## 1 Introduction
Through this study, a facile and novel development of the tunable silica thickness and enhancement in stability and biocompatibility of the Fe\({}_{3}\)O\({}_{4}\)/SiO\({}_{2}\) core/shell nanocubes was demonstrated. These materials presented excellent magnetization and an affinity for binding molecules of the formed core/shell, which make them promising materials for diverse bio-sensing applications [45; 46]. Many types of research illustrate the use of magnets in different special applications, for example, the removal of different metallic parts such as safety pins [47; 48], bullets, grenade splinters, dental prostheses, and catheters navigating through the brain and body [35; 49]. Recently, magnetic nanoparticles have been intensively used in magnetic guide applications, bioaccumulation, and hyperthermia, especially because of their magnetic properties and their interaction with external electromagnetic fields. Magnetite nanoparticles are interesting because of the two valence states of the iron cations, Fe\({}^{2+}\) and Fe\({}^{3+}\), that have inverse spinel structures with a special surface modification capacity. This also includes the possibility to be coated and to manufacture core/shell systems only by maintaining the superparamagnetic properties of the core [50; 51; 52]. Magnetite nanoparticles have gained interest in applications from biomedical fields, such as drug delivery [53; 54] and therapeutic treatments [55; 56], as well as contrast agents for MRI [54], magneto-thermal therapy [57], enzyme immobilization [58; 59], bio-separation [54; 55], cells labelling [60; 61], hyperthermia [53; 54], and tissue engineering [54; 55]. Recently, studies have demonstrated that biomedicine uses coated magnetic nanoparticles to improve their stability and biocompatibility. Researchers have seen excellent materials such as silica that were considered as shells for magnetic nanoparticles, because they had protective behavior and adapted to various chemicals and molecules. The most common method used for the functionalization of silica on the surface of magnetite nanoparticles is the Stober sol-gel method [5; 50; 51; 62; 63]. The Stober sol-gel method is a chemical synthesis usually used to prepare silica nanoparticles with controllable growth and uniform size particles for diverse applications. Since it was discovered, the Stober method remains the most widely used wet chemistry synthesis approach to synthesize silica nanoparticles. Through the Stober sol-gel method, researchers were able to produce large silica particles with diameters ranging from 50-2000 nm, depending on conditions. Researchers were able to understand their kinetics and mechanisms, and more control over particle size, distribution, and tunable physical properties were also achieved [64; 65]. Typically, in the Stober method, ethanol and ammonia (catalyst) are mixed with a small amount of deionized water, followed by the addition of tetraethylorthosilicate (TEOS) under continuous stirring, which can be replaced by sonication. In this method, the rate-determining steps which can affect the physicochemical properties of silica nanoparticles are a concentration of TEOS, ammonia, water, type and amount of solvent, reaction temperature, and pH [6]. The major advantage of the Stober method is that it can synthesize almost monodisperse silica nanoparticles and, as already said before, it remains the most widely used wet chemistry synthesis approach for silica nanoparticles. Because monodisperse silica nanoparticles with controlled sizes are produced, the process is considered a convenient approach in preparing silica nanoparticles for applications including intracellular drug delivery and biosensing [66; 67]. This advantage of synthesizing silica nanoparticles through the Stober method suggests that silica coated over magnetite nanoparticles can significantly improve their stability for long-term storage conditions, thus retaining their medical properties by improving their shelf life.