Full text of DOI:10.1007/BF02879535

Vol. 44 No. 2
SCIENCE IN CHINA (Series B)
April 2001
Resonance scattering spectroscopy of gold nanoparticle
JIANG Zhiliang (蒋治良), FENG Zhongwei (冯忠伟), LI Tingsheng (李廷盛),
LI Fang (李 芳), ZHONG Fuxin (钟福新), XIE Jiyun (谢济运)
&
YI Xianghui (义祥辉)
Institute of New Technology and Material, Guangxi Normal University，Guilin 541004, China
Correspondence should be addressed to Jiang Zhiliang (email: zljiang@gl.gx.cninfo.net)
Received October 8, 2000
Abstract The gold nanoparticles in diameter of 10—95 nm have been prepared by Frens proce-
dure, all of which exhibit a resonance scattering peak at 580 nm. The mechanism of resonance
scattering for gold nanoparticle has been considered according to the wave motion theory of
nanoparticle in liquid. The principle of superamolecular interface energy band(SIEB) has been set
up and utilized to explain the relationship between the diameter and colors for gold nanoparticle in
liquid. A novel spectrophotometric ruler for the determination of the diameter has been proposed
according to the relationship of the maximum absorption wavelength and diameter.
Keywords: gold nanoparticle, resonance scattering spectroscopy, ultraviolet-visible, absorption spectrophotometry,
spectrophotometric ruler.
Gold nanoparticle has fascinating chemical and physical properties, and has important value
[
1—3]
in the fundamental and application research fields
. Gold immunolabeling technique has
[
4]
unique advantages , and has become the fourth immunolabeling technique in clinic medicine. It
is also one of the first selected objects and underlaying materials in nanochemistry, agglomeration
[
3, 5, 6]
[7]
physics and nanomaterial science
. In1993 , a new resonance scattering spectroscopy was
[
8]
used for biomacromolecular research . In 1995, it was succesfully applied to the determination of
[
9]
ultratrace amount of inorganic ions . Recently, it has been utilized in biochemical analysis, su-
[
10—17]
peramolecular photochemistry and photochemical analysis
, giving satisfactory results. Ag,
Pt, TiO2 nanoparticles and superamolecules in liquid have been prepared by microwave
high-pressure liquid procedure and photochemical procedure. The resonance scattering spectros-
copy has been examined. The nanoparticles and superamolecules in big size are fundamental
cause to exhibit resonance scattering spectrum. The influence factors on resonance scattering
[
15—17]
spectra include shape, diameter, rigidity, refration index and absorption properties
. At pre-
sent，the mechanism of resonance scattering is not clear. The gold nanoparticle’s resonance scat-
tering and UV-visible absorption spectra have been investigated by taking the nanoparticle and
superamolecule as a whole.
1
Experimental
1
.1 Apparatus and reagents
Model RF-540 spectrofluorimeter (Japan), U-3400 UV-visible spectrophotometer (Japan) and

1
76
SCIENCE IN CHINA (Series B)
Vol. 44
H-600 transmission electron microscope (TEM) (Japan) were used.
HAuCl solutions: 117 μg/mL Au (III); sodium citrate solutions: 10 mg/mL.
4
1
.2 Procedure
Gold nanoparticles of various sizes can be prepared by Frens procedure . Its diameter (d)
[
4]
was determinated by TEM. Its resonance scattering and absorption spectra were obtained by spec-
trofluorimeter and spectrophotometer.
2
Results and discussion
2
.1 The resonance scattering spectra for gold nanoparticle
Gold nanoparticles in various sizes can be prepared by controlling the addition amount of so-
dium citrate solution. The results of TEM indicate that the gold nanoparticle is globularity, and its
[
18]
diameters (table 1) are consistent with the reference . The gold nanoparticles in diameter of
0—95 nm exhibit a resonance scattering peak (λ ) at 580 nm (fig. 1), that is, λ has no relation to
1
rs
rs
d. The gold nanoparticle can also be prepared by means of microwave high-pressure liquid proce-
dure, using propanetriol, ethanol and oxalic acid as reductants. All those particles exhibit a reso-
nance scattering peak at 580 nm. Fig. 2 is scattering spectra (also called emission spectra). There
is a resonance scattering peak (first order) at 290 nm, a 1/2 fraction frequency scattering (second
order) peak at 2×290 nm and a 1/3 fraction frequency scattering peak at 3×290 nm when the
[19, 20]
excited wavelength λ is at 290 nm (that is, a half of the resonance scattering peak 580 nm)
.
ex
The gold nanoparticle exhibits a strongest resonance scattering peak at 580 nm, a weaker 2/3 frac-
tion frequency scattering peak at 870 nm (λrs +λrs /2) and a double frequency scattering peak at
[
21]
2
90 nm (λ −λ /2, also called anti-second order) as λ = 580 nm . Several mechanisms have
rs
rs
ex
[
12, 22—24]
been proposed to explain the cause of resonance scattering
. The first viewpoint is that
molecules absorbing low energy photon cannot transit to excited state of electron but excites to the
higher vibration energy level of ground state. The electron can return to the original level in a very
short time (about 10− s), with radiating the same frequency lights in all directions. However, we
know that the transition between vibration levels produces red and Raman spectra. The second
viewpoint is that the electron resonance occurs and strongly absorbs incident light wave when the
frequency of absorption electromagnetic wave is close to the intrisic frequency of harmonic elec-
tron. Part of the absorption energy transfers into heat energy (for example, vibration collision),
part radiates in light. The resonance scattering intensity increases greatly owing to this process of
absorption-rescattering, but the results reported show that the absorption is weak at the resonance
scattering wavelength for many nanoparticle systems in liquid. The third viewpoint is that light
scattering is because of the different polarities between the solvent and aggregations. Incident
electromagnetic wave induces and produces vibration, and the vibrator radiates light in all direc-
tions. Nonlinear optical theory may be used in the interaction system between the light and
nanoparticle in liquid, which can only explain the double- and three-times frequency scattering
12

No. 2
RESONANCE SCATTERING SPECTROSCOPY OF Au NANOPARTICLE
177
1)
etc. . In short, the above viewpoints cannot answer the following questions: why does it have the
same λ for various diameters? Why does it exhibit 1/2 (second order scattering),1/3 (third order
rs
scattering) and 2/3 fraction frequency scattering for gold nanopaticle？
Table 1 The properties for gold nanoparticle (57 μg/mL Au)
Added amount of
Diameter
Au atom number in each
No.
sodium citrate
Color
λ
max/ nm
λ
rs /nm
a)
/
nm
particle
−
1
/
mL·(100mL)
4
A
B
C
D
E
F
5
10
16
30
50
60
70
95
Salmon
red
517.8
518.4
522.0
526.4
531.2
537.0
553.3
580
580
580
580
580
580
580
3.10×10
5
4
1.27×10
5
1.5
1.0
0.75
0.6
0.42
red
8.37×10
6
red
3.88×10
6
red-violet
red-violet
red-violet
3
6.70×10
7
1.06×10
7
G
2.66×10
3
3
a) Au atom radius r = 0.144 nm. Its volume is 0.0125 nm . The volume for d nm Au nanoparticle is 4/3π (d / 2) = (π/ 6)d .
If Au atom forms spherical Au nanoparticle in surface-cubic structure, the ratio of Au atom volume to Au nanoparticle volume is
3
7
4.06%, so the number of Au in each nanoparticle is 30.99 d .
Fig. 1. Resonance scattering spectra for gold nanoparticle. Fig. 2. The scattering spectra for 80 nm Au particle. A, λex
=
C, E and F conditions are as in table 1.
290 nm; B, λ ex = 580 nm.
Results reported demonstrate that nanoparticle and superamolecule in big size are the main
[
16]
cause resulting in resonance scattering , indicating that the whole nanoparticle and su-
peramolecule must be considered in discussion of resonance scattering mechanism. In addition,
the surface energy of nanoparticle increases with the decrease of diameter (table 2), and some of
nanoparticles (or superamolecules) locate in the substate. According to the hypothesis of De
1
) Jiang Zhiliang, Zhong Fuxing, Li Tingsheng et al., Resonance scattering spectroscopic study of green silver nanoparti-
cle, Acta Chimica Sinica, 2000 (to be pressed).

1
78
SCIENCE IN CHINA (Series B)
Vol. 44
Broglie, all practical particles have properties of wave-particle. Nanoparticle in liquid also forms
De Broglie wave and has wave motion properties. Its wavelenth is λ , frequency is ν , propagation
d
d
[
25]
velocity is V; u is the motion speed of nanoparticle in liquid , and m indicates the mass, and its
momentum is P:
P = mu,
= h/mu,
=V / λ
(1)
(2)
(3)
λ
d
ν
d
d
.
Table 2 The relationship between nanoparticle diameter and surface atom
−
1
Diameter / nm
00
Containning atom number (particle)
Occupy ratio of surface atom(%)
Ratio surface energy/J·mol
7
2
1
8.46×10
5.9×10
5
2
0
0
2.5×10
10
20
40
80
99
4
3
1
3.0×10
5.9×10
2
5
4.0×10
2
2
1
2.5×10
4
30
5.9×10
When incident light frequency ν is the same as De Broglie wave frequency ν , De Broglie wave
d
can resonate with the incident light wave. Supposing that the collision between nanoparticle and
photon is elastic collision, there is conservation of momentum
mu = m c = constant,
(4)
p
where m and c are incident light mass and speed. From formulae (3) and (4), we know that the
p
larger the m, the slower its De Broglie wave motion speed of the nanoparticle. And the resonance
scattering frequency(or wavelenth) has no relation to the diameter(or mass). The nanoparticles in
excitated state produce stimulated radiation owing to the resonance between the De Broglie wave
and incident light wave, and the scattering light intensity increases greatly. The De Broglie wave-
lenth λd is the maximum resonance scattering wavelenth λ . The nonlinear effects of the interac-
rs
tion system result in 1/2, 1/3 and 2/3 fraction frequency scattering and double frequency scattering
spectra. This is in agreement with the above results.
2
.2 Absorption spectra
The UV-visible spectra show that the maximum absorption wavelenth λmax red-shifts with
the increasing of the diameter of the gold nanoparticle (table 1). In the process of forming (Au)
n
3
+
(
n =1, 2, …) by means of the reaction between Au and sodium citrate，fresh Au atoms(or small
gold nanoparticles) locate in a substable state. The ratio of the amount of surface nanoparticle at-
oms to the total amount of atoms increases sharply along with the decreasing of nanoparticle di-
ameter, so a large amount of atoms locate on the interface and their surface energy is high. The
atoms with the lowest energy in solid phase are in a metastable state because of the decreasing of
[
26,27]
particle diameter and increasing of surface energy
. There are strong molecular forces (in-
cluding induce, dispersion and tropism forces) between the gold atoms (or gold nanoparticle) and
3
+
3+
Au . Both of Au and Au have approximate energy and good symmetry.

No. 2
RESONANCE SCATTERING SPECTROSCOPY OF Au NANOPARTICLE
28] [29] 3+
179
[
3
3
By means of those molecular forces , Au dsp hybrid orbital and Au dsp hybrid orbital
alternate and form superamolecular interface energy band(SIEB) (figs. 3 and 4) and the surface
molecule on the superamolecule and nanoparticle is a key factor to determine the physical and
3
chemical properties. The SIEB energy in ground state is lower than the energy of Au dsp hybrid
3
+
3
orbital, and higher than that of Au dsp . That is to say, the formation of superamolecule causes
3
3+
3+
the decrease of Au dsp hybrid orbital energy and the increase of Au dsp hybrid orbital energy.
3
+
3+
+
So Au in (Au) ·nAu can be reduced easily to (Au)m+n by citrate. Similarly, Ag in
m
+
+
(
Ag) ·nAg or (AgCl) ·nAg superamolecules can be reduced photochemically under the con-
m m
dition of irradiation of visible light. This is identified by superamolecular photochemistry and
resonance scattering spectroscopy. For spherical (Au)n+m supramolecule (nanoparticle), the (Au)m+n
supramolecular SIEBs in excitated state and ground state broaden, and its energy gap decrease
3
+
Fig. 3. The figure of Au·Au SIEB.
2
Fig. 4. The figure of (Au) SIEB.
with n+m (that is, d increase) (see fig. 5), leading
that λmax shifts to red with the increase of the
diameter d. It must be pointed out that the elec-
trons for formation of SIEB are not in ground
state, but follow the Boltzmann distribution law.
Some of the electrons locate at the higher energy
band (for example, the SIEB in excited state).
That is to say, there are superamolecules in
higher energy.
Fig. 5. Diagram of interface energy band for nanoparticle
and superamolecule.
2
.3 Spectrophotometric ruler for gold nanoparticles
The gold nanoparticles prepared by sodium citrate procedure have been applied widely. The

1
80
SCIENCE IN CHINA (Series B)
Vol. 44
diameter determined is important. TEM is a
good method for the determination of the
diameter. However, it is not simple and fast.
It is not reliable to control the addition
amount of sodium citrate solutions to get
needed diameter. A novel, simple, fast and
reliable spectrophotometric ruler has been
proposed for the determination of gold
nanoparticle diameter according to the rela-
tionship between d and λmax (fig. 6).
The following equations are given ac-
Fig. 6. The relationship between d and λmax
.
cording to conic treatment of the data.
2
5
λ
max = (d +1.34×10 )/260,
(5)
(6)
5
1/2
d = (260λmax − 1.34×10 ) .
If only λmax was obtained by UV-visible spectrophotometer, the diameter of gold nanoparticle
can be calculated according to eq. (6). The results are in agreement with those of TEM. The ex-
3
+
periments indicate that the diameter is related to the heating procedure, the concentrations of Au
and sodium citrate. Eq. (6) only suits to the gold nanoparticle prepared by Frens procedure. Even
3
+
if using the system of sodium citrate-Au , and microwave high-pressure liquid procedure to pre-
pare gold nanoparticle, there should be a big error for the diameter determination according to eq.
(
6).
Based on the resonance scattering mechanism and SIEB principle，the photochemical
+
+
mechanism of (Ag) ·nAg and (AgCl) ·nAg may be easier to understand, explaining why the
m
m
+
+
+
Ag in (Ag)
m
·nAg and (AgCl)
m
·nAg superamolecular solutions is easier to be reduced than the
+
Ag in AgNO solutions using visible light irradiation. It can also be used to consider the sur-
3
face-enhanced resonance scattering etc.
References
1.
2.
3.
4.
5.
6.
Tang Fangqiong, Meng Xianwei, Cheng Dong et al., Glucose biosensor enhanced by nanoparticles, Science in China, Se-
ries B, 2000, 43(3): 268.
Van der Zande, B. M. I., Bohmer, M. R., Fokkinket, L. G. J. et al., Aqueous gold sols of rod-shaped particle, J. Phys. Chem.
B, 1997, 101: 852.
Krug, II. J. T., Wang, G. D., Emory, S. R. et al., Efficient Raman enhancement and intermittent light emission observed in
single gold nanocrystals, J. Am. Chem. Soc., 1999, 121: 9208.
Wang Fuyong, Preparation of colloidal gold probe and its applications, Foreign Medicine, Series of Clinic Biochemistry
and Assay (in Chinese),1991, 12(4): 145.
Clark, B. K., Gregorg, B. W., Avila, A. et al., Surface-enhanced electronic Raman scattering from self-assembled al-
kanethiol monokyers on gold surface, J. Phys. Chem. B, 1999, 103: 8201.
Wang Guanghou, The stable structure and magic number of atomic clusters, Progress in Physics (in Chinese), 2000, 20:
5
2.

No. 2
RESONANCE SCATTERING SPECTROSCOPY OF Au NANOPARTICLE
181
7
8
9
.
.
.
Pasternack, R. F., Collings, P. J., Gianncttd, A. et al., Resonance light scattering: A new technique for studying chromo-
phore aggregation, J. Am. Chem. Soc., 1993, 115: 5393.
Parkash, J., Robblee, J. H., Agnew, J. et al., Depolarized resonance light scattering by porphyrin and chlorophyll an ag-
gregates, Biophysical Journal, 1998, 74: 2089.
Liu Shaopu, Liu Zhongfang, Li Ming, The second order scattering spectroscopic study of ion associated complex and its
analytical applications, Acta Chimica Sinica (in Chinese), 1995, 53: 1178.
1
1
1
1
1
1
1
1
0. Huang Chengzi, Li Ke’an, Tong Shengyang, Spectroscopic study of the interation of soluble cation porphyrin and nucleic
acid, Chem. J. Chinese Universities (in Chinese), 1997, 18(4): 525.
1. Collings, P. J., Gibbs, E. J., Starr, T. E. et al., Resonance light scattering and its application in determining the size, shape,
and aggregation number for supramolecular assemblies of chromophores, J. Phys. Chem. B, 1999, 103(40): 8474.
2. Ma Qunqi, Liu Yuqun, Li Ke’an et al., Rayleigh light scattering and its application to biochemical analysis, Chin. Sci. Bull.
(in Chinese), 1999, 44(6): 682.
3. Jiang Zhiliang, Li Fang, Huang Shengmian et al., Study on the fluorescence system of PMo heteropoly acid-rhodamine B
and its application, Analytical and Testing Technology and Instruments (in Chinese), 1999, 5(3): 157.
4. Liang Hong, Sheng Xincan, Jiang Zhiliang, The photochemical study of HAS and BSA with resonance scattering and
fluorescence spectroscopy, Chinese Chemical Letters (in Chinese), 2000, 11: 251.
5. Jiang Zhiliang, Li Fang, Li Tingsheng et al., The relationship between gold nanoparticle diameter and resonance scattering
intensity, Chem. J. Chinese Universities, 2000, 21: 4888.
6. Jiang Zhiliang, Li Fang, Liang Hong, Resonance scattering spectroscopic study of the system of PMo heteropoly
acid-rhodamine S, Acta Chimica Sinica (in Chinese), 2000, 58: 1059.
7. Wang Liupin, Jiang Zhiliang, Resonance scattering spectroscopic study of the photochemical system of Ag(I)-benzilic acid,
Analytical and Testing Technology and Instruments (in Chinese), 2000, 6(1): 25.
1
1
8. Wang Chongqiang, Foundemental Molecular Immunity (in Chinese), Beijing：Beijing University Press, 1999, 243.
−
9. Liu Shaopu, Liu Zhongfang, Resonant luminescence and second order scattering spectra of Se(IV)-I crystal violet,
Chem. J. Chinese Universities (in Chinese), 1996, 17: 1213.
2
2
2
2
0. Huang Yongyan, Jiang Zhiliang, Wang Shengmian, The second order sacttering study of the system of AsMo heteropoly
acid-rhodamine B, J. Anal. Sci. (in Chinese), 2000, 16: 127.
1. Liu Shaopu, Liu Zhongfang, Resonant luminescence and second order scattering spectra of Hg(II)-cyanate-
Vigire blue 4R system and its applications, Chem. J. Chinese Universities (in Chinese), 1996, 17: 887.
2. Cheng Guozheng, Xu Jingou, Wang Xiangzhi et al., Fluorescence Analytical Methods (in Chinese), Beijing：Science Press,
1
990, 102.
3. Zhao Zaofang, Zhou Xingyao, Zhang Wuming et al., Instrumental Analysis (in Chinese), Beijing: High Education Press,
990, 7.
1
2
2
4. Chou Gongdu, Duan Liangyun, Basic Structure Chemistry (in Chinese), Beijing: Beijing University Press, 1995, 9—10.
5. Pasternack, R. F., Collings, P. J., Resonance light scattering: A new technique for studying chromophore aggrogation, Sci-
ence, 1995, 269: 935.
2
6. Zhang Lide, Mou Jimei, Nanomaterial Science (in Chinese), Shengyang: Liaoning Scientific and Techlogical Press, 1994,
2
2.
2
2
7. Zu Jianjun, Lin Xipin, Du Youwei et al., Nanostructure materials (in Chinese), Chinese J. Nature, 1999, 21(6): 315.
8. Sun Xiaoqiang, Meng Qi, Yan Haibo, Introduction of Superamolecular Chemistry (in Chinese), Beijing: China Oil and
Chemical Press, 1997, 137—138.
2
9. Xie Youchang, Shao Meicheng, Structural Chemistry, Vol. 1 (in Chinese), Beijing: People’s Education Press, 1979, 158—
1
59.