# Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films
## 1 Introduction
In this context, the preparation of MIPs for sensing applications was performed, in recent years, by combining MI with sol-gel techniques as an alternative approach to overcome these shortcomings [28; 29]. The method is simple and implies deposition/casting of thin films on various surfaces (for example nanowires, nanotubes, glass, ceramic and plastic substrates). Literature studies are minimal when it comes to BPA imprinting for obtaining MIP films via sol-gel methods. One of these studies include that of [PERSON] et al. [30], who described the electrochemical deposition of imprinted sol-gel films with specific binding sites for BPA on a gold electrode. This work implied the use of expensive nanomaterials and the minimal characterization of the sol-gel film hampers the assessment of efficiency. A recent study of [PERSON] and [PERSON] [31] used the surface-initiated atom transfer radical polymerization (SI-ATRP) for the synthesis of BPA-imprinted poly(4-vinyl pyridine-co-ethylene glycol dimethacrylate) films on a specific surface of silica inverse opal-formed quartz crystals (QCs). It is also worth mentioning the paper of [PERSON] et al., who prepared molecularly imprinted nanofibers based on 3-aminopropyltriethoxysilane (APTES) as functional monomer and nylon 6 as the matrix, using the sol-gel and the electrospinning techniques, which can absorb BPA in water samples [32]. Another valuable study of [PERSON] and co-workers [33] reported the use of APTES and phenyl triethoxysilane to prepare imprinted sol-gel sorbents for the BPA removal from moat waters and tap water. Although the MIP sorbent can be used up to ten times, the extraction protocol involves numerous steps and materials. With regard to the recent literature, the present study provides a simpler and more reproducible procedure to prepare BPA-MIPs, with the use of MI and sol-gel derived techniques. The methodology is original and consisted of casting the BPA-MIP layer on top of previously degreased glass support. According to the present literature, this combined procedure of BPA imprinting has never been used to prepare MIP films. Thereby, the aim of this work was to prepare and characterize two types of BPA-MIP films, based on two different organosilane monomers, meaning N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (DAMO-T) and (3-mercapopropyl)trimethoxysilane (MPTES). The films BPA-MIP\({}_{\text{DAMOT}}\) and BPA-MIP\({}_{\text{MPTES}}\) were obtained by spraying the sol-gel precursor solutions directly on previously depressed glass slides. The proposed sol-gel approach for BPA-MIP preparation seemed to be suitable due to the low temperature processing conditions (for polycondensation at 25 \({}^{\circ}\)C and for the maturation of films at 60 \({}^{\circ}\)C). The prepared BPA-MIP films were well characterized by Fourier-Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and Atomic Force Microscopy (AFM), as well as thermogravimetric analysis (TGA). The optical behavior of films was investigated by ellipsometry, to establish the imprinting effect over the final properties of the obtained BPA-MIPs. The BPA-MIP films were further tested in terms of rebinding measurements in liquid state via spectrophotometric techniques, to assess their potential as sensing elements for optic sensors. The reusability and stability of the sol-gel films were also discussed.