Submicron Y2O3 particles codoped with Eu and Tb ions: Size controlled synthesis and tuning the luminescence emission

Toxicity response of highly colloidal, bioactive, monodisperse SiO2@ Pr(OH)3 hollow microspheres

In a facile synthesis, highly colloidal, bioactive Pr(OH)₃-encapsulated silica microspheres (PSMSs) with an average diameter of 500-700 nm were successfully prepared via a sol-gel process followed by heat treatment. The phase formation, morphology, surface and optical properties of the as-synthesized PSMSs were characterized by various techniques including X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscope (SEM), transmission electron microscope (TEM), N₂-adsorption-desorption, energy dispersive X-ray (EDX) analysis, Fourier transform infrared (FTIR) and UV/vis spectroscopy. The PSMSs were semi-amorphous or ultra-small in size, highly dispersible in water, mesoporous, irregular in size and spherical in shape. The SEM images show a well-ordered broad nanoporous structure which is preserved after coating with Pr(OH)₃ molecules, demonstrating interaction between the optically active Pr³⁺ ion and silanol (Si-OH) groups via hydrogen bonding. Optical spectra show well-resolved weak intensity 4f-4f absorption transitions in the visible region of the Pr³⁺ ion, indicating successful grafting of the Pr(OH)₃ layer. Toxicity was measured by MTT and NRU assays to determine potential toxicity. Cell viability was suppressed with increasing dosage of PSMSs, but showed greater than 55% cell viability at a concentration of 200 μg/mL, resulting in low toxicity. Due to its high aqueous dispersibility, optical activity, excellent biocompatibility and low toxic nature, it could be a favorable material for biomedical and drug delivery applications.

Aqueous dispersible green luminescent yttrium oxide:terbium microspheres with nanosilica shell coating

Tb-doped Y₂O₃ microspheres (MSs) were prepared via a homogeneous thermal degradation process at a low temperature and then coated with a nanosilica shell (Y₂O₃:Tb@SiO₂) using a sol-gel process. The core MSs were highly crystalline and spherical with a porous surface, single cubic phase, and particle size of 100-250 nm. Transmission electron microscopy (TEM) images clearly showed the spherical shape of the as-prepared core MSs, which were fully covered with a thick and mesoporous nanosilica shell. Fourier transform infrared (FTIR) spectra displayed the well-resolved infrared absorption peaks of silica (SiO, SiOSi, etc.), confirming the presence of the silica surface coating. The core MSs retained their spherical shape even after heat treatment and subsequent silica surface coating. It was observed that the core/shell MSs are easily dispersible in aqueous media and form a semi-transparent colloidal solution. Ultraviolet/visible and zeta potential studies were tested to prove the changes in the surface chemistry of the as-designed core/shell MSs and compare with their core counterpart. The growth of the amorphous silica shell not only increased the particle size but also enhanced remarkably the solubility and colloidal stability of the MSs in aqueous media. The strongest emission lines originating from the characteristic intra-shell 4f-4f electronic transitions of Tb ions were quenched after silica layer deposition, but the MSs still showed strong green (⁵D₄ → ⁷F₅ at 530-560 nm as most dominant) emission efficiency, which indicates great potential in fluorescent bio-probes. The emission intensity is discussed in relation to the quenching mechanism induced by surface silanol (Si-OH) groups, particle size, and surface charge.

Multicolor nanoprobes based on silica-coated gadolinium oxide nanoparticles with highly reduced toxicity

Multicolor core-shell nanoprobes were developed for molecular imaging of living cells using optical and MRI technique.

Cytotoxicity and cell imaging potentials of submicron color-tunable yttria particles

Increased demand of environment protection encouraged scientists to design products and processes that minimize the use and generation of hazardous substances. This work presents comprehensive result of large-scale fabrication and investigation of red-to-green tunable submicron spherical yttria particles codoped with low concentrations of Eu(+3) and Tb(+3). The color emission of synthesized particles can be precisely tuned from red to green by simple variation of Tb/Eu ratio and excitation wavelength. The Tb/Eu-codoped Y(2)O(3) particles did not adversely affect the viability of L-929 fibroblastic cells at concentrations less than 62.5 ppm. Through internalization and wide distribution inside the cells, Tb/Eu codoped Y(2)O(3) particles with intense bright green or red fluorescence rendered cell imaging to be possible. The high brightness, excellent stability, low-toxicity, and imaging capability along with fine color-tunability of synthesized particles enable to find promising application in various areas.