IR Spectroscopic Methods for Studying Ultrathin Films on Powders

Comparison of IR Spectroscopic Methods for Studying Ultrathin Films on Powders 

The main advantage of the ATR method is the convenient and rapid sample preparation and linearity of the ATR band intensity-surface coverage dependence. In addition, it is the best method to study in situ the powder-liquid interface, especially in the spectral region where the liquid absorbs. 

Spectra collected by these fom methods of an oxidized layer on 50-70-p,m galena particles (natural PbS, n 4) using the same number of scans (100) and resolution (4 cm ) and a Perkin-Ehner 1760X FTIR spectrometer equipped with a mercury-cadmium-teUmium detector are shown in Fig. 2.51. Because of strong backscattering by the PbS particles and, as a result, a small penetration depth of radiation, the transmission spectrum obtained from the powder squeezed between two plane-parallel KBr plates represents mainly the component /q that has passed by the particles (Fig. 1.22) and, hence, bears no information on the sample absorption. The DRIFTS and DTIFTS spectra of the PbS powder and the transmission spectrum of a mixture of PbS and KBr spectra are more informative. The distinct absorption bands of surface oxidation products at 1440, 1400, and 1200-1100 cm are assigned to lead carbonate, hydroxide, and sulfoxide [109], 

Mirabella (Ed.), Modem Techniques in Applied Molecular Spectroscopy, Wiley, New York, 1998, pp. 185-220. 

Spectrophotometry of Semiconducting Structures, Sovetskoe Radio, Moscow, 1975 (in Russian). 

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