Characterization of SERS–fluorescence bimodal nanocomposites from Au-decorated CaTiO₃:Eu³⁺

Surface-enhanced Raman scattering (SERS)–fluorescence bimodal composites have attracted great interest for biomedical applications. Herein, we report the characterization of Au-decorated CaTiO₃:Eu³⁺ nanocomposites (CaTiO₃:Eu³⁺@Au NCs) using SERS and fluorescence properties. X-ray diffraction (XRD) of the CaTiO₃:Eu³⁺@Au NCs shows orthorhombic phases, which are in good agreement with the standard CaTiO₃ XRD peaks. The photoluminescence (PL) spectra show a strong visible red emission at 614 nm (⁵D₀ → ⁷F₂) with an excitation wavelength of 380 nm. The PL-emission intensity of the CaTiO₃:Eu³⁺@Au NCs increased more than that of the CaTiO₃:Eu³⁺ powder. The maximum PL-emission intensity of the CaTiO₃:Eu³⁺@Au NCs was obtained at an Au doping concentration of 0.8 mol/L; however, the intensity at higher Au doping concentrations (> 0.8 mol/L) was lower. This behavior is consistent with the SERS results. These results suggest that varying the Au nanoparticle concentration can control the PL-emission intensity and SERS of the CaTiO3:Eu³⁺@Au NCs. Therefore, CaTiO₃:Eu³⁺@Au NCs may be useful for multiplex detection and bioimaging.