Alkylene-bridged N,N,N′N′-Tetrasubstituted Bis(2-amino-5-thiazolyl)methinium Salts-A New Class of Strongly Fluorescent Dyes

Dendritic nanoparticles-the impact of ligand cross-linking on nanocore stability

This paper describes the synthesis of gold nanoparticles stabilized by two series of new dendritic disulfide ligands with alkene groups at their peripheries. Intraparticle cross-linking of the alkene groups around the periphery of each nanoparticle was achieved by Grubbs' metathesis. It was demonstrated that cross-linking of the organic ligand has no effect on the size or morphology of the inorganic gold core as determined by TEM and UV-vis measurements. However, the introduction of cross-linking at the surface of the ligand enhances the stability of the gold nanocore toward chemical etchant agents (NaCN) and thermal treatment. The impact of cross-linking on nanoparticle stability is greater when the cross-linking is closer to the nanoparticle surface (i.e., using lower generation dendritic ligands). Attempts to perform further synthetic transformation on the hybrid materials in order to remove the gold core led to insoluble products composed predominantly of the dendritic ligand.

Dendron-Tethered and Templated CdS Quantum Dots on Single-Walled Carbon Nanotubes

CdS nanoparticles on the surface of single-walled carbon nanotubes (SWNTs) were templated and stabilized through the initial attachment of 1 --> 3 C-branched amide-based dendrons and were both photophysically and morphologically characterized. The CdS clusters were shown to be ca. 1.4 nm in diameter as calculated from their optical absorption spectra and exhibited reduced fluorescence emission intensity at 434 nm compared to that of CdS quantum dots stabilized by untethered dendrons due to partial emission quenching by the SWNT. Unchanged UV absorption behavior of these materials indicated that they are stable > 90 days at 25 degrees C.

Uniform gold nanorod arrays from polyethylenimine-coated alumina templates

Monolithic Au nanorod arrays can be grown by electrodeposition in Au-backed nanoporous alumina templates using polyethylenimine (PEI) as an adhesion layer, with excellent height control between 300 nm and 1.4 microm. The local height distribution can be extremely narrow with relative standard deviations well below 2%. The uniform growth rate appears to be determined by the adsorbed PEI matrix, which controls the growth kinetics of the grains comprising the nanorods. The nanorods can be retained as free-standing 2D arrays after careful removal of the AAO template. Reflectance spectroscopy reveals a collective plasmon mode with a maximum near 1.2 microm, in accord with recent calculations for 2D arrays of closely spaced cylindrical nanoparticles.

Completely “Green” Synthesis and Stabilization of Metal Nanoparticles

In the present Communication, a completely "green" synthetic method for producing silver nanoparticles is introduced. The process is simple, environmentally benign, and quite efficient. By gentle heating of an aqueous starch solution containing silver nitrate and glucose, we produce relatively monodisperse, starched silver nanoparticles. beta-d-Glucose serves as the green reducing agent, while starch serves as the stabilization agent.