Catalysts spin number

Experiments on catalysts often require the measurement of an absolute spin concentration. Although this is a somewhat tedious task, it can be carried out to a moderate degree of accuracy. The number of spins per gram of unknown n is given by... 

Removal of the solvent from systems in which the anion-radical concentration had been increased by the coadsorption of anthracene or perylene caused no change in the number of unpaired spins. In catalyst samples where the TNB radical concentration had not been initially increased by ultraviolet irradiation or by warming the catalyst + TNB solution above room temperature (6), a 12-fold increase in the anion-radical concentration was obtained in the presence of adsorbed anthracene or perylene. For samples of decationated Y formed by dehydroxylation in vacuo, a sevenfold enhancement was observed. 

A fairly crude estimate of the magneton number for activated Lu203 and Y203 suggests that only one electron spin per site is active. But for nearly all the other catalysts studied the Bohr magneton number is much larger and it varies widely. 

A second, equally powerful means to prepare such materials relies on traditional inorganic polymerization tools, most notably sol-gel polymerization.24 25 A number of excellent reviews have appeared on this subject as well.5,12,17 In sol-gel processing, the functional monomer [i.e., an organoalkoxysilane such as 3-aminopropyltrimethox-ysilane (APTMS)] is combined with the cross-linking agent [i.e., a tetrafunctional alkoxysilane such as tetramethoxysilane (TMOS) or tetraethoxysilane (TEOS)], a catalyst (such as hydrochloric acid or ammonia), and the template molecule. The resultant sol can be left to gel to form a monolith, which can then be dried, sieved, and extensively washed to remove the template. Alternatively, the sol can be spin coated, dip coated, or electrodeposited on a surface to yield a thin film, which can be subsequently washed with a solvent to remove the template and yield the imprinted cavities. 

The energetics for the rotational levels of hydrogen are shown in Fig. 5.3. [To be exact, the 7=0 must be combined with electron spin S = 0 to yield a total spin quantum number T = 0 for ortho-hydrogen, 7=1 combines with S = 0 to yield T = 1.] As said above, a catalyst is needed to ensure that the spin statistics reach true thermodynamic equilibrium. 

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