The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in the size and shape control of magnetic nanoparticles has been made by developing methods such as co-precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.

Magnetic nanoparticles: Synthesis, protection, functionalization, and application

▪ Abstract Solution phase syntheses and size-selective separation methods to prepare semiconductor and metal nanocrystals, tunable in size from ∼1 to 20 nm and monodisperse to ≤5%, are presented. Preparation of monodisperse samples enables systematic characterization of the structural, electronic, and optical properties of materials as they evolve from molecular to bulk in the nanometer size range. Sample uniformity makes it possible to manipulate nanocrystals into close-packed, glassy, and ordered nanocrystal assemblies (superlattices, colloidal crystals, supercrystals). Rigorous structural characterization is critical to understanding the electronic and optical properties of both nanocrystals and their assemblies. At inter-particle separations 5–100 A, dipole-dipole interactions lead to energy transfer between neighboring nanocrystals, and electronic tunneling between proximal nanocrystals gives rise to dark and photoconductivity. At separations <5 A, exchange interactions cause otherwise insulating ass...

Synthesis and Characterization of Monodisperse Nanocrystals and Close-Packed Nanocrystal Assemblies

Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

Recent startling interest for lanthanide luminescence is stimulated by the continuously expanding need for luminescent materials meeting the stringent requirements of telecommunication, lighting, electroluminescent devices, (bio-)analytical sensors and bio-imaging set-ups. This critical review describes the latest developments in (i) the sensitization of near-infrared luminescence, (ii) “soft” luminescent materials (liquid crystals, ionic liquids, ionogels), (iii) electroluminescent materials for organic light emitting diodes, with emphasis on white light generation, and (iv) applications in luminescent bio-sensing and bio-imaging based on time-resolved detection and multiphoton excitation (500 references).

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Lanthanide luminescence for functional materials and bio-sciences

Paralleling the evolution of Fourier Transform Infrared Spectroscopy during the 1960’s and 1970’s there have been rapid developments in the area of Raman spectroscopy. The laser serves only in a secondary role for FT-IR spectroscopy, but as a source for excitation it has greatly revolutionized conventional Raman spectroscopy and led to the advent of new techniques including coherent anti-Stokes Raman scattering (CARS), Raman gain, inverse or hyper- Raman spectroscopy. Both FT-IR and Raman techniques have also benefited from the improvements in optoelectronic and data processing systems. While a moving mirror with high mechanical precision and a high quality beam splitter are basic to an FT-IR instrument, a double monochromator with precision gratings, which may be holographic, and a laser as light source are intrinsic to a Raman spectrometer. Improved detector systems (pyroelectric bolometers, such as triglycine sulfate, TGS, for FT-IR or photon counting for Raman), not available a decade ago now serve vital functions. Utilization of an on-line mini-computer is all but essential for practical FT-IR spectroscopy in order to facilitate the data handling and computation; it can also serve as a valuable accessory for the signal averaging and manipulation of Raman data.

Comparison of FT-IR and Raman Spectroscopy

Different techniques are applied in order to obtain information about ultrafast molecular and reaction dynamics. Femtosecond time-resolved pump-probe spectroscopy is used to investigate the dissociation reaction of NAI molecules. Starting from free NaI molecules, the environment is changed to solution-like conditions adding rare gas with different pressures. Femtosecond time-resolved degenerate four-wave mixing (DFWM) spectroscopy is performed in order to investigate molecular dynamics in iodine molecules in the gas phase. Depending on the timing of the laser pulses different dynamics are reflected in the DFWM transient signal. By the use of time evolution diagrams, the varying contribution of ground and excited-state dynamics can be explained conclusively. Supersonic jet-cooled potassium dimers are investigated in their electronic ground state by a femtosecond pump-probe experiment. The ground state vibrational wave packets are created by a stimulated Raman pumping process and selectively interrogated by resonance enhanced three photon ionization.

Femtosecond spectroscopy on simple molecular systems: pump-probe and four-wave mixing techniques

A blue-shifted output of a photonic-crystal fiber, providing a frequency upconversion of femtosecond Ti:sapphire laser pulses, is used to seed a double-pass optical parametric oscillator (OPA). The OPA is based on a BBO crystal, pumped by 65-mW 150-fs second-harmonic pulses of a Ti:sapphire laser. Gain factors in excess of 103 are demonstrated for such an OPA, yielding tunable light pulses within the range of wavelengths from 420 to 650 nm, a peak power up to 250 kW, and a typical pulse width of about 200 fs at a repetition rate of 100 kHz.

A double-pass optical parametric amplifier seeded by a blue-shifted output of a photonic-crystal fiber

1 RuAer Bos—kovic“ Institute, Bijenic—ka, c.54, P.O. Box 1016, 10001 Zagreb, Croatia2 Mineralogisches Institut, Universita” t Wu” rzburg, Am Hubland, D-97074 Wu” rzburg, Germany3 Institut fu” r Kristallographie, Universita” t Tu” bingen, Charlottenstr. 33, D-72070 Tu” bingen, Germany4 Institut fu” r Physikalische Chemie, Universita” t Wu” rzburg, Am Hubland, D-97074 Wu” rzburg, Germany

Wolfgang Kiefer

Papers

Comparison of FT-IR and Raman Spectroscopy

Femtosecond spectroscopy on simple molecular systems: pump-probe and four-wave mixing techniques

A double-pass optical parametric amplifier seeded by a blue-shifted output of a photonic-crystal fiber

Low-Temperature Anomalies of Cuprite Observed

Theory for morphology dependent resonances in the raman spectra of optically levitated dielectric microspheres