Identification of Al13 on the Colloid Surface Using Surface-Enhanced Raman Spectroscopy.

Al13 is the most active polymeric Al species responsible for coagulation at the solid-liquid interface, whereas the detection techniques for Al13 at the interface are currently limited. In this study, for the first time, the identification of Al13 on the silicon dioxide-based colloid surface was realized by using surface-enhanced Raman scattering (SERS), which is an ideal surface method sensitive for single-molecule detection. The high purity Al13 salts were prepared by an electrolysis procedure followed by precipitation or metathesis. Al13-Cln was determined to be feasible for the Raman detection as it exhibited more noticeable signals in comparison to Al13-(SO4)p and Al13-(NO3)m. The peak of Al13-Cln at 635 cm-1 could be the major characteristic peak of Al13, and the other two peaks at 300 and 987 cm-1 could be accessorial evidence for the identification. Further, the identification of Al13 adsorbed on the surface of Ag and gold-core/silica-shell colloids was confirmed by the SERS response at the above three wavenumbers with a higher signal-to-noise ratio than the normal Raman scattering. According to the least-squares fitting computed Raman spectra, each of the characteristic peaks was associated with specific vibrational modes.