There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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.

Signaling Recognition Events with Fluorescent Sensors and Switches.

BODIPY dyes and their derivatives: syntheses and spectroscopic properties.

Lanthanide ions possess fascinating optical properties and their discovery, first industrial uses and present high technological applications are largely governed by their interaction with light. Lighting devices (economical luminescent lamps, light emitting diodes), television and computer displays, optical fibres, optical amplifiers, lasers, as well as responsive luminescent stains for biomedical analysis, medical diagnosis, and cell imaging rely heavily on lanthanide ions. This critical review has been tailored for a broad audience of chemists, biochemists and materials scientists; the basics of lanthanide photophysics are highlighted together with the synthetic strategies used to insert these ions into mono- and polymetallic molecular edifices. Recent advances in NIR-emitting materials, including liquid crystals, and in the control of luminescent properties in polymetallic assemblies are also presented. (210 references.)

Taking advantage of luminescent lanthanide ions

Photophysics of Organic Molecules in Solution Introduction Electronic States Radiative Transitions Nonradiative Transitions Excited State Kinetics Acknowledgments Bibliography Transition Metal Complexes Electronic Structure Types of Excited States and Electronic Transitions Absorption and Emission Bands Jablonski Diagram Photochemical Reactivity Electrochemical Behavior Polynuclear Metal Complexes Photophysical Properties of Organic Compounds Photophysics of Organic Molecules in Solution Triplet-State Energies: Ordered Flash Photolysis: Designing Experiments Low-Temperature Photophysics of Organic Molecules Absorption and Luminescence Spectra of Organic Compounds ESR and ODMR Parameters of the Triplet State Photophysical Properties of Transition Metal Complexes Photophysical Parameters Absorption and Emission Spectra Abbreviations Rate Constants of Excited-State Quenching Ionization Energies, Electron Affinities, and Reduction Potentials Ionization Energies and Electron Affinities Reduction Potentials Bond Dissociation Energies Solvent Properties Donor Number Luminescence Spectroscopy Measurements Correction of Luminescence Intensity Measurements in Solution Fluorescence Quantum Yield Standards Phosphorescence Quantum Yield Standards Luminescence Lifetime Standards Light Sources and Filters Spectral Distribution of Photochemical Sources Transmission Characteristics of Light Filters and Glasses Chemical Actinometry Ferrioxalate Actinometer Photochromic Actinometers Reinecke's Salt Actinometer Uranyl Oxalate Actinometer Other Actinometers Miscellaneous Spin-Orbit Coupling Hammett ? Constants Fundamental Constants and Conversion Factors Index *References included in each chapter

Handbook of Photochemistry

An Effective Fluorescent Chemosensor for Mercury Ions

A mechanical switch in a [2]catenane, made up of a cyclobis(paraquat-p-phenylene) tetracation interlocked with a macrocyclic polyether containing a redox-active tetrathiafulvalene (TTF) unit and a 1,5-dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides "inside" the tetracationic cyclophane in the reduced state and "alongside" it in the oxidized species (TTF+ / TTF2+ ). Switching between the reduced (I4+ ) and oxidized state (I5+ (I6+ )) is accompanied by a dramatic color change.

A Chemically and Electrochemically Switchable [2]Catenane Incorporating a Tetrathiafulvalene Unit.

Despite the key role of magnesium in many fundamental biological processes, knowledge about its intracellular regulation is still scarce, due to the lack of appropriate detection methods. Here, we report the spectroscopic and photochemical characterization of two diaza-18-crown-6 hydroxyquinoline derivatives (DCHQ) and we propose their application in total Mg2+ assessment and in confocal imaging as effective Mg2+ indicators. DCHQ derivatives 1 and 2 bind Mg2+ with much higher affinity than other available probes (Kd = 44 and 73 μM, respectively) and show a strong fluorescence increase upon binding. Remarkably, fluorescence output is not significantly affected by other divalent cations, most importantly Ca2+, or by pH changes within the physiological range. Evidence is provided on the use of fluorometric data to derive total cellular Mg2+ content, which is consistent with atomic absorption data. Furthermore, we show that DCHQ compounds can be effectively employed to map intracellular ion distribution and m...

8-Hydroxyquinoline Derivatives as Fluorescent Sensors for Magnesium in Living Cells

Silica nanoparticles are versatile platforms with many intrinsic features, such as low toxicity. Proper design and derivatization yields particularly stable colloids, even in physiological conditions, and provides them with multiple functions. A suitable choice of dyes and synthetic strategy may, in particular, yield a very bright nanosystem. Silica nanoparticles thus offer unique potential in the nanotechnology arena, and further improvement and optimization could substantially increase their application in fields of high social and economic impact, such as medical diagnostics and therapy, environmental and food analysis, and security. This paper describes silica-based, multicomponent nanosystems with intrinsic directional energy- and electron-transfer processes, on which highly valued functions like light harvesting and signal amplification are based.

Marco Montalti

Papers

Handbook of Photochemistry

An Effective Fluorescent Chemosensor for Mercury Ions

A Chemically and Electrochemically Switchable [2]Catenane Incorporating a Tetrathiafulvalene Unit.

8-Hydroxyquinoline Derivatives as Fluorescent Sensors for Magnesium in Living Cells

Luminescent Silica Nanoparticles: Extending the Frontiers of Brightness