Catalyst small molecule imaging

A chemically amplified deep UV photoresist system based on acetal chemistiy is reported. Acetal-protected pol vinylphenols) were prepared either by free radical polymerization of the monomers or chemical modification of poly(vinylphenol). In the presence of an add as a catalyst, the polymers thermally decomposed to aqueous base soluble po vinylphenol) and some small molecules. Therefore, the resists were formulated with the acetal-protected polymers and a photoadd generator such as triphei lsulfonium hex-afluoroantimonate. Positive-tone image could be resolved 1 exposing the resist film in deep UV region, post-baking, and developing in tetramethylam-monium hydroxide solutions. 

For supported metal catalysts, no simple calculation is possible. A direct measurement of the metal crystallite size or a titration of surface metal atoms is required (see Example 1.3.1). TWo common methods to estimate the size of supported crystallites are transmission electron microscopy and X-ray diffraction line broadening analysis. Transmission electron microscopy is excellent for imaging the crystallites, as illustrated in Figure 5.1.5. However, depending on the contrast difference with the support, very small crystallites may not be detected. X-ray diffraction is usually ineffective for estimating the size of very small particles, smaller than about 2 nm. Perhaps the most common method for measuring the number density of exposed metal atoms is selective chemisorption of a probe molecule like H2, CO, or O2. 

Fig. 1.9 High-pressure STM results. 90 Ax90 A STM images of cateilytically active Pt(lll) at 298 K in the presence of (a) 200 mTorr Hj and 20 mTorr D2 eind (b) 200 mTorr H2, 20 mTorr D2, and 5 mTorr CO. (c) CO molecules are represented by the small circles and color coded according to their proximity to a top site (dark) or to a bridge site light), (d) Dj and HD at 296 K, 200 mTorr H2, and 20 mTorr D2 were monitored using mass spectroscopy. The evolution of the D2 and HD partial pressures indicates that the Pt catalyst surface is actively producing HD, consistent with the STM image (a). (Adapted from ref. [18], reprinted with permission)...

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