Fluorescence Detection of Carbofuran in Aqueous Extracts Based on Dual-emission SiO2 @Y2 O3 :(Eu3+ ,Tb3+ )@MIP Core-shell structurally Nanoparticles

A novel double-windows fluorescent sensor for carbofuran (CF) detection was successfully developed based on rare-earth Eu, Tb-doped Y₂ O₃ @SiO₂ -based molecularly imprinted nanoparticles (MINs) with multilayer core-shell structure. The recognition process of the MINs for CF was fairly fast and merely need ca. 8 min to reach a dynamic equilibrium. Interestingly, one fluorescent attenuation window was found with an increase of CF concentration (Q) from 0.1 to 10 μg mL^-1 with the limit of detection (LOD) of 0.04 μg mL^-1 at 544 nm belonging to the Tb³⁺ emission, as well as the other fluorescence enhanced window within the range of CF concentration from 10 to 100 μg mL^-1 (LOD = 4 μg mL^-1 ) at 617 nm of Eu³⁺ emission in the dispersed rare-earth doped MINs colloidal aqueous solution. Simultaneously, it was obviously observed that the luminescent resonance energy transfer from CF to Eu³⁺ , and an inner filter effect of CF towards Tb³⁺ as well from the two independent detection windows. The competition experiment displayed hardly any remarkable interference during the detection of CF by addition of its analogues (carbaryl, isoprocarb, aldicarb, methomyl and etofenprox). Moreover, the MINs could also be applied to accurately detect CF in the rhubarb and wolfberry samples with the recoveries of 85.7%-92.2%. The sensing system has high specific recognition and wide detection range to CF and provides new opportunities in pesticide detection.

Hydrothermal Synthesis and Optical Properties of Magneto-Optical Na3FeF6:Tb3+ Octahedral Particles

Sodium iron hexafluoride (Na3FeF6), as a colorless iron fluoride, is expected to be an ideal host for rare earth ions to realize magneto-optical bi-functionality. Herein, monodispersed terbium ions (Tb3+) doped Na3FeF6 particles are successfully synthesized by a facile one-pot hydrothermal process. X-ray diffraction (XRD) and Field emission scanning electron microscopy (FESEM) reveal that the Tb3+ doped Na3FeF6 micro-particles with regular octahedral shape can be assigned to a monoclinic crystal structure (space group P21/c). Under ultraviolet light excitation, the Na3FeF6:Tb3+ octahedral particles given orange-red light emission originated from the 5D4→7FJ transitions of the Tb3+ ions. In addition, the magnetism measurement indicates that Na3FeF6:Tb3+ octahedral particles are paramagnetic with high magnetization at room temperature. Therefore, the Na3FeF6:Tb3+ powders may find potential applications in the biomedical field as magnetic-optical bi-functional materials.

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.

Hollow mesoporous Gd2O3:Eu3+ spheres with enhanced luminescence and their drug releasing behavior

Hollow mesoporous nanospheres Gd₂O₃:Eu³⁺ could be well fabricated by CCPS templates, which exhibited a durable drug release property.

Photoluminescence profiles and fast/slow annealing effects of Eu(III)/Tb(III)-codoped silica phosphor materials

A silica (SiO2) nanoparticle matrix was codoped with luminescent Eu(III) and Tb(III) ions using a modified Stöber method. The effects of fast and slow thermal annealing on photoluminescence profile imaging were examined. Slow annealing treatment suppressed more quenching sites than fast thermal annealing to further increase the photoluminescence signals. The photoluminescence signals observed between 450 and 720 nm were assigned to the (5)D(0)  → (7)F(J) (J = 0,1,2,3,4) of Eu(III) and the (5)D(4)  → (7)F(J) (J = 6,5,4,3) transitions of Tb(III). Photoluminescence was largely sensitized by indirect excitation and was much stronger than that generated by direct excitation. The Eu(III) and Tb(III) ions were doped at lower symmetry sites in the silica matrix.

Photoluminescence profile mapping of Eu(iii) and Tb(III → IV)-embedded in quantum size SnO2 nanoparticles

Eu(iii) and Tb(iv) activators were embedded in quantum size SnO₂ nanoparticles by a hydrothermal method and their morphologies, crystal structures and spectroscopic properties were examined by transmission electron microscopy, X-ray diffraction crystallography, UV-visible absorption, and 2D/3D-photoluminescence mapping.