Chemiluminescence Produced in Saccharides by Cold Plasmas

Abstract

Cotton cellulose and other saccharides varying in molecular size and in type of glucosidic linkage were treated with cold plasmas generated by radiofrequency (rf) radiation (13.56 MHz). Plasma treatment produced reactive centers on all compounds, and activated samples were capable of producing chemiluminescence (CL). CL was greatest for long-chain structures. Subsequent immersion of plasma-activated compounds in either CHCl₃/CH₃OH, or the 2:1 v/v mixed-solvent system (CHCl₃/CH₃OH) increased CL significantly, with the latter solvent and the large molecules exhibiting the greatest effect. Reagents that caused an increase in CL reduced intensity of the ESR (electron spin resonance) signal, indicating a possible dependence of CL on the decay of free radicals formed during plasma treatment. CL quenched by nitrogen gas was partially regenerated when nitrogen was exchanged with oxygen. CL decay curves showed an initial fast rate followed by a slower one and especially in case of large molecules indicated that at least two different excited states were responsible for observed CL. Consideration of molecular structures of saccharides in relation to CL and to previously reported changes in ESR, IR, and ESCA spectra leads to the conclusion that the glucosidic bond is the primary site of free-radical formation.