Colloidal gold is a sol or colloidal suspension of nanoparticles of
gold in a fluid, usually water. The colloid is usually either an
intense red colour (for particles less than 100 nm) or
blue/purple (for larger particles). Due to their optical, electronic,
and molecular-recognition properties, gold nanoparticles are the
subject of substantial research, with many potential or promised
applications. and materials science.
The properties of colloidal gold nanoparticles, and thus their
applications, depend strongly upon their size and shape. For
example, rodlike particles have both transverse and longitudinal
absorption peak, and anisotropy of the shape affects their
2 Physical properties
2.1.1 Effect of size
2.1.2 Effect of local refractive index
2.1.3 Effect of aggregation
3 Medical research
3.1 Electron microscopy
Drug delivery system
3.3 Tumor detection
3.4 Gene therapy
3.5 Photothermal agents
3.6 Radiotherapy dose enhancer
3.7 Detection of toxic gas
Gold nanoparticle based biosensor
3.8.1 Optical biosensor
3.8.2 Electrochemical biosensor
3.9 Thin films
4 Surface chemistry
4.1 Ligand exchange/functionalization
4.2 Ligand removal
4.3 Surface structure and chemical environment
5 Health and safety
5.1 Toxicity and hazards in synthesis
5.2 Toxicity due to capping ligands
5.3 Toxicity due to size of nanoparticles
6.1 Turkevich method
6.2 Brust-Schiffrin method
6.3 Perrault method
6.4 Martin method
6.5 Nanotech applications
6.6 Navarro et al. method
6.8 Block copolymer-mediated method
7 See also
9 Further reading
10 External links
This cranberry glass bowl was made by adding a gold salt (probably
gold chloride) to molten glass.
Used since ancient times, the synthesis of colloidal gold was crucial
to the 4th-century Lycurgus Cup, which changes color depending on the
location of light source. Later it was used as a method of
During the Middle Ages, soluble gold, a solution containing gold salt,
had a reputation for its curative property for various diseases. In
1618, Francis Anthony, a philosopher and member of the medical
profession, published a book called Panacea Aurea, sive tractatus duo
de ipsius Auro Potabili (Latin: gold potion, or two treatments of
potable gold). The book introduces information on the formation of
colloidal gold and its medical uses. About half a century later,
English botanist Nicholas Culpepper published book in 1656, Treatise
of Aurum Potabile, solely discussing the medical uses of colloidal
In 1676, Johann Kunckel, a German chemist, published a book on the
manufacture of stained glass. In his book Valuable Observations or
Remarks About the Fixed and Volatile Salts-Auro and Argento Potabile,
Spiritu Mundi and the Like, Kunckel assumed that the pink color of
Aurum Potabile came from small particles of metallic gold, not visible
to human eyes. In 1842,
John Herschel invented a photographic process
called chrysotype (from the Greek χρῡσός meaning "gold") that
used colloidal gold to record images on paper.
Modern scientific evaluation of colloidal gold did not begin until
Michael Faraday's work in the 1850s. In 1856, in a basement
laboratory of Royal Institution, Faraday accidentally created a ruby
red solution while mounting pieces of gold leaf onto microscope
slides. Since he was already interested in the properties of light
and matter, Faraday further investigated the optical properties of the
colloidal gold. He prepared the first pure sample of colloidal gold,
which he called 'activated gold', in 1857. He used phosphorus to
reduce a solution of gold chloride. The colloidal gold Faraday made
150 years ago is still optically active. For a long time, the
composition of the 'ruby' gold was unclear. Several chemists suspected
it to be a gold tin compound, due to its preparation. Faraday
recognized that the color was actually due to the miniature size of
the gold particles. He noted the light scattering properties of
suspended gold microparticles, which is now called Faraday-Tyndall
Richard Adolf Zsigmondy
Richard Adolf Zsigmondy prepared the first colloidal gold in
diluted solution. Apart from Zsigmondy, Theodor Svedberg, who
invented ultracentrifugation, and Gustav Mie, who provided the theory
for scattering and absorption by spherical particles, were also
interested in the synthesis and properties of colloidal gold.
With advances in various analytical technologies in the 20th century,
studies on gold nanoparticles has accelerated. Advanced microscopy
methods, such as atomic force microscopy and electron microscopy, have
contributed the most to nanoparticle research. Due to their comparably
easy synthesis and high stability, various gold particles have been
studied for their practical uses. Different types of gold nanoparticle
are already used in many industries, such as medicine and electronics.
For example, several FDA-approved nanoparticles are currently used in
Colloidal gold has been used by artists for centuries because of the
nanoparticle’s interactions with visible light.
absorb and scatter light with incredible efficiency. Ranging from
vibrant reds to blues to black and finally to clear and colorless,
colloidal gold has the ability to exhibit a wide range of colors
depending on particle size, shape, local refractive index, and
aggregation state. These colors occur because of a phenomenon called
Localized Surface Plasmon Resonance (LSPR), in which conduction
electrons on the surface of the nanoparticle oscillate in resonance
with incident light.
Effect of size
As a general rule, the wavelength of light absorbed increases as a
function of increasing nano particle size. For example,
pseudo-spherical gold nanoparticles with diameters ~ 30 nm have a
peak LSPR absorption at ~530 nm.
Effect of local refractive index
Changes in the apparent color of a gold nanoparticle solution can also
be caused by the environment in which the colloidal gold is
suspended The optical properties of gold nanoparticles depends
on the refractive index near the nanoparticle surface, therefore both
the molecules directly attached to the nanoparticle surface (i.e.
nanoparticle ligands) and/or the nanoparticle solvent both may
influence observed optical features. As the refractive index near
the gold surface increases, the NP LSPR will shift to longer
wavelengths In addition to solvent environment, the extinction
peak can be tuned by coating the nanoparticles with non-conducting
shells such as silica, bio molecules, or aluminium oxide.
Effect of aggregation
When gold nano particles aggregate, the optical properties of the
particle change, because the effective particle size, shape, and
dielectric environment all change.
This section needs more medical references for verification or relies
too heavily on primary sources. Please review the contents of the
section and add the appropriate references if you can. Unsourced or
poorly sourced material may be challenged and removed. (August 2017)
Main article: Immunogold labelling
Colloidal gold and various derivatives have long been among the most
widely used labels for antigens in biological electron
Colloidal gold particles can be
attached to many traditional biological probes such as antibodies,
lectins, superantigens, glycans, nucleic acids, and receptors.
Particles of different sizes are easily distinguishable in electron
micrographs, allowing simultaneous multiple-labelling experiments.
In addition to biological probes, gold nanoparticles can be
transferred to various mineral substrates, such as mica, single
crystal silicon, and atomically flat gold(III), to be observed under
atomic force microscopy (AFM).
Drug delivery system
Gold nanoparticles can be used to optimize the biodistribution of
drugs to diseased organs, tissues or cells, in order to improve and
target drug delivery. Nanoparticle-mediated drug delivery is
feasible only if the drug distribution is otherwise inadequate. These
cases include drug targeting of unstable (proteins, siRNA, DNA),
delivery to the difficult sites (brain, retina, tumors, intracellular
organelles) and drugs with serious side effects (e.g. anti-cancer
agents). The performance of the nanoparticles depends on the size and
surface functionalities in the particles. Also, the drug release and
particle disintegration can vary depending on the system (e.g.
biodegradable polymers sensitive to pH). An optimal nanodrug delivery
system ensures that the active drug is available at the site of action
for the correct time and duration, and their concentration should be
above the minimal effective concentration (MEC) and below the minimal
toxic concentration (MTC).
Gold nanoparticles are being investigated as carriers for drugs such
as Paclitaxel. The administration of hydrophobic drugs require
molecular encapsulation and it is found that nanosized particles are
particularly efficient in evading the reticuloendothelial system.
In cancer research, colloidal gold can be used to target tumors and
provide detection using SERS (surface enhanced Raman spectroscopy) in
vivo. These gold nanoparticles are surrounded with Raman reporters,
which provide light emission that is over 200 times brighter than
quantum dots. It was found that the Raman reporters were stabilized
when the nanoparticles were encapsulated with a thiol-modified
polyethylene glycol coat. This allows for compatibility and
circulation in vivo. To specifically target tumor cells, the
polyethylenegylated gold particles are conjugated with an antibody (or
an antibody fragment such as scFv), against, e.g. epidermal growth
factor receptor, which is sometimes overexpressed in cells of certain
cancer types. Using SERS, these pegylated gold nanoparticles can then
detect the location of the tumor.
Gold nanoparticles accumulate in tumors, due to the leakiness of tumor
vasculature, and can be used as contrast agents for enhanced imaging
in a time-resolved optical tomography system using short-pulse lasers
for skin cancer detection in mouse model. It is found that
intravenously administrated spherical gold nanoparticles broadened the
temporal profile of reflected optical signals and enhanced the
contrast between surrounding normal tissue and tumors.
Tumor targeting via multifunctional nanocarriers. Cancer cells reduce
adhesion to neighboring cells and migrate into the vasculature-rich
stroma. Once at the vasculature, cells can freely enter the
bloodstream. Once the tumor is directly connected to the main blood
circulation system, multifunctional nanocarriers can interact directly
with cancer cells and effectively target tumors.
Gold nanoparticles have shown potential as intracellular delivery
vehicles for siRNA oligonucleotides with maximal therapeutic impact.
Multifunctional siRNA-gold nanoparticles with several biomolecules:
PEG, cell penetration and cell adhesion peptides and siRNA. Two
different approaches were employed to conjugate the siRNA to the gold
nanoparticle: (1) Covalent approach: use of thiolated siRNA for
gold-thiol binding to the nanoparticle; (2) Ionic approach:
interaction of the negatively charged siRNA to the modified surface of
the AuNP through ionic interactions.
Gold nanoparticles show potential as intracellular delivery vehicles
for antisense oligonucleotides (ssDNA,dsDNA) by providing protection
against intracellular nucleases and ease of functionalization for
Gold nanorods are being investigated as photothermal agents for
Gold nanorods are rod-shaped gold nanoparticles
whose aspect ratios tune the surface plasmon resonance (SPR) band from
the visible to near-infrared wavelength. The total extinction of light
at the SPR is made up of both absorption and scattering. For the
smaller axial diameter nanorods (~10 nm), absorption dominates,
whereas for the larger axial diameter nanorods (>35 nm)
scattering can dominate. As a consequence, for in-vivo applications,
small diameter gold nanorods are being used as photothermal converters
of near-infrared light due to their high absorption
cross-sections. Since near-infrared light transmits readily
through human skin and tissue, these nanorods can be used as ablation
components for cancer, and other targets. When coated with polymers,
gold nanorods have been observed to circulate in-vivo with half-lives
longer than 6 hours, bodily residence times around 72 hours, and
little to no uptake in any internal organs except the liver. Apart
from rod-like gold nanoparticles, also spherical colloidal gold
nanoparticles are recently used as markers in combination with
photothermal single particle microscopy.
Radiotherapy dose enhancer
Considerable interest has been shown in the use of gold and other
heavy-atom-containing nanoparticles to enhance the dose delivered to
tumors. Since the gold nanoparticles are taken up by the tumors
more than the nearby healthy tissue, the dose is selectively enhanced.
The biological effectiveness of this type of therapy seems to be due
to the local deposition of the radiation dose near the
nanoparticles. This mechanism is the same as occurs in heavy ion
Detection of toxic gas
Researchers have developed simple inexpensive methods for on-site
detection of hydrogen sulfide H
2S present in air based on the antiaggregation of gold nanoparticles
(AuNPs). Dissolving H
2S into a weak alkaline buffer solution leads to the formation of HS-,
which can stabilize AuNPs and ensure they maintain their red color
allowing for visual detection of toxic levels of H
Gold nanoparticle based biosensor
Gold nanoparticles are incorporated into biosensors to enhance its
stability, sensitivity, and selectivity.
such as small size, high surface-to-volume ratio, and high surface
energy allow immobilization of large range of biomolecules. Gold
nanoparticle, in particular, could also act as "electron wire" to
transport electrons and its amplification effect on electromagnetic
light allows it to function as signal amplifiers. Main types
of gold nanoparticle based biosensors are optical and electrochemical
Gold nanoparticles improve the sensitivity of optical sensor by
response to the change in local refractive index. The angle of the
incidence light for surface plasmon resonance, an interaction between
light wave and conducting electrons in metal, changes when other
substances are bounded to the metal surface. Because gold is
very sensitive to its surroundings' dielectric constant,
binding of an analyte would significantly shift gold nanoparticle's
SPR and therefore allow more sensitive detection.
could also amplify the SPR signal. When the plasmon wave pass
through the gold nanoparticle, the charge density in the wave and the
electron I the gold interacted and resulted in higher energy response,
so called electron coupling. Since the analyte and bio-receptor
now bind to the gold, it increases the apparent mass of the analyte
and therefore amplified the signal. These properties had been used
DNA sensor with 1000-fold sensitive than without the Au
NP. Humidity senor was also built by altering the atom
interspacing between molecules with humidity change, the interspacing
change would also result in a change of the Au NP's LSPR.
Electrochemical sensor convert biological information into electrical
signals that could be detected. The conductivity and biocompatibility
of Au NP allow it to act as "electron wire". It transfers electron
between the electrode and the active site of the enzyme. It could
be accomplished in two ways: attach the Au NP to either the enzyme or
the electrode. GNP-glucose oxidase monolayer electrode was constructed
use these two methods. The Au NP allowed more freedom in the
enzyme's orientation and therefore more sensitive and stable
detection. Au NP also acts as immobilization platform for the enzyme.
Most biomolecules denatures or lose its activity when interacted with
the electrode. The biocompatibility and high surface energy of Au
allow it to bind to a large amount of protein without altering its
activity and results in a more sensitive sensor. Moreover, Au
NP also catalyzes biological reactions.
under 2 nm has shown catalytic activity to the oxidation of
Gold nanoparticles capped with organic ligands, such as alkanethiol
molecules, can self-assemble into large monolayers (>cm
displaystyle ^ 2
). The particles are first prepared in organic solvent, such as
chloroform or toluene, and are then spread into monolayers either on a
liquid surface or on a solid substrate. Such interfacial thin films of
nanoparticles have close relationship with Langmuir-Blodgett
monolayers made from surfactants.
The mechanical properties of nanoparticle monolayers have been studied
extensively. For 5 nm spheres capped with dodecanethiol, the
Young's modulus of the monolayer is on the order of GPa. The
mechanics of the membranes are guided by strong interactions between
ligand shells on adjacent particles. Upon fracture, the films
crack perpendicular to the direction of strain at a fracture stress of
2.6 MPa, comparable to that of cross-linked polymer films.
Free-standing nanoparticle membranes exhibit bending rigidity on the
order of 10
displaystyle ^ 5
eV, higher than what is predicted in theory for continuum plates of
the same thickness, due to nonlocal microstructural constraints such
as nonlocal coupling of particle rotational degrees of freedom. On
the other hand, resistance to bending is found to be greatly reduced
in nanoparticle monolayers that are supported at the air/water
interface, possibly due to screening of ligand interactions in a wet
In many different types of colloidal gold syntheses, the interface of
the nanoparticles can display widely different character – ranging
from an interface similar to a self-assembled monolayer to a
disordered boundary with no repeating patterns. Beyond the
Au-Ligand interface, conjugation of the interfacial ligands with
various functional moieties (from small organic molecules to polymers
DNA to RNA) afford colloidal gold much of its vast functionality.
After initial nanoparticle synthesis, colloidal gold ligands are often
exchanged with new ligands designed for specific applications. For
example, Au NPs produced via the Turkevich-style (or Citrate
Reduction) method are readily reacted via ligand exchange reactions,
due to the relatively weak binding between the carboxyl groups and the
surfaces of the NPs. This ligand exchange can produce conjugation
with a number of biomolecules from
DNA to RNA to proteins to polymers
(such as PEG) to increase biocompatibility and functionality. For
example, ligands have been shown to enhance catalytic activity by
mediating interactions between adsorbates and the active gold surfaces
for specific oxygenation reactions. Ligand exchange can also be
used to promote phase transfer of the colloidal particles. Ligand
exchange is also possible with alkane thiol-arrested NPs produced from
the Brust-type synthesis method, although higher temperatures are
needed to promote the rate of the ligand detachment. An
alternative method for further functionalization is achieved through
the conjugation of the ligands with other molecules, though this
method can cause the colloidal stability of the Au NPs to
In many cases, as in various high-temperature catalytic applications
of Au, the removal of the capping ligands produces more desirable
physicochemical properties. The removal of ligands from colloidal
gold while maintaining a relatively constant number of Au atoms per Au
NP can be difficult due to the tendency for these bare clusters to
aggregate. The removal of ligands is partially achievable by simply
washing away all excess capping ligands, though this method is
ineffective in removing all capping ligand. More often ligand removal
achieved under high temperature or light ablation followed by washing.
Alternatively, the ligands can be electrochemically etched off.
Surface structure and chemical environment
The precise structure of the ligands on the surface of colloidal gold
NPs impact the properties of the colloidal gold particles. Binding
conformations and surface packing of the capping ligands at the
surface of the colloidal gold NPs tend to differ greatly from bulk
surface model adsorption, largely due to the high curvature observed
at the nanoparticle surfaces. Thiolate-gold interfaces at the
nanoscale have been well-studied and the thiolate ligands are observed
to pull Au atoms off of the surface of the particles to for
“staple” motifs that have significant Thiyl-Au(0)
character. The citrate-gold surface, on the other hand, is
relatively less-studied due to the vast number of binding
conformations of the citrate to the curved gold surfaces. A study
performed in 2014 identified that the most-preferred binding of the
citrate involves two carboxylic acids and the hydroxyl group of the
citrate binds three surface metal atoms.
Health and safety
Health and safety hazards of nanomaterials
Health and safety hazards of nanomaterials and
As gold nanoparticles (AuNPs) are further investigated for targeted
drug delivery in humans, their toxicity needs to be considered. For
the most part, it is suggested that AuNPs are biocompatible,[citation
needed] but it is important to ask at what concentration they would be
toxic, and if that concentration falls within the range of used
concentrations. Toxicity can be tested in vitro and in vivo. In vitro
toxicity results can vary depending on the type of the cellular growth
media with different protein compositions, the method used to
determine cellular toxicity (cell health, cell stress, how many cells
are taken into a cell), and the capping ligands in solution. In
vivo assessments can determine the general health of an organism
(abnormal behavior, weight loss, average life span) as well as tissue
specific toxicology (kidney, liver, blood) and inflammation and
In vitro experiments are more popular than in
vivo experiments because in vitro experiments are more simplistic to
perform than in vivo experiments.
Toxicity and hazards in synthesis
While AuNPs themselves appear to have low or negligible
toxicity, and the literature shows that the toxicity
has much more to do with the ligands rather than the particles
themselves, the synthesis of them involves chemicals that are
hazardous. Sodium borohydride, a harsh reagent, is used to reduce the
gold ions to gold metal. The gold ions usually come from
chloroauric acid, a potent acid. Because of the high toxicity and
hazard of reagents used to synthesize AuNPs, the need for more
“green” methods of synthesis arose.
Toxicity due to capping ligands
Some of the capping ligands associated with AuNPs can be toxic while
others are nontoxic. In gold nanorods (AuNRs), it has been shown that
a strong cytotoxicity was associated with CTAB-stabilized AuNRs at low
concentration, but it is thought that free CTAB was the culprit in
toxicity . Modifications that overcoat these AuNRs reduces
this toxicity in human colon cancer cells (HT-29) by preventing CTAB
molecules from desorbing from the AuNRs back into the solution.
Ligand toxicity can also be seen in AuNPs. Compared to the 90%
toxicity of HAuCl4 at the same concentration, AuNPs with carboxylate
termini were shown to be non-toxic. Large AuNPs conjugated with
biotin, cysteine, citrate, and glucose were not toxic in human
leukemia cells (K562) for concentrations up to 0.25 M. Also,
citrate-capped gold nanospheres (AuNSs) have been proven to be
compatible with human blood and did not cause platelet aggregation or
an immune response. However, citrate-capped gold nanoparticles
sizes 8-37 nm were found to be lethally toxic for mice, causing
shorter lifespans, severe sickness, loss of appetite and weight, hair
discoloration, and damage to the liver, spleen, and lungs; gold
nanoparticles accumulated in the spleen and liver after traveling a
section of the immune system. There are mixed-views for
polyethylene glycol (PEG)-modified AuNPs. These AuNPs were found to be
toxic in mouse liver by injection, causing cell death and minor
inflammation. However, AuNPs conjugated with PEG copolymers showed
negligible toxicity towards human colon cells (Caco-2). AuNP
toxicity also depends on the overall charge of the ligands. In certain
doses, AuNSs that have positively-charged ligands are toxic in monkey
kidney cells (Cos-1), human red blood cells, and E. coli because of
the AuNSs interaction with the negatively-charged cell membrane; AuNSs
with negatively-charged ligands have been found to be nontoxic in
these species. In addition to the previously mentioned in vivo and
in vitro experiments, other similar experiments have been performed.
Alkylthiolate-AuNPs with trimethlyammonium ligand termini mediate the
DNA across mammalian cell membranes in vitro at a
high level, which is detrimental to these cells. Corneal haze in
rabbits have been healed in vivo by using polyethylemnimine-capped
gold nanoparticles that were transfected with a gene that promotes
wound healing and inhibits corneal fibrosis.
Toxicity due to size of nanoparticles
Toxicity in certain systems can also be dependent on the size of the
nanoparticle. AuNSs size 1.4 nm were found to be toxic in human
skin cancer cells (SK-Mel-28), human cervical cancer cells (HeLa),
mouse fibroblast cells (L929), and mouse macrophages (J774A.1), while
0.8, 1.2, and 1.8 nm sized AuNSs were less toxic by a six-fold
amount and 15 nm AuNSs were nontoxic. There is some evidence
for AuNP buildup after injection in in vivo studies, but this is very
size dependent. 1.8 nm AuNPs were found to be almost totally
trapped in the lungs of rats. Different sized AuNPs were found to
buildup in the blood, brain, stomach, pancreas,
kidneys, liver, and spleen.
Potential difference as a function of distance from particle surface.
Generally, gold nanoparticles are produced in a liquid ("liquid
chemical methods") by reduction of chloroauric acid (H[AuCl4]). After
dissolving H[AuCl4], the solution is rapidly stirred while a reducing
agent is added. This causes Au3+ ions to be reduced to Au+ions. Then a
disproportionation reaction occurs whereby 3 Au+ ions give rise to
Au3+ and 2 Au0 atoms. The Au0 atoms act as center of nucleation around
which further Au+ ions gets reduced. To prevent the particles from
aggregating, some sort of stabilizing agent that sticks to the
nanoparticle surface is usually added. In the Turkevich method of Au
NP synthesis, citrate initially acts as the reducing agent and finally
as the capping agent which stabilizes the Au NP through electrostatic
interactions between the lone pair of electrons on the oxygen and the
They can be functionalized with various organic ligands to create
organic-inorganic hybrids with advanced functionality.
The method pioneered by J. Turkevich et al. in 1951 and
refined by G. Frens in the 1970s, is the simplest one
available. In general, it is used to produce modestly monodisperse
spherical gold nanoparticles suspended in water of around
10–20 nm in diameter. Larger particles can be produced, but
this comes at the cost of monodispersity and shape. It involves the
reaction of small amounts of hot chloroauric acid with small amounts
of sodium citrate solution. The colloidal gold will form because the
citrate ions act as both a reducing agent and a capping agent. A
capping agent is used in nanoparticle synthesis to stop particle
growth and aggregation. A good capping agent has a high affinity for
the new nuclei so it will bind to surface atoms which stabilizes the
surface energy of the new nuclei and makes so that they cannot bind to
Recently, the evolution of the spherical gold nanoparticles in the
Turkevich reaction has been elucidated. It is interesting to note that
extensive networks of gold nanowires are formed as a transient
intermediate. These gold nanowires are responsible for the dark
appearance of the reaction solution before it turns ruby-red.
To produce larger particles, less sodium citrate should be added
(possibly down to 0.05%, after which there simply would not be enough
to reduce all the gold). The reduction in the amount of sodium citrate
will reduce the amount of the citrate ions available for stabilizing
the particles, and this will cause the small particles to aggregate
into bigger ones (until the total surface area of all particles
becomes small enough to be covered by the existing citrate ions).
This method was discovered by Brust and Schiffrin in the early
1990s, and can be used to produce gold nanoparticles in organic
liquids that are normally not miscible with water (like toluene). It
involves the reaction of a chlorauric acid solution with
tetraoctylammonium bromide (TOAB) solution in toluene and sodium
borohydride as an anti-coagulant and a reducing agent, respectively.
Here, the gold nanoparticles will be around 5–6 nm. NaBH4
is the reducing agent, and TOAB is both the phase transfer catalyst
and the stabilizing agent.
It is important to note that TOAB does not bind to the gold
nanoparticles particularly strongly, so the solution will aggregate
gradually over the course of approximately two weeks. To prevent this,
one can add a stronger binding agent, like a thiol (in particular,
alkanethiols), which will bind to gold, producing a near-permanent
Alkanethiol protected gold nanoparticles can be
precipitated and then redissolved. Thiols are better binding agents
because there is a strong affinity for the gold-sulfur bonds that form
when the two substances react with each other. Tetra-dodecanthiol
is a commonly used strong binding agent to synthesize smaller
particles. Some of the phase transfer agent may remain bound to
the purified nanoparticles, this may affect physical properties such
as solubility. In order to remove as much of this agent as possible,
the nanoparticles must be further purified by soxhlet extraction.
This approach, discovered by Perrault and Chan in 2009, uses
hydroquinone to reduce HAuCl4 in an aqueous solution that contains
15 nm gold nanoparticle seeds. This seed-based method of
synthesis is similar to that used in photographic film development, in
which silver grains within the film grow through addition of reduced
silver onto their surface. Likewise, gold nanoparticles can act in
conjunction with hydroquinone to catalyze reduction of ionic gold onto
their surface. The presence of a stabilizer such as citrate results in
controlled deposition of gold atoms onto the particles, and growth.
Typically, the nanoparticle seeds are produced using the citrate
method. The hydroquinone method complements that of Frens, as
it extends the range of monodispersed spherical particle sizes that
can be produced. Whereas the Frens method is ideal for particles of
12–20 nm, the hydroquinone method can produce particles of at
least 30–300 nm.
This simple method, discovered by Martin and Eah in 2010,
generates nearly monodisperse "naked" gold nanoparticles in water.
Precisely controlling the reduction stoichiometry by adjusting the
ratio of NaBH4-NaOH ions to HAuCl4-HCl ions within the "sweet zone,"
along with heating, enables reproducible diameter tuning between
3–6 nm. The aqueous particles are colloidally stable due to
their high charge from the excess ions in solution. These particles
can be coated with various hydrophilic functionalities, or mixed with
hydrophobic molecules for applications in non-polar solvents. In
non-polar solvents the nanoparticles remain highly charged, and
self-assemble on liquid droplets to form 2D monolayer films of
Bacillus licheniformis can be used in synthesis of gold nanocubes with
sizes between 10 and 100 nanometres.
Gold nanoparticles are
usually synthesized at high temperatures in organic solvents or using
toxic reagents. The bacteria produce them in much milder conditions.
Navarro et al. method
The precise control of particle size with a low polydispersity of
spherical gold nanoparticles remains difficult for particles larger
than 30 nm. In order to provide maximum control on the NP
structure, Navarro and co-workers used a modified Turkevitch-Frens
procedure using sodium acetylacetonate Na(acac) as the reducing agent
and sodium citrate as the stabilizer.
Another method for the experimental generation of gold particles is by
sonolysis. The first method of this type was invented by Baigent and
Müller. This work pioneered the use of ultrasound to provide the
energy for the processes involved and allowed the creation of gold
particles with a diameter of under 10 nm. In another method using
ultrasound, the reaction of an aqueous solution of HAuCl4 with
glucose, the reducing agents are hydroxyl radicals and sugar
pyrolysis radicals (forming at the interfacial region between the
collapsing cavities and the bulk water) and the morphology obtained is
that of nanoribbons with width 30–50 nm and length of several
micrometers. These ribbons are very flexible and can bend with angles
larger than 90°. When glucose is replaced by cyclodextrin (a glucose
oligomer), only spherical gold particles are obtained, suggesting that
glucose is essential in directing the morphology toward a ribbon.
Block copolymer-mediated method
An economical, environmentally benign and fast synthesis methodology
for gold nanoparticles using block copolymer has been developed by
Sakai et al. In this synthesis methodology, block copolymer plays
the dual role of a reducing agent as well as a stabilizing agent. The
formation of gold nanoparticles comprises three main steps: reduction
of gold salt ion by block copolymers in the solution and formation of
gold clusters, adsorption of block copolymers on gold clusters and
further reduction of gold salt ions on the surfaces of these gold
clusters for the growth of gold particles in steps, and finally its
stabilization by block copolymers. But this method usually has a
limited-yield (nanoparticle concentration), which does not increase
with the increase in the gold salt concentration. Recently, Ray et al.
demonstrated that the presence of an additional reductant (trisodium
citrate) in 1:1 mole ratio with gold salt enhances the yield by
manyfold at ambient conditions and room temperature.
Gold nanoparticles in chemotherapy
^ Xuan Yang, Miaoxin Yang, Bo Pang, Madeline Vara, Younan Xia (2015).
Nanomaterials at Work in Biomedicine". Chem. Rev. 115:
10410–10488. doi:10.1021/acs.chemrev.5b00193. CS1 maint: Uses
authors parameter (link)
^ Paul Mulvaney, University of Melbourne, The beauty and elegance of
Nanocrystals, Use since Roman times Archived 2004-10-28 at the Wayback
^ C. N. Ramachandra Rao, Giridhar U. Kulkarni, P. John Thomasa, Peter
P. Edwards, Metal nanoparticles and their assemblies, Chem. Soc. Rev.,
2000, 29, 27–35. (on-line here; mentions Cassius and Kunchel)
^ S.Zeng; Yong, Ken-Tye; Roy, Indrajit; Dinh, Xuan-Quyen; Yu, Xia;
Luan, Feng; et al. (2011). "A review on functionalized gold
nanoparticles for biosensing applications" (PDF). Plasmonics. 6 (3):
^ a b Sharma, Vivek; Park, Kyoungweon; Srinivasarao, Mohan (2009).
"Colloidal dispersion of gold nanorods: Historical background, optical
properties, seed-mediated synthesis, shape separation and
self-assembly". Material Science and Engineering Reports. 65 (1–3):
^ "The Lycurgus Cup". British Museum. Retrieved 2015-12-04.
^ Freestone, Ian; Meeks, Nigel; Sax, Margaret; Higgitt, Catherine
Lycurgus Cup — A Roman nanotechnology".
40 (4): 270–277. doi:10.1007/BF03215599. ISSN 0017-1557.
^ Antonii, Francisci (1618). Panacea aurea sive Tractatus duo de
ipsius auro potabili. Ex Bibliopolio Frobeniano.
^ Culpeper, Nicholas (1657). Mr. Culpepper's Treatise of aurum
potabile Being a description of the three-fold world, viz. elementary
celestial intellectual containing the knowledge necessary to the study
of hermetick philosophy. Faithfully written by him in his life-time,
and since his death, published by his wife. London.
^ Kunckel von Löwenstern, Johann (1678). Utiles observationes sive
animadversiones de salibus fixis et volatilibus, auro et argento
potabili (etc.). Austria: Wilson.
^ a b V. R. Reddy, "
Gold Nanoparticles: Synthesis and Applications"
2006, 1791, and references therein
^ Michael Faraday, Philosophical Transactions of the Royal Society,
^ "Michael Faraday's gold colloids The Royal Institution: Science
Lives Here". www.rigb.org. Retrieved 2015-12-04.
^ Gay-Lussac (1832). "Ueber den Cassius'schen Goldpurpur". Annalen der
Physik. 101 (8): 629–630. Bibcode:1832AnP...101..629G.
^ Berzelius, J. J. (1831). "Ueber den Cassius' schen Goldpurpur".
Annalen der Physik. 98 (6): 306–308. Bibcode:1831AnP....98..306B.
^ Faraday, M. (1857). "Experimental Relations of
Gold (and Other
Metals) to Light,". Philosophical Transactions of the Royal Society.
147: 145. doi:10.1098/rstl.1857.0011.
^ Zsigmondy, Richard (December 11, 1926). "Properties of colloids"
(PDF). Nobel Foundation. Retrieved 2009-01-23.
^ Zeng, Shuwen; Yu, Xia; Law, Wing-Cheung; Zhang, Yating; Hu, Rui;
Dinh, Xuan-Quyen; Ho, Ho-Pui; Yong, Ken-Tye (2013). "Size dependence
of Au NP-enhanced surface plasmon resonance based on differential
phase measurement". Sensors and Actuators B: Chemical. 176: 1128.
^ Hurst, Sarah J., ed. (2011-01-01).
Nanoparticle Therapeutics: FDA
Approval, Clinical Trials, Regulatory Pathways, and Case Study -
Springer. Methods in Molecular Biology. Humana Press.
doi:10.1007/978-1-61779-052-2_21. ISBN 978-1-61779-051-5.
^ Anderson, Michele L.; Morris, Catherine A.; Stroud, Rhonda M.;
Merzbacher, Celia I.; Rolison, Debra R. (1999-02-01). "Colloidal Gold
Aerogels: Preparation, Properties, and Characterization". Langmuir.
15 (3): 674–681. doi:10.1021/la980784i. ISSN 0743-7463.
^ a b Link, Stephan; El-Sayed, Mostafa A. (1999-05-01). "Size and
Temperature Dependence of the Plasmon Absorption of Colloidal Gold
Nanoparticles". The Journal of Physical Chemistry B. 103 (21):
4212–4217. doi:10.1021/jp984796o. ISSN 1520-6106.
^ a b Ghosh, Sujit Kumar; Nath, Sudip; Kundu, Subrata; Esumi, Kunio;
Pal, Tarasankar (2004-09-01). "
Solvent and Ligand Effects on the
Localized Surface Plasmon Resonance (LSPR) of
Gold Colloids". The
Journal of Physical Chemistry B. 108 (37): 13963–13971.
doi:10.1021/jp047021q. ISSN 1520-6106.
^ a b Underwood, Sylvia; Mulvaney, Paul (1994-10-01). "Effect of the
Solution Refractive Index on the Color of
Gold Colloids". Langmuir. 10
(10): 3427–3430. doi:10.1021/la00022a011. ISSN 0743-7463.
^ Xing, Shuangxi; Tan, Li Huey; Yang, Miaoxin; Pan, Ming; Lv, Yunbo;
Tang, Qinghu; Yang, Yanhui; Chen, Hongyu (2009-05-12). "Highly
controlled core/shell structures: tunable conductive polymer shells on
gold nanoparticles and nanochains". Journal of Materials Chemistry. 19
(20): 3286. doi:10.1039/b900993k. ISSN 1364-5501.
^ Ghosh, Sujit Kumar; Pal, Tarasankar (2007-11-01). "Interparticle
Coupling Effect on the Surface Plasmon Resonance of Gold
Nanoparticles: From Theory to Applications". Chemical Reviews. 107
(11): 4797–4862. doi:10.1021/cr0680282. ISSN 0009-2665.
^ Horisberger; Rosset, J (4 January 1977). "Colloidal gold, a useful
marker for transmission and scanning electron microscopy". Journal of
Histochemistry and Cytochemistry. 25 (4): 295–305.
^ Electron Microscopy, 2nd Edition, by John J. Bozzola, Jones &
Bartlett Publishers; 2 Sub edition (October 1998)
^ Practical Electron Microscopy: A Beginner's Illustrated Guide, by
Elaine Evelyn Hunter. Cambridge University Press; 2nd edition
(September 24, 1993) ISBN 0-521-38539-3
^ Electron Microscopy: Methods and Protocols (Methods in Molecular
Biology), by John Kuo (Editor). Humana Press; 2nd edition (February
27, 2007) ISBN 1-58829-573-7
^ Romano, Egidio L (1977). "Staphylococcal protein a bound to
colloidal gold: A useful reagent to label antigen-antibody sites in
electron microscopy". Immunochemistry. 14: 711–715.
^ Simultaneous visualization of chromosome bands and hybridization
signal using colloidal-gold labeling in electron microscopy 
^ Double labeling with colloidal gold particles of different sizes
^ Grobelny, Jaroslaw, et al. "Size Measurement of
Atomic Force Microscopy." Characterization of
for Drug Delivery.Springer, 2011. 71–82. Print.
^ Han, G; Ghosh, P; Rotello, VM (2007). "Functionalized gold
nanoparticles for drug delivery". Nanomedicine (Lond). 2: 113–123.
^ Han, G; Ghosh, P; Rotello, VM (2007). "Multi-functional gold
nanoparticles for drug delivery". Adv Exp Med Biol. 620:
^ Langer, R (2000). "Biomaterials in drug delivery and tissue
engineering: one laboratory's experience". Acc Chem Res. 33: 94–101.
^ Gibson, Jacob D. (2007). "Paclitaxel-Functionalized Gold
Nanoparticles". Journal of the American Chemical Society. 129:
^ Qian, Ximei.
In vivo tumor targeting and spectroscopic detection
with surface-enhanced Raman nanoparticle tags. Nature Biotechnology.
2008. Vol 26 No 1.
^ Sajjadi, AY; Suratkar, AA; Mitra, KK; Grace, MS (2012). "Short-Pulse
Laser-Based System for Detection of Tumors: Administration of Gold
Nanoparticles Enhances Contrast". J. Nanotechnol. Eng. Med. 3 (2):
^ Giljohann DA, Seferos DS, Prigodich AE, Patel PC, Mirkin CA. Gene
regulation with polyvalent siRNA-nanoparticle conjugates. J Am Chem
^ Mackey, Megan A.; Ali, Moustafa R. K.; Austin, Lauren A.; Near,
Rachel D.; El-Sayed, Mostafa A. (2014-02-06). "The Most Effective Gold
Nanorod Size for Plasmonic Photothermal Therapy: Theory and In Vitro
Experiments". The Journal of Physical Chemistry B. 118 (5):
1319–1326. doi:10.1021/jp409298f. ISSN 1520-6106.
PMC 3983380 . PMID 24433049.
^ Niidome, Takuro; Yamagata, Masato; Okamoto, Yuri; Akiyama, Yasuyuki;
Takahashi, Hironobu; Kawano, Takahito; Katayama, Yoshiki; Niidome,
Yasuro (2006-09-12). "PEG-modified gold nanorods with a stealth
character for in vivo applications". Journal of Controlled Release.
114 (3): 343–347. doi:10.1016/j.jconrel.2006.06.017.
^ Hainfeld, James et al. "The use of gold nanoparticles to enhance
radiotherapy in mice." Phys. Med. Biol. 2004. Vol 49, N309–315
^ McMahon, Stephen et al. "Biological consequences of nanoscale energy
deposition near irradiated heavy atom nanoparticles." Nature
^ Zhang, Zhiyang; Zhaopeng Chen; Shasha Wang; Chengli Qu; Lingxin Chen
(2014). "On-site Visual Detection of Hydrogen Sulfide in Air Based on
Enhancing the Stability of
Gold NanoParticles". ACS Applied Materials
& Interfaces. 6 (9): 6300–6307. doi:10.1021/am500564w.
^ a b c d e Xu, S. et. al.
Gold nanoparticle-based biosensors. Gold
Bulletin. 2010, 43, p 29–41.
^ Wang, J.; Polsky, R.; Xu, D. (2001). "Silver-Enhanced Colloidal Gold
Electrochemical Stripping Detection of
DNA Hybridization". Langmuir.
17: 5739. doi:10.1021/la011002f.
^ Wang, J.; Xu, D.; Polsky, R. (2002). "Magnetically-Induced
Solid-State Electrochemical Detection of
DNA Hybridization". J Am Chem
Soc. 124: 4028. doi:10.1021/ja0255709.
^ Daniel, M. C.; Astruc, D. (2004). "
Gold Nanoparticles: Assembly,
Supramolecular Chemistry, Quantum-Size-Related Properties, and
Applications toward Biology, Catalysis, and Nanotechnology". Chem Rev.
104: 293. doi:10.1021/cr030698+.
^ Hu, M.; Chen, J.; Li, Z.Y.; Au, L.; Hartland, G.V.; Li, X.; Marquez,
M.; Xia, Y. (2006). "
Gold nanostructures: engineering their plasmonic
properties for biomedical applications". Chem Soc Rev. 35: 1084.
^ Link, S.; El-Sayed, M.A. (1996). "Spectral Properties and Relaxation
Dynamics of Surface Plasmon Electronic Oscillations in
Gold and Silver
Nanodots and Nanorods". J. Phys. Chem. B. 103: 8410.
^ Mulvaney, P. (1996). "Surface Plasmon Spectroscopy of Nanosized
Metal Particles". Langmuir. 12: 788. doi:10.1021/la9502711.
^ Lin, H. Y.; Chen, Y. C. (2006). "Detection of Phosphopeptides by
Localized Surface Plasma Resonance of Titania-Coated Gold
Nanoparticles Immobilized on Glass Substrates". Anal Chem. 78: 6873.
^ He, L.; Musick, M.D.; Nicewarner, S. R.; Salinas, F.G. (2000).
"Colloidal Au-Enhanced Surface Plasmon Resonance for Ultrasensitive
DNA Hybridization". Journal of the American Chemical
Society. 122: 9071. doi:10.1021/ja001215b.
^ Okamoto, Takayuki; Yamaguchi, Ichirou; Kobayashi, Tetsushi (2000).
"Local plasmon sensor with gold colloid monolayers deposited upon
glass substrates". Opt Lett. 25: 372. Bibcode:2000OptL...25..372O.
^ Brown, K.R.; Fox, P; Natan, M.J. (1996). "Morphology-Dependent
Electrochemistry of Cytochromecat Au Colloid-Modified SnO2Electrodes".
Journal of the American Chemical Society. 118: 1154.
^ Xiao, Y.; et al. (2003). ""Plugging into Enzymes": Nanowiring of
Redox Enzymes by a
Gold Nanoparticle". Science. 299: 1877.
Bibcode:2003Sci...299.1877X. doi:10.1126/science.1080664. CS1
maint: Explicit use of et al. (link)
^ Gole, A.; et al. (2001). "Pepsin−
Gold Colloid Conjugates:
Preparation, Characterization, and Enzymatic Activity". Langmuir. 17:
1674. doi:10.1021/la001164w. CS1 maint: Explicit use of et al.
^ Gole, A.; et al. (2002). "Studies on the formation of bioconjugates
of Endoglucanase with colloidal gold". Colloids and Surfaces B:
Biointerfaces. 25: 129. doi:10.1016/s0927-7765(01)00301-0. CS1
maint: Explicit use of et al. (link)
^ Valden, M.; Lai, X.; Goodman, D.W. (1998). "Onset of Catalytic
Gold Clusters on Titania with the Appearance of
Nonmetallic Properties". Science. 281: 1647.
^ Lou, Y.; Maye, M.M.; Han, L.; Zhong, C. -J. (2001). "Gold–platinum
alloy nanoparticle assembly as catalyst for methanol
electrooxidation". Chemical Communications. 2001: 473.
^ Turner, M.; Golovko, V.B.; Vaughan, O.P; Abdulkin, P.;
Berenguer-Murcia, A.; Tikhov, M.S.; Johnson, B.F.; Lambert, R.M
(2008). "Selective oxidation with dioxygen by gold nanoparticle
catalysts derived from 55-atom clusters". Nature. 454: 981.
^ Mueggenburg, K.; et al. (2007). "Elastic Membranes of Close-Packed
Nanoparticle Arrays". Nature Materials. 6: 666–670. CS1 maint:
Explicit use of et al. (link)
^ He, J.; et al. (2010). "Fabrication and Mechanical Properties of
Nanoparticle Membranes". Small. 6:
1449–1456. doi:10.1002/smll.201000114. CS1 maint: Explicit use
of et al. (link)
^ Wang, Y.; et al. (2014). "Fracture and Failure of Nanoparticle
Monolayers and Multilayers". Nano Letters. 14: 826–830.
Bibcode:2014NanoL..14..826W. doi:10.1021/nl404185b. CS1 maint:
Explicit use of et al. (link)
^ Wang, Y.; et al. (2015). "Strong Resistance to Bending Observed for
Nanoparticle Monolayers". Nano Letters. 15: 6732–6737.
doi:10.1021/acs.nanolett.5b02587. CS1 maint: Explicit use of et
^ Griesemer, S. et al. The Role of Ligands in the Mechanical
Properties of Langmuir
Nanoparticle Films. Soft Matter 2017, 13,
^ a b c Sperling, R. A.; Parak, W. J. (2010-03-28). "Surface
modification, functionalization and bioconjugation of colloidal
inorganic nanoparticles". Philosophical Transactions of the Royal
Society of London A: Mathematical, Physical and Engineering Sciences.
368 (1915): 1333–1383. Bibcode:2010RSPTA.368.1333S.
doi:10.1098/rsta.2009.0273. ISSN 1364-503X.
^ Tauran, Yannick; Brioude, Arnaud; Coleman, Anthony W; Rhimi, Moez;
Kim, Beonjoom (2013-08-26). "Molecular recognition by gold, silver and
copper nanoparticles". World Journal of Biological Chemistry. 4 (3):
35–63. doi:10.4331/wjbc.v4.i3.35. ISSN 1949-8454.
PMC 3746278 . PMID 23977421.
^ Taguchi, Tomoya; Isozaki, Katsuhiro; Miki, Kazushi (2012-12-18).
"Enhanced Catalytic Activity of Self-Assembled-Monolayer-Capped Gold
Nanoparticles". Advanced Materials. 24 (48): 6462–6467.
doi:10.1002/adma.201202979. ISSN 1521-4095.
^ Heinecke, Christine L.; Ni, Thomas W.; Malola, Sami; Mäkinen,
Ville; Wong, O. Andrea; Häkkinen, Hannu; Ackerson, Christopher J.
(2012-08-15). "Structural and Theoretical Basis for Ligand Exchange on
Thiolate Monolayer Protected
Gold Nanoclusters". Journal of the
American Chemical Society. 134 (32): 13316–13322.
doi:10.1021/ja3032339. ISSN 0002-7863. PMC 4624284 .
^ Perumal, Suguna; Hofmann, Andreas; Scholz, Norman; Rühl, Eckart;
Graf, Christina (2011-04-19). "Kinetics Study of the Binding of
Multivalent Ligands on Size-Selected
Gold Nanoparticles". Langmuir. 27
(8): 4456–4464. doi:10.1021/la105134m. ISSN 0743-7463.
^ McMahon, Jeffrey M.; Emory, Steven R. (2007-01-01). "Phase Transfer
Nanoparticles to Organic Solvents with Increased
Stability". Langmuir. 23 (3): 1414–1418. doi:10.1021/la0617560.
^ Tyo, Eric C.; Vajda, Stefan (2015). "
Catalysis by clusters with
precise numbers of atoms". Nature Nanotechnology. 10 (7): 577–588.
^ Niu, Zhiqiang; Li, Yadong (2014-01-14). "Removal and Utilization of
Capping Agents in Nanocatalysis". Chemistry of Materials. 26 (1):
72–83. doi:10.1021/cm4022479. ISSN 0897-4756.
^ a b Häkkinen, Hannu; Walter, Michael; Grönbeck, Henrik
(2006-05-01). "Divide and Protect: Capping
Gold Nanoclusters with
Molecular Gold−Thiolate Rings". The Journal of Physical Chemistry B.
110 (20): 9927–9931. doi:10.1021/jp0619787.
^ Reimers, Jeffrey R.; Ford, Michael J.; Halder, Arnab; Ulstrup, Jens;
Hush, Noel S. (2016-03-15). "
Gold surfaces and nanoparticles are
protected by Au(0)–thiyl species and are destroyed when
Au(I)–thiolates form". Proceedings of the National Academy of
Sciences. 113 (11): E1424–E1433. Bibcode:2016PNAS..113E1424R.
doi:10.1073/pnas.1600472113. ISSN 0027-8424. PMC 4801306 .
^ Park, Jong-Won; Shumaker-Parry, Jennifer S. (2014-02-05).
"Structural Study of Citrate Layers on
Gold Nanoparticles: Role of
Intermolecular Interactions in Stabilizing Nanoparticles". Journal of
the American Chemical Society. 136 (5): 1907–1921.
doi:10.1021/ja4097384. ISSN 0002-7863.
^ a b c Alkilany, A. M.; Murphy, C.J . (September 2010). "Toxicity and
cellular uptake of gold nanoparticles: what we have learned so far?".
Nanoparticle Research. 12 (7): 2313–2333.
^ Rama, S.; Perala, K.; Kumar, S. (July 2013). "On the Mechanism of
Nanoparticle Synthesis in the Brust-Schiffrin Method". Langmuir.
29 (31): 9863–73. doi:10.1021/la401604q.
^ Murphy, C.J.; et., al. (March 2009). "Cellular uptake and
cytotoxicity of gold nanorods: molecular origin of cytotoxicity and
surface effects". Small. 5 (6): 701–708.
^ a b Murphy, C.J.; et., al. (March 2009). "Cellular uptake and
cytotoxicity of gold nanorods: molecular origin of cytotoxicity and
surface effects". Small. 5 (6): 701–708.
^ Takahashi, H.; et., al. (January 2006). "Modification of gold
nanorods using phosphatidylcholine to reduce cytotoxicity". Langmuir.
22 (1): 2–5. doi:10.1021/la0520029.
^ a b Rotello, V.M.; et., al. (June 2004). "Toxicity of Gold
Nanoparticles Functionalized with Cationic and Anionic Side Chains".
Bioconjugate Chemistry. 15 (4): 897–900.
^ Murphy, C.J.; et., al. (January 2005). "
Nanoparticles Are Taken
Up by Human Cells but Do Not Cause Acute Cytotoxicity". Small. 1 (3):
^ McNeil, S.E.; et., al. (June 2009). "Interaction of colloidal gold
nanoparticles with human blood: effects on particle size and analysis
of plasma protein binding profiles". Nanomedicine: Nanotechnology,
Biology and Medicine. 5 (2): 106–117.
^ Chen, Y.S.; et., al. (May 2009). "Assessment of the In Vivo Toxicity
Gold Nanoparticles". Nanoscale Research Letters. 4 (8): 858–864.
^ Jeong, J.; et., al. (April 2009). "Acute toxicity and
pharmacokinetics of 13 nm-sized PEG-coated gold nanoparticles".
Toxicology and Applied Pharmacology. 236 (1): 16–24.
^ Gref, R.; et., al. (November 2003). "Surface-engineered
nanoparticles for multiple ligand coupling". Biomaterials. 24 (24):
^ Astruc, D.; Boisselier, E. (April 2009). "
Gold nanoparticles in
nanomedicine: preparations, imaging, diagnostics, therapies and
toxicity". Chemical Society Reviews. 38 (6): 1759–1782.
^ Mohan, R.R.; et., al. (June 2013). "BMP7 Gene Transfer via Gold
Nanoparticles into Stroma Inhibits Corneal
Fibrosis In Vivo". PLOS
ONE. 8 (6): 1–9. Bibcode:2013PLoSO...866434T.
^ Goodman, C.M.; McCusker, C.D.; Yilmaz, T.; Rotello, V.M. (June
2004). "Toxicity of
Nanoparticles Functionalized with Cationic
and Anionic Side Chains". Bioconjugate Chemistry. 15 (4): 897–900.
^ Gratton, S. E. A.; Polhaus, P. D.; et. al (June 2007).
"Nanofabricated particles for engineered drug therapies: A preliminary
biodistribution study of PRINT™ nanoparticles". J. Control Release.
121 (1–2): 10–18. doi:10.1016/j.jconrel.2007.05.027.
^ a b c d e f g Sonavane, G.; Tomoda, K.; Makino, K. (October 2008).
"Biodistribution of colloidal gold nanoparticles after intravenous
administration: effect of particle size". Colloids Surf. 66 (2):
^ a b c De Jong, W. H.; Hagens, W.I.; et. al. (April 2008). "Particle
size-dependent organ distribution of gold nanoparticles after
intravenous administration". Biomaterials. 29 (12): 1912–1919.
^ Turkevich, J.; Stevenson, P. C.; Hillier, J. (1951). "A study of the
nucleation and growth processes in the synthesis of colloidal gold".
Discuss. Faraday. Soc. 11: 55–75. doi:10.1039/df9511100055.
^ Kimling, J.; Maier, M.; Okenve, B.; Kotaidis, V.; Ballot, H.; Plech,
A. (2006). "Turkevich Method for
Revisited". J. Phys. Chem. B. 110: 15700–15707.
^ a b Frens, G. (1972). "Particle size and sol stability in metal
colloids". Colloid & Polymer Science. 250: 736–741.
^ a b Frens, G. (1973). "Controlled nucleation for the regulation of
the particle size in monodisperse gold suspensions". Nature. 241:
^ Niu, Zhiqiang; Li, Yadong (2014). "Removal and Utilization of
Capping Agents in Nanocatalysis". Chemistry of Materials. 26: 72–83.
^ Pong, B.-K.; Elim, H. I.; Chong, J.-X.; Trout, B. L.; Lee, J.-Y.
(2007). "New Insights on the
Nanoparticle Growth Mechanism in the
Citrate Reduction of Gold(III) Salt: Formation of the Au Nanowire
Intermediate and Its Nonlinear Optical Properties". J. Phys. Chem. C.
111 (17): 6281–6287. doi:10.1021/jp068666o.
^ M. Brust; M. Walker; D. Bethell; D. J. Schiffrin; R. Whyman (1994).
"Synthesis of Thiol-derivatised
Nanoparticles in a Two-phase
Liquid-Liquid System". Chem. Commun. (7): 801–802.
^ Manna, A.; Chen, P.; Akiyama, H.; Wei, T.; Tamada, K.; Knoll, W.
(2003). "Optimized Photoisomerization on
Nanoparticles Capped by
Unsymmetrical Azobenzene Disulfides". Chem. Mater. 15 (1): 20–28.
^ Gao, Jie; Huang, Xiangyi; Liu, Heng; Zan, Feng; Ren, Jicun
(2012-03-06). "Colloidal Stability of
Nanoparticles Modified with
Thiol Compounds: Bioconjugation and Application in Cancer Cell
Imaging". Langmuir. 28 (9): 4464–4471. doi:10.1021/la204289k.
^ Bekalé, Laurent, Saïd Barazzouk, and Surat Hotchandani.
"Beneficial Role of
Nanoparticles as Photoprotector of Magnesium
Tetraphenylporphyrin." SpringerReference (n.d.): n. pag. Web. 14 Nov.
Gold Nanoparticles." Nanomanufacturing Process
Database (n.d.): n. pag. Web. 14 Nov. 2016.
Gold Nanoparticles." Nanomanufacturing Process
Database (n.d.): n. pag. Web. 14 Nov. 2016.
^ S.D. Perrault; W.C.W. Chan (2009). "Synthesis and Surface
Modification of Highly Monodispersed, Spherical
50-200 nm". J. Am. Chem. Soc. 131 (47): 17042–3.
doi:10.1021/ja907069u. PMID 19891442.
^ M.N. Martin; J.I. Basham; P. Chando; S.-K. Eah (2010). "Charged Gold
Nanoparticles in Non-Polar Solvents: 10-min Synthesis and 2D
Self-Assembly". Langmuir. 26 (10): 7410–7417.
doi:10.1021/la100591h. A 3-min demonstration video for the
Martin synthesis method is available at YouTube
^ Kalishwaralal, Kalimuthu; Deepak, Venkataraman; Ram Kumar Pandian,
Sureshbabu; Gurunathan, Sangiliyandi (1 November 2009). "Biological
synthesis of gold nanocubes from Bacillus licheniformis". Bioresource
Technology. 100 (21): 5356–5358.
^ Navarro, Julien R.G.; Lerouge, Frédéric; Cepraga, Cristina;
Micouin, Guillaume; Favier, Arnaud; Chateau, Denis; Charreyre,
Marie-Thérèse; Lanoë, Pierre-Henri; Monnereau, Cyrille; Chaputa,
Frédéric; Marotte, Sophie; Leverrier, Yann; Marvel, Jacqueline;
Kamada, Kenji; Andraud, Chantal; Baldeck, Patrice L.; Parola, Stephane
(2013). "Nanocarriers with ultrahigh chromophore loading for
fluorescence bio-imaging and photodynamic therapy". Biomaterials. 34:
^ Baigent, CL; Müller, G (1980). "A colloidal gold prepared using
ultrasonics". Experientia. 36 (4): 472–473.
^ Jianling Zhang; Jimin Du; Buxing Han; Zhimin Liu; Tao Jiang; Zhaofu
Zhang (2006). "Sonochemical Formation of Single-Crystalline Gold
Nanobelts". Angew. Chem. 118 (7): 1134–7.
^ Sakai, Toshio; Alexandridis, Paschalis (2005). "Mechanism of Gold
Nanoparticle Growth and Size Control in Aqueous
Amphiphilic Block Copolymer Solutions at Ambient Conditions". The
Journal of Physical Chemistry B. 109: 7766–7777.
^ Ray, Debes; Aswal, Vinod K.; Kohlbrecher, Joachim (2011). "Synthesis
and Characterization of High Concentration Block Copolymer-Mediated
Gold Nanoparticles". Langmuir. 27: 4048–4056.
Boisselier, E.; Astruc, D (2009). "
Gold nanoparticles in nanomedicine:
preparations, imaging, diagnostics, therapies and toxicity". Chemical
Society Reviews. 38 (6). pp. 1759–1782.
doi:10.1039/b806051g. - " This critical review provides an
overall survey of the basic concepts and up-to-date literature results
concerning the very promising use of gold nanoparticles (AuNPs) for
Wikimedia Commons has media related to Colloidal gold.
Moriarty, Philip. "Au –
Gold Nanoparticle". Sixty Symbols. Brady
Haran for the University of Nottingham.
Point-by-point methods for citrate synthesis and hydroquinone
synthesis of gold nanoparticles are ava