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.

Titanium Dioxide Nanomaterials: Synthesis, Properties, Modifications, and Applications

Dye-sensitized solar cells (DSCs) offer the possibilities to design solar cells with a large flexibility in shape, color, and transparency. DSC research groups have been established around the worl ...

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Dye-Sensitized Solar Cells

J. Appl. Cryst.の発刊に際して

The long-standing challenge of designing and constructing new crystalline solid-state materials from molecular building blocks is just beginning to be addressed with success. A conceptual approach that requires the use of secondary building units to direct the assembly of ordered frameworks epitomizes this process: we call this approach reticular synthesis. This chemistry has yielded materials designed to have predetermined structures, compositions and properties. In particular, highly porous frameworks held together by strong metal-oxygen-carbon bonds and with exceptionally large surface area and capacity for gas storage have been prepared and their pore metrics systematically varied and functionalized.

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Reticular synthesis and the design of new materials

Two kinds of cobalt−iron cyanides (Rb0.66Co1.25[Fe(CN)6]·4.3H2O and Co1.5[Fe(CN)6]·6H2O) with different electronic structures have been investigated to understand the photoinduced long-range magnetic ordering. Rb0.66Co1.25[Fe(CN)6]·4.3H2O produces a photomagnetic effect, whereas Co1.5[Fe(CN)6]·6H2O does not respond to light. FT-IR and Mossbauer studies revealed that their oxidation states are expressed as Rb0.66CoIII0.84CoII0.41[FeII(CN)6] and CoII1.5[FeIII(CN)6], respectively. The difference in the oxidation states of the metal atoms in these two compounds has been explained by the Co coordination with H2O or CN ligands. In the case of Rb0.66Co1.25[Fe(CN)6]·4.3H2O, more CN ligands are involved in coordination than expected in the case of Co1.5[Fe(CN)6]·6H2O. A charge-transfer (CT) band from FeII to CoIII is observed at around 550 nm for Rb0.66Co1.25[Fe(CN)6]·4.3H2O. The magnetism of Rb0.66Co1.25[Fe(CN)6]·4.3H2O changed from paramagnetic to ferrimagnetic due to the CT from FeII to CoIII when illuminated a...

Photoinduced Long-Range Magnetic Ordering of a Cobalt-Iron Cyanide.

The structural blue color of a Morpho butterfly originates from the diffraction of light and interference effects due to the presence of the microstructures on the wing of the butterfly. Structural color on the surface of a damselfish reversibly changes between green and blue. Inspired by these creatures, we have been trying to prepare high-quality and functional structural color films. We describe our efforts in this Account. A useful technique to prepare such structural color films in colloidal solution is a “lifting” method, which allows us to quickly fabricate brilliant colloidal crystal films. The thicknesses of the films can be controlled by precisely adjusting the particle concentration and the lifting speed. Moreover, in order to prepare a complicated structure, we have used template methods. Indeed, we have successfully prepared the inverse structure of the wing of a Morpho butterfly with this technique. Initially, however, our structural color films had a whitish appearance due to the scattering...

Structural color films with lotus effects, superhydrophilicity, and tunable stop-bands

The magnetic properties of the spin-crossover compounds, [Fe(qsal)2]NCSe·MeOH (1) and [Fe(qsal)2]NCSe·CH2Cl2 (2), have been measured. We have discovered that both compounds 1 and 2 exhibit a wide thermal hysteresis loop of 140 K (T1/2↑ = 352 K and T1/2↓ = 212 K) and 180 K (T1/2↑ = 392 K and T1/2↓ = 212 K), respectively, in the first cycle. Thermogravimetric analysis shows that solvent molecules escape from compounds 1 and 2 around 340 and 395 K, respectively. This means that the hysteresis loops observed for the first cycle are only apparent ones. Following the first loop, they show a two-step spin-crossover in warming mode. The so-called “step 1” and “step 2” are centered around T1/2(S1)↑ = 215 K and T1/2(S2)↑ = 282 K, respectively. On the other hand, a one-step spin-crossover occurs at T1/2↓ = 212 K in cooling mode. The hysteresis widths can be estimated to be 3 K (step 1) and 70 K (step 2), assuming that the widths in steps 1 and 2 are defined as the differences between T1/2(S1)↑ and T1/2↓, and T1/2(S2...

Iron(III) spin-crossover compounds with a wide apparent thermal hysteresis around room temperature.

We tried to design the magnet exhibiting magnetic pole (N and S) inversion by photostimuli. The magnetization of Fe1.5IICrIII(CN)6⋅7.5H2O was changed in a photon mode by visible light. A ferro-ferrimagnet (Fe0.40IIMn0.60II)1.5CrIII(CN)6⋅7.5H2O mixed by ferromagnetic (Fe–Cr system showing the change of magnetization by optical stimuli) site and ferrimagnetic (Mn–Cr system showing no optical response) site showed negative magnetization at the temperature lower than compensation temperature (Tcomp=19 K). In this mixed metal cyanide magnet we have succeeded in demonstrating a novel magnetic behavior “photoinduced magnetic pole inversion.” Moreover, the magnetic pole inversion can be induced repeatedly by alternate optical and thermal stimulations.

Osamu Sato

Papers

Photoinduced Long-Range Magnetic Ordering of a Cobalt-Iron Cyanide.

Structural color films with lotus effects, superhydrophilicity, and tunable stop-bands

Iron(III) spin-crossover compounds with a wide apparent thermal hysteresis around room temperature.

Photoinduced magnetic pole inversion in a ferro-ferrimagnet: (Fe0.40IIMn0.60II) 1.5CrIII(CN)6

First observation of light-induced excited spin state trapping for an iron(III) complex [7]