Hybrid organic-inorganic polymer thin films of the form (-O-Zn-O-C 2 H 4 -) n have been deposited from diethyl zinc and ethylene glycol using molecular layer deposition (MLD) over a range of substrate temperatures between 100 and 170 °C. Infrared transmission confirms that the films consist of Zn-O and ethylene-oxide units. In analogy with known alucone polymers of the form (-O-Al-O-R-) n , the zinc-based hybrid material is an example of a "zincone" polymer. In situ quartz crystal microbalance analysis indicated that the sequential surface reactions of diethyl zinc and ethylene glycol are sufficiently self-limiting and saturating to enable well-controlled MLD growth. Quantitative analysis of in situ quartz crystal microbalance and film thickness results indicate that ethylene glycol molecules can undergo a "double reaction" where the OH groups on both ends of the diol react with available Zn-C 2 H 5 surface sites to produce a relatively inert bridging alkane. The mass uptake per MLD cycle during Zn-hybrid film deposition decreases with increasing reaction temperature. Infrared transmission spectroscopy also shows that Zn-organic hybrid films are stable in dry air. However, the as-deposited ZnO-hybrid material could be hydrolyzed by H 2 O (for example, in ambient) resulting in films consisting of zinc oxide and zinc hydroxide with some carbon remnants. Spectroscopic ellipsometry indicates the thickness of hydrolyzed films increases linearly with reaction cycles, and scanning probe and transmission electron microscopy images show the hydrolyzed ZnO-hybrid film coating is uniform and conformal. The transmission electron micrographs also show the hydrolyzed Zn-hybrid films contain nanoscale porosity. These results suggest new pathways to fabricate organic-inorganic hybrid materials, including metalorganic framework structures.

The hepatitis delta virus (HDV) ribozyme uses a cytosine to facilitate general acid-base catalysis. Biochemical studies suggest that C75 has a pKa perturbed to near neutrality. To measure this pKa directly, Raman spectra were recorded on single ribozyme crystals using a Raman microscope. A spectral feature arising from a single neutral cytosine was identified at 1528 cm(-1). At low pH, this mode was replaced with a new spectral feature. Monitoring these features as a function of pH revealed pKa values for the cytosine that couple anticooperatively with Mg2+ binding, with values of 6.15 and 6.40 in the presence of 20 and 2 mM Mg2+, respectively. These pKa values agree well with those obtained from ribozyme activity experiments in solution. To correlate the observed pKa with a specific nucleotide, crystals of C75U, which is catalytically inactive, were examined. The Raman difference spectra show that this mutation does not affect the conformation of the ribozyme. However, crystals of C75U did not produce a signal from a protonatable cytosine, providing strong evidence that protonation of C75 is being monitored in the wild-type ribozyme. These studies provide the first direct physical measurement of a pKa near neutrality for a catalytic residue in a ribozyme and show that ribozymes, like their protein enzyme counterparts, can optimize the pKa of their side chains for proton transfer.

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The reactions of trimethylaluminum (TMA) toward substrates during the Al 2 O 3 atomic layer deposition (ALD) on a variety of polymers were studied by in situ Fourier transform infrared spectroscopy (FTIR). The experiments demonstrate that TMA reacts with certain nucleophilic functional groups on the polymer surface during the first several ALD cycles. For some polymer substrates, TMA vapor penetrates into the polymer and reacts in the polymer bulk. In both cases, the initial reaction plays an important role in the nucleation and growth of Al 2 O 3 . For chemically inert polymers, such as polypropylene, nucleation of Al 2 O 3 ALD is relative slow at the initial stage due to the lack of reactive groups on the substrate. However, polyester, polyamide and polyether are more reactive, and in situ FTIR spectra showed a larger extent of reaction with TMA, facilitating the nucleation of ALD film on these polymers. By comparing FTIR spectra, we quantitatively estimate the extent of TMA reaction towards different polymers, and confirmed the results using X-ray photoelectron spectroscopy and scanning electron microscopy. Results give insight into the importance of the polymer structure in determining the nature and extent of the reaction during ALD film processing on polymer substrates.

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