# Role of Functional Monomers upon the Properties of Bisphenol A Molecularly Imprinted Silica Films
## 4 Conclusions  
The study provides significant information regarding the role of functional monomers in the molecular imprinting process of BPA in silica networks. The two sets of BPA molecularly imprinted films (i.e., BPA-MIP\({}_{\text{DAMOT}}\) and BPA-MIP\({}_{\text{MPTES}}\)) were successfully prepared via sol-gel derived methods using N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (DAMO-T) and (3-mercaptoethanolpropyl)trimethoxysilane (MPTES) as functional organosilane monomers.  
Morpho-structural, thermal, and optical studies were undertaken to assess the influence of the monomers' functionalities upon the overall features of films but also to highlight the meaningful changes brought by the addition of BPA. Ellipsometry results suggested that there is much potential for application of such BPA-MIP films in optical sensing applications. An evaluation of specificity for BPA was conducted and the relevant results on adsorption capacities and imprinting factors for both types of films- were in agreement with their morpho-structural properties.  
The overall results have shown that thinner films with better-defined porous morphology, meaning BPA-MIP\({}_{\text{MPTES}}\) were more likely to retain BPA molecules. In this case, the most specific binding of BPA was registered in the first five minutes after contact (F = 3.03). BPA-MIP films were effectively regenerated for further usage 5 times and the adsorption capacity of films decreased only by 35% after three cycles, demonstrating high stability and reusability.  
In order to ascertain the real application potential of the prepared sol-gel imprinted films for BPA detection, the next challenges will assume an investigation of the selective adsorption of BPA-MIP films using compounds with similar structure and application of the methodology for real samples contaminated with BPA. Considering that the BPA-MIPs films enable stability and reusability, the real-time response can be estimated in terms of quantification limit (LOQ) in the range of ng-\(\upmu\)g in aqueous samples. Although further investigations are required, this work is a step forward to develop simple and cost-effective molecularly imprinted silica films for optical sensors.  
Figure 9: Reusability experiments of BPA-MIP and NIP films.  
**Supplementary Materials:** The following are available online at [[https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)]([https://www.mdpi.com/2076-3](https://www.mdpi.com/2076-3)) 417/11/7/2956/s1, Figure S1: The UV-visible absorption spectra after two steps of washing (1) 1 st washing protocol with ethanol and (2) 2 nd washing with ethanol-acetic acid (9:1, \(v/v\)) for imprinted BPA-MIPMPTES and BPA-MIPADMMO and their non-imprinted NIPMPTES and NIPADMMO; Figure S2. UV-visible absorption spectra of 1.5 ug/mL bisphenol A in ethanol; Figure S3. The calibration curve of BPA in ethanol solution; Figure S4. Thermogravimetric curve (TG) and its derivative (DTG) for BPA template; Figure S5. Fitting of the experimental ellipsometric data.  
**Author Contributions:** Conceptualization of the paper by [PERSON] and [PERSON]; Methodology by [PERSON], [PERSON] and [PERSON]; Formal analysis by [PERSON], [PERSON] and [PERSON]; Investigation by [PERSON]; Writing of Original Draft was done by [PERSON] and [PERSON]; Writing--review and editing by [PERSON]; Supervision by [PERSON]; Project administration by [PERSON], [PERSON]; All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by Romanian Funding Agency UEFISCDI, through the supporting projects NUCLEEU PN.19.23.02.01. and by the 255 PED/2020.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data presented in this study are available in the article.  
**Conflicts of Interest:** The authors declare no conflict of interest.