Sol-gel synthesis of Eu3+ doped silica-gold nanorod composites with tunable optical properties

Gold nanorods (AuNRs) suspension at various concentrations was added into the sol-gel process to engineer nanostructured europium-doped silica host matrices as light-emitting composites. For this purpose, the samples were prepared following two different routes depending on the chemicals used as dopant and catalyst: (a) Eu(NO3)(3).5H(2)O and HNO3, and (b) EuCl.6H(2)O and HCl. In any case, samples adding various concentrations of AuNRs suspension were prepared. The structural characterization of the samples was through STEM, backscattered electrons (BSE), and EDS analysis. Additionally, their optical properties were evaluated by PL spectroscopy and CIE colorimetry. The results confirmed that (a) methodology produced samples with AuNRs embedded and randomly distributed in the samples. However, these features were not observed in the samples obtained through (b) due to AuNRs dissolution in HCl media. Regarding the optical properties, the analysis of the relative intensity ratio D-5(0) / F-7(2)/D-5(0) / F-7(1) suggested that Eu3+ ions occupy non-centrosymmetric sites in (a) host matrices and centrosymmetric sites in (b). Hence, the increase of AuNRs suspension when fabricating (a) host matrices produced remarkable color changes in the luminescence of the samples towards the reddish-orange region. Meanwhile, the dissolution of AuNRs in (b) minimized the localized surface plasmon resonance (LSPR) effects on the Eu3+ luminescence. These findings revealed that the evaluation and selection of chemicals are critical factors when engineering these materials for more efficient coupling between the LSPR and Eu3+ luminescence.

Automated summary

This study engineered light-emitting composites by adding gold nanorods (AuNRs) suspension at various concentrations into the sol-gel process with europium-doped silica host matrices. The results showed that the addition of AuNRs suspension produced remarkable color changes in the luminescence of the samples towards the reddish-orange region, while the dissolution of AuNRs minimized the localized surface plasmon resonance effects on the luminescence. Therefore, the evaluation and selection of chemicals are critical factors for more efficient coupling between the localized surface plasmon resonance and the luminescence.