## 1 Introduction  
Over the past few decades, significant efforts have been devoted to integrating plasmonic nanoparticles (NPs) with macrocyclic molecules. This combination leverages the unique properties of both components: the localizeNerad surface plasmon resonance (LSPR) of metals like gold (Au) and silver (Ag) and the molecular recognition capabilities of macrocyclic molecules, aiming to create advanced nanoplatforms for biosensing, drug delivery, and chiral separation [1; 2; 3; 4; 5; 6]. The LSPR of Au and Ag NPs amplifies the electromagnetic field at their surface, allowing for highly sensitive, label-free detection of analyte molecules [7; 8; 9]. Since near-field enhancement diminishes exponentially with distance, the sensitivity of plasmonic detection is heavily influenced by the proximity of analyte molecules to the surface of the NPs [10]. Therefore, maintaining analyte molecules in close vicinity to the NP surface is crucial. Capping plasmonic NPs with macrocyclic molecules provides a versatile solution. The host-guest interactions (including hydrophobic association, van der Waalsforces, electrostatic attraction, and \(\pi\)-stacking interactions) [11; 12] effectively retain analyte molecules, being able to amplify their surface-enhanced Raman scattering (SERS) signals. Additionally, macrocyclic molecules exhibit good biocompatibility and stabilizing performance, while their cavity height of approximately 1 nm is ideal for entrapping molecules close to the plasmonic NP surface [13]. This proximity ensures optimal interaction with the enhanced electromagnetic field, significantly improving detection sensitivity and reliability. Among the various families of macrocyclic molecules used as capping agents for SERS substrates--such as pillararenes, calixarenes, and cucurbiturils--cyclodextrintrins (CDs) stand out due to their unique properties [14]. CDs are particularly favored for forming inclusion complexes because they contribute minimally to the background SERS signal, thanks to their low Raman activity [15; 16]. This attribute makes them ideal for enhancing the detection of target molecules without interference. CDs are also more cost-effective than other natural macrocyclic molecules, making them a practical choice for widespread application [17; 18; 19]. CDs come in three different types, \(\alpha\), \(\beta\), and \(\gamma\), based on the number of glucose units they contain. These types have internal cavity diameters ranging from approximately 5 A to 8 A, which allows them to form inclusion complexes with a wide variety of analytes [20; 21]. The versatility of CDs in accommodating molecules of different sizes, along with their economic and functional advantages, underscores their popularity and effectiveness in SERS applications. The synthesis of AuNPs capped with CDs involves several methods that can be classified into chemical and physical methods. Different chemical approaches have been developed to tailor AuNPs@CDs using the bond formed between Au and either S or O. In the first case, the synthesis involves using CDs possessing thiol groups (SH). CDs modified with thiol groups are particularly effective in forming stable AuNPs conjugates, mainly due to the strong bond between thiol groups and Au surface. One common approach is the post-synthesis modification, where SH-CDs are attached to the surface of pre-synthesized AuNPs. This process often involves replacing the original stabilizer on the AuNPs surface with SH-CDs, enhancing the AuNPs' stability and functionality [3; 22]. Another popular method is the one-pot synthesis, in which SH-CDs are introduced into the reaction, serving as stabilizers, to produce AuNPs@CDs in a single step [23; 24]. For CDs lacking thiol groups, such as native CDs, the synthesis generally involves a similar reduction process but without the specific thiol interaction. In this case, CDs act primarily as capping agents, stabilizing the AuNPs by the bond between the Au atoms and the oxygen in CDs.