Chemical imaging of pharmaceutical materials: fabrication of micropatterned resolution targets.

Resolution targets composed of thick poly(ethylene glycol) (PEG) lines on silicon substrates have been fabricated using the method of micromolding in capillaries (MiMIC). Patterns of three parallel lines with equal width and spacing have been prepared, with widths between 5 and 25 microm. Raman chemical images of the PEG-on-silicon devices as well as the metal-on-glass masks used to prepare the devices were measured. The Raman images were used to determine the impulse response of the instrument by comparing the measured images to model functions prepared by convolution of a test impulse function with the object functions of the devices. Impulse widths for PEG-on-silicon targets were approximately two times greater than impulse widths for metal-on-glass targets. The results provide a quantitative measure of the influence of light-matter interactions on the spatial resolution achievable with chemical imaging instruments. This work shows that microfluidic channels can be used to produce robust patterns of PEG on silicon, and these patterns are realistic resolution targets for spectroscopic chemical imaging of pharmaceutical materials.

A theoretical study of P4O10: vibrational analysis, infrared and Raman spectra.

The normal mode frequencies and the corresponding vibrational assignments of tetraphosphorus decaoxide (P4O10) in tetrahedral (Td) symmetry are examined theoretically and experimentally. The Gaussian 98 set of quantum chemistry codes at the HF/6-311G*, MP2/6-311G*, and DFT/B3LYP/6-311G* levels of theory are used. By comparison to experimental normal mode frequencies deduced by Gilliam et al. [J. Phys. Chem. B 107 (2003) 2892], Chapman [Spectrochim. Acta A, 24 (1968) 1687], Beattie et al. [J. Chem. Soc. A (1970) 449], Konings et al. [J. Mol. Spectrosc. 152 (1992) 29] and the present work, correction factors for predominant vibrational motions are determined and compared. Normal modes were decomposed into five non-redundant motions (P-O stretch, P=O stretch, P-O-P bend, P-O-P wag, and P=O wag). Standard deviations found for the HF, MP2, and DFT corrected frequencies compared to experiment are 9, 5, and 4 cm(-1), respectively. Electron distribution for selected molecular orbitals is considered.

A theoretical and experimental study of Sb4O6: vibrational analysis, infrared, and Raman spectra.

The first ab initio theoretical study of tetraantimony hexoxide (Sb4O6) is reported. The normal mode frequencies, intensities, and the corresponding vibrational assignments of Sb4O6 in T(d) symmetry were calculated using the GAUSSIAN 98 set of quantum chemistry codes at the Hartree-Fock (HF)/CEP-121G, Møller-Plesset (MP2)/CEP-121G, and density functional theory (DFT)/B3LYP/CEP-121G levels of theory. By comparison to experimental data deduced by our laboratory and others, correction factors for the calculated vibrational frequencies were determined and compared. Normal modes were decomposed into three non-redundant motions (Sb-O-Sb stretch, Sb-O-Sb bend, and Sb-O-Sb wag). Percent relative errors found for the HF, DFT, and MP2 corrected frequencies when compared to experiment are 5.8, 6.1, and 5.7 cm(-1), respectively. Electron distributions for selected molecular orbitals are also considered.