## 3 Results and Discussion
### Nanoparticle Characterization
This diminution showed an exponential correlation between the type and the hydrodynamic size form (R\({}^{2}\) = 0.999; Figure 3a). PdNPs alone showed a size 2120.33 \(\pm\) 112.53 nm, three times larger than PdNPs-PVP and 16 times larger than PdNPs-PVP-Q (Figure 3a). The size diminution with PVP addition in silver nanoparticles [55], antimony [56], or bismuth [57] has been shown. Surfactant and quercetin addition generated a diminution in size and zeta potential. The index of the interaction between colloidal nanoparticles is estimated by the zeta potential. Thus, this parameter measures the nanoparticles' capacity to agglomerate or its dispersion stability. Nanoparticles with a zeta potential larger than +30 mV or \(-\)30 mV normally are considered stable [55]. The addition of PVP or PVP-Q addition to PdNPs showed a change in the zeta potential (Figure 3b). PdNPs-PVP-Q showed the smallest value with a charge of \(-\)7.9 \(\pm\) 0.73 mV. In both attributes (hydrodynamic size and zeta potential), the quercetin contributes to the size of nanoparticles favorably. These results are coincident with the result shown by [PERSON] et al. [58]. However, this result is not consistent with the zeta potential increase from Sb\({}_{2}\)S\({}_{3}\)[56] or Bi\({}_{2}\)S\({}_{3}\)NPs [57], where the increase was related to the hydrodynamic size diminution. Two mechanisms have been reported for NP stabilization: (1) electrostatic stabilization, where the nanoparticles are repelled by the NPs' surface charge, and (2) steric stabilization, where NPs are coated by macromolecules, which generates repelling forces [13; 50]. X-ray diffraction analysis was performed to describe the crystallinity of the nanoparticles (Figure 4). PdNPs showed a centered cubic structure (fcc) with five pics at 40.1, 46.4, 67.9, 82.7, and 86.7 2-tetha, indicating the presence of (111), (200), (220), (311), and (222) planes. The PVP and quercetin addition in the nanoparticles caused a diminution in intensity compared to PdNPs alone (Figure 4b,c). However, such an addition does not change the NPs' crystallinity. Previous studies have reported that the addition of PVP to PdNPs showed no change in the NPs' crystallinity, only in the intensity [59]. Figure 3: Hydrodynamic size and potential zeta characterization. (**a**). Hydrodynamic size determination. (**b**). Potential zeta size determination. Both were determined in bidistilled water with a concentration of 300 ppm for each nanoparticle. To further confirm the incorporation of quercetin with PdNPs, we used FT-IR spectroscopy (Figure 5). Our results indicated that quercetin showed characteristic transmittance bands. The OH group stretching was detectable at 3406 and 3283 cm\({}^{-1}\), while the OH bounded to the phenol group was detected at 1379 cm\({}^{-1}\). The aryl group was detectable at 1666 cm\({}^{-1}\), and the C=C from the aromatic ring was found at 1610, 1560, and 1510 cm\({}^{-1}\). The C-H in aromatic hydrocarbon in the plane was detectable at 1317 cm\({}^{-1}\). whereas the C-H out of the plane was observed at 933, 820, 679, and 600 cm\({}^{-1}\). The C-O stretch in the aryl ether group was observed at 1263 cm\({}^{-1}\), while C-O stretching in the phenol was observed at 1200 cm\({}^{-1}\), and the C-CO-C stretch in ketone was observed in 1165 cm\({}^{-1}\) which has been reported as a band typical of quercetin [60]. Figure 4: X-ray diffraction of PdNPs synthetized alone (**a**), with PVP (**b**), or with PVP-Q (**c**). The PVP characteristic bands in the 1655 cm\({}^{-1}\) correspond to the C=O group. The bands stretching at 1492, 1460, and 1421 nm correspond to CH\({}_{2}\) deformation, the 1372 cm\({}^{-1}\) band corresponds to CH deformation and 646 N-C=O bands [61]. Quercetin used to load ZnO with PBA as a surfactant showed the successful load of quercetin into NPs [62]. Additionally, quercetin has been used to load silica NPs without the addition of surfactants, indicating the possibility of quercetin union without an intermediate [58].