Researchers Examine Growth and Optical Properties of Gold Nanoparticles in Stained Glass
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production costs and reduced environmental pollution during fabrication. COLIN MCCORMICK
Researchers Examine Growth and Optical Properties of Gold Nanoparticles in Stained Glass Stained glass is best known from its extensive use in Gothic churches, although
its production dates back to ancient civilizations of Egypt and Rome. A colored “stain” is achieved when colorless metaldoped glass is heated at high temperatures. Annealing of gold-doped glass results in the formation of colloidal gold, which gives rise to a characteristic rubyred color through surface plasmon resonance (SPR). However, tuning the SPR
Octahedral Nanocontainer Molecules Formed Spontaneously Applications for nanocontainer molecules include stabilizing short-lived chemical species, accelerating chemical reactions, and directing regioselectivity and stereochemistry of reaction products. Supramolecular approaches to the selfassembly of nanocontainers, which involve hydrogen bonding or metal coordination chemistry, are efficient and quantitative. In contrast, nanocontainers constructed from cavitands (i.e., molecules whose constrained structure accommodates a cavity) typically require multiple steps. Recently, however, researchers from the Department of Chemistry and Chemical Biology at Rutgers University have used dynamic covalent chemistry to synthesize nanocontainers from 18 components in a single step and in high yield, greatly improving the simplicity and efficiency of nanocontainer synthesis. As reported in Angewandte Chemie International Edition (DOI: 10.1002/ anie.200504049), Rutgers University researcher R. Warmuth and co-researchers discovered a spontaneous formation of an octahedral nanocontainer (B), composed of six cavitands (A) linked together with 12 diamino bridges via 24 newly formed imine bonds (see Figure 1). Yields of up to 82% were achieved. The researchers used 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and electrospray ionization mass spectroscopy to validate the structure of B. Although the researchers were unable to isolate and purify B, they were able to reduce all 24 imine bonds and purify the trifluoroacetate salt of the resulting polyamino nanocontainer (C) with reversephase high-pressure liquid chromatography and isolate it in an overall 63% yield. Although crystals suitable for x-ray structure determination could not be obtained, the researchers used molecular mechanics (MM) calculations to estimate the cavity volume at 1700 Å3, which is large enough to encapsulate multiple guest molecules. Pulse-field gradient spin-echo NMR measurements and application of the Stokes–Einstein equation yielded a solvodynamic diameter of 3.2 nm, which is consistent with the MM model. The researchers also used MM to show that the formation of B requires each ethylenediamine to be in an anti conformation.
Figure 1. An octahedral nanocontainer (B) composed of six cavitands (A) linked together with 12 diamino bridges via 24 newly formed imine bonds; B is reduced to polyamino nanocontainer (C).
The researchers said, “We see p
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