydrazine hydrate was preꢀ
pared from a saturated hydrazine sulfate solutions (c =
0.22 mol/L) by ion exchange (on anionꢀexchanger
ABꢀ17ꢀ8 in OHꢀform) in a dynamic mode.
A representative twoꢀstep process for manufacturꢀ
ing silver nanoparticles comprised the first step of preꢀ
paring nuclei by one of the following variations:
in various concentrations (
10–3 mol/L); after stirring, the resulting colloids
were studied spectrophotometrically.
9 × × ×
10–6, 9 10–5, 9 10–4, or
9
×
For recording Xꢀray photoelectron spectra (XPS
spectra), a sol drop on pyrographite was dried in the
vacuum lock chamber of a SPECS spectrometer. The
spectra were excited by nonꢀmonochromatized Mg
K
α
radiation of an Xꢀray tube at the 8ꢀeV transmission
energy of a PHOIBOS 150 MCDꢀ9 energyꢀdispersive
analyzer (narrow scans). The pressure inside the anaꢀ
lytical chamber did not exceed 10–9 mBar.
(a) Borohydrides reduction (Zou’s method [17]):
0.5 mL of silver nitrate solution (
1 mL of citrate solution ( = 0.034 mol/L) were added
to 98 mL of distilled water; after several minutes of
stirring, 0.5 mL of NaBH4 ( = 0.02 mol/L) was
c = 0.059 mol/L) and
c
c
added, and the mixture was allowed to stand at room
temperature for 24 h; this provided solution A.
RESULTS AND DISCUSSION
An SPR peak in optical absorption spectra at 390 nm
is intrinsic to spherical silver nanoparticles with sizes
exceeding 2 nm [18]. A longꢀwavelength shift of this
peak by several tens of nanometers indicates either an
increase in particle size or a change in ambient permitꢀ
tivity, specifically, surface adsorption. The appearance
of a longꢀwavelength peak shifted by several hundred
nanometers, indicates either the anisotropy of nanoꢀ
particles or their aggregation and is due to resonance
electron density oscillations in the direction of the
longer axis. The main decisive factor for the SPR peak
position for planar or elongated particles is the aspect
ratio, for example, the thicknessꢀtoꢀlateral length
ratio for nanoplates.
The optical absorption spectra of the sols that we
obtained at the first step by reacting silver ions with
sodium borohydride (the SPR peak was at 390 nm) or
with glucose (the SPR peak at 410 nm), imply that
spherical nuclei are formed regardless of the nature of
the reducing agent. Such the nuclei are larger, which
does not, however, keeps them from forming planar
nanoparticles at the second step (table).
Along with planar particles, the final product conꢀ
tains spherical nanoparticles, which are the major
contributors to the shortꢀwavelength SPR peak (e.g.,
at 430 nm) and are observable by TEM. Centrifuging
for 30 min at 8000 rpm fails to separate planar and
spherical nanoparticles, evidently, because of the
closeness of their masses.
Anisotropic nanoparticles (including planar ones)
have a lower aggregative stability than spherical or
polyhedral particles [19, 20]. Our studies showed that,
when sols of set 2 were aged for 10 days at room temꢀ
(b) Glucose reduction [16]: to 10 mL of 0.005 M
silver nitrate solution (contained in a 50ꢀmL heatꢀ
resistant beaker), were poured 10 mL of 0.05 M gluꢀ
cose solution and heated for 10 min on a water bath
(300 mL water) in a microwave oven (at 700 W power);
this provided solution B.
At the second step, anisotropic silver nanoparticles
were manufactured by the following two main proꢀ
cesses:
–Process I was a consecutive addition method [17]:
to 5 mL of solution A (set 1) or solution B (set 2) were
poured 0.3 mL of 0.04 M hydrazine hydrate solution
and 0.1 mL of 0.04 M sodium citrate solution; the total
volume was brought to 20 mL with distilled water; this
provided solution 1. Further, a set of solutions was preꢀ
pared where each subsequent solution was obtained by
adding a 10ꢀmL portion of the preceding solution with
0.3 mL of 0.04 M hydrazine hydrate solution and 0.1
mL of 0.04 M sodium citrate solution; each time, the
total volume of the system was brought to 20 mL with
distilled water. To each asꢀprepared solution, 10 mL of
5.9
×
10–4 M silver nitrate solution was added at a rate
of 1 mL/min under vigorous stirring;
–Process II consisted of oneꢀtime addition of
reagents (set 3): to solution B (
time: 5 min to 2 days) were added 0.04 M sodium citꢀ
rate solution ( = 0.05–1.25 mL) and 0.04 M hydraꢀ
zine hydrate solution ( = 0.1–0.75 mL). The total
volume was brought to 10 mL with distilled water, after
which 10 mL of 5.9
10–4 M silver nitrate solution was
V = 0.01–1 mL; aging
V
V
×
added in 1ꢀmL increments in 1ꢀmin intervals under
continuous stirring.
The resulting colloidal solutions were studied specꢀ perature, some systems indeed featured the loss of
trophotometrically in the wavelength range from 300 aggregative stability accompanied by precipitation or
to 800 nm (Specol 1300) and by transmission electron silver mirror (see table; solutions 1, 2). In other cases
microscopy (TEM) (JEOL JEMꢀ2100) at an accelerꢀ (solutions 3 and 4), the longꢀwavelength peak slightly
ating voltage of 200 kV. In the latter case, a sol drop shifted to the blue and its intensity was reduced, which
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

154
VISHNYAKOVA et al.
, nm) and colors of colloidal silver
SPR peak positions (
solutions prepared by process I
λ
attributed to the stabilizing effect of citrate ions, whose
concentration increases with the solution number.
The multistep manufacture of silver nanoparticles
according to process I is rather lengthy and laborious
and suggests the use of toxic borohydride. We propose
a simpler process for manufacturing anisotropic nanoꢀ
particles with oneꢀtime addition of reagents (process II)
using nuclei prepared by glucose reduction. It is now
believed that planar nanoparticles are mostly formed
via agglomeration (preferably, via twinning) of the iniꢀ
tial nuclei followed by oriented anisotropic crystal
growth, so that the amount of nuclei and their aging
time are important factors for the carrying out of the
second synthesis step.
λ
1
λ
2
Color
Solution
No.
Set I
1
2
3
4
5
430
430
490
470
510
550
550
710
630
–
Maroonꢀred
Violet
Blue
Grayꢀgreen
Green
Set 2
1
2
3
4
5
410
410
410
410
410
490
570
650
610
590
Orange
Red
The solution volume of nuclei and their aging time
were varied in our experiments that were intended to
manufacture silver nanoparticles by process II. We disꢀ
covered that the SPR peak of sufficient intensity
appears in the range 650–900 nm provided that the
nuclei solution volume is approximately 0.1–0.2 mL
(Fig. 1a), which is likely to provide optimal conditions
for nuclei to agglomerate. At low nuclei concentraꢀ
Emerald green
Blueꢀgreen
Blue
may serve as an indication of a partial transformation
of planar to spherical nanoparticles [20]. In solution 5,
anisotropic particles did not undergo any changes for
10 days. The increased stability of nanoparticles may be
tions (
formed; rather, spherical particles are grown. While at
high concentrations ( = 0.5 mL), a broad absorption
V = 0.01 mL), anisotropic nanoparticles are not
V
peak is observed, indicating that particles are agglomꢀ
erated disorderly, which likewise does not favor the
formation of homogeneous silver nanoprisms.
A, arb. units
(а)
3.0
2.5
2.0
1.5
1.0
0.5
0
Optimal agglomeration is likely to be enhanced by
aging nuclei for 40 min (Fig. 1b, curve
aging, the effectiveness of their use (yield of planar
nanoprisms) decreases dramatically (Fig. 1b; curves ).
3). Upon longer
4, 5
This might result from the oxidation of nanoparticles,
as proven by reduction in peak intensity at 410 nm.
1
4, 5
3
6
2
Studies of the effect of sodium citrate concentraꢀ
tion showed that growth of anisotropic particles is
favored by values in a range of (2–5)
wellꢀdefined SPR peak appears at ~600 nm). At lower
sodium citrate concentrations (
10–4), as at higher
concentrations ((1–2)
10–3), too, the peak at 410 nm
×
10–4 mol/L (a
300
400
500
600
(b)
700
800
900
, nm
λ
1
×
A, arb. units
×
grows in intensity and the longꢀwavelength peak disꢀ
appears; that is, most of the particles formed are
spherical. Likely, optimal citrate ion concentrations
are required for crystallite growth to be inhibited only
in the Ag (100) plane and thereby the formation of plaꢀ
nar nanoparticles to be inhibited, too. Moreover,
sodium citrate in high concentrations exhibits reducꢀ
ing properties, and this is likely to be responsible for
the nucleation of new crystals and their isotropic
growth.
3.0
2.5
2.0
1.5
1.0
0.5
0
4, 5
3
1, 2
300
400
500
600
700
800
900
, nm
λ
Dependence on hydrazine hydrate concentration
also has an extreme character: the concentration optimal
for planar nanoparticles to form is (5–10) ×
10–4 mol/L.
Fig. 1. Effects of (a) nuclei solution volume: (
0.05, ( ) 0.1, ( ) 0.2, and ( ) 0.5 mL (aging time: 40 min)
and (b) aging time: ( ) 5 min, ( ) 15 min, ( ) 40 min, (
120 min, ( ) 2 days (nuclei volume: 0.2 mL) on the pattern
of electronic absorption spectra of silver sols. Hydrazine
hydrate concentration:
concentration:
1) 0.01, (2)
3
4
5
As the concentration of the reducing agent increases
further, the total number of silver nanoparticles in the
system decreases (the SPR peaks are reduced in intenꢀ
sity), possibly because of their solubilization by excesꢀ
1
2
3
4)
5
–4
5
×
10 mol/L; sodium citrate
–4
2
×
10 mol/L.
sive N2H4 ⋅ H2O, which expresses oxidizing properties.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

SYNTHESIS OF ANISOTROPIC SILVER NANOPARTICLES
155
of local supersaturation. This is signified by the strong
increase in SPR intensity at 420 nm, which correꢀ
sponds to spherical particles. Further, a strong
increase in nuclei concentration is likely accompanied
by their uncontrolled agglomeration (proven by the
appearance of a small peak at 490 nm).
A
3
, arb. units
2
1
0
Thus, the optimal parameters for manufacturing
anisotropic silver nanoparticles (according to process II)
1
are as follows:
chydrazine hydrate = 1
10⎯ 4 mol/L; incremental addition of a
V
(Ag0) = 0.1 mL; aging time: 40 min;
2
×
10–3 mol/L; csodium citrate = 2
10–4 M silꢀ
×
3
×
ver nitrate solution at a rate of 1 mL/min. Under these
conditions, we obtained green colloidal solutions with
longꢀwavelength plasmon absorption peaks approxiꢀ
mately at 710–750 nm, which corresponds to the forꢀ
mation of planar triangular particles. This is proven by
micrographs of silver nanoparticles (Fig. 3), where one
can see planar particles with nearꢀtriangular shapes
and sizes of ~100 nm, as well as fine spherical particles
with sizes of ~10–15 nm.
300 400 500 600 700 800 900 1000
, nm
λ
Fig. 2. Effects of the concentration and addition mode of
the precursor silver nitrate solutions on the pattern of elecꢀ
tronic absorption spectra of anisotropic silver nanopartiꢀ
cles: (
1) 0.059 M AgNO is added rapidly and (2) 0.00059 M
3
3
AgNO is added in increments.
The halideꢀionꢀsensory properties of silver nanoꢀ
particles (sets 1 and 3) have been studied. The asꢀmanꢀ
ufactured particles had different morphologies and
plasmon resonance spectra. Samples of set 1 typically
feature two peaks of commensurate intensities near
This behavior of hydrazine hydrate was noted by Saikoꢀ
va et al. [21].
The effect of silver nitrate concentration in soluꢀ
tion and the schedule of its addition is illustrated by
Fig. 2. If the synthesis is carried out with an incremenꢀ
tal addition (at 1 mL/min) of dilute (0.00059 M) silver
nitrate solution, planar metal nanoparticles are proꢀ
420 and 580 nm (Fig. 4, curve 1). This indicates (and
is verified by microscopic data; see Fig. 5) a high perꢀ
centage of planar triangular particles with sizes of
about 30–50 nm, that is, finer particles than in sols of
set 3 (Fig. 3). In the spectra of sols of set 3, the narrow
shortꢀwavelength peak has a higher intensity than the
longꢀwavelength peak in the region of 700–900 nm, for
duced (curve
2). Rapid, oneꢀtime addition of 0.1 mL
of comparatively concentrated (0.059 M) solution is
likely to generate a lot of nucleation centers as a result the reason that, along with planar particles which are
(а)
(b)
Particles fraction, %
40
30
20
10
0
5
15
30
Diameter, nm
50
80
100 nm
Fig. 3. (a) Electronꢀmicroscopic image of silver nanoparticles (set 3) and (b) particleꢀsize bar diagram.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

156
VISHNYAKOVA et al.
arb. units
(a)
A
, arb. units
A,
(а)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.6
1.4
1.2
1.0
0.6
0.6
0.4
0.2
1
2
3
4
5
2
1
3
4
5
700
400
500
600
(b)
800
900
, nm
300
λ
A,
arb. units
0
300 400 500 600 700 800 900 1000
λ, nm
(b)
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
A, arb. units
1
1.2
1.0
0.8
0.6
0.4
0.2
0
2
2
3
1
4
5
3
4
5
300
400
500
600
700
800
900
, nm
λ
300 400 500 600 700 800 900 1000
, nm
(c)
Fig. 4. Effects of the nature of anion ((a) chloride and (b)
iodide) and the anion concentration ((
(3) 1 × 10 , (4) 1 × 10 , and (5) 1 × 10 mol/L) on the
pattern of an optical spectrum of silver hydrosol (set 1,
solution 4).
λ
–6
1
) 0, (
2) 1
× 10 ,
A, arb. units
–5
–4
–3
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
2
1
3
4
5
0
300 400 500 600 700 800 900 1000
λ, nm
Fig. 6. Electron absorption spectra for solutions of anisoꢀ
tropic silver nanoparticles in the presence of (a) chloride
ions, (b) bromide ions, and (c) iodide ions: (
10 , (3) 1 × 10 , (4) 1 × 10 , and (5) 1 × 10 mol/L.
1
) 0, (
2
) 1
×
–6
–5
–4
–3
the nature and concentration of the anion. For the sols
of set 1, both peaks are simultaneously reduced in
intensity; for chloride ions, this reduction is rather
slow and monotonic, whereas for iodide ions, it is
abrupt even for micromolar concentrations. This
behavior can be explained by the reduction in overall
number of nanoparticles in the system as a result of
dissolution or coagulation in response to increasing
halide ion concentrations. This is signified by TEM
data (Figs. 7a, 7b), which imply that addition of iodide
ions changes the morphology of nanoparticles (planar
triangles transform into disks), their sizes are reduced,
100 nm
Fig. 5. Electronꢀmicroscopic image of silver nanoparticles
(set 1).
characterized by great ratios of the lateral size to thickꢀ
ness [22] than samples of set 2, there is a noticeable
amount of spherical nanoparticles (Fig. 6, curve
1).
The halideꢀionꢀinduced changes in the spectra
depend both on the nanoparticle morphology and on and their number is reduced, too.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

SYNTHESIS OF ANISOTROPIC SILVER NANOPARTICLES
157
20 nm
(b)
20 nm
(а)
100 nm
(d)
100 nm
(c)
–
–
–
Fig. 7. Electronꢀmicroscopic image of silver nanoparticles: (a) without
I and (b) in the presence of I (set 1); and (c) without I
–
and (d) in the presence of
I
(set 3).
Silver XPS spectra were also recorded before and
For silver nanoparticles of set 3 (Fig. 6), another
after sodium chloride and sodium iodide solutions pattern is observed: at relatively low concentrations,
were added (Figs. 8a, 8b). Inasmuch as the binding the longꢀwavelength peak systematically shifts toward
energies of silver XPS lines Ag 3d5/2 (~368.3 eV) virtuꢀ higher frequencies with a small reduction in intensity,
ally do not change in going from the metal to its comꢀ while the SPR peak at 420 nm remains almost
pounds, specifically to chlorides and iodides, Auger unchanged. Then, the longꢀwavelength peak disapꢀ
electron lines Ag MNN were also recorded (Figs. 8c, pears almost completely and the shortꢀwavelength
8d). For the asꢀprepared sol particles, the Ag peak is slightly reduced, and for each ion there is its
M4N4.5N4.5 energy (~357.9 eV) is characteristic of own threshold concentration. This concentration is
metallic silver. The line position remains practically maximal for fluoride ions (there are no changes in the
unchanged as chloride ions are added; that is, silver spectra at c = 0.01 mol/L) and minimal for iodide ions
remains in the metallic form, although the presence of (Fig. 6c). According to TEM data (Fig. 7d), halide
a small amount of chloride cannot be ruled out. Upon ions induce etching of angles of large nanoprisms in
addition of iodide ions, a small Ag M4N4.5N4.5 peak sols of set 3. At higher iodide ion concentrations,
appears with an energy of 355.9 eV, which is typical of nanoparticles (and spherical particles, too) probably
silver iodide. Sodium lines are also observed in the also dissolve, because the first SPR peak is reduced in
spectra, and part of the halide ions can be bound with intensity, too. In Auger spectra (Fig. 8d), however,
sodium rather than with silver. In this way, XPS specꢀ there are no lines corresponding to silver halide formaꢀ
tral data verify the inference that upon silver nanoparꢀ tion, which may be interpreted as resulting from the
ticles are likely to destroy addition of iodide ions to formation of bulky precipitates. The shift of the longiꢀ
produce AgI precipitates. Under the action of chloride tudinal plasmon resonance peak is likely to arise from
ions, however, either AgCl is not formed or its amount a decrease in the axial ratio of nanoparticles as a result
is insignificant.
of etching particle’s angles.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

158
VISHNYAKOVA et al.
(a)
Ag 3d5/2, 3/2
(b)
6
6
5
5
4
4
2
3
3
2
1
1
364 366 368 370 372 374 376 378
Binding energy, eV
378 376 374 372 370 368 366 364
Binding energy, eV
(c)
(d)
Ag MNN
Ag0
AgCl
AgI
Ag MNN
AgJ, Ag2O
6
AgCl
Ag0
6
5
5
4
4
3
2
2
1
1
348 350 352 354 356 358 360 362
Binding energy, eV
348 350 352 354 356 358 360 362
Binding energy, eV
Fig. 8. (a, b) Ag
3
d
XPS spectra and (c, d) Ag MNN Auger spectra of precursor silver sol (
1) before etching and (2) 2 min after
+
etching with Ar ions (5 keV, 30 A), and after adding chloride ions ( ) before and after ion etching, respectively) and adding
µ
3, 4
iodide ions (
5,
6
before and after ion etching, respectively) of pyrographite immobilized silver nanoparticles of (a, c) set 1 and (b,
d) set 3.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012

SYNTHESIS OF ANISOTROPIC SILVER NANOPARTICLES
159
4. I. R. Nabiev, R. G. Efremov, and G. D. Chumanov,
Usp. Fiz. Nauk 154, 459 (1988).
5. X. C. Jiang and A. B. Yu, Langmuir 24, 4300 (2008).
In summary, we have proposed quite a simple proꢀ
cess for manufacturing planar silver nanoparticles with
sizes of about 100 nm on the basis of nuclei prepared
by glucose reduction followed by directional growth.
We have studied the effects of various factors and
determined the optimal parameters of this process.
Plasmon resonance peaks from the resulting planar
silver nanoparticles showed high sensitivity to halide
6. B. Tang, S. Xu, J. An, et al., Phys. Chem. Chem. Phys.
112, 10286 (2009).
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Larger particles with greater ratios of the lateral size to
thickness are likely to be more promising for use in
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ACKNOWLEDGMENTS
4929 (2006).
The authors are grateful to S.M. Zharkov for carryꢀ
ing out the electronꢀmicroscopic studies. The studies
have been carried out at the Shared Facilities Center of
the Siberian Federal University. Financial support was
provided by the Federal Targeted Program “Research
and ResearchꢀTeaching Resources of Innovative Rusꢀ
sia” (GK 02.740.11.0269).
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RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 2 2012