Intact DENs

The preceding discussions have hopefully convinced readers that the PAMAM dendrimer template offers a variety of new opportunities for studying catalysis. These properties also present challenges for evaluating nanoparticle properties, particularly reaction kinetics. Nanoparticle surface geometric and electronic properties are extremely difficult to probe in solution, especially when the dendrimer inhibits access by various probe molecules. Further, the number of bonds between nanoparticle surfaces and dendrimer amine and amide groups is essentially unknown. In cases where the dendrimer may preferentially bind one metal over another, stoichiometries and activities are difficult to evaluate, thus making it extremely difficult to interpret catalysis results in terms of particle composition. 

Evaluating dendrimer templated nanoparticles in the absence of the dendrimer provides opportunities for insights into these new materials. In order to pursue these investigations, it is first necessary to immobilize DENs onto an appropriate substrate and to gently remove the dendrimer shell (see Fig. 4.8). Opportunities for controlling nanoparticle size and composition make DENs potentially important precursors for heterogeneous catalysts and electrocatalysts, and DEN deposition and thermolysis are similarly critically important steps in pursuing these applications. 

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Supported, intact DENs do not bind CO and are not active catalysts. Presumably, in the absence of solvent, the dendrimer collapses onto the nanoparticles preventing even small substrates from accessing the metal surface (11,12). This means that the organic dendrimer must be removed in order to prepare active catalysts. 

Lubberts E, Joosten LA, van de Loo FA, van den Gersselaar LA, van den Berg WB Reduction of interleukin-17-induced inhibihon of chondrocyte proteoglycan synthesis in intact murine articular carhlage by interleukin-4. Arthritis Rheum 2000 43 1300-1306. 

In order to better understand changes to the catalyst surface during activation, infrared spectroscopy was used to monitor the dendrimer decomposition process. IR spectra of intact Au-DENs/TiOz are... 

Heck, A.J.R. and van den Heuvel, R.H.H. (2004) Investigation of intact protein complexes by mass spectrometry... 

TJ Romer, JF Brennan III, TC Bakker Schut, R Wolthuis, RCM van den Hoogen, JJ Emeis, A van der Laarse, AVG Bruschke, GJ Puppels. Raman spectroscopy for quantifying cholesterol in intact coronary artery wall. Atherosclerosis 141 117-124, 1998. 

Note 1.6 nun (0.060 in.) sheet produced by hot rolling from a 136 kg (300 lb) ingot, (a) Solution heat treated at 760 °C (1400 °F), 20 min, fan air cooled, (b) Oxide and contamination layer due to aging treatment removed by sandblasting and pickling while they were left intact on all other specimens. Source EA. Cros ey and J.M. Van Or-den, ANew Titanium Alloy for Forms and Weldments, Met. Eng. Quart., Vol 13,1973, p 55-61 also Souixx Book on Materials Selection, Vol 2, American Society for Metals, p 170-176... 

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