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Tb-doped Y 2 O 3 microspheres (MSs) were prepared via a homogeneous thermal degradation process at a low temperature and then coated with a nanosilica shell (Y 2 O 3 :Tb@SiO 2 ) 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 ( 5 D 4  →  7 F 5 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., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Mesoporous multi-layered silica-coated luminescent Y 2 O 3 :Eu nanoparticles (NPs) were prepared by a urea-based decomposition process, and their surfaces were gradually modified with nanoporous and mesoporous silica layers using modified sol-gel methods. The synthesized luminescent core-shell NPs were characterized thoroughly to investigate their structural, morphological, thermal, optical, photo luminescent properties and their surface chemistry. The morphology of the core NPs were nearly spherical in shape and were nano-sized grains. The observed luminescent efficiency of the mesoporous multi-layered silica-coated luminescent core NPs was gradually reduced because of bond formation between the Y 2 O 3 :Eu core and the amorphous silica shell via YOSiOH bridges on the surface of the NPs; the bonds suppressed the non-radiative transition pathways. Biocompatibility tests on Human breast cancer cells using the 3‑(4,5‑Dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide and lactate dehydrogenase assays indicated that the core-shell NPs were non-toxic even at high concentrations. The mesoporous SiO 2 layer played a key role in perfecting the solubility, biocompatibility, and non-toxicity of the NPs. The zeta potential, surface chemistry (Fourier transform infrared spectroscopy), and optical absorption spectral analyses revealed the high hydrophilicity of the as-prepared core-shell NPs because of the active surface-functionalized silanol (SiOH) groups, which could potentially offer many exciting opportunities in photonic-based biomedical applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Monodispersed La(OH) 3 :Eu nanospheres(core-NSs) were synthesized by urea-based homogeneous co-precipitation process, where mesoporous silica layer was coated over the surface of luminescent La(OH) 3 :Eu core-NSs. The XRD data exhibit the high crystalline, single hexagonal-shaped La(OH) 3 :Eu core and silica modified La(OH) 3 :Eu@mSiO 2 (core-shell) NSs. Monodispersibility, spherical shaped, high surface area and mesoporosity were identified by TEM analysis and were further confirmed by BET analysis. The as-synthesized samples are highly soluble in aqueous media at ambient conditions. Spectroscopic analyses were also carried out to examine the impact of surface modification on structural, surface chemistry, optical and luminescence behavior of the as-designed silica coated core-shell NSs. The emission spectral study revealed that the luminescence intensity of magnetic-dipole transition (590 nm, 5 D 0  →  7 F 1 ) is dominant with respect to electric-dipole (614 nm, 5 D 0  →  7 F 2 ) transition. The high crystallinity of the hydroxide products supports the existence of good photoluminescence intensity, a good indication for their future use in detection of biomacromolecules through hypersensitive emission (614 nm, 5 D 0  →  7 F 2 ) transition. Excellent biocompatibility, cell viability and good luminescence properties suggested that the as-prepared core-shell NSs are an ideal candidate for luminescence biolabeling/bioimaging and as an optical bio-probe., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Luminescent functionalized mesoporous SiO2@Eu(OH)3 core-shell microspheres (LFMCSMs) were prepared by coating of europium hydroxide (Eu(OH)3) shell on mesoporous silica (SiO2) nanospheres via a facile one-pot process at low temperature. The FETEM images revealed that a well-defined luminescent europium hydroxide shell was successfully grafted on the surface of mesoporous silica nanospheres. These experimental results showed that the LFMCSM has a typical diameter of ca. 392 nm consisting of the silica core with about 230 nm in diameter and europium hydroxide shell with an average thickness of about 162 nm. LFMCSMs exhibited strong red emission peak upon irradiation with ultraviolet light, which originated from the electric-dipole transition (5)D0 → (7)F2 (614 nm) of Eu(3+) ion. The biocompatibility of the synthesized LFMCSMs was evaluated in vitro by assessing their cytotoxic and genotoxic effect on human hepatoblastoma (HepG2) cells using MTT, TUNEL, fluorescent staining, DNA ladder and Gene expression assays respectively., From the Clinical Editor: This paper describes the development of a one-pot synthesis of luminescent mesoporous SiO2@Eu(OH)3 core-shell microspheres and evaluates their favorable in vitro cyto-toxicity and geno-toxicity, and their applications in bio-imaging of these particles that emit bright red signal under UV exposure., (Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.)

In this work, mesoporous shells were constructed on solid silica cores by employing anionic surfactante. A co-structure directing agent (CSDA) has assisted the electrostatic interaction between negatively charged silica particles and the negatively charged surfactant molecules. Synthetic parameters such as reaction time and temperature had a significant impact on the formation of mesoporous silica shelld and their textural properties such as surface area and pore volume. Core-mesoporous shell silica spheres were characterized by small angle X-ray scattering, transmission electron microscopy, and N(2) adsorption–desorption analysis. The synthesized particles have a uniformly mesoporous shell of 34–65 nm and possess a surface area of ca. 7–324 m2/g, and pore volume of ca. 0.008–0.261 cc/g. The core-mesoporous shell silica spheres were loaded with ketoprofen drug molecules. The in vitro drug release study suggested that core-mesoporous shell silica spheres are a suitable nanocarrier for drug molecules offering the possibility of having control over their release rate.

In this work, we demonstrate a simple two-pot approach to double mesoporous core-shell silica spheres (DMCSSs) with uniform size of 245-790 nm, shell thickness of 41-80 nm and surface area and total pore volume of 141-618 m(2) g(-1) and 0.14-0.585 cc g(-1), respectively. First, solid silica spherical particles were synthesized by the Stöber method and used as a core. Second, a mesoporous shell could be formed around the silica cores by using an anionic surfactant and a co-structure directing agent. It was found that mesopores can be anchored within dense silica cores during mesoporous silica shell formation, synchronously the base group with surfactant assistant can etch the dense silica cores to re-organize new mesostructure, so that double mesoporous core-shell silica sphere (DMCSS) structure can be obtained by a single surfactant-templating step. The spherical size and porosity of the silica cores of DMCSS together with shell thickness can be tuned by controlling Stöber parameters, including the concentrations of ammonia, solvent and tetraethoxysilane and the reaction time. DMCSS were loaded with ketoprofen and thymoquinone, which are an anti-inflammatory and a potential novel anti-cancer drug, respectively. Both drugs showed controlled release behavior from the pores of DMCSS. Drug uptakes within DMCSS were ~27 and 81 wt.% for ketoprofen and thymoquinone, respectively. Furthermore, DMCSS loaded with thymoquinone was more effective in inducing cancer cell apoptosis than uncontained thymoquinone, because of the slow release of the drug from the mesoporous structure., (Copyright © 2012 Elsevier Inc. All rights reserved.)