*3.2. Raman and SERS Analysis*

Preliminary Raman analyses were performed directly on the samples focusing on dye spots or particles. However, the fluorescence background did not allow acquiring meaningful spectra. The collection of spectra at the highest intensity of the laser was attempted, but this only resulted in degradation of the sample with the formation of amorphous carbon or in the individuation of signals of the cellulose from the stubbons (Figure S6, Supplementary Materials).

With respect to the SERS spectra obtained for sample D816-4, it was possible to distinguish some common characteristic peaks (Figure 4, top). In particular, in most spectra, two broad bands around 461 and 477 cm−<sup>1</sup> are observable, while more defined peaks appear at 622, 680, and 735 cm<sup>−</sup>1. At higher wavenumbers, two peaks are observable at 1004 and 1049 cm<sup>−</sup>1, and other bands are distinguishable at 1213, 1255, 1301, 1329, 1364, 1436, 1461, 1484, 1509, 1565, 1577, 1582, 1601, 1623, and 1646 cm<sup>−</sup>1. These signals change in intensity and width in the different spectra.

All the spectra of the D816-9 sample (Figure S7, Supplementary Materials) present peaks at 452 (shoulder), 479, 680, 1002, 1049, 1207, 1447, 1485, 1578, and 1623 cm−1. It is interesting to notice that several bands observed for the D816-9 sample are also present in the spectra of the D816-4 sample.

In the case of sample D816-7, instead, the acquired spectra (Figure 5, top) present high reproducibility: there are peaks at 436, 457, 479, 530, 620, 644, 677, 693, 732, 761, 804, 827, and 918 cm<sup>−</sup>1, and defined signals at around 1030, 1176, 1221, 1298, 1364, 1399, 1429, 1476 (shoulder), 1530, 1586, and 1621 cm−<sup>1</sup> are clearly observable. In two spectra, further sharp bands are distinguishable at 546, 601, 1488, and 1576 cm<sup>−</sup>1.

**Figure 4.** Comparison of SERS spectra obtained for the D816-4 (top) and D817-2 (bottom) samples. Some peak wavenumbers are evidenced for clarity. The spectrum of sample D817-2 presents a clear correspondence with Rhodamine B SERS spectrum [50] (literature spectrum not reported in the image).

**Figure 5.** Comparison of SERS spectra obtained for the D816-7 (top) and D817-4 (bottom) samples. Some peak wavenumbers are evidenced for clarity. The spectra of samples presents a clear correspondence with the SERS spectra of Malachite Green [44,46] (D816-7) and Crystal Violet [44,46,54] (present in both the samples, see Discussion; literature spectra not reported in the image).

The SERS spectra obtained for D816-5 sample present a good reproducibility, even if their relative intensities can change in the different spectra. In most of them, peaks at 479, 656, 691, 733, 1139, 1225, 1300, 1340, 1443, 1458, 1585, and 1628 cm−<sup>1</sup> are present. In some spectra, further peaks can be identified: one spectrum presents bands at 434, 518, 570, 716, 810, 1001, 1207, and 1315 cm<sup>−</sup>1, which result generally sharper than the above-mentioned ones (Figure 6, top), while in another spectrum, intense signals at 798, 1404, and 1539 cm−<sup>1</sup> are observable. For the D816-15 sample, the spectra (Figure 6, bottom) present a general reproducibility, even if, also in this case, change in relative intensities are observed; the main spectral features are at 422, 440, 479, 519, 562, 593, 679, 717, 813, 857, 914, 1003, 1033, 1047, 1130, 1183, 1209, 1252, 1323, 1335, 1445, 1458 (shoulder), 1531, 1586, and 1627 cm−1. Some similarities with the spectra of sample D816-5 are evident.

**Figure 6.** Comparison of SERS spectra obtained for the D816-5 (top) and D816-15 (bottom) samples.

About the samples from S¯ıta puppet, the SERS spectra acquired show a great repro- ¯ ducibility. For the D817-2 sample, all the spectra present distinguishable peaks at 589, 622, 634 (shoulder), 661, 726, 737, 768, 1050, 1129, 1185 (shoulder), 1197, 1279, 1345 (shoulder), 1362, 1437, 1471, 1510, 1530, 1578, 1598, and 1649 cm−<sup>1</sup> (Figure 4, bottom). The SERS spectra of the D817-4 sample (Figure 5, bottom), instead, present reproducible bands at 423, 443, 530, 570, 622, 636, 665, 732, 745 (shoulder), 760, 802, 834 (shoulder), 914, 944, 977, 1124, 1181, 1217, 1298, 1345 (shoulder), 1376, 1444, 1473, 1524, 1533, 1565, 1589, and 1621 cm−1. The general pattern of this spectra presents high similarity with the spectra obtained for the D816-7 sample.
