Adsorption Orientation of Fuchsine Basic on Negatively and Positively Charged Silver Colloid Particles

Both negatively and positively charged colloids (for short, PCS and NCS) with nano-silver particles were prepared. TheNCSwaspreparedbyusing tannic acid asthe reducing agent forAgNO3 and the PCS was prepared by using trisodium citrate as the reducing agent forAgNO3. The surface charge of these two kinds colloidal silver particles was validated by electrophoresis experiment. Surface enhanced Raman scattering (SERS) from fuchsine basic molecules on the two colloids of nano-silver particles were recorded respectively and compared with each other. The resultsshow that there are some obvious differences on the SERSspectrawhen the molecule was adsorbed on the NCS and PCS. On PCS, the in-plane vibrational modes ring skeletal vibration 968cm-1, ring C-H bend 1178 cm-1, N-phenyl stretching 1370 cm-1, Ring C=Cstretching 1588 cm-1were enhanced.On theother hand, on NCS, both the inplane 348, 914, 968, 1178, 1291, 1370, 1520, 1588 cm-1and out-of-plane 1520, 832, 759, 736,423 cm-1were enhanced. It indicates that the fuchsine basic molecule adsorbs on the two kinds of silver surface in different configuration. The molecule adsorbs on the PCS surface vertically, however tilted on the NCS surface.