Investigation of the adsorption of gaseous aromatic compounds at surfaces coated with heptakis(6-thio-6-deoxy)-beta-cyclodextrin by surface-enhanced Raman scattering

Heptakis(6-thio-6-deoxy)-beta-cyclodextrin (TCD) was prepared and chemisorb ed at the surface of rough silver substrates for surface-enhanced Raman sca ttering (SERS). The enhanced adsorption of methyl orange and the stability of its azo form at the TCD-coated substrates proved the capability of the i mmobilized TCD to form inclusion complexes with organic guest molecules. Th is complexation was used for the detection of aromatics in the gas phase. T oluene, ethylbenzene, m-xylene, chlorobenzene, and m-dichlorobenzene were s trongly adsorbed at the TCD-coated substrates, thus making possible the det ection of low concentrations, as for example 15 ppm of m-dichlorobenzene. B enzene was weakly adsorbed and detectable in high concentrations only. Sinc e the strongly adsorbed aromatics desorb very slowly, TCD-coated substrates may be applicable for the detection of slowly changing concentrations or a s integrating sensors in the surveillance of chemical exposures. The capabi lity of immobilized TCD to adsorb also polycyclic aromatic hydrocarbons was demonstrated using naphthalene.