Gold nanoparticles are encapsulatedwithin thermoresponsive pNIPAMmigrogels through an easy two‐stepprotocol. The core/shell structure ofthe composite is characterized by TEM,AFM, PCS, and UV‐vis spectroscopy. The restricted environment and thehigh porosity of the microgel shell arestudied through the overgrowth of thegold core.

Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N‐isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross‐linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core–shell systems is carried out by photon‐correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature‐induced local changes of the refractive index surrounding the gold cores.

Changing faces: The shape of gold nanorods can be finely tuned by controlled growth under sonication in DMF in the presence of poly(vinylpyrrolidone). Reshaping involves the formation of rods with sharp tips and strongly faceted lateral faces, and ultimately leads to perfect, single‐crystal octahedrons (see images). Mechanistic considerations indicate a shape‐inducing effect of the polymer through different binding interactions for the different faces.

A simple procedure for creating titania sol–gel‐based semiconductor thin films is described. Gold nanoparticles are doped homogeneously into the precursor mixture and the particles are homogeneously distributed in the resultant films when prepared using spin‐coating. The effects of particle loading and annealing temperature on the optical properties of the resultant films are characterized. Ellipsometry, X‐ray diffraction, atomic force microscopy, and surface plasmon spectroscopy are used to monitor the crystallization and porosity changes during film synthesis.

A reproducible route for the preparation of high‐quality CdSe–ZnS‐doped titania and zirconia waveguides is presented. The optical properties of the resultant composite materials are found to be sensitive to the semiconducting properties of the host matrix. Titania‐based composites are seen to be inherently photounstable because of photoelectron injection into the bulk matrix and subsequent nanocrystal (NC) oxidation. In comparison, zirconia composites are significantly more robust with high photoluminescence (PL) retained for annealing temperatures up to 300 °C. Both titania and zirconia composite waveguides exhibit amplified stimulated emission (ASE); however only zirconia‐based waveguides exhibit long‐term photostability (loss of less than 30 % ASE intensity after more than 40 min continuous excitation). We conclude that the low electron affinity of zirconia and its inherent high refractive index makes it an ideal candidate for NC‐based optical waveguides.

A general scaling law connecting the stiffness and dissipative properties of a linear mechanical oscillator immersed in a viscous fluid is derived. This enables the noninvasive experimental determination of the stiffness of small elastic bodies of arbitrary shape by measuring their resonant frequency and quality factor in fluid ͑typically air͒. In so doing, we elucidate the physical basis of the method of Sader et al. ͓Rev. Sci. Instrum. 70, 3967 ͑1999͔͒ for determining the stiffness of rectangular atomic force microscope cantilevers, and discuss its applicability. The validity of the derived general technique is demonstrated by calibrating atomic force microscope cantilevers with complex geometries, and its implications to small bodies in general are discussed.

Faceted iron oxide nanoparticles with octahedral shape were synthesized through controlled modification of the iron oleate decomposition method. The key to this novel shape control is the "in situ" formation of trioctylammonium bromide (TOAHB) during the process, through decomposition of quaternary ammonium salts. This hypothesis was confirmed by carrying out the synthesis in the presence of preformed TOAHB, which again resulted in the formation of iron oxide octahedra. A detailed high-resolution transmission electron microscopy (HRTEM) analysis of the nanooctahedra was performed for shape analysis and structural characterization. X-ray photoelectron spectroscopy (XPS) indicates the presence of both metallic iron and iron oxide within the nanooctahedra. The results obtained by HRTEM and XPS are in agreement with magnetic analysis, which revealed the presence of several magnetic phases in the samples.

In die Breite gegangen: Die Form von Goldnanostäben kann durch ein Wachstum in DMF unter Ultraschallbestrahlung in Gegenwart von Poly(vinylpyrrolidon) fein abgestimmt werden. Zunächst entwickeln die Stäbe Spitzen und facettenreiche Flächen, bevor schließlich perfekt oktaedrische Einkristalle erhalten werden (siehe Bildfolge). Vermutlich steuert das Polymer die Formbildung, indem es unterschiedlich mit den verschiedenartigen Flächen wechselwirkt.