Drying-induced inversion of circular dichroism spectra of thioflavin T adsorbed on TEMPO-oxidized cellulose nanofibers

Abstract The circular dichroism (CD) spectra of an achiral cationic dye molecule, thioflavin T (ThT), adsorbed on TEMPO-oxidized cellulose nanofiber (CNF) suspended in an aqueous solution exhibited the positive exciton coupling like CD spectra, indicating the right-handed helicity of the fiber. Interestingly, a spontaneous drying of the aqueous suspension inverted the sign of the CD spectra completely and showed a negative exciton coupling like CD spectra, suggesting the change of the chiral nano-environment of ThT from a right-handed twisting single cellulose nanofiber in water to the left-handed liquid crystalline aggregates of CNF by drying. This phenomenon demonstrated that the induced CD spectra of ThT can be a sensitive probe of the helical change of CNF conformations.