## 3 Results and Discussion
### Nanoparticle Synthesis and Characterization
#### 3.1.3 Characterization of the Coating and Dynamic Light Scattering (DLS)  
To prove the decoration of Au/ AgNPs surface with \(\beta\)-CDs, FTIR spectroscopy was employed. Before measurement, the colloids were centrifuged at approximately 16,000\(\times\)\(g\) to separate the NPs from their synthesis environment. The supernatant was removed and  
Figure 6: (**a**) TEM image of AuNPs synthesized at room temperature using 0.5 mM HAuCl\({}_{4}\), 1 mM \(\beta\)-CD, and 10 mM K\({}_{2}\)CO\({}_{3}\) and (**b**) their size distribution with mean and standard deviation.  
replaced with double-distilled water (resistivity \(>\) 18 M\(\Omega\cdot\)cm). This process involved redesign by sonication and was repeated two times. From the final suspension, 2-4 \(\mu\)L were deposited on the diamond crystal of the FTIR spectrophotometer. Upon water evaporation, the IR spectrum was recorded and compared with the spectrum of natural \(\beta\)-CDs.  
Figure 7 illustrates the results of FTIR analysis for gold colloids produced under different conditions, including microwave irradiation, ultrasonication, and room temperature, using \(\beta\)-CDs as a reducing agent. The FTIR spectra confirm the presence of \(\beta\)-CDs on the colloid surfaces, as indicated by identifying characteristic vibration bands corresponding to \(\beta\)-CD.  
For \(\beta\)-CD, we obtained the main vibrational peaks as those reported in the literature, and their assignments are provided in Table S1 [43]. In the case of the NPs capped with CDs, there is a remarkable similarity between the spectra regardless of the synthesis method. It is well known that the spectra of NPs alone are featureless and indicate only a flat baseline. Both the spectral features were almost similar; however, there are variations in the peak position as well as intensities, corroborating the occurrence of CDs as an indispensable constituent of the NPs. The observed shifts for the peaks of the Au NPs compared with those of \(\beta\)-CDs were explained because of their interaction with the particle surface [27]. It was also speculated that the hydroxyl groups of CD may act as the reducing moieties for the reduction of metallic ions, and they were self-oxidized into carboxylic acid, which may also provide efficient capping on the surface of the NPs and the peaks recorded at 1645 cm\({}^{-1}\) and 1430 cm\({}^{-1}\) might be assigned to carboxylate ions [34]. Similar spectra were obtained in the case of \(\beta\)-CD-mediated synthesis of AgNP.  
The DLS for the CD capped AuNPs are presented in Figure 8.  
The DLS of CD-reduced AuNPs using a microwave-assisted synthesis (Figure 8a) presents a major peak corresponding to a diameter of 22.5 nm, slightly higher than the diameter resulting from TEM. In the case of ultrasound-assisted synthesis, a first maximum appears at around 16 nm but a second one was recorded at around 100 nm. The ultrasound-assisted synthesis yields NPs with polydisperse sizes and the colloidal solution less stable as compared with the other two methods. In the case of room temperature synthesis, the mean size of the colloids is around 19 nm. A second, much smaller maximum can also be noticed at around 300 nm. The DLS data correlate with the other observations made on the colloids, which show that in the ultrasound-assisted synthesis, the colloids are less stable, more polydisperse, and have the tendency to aggregate.  
Figure 7: The FTIR spectra of beta-cyclodextrintrin and AuNPs reduced with beta-cyclodextrintrin in an alkaline environment produced with K\({}_{2}\)CO\({}_{3}\) at room temperature (RT) with ultrasound (US) or microwave (MW) irradiation.  
The zeta potential was measured for the colloids synthesized in microwaves with values of \(-42.5\) mV at pH 9.5 the pH after the synthesis, decreasing slightly to \(-40.1\) at pH 7.5 and \(-36\) mV at pH 4. This intense negative charge explains the stability of these colloids.