Green and Sustainable Chemistry, 2012, 2, 26-28 Published Online February 2012 (
Comparative Study on Methods for Preparation of
Gold Nanoparticles
Khalida S. Merza1, Hadi D. Al-Attabi2, Zaid M. Abbas1, Hashim A. Yusr2
1Chemistry Department, College of Science, Wassit University, Al Kut, Iraq
2Physic al Department, Coll e ge of Science, Wa ssi t University, Al Kut, Iraq
Email: {dr_ksm, hadidawyich, zaid_almalki, hsmphys}
Received November 3, 2011; revised December 15, 2011; accepted December 25, 2011
The gold nanoparticles were prepared in many methods, differed in reducing and dispersion agents and stability. The
first solution was prepared by using potassium bitartrate as reducing agent and Polyethylene glycol as a dispersion fac-
tor. We got a solution of colloid gold with wine-red color that has been measured the particle size; it was between 50 -
200 nanometers. The second gold colloidal solution was prepared by using sodium citrate as a reducing agent and
without adding a dispersion agent, the color of the final solution is dark grey, but this solution did not remain stable,
deposition h appened quickly and crystals separated from the solution. The th ird one was prepared by using so dium cit-
rate as a reducing agent and the solution was heated to a certain temperature, and the color of the solution became dark
red after several minutes. Either the fourth method has been prepared gold colloid solution by using potassium bitartrate
as a reductant for the gold ion. We have noted that no reaction under normal conditions, while the reaction by heating
the solution to high temperature, and when added poly vinyl pyrrolidone will lead to a solution of colloild gold with
dark purple-r ed color and stab le under normal condition s for a long time. We measured the particles size in this experi-
ment; it was less than 100 nanometers. We conclude from the above that all the reducing agent needs to appropriate
conditions to complete the pro cess of reduction of gold ion, and to get the nano gold particles, therefo re; these particles
in the colloid so lution ne ed to dispersion factor to the surviv al of the particles widespread so that the solutions with cer-
tain concentration s of poly vinyl pyrrolidone can be proven in the process of stability of the gold colloid so lution.
Keywords: Nanotechnology; Gold Colloidal Solution; Nanoparticles
1. Introduction
Nanotechnology (N T) is the production and use of mate-
rials with purposely engineered features close to the ato-
mic or molecular scale and involves the investigation and
design of materials or devices at the atomic and molecu-
lar levels.
Two main approaches are used in nanotechnology. In
the “bottom-up” approach, materials and devices are built
from molecular components which assemble themselves
chemically by principles of molecular recognition. In the
“top-down” approach, nano-objects are constructed from
larger entities without atomic-level control. The original
meaning of “nanotechnology” refers to the ability to build
components from the bottom up, using techniques and
tools that are constantly being developed to become in-
tegrated, and whose performance is high. This technique
leads to provide the ability to create materials, devices
and systems with new functions and characteristics of
substance. As a result to that it has large applications in
the areas of manufacturing and production [1,2]. Nano-
particles are much smaller than those used in chemical
and industrial applications, where can be small enough
to enable them to enter into a living cell easily. In study-
ing of the elements and compounds, it is found that is
different when it is on the nano scale. Nanotechnology is
a wide range of flourishing scientific research. Manufac-
turing of most nanoparticles during industrial processes
as by products. Researchers at the University of Missouri-
Columbia discovered a method to prepare nanoparticles
by the addition of gold salts to a soybean-water mixture.
Through the interaction of chemicals in soybean with
gold salts has been producing stable gold nano particles
with no toxic by-products.
The researchers found a practical process to connect
the phytochemicals to cancer cells directly through the
gold particles and thus kill the cancer cells.
The researchers selected gold for their research be-
cause it is very stable, chemically, therefore, it is less
likely to lead to side effects in the body. They said that
the production process, they have pioneered, could easily
be replicated on a larger scale.The gold in HAuCl4.3H2O
complex as Au3+ ions are reduced to neutral gold atoms,
opyright © 2012 SciRes. GSC
where citrate ions act as both a reducing agent and a cap-
ping agent. The formation of gold nanoparticles can be
detected by observing the change in the solution to the
red color.The presence of the colloidal suspension can be
detected by the reflection of a laser beam from the parti-
cles. The layer of absorbed citrate anions on the surface
of the nanoparticles keep them separated. Switching to a
smaller anion allows the particles to approach more
closely and another color change is observed [3].
Colloidal gold is a suspension of sub-micrometer-sized
particles of goldin an aqueous medium. The color of the
solution is either red when the particles size less than 100
nm or a dirty yellowish color for larger particles. Due to
the optical and electronic properties of gold nanoparticles
is the area of research which ha ve a very broad [4].
Properties and applications of co lloid al go ld nanoparti-
cles depend upon shape. For example, rod like particles
have both transverse and longitudinal absorption peak,
and anisotropy of the shape affects their self-assembly.
Gold nanoparticles are prepared by the reduction of
chloroauric acid (H[AuCl4]), after addition of reducing
agent the solu tion is rapidly stirred leads to the reduction
of gold ion Ag3+ to neutral gold atom and the continua-
tion of the operation will turn out all the go ld ions to neu-
tral atoms and the solution becomes supersaturated. If the
solution is stirred v igorously enough that will lead to the
formation of nanoparticles uniform in size. To avoid the
particles from aggregating must use stabilizing agent or
to spread particles of each other. This agent can be func-
tionalized with various organic ligands to create organic-
inorganic hybrids with advanced functionality. It can also
be synthesised by laser ablation [5].
Chemical reduction methods have been extensively
us ed in the preparation of nanoparticles because these me-
thods are simple and cheap and can be used to prepare
large quantities of nanoparticles. Series of chemical re-
ductions have been utilized for the preparation of noble
metal Nanoparticles, which include H2, NaBH4, N2H2,
NH2OH, (CH3)2NH·BH3, ethanol, ethylene glycol, citrate,
formamide, ormald ehyde or Tollens r eagents, ascorbic acid,
and polyaniline or o-anisidine.
The aim of this research is to know the best, simple
and efficient method to prepare colloid al gold and itspar-
ticle size located within the nanoscale, for using it in
other applications.
2. Experimental
2.1. Materials
Hydrogen tetrachlorourate (III) trihydrate (HAuCl4·3H2O)
and poly vinyl pyrrolidone (PVP) were purchased from
Aldrich. Potassium bitartrate, polyethylene glycol (PEG)
and sodium citrate were purchased from Merck. For the
preparation of mi xture solution, deionized water was used.
2.2. The Methods
The colloidal forms of gold nanoparticles were prepared
by four methods:
First method: nanoparticles were obtained by heating
20 ml potassium bitartrate solution (0.5 wt%) with stir-
ring (in water bath) at 60˚C, and 20 ml of an aqueous
solution of HAuCl4 (1.0 Mm) containing polyet hyl ene gly -
col (1.0 w t%). Af ter 5 min the color of th e so lution chan ged
from light yellow to wine-red, indicating the formation of
Au colloidal nanoparticles.
Second method: the gold nanoparticles were obtained
by adding 20 ml of trisodium citrate (0.5 wt%) to 20 ml
of an aqueous solution of HAuCl4 (0.1 Mm) the solution
became a dark-grey after 20 min.
Third method: included preparation of gold nanoparti-
cles by heating 20 ml of HAuCl4 (1.0 Mm) on a stirring
hot plate and bring the solution just to boil with stirring.
To the boiling solution, add 2 ml of 1% sodium citrate
solution. When the solution became dark red it removed
from heat.
Fourth method: The Au colloidal solution was prepared
by heating 25 ml of potassium bitartrate solution (0.5%
and 1%) with stirring and 25 ml of HAuCl4 solution (1.0
Mm) containing PVP solution (1.5 wt%) was added. The
color of the solution changed to dark purple red after 5
3. Results and Discussion
The formation of gold colloidal nanoparticles can be ob-
served by change in color of the solutions. Potassium bi-
tartrate is a potassium acid salt of tartaric acid, a car-
boxylic acid, it is used for preventing sugar syrups from
crystallizing and for reducing discoloration of boiled ve-
getables [6]. Potassium bitartrate is a weak reductant, re-
lative to sodium citrate. Sodium citrate can be used as a
buffering agent or acid ity regulator, because it resists the
change in pH. When mixing a solution of sodium citrate
with aqueous solution of HAuCl4 the resulting is dark grey
solution within minutes and this indicates a reduction reac-
tion happened. In case of addition of potassium bitartrate
to the solution of HAuCl4, no change in the color of the
resulting solution after an hour of addition and under the
same conditions [7].
In the first experiment when using Potassium bitartra-
teas a reductant and polyethylene glycol as a dispersion,
red wine solution was obtained and remained stable in
normal conditions the particle size was measured it was
between 50 - 200 nanometers as shown in the (Figure 1).
In the second and third methods when using sodium
citrate as a reductant and without dispersion factor, the
color of the resultin g solution d oes not clear th at the go ld
particles is located within the nanoscale. So we did not
measure the particle size, because we know that the color
Copyright © 2012 SciRes. GSC
Copyright © 2012 SciRes. GSC
Figure 1. The range of gold particles size by using atomic
force. (PEG as a protective agent).
Figure 2. The range of gold particles size by using atomic
force. (PVP as a protective agent).
of gold nano p articles is red wine or dark p urple red. As a
result of this experiment shows how important the use of
an appropriate reducing agent and the dispersion factor
for the survival of a stable solution without clustered
Au colloidal solution obtained by the reduction of
HAuCl4with potassium bitartrate is unstable in the absen-
ce of the stabilizer but when the Au nanoparticles pre-
pared by the reduction of HAuCl4 with potassium bitar-
trate in the presence of PVP the solution are stable for a
long peri od.
As for the fourth experiment, we used PVP as a pro-
tective agent also mixed with the reductant first prior to
the reaction will lead to a colloid al gold with dark purple
red color and stable under normal conditions for a long
time. We measured the particles size in this experiment;
it was less than 100 nanometers (Figure 2). It is favor-
ablefor the reductant dispersing in PVP solutions in wa-
ter and interacting with PVP via the intermolecular force
or hydrogen bond. As the amount of PVP increase, which
may hamper the reaction between the reductant and [Au
Cl4] decreasing, and to producing less Au nuclei in a
shorter period, which favors growth of Au nanoparticles,
and the larger Au nanoparticles finally [8].
We speculated that the difference of the results might
be resulted to the different reducing agents used and PVP
and PEG as a protective agent.
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