Extended Data Fig. 6: SC spectrum of regular and deuterated oil nanodroplets.

a, SC spectra of 2% regular hexadecane nanoemulsion in water (blue solid) and scaled Raman spectra of pure water (orange solid). b, SC spectra of 2% d34-hexadecane nanoemulsion in water (blue solid) and scaled Raman spectra of pure water (orange solid). Their gaussian-fitted O-H regions are plotted in Fig. 2c,d. c,Water-perturbed, solute-correlated oil spectrum of d34-hexadecane oil droplets. While Raman-MCR spectroscopy has mostly focused on the water spectrum, the strategy should be general and thus extendable to the oil phase. We therefore measured water-perturbed interfacial oil spectrum with MCR (purple), and compared it to a pure d34-hexadecane (yellow). Although there is a narrowing of multiple peaks at the oil-water interface, the positions of the peaks are largely consistent. The largest difference is that the water-perturbed oil spectrum appears narrower, and the peak ratio of 2105 cm⁻¹ over 2196 cm⁻¹ is increased compared to bare oil, both suggesting the interfacial oil may be more ordered. Indeed, similar behavior is commonly observed in lipids at low temperature and more ordered phase. An increase in molecular order can also be understood by the fact that oil molecules tend to lie parallel to the interface with water, which has been reported elsewhere for hexadecane-water and other oil-water systems.