Tham khảo tài liệu 'advanced biomedical engineering part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Semiconductor II-VI Quantum Dots with Interface States and Their Biomedical Applications 171 Fig. 26. Raman spectra of nonconjugated a and bioconjugated b 565 nm CdSe ZnS QDs Vega Macotela et al. 2010b . In nonconjugated CdSe ZnS QD samples 605N and 565N in the range 1050-4000 cm-1 a set of Raman peaks at 1214 1273 1326 1347 1413 1457 1613 1661 cm-1 and 2149-2430 2752 2880 2939 3061 and 3317-3380 cm-1 have been detected as well Fig. 27 and Fig. 28 . These Raman peaks and the small intensity Raman peaks revealed in Fig. 25a 837 860 1011 and 1039 cm-1 can be assigned to the vibrations of different groups of atoms in the organic amine NH2 -derivatized PEG polymer OH- CH2-CH2-O n-H covered the QD surface. There are 837 860 and 1661 cm-1 - PEG skeleton vibrations Kozielski et al. 2004 1011 and 1039 cm-1 - stretching vibrations of COH groups 1214 1273 1413 and 1457 cm-1 stretching vibrations of C-H bounds and deformation vibrations of C-H at 1326 and 1347 cm-1 Kozielski et al. 2004 Nakamoto 1997 1613 cm-1 - stretching vibrations of C C bounds and 2149-2430 cm-1 - stretching vibrations of CO or C-N groups Nakamoto 1997 symmetric and anti-symmetric stretching vibrations of CH CH2 or CH3 groups 2752 2880 2939 and 3061 cm-1 as well as the stretching vibrations of O-H and NH2 groups at 3317-3380 cm-1. To confirm that mentioned peaks related to PEG polymers the QDs without PEG polymer have been studied as well and actually these peaks have been not observed in Raman spectrum. The intensity enhancement of Raman lines related to the Si acoustic and optical phonons in the bioconjugated QD samples can be attributed to the surface enhanced Raman scattering SERS effect Aroca et al. 2004 Torchynska et al. 2007 2008 2009a . The surface electric field enhancement due to the realization of resonance conditions for the plasmon- phonon-or exciton-polariton resonances is the known effect in nanocrystals of polar materials Anderson 2005 . The stimulation of optical field near the interface
