## 4 Conclusions  
We demonstrated experimentally that Ag and Au colloids can be synthesized using \(\beta\)-CDs as a reducing and capping agent in an alkaline environment. Moreover, alkalinity can be induced by salts like K\({}_{2}\)CO\({}_{3}\) without the need for harsh bases, so we can say that the proposed synthesis methods are green. By replacing NaOH with K\({}_{2}\)CO\({}_{3}\) we were able to increase the size of Ag NP from <10 nm to around 20 nm. The CD-reduced colloids are, in general, less polydisperse compared with classical colloids; however, their sizes cannot be easily changed. As a general observation increasing the CDs concentration reduces the sizes of the colloids. In the case of ultrasound-assisted synthesis, the ultrasound irradiation time is a more sensitive parameter from the point of view of the colloid stability as longer irradiation times lead to sample aggregation. Following the time evolution of the UV-Vis spectra, we noticed an increase in the plasmonic peak even 1 h after the irradiation. However, the ultrasound-synthesized colloids are less stable compared with the microwave and room temperature methods, yielding colloids with more polydisperse sizes. Figure 13: SERS spectra of 1 mM R and S propranolol on \(\beta\)-CD-capped AuNPs synthesized in ultrasound using 20 mM KI as an aggregating agent. We succeeded in synthesizing both Ag and Au colloids at room temperature with larger (20 nm) and more polydisperse colloids in the case of Ag and smaller (11-12 nm) quasi-spherical and monodisperse ones in the case of Au. All synthesized colloids present SERS activity with higher SERS signals for the larger ones. The CD-capped colloids can detect hydrophobic molecules, which are less prone to provide an effective SERS signal. Moreover, in the case of propranolol, a molecule known to form inclusion complexes with \(\beta\)-CDs, we demonstrated that the inclusion leads to the discrimination between its R and S enantiomers with stronger intensity SERS peaks for R-propranolol. By complexation with CDs, the SERS landscape of propranolol changes with a lower contribution from the naphtyl group. Overall, our results suggest that CD capping of both Ag and AuNPs creates nanostructures with versatile and useful properties in many fields. The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app14188215/s1](https://www.mdpi.com/article/10.3390/app14188215/s1)]([https://www.mdpi.com/article/10.3390/app14188215/s1](https://www.mdpi.com/article/10.3390/app14188215/s1)), Figure S1: TEM images or citrate reduced AuNPs and their UV-Vis spectrum; Figure S2: AgNPs obtained by microwave synthesis for an Ag:\(\beta\)-CD molar ratio of 1:2 at pH 10 obtained with NaOH. Figure S3. TEM images of AgNPs obtained by microwave synthesis for an Ag:\(\beta\)-CD molar ratio of 1:4 at pH 10.5 obtained with K\({}_{2}\)CO\({}_{3}\); Figure S4. Normalized UV-Vis absorption spectra of Ag colloids reduced with high concentration \(\beta\)-CD in potassium carbonate alkaline medium; Figure S5. TEM images of AgNPs obtained by microwave synthesis for an Ag:\(\beta\)-CD molar ratio of 1:40 and 5 mM of K\({}_{2}\)CO\({}_{3}\); Figure S6. TEM images of AgNPs obtained by microwave synthesis for an Ag:\(\beta\)-CD molar ratio of 1:40 and 2.5 mM of K\({}_{2}\)CO\({}_{3}\); Figure S7. TEM images of AgNPs obtained at room temperature and their size distributions; Figure S8. TEM images of AuNPs obtained by microwave synthesis with NaOH; Figure S9. TEM images of AuNPs obtained by microwave synthesis with K\({}_{2}\)CO\({}_{3}\); Figure S10. TEM images of AuNPs obtained at room temperature, left undisturbed for 12 h for Au:\(\beta\)-CD; Table S1. Main FTIR peaks of beta CD and their assignments; Figure S11. SERS spectrum of Rodamine 6G using \(\beta\)-CD reduced Ag NPs at room temperature; Table S2. Experimental and simulated vibrational bands in the Raman spectrum of propranolol. Conceptualization, C.M.L. and R.-I.S. ; methodology, V.T. and C.I. ; software, C.M.L. and V.T. ; validation, C.I. and C.M.L.