SERS Characterization of the Indocyanine-Type Dye IR-820 on Gold and Silver Nanoparticles in the Near Infrared
Table 1
Band wavenumber (in cm−1) assignment for Raman, SERS (on Au and Ag nanoparticles), and infrared spectra of IR-820. = 1064 nm.
Theoretical/cm−1
Infrared /cm−1
Raman solid/cm−1
Raman solution/cm−1
SERS (Ag)/cm−1
SERS (Au)/cm−1
Assignment*,**
308
—
299
300
300
298
δ(CCC)alk,oop
359
—
—
353
353
351
δ(CCC)alk,oop
392
—
—
371
374
370
δ(CCC)alk,oop + δ(CCC)conj
461
462
450
449
451
452
δ(CCC)alk,oop
481
510
503
474
476
478
δ()sim + (CS)
520
—
515
515
514
511
δ(CCC)F,G
595
—
588
—
590
589
δ(CCC)A,B,C
639
618
—
—
—
—
δ(CCC)A,B,C
654
—
—
646
647
645
δ(CCC)rings + δ(CCC)conj
691
672
674
675
675
676
(CS)
718
—
702
701
701
699
δ(CH)rings,oop
741
722
725
725
726
724
δ(CH2)r,alk
768
—
751
751
751
751
δ
802
786
790
789
792
790
(CC)alk
815
811
811
—
—
—
δ(CH)conj,oop + δ(CH2)r,D
840
837
837
837
838
837
δ(CCC)E,F,G
874
860
862
863
863
863
δ(CCC)E,F,G + δ(CCC)conj
911
893
894
897
897
897
δ(CCC)A,B,C + δ(CH2)t,D
943
934
940
940
944
941
δ(CH)conj,oop
1011
1012
1011
1016
1014
1015
(CC)D
1046
1051
1059
—
1054
—
(CC)A
1072
—
—
1064
1067
1063
δ(CH2)r,alk + (CC)D
1161
1118
1114
1122
1122
1122
δ(CH)A,B,F,G
1174
1141
1146
1147
1148
1144
δ(CH)rings
1208
1171
1166
1171
1167
1169
δ(CH)A,B,F,G + δ(CH2)t,alk,D + (SO)
1223
—
1205
1209
1207
1205
(CC)conj
1236
1237
1235
1238
1235
1236
δ(CH)A,B,F,G
1274
1273
1264
1265
1265
1263
δ(CH)conj + δ(CH2)t,D
1375
1375
1361
1361
1364
1363
δ(CH2)t,alk + δ(CH)conj
1392
1392
1397
1399
1398
1400
δ(CH)conj + δ(CH2)w,alk + (CN)
1463
—
—
1415
1414
1415
δ(CH)conj + (CC)conj
1482
1446
1446
1447
1445
1446
δ(CH)rings
1504
1463
1462
1464
1465
1463
δ(CH2)sc,alk + δ
1562
1523
1521
1522
1522
1523
(CC)A,B
1573
1549
—
—
—
—
(CC, CN)conj
1603
1575
1576
1575
1574
ν(CC)conj
1640
—
1595
1595
1596
1596
(CC)F,G
1666
1626
1625
1626
1625
1626
(CC)A,B
: stretching; δ: bending; u: umbrella; sc: scissoring; t: twisting; r: rocking; w: wagging; conj: conjugated chain; alk: alkyl chain; A, B, C, D, E, F, and G: rings, referred to in Figure 2; oop: out-of-plane. **Assignment based on the visual inspection of vibrational eigenvectors calculated by DFT [B3LYP/6-311G(d,p)] and compared to the assignments from [36].
