## 3 Results and Discussion
### Nanoparticle Synthesis and Characterization
#### 3.1.2 Gold Nanoparticles Synthesis  
* Microwave-assisted synthesis  
Using our experience with synthesizing Ag colloids employing \(\beta\)-CDs as reducing and stabilizing agents, we proceeded with synthesizing Au colloids from chloroauric acid in an alkaline medium produced by using both sodium hydroxide and potassium carbonate. We prepared three 10 mL samples with an Au:\(\beta\)-CD molar ratio of 1:2, 1:1, and 1:5:1, respectively, in the presence of NaOH. These samples were placed in a microwave oven and irradiated. After approximately 60 s, the samples reached boiling and turned ruby red, indicating the formation of Au colloids, as confirmed by TEM images (Figure S8). The absorption spectra revealed a maximum of around 524 nm for all three samples (Figure 3a). For an Au:\(\beta\)-CD molar ratio of 1:2, the absorption peak was broad (FWHD of 48 nm) and of low intensity. Increasing the Au precursor amount in a more alkaline environment (pH = 11.2) resulted in a higher absorption while the FWHD did change slightly (46 nm). At an Au:\(\beta\)-CD molar ratio of 1:5:1 and a similar alkaline environment, the absorption peak intensity further increased, and it weakly broadened (FWHD of 52 nm) due to the higher  
Figure 4: UV-Vis spectra of Ag colloids synthesized at room temperature in an alkaline environment produced with K\({}_{2}\)CO\({}_{3}\) for 1:1 and 1:2 ratios of Ag:\(\beta\)-CD. All samples were diluted three times with double distilled water before the measurement. gold content. In all three cases, the AuNPs were spherical with an average diameter of around 20 nm. Similar to our approach with Ag colloids, we explored the possibility of using K2 CO3 as an alkaline medium instead of NaOH. We maintained the same proportions and conditions as those used for the Ag colloid (Figure 2a), substituting the Ag precursor with the Au one. For all four colloids, the maximum absorption occurred in the spectral range of 518-521 nm. The shift of the absorption peak toward shorter wavelengths indicates that the AuNPs are smaller than those formed with NaOH. TEM images show a relatively uniform size distribution of AuNPs, averaging about 10 nm with a quasi-spherical shape (Figure S9). The intensity of the absorption peaks is much lower compared with the previous two cases (Figures 2a and 5a). Additionally, Figure 5b demonstrates that the highest absorbance is achieved with the lowest concentration of Au precursor. This suggests that, under these conditions, not all Au ions are reduced, limiting the number and size of the formed AuNPs. ultrasonicator, operating at 30% of its maximum power. After approximately 10 min, the solution turned red, indicating the formation of AuNPs. Sonication was continued for 35 min more, while the UV-VIS spectra were acquired at 15, 30, and 45-min intervals to determine the optimal exposure time. By the end of the process, the solution's pH was 9.5. The absorption curves, shown in Figure 5c, reveal that even upon 15 min, the absorption peak of the AuNPs is well-defined, being located at 518 nm. After 30 min, there is a slight decrease in the absorption peak intensity and a shift to 516 nm. Prolonged ultrasonication results in a significant reduction of absorption peak intensity and an increased absorbance at higher wavelengths, suggesting the formation of larger structures. Thus, the optimal exposure time ranges from 15 to 30 min, with longer exposure adversely affecting the quality of the synthesized AuNPs. * Room temperature synthesis Adding K\({}_{2}\)CO\({}_{3}\) to a solution containing Au ions and \(\beta\)-CDs causes the solution to rapidly lose its color. For instance, at a concentration of 1 mM, chloroauric acid appears pale yellow. Within 1-2 min, after the addition of the \(\beta\)-CD, the solution becomes transparent, indicating the reduction of Au\({}^{3+}\) ions to Au\({}^{+}\) ions. Over time, at room temperature without external energy input such as heating or ultrasound, the solution transitions to blue, then purple, and eventually red after a few hours.