Distance‐dependent Enhancement in Raman Spectroscopy Probed by Conjugated Molecules with Different Molecular Lengths

Abstract

In this study, the distance-dependent enhancement effect in surface-enhanced Raman scattering (SERS) was explored with molecules bearing different lengths of conjugated double bonds. These conjugated molecules were synthesized utilizing the diazotization-coupling reaction allowing a thio group on one end and a nitro group on the other end. The thiol group allows the probed molecule to chemisorb on the surface of silver nanoparticles (AgNPs). The opposite end of each molecule contains a nitro group, which gives an intense SERS signal to show a fair and accurate comparison of the effect of chain length. The obtained SERS intensities were correlated with the chain lengths of these synthesized molecules, which ranged from 0.6 to 2.0 nm between the nitro and thiol groups. Based on these results, the electromagnetic field effect was mainly responsible for the signal enhancements in SERS measurements. Also, the obtained signals were exponentially decayed due to the distances of the surface of AgNPs. Based on the SERS intensities of the conjugated molecules, the contribution of CT effect to SERS for these examined molecules were limited.

Bovine Serum Albumin Conjugated Gold-198 Nanoparticles as Model To Evaluate Damage Caused by Ionizing Radiation to Biomolecules

“…By comparing the results of fluorescence and Raman spectroscopy after irradiation with 0.1 kGy of γ radiation, the fluorescence spectrum indicated that only about 50% of chromophore species were destroyed, whereas SERS spectrum was consistent with almost complete decomposition since almost no signal associated with BSA chromophores could be detected. Accordingly, SERS is considered for analytical purposes but its limitations especially for samples with angular or spatial dependences. − In our case, it indicates that chromophore groups next to surface are being destroyed preferentially to those farther from the surface of gold nanoparticles.…”