## 4 Antifungal Mechanism
### Raman Spectroscopy Analysis
#### 4.2.2 Raman Spectroscopy Analysis of PEI-AuNP@Van-Treated Conidia of _A. fumigatus_  
The Raman spectra of the PEI-AuNP@Van-treated, voriconazole-treated, and untreated conidia of A. fumigatus are shown in Figure 8b, and detailed spectrum assignments are shown in Table S1 (Supplementary File). The untreated conidia exhibited several weak intensity peaks between wave numbers 400 and 1200 cm\({}^{-1}\); and a broad and intense peak was observed at 1345 and 1590 cm\({}^{-1}\), as shown in Figure 8(bi). The peak assignments can be made based on previously studied biomolecules as follows: 657 cm\({}^{-1}\) (out-of-plane bending of OH in guanosine/tyrosine), 743 cm\({}^{-1}\) (CH\({}_{2}\) deformation), 791 cm\({}^{-1}\) (uracil), 872 cm\({}^{-1}\) (in-plane bending of CCO in the glucosyl ring), 909 cm\({}^{-1}\) (stretching in the pyrenoid ring and vibration in CH\({}_{2}\)), 1000 cm\({}^{-1}\) (C-C aromatic ring stretching/breathing in phenylalanine and galactomannan), 1032-1062 cm\({}^{-1}\) (C-C stretching in phospholipids and chitin +C-N stretching), 1126 cm\({}^{-1}\) (C-O-C of unsaturated fatty acids in lipids and galactomannan), and 1152 cm\({}^{-1}\) (C-O ring, aromatic amino acids in proteins). A broad-spectrum band observed from 1200 to 1650 cm\({}^{-1}\) was associated with the structural component of a complex polysaccharide and the protein fingerprint of the conidial cell wall in _A. fumigatus_. These features can be assigned to chitin, amide III (random), C-H deformation, galactomanan, CH\({}_{2}\) deformation, C=C stretching, COO symmetrical stretching, amide II, and COO asymmetrical stretching. These spectral bands indicate the intact structure of the conidia.  
Similarly, the voriconazole- and PEI-AuNP@Van-treated conidial Raman spectra were recorded, and chemical bonds were assigned to these features. Except for a few peaks, most of the spectral peaks were identical to those of the voriconazole- and PEI-AuNP@Van-treated conidia (Figure 8(bii,biii)). The bands were assigned as follows: 405 cm\({}^{-1}\) (trutose ring of carbohydrates) and 489 cm\({}^{-1}\) (C-1-O-C-4 glucoside bond in chitin). Along with overlapping bands, a few shifts were observed in both spectra: 727 to 735 cm\({}^{-1}\) (cytosine and uracil) and 808 cm\({}^{-1}\) shifted to 805 cm\({}^{-1}\) with weakened intensity (antisymmetric stretching in OPO phosphodieser), indicating structural changes in the cell wall component. Furthermore, a band at 1041 cm\({}^{-1}\) was observed for voriconazole; the spectrum of the PEI-AuNP@Van-treated A. fumigatus conidia (Figure 8(aii,aiii)) was similar to that of the _A. flavus_ conidia, with a slight shift. However, the spectrum of PEI-AuNP@Van-treated conidia was lower than that of the voriconazole-exposed conidia. The spectra of the PEI-AuNP@Van-treated conidia showed significant differences. For example, extra bands at 1127 and 1199 cm\({}^{-1}\) (=C-O-C= unsaturated fatty acids within lipids, galactomannan, and chitin) were observed when compared to the spectrum of voriconazole-treated conidia (Figure 8(bii,biii)). This observation indicated a difference in the modes of action of voriconazole and PEI-AuNP@Van at the molecular level. However, the band at 1204 cm\({}^{-1}\) (in-plane bending in the OH---O +, vibration in C-C, vibration in C-O, and deformation of CH\({}_{2}\)) was not observed in the PEI-AuNP@Van-treated conidia, again confirming the differences in the mode of action.