# Enhancement of the Luminescence Properties of Eu (III) Containing Paramagnetic Saponite Clays
## 4 Conclusions  
In this work, two hybrid materials were prepared through intercalation of 1,10-phenanthroline molecules in a bifunctional optical/paramagnetic saponite clay containing Eu\({}^{3+}\) and Gd\({}^{3+}\) ions in structural positions. The phenanthroline was introduced in the interlayer space of the saponite at two different loadings. The hybrid materials, which already possessed interesting optical and magnetic properties, exhibit significantly improved luminescent features upon interaction of phenanthroline molecules with Eu\({}^{3+}\) ions, especially in the sample with the highest organic loading, due to an efficient antenna effect from the ligand to the metallic centers, which is even greater than the Gd\({}^{3+}\)-Eu\({}^{3+}\) energy transfer previously observed. From a magnetic point of view, the solids maintain similar relaxometric properties in aqueous solution compared to the starting bifunctional saponite. The properties displayed by the hybrid materials prepared in this study make them desirable in applications such as optical and MRI probes or as light-emitting devices. The following are available online at [[https://www.mdpi.com/article/10.390/app11198903/sl](https://www.mdpi.com/article/10.390/app11198903/sl)]([https://www.mdpi.com/article/10.390/app11198903/sl](https://www.mdpi.com/article/10.390/app11198903/sl)), Scheme S1: Schematic view of the intercalation procedure of 1,10-phenanthroline (Phen) molecules into the interlayer space of Na-GdEuSAP, at two different loadings with respect to the cation exchange capacity of the clay, and of the simplified structure of the final material; Figure S1. **(A)** UV-Vis spectra of [Co (NH\({}_{3}\))\({}_{6}\)]\({}^{3+}\) standard solutions at 25 \({}^{\circ}\)C with concentration in the 0.05-0.005 M range. **(B)** Calibration curve extrapolated by the UV-Vis spectra (\(\lambda_{\text{abs}}\) = 475 nm). **(C)** UV-Vis spectra of the supernatant of Na-GdEuSAP, obtained after treatment of the solid in 0.02 M [Co(NH\({}_{3}\))\({}_{6}\)]\({}^{3+}\) at 25 \({}^{\circ}\)C for 60 h; Figure S2: X-ray profile of crystalline Phen; Figure S3: TGA **(A)** and DTG **(B)** profiles of crystalline Phen. The analyses were carried out under oxygen flow (100 mL/min); Figure S4: Excitation spectrum at solid state of Phen-GdEuSAP_1, monitored at 615 nm; Figure S5: **(A)** Excitation spectrum at solid state of Phen, monitored at 415 nm. **(B)** Emission spectrum at solid state of Phen, under excitation at 290 nm; Figure S6: Emission spectra at solid state of Na-GdEuSAP (a) [1], Phen-GdEuSAP_1 (b) and Phen-GdEuSAP_2 (c), under excitation at 399 nm; Figure S7: PL T\({}_{1}\)-S\({}_{0}\) (415 nm) intensity decay over time of Phen-GdEuSAP_1 **(A)** and Phen-GdEuSAP_2 **(B)** under irradiation at 295 nm at solid state. The curves fitting was performed with a bi-exponential function (black lines). The \(\chi^{2}\) and \(RSS\) (residual sum of squares) values are reported in the table below; Figure S8: PL T\({}_{1}\)-S\({}_{0}\) (415 nm) intensity decay over time of Phen-SAP_1 **(A)** and Phen-SAP_2 **(B)**, under irradiation at 295 nm at solid state. The curve fitting was performed with a bi-exponential function (black lines). The \(\chi^{2}\) and \(RSS\) (residual sum of squares) values are reported in the table below; Figure S9. PL \({}^{5}\)D\({}_{0}\)-\({}^{7}\)F\({}_{2}\) (615 nm) intensity decay over time of Na-GdEuSAP **(A)**, Phen-GdEuSAP_1 **(B)** and Phen-GdEuSAP_2 **(C)**, under irradiation at 370 nm at solid state. The curve fitting was performed with a bi-exponential function (black lines); Table S1: Photometric data, in accordance with CIE 1931 colour spaces, for Phen-GdEuSAP_1 and Phen-GdEuSAP_2, extrapolated from emission spectra at solid state shown in Figure 3.  
Conceptualization, S.M., C.B. and F.C. ; methodology, S.M., C.B. and F.C. ; formal analysis, S.M. ; investigation, S.M. ; data curation, S.M. and F.C. ; writing--original draft preparation, S.M. ; writing--review and editing, C.B. and F.C.