NEAR INFRARED SURFACE ENHANCED RAMAN SCATTERING OF HALATE IONS

Surface enhanced Raman scattering (SERS) of halate ions in silver colloids is studied by near infrared (NIR) laser excitation.Ions of ClO － 3 and BrO － 3 in silver colloids give rise to SERS bands at about 226 and 158cm －1 ,respectively while IO － 3 ions on colloidal silver surface result in two Raman bands at about 750 and 334cm －1 .These results indicate that the interactions of ClO － 3 and BrO － 3 ions with silver surface are through their lone pair electrons of Cl and Br.Nevertherless,IO － 3 ions bond to silver surface through their negatively charged O － .The interaction strength of halate ions with silver are measured to be BrO － 3 >ClO － 3 ≈IO － 3 .The enhancements of the Raman modes of pyridine caused by addition of halate ions increase in the order ClO － 3 － 3 － 3 .The enhancement mechanisms in NIR SERS are discussed.