## 3 Results and Discussion
### Nanoparticle Synthesis and Characterization
#### 3.1.1 Silver Nanoparticles Synthesis
We examined how the alkaline environment affects the formation of Ag colloids using potassium carbonate (K\({}_{2}\)CO\({}_{3}\)), a salt from a strong base and weak acid, which creates an  
Figure 1: UV-Vis absorption spectra of Ag colloids reduced with \(\beta\)-CD in alkaline medium and exposed to a microwave field (**a**) for different Ag:\(\beta\)-CD molar ratios; (**b**) with increasing alkalinity of the synthesis medium for different Ag: \(\beta\)-CD molar ratios; (**c**) for Ag:\(\beta\)-CD molar ratio of 3:1 obtained at various intervals: immediately after synthesis and two weeks later; and (**d**) for Ag:\(\beta\)-CD molar ratio of 1:2, achieved by reducing microwave power and extending irradiation time. alkaline environment. Two sets of colloids were prepared with Ag:\(\beta\)-CD molar ratios of 1:2 and 1:4: one with 10 mM K\({}_{2}\)CO\({}_{3}\) (pH = 10.5) and another with 5 mM K\({}_{2}\)CO\({}_{3}\) (pH = 10). The UV-Vis curves (Figure 2a) were similar to those with NaOH, showing a plasmonic maximum at 404-408 nm, suggesting reduced polydispersity. The plasmonic maximum shifted to longer wavelengths with a 1:4 Ag:\(\beta\)-CD ratio compared with 1:2. Over time, the 1:2 samples showed a decrease in the absorption maximum and a new peak around 500 nm, indicating colloid aggregation. TEM analysis showed that the 1:4 ratio produced quasi-spherical AgNPs with diameters of 18-20 nm and reduced polydispersity (Figure S3). Replacing NaOH with K\({}_{2}\)CO\({}_{3}\) affects the size of the NPs, resulting in larger NPs. We further increased the \(\beta\)-CD concentration tenfold to study its impact on synthesis, using Ag:\(\beta\)-CD ratios of 1:20 and 1:40 with K\({}_{2}\)CO\({}_{3}\) concentrations of 10 mM and 5 mM. The absorption curves (Figure S4) show similar plasmonic maxima at 398-404 nm with comparable FWHM widths. The blue shift in absorption maxima suggests smaller synthesized AgNPs, likely due to \(\beta\)-CD reducing NP growth after nucleation and inhibiting crystal growth on silver cores. Another reason could be a change in the refractive index due to \(\beta\)-CD. TEM images for a 1:40 Ag:\(\beta\)-CD ratio at 5 and 2.5 mM K\({}_{2}\)CO\({}_{3}\) (Figures S5 and S6) show well-separated quasi-spherical AgNPs, with some clustering possibly due to drying on the TEM grid. * Ultrasound-assisted synthesis  
Figure 2: UV-Vis absorption spectra of Ag colloids reduced with \(\beta\)-CD in alkaline medium and exposed to a microwave field (**a**) for different Ag:\(\beta\)-CD molar ratios and K\({}_{2}\)CO\({}_{3}\) amount; (**b**) for Ag:\(\beta\)-CD molar ratio of 1:2 obtained at various intervals: immediately after synthesis and 7 days later; (**c**) for Ag:\(\beta\)-CD molar ratio of 1:1 exposed to ultrasonication; and (**d**) for Ag:\(\beta\)-CD molar ratio of 1:1 at room temperature for 24 h.  
Furthermore, different other synthetic routes have been explored aiming to produce \(\beta\)-CD-capped AgNPs. In this line, the microwave field has been replaced by an ultrasonic field to synthesize AgNPs in the presence of \(\beta\)-CDs. For this purpose, a 50 mL solution was prepared with a molar ratio of Ag:\(\beta\)-CD of 1:1 and 8 mM K\({}_{2}\)CO\({}_{3}\). The solution was subjected to ultrasound irradiation using a 200 W tip ultrasonicator at 40% of its maximum power. After approximately 10 min of sonication, the solution developed a brownish-yellow color, and the UV-Vis spectrum showed a plasmonic absorption maximum at around 414 nm (Figure 2c). It has been observed that, in contrast to the microwave synthesis method, synthesis in an ultrasonic field generates larger and more polydispersed Ag colloids. These Ag colloids can potentially produce more intense SERS spectra due to their size and the high intensity of the electromagnetic field in the hot spots, as previously discussed. While trying to optimize the ultrasonication time, we notice that there is time evolution in the UV-Vis spectrum of the sample.