Gold Nanoparticles: Assembly, Supramolecular Chemistry,
Quantum-Size-Related Properties, and Applications toward Biology, Catalysis,
and Nanotechnology
Marie-Christine Daniel and Didier Astruc*
Molecular Nanosciences and Catalysis Group, LCOO, UMR CNRS No. 5802, Universite´ Bordeaux I, 33405 Talence Cedex, France
Received August 6, 2003
Contents
1. Historic Introduction 293
2. General Background: Quantum Size Effect and
Single-Electron Transitions
294
3. Synthesis and Assembly 296
3.1. Citrate Reduction 296
3.2. The Brust−Schiffrin Method: Two-Phase
Synthesis and Stabilization by Thiols
296
3.3. Other Sulfur Ligands 297
3.4. Other Ligands 298
3.4.1. Phosphine, Phosphine Oxide, Amine, and
Carboxylate Ligands
298
3.4.2. Isocyanide 298
3.4.3. Acetone 298
3.4.4. Iodine 298
3.5. Microemulsion, Reversed Micelles,
Surfactants, Membranes, and Polyelectrolytes
298
3.6. Seeding Growth 298
3.7. Physical Methods: Photochemistry (UV,
Near-IR), Sonochemistry, Radiolysis, and
Thermolysis
298
3.8. Solubilization in Fluorous and Aqueous Media 299
3.9. Characterization Techniques 300
3.10. Bimetallic Nanoparticles 303
3.11. Polymers 304
3.12. Dendrimers 307
3.13. Surfaces, Films, Silica, and Other AuNP
Materials
308
4. Physical Properties 312
4.1. The Surface Plasmon Band (SPB) 312
4.2. Fluorescence 314
4.3. Electrochemistry 315
4.4. Electronic Properties Using Other Physical
Methods
315
5. Chemical, Supramolecular, and Recognition
Properties
317
5.1. Reactions of Thiolate-Stabilized AuNPs 317
5.2. Supramolecular Chemistry 318
5.3. Molecular Recognition 319
5.3.1. Redox Recognition Using Functionalized
AuNPs as Exoreceptors
319
5.3.2. Miscellaneous Recognition and Sensors 320
6. Biology 321
6.1. DNA−AuNPs Assemblies and Sensors 321
6.2. AuNP-Enhanced Immuno-Sensing 323
6.3. AuNP Sugar Sensors 323
6.4. Other AuNP Bioconjugates: Peptides, Lipids,
Enzymes, Drugs, and Viruses
324
6.5. AuNP Biosynthesis 325
7. Catalysis 325
7.1. Catalysis of CO Oxidation 325
7.2. Electrochemical Redox Catalysis of CO and
CH
3
OH Oxidation and O
2
Reduction
326
7.3. Catalysis of Hydrogenation of Unsaturated
Substrates
326
7.4. Catalysis by Functional Thiolate-Stabilized
AuNPs
326
7.5. Other Types of Catalysis 327
8. Nonlinear Optics (NLO) 327
9. Miscellaneous Applications 328
10. Conclusion and Perspectives 329
11. Acknowledgment 329
12. Abbreviations 329
13. References 330
1. Historic Introduction
Although gold is the subject of one of the most
ancient themes of investigation in science, its renais-
sance now leads to an exponentially increasing
number of publications, especially in the context of
emerging nanoscience and nanotechnology with nano-
particles and self-assembled monolayers (SAMs). We
will limit the present review to gold nanoparticles
(AuNPs), also called gold colloids. AuNPs are the
most stable metal nanoparticles, and they present
fascinating aspects such as their assembly of multiple
types involving materials science, the behavior of the
individual particles, size-related electronic, magnetic
and optical properties (quantum size effect), and their
applications to catalysis and biology. Their promises
are in these fields as well as in the bottom-up
approach of nanotechnology, and they will be key
materials and building block in the 21st century.
Whereas the extraction of gold started in the 5th
millennium B.C. near Varna (Bulgaria) and reached
10 tons per year in Egypt around 1200-1300 B.C.
when the marvelous statue of Touthankamon was
constructed, it is probable that “soluble” gold ap-
peared around the 5th or 4th century B.C. in Egypt
and China. In antiquity, materials were used in an
ecological sense for both aesthetic and curative
purposes. Colloidal gold was used to make ruby glass
293Chem. Rev. 2004, 104, 293−346
10.1021/cr030698+ CCC: $48.50 © 2004 American Chemical Society
Published on Web 12/20/2003

and for coloring ceramics, and these applications are
still continuing now. Perhaps the most famous ex-
ample is the Lycurgus Cup that was manufactured
in the 5th to 4th century B.C. It is ruby red in
transmitted light and green in reflected light, due to
the presence of gold colloids. The reputation of soluble
gold until the Middle Ages was to disclose fabulous
curative powers for various diseases, such as heart
and venereal problems, dysentery, epilepsy, and
tumors, and for diagnosis of syphilis. This is well
detailed in what is considered as the first book on
colloidal gold, published by the philosopher and
medical doctor Francisci Antonii in 1618.
1
This book
includes considerable information on the formation
of colloidal gold sols and their medical uses, including
successful practical cases. In 1676, the German
chemist Johann Kunckels published another book,
2a
whose chapter 7 concerned “drinkable gold that
contains metallic gold in a neutral, slightly pink
solution that exert curative properties for several
diseases”. He concluded, well before Michael Faraday
(vide infra), that “gold must be present in such a
degree of communition that it is not visible to the
human eye”. A colorant in glasses, “Purple of Cas-
sius”, is a colloid resulting from the heterocoagulation
of gold particles and tin dioxide, and it was popular
in the 17th century.
2b
A complete treatise on colloidal
gold was published in 1718 by Hans Heinrich
Helcher.
3
In this treatise, this philosopher and doctor
stated that the use of boiled starch in its drinkable
gold preparation noticeably enhanced its stability.
These ideas were common in the 18th century, as
indicated in a French dictionary, dated 1769,
4
under
the heading “or potable”, where it was said that
“drinkable gold contained gold in its elementary form
but under extreme sub-division suspended in a
liquid”. In 1794, Mrs. Fuhlame reported in a book
5
that she had dyed silk with colloidal gold. In 1818,
Jeremias Benjamin Richters suggested an explana-
tion for the differences in color shown by various
preparation of drinkable gold:
6
pink or purple solu-
tions contain gold in the finest degree of subdivision,
whereas yellow solutions are found when the fine
particles have aggregated.
In 1857, Faraday reported the formation of deep-
red solutions of colloidal gold by reduction of an
aqueous solution of chloroaurate (AuCl
4
-
) using
phosphorus in CS
2
(a two-phase system) in a well-
known work. He investigated the optical properties
of thin films prepared from dried colloidal solutions
and observed reversible color changes of the films
upon mechanical compression (from bluish-purple to
green upon pressurizing).
7
The term “colloid” (from
the French, colle) was coined shortly thereafter by
Graham, in 1861.
8
Although the major use of gold
colloids in medicine in the Middle Ages was perhaps
for the diagnosis of syphilis, a method which re-
mained in use until the 20th century, the test is not
completely reliable.
9-11
In the 20th century, various methods for the
preparation of gold colloids were reported and
reviewed.
11-17
In the past decade, gold colloids have
been the subject of a considerably increased number
of books and reviews,
15-44
especially after the break-
throughs reported by Schmid
17,19,21
and Brust et al.
22,27
The subject is now so intensively investigated, due
to fundamental and applied aspects relevant to the
quantum size effect, that a majority of the references
reported in the present review article have appeared
in the 21st century. Readers interested in nano-
particles in general can consult the excellent books
cited in refs 15, 24, 28, 33, and 43. The book by
Hayat, published in 1989,
14
essentially deals with
biological aspects and imaging of AuNPs.
2. General Background: Quantum Size Effect and
Single-Electron Transitions
Physicists predicted that nanoparticles in the
diameter range 1-10 nm (intermediate between the
size of small molecules and that of bulk metal) would
display electronic structures, reflecting the electronic
band structure of the nanoparticles, owing to quan-
tum-mechanical rules.
29
The resulting physical prop-
erties are neither those of bulk metal nor those of
molecular compounds, but they strongly depend on
Marie-Christine Daniel was born in Vannes, France. She graduated from
the University of Rennes (France). She is now finishing her Ph.D. on
exoreceptors at the Bordeaux 1 University in the research group of
Professor Didier Astruc. Her doctoral research is concerned with the
recognition of anions of biological interest using functionnalized gold
nanoparticles and redox-active metallodendrimers.
Didier Astruc is Professor of Chemistry at the University Bordeaux I and
has been a Senior Member of the Institut Universitaire de France since
1995. He studied in Rennes (thesis with R. Dabard), and then did his
postdoctoral research at MIT with R. R. Schrock. He is the author of
Electron Transfer and Radical Processes in Transition-Metal Chemistry
(VCH, 1995, prefaced by Henry Taube) and Chimie Organome´tallique
(EDP Science, 2000; Spanish version in 2003). His research interests
are in organometallic chemistry at the interface with nanosciences,
including sensing, catalysis, and molecular electronics.
294 Chemical Reviews, 2004, Vol. 104, No. 1 Daniel and Astruc