The effects of metal doping (M = Cu, Ag and Eu) were investigated in nanostructured (M-TiO2) with the objectives to define the location of metal ions in the host matrices, identifying their stable ...valence states and environments as well as the incidence on the structural, electronic and optical properties of M-TiO2. Sol-gel method was used for the synthesis based on the reactants as metal-acetate and titanium alkoxide with defined experimental conditions to achieve the formation of nanostructured anatase phase with metallic doping ratios about 1, 2 and 3 mol.%. The investigations of doped structures were carried out by using x-ray diffraction, Raman spectroscopy, UV–Vis absorption and electron paramagnetic resonance (EPR) which contributes to precise insights on the metal behavior in M-TiO2. Correlations of the metal states such as the stable valence and local environments were made with the crystalline domains sizes, stability of anatase phase, electrical conductivity and optical features of the different M-TiO2 samples. The photocatalytic activity of 3 mol.% doped structures was compared through a heterogeneous photocatalysis carried out for the degradation of organic dyes in solutions under Xe-source irradiation. The efficiency of this process was discussed as function of the doping peculiarities.
Metal doping of TiO2 by Cu, Ag and Eu leads to the formation of different configurations for the metal environments as function of the metallic element and contribute to modulate the photoinduced electronic and optical responses of the doped structures. Display omitted
•The work reports a consistent analysis on the physical features of metal doped TiO2 by using Cu, Ag and Eu devoted to realize efficient photocatalysts.
This article reports on the properties of xerogel and aerogels of rare-earth with a hybrid matrix corresponding to the TTA/Er2O3/Eu2O3 system synthesized through the sol-gel method and the technique ...of supercritical drying at low temperature and characterization. A variant of the sol-gel method employing epoxide-assisted gelling and supercritical drying with CO2 was used, due to the efficiency and the fact that it can remove the solvent from the gels and yield ultra-porous materials. The morphology of TTA/Er2O3/Eu2O3 powders consist of agglomerates of irregularly shaped particles ranging from 100 nm to 1 μm in size. The use of the organic compound TTA does not change the cubic crystalline structure of the Er2O3:Eu2O3 powders. The results show a visible emission starting at a concentration of 2% when the material was excited to a wavelength of 613 nm, indicating a highly efficient energy transfer between the matrix and the rare earth which can be attributed to smaller crystal size and a large surface area. Due to the improvement of their spectroscopical properties, the hybrid powders are promising for use as sensors in medical and photoelectronic applications.
Hybrid materials based on lanthanide ions or lanthanide-doped nanostructured particles have received a lot of recent attention because organic ligands can sensitize RE ions via the “antenna effect.” ...With the aim of obtaining efficient emission via Eu
3+
ions, luminescent hybrid powders of Gd
2
O
3
:Eu
3+
were decorated with thenoyltrifluoroacetone (TTA) by the sol–gel method. This article reports on the influence of the organic ligand on the luminescent properties by varying the TTA: Gd
2
O
3
:Eu
3+
molar ratios: X:1 (
X
= 0.08, 0.16, 0.32, and 0.48). The precursors used to elaborate the TTA/Gd
2
O
3
:Eu
3+
hybrid systems were gadolinium and europium nitrates, with ethanol used as a solvent. Gd
2
O
3
:Eu
3+
, modified nanopowders were previously synthesized by the sol–gel process and heat-treated at 800 °C in the presence of Pluronic F-127; this fact was due to the observed enhanced luminescence intensity promoted by Pluronic F-127. For all of the hybrid systems, the x-ray diffraction results showed a Gd
2
O
3
:Eu
3+
-TTA cubic structure, without structural changes. FTIR studies revealed the presence of new bands besides those related to Gd–O, which suggests that Gd
2
O
3
:Eu
3+
was successfully capped by TTA. The TTA/ Gd
2
O
3
:Eu
3+
hybrid systems presented a stronger luminescence intensity than those of the non-hybrid systems; this effect is due to an energy transfer from the 2-thenoyltrifluoroacetone ligands to the Gd
2
O
3
:Eu
3+
particles. In this study, the effect of TTA on the structural, morphological, and luminescence properties of TTA/ Gd
2
O
3
:Eu
3+
hybrid systems was investigated.
(
a
) PL emission intensities Gd
2
O
3
:Eu
3+
, TTA: Eu
3+
(
b
) scheme of the TTA/Gd
2
O
3
:Eu
3+
system.
This study reports on the fabrication and characterization of luminescent aerogels of Gd
2
O
3
:Eu
3+
and Gd
2
O
3
:(Eu
3+
, Tb
3+
), synthetized by the sol–gel method and the supercritical drying ...technique. The mol% concentration of the Eu
3+
and Tb
3+
ions in the synthesis were varied to study the effects of concentration on the luminescent properties of the aerogels. The results show that the Gd
2
O
3
:Eu
3+
and the Gd
2
O
3
:(Eu
3+
, Tb
3+
) aerogels exhibited a maximum emission at
λ
= 613 nm. For all the samples, a decay in light intensity occurred when a concentration of 8 mol% of Eu
3+
was exceeded, regardless of whether the Tb
3+
ion was present. The analysis by X-ray diffraction showed that the aerogels of Gd
2
O
3
:Eu
3+
, like those of Gd
2
O
3
:(Eu
3+
, Tb
3+
), had a cubic crystalline structure with no change even at high concentrations of Eu
3+
. The microscopy analyses showed that the aerogels present a porous structure made up of interconnected quasi-spherical nanoparticles that formed a three-dimensional network. Quantum yield analysis shows that Tb
3+
acts as a sensitizer of Eu
3+
, increasing the light intensity in the aerogels. The results reveal that it is possible to manufacture luminescent aerogels of rare-earth oxides that can be used in opto-electronic devices.
Metal-organic frameworks (MOFs) have been synthesized using several elements, including the rare-earth. Research on luminescent diketones as an efficient alternative for the generation of OLEDs has ...increased in recent years, however, the evaluation of parameters such as morphology or excess of the cheating agent is not completely studied. In this work, the synthesis of thenoyltrifluoroacetone (TTA) combined with europium at the different chelating agent and rare earth ratio is presented, founding a change in morphology directed related with optical performance, structural analysis was performed using x-ray diffraction (XRD), and was observed a monoclinic structure in Eu 15% and Eu 20% samples. Morphological analysis was done with scanning electron microscopy (SEM). The TTA5Eu sample presented an irregular morphology with nanometric particles embedded, the TTA15Eu had a morphology of agglomerated particles, and TTA20Eu sample the morphology changes radically to an angular morphology. Nanowires were present in the sample of 25% Eu3+. The chemical properties were determined using Fourier transform infrared spectroscopy (FTIR), and the optical properties were measured by photoluminescence (FL). The results showed vibration bands and stretching of the thiophene group, without apparent change due to the chelation of the Eu3+.
A New Ultrafine Luminescent La2O3:Eu3+ Aerogel García Ramírez, Víctor M.; García Murillo, Antonieta; Carrillo Romo, Felipe de J. ...
Gels,
07/2023, Letnik:
9, Številka:
8
Journal Article
Recenzirano
Odprti dostop
This paper reports on the synthesis and characterization of La2O3:Eu3+ luminescent aerogels fabricated by the sol–gel method and the supercritical drying technique. The % mol concentration of the ...Eu3+ ion was varied to study the effects on the luminescent properties of the aerogels. XRD and TEM analysis showed that the La2O3:Eu3+ aerogels exhibited a semi-crystalline behavior regardless of whether the concentration of europium was increased. SEM micrographs revealed a porous structure in the aerogels, which were composed of quasi-spherical nanoparticles that were interconnected and formed coral-shaped agglomerates. Photoluminescence spectroscopy characterization showed that the aerogels had an infrared emission located at λ = 793 nm, and the maximum photoluminescence emission intensity was observed for the aerogel with 50% Eu3+. The results demonstrate that, without heat treatment, it is possible to manufacture luminescent aerogels of rare-earth oxides that can be used in opto-electronic devices.
The main drawbacks of fluorescent ZnO nanoparticles in practical optoelectronic applications are fast particle growth and agglomeration in water, causing a periodic decrease of light emission ...intensity. In this work, ZnO nanoparticles were successfully embedded within a silica matrix to prevent their agglomeration. The ZnO NPs were synthesized by the polyol method, using ethylene glycol and glycerol in sizes ranging from 5–6 nm. The as-obtained ZnO particles were dispersed in an amorphous silica matrix under three different ZnO:SiO
2
molar ratios: 20:80, 15:85 and 10:90. With the aim of enhancing the luminescent properties of the ZnO@SiO
2
composites, various annealing treatments in the range of 150–210 °C were carried out. The chemical analyses of the bare ZnO and the composites were carried out by Fourier transform infrared spectroscopy, which confirmed the presence of functional groups attached to the ZnO surface. By means of thermogravimetric analysis, it was determined that the evaporation of solvents shifted to lower temperatures (180 °C) when silica was added to the ZnO colloidal solution. By means of photoluminescence, a bright blue emission, centered at 440 nm, was observed in all of the samples, even at high temperatures (i.e., 210 °C); only a red shift of 20 nm was observed. Interestingly, the emission intensity of the sample 20:80, when annealed at 170 °C for 4 h, was enhanced 2.6 times, compared to the bare ZnO.
Graphical Abstract
F-127-Assisted Sol-Gel Synthesis of Gd2O3:Eu3+ Powders and Films Murillo, Antonieta García; Calderon, Víctor Hugo Colín; Romo, Felipe de Jesús Carrillo ...
Materials research (São Carlos, São Paulo, Brazil),
01/2019, Letnik:
22, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In the current work, the influence of Pluronic F-127 (S = F-127) and temperature on the luminescent properties of Gd2O3:Eu3+ (Gd:S = 1:2) powders and films was studied. In order to synthesize the ...powders and films (by the dip-coating technique), Gd2O3: Eu3+ (5 mol%) ceramics were elaborated by the sol-gel route, using gadolinium and europium nitrates as precursors. The results obtained by means of X-ray diffraction, confirmed the presence of the cubic structure of Gd2O3 (in 800 ºC heat-treated powders and 700 ºC heat-treated films), and crystals with nanometer sizes of ~19 nm, and ~15 nm, corresponding to the spherical and laminar-like morphologies of densified powders and films, respectively. Crystallites from the cubic and monoclinic structure were present on Gd2O3: Eu3+-modified films up to 800 ºC. Chemical identification of the bonds present in the films was performed by Fourier transform infrared spectroscopy, which identified representative infrared absorption at 543 cm-1, attributable to the Gd-O vibration. Photoluminescence studies showed that when the powders and films were heat-treated at 800 ºC, the intensity of their luminescence at the 5D0→7F2 Eu3+ transition (618 nm) was enhanced by the presence of F-127.
Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite Ba TiO3 consisting of spherical ...particles with diameters ranging from 10 to 30 nm was easily achieved by this route. In order to study the influence of the synthesis process on the morphology and the optical properties, barium titanate was also prepared by a solid-state reaction. In this case, only the tetragonal phase which crystallizes above 900 was observed. High-temperature X-ray diffraction measurements were performed to investigate the crystallization temperatures as well as the particle sizes via the Scherrer formula. The lattice vibrations were evidenced by infrared spectroscopy. Eu3+was used as a structural probe, and the luminescence properties recorded from Ba TiO3 :Eu3+and elaborated by a solid-state reaction and hydrothermal process were compared. The reddish emission of the europium is increased by the nanometric particles.
Display omitted
•Lu2O3:Eu3+, Tb3+ films were synthesized by sol–gel and by dip-coating technique.•Effects of annealing treatment on structural and optical properties were studied.•Optogeometrical ...characteristics of synthesized films were analyzed.•X-ray diffraction results showed that Lu2O3:Eu3+, Tb3+ crystallizes at 700°C.•High reddish emission on transparent films with at least 1μm thick was observed.
High-optical quality Lu2O3:Eu3+ 5mol%, X Tb3+ (X=0–0.04mol%) thin films were prepared by the sol–gel process and dip-coating technique. The procedure was as follows: lutetium, europium and terbium nitrates were used as precursors, and ethanol as a solvent. Etylenglycol (EG) was added as a sol stabilizer, and the pH was adjusted by acetic acid. After 10 dipping-cycles, followed by an annealing process (600–900°C) for 1h, transparent, smooth and crack-free films (ra=8–9nm) were formed. The X-ray diffraction (XRD) results showed crystallized films into the cubic structure at 800°C. The ellipsometry results showed that the thickness of the films varied from 1 to 1.4μm at 1000 and 600°C, respectively. Finally, the films presented a typical Eu3+ red emission at 611nm (5D0→7F2); furthermore, the effect of the Tb3+ content showed that the highest emission intensity corresponded to the lower Tb3+ content.
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