Zn2SiO4:Eu3+ phosphors with diverse morphologies, including rice-like, hexahedron-like, and column-like, have been successfully prepared by means of a simple hydrothermal approach followed by a subsequent calcinations process. The results indicate that the morphologies of the products can be adjusted by altering the pH value of the reaction system. The formation mechanisms of different morphologies of samples have been investigated in detail. Furthermore, under near ultraviolet excitation, the Zn2SiO4:Eu3+ exhibits strong red emission corresponding to the 5D0→7F2 transitions of the Eu3+ ions, which have potential applications in optical and biological areas. Meanwhile, luminescent characteristics of different morphologies have been explored and the column-like Zn2SiO4:Eu3+ sample presents an optimum red luminescence. The CIE chromaticity diagram and the symmetry of the different morphologies phosphors also have been explored. In addition, the concentration quenching effects and decay kinetics behaviors of Zn2SiO4:Eu3+ microstructures with optimum red luminescence were investigated and the strongest luminescent intensity and the longest lifetime were both in the composition of 0.03 mol Eu3+.

Luminescent one-dimensional Lu2O2S:Eu3+ fibers were successfully prepared via an electrospinning method followed by a subsequent two-step calcination process for the first time. Scanning electron microscopy (SEM) showed that the as-obtained samples present a fiber-like morphology with uniform size and the diameters of the fibers changed from microscale to nanoscale with the increase of Eu3+ concentration. The emission spectra indicated that the obtained Lu2O2S:Eu3+ fibers exhibited typical Eu3+ (5D0–7FJ) red emission under ultraviolet excitation and the concentration quenching effects occurred in the fibers composed of 3 mol% Eu3+. The decay kinetics behaviors of the Lu2O2S:Eu3+ fibers were investigated, which showed that the fibers composed of 3 mol% Eu3+ also had the longest lifetime. The spectral characteristics and Eu–O ligand behavior were discussed through Judd–Ofelt parameters such as intensity parameters (Ω2, Ω4), radiative transition probability (ARAD), radiative lifetime (τrad), and branching ratio (β0J). In addition, the energy-dispersive X-ray spectra (EDS), thermogravimetry-differential thermal analysis (TG-DTA) and the formation mechanism were also displayed in order to better understand the work.

Calcium carbonate (CaCO3) particles including three anhydrous polymorphs (calcite/vaterite/aragonite) have been prepared in the absence and presence of sodium carboxyl methylcellulose (NaCMC), which further serve as hosts to prepare the phosphors doped with Eu3+. The as-obtained samples were characterized by means of XRD, SEM, and PL techniques. The experimental results reveal that vaterite, as a less stable polymorph, will transform into calcite in aqueous solution without any additive. In contrast, NaCMC can induce the formation of vaterite phase at 50 °C and the formation of aragonite phase at 90 °C in aqueous solution. In addition, the polymorph-dependent luminescence properties of CaCO3:Eu3+ have been briefly studied by excitation spectra, emission spectra, PL decay curves and quantum yield.

Gd3+ and Eu3+ ions co-doped CaCO3 nanoparticles have been successfully synthesized via carbonization method. The emission spectra of co-doped CaCO3 phosphors in the range of VUV–vis spectral were studied. The results reveal that the co-doped CaCO3 phosphors show intense red emission in the VUV range because of the Gd3+ ions as sensitizers. The energy transfer process from Gd3+ to Eu3+ in CaCO3:Gd3+/Eu3+ phosphors was investigated and discussed in terms of the luminescence spectra and the decay curves, which demonstrated that the energy transfer of Gd3+→Eu3+ is efficient. The mechanism of energy transfer from Gd3+ to Eu3+ is a resonant transfer, in which electric dipole–dipole interaction plays a leading role. Furthermore, the effect of doping concentration of Eu3+ ions on the energy transfer efficiency was also investigated. From the photoluminescence (PL) spectra, it was also found that the incorporation of Na+ ions into CaCO3:Gd3+/Eu3+ could lead to a remarkable increase of luminescent intensity due to the charge compensation.

Lu2O2S:Eu3+ phosphors were successfully prepared with controllable morphology, including 3D sphere-like, cloud-like, nested tetrahedron, flower-like and 1D rod-like architectures. It is indicated that the pH value of the system plays an important role in the morphology and the degree of crystallinity of the product. Interestingly, with morphological changes, the band gap energy of the Lu2O2S crystal changed, followed by a variation of the crystal field symmetry and furthermore the luminescence performance. Therefore, such a morphology-sensitive luminescence property was first interpreted in terms of degree of crystallinity, band gap energy, and the crystal field symmetry around Eu3+.

Enhanced red-emitting CaCO3:Eu3+ phosphors were in situ prepared using the carbonization method in the presence of sodium oleate. It has been proved that the introduction of sodium oleate can endow the products with a hydrophobic surface, which makes the products exhibit good compatibility with plastics or other polymers. Remarkably, the addition of sodium oleate can also enhance the red emission intensity of CaCO3:Eu3+ phosphors greatly compared to that of the common CaCO3:Eu3+ phosphors. The enhancement is attributed to two functions of sodium oleate. One function is that sodium oleate can avoid OH ligands and/or crystal water molecules attached on the surface of CaCO3 particles; the other function is that Na+ ions can supply effective charge compensation.

TiO2:Eu3+ submicrospheres have been successfully synthesized by a facile one-pot hydrothermal process using Ti(SO4)2 as Ti resource, d-fructose as the capping agent, and urea as the precipitation agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG/DTA), and photoluminescence spectra (PL) were performed to characterize the samples. The results show that TiO2:Eu3+ submicrospheres are assembled by primary nanocrystals with diameters of about 5 nm. The possible formation mechanism for TiO2:Eu3+ submicrospheres has been proposed on a hydrogen bond induced self-assembly process. Under ultraviolet excitation (λex=394 nm), these obtained TiO2:Eu3+ submicrospheres exhibit strong red emission corresponding to the 5D0→7F2 transition of Eu3+ ions.

•SiO2@Lu2O3:Eu3 + core–shell microspheres were prepared via a mild solvothermal method.•SiO2@Lu2O3:Eu3 + core–shell microspheres are monodisperse, uniform and submicron scale.•The obtained core–shell microspheres exhibit excellent red-luminescent properties.Highly monodispersed SiO2@Lu2O3:Eu3 + core–shell microspheres were successfully synthesized by coating the Lu2O3:Eu3 + nanoparticles onto the surface of non-aggregated spherical SiO2 particles via a simple solvothermal method, followed by a subsequent calcination process. The as-prepared phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermal analysis (TGA-DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM), and photoluminescence spectra (PL). The as-obtained core–shell microspheres show strong red emission corresponding to the 5D0 → 7F2 transition of the Eu3 + ions under ultraviolet (UV) excitation, which may have potential applications in light-emitting phosphors, field emission displays, advanced flat panel displays and biological labeling.This picture is the illustration for the formation process of the SiO2@Lu2O3:Eu3 + composite microspheres. Well-dispersed and uniform silica cores were used as template, and then a continuous europium-doped lutetium oxide precursor shells were homogeneously coated over the silica spheres template. At last, SiO2@Lu2O3:Eu3 + composite microspheres were obtained by calcinating the corresponding precursors at 800 °C for 2 h in air.

•The SiO2@SiO2:Eu3+ microspheres were synthesized in a seeded growth way.•The SiO2@SiO2:Eu3+ microspheres are monodisperse and uniform.•The spherical phosphors exhibit considerably strong PL of Eu3+ ions.Monodisperse core–shell structured SiO2@SiO2:Eu3+ microspheres were synthesized in a seeded growth way. In that way, a thin shell of Eu3+-doped silica was grown on the prepared monodisperse silica colloids. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR), thermal analysis (TGA-DSC) and photoluminescence (PL) spectroscopy. The results reveal that the SiO2 spheres have been successfully coated by SiO2:Eu3+ phosphors and the obtained SiO2@SiO2:Eu3+ particles have perfect spherical shape with narrow size distribution. Additionally, the monodisperse SiO2@SiO2:Eu3+ microspheres exhibit considerably strong photoluminescence (PL) of Eu3+ under the excitation of 393 nm compared with the SiO2:Eu3+ samples with polydispersed or irregular shapes and sizes obtained by base-catalyzed Stöber method. Furthermore, the PL intensity increases with the increasing of Eu3+ concentration in SiO2 microspheres shell, and concentration quenching occurs when Eu3+ concentration exceeds 5.0 mol%.Monodisperse core–shell structured SiO2@SiO2:Eu3+ microspheres were synthesized in a seeded growth way. The obtained SiO2@SiO2:Eu3+ particles have perfect spherical shape with narrow size distribution. Remarkably, the monodisperse SiO2@SiO2:Eu3+ microspheres exhibit considerably strong photoluminescence (PL) of Eu3+ under the excitation of 393 nm compared with the SiO2:Eu3+ samples with polydispersed or irregular shapes and sizes obtained by base-catalyzed method under the same Eu3+ ions doping concentration.

•Novel 3D Lu2O2S:Eu3+ microstructures were prepared via a mild solvothermal method.•The 3D Lu2O2S:Eu3+ microstructures are monodisperse and uniform.•The obtained 3D Lu2O2S:Eu3+ microstructures exhibit excellent red-luminescent properties.Novel 3D Lu2O2S:Eu3+ microstructures were successfully synthesized by a simple and effective solvothermal method followed by a subsequent calcination process. The X-ray diffraction (XRD) analysis reveals that the precursors have been thoroughly transformed into lutetium oxysulfide with high crystallinity after calcination at 800 °C. The field scanning electron microscope (FE-SEM) images show that the products are uniform and their morphologies are novel, just like two intertwined tetrahedrons slotted into each other. Furthermore, the obtained 3D Lu2O2S:Eu3+ architectures show strong red emission corresponding to the 5D0→7F2 transition of the Eu3+ ions under ultraviolet (UV) excitation.Novel and uniform morphology of 3D Lu2O2S:Eu3+ microstructures, which are just like two intertwined tetrahedrons slotted into each other, was prepared successfully by a simple solvothermal method followed by a subsequent calcination process for the first time. The obtained 3D Lu2O2S:Eu3+ architectures show strong red emission corresponding to the 5D0→7F2 transition of the Eu3+ ions under ultraviolet (UV) excitation.

•The cubic and spindle-liked CaCO3:Eu3+ have been first prepared using carbonization method without any additional crystal controlling agent.•Under UV light excitation, both the cubic and spindle-liked CaCO3:Eu3+ exhibits red emission without any treatment such as sintering.•The photoluminescence intensity of CaCO3:Eu3+ is different with the matrix's morphology.Cubic and spindle-shaped CaCO3 particles were successfully prepared using carbonation method without any additional crystal controlling agent. The experimental results showed that carbonation temperature and initial concentration of Ca(OH)2 slurry are the main factors to influence the morphology of CaCO3 particles. The as-prepared cubic and spindle-shaped CaCO3:Eu3+ particles are pure calcite, and Eu3+ ions have been effectively doped into the cubic and spindle-shaped CaCO3 lattices. Without any post-treatment such as sintering, both cubic and spindle-shaped CaCO3:Eu3+ particles exhibit strong red emission corresponding to the 5D0–7F2 transition of the Eu3+ ions under UV light excitation. Furthermore, CaCO3:Eu3+ cubic particles show higher luminescence intensity than CaCO3:Eu3+ spindle-shaped particles due to fewer defects of cubic CaCO3 particles.The cubic and spindle-like CaCO3:Eu3+ particles were in situ prepared using carbonization method. Under UV light excitation, both of them exhibit the strong red emission without any treatment such as sintering. It is easy to note that the relative intensities of the PL peaks are closely related to the matrix's morphology. The spindle-like CaCO3:Eu3+ shows much weaker luminescence than cubic CaCO3:Eu3+ under the same measurement conditions, which is attributed to the different matrix's internal and surface defects.

•Uniform Lu2O2S:Eu3+ spheres with different size were prepared via a solvothermal process followed by a heat treatment.•The luminescent properties of Lu2O2S:Eu3+ spheres changed with diameter of the spheres.•The size-sensitive luminescent properties were interpreted from several aspects.Monodisperse and uniform Lu2O2S:Eu3+ luminescent spheres have been successfully synthesized through a facile hydrothermal method followed by a subsequent calcination process. The sizes of the spheres can be tuned in the range of 65 nm–295 nm by only changing the pH value of the system. It is indicated that the luminescence properties of the spherical phosphors were strongly influenced by size of the spheres. Such a size-sensitive luminescence property was interpreted from the structures of the spheres, including the degree of crystallinity, band gap energy, crystal field symmetry around Eu3+. We expected that this study not only can provide important information for size-controlled synthesis of spherical phosphors, but also can give a reference for exploration of size-dependent luminescence.

Enhanced red-emitting CaCO3:Eu3+ phosphors were in situ prepared using the carbonization method in the presence of sodium oleate. It has been proved that the introduction of sodium oleate can endow the products with a hydrophobic surface, which makes the products exhibit good compatibility with plastics or other polymers. Remarkably, the addition of sodium oleate can also enhance the red emission intensity of CaCO3:Eu3+ phosphors greatly compared to that of the common CaCO3:Eu3+ phosphors. The enhancement is attributed to two functions of sodium oleate. One function is that sodium oleate can avoid OH ligands and/or crystal water molecules attached on the surface of CaCO3 particles; the other function is that Na+ ions can supply effective charge compensation.