## 1 Introduction  
Glasses doped with noble metal nanoparticles are a fascinating group of materials. The presence of nanoparticles in the glass matrix can significantly affect the optical properties of a material [1]. One of the most known effects of adding nanoparticles is the ability to control the optical properties of the material or even enhance the luminescence properties of rare-earth (Re) ions, which can lead to applications, e.g., in LEDs. The presence of Ag nanoparticles in the glass matrix can lead to the occurrence of localized surface plasmon resonance (ISPR) phenomenon [2]. LSPR occurs when light interacts with nanoparticles smaller or similar in size to the incident light wavelength. As a result, the electrons of the conduction band oscillate coherently, creating surface plasmonsthat propagate along the metal-insulator boundary as electromagnetic waves [3]. The LSPR results in enhancement of the electric field around the nanoparticle and its optical absorption, which is maximal at the plasmon resonant frequency. If Re ions are embedded in glass, and some of their energy levels are resonant with the plasmons, an enhancement of their luminescence properties can occur [4]. The formation of Ag nanoparticles can be obtained via a controlled crystallization process of glass using adequate heat treatment (HT) parameters, such as time and temperature [5]. The crystallization of nanoparticles in the glass matrix can occur slightly above the glass transition temperature (Tg) but lower than the first crystallization peak (Tc). In this temperature region, it is likely that silver ions can easily diffuse through glass, changing its valence state due to the one-step reduction process (Ag\({}^{+}\) + 1e\({}^{-}\) \(\rightarrow\) Ag\({}^{0}\)), and form nanoparticles via Ostwald ripening [3; 5]. The formation of Ag nanoparticles in an amorphous matrix through thermal annealing has been described, in various glass compositions, such as Bi\({}_{2}\)O\({}_{3}\)-SiO\({}_{2}\)-Ga\({}_{2}\)O\({}_{3}\)-Tm\({}_{2}\)O\({}_{3}\)-AgNO, TeO\({}_{2}\)-BaO-Bi\({}_{2}\)O\({}_{3}\), bismuth-germanate and K\({}_{2}\)O-B\({}_{2}\)O\({}_{3}\)-Sb\({}_{2}\)O\({}_{3}\) glasses [5; 6; 7; 8]. The LSPR phenomenon, which enhances the luminescence properties of Re ions embedded in glass matrices, has been observed in various types of glasses, e.g., Er\({}^{3+}\)/Yb\({}^{3+}\) co-doped bismuth-germanate glasses containing silver NPs, 73 FeO\({}_{2}\)-4 BaO-3 Bi\({}_{2}\)O\({}_{3}\)-2 Eu\({}_{2}\)O\({}_{3}\)-Ag and Dy\({}^{3+}\) doped boro-tellurite glasses with Ag nanoparticles [9; 10]. It should be noted that in the case of glasses containing bismuth, one aspect can affect the formation of Ag nanoparticles. Eutectic transition has been reported between Ag and Bi\({}_{2}\)O\({}_{3}\)[11]. According to the phase diagram by [PERSON] et al., eutectic transformation can occur at around 687 \({}^{0}\)C, which is lower than the B\({}_{2}\)O\({}_{3}\)-Bi\({}_{2}\)O\({}_{3}\) glass melting point [12]. The formation of (Bi\({}_{2}\)O\({}_{3}\)-Ag) eutectic was observed in Bi\({}_{2}\)O\({}_{3}\)-Ag bulk composite [13]. Borate-bismuth glass seems to be a good host for Ag nanoparticles. Boron oxide is a commonly used glass former in various types of commercial glasses with the ability to form glass in a wide range of Bi\({}_{2}\)O\({}_{3}\) additions (20-80 mol% Bi\({}_{2}\)O\({}_{3}\)) [14; 15]. The combination of boron and bismuth oxides results in their excellent optical properties, including a high refractive index and wide transparency for both visible and IR light [14; 16; 17]. Borate-bismuth glasses are also known for their good solubility for rare-earth (Re) ions, which makes them excellent hosts for them [18]. Moreover, they have high chemical and physical durability. Our prior experience with borate glasses demonstrates their efficacy as a matrix for luminescence applications when doped with bismuth oxide.