YF3:Tb, LaF3:Ce/Tb, and GdF3:Tb nanoparticles (NPs) were synthesized by the thermal co-precipitation technique at a lower temperature. X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), FT-Raman, UV/visible, and photoluminescence techniques were utilized to determine the phase purity, crystal phase, thermal stability, exterior behavior, optical properties, colloidal stability, and luminescent properties. The XRD results showed the different crystal phases in each nanoproduct. The TGA studies exhibited slight degradation at a lower temperature, which suggests surface water adsorption and organic moieties. The FTIR spectra revealed the existence of the IR bands related to hydroxyl and (C O) groups, suggesting the presence of organic moieties. The absorption spectra and optical bandgap energies were measured in aqueous media for the determination of the colloidal dispersibility in an aqueous solution. The excitation and emission spectra were analyzed, and all observed excitation and emission transitions were labeled. The emission spectra of the LnF3:Tb NPs exhibited distinctive features of the most dominant emission transition located at 543 (5D4 → 7F5) under the excitation at 368 nm. Among the presented LnF3 host matrices, YF3:Tb NPs demonstrated high crystallinity along with superior photoluminescence properties. These findings are highly useful in the conjugation of biomolecules for sensitive detection of biomolecules and optical bioimaging. 相似文献
Lighting‐up time : A cation‐exchange reaction releases thousands of divalent cations from nonfluorescent CdSe ionic crystals and triggers fluorescence from thousands of originally nonfluorescent Fluo‐4 fluorophores to obtain a large fluorescence amplification (see picture) and a low detection limit in bioassays. The technique is fast, simple, with a large dye‐to‐reporter labeling ratio, and flexible in selection of nanocrystals and fluorophores.
The vacuum ultraviolet (VUV) spectroscopic properties of praseodymium (Pr3＋, 1at%) doped LaF3 nanocrystals/glass at room temperature and 20 K are reported. Two types of Pr3＋ ions, those in LaF3 nanocrystals and those in the glass host, were excited to 4f 5d band by VUV using synchrotron radiation as an excitation source, and emissions of 1S0 → 1D2 (336 nm), 1S0 → 1I6 (397 nm ) of Pr3＋ in the nanocrystals and emissions of 4f 5d → 3HJ, 3FJ of Pr3＋ in the glass appeared at the same time. But unlike in the bulk sample crystals, emission of 3P0 → 3HJ, 3FJ as the second step of the quantum splitting (QS) of Pr3＋ in the LaF3 nanocrystals was not observed at room temperature, which could be explained that Pr3＋ ions in the glass absorbed the energy of 3P0→ 3H4 of Pr3＋ in the nanocrystals. Two types of excitation spectra monitoring different emissions were also measured, so it could be observed that the lowest energy of 4f 5d band of Pr3＋ in the nanocrystals was about 53 500 cm-1 (186 nm) and in the glass about 33 800 cm-1(295 nm), respectively. These emission and excitation spectra were contrasted to those of bulk sample crystals LaF3∶Pr3＋. 相似文献
ZnO nanocrystals are synthesized using the quenching method. The properties of the grown nanocrystals are studied using ultraviolet-vis spectroscopy, x-ray diffraction, photoluminescence, electron diffraction, energy dispersive x-ray spectroscopy, and high resolution transmission electron microscopy. Current-voltage characteristics of the prepared samples are studied for investigating the possible application of the samples as switch and memristor. 相似文献
