Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles 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 appeared 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 293 Chem. Rev. 2004, 104, 293−346

Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology.

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Self-assembled monolayers of thiolates on metals as a form of nanotechnology.

The development of novel materials is a fundamental focal point of chemical research; and this interest is mandated by advancements in all areas of industry and technology. A good example of the synergism between scientific discovery and technological development is the electronics industry, where discoveries of new semiconducting materials resulted in the evolution from vacuum tubes to diodes and transistors, and eventually to miniature chips. The progression of this technology led to the development * To whom correspondence should be addressed. B.L.C.: (504) 2801385 (phone); (504) 280-3185 (fax); bcushing@uno.edu (e-mail). C.J.O.: (504)280-6846(phone);(504)280-3185(fax);coconnor@uno.edu (e-mail). 3893 Chem. Rev. 2004, 104, 3893−3946

http://depa.fquim.unam.mx/amyd//archivero/FidelmarLechugaSanabria_4940.pdf

Recent advances in the liquid-phase syntheses of inorganic nanoparticles.

In this report, we evaluate the present state of the rapidly emerging field of monolayer-protected cluster (MPC) molecules with regard to their synthesis and monolayer functionalization, their core and monolayer structure, their composition, and their properties. Finally, we canvass some of the important remaining research opportunities involving MPCs.

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Monolayer-Protected Cluster Molecules

Surface plasmons (SPs) are coherent oscillations of conduction electrons on a metal surface excited by electromagnetic radiation at a metal -dielectric interface. The growing field of research on such light -metal interactions is known as ‘plasmonics’. 1-3 This branch of research has attracted much attention due to its potential applications in miniaturized optical devices, sensors, and photonic circuits as well as in medical diagnostics and therapeutics. 4-8

Nanostructured plasmonic sensors.

Carboxylate-modified gold nanoparticles have been synthesized in a single-phase system based on the reduction of hydrogen tetrachloroaurate(III) by sodium borohydride in methanol using mercaptosuccinic acid (MSA) as the stabilizing thiol ligand. Five samples with diameters of 10.2, 10.8, 12.8, 19.4, and 33.6 A have been prepared as water-redispersible powders through decreasing the initial MSA/HAuCl4 molar ratio from 2.5 to 0.5. These samples were characterized by X-ray diffraction, transmission electron microscopy, elemental analysis, thermogravimetric analysis, ζ-potential measurement, Fourier transform infrared spectroscopy, and UV−vis spectroscopy. The results show that a large number of the particles are fcc single crystals with the polyhedral morphology of a truncated octahedral motif and that a self-assembled monolayer of thiolates has indeed formed through the adsorption of mercapto groups on the gold particle surface; the maximum packing density of the thiolates is 15.23 A2 per mercapto group. Th...

Synthesis and Characterization of Carboxylate-Modified Gold Nanoparticle Powders Dispersible in Water

The coagulation of Au nanoparticles dispersed in organic liquids was dramatically accelerated under the illumination of light It was clarified through the wavelength dependence of the irradiation that particles coagulated with the illumination of visible light and coalesced upon irradiation of UV light The coagulation process was characteristic of the surface plasmon oscillation of small metallic particles but not of the interband transition The enhanced van der Waals attraction force or the photoinduced deionization of particles is suggested to be a cause of this finding Particle clustering proceeded 1-dimensionally at the early stage and 17-dimensionally in the fractal dimension at the later stage of the coagulation

Photoinduced Coagulation of Au Nanocolloids

Tetracarbene (1) was generated by photolysis of the corresponding tetradiazo compound (2) in a 2-methyltetrahydrofuran glass or a single crystal of benzophenone at cryogenic tempreatures. The temperature dependence of paramagnetic susceptibility revealed its nonet spin multiplicity in the ground state. A behavior suggesting the presence of antiferromagnetic intermolecular interaction was also found when generated in the glass. The field dependence of magnetization of 1 was analyzed in terms of the Brillouin function and the experimental data fit closely to that of the theoretical value for J = */*. This is independent evidence for the nonet spin multiplicity of 1. The characteristic saturation behavior of magnetization in 1 was found to be due to its high spin multiplicity. Thus 1 may be regarded as a molecular superparamagnet. In the polycarbenes, the localized n spins a t carbenic centers are aligned all in parallel through the electron correlation between the mobile K spins, resulting in the intramolecular ferromagnetic spin ordering. Although the mechanism of spin ordering of a spins in polycarbenes is entirely different from that in metallic ferromagnets, the interaction between n and K spins resembles s-d interaction in dilute alloys. The potentiality of polycarbenes as a microdomain in macroscopic ferromagnets will be discussed. The explosive growth in the number of reports on organic conductors and superconductors has arisen from genunie interests in mobility of electrons in organic molecular crystals, components of which are insulators in themse1ves.I On the other hand, molecular design of organic ferromagnets which is becomming the current topic of theoretical interest in organic material science deals with the behavior of electron spins in organic molecules.* One of the strategies toward this goal is to construct organic molecules with high-spin multiplicity as domains in ferromagnets and to introduce ferromagnetic intermolecular (interdomain) interaction among them. High-spin organic molecules are accessible when nonbonding molecular orbitals are present due to the symmetry of the alternant hydrocarbon skeleton. Examples of the above category are m-phenylenebi~(phenylmethylene),~ its higher homologues, 3,6-dimethyleneanthracenediyl1,8-dioxyI$ etc. Recently we have generated tetracarbene, m-phenylenebis((diphenylmethylen-3-y1)methylene) (1) and proved its nonet spin multiplicity in the ground state by analyzing ESR fine structures of the sample oriented in a host single crystal of ben~ophenone.~ Now we have studied the magnetic behavior of this highly important tetracarbene 1 by means of magnetic susceptibility measurements.6 The magnet was composed of a main coil and a pair of reverse Helmholtz coils for the field gradient. The main field gradient, the temperature of a sample, and the weight change were carefully calibrated to enable the absolute magnetic susceptibility measurement. Inhomogeneity of the main magnetic field (HM) was leis than 0.2 T/m at the center of the main coil with the accuracy of lo-’. The accuracy of the field gradient (aHG/az) is better than IO-’ which was calibrated by a GaAs Hall device. The temperature of the cryostat (300-20 K) was regulated by the microcomputer, and data were recorded when the temperature stabilized within O.l%/min. The temperatures between 20 and 4 K were controlled manually by adjusting the flow of liquid helium, and lower temperatures than 4 K were obtained by pumping liquid helium. A platinum-resistance thermometer was used to read temperatures higher than 25 K and a carbon-resistance thermometer for lower temperatures. These temperature readings were calibrated in the whole temperature range with a magnetic thermometer with use of paramagnetic Cr(NH3)I Sculz, H. Adu. Phys. 1982, 31, 299. (b) Torrance, J . B. Arc. Chem. Res. 1979, 12, 79. (2) (a) McConnell, H. M. J . Chem. Phys. 1%3,39, 1910. (b) McConnell, H. M. Proc. Robert A . Welch Found. ConJ Chem. Res. 1967,1I, 144. (c ) Mataga, N. Theor. Chim. Acra 1968,10,372. (d) Ovchinnikov, A. A. Dokl. Akad. Nauk SSSR 1977, 236, 928. (e) Ovchinnikov, A. A. Theor. Chim. Acra 1978,47,297. (f) Buchachenko, A. L. Dokl. Akad. Nauk SSSR 1979, 244, 1146. (8) Breslow, R.; Juan, B.; Kluttz, R. Q.; Xia, C. 2. Terrahedron 1982,38,863. (h) Iwamura, H.; Sugawara, T.; Itoh, K.; Takui, T. Mol. Crysr. Liquid Cryst. 1985, 125, 251. (i) Breslow, R. Ibid. 1985, 125, 261. Q) Ooster, S.; Torrance, J. B.; Scumaker, R. R. The 1984 International Chemical Congress of Pacific Basin Societies, Abstract of Papers 07E28, Honolulu, Hawaii, December 1984. (3) (a) Itoh, K. Chem. Phys. Left. 1967,1, 235. (b) Itoh, K. Pure Appl. Chem. 1978, 50, 1251. (c) Wasserman, E.; Murray, R. W.; Yager, W. A.; Trozzolo, A. M.; Smolinsky, G. J. J . Am. Chem. SOC. 1967, 89, 5076. (4) (a) Seeger, D. E.; Berson, J . A. J . Am. Chem. SOC. 1983, 105, 5144. (b) Seeger, D. E.; Berson, J. A. Ibid. 1983, 105, 5146. (5 ) (a) Teki, Y.; Takui, T.; Itoh, K.; Iwamura, H.; Kobayashi, K. J . Am. Chem. SOC. 1983, 105, 3722. (b) Teki, Y . ; Takui, T.; Itoh, K.; Iwamura, H.; Kobayashi, K., to be published. ( 6 ) (a) Sugawara, T.; Bandow, S.; Kimura, K.; Iwamura, H.; Itoh, K. J . Am. Chem. SOC. 1984, 106, 6449. (b) Kimura, K.; Bandow, S. Solid State Phys. 1984, 20, 467. 0002-7863/86/ 15O8-0368$01.50/0

Magnetic behavior of nonet tetracarbene as a model for one-dimensional organic ferromagnets.

The influence of laser light irradiation at the surface plasmon frequency of the gold nanoparticles suspended in 2-propanol is examined by the UV−vis absorption spectral measurement and also by a t...

Colloidal Stability of Gold Nanoparticles in 2-Propanol under Laser Irradiation

Three new methods for the preparation of metal colloid in organic solvent are presented. These methods were the matrix isolation method, the gas flow-cold trap method and the gas flow–solution trap method; the latter was found to give a good colloid solution for the optical measurements. The metals reported are high purity Ag, Au, Cu, In, Al, Ca, Sn, and Pb. The stability of the colloid is dependent on the kind of metals: Al, In, Au, and Ag are stable, and Pb, Sn, Ca, and Cu are unstable. The optical absorption spectra of these sols were measured in ethanol solution in Ar atmosphere. They are discussed in relation to those reported on the solid matrix or on the solid substrate.

Keisaku Kimura

Papers

Synthesis and Characterization of Carboxylate-Modified Gold Nanoparticle Powders Dispersible in Water

Photoinduced Coagulation of Au Nanocolloids

Magnetic behavior of nonet tetracarbene as a model for one-dimensional organic ferromagnets.

Colloidal Stability of Gold Nanoparticles in 2-Propanol under Laser Irradiation

The Study of Metal Colloids Produced by Means of Gas Evaporation Technique. I. Preparation Method and Optical Properties in Ethanol