Synthesis and Characterization of β-Caryophyllene-Capped Gold Nanoparticles

The synthesis of β-c-AuNPs was carried out exactly as described previously [50 (link)]. In brief, the reaction was carried out in a volume of 200 mL of deionized water by first dissolving 1 mM of HAuCl₄.3H₂O (pH 9.0) and stirring at 60 °C. A drop-wise solution of β-caryophyllene (1 mM) was added to the reaction mixture and stirred continuously at 60 °C. During the reaction, the color of the liquid changed from yellow to a deep wine-red. Furthermore, the nanoparticle synthesis was confirmed by measuring the UV-visible absorption spectra using a microplate reader (BioTek, Winooski, VT, USA) with the scanned absorption spectra ranging from 200 to 700 nm. A Fourier transform infrared spectrometer (FTIR, JASCO (FT-4100), Tokyo, Japan) was used to measure the ionic interaction in β-c-AuNPs. The Litesizer 500 was used to determine the size and zeta potential of β-c-AuNPs (Anton Paar, GmbH, Graz, Austria). An XRD (X-Ray Diffractometer, Rigaku (Japan), Ultima IV) was used to determine the crystalline nature of β-c-AuNPs.