Photocatalytic and Photoluminescence Properties of Core–Shell SiO₂@TiO₂:Eu³⁺,Sm³⁺ and Its Etching Products

Abstract

A novel multifunctional core–shell, yolk–shell SiO2@TiO2:Eu3+/Sm3+ and hollow TiO2:Eu3+/Sm3+ structures were successfully synthesized. The relationship between morphology/ions doping and multifunctional properties including photoluminescence and photocatalysis has been discussed in detail for the first time using systematic characterization techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), photoluminescence (PL), ultraviolet–visible light (UV-vis) analysis, Fourier transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS). Upon ultraviolet (UV) excitation, the products show the characteristic red and orange–red emission lines of Eu3+ and Sm3+, respectively. In addition, Judd–Ofelt intensity parameters (Ω2, Ω4) were used to investigate the symmetry and coordination state of Eu3+ ions in the products with different morphologies. The relative luminescence intensities were in the following order: yolk–shell > core–shell > hollow structure. This phenomenon can be ascribed to the unique yolk–shell configuration, which possesses appropriate interior cavity used for multiple reflections and scattering, allowing for more-efficient utilization of the light. Moreover, compared with yolk–shell and hollow structure, the core–shell spheres exhibit excellent photoactivity for the degradation of MO, because the existence of Ti–O–Si bonds increases the surface acidity of the sample, thereby activating the oxidation reaction. In addition, the electron activation in the TiO2 matrix can be facilitated through intermediate oxygen atoms. Moreover, products doped with different rare-earth (RE3+) ions exhibited distinguishable photocatalytic performance. The surfactant-free method provides a promising route toward the development of multifunctional materials for many applications in photocatalysis and PL.

SiO2@TiO2:Sm3+ with Diverse Phase Structure and Morphology: Photoluminescence and Simulated Solar Light‐Activated Photodegradation Properties

“…The O 1s spectra are showed in Figure (b). All spectra can be deconvoluted to three peaks, which are ascribed to Ti‐O−Ti, Ti‐O−Si and Si‐O−Si bonds, respectively . The result further proved the existence of Si in the hollow structure.…”

“…Due to the alkali‐dissolution characteristics of SiO 2 , yolk‐shell and hollow structures can be easily obtained through an etching process. Our previous work has reported the relationship between these three structure and performance . However, the effect of different preparation methods on the time for complete etching of SiO 2 was not discussed, and the etching time used for obtaining the hollow structure is too long.…”

Controlled synthesis and luminescence properties of core-shell-shell structured SiO2@AIPA-S-Si-Eu@SiO2 and SiO2@AIPA-S-Si-Eu-phen@SiO2 nanocomposites

“…As shown in Fig. S10, all curves follow a double exponential fit (1) 38 : Table 1. Luminescence emission spectra data of core-shell and core-shell-shell nanocomposites.…”

Luminescence properties in relation to controllable morphologies of Ba3[Ge2B7O16(OH)2](OH)(H2O):Eu3+ and its thermal conversion product Ba3Ge2B6O16:Eu3+

“…The very weak 5 D 0 / 7 F 3 transitions can also be observed at 653 nm. 29 The results show that the red emission 5 D 0 / 7 F 2 transition is dominant in intensity, and so, the Eu 3+ ions mainly occupied a non-inversion symmetry center in the crystal lattice. As the concentration of Eu 3+ increases, the emission associated with Eu 3+ continues to increase rst, and above the 3% doping concentration, it decreases due to concentration quenching.…”