## 3 Results and Discussion  
Figure 3 displays the XPS survey spectra of Ag-Au NPs before and after interaction with LCC. The surface composition determined from these spectra is presented in Table 1. These data show that the concentration of noble materials on the surface of the studied samples does not exceed 0.4 at. %. On this basis we conclude that the NPs were successfully deposited onto silicon substrate despite the fact that concentrations of metal NPs in initial solutions were small enough. The estimated concentration of metal colloids in initial water solution was about 0.3 \(\times\) 10\({}^{-6}\) M. On the other hand, the increasing of carbon concentrations supports the conclusion that LCC structures were also deposited. The high-energy resolved XPS Si 2p (Figure 4a) and O 1s-spectra (Figure 4b) of both samples show the main peak (in O 1s) corresponds to Si-O bond in SiO\({}_{2}\). At the same time  
Figure 3: XPS survey spectra of Ag-Au and (Ag-Au)@LCC. Si 2p spectra indicate that the main peak corresponds to Si-Si bond of substrate (99.4 eV) while the feature at 103 eV ascribed to a partial oxidation of the substrate. Further, we should note that an additional low-energy fine structure in the 528.2-531.3 eV energy range appears for (Ag-Au)@LCC. Adsorbed oxygen can contribute to spectral range near 531 eV, however, according to [37,38] the contributions of metal-oxygen bonds (the Ag-O and Au-O) are located at the indicated energy range. This means that a surface oxidation of both metal components in (Ag-Au)@LCC prepared by laser ablation in water could take place. To check this conclusion the high-energy resolved XPS Ag 3d and Au 4f spectra were analyzed (see Figure 5a,b). It emerged that the spectra of both components for (Ag-Au)@LCC nanoparticles show a two-peak structure. In details, XPS spectra of Ag 3d\({}_{5/2,3/2}\) (Figure 5a) shows lines at the binding energies of 366.7 and 372.6 eV. We should note that the Ag 3d\({}_{5/2}\) lineshape  
Figure 4: XPS spectra of Ag-Au and (Ag-Au)@LCC: (**a**) Si2p and (**b**) O 1s. Figure 5: XPS spectra of Ag-Au and (Ag-Au)@LCC: (**a**) Ag 3d and (**b**) Au 4f. Label “Au-shell ct” designates charge transfer between Au atoms and LCCs shell. between 366.7 and 368.2 eV could arise from Ag-O bonds (specifically, Ag 3d\({}_{5/2}\) located at 367.33 eV for AgO [37] and at 367.62 eV for Ag\({}_{2}\)O [39]). However, these additional lines cannot be attributed only to oxidation of (Ag-Au)@LCC nanoparticles since XPS Ag 3d lines in oxides have higher binding energies in XPS spectra than 366.7 eV peak. Earlier it was shown that this feature could arise from the formation of Ag-C bond in Ag@LCC NPs [40] and Ag NPs [41] and nanowires [42]. Moreover, we do not exclude that, during the second irradiation, a series of Ag or Au end-capped LCCs are also formed together to the Ag NPs encapsulated in carbonaceous shells [40]. On the other hand, the additional feature appearing at lower binding energy might hint of the electron transfer to Au. A similar picture could be seen in Au 4f spectra (Figure 5b) where the presence of a low energy band could be associated with Au and C atoms interaction because the similar peaks were observed in the Au 4f spectra of Au@LCC [43]. The lower-energy shift of Au 4f peak position is a known for metal nanoparticles (including Au) on various substrates [44; 45; 46; 47] due to strong metal-substrate interactions. It should be noted that some authors refer to the low-energy shift to negatively charged gold atoms organized in clusters [48]. [PERSON] et al. [49] associated the same shift of Au 4f binding energies for Au-Pd NPs (Au core-Pd shell) to an increase in the surface to volume ratio as the Au core became smaller. In our case we suggest that gold atoms located at NPs surface strongly interacted with LCC shell. For this reason, the gold atoms located on the NPs surfaces show a significant shift to lower binding energy while atoms located in the core of NPs show the peak position close to the Ag-Au alloy.