FOURIER TRANSFORM INFRARED EXTERNAL REFLECTION STUDY OF MOLECULAR ORIENTATION IN SPONTANEOUSLY ADSORBED LAYERS ON LOW-ABSORPTION SUBSTRATES

Article abstract of DOI:10.1021/j100342a064

An infrared reflection absorption spectroscopy (IRAS) technique has been developed to study the structure of spontaneously adsorbed layers of ethyl xanthate (C2H5OCS2(1-) ion) on a semiconductor, cuprous sulfide (chalcocite), from aqueous solutions.Owing to the optical properties of the substrate, positive as well as negative absorption bands are observed in the recorded spectra of the same sample, depending on the angle of incidence and the polarization of the incident radiation.The spectroscopic study was performed on mono- and multilayer coverages of ethyl xanthate. generally good agreement has been obtained between experimental and theoretically calculated absorbance values for a model of the system investigated.The results show that the spectroscopic data obtained with the IRAS method make it possible to determine both the chemical nature and the structure of an adsorbed anisotropic layer at mono- and multilayer coverages on low-absorption substrates.The orientation of the individual molecular groups of adsorbed ethyl xanthate on cuprous sulfide and the chemical nature of the adsorbed species have been determined.The measurement conditions chosen for the IRAS studies of the adsorption layer on low-absorption substrates are also discussed.