Extended molar absorption analysis of confined states of water in reverse micelles using near-infrared spectroscopy

The properties of nanoscale water pools in reverse micelles (RMs) are significantly different from those of bulk water because of the influence of polar groups and spatial confinement. It was commonly accepted that water in RMs exists in two forms: interfacial water near the surfactant polar groups and core water in the central region away from the polar groups, however, it is difficult to detect two distinct forms. The near-infrared spectra of water inside the RMs formed by four surfactants were measured, and the spectra of bulk water-like core water were detected by an extended molar absorption analysis.