Utilization of surface Plasmon resonance band of silver nanoparticles for determination of critical micelle concentration of cationic surfactants

Highlights: • Spectroscopic and colorimetric detection of CMC using AgNPs probe. • The measured spectral shifts of SPR band have been utilized to determine CMC values for cationic surfactants. • Detection is based on the change of color of AgNPs colloidal solution at CMC. • The head group sizes of surfactants play an important role in the color formation of AgNPs colloidal solution. We have utilized surface Plasmon resonance (SPR) band sensitivity to surfactant concentration to investigate the critical micelle concentration (cmc) of CTAB, HY and CPB. The process is based upon an in situ formation of silver nanoparticles (AgNPs) through the reduction of silver ions (Ag⁺) by diethylene triamine (DETA) at 25 °C. In the presence of cationic surfactants, Ag⁺ ions can be reduced to AgNPs in a few minutes, accompanied by changes in intensity and wavelength of the SPR band. The spectral shifts of SPR band and the change of color have been used to determine CMC values of cationic surfactants.