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.

The field of nanoparticle research has drawn much attention in the past decade as a result of the search for new materials. Size confinement results in new electronic and optical properties, possibly suitable for many electronic and optoelectronic applications. A characteristic feature of noble metal nanoparticles is the strong color of their colloidal solutions, which is caused by the surface plasmon absorption. This article describes our studies of the properties of the surface plasmon absorption in metal nanoparticles that range in size between 10 and 100 nm. The effects of size, shape, and composition on the plasmon absorption maximum and its bandwidth are discussed. Furthermore, the optical response of the surface plasmon absorption due to excitation with femtosecond laser pulses allowed us to follow the electron dynamics (electron−electron and electron−phonon scattering) in these metal nanoparticles. It is found that the electron−phonon relaxation processes in nanoparticles, which are smaller than t...

Spectral properties and relaxation dynamics of surface plasmon electronic oscillations in gold and silver nanodots and nanorods

Recent years have seen a rapid expansion of research into nanophotonics based on surface plasmon–polaritons. These electromagnetic waves propagate along metal–dielectric interfaces and can be guided by metallic nanostructures beyond the diffraction limit. This remarkable capability has unique prospects for the design of highly integrated photonic signal-processing systems, nanoresolution optical imaging techniques and sensors. This Review summarizes the basic principles and major achievements of plasmon guiding, and details the current state-of-the-art in subwavelength plasmonic waveguides, passive and active nanoplasmonic components for the generation, manipulation and detection of radiation, and configurations for the nanofocusing of light. Potential future developments and applications of nanophotonic devices and circuits are also discussed, such as in optical signals processing, nanoscale optical devices and near-field microscopy with nanoscale resolution.

Plasmonics beyond the diffraction limit

Gold nanorods: Synthesis, characterization and applications

Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.

Optical properties and ultrafast dynamics of metallic nanocrystals.

Femtosecond pump‐probe experiments with a time resolution of 100 fs have been performed for copper particles with a radius of 4 nm Differential absorption spectra for a pump centered at 205 eV indicates the broadening of the absorption band due to the surface plasmon The nonlinear response time derived from the recovery time of the nonlinear absorption is dependent on the pumping laser fluences, and is as short as 07 ps for 210 μJ/cm2 The relaxation dynamics of nonequilibrium electrons can be described by the usual electron‐phonon coupling model

Subpicosecond time response of third‐order optical nonlinearity of small copper particles in glass

Preparation and Nonlinear Optical Properties of Ag/SiO_2 Glass Composite Thin Films

A faradaic current on the order of a sub-pico-ampere was detected while fabricating two-dimensional oxide nanostructures on H-passivated Si(001) surfaces. The detected faradaic current has been shown to faithfully reflect the degree of probe oxidation with a clear dependence on the variation of voltage and the tip speed. The faradaic current in dynamic mode can serve as a sensitive monitor of the nano-oxidation reaction for implementing precise closed-loop control of the oxide growth.

In situ detection of faradaic current in probe oxidation using a dynamic force microscope

This article reports large nonlinear susceptibility χ(3) of nanometer‐sized particles of amorphous phosphorus. Nanocomposites of amorphous red phosphorous colloid particles (3–5 nm in diameter) and SiO2 glasses have been fabricated by ion implantation technique. Silica glasses implanted at an acceleration voltage of 180 keV to a dose of 5×1017 P+ ions/cm2 shows χ(3) of ∼1×10−6 esu, which is comparable to quantum‐sized crystals of semiconductors such as CuCl and CdS1−xSex. This is the first finding that quantum dots of amorphous semiconductors embedded in dielectrics exhibits such a large χ(3).

Large third‐order optical nonlinearity of nanometer‐sized amorphous semiconductor: Phosphorous colloids formed in SiO2 glass by ion implantation

A scanning optical microscope for low temperature imaging and spectroscopy with a gradient index rod-shaped microlens as an objective lens is presented. The solid immersion effect enhances the resolution to 310 nm of the full-width at half-maximum at the wavelength of 545 nm. Laser scanning mechanism located outside an optical cryostat enables to achieve large scanning ranges independent of temperature. The performance is demonstrated at 1.6 K on single molecules of terrylene in a dodecane crystal and on molecular J aggregates in thin polymer films.

Takashi Tokizaki

Papers

Subpicosecond time response of third‐order optical nonlinearity of small copper particles in glass

Preparation and Nonlinear Optical Properties of Ag/SiO_2 Glass Composite Thin Films

In situ detection of faradaic current in probe oxidation using a dynamic force microscope

Large third‐order optical nonlinearity of nanometer‐sized amorphous semiconductor: Phosphorous colloids formed in SiO2 glass by ion implantation

Laser scanning microscope for low temperature single molecule and microscale spectroscopy based on gradient index optics