Developing photocatalytic nanomaterials with improved physicochemical properties (broader light absorption range, high visible light-induced photoactivity, large adsorption capacity, and tailored defects density) and pollutants removal efficiency is important for different photochemical applications, especially emerging pollutants remediation. In this study, visible light active SnS2 nanosheets co-doped with 1.5 mol% Er3+ and 3 mol% Yb3+ (coded as SEY) were synthesized via hydrothermal method and applied for the photocatalytic degradation of three different antibiotics, tetracycline hydrochloride (THC), sulfamethazine (SMZ), and sulfadiazine (SDZ), under visible LED irradiation. Compared to pristine SnS2 (kobs = 0.006 min-1), the doped SEY exhibited 3.5 times higher removal efficiency (kobs. = 0.021 min-1), removing 95 % of THC and 89 % of SMZ after 120 min. The RE doping induced the formation of structural defects (stacking faults and interstitial defects) confirmed by HR-TEM and EELS, which contributed to improved extended visible light absorption. Thermal treatment of SEY samples at 350 degrees C and 750 degrees C resulted in the formation of SEY_350 (SnS2/SnO2) and SEY_750 (SnO2), respectively, indicating partial and complete phase transformation. Annealing-induced crystallization into nanostructured cassiterite SnO2 resulted in marked decrease in photocatalytic activity (kobs. = 0.004 min-1), due to its wider band gap (3.6 eV) and reduced visible light absorption. EPR spin-trapping with DMPO revealed the formation of both hydroxyl and superoxide radicals in the degradation process, while the involvement of photogenerated holes (h+) was confirmed through scavenger experiments using EDTA. These results indicate that multiple reactive oxygen species contribute synergistically to the degradation of antibiotics. These findings demonstrate that RE ion doping effectively tunes the structural defects and visible-light-driven photocatalytic response of SnS2, enabling its application as an efficient dual-function adsorbent-photocatalyst for the removal of antibiotics in water treatment applications.

Phase control in rare earth tantalates is an effective strategy to tailor their scintillation performance. Here, undoped and Tb3+-doped yttrium tantalates were synthesized via sol-gel method. Their structural, photo- and radio-luminescent properties were investigated as a function of the annealing temperature (900-1300 degrees C) and Tb3+ concentration (ranging from 0.5 to 5.0 mol %). X-ray diffraction and Rietveld refinements reveal that Tb3+ incorporation stabilizes the cubic Y3TaO7 phase, whereas elevated annealing temperatures promote the monoclinic M '-YTaO4 phase. Undoped samples exhibit intense blue photoluminescence (similar to 450 nm) when excited at their band gap, arising from TaO6 groups, most pronounced when the M ' phase dominates. Tb3+ doping results in an intense green emission (similar to 542 nm, D-5(4)-> F-7(5)), with concentration-dependent D-5(4)/D-5(3) population dynamics. Under X-ray excitation, both undoped and Tb3+-doped samples exhibited intense luminescence, which was shown to be strongly dependent on the predominant crystalline phase and TaO6 mediated charge transfer. Thermoluminescence measurements reveal stable charge traps. These results establish Tb3+-doped yttrium tantalates as promising scintillators combining photo-, radio-, and thermoluminescence for advanced applications such as high-resolution X-ray imaging and photodynamic therapy enhancement.

This study reports the synthesis, structural, and spectroscopic characterization of Eu3+-doped yttrium stannate prepared by coprecipitation followed by thermal annealing at temperatures ranging from 700 to 1300 degrees C. All the samples contained pyrochlore Y2Sn2O7, and the crystallization degree increased with an increasing temperature. The Eu3+ emission spectra were used to follow the structural changes. For the sample annealed at 700 degrees C, inhomogeneous broadening resulted from Eu3+ distribution in a significantly disordered low-symmetry environment. As the annealing temperature increased, the spectral profile became sharper, and the band due to the 5 D 0 -> 7 F 1 transition stood out, revealing that Eu3+ occupied a centrosymmetric site (D3d). Site-selective excitation was observed through the 5 D 0 -> 7 F J (J = 0, 1, 2, 3, and 4) transitions under different excitation wavelengths. The samples exhibited potential for excitation in the green region (525 nm) and a long 5 D 0 excited state lifetime as the pyrochlore is stabilized. The outstanding results showed these materials have promising photonic applications, especially in imaging via time-resolved luminescence analysis.

This work reports, for the first time, the development of Er3+/Yb3+ co-doped Y2Sn2O7 as a high-performance optical material, exhibiting long-lived emissions and outstanding thermometric properties which enable its use as a primary thermometer. The materials were synthesized via a coprecipitation method and exhibited a dominant pyrochlore phase, as confirmed by X-ray diffraction analysis. Photoluminescence measurements revealed intense downshifting and upconversion emissions under both 980 nm and 1550 nm excitation. Remarkably, the 4I13/2 excited-state lifetime of Er3+ reached values up to 20 ms, while the upconverted emissions from the Er3+ 4S3/2 and 4F9/2 levels exhibited excited-state lifetimes as long as 1.4 ms, demonstrating strong potential for time-gated bioimaging applications. Thermometric performance evaluation revealed that the Er3+/ Yb3+ -doped Y2Sn2O7 operates as an exact primary luminescent thermometer, achieving a notable relative thermal sensitivity (1.37 +/- 0.01 % K-1 at 293 K), with repeatability exceeding 96 %. Furthermore, the system displayed excitation- and annealing-dependent chromatic tunability, transitioning from orange to green with an increasing annealing temperature, along with the pure red emission under 1550 nm excitation, highlights its versatility for multiplexed optical applications. These results position Y2Sn2O7: Er3+/Yb3+ as a promising platform for advanced photonic technologies, including high-resolution thermal sensing and deep-tissue optical bioimaging.

We synthesized Er 3+ and Yb 3+ co -doped tantalum oxide (Ta 2 O 5 ) spherical sub -micrometric particles by a facile method involving formation of tantalum glycolates after pouring in acetone. Then, we investigated how the annealing temperature and Yb 3+ concentration (0-30 mol %) affect their structural and luminescence properties. Particle sizes ranged from 146 to 258 nm for the samples annealed at 800 degrees C. XRD analysis revealed the orthorhombic L-Ta 2 O 5 crystalline structure. The different symmetry sites that the rare earth ions can occupy within the Ta 2 O 5 structure led to intense and broad emission bands centered around 1530 nm. Up -conversion measurements and the calculated number of photons for intense green and red emissions obtained with 980 and 1550 nm excitations helped us to elucidate the mechanisms involved at both excitation wavelengths. We investigated how the 0.5 mol % Er 3+ /1.5 mol % Yb 3+ co -doped Ta 2 O 5 sample performs as a primary thermometer by using the Boltzmann distribution law to predict the absolute temperature from the ratio between the Er 3+ 2 H 11/2 -> 4 I 15/2 and 4 S 3/2 -> 4 I 15/2 transitions. We obtained a maximum relative thermal sensitivity of 0.97 +/- 0.04 % K -1 and a minimum delta T of 2.41 K. The calculated repeatability was above 95%. These results show that promising nanothermometer based on Ta 2 O 5 with controlled size and morphology can be designed.

We have synthesized Er3+,Yb3+ co-doped lanthanum niobate samples by a sol-gel route and investigated their luminescent properties under different excitation sources aiming at applications in Biophotonics. The samples were crystalline and composed primarily of orthorhombic La3NbO7 with secondary formation of monoclinic LaNbO4. We verified NIR-to-visible upconversion with the naked eye under excitation at 980 and 1550 nm; emission in the green and red regions prevailed, respectively. X-ray excitation revealed prevalent emission in the blue region, attributed to the luminescence of NbO43- groups in the lattice, as well as Er3+ emissions in the visible range. All the samples presented high relative thermal sensitivity (above 1.32 % K- 1) and repeatability above 97 % between 243 and 293 K. Based on the investigated luminescent properties, the samples prepared herein are versatile materials with a wide range of potential applications as scintillators, optical markers, energy converters for photodynamic therapy, and nanothermometers.

We synthesized Er3+ and Yb3+ co-doped tantalum oxide (Ta2O5) spherical sub-micrometric particles by a facile method involving formation of tantalum glycolates after pouring in acetone. Then, we investigated how the annealing temperature and Yb3+ concentration (0-30 mol %) affect their structural and luminescence properties. Particle sizes ranged from 141 to 260 nm for the samples annealed at 800 °C. XRD analysis revealed the orthorhombic L-Ta2O5 crystalline structure. The different symmetry sites that the rare earth ions can occupy within the Ta2O5 structure led to intense and broad emission bands centered around 1530 nm. Up-conversion measurements and the calculated number of photons for intense green and red emissions obtained with 980 and 1550 nm excitations helped us to elucidate the mechanisms involved at both excitation wavelengths. We investigated how the 0.5 mol % Er3+/1.5 mol % Yb3+ co-doped Ta2O5 sample performs as a primary thermometer by using the Boltzmann distribution law to predict the absolute temperature from the ratio between the Er3+ 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions. We obtained a maximum relative thermal sensitivity of 0.97 ± 0.04 % K-1 and a minimum δT of 2.41 K. The calculated repeatability was above 95%. These results show that promising nanothermometer based on Ta2O5 with controlled size and morphology can be designed.

Undoped and Eu3+-doped yttrium tantalates were synthesized via sol–gel method. Refined X-ray diffraction, Raman spectroscopy, and low-temperature photoluminescence measurements were employed for conclusive RE3TaO7 crystalline phase asignment.

Synthesis, structural and spectroscopic properties of Ln3+ (Ln= Eu, Er and Yb) in Y2Sn2O7 materials synthesized by co-precipitation, calcined at 700, 900 and 1100 °C using as precursors the Tin (IV) chloride pentahydrate, yttrium chloride and ammonium hydroxide.

The growing demand aiming non-invasive diagnosis techniques applications has become an emerging field for developing more efficient bioprobes working in the near infrared (NIR) biological windows. In this work, we propose Er3+/Yb3+ co-doped yttrium niobate as a multifunctional material synthesized via sol-gel method. We study its NIR emission under UV excitation (down-shifting) and NIR-to-visible upconversion (UC) emission and exploit this material as a luminescent thermometer. X-ray diffraction analysis points out the formation of cubic Y3NbO7 crystalline phase after annealing at 1100 degrees C. Intense and narrow 1.5 mu m emission (FWHM ~24 nm) with Er3+ 4I13/2 lifetime value of ca. 5.5 ms are observed under excitation in the host absorption band (276 nm), due to down-shifting process. Down-shifting and upconversion quantum yields (QY) with excitation at 980 nm were reported for the first time for Y3NbO7 material with values of ca. 18% and ca. 0.0020% in the NIR and visible ranges, respectively. Y3NbO7 is a luminescent primary thermometer with maximum relative thermal sensitivity of 1.31 +/- 0.06% K-1, temperature uncertainty of 0.31 K, and repeatability of 99.6%. Furthermore, the relatively high QY values in NIR and UC emission, comparable to fluorides and higher than other oxides, make Er3+/Yb3+ co-doped yttrium niobate an interesting multifunctional probe aiming for biological applications.

We report high incorporation of rare earth ions (RE3+) into hafnia nanoparticles prepared by the sol–gel method and investigate how these dopants affect hafnia structure and phase transformation. An ethanolic suspension containing 5-nm hafnia nanoparticles was obtained from HfOCl2.8H2O in ethanol. Pure and 0.1–7 mol% Eu3+-doped materials afforded HfO2 monoclinic phase, whereas hafnia nanoparticles added with 10 and 20 mol% Eu3+ were stabilized in the tetragonal phase. Structural evolution of the nanoparticles was analyzed by Eu3+ luminescence spectroscopy and excited level lifetimes. The emission spectra in the visible region showed an increase of the Eu3+ site symmetry due to hafnia phase transformation from monoclinic to tetragonal upon increasing Eu3+ concentration. Concentration quenching, followed by lifetime measurements, occurred at high Eu3+ concentration (20 mol %). The hafnia tetragonal phase was stabilized with non-optically active La3+ (a fixed concentration of 10 mol %), co-doped with a lower concentration of Eu3+ ions (from 0.1 to 3 mol %). This strategy ensured that Eu3+ luminescence in tetragonal hafnia was intense and prevented quenching by the high Eu3+ concentration. In this sense, the hafnia structure and emission properties can be tailored by the RE3+ concentration, so that an interesting material for applications in photonics and biophotonics can be achieved.

The objective of this work is to evaluate the optically stimulated luminescence (OSL) lifetimes of different polycrystalline CaB6O10:Ln, Agx (Ln = Gd, Tb and Ce; x: % molar concentration) compounds. For the determination of the luminescence lifetimes, time-tagged time-resolved (TTTR) data of the OSL under pulsed stimulation were analyzed. In addition, OSL emission spectra of the samples were recorded to correlate the emission bands with the estimated lifetimes. Whereas single Ce-doped compound presented a fast dominant component (tau < 0.41 mu s, -63% of the signal), single Gd-doped compound exhibited a slow dominant component (tau = 2.3 ms, -67% of the signal). All Ag-codoped compounds (except for the Ce-Ag-codoped compound) presented a common dominant component with a -43 mu s lifetime, which is ascribed to a broad emission centered at -330 nm. Both lifetimes and OSL emission spectra for the Gd-Ag-codoped compounds suggest that two luminescent centers compete for the radiative recombinations, confirming previous reported results. The relative Gd and Ag molar concentrations also had a strong influence in the estimated luminescence lifetimes of the slow component, probably due to the introduction of shallow trapping centers by silver doping. Furthermore, the temperature dependence of the common luminescence in Ag-codoped compounds appeared to be in agreement with the MottSeitz model for luminescence quenching. This work provides a better understanding of the physical processes and dynamics behind the radiative recombinations linked to OSL in borate compounds.

This study investigates how rare earth ion (RE3+) concentration affects stabilization of the crystalline structure and infrared-to-visible upconversion (UC) in Er3+/Yb3+ co-doped yttrium tantalates, synthesized by the sol–gel method. Under 980 nm, the samples exhibited intense UC luminescence. The crystalline phases strongly influenced the emission color of UC luminescence. The sample consisting of pure Y3TaO7 phase had a yellowish-green color, but a greener emission appeared in the presence of a small amount of M’-YTaO4. Increasing the RE3+ concentration influences the Y3TaO7 crystalline phase stabilization, as well as in the color tunability, since cross-relaxation processes take place, enhancing red emission intensity. This is the first report of UC quantum yield (UCQY) for yttrium tantalate samples (up to 0.016 ± 0.002%). Samples doped with Er3+/Yb3+ 0.5/1.5 mol % annealed at 900 or 1100 °C were successfully developed as primary thermometers. The temperature of these materials can be predicted without any calibration through the Boltzmann law, using the ratio of the intensity of transitions of Er3+. The maximum relative thermal sensitivity was 1.31 ± 0.05% K−1, which was higher than the sensitivity reported for other oxides. Nanothermometer repeatability was 98.8% and 99.8%, with minimum temperature uncertainty of 0.93 and 0.87 K for samples annealed at 900 and 1100 °C, respectively. The great tunability properties, UCQY values, and nanothermometry results indicated that primary thermometers can be implemented by using Er3+/Yb3+ co-doped yttrium tantalate upconverting nanoparticles for biophotonic applications in temperature sensing and deep tissue imaging.

In recent years, the use of quantum dots (Qdots) to obtain biological images has attracted attention due to their excellent luminescent properties and the possibility of their association with contrast agents for magnetic resonance imaging (MRI). In this study, Gd3+/ZnO (ZnOGd) were conjugated with Qdots composed of a gadolinium-copper-indium-sulphur core covered with a ZnS shell (GCIS/ZnS Qdots). This conjugation is an innovation that has not yet been described in the literature, and which aims to improve Qdot photoluminescent properties. Structural and morphological Qdots features were obtained by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analyses (TGA). The photoluminescent properties were examined by emission (PL) and excitation (PLE) spectra. A new ZnOGd and GCIS/ZnS (ZnOGd-GCIS/ZnS) nanomaterial was synthesized with tunable optical properties depending on the ratio between the two native Qdots. A hydrophilic or lipophilic coating, using 3-glycidyloxypropyltrimethoxysilane (GPTMS) or hexadecyltrimethoxysilane (HTMS) on the surface of ZnOGd-GCIS/ZnS Qdots, was carried out before assessing their efficiency as magnetic resonance contrast agents. ZnOGd-GCIS/ZnS had excellent luminescence and MRI properties. The new Qdots developed ZnOGd-GCIS/ZnS, mostly constituted of ZnOGd (75%), which had less cytotoxicity when compared to ZnOGd, as well as greater cellular uptake.

A dual tunable visible (reddish, orangish, blueish and white emission) and near infrared energy conversion in Pr3+-doped yttrium tantalate prepared by sol-gel method were observed depending on the ratio of radiative transitions from the P-3(0) and D-1(2) excited states. The Pr3+ concentration influences the crystallization process of cubic Y3TaO7 and monoclinic M'-YTaO4 crystalline phases as attested by X-ray diffraction and Raman spectroscopy. Increasing the lanthanide concentration, the Y3TaO7 crystalline phase is stabilized, delaying the formation of the M'-YTaO4 one. Spectroscopic studies revealed a pronounced near-infrared (NIR) emission of Pr3+ ions, ascribed to D-1(2)-> F-3(3,4) transition, under ultraviolet (UV) and visible excitation. Changes in the emission profile were also noticed and could be correlated with the crystalline structure. A reduced multiphonon relaxation from the P-3(0) to the D-1(2) was observed due to the low phonon energy of the host. An intense blue emission (P-3(0)-> H-3(4)) was detected, which is increased in comparison to the red emission, for higher dopant concentration. Samples containing the highest Pr3+ concentration (5.0 mol %) exhibited a luminescence quenching on the visible and NIR transitions from the D-1(2) level indicating the influence of a cross-relaxation process on depopulating the D-1(2) level and tuning the color emission. All the above-mentioned structural and luminescent properties make these yttrium tantalates potential candidates for Photonic applications, especially as red-orangewhite-blue light emitters and as energy converters for the enhancement of commercial Si solar cell efficiency.

Flexible coatings with dual capabilities for remote real-time temperature sensing and photothermal conversion have a huge potential in the field of advanced thermal actuated optoelectronic applications. In this work, we demonstrated that plastic free-standing films of Er3+/Yb3+-codoped GeO2-Ta2O5 particles dispersed in poly(methyl methacrylate) (PMMA) having intriguing upconversion high absolute emission quantum yield (similar to 0.1452, excited at 980 nm, 760 W.cm(-2)) can simultaneously operate as photothermal converters and real-time primary thermometers. The emission of the films was studied at the microscale, revealing emission homogeneity detected through surface hyperspectral microscopy. One factor that contributes to the unusually high absolute emission quantum yield, when compared with other oxides-based materials, is the high occurrence (probability) of the shortest Yb-Er distances obtained when the YbTaO4 phase is formed. This, as demonstrated by computational simulations of doping processes, favors the Yb-to-Er energy transfer rates, enhancing the population of the Er3+ emitting levels. Besides, the films combined a relative thermal sensitivity of similar to 1.1% K-1 (at 300 K) with a temperature uncertainty of similar to 0.7 K and a maximum photothermal efficiency of similar to 44%, which permits the prospect of using this material as a coating with photothermal and thermometer functions. Moreover, as an added benefit, the thermal resistance of the composite in PMMA was estimated, yielding a maximum value of 760 +/- 8 K.W-1. This is the first example of an active coating for photothermal conversion with the simultaneous ability to remotely sense temperature that can be explored in NIR-pumped free-space telecommunications without the need of additional optoelectronics devices.

We report the synthesis of a Y3TaO7 solid solution containing a high Eu3+ concentration (from 7 up to 50 mol%) and investigate how Eu3+ influences the Y3TaO7 crystallization process. To this end, we evaluate the Y3TaO7 structural features and photoluminescence properties after Eu3+ introduction into the Y3TaO7 lattice. The higher the Eu3+ ion concentration, the more stable the crystallization process of the Y3TaO7 phase seems to be. The Eu3+-containing Y3TaO7 displays intense orange-reddish, broad band emission because Eu3+ occupies different symmetry sites in the host and causes inhomogeneous broadening. Eu3+ emission quenching due to Eu3+ concentration is negligible up to 30 mol% and absolute quantum yield values of up to nearly 30% were obtained, making Eu3+-containing Y3TaO7 interesting materials for application as high-intensity emitters in photonics.

This study reports the synthesis and the structural and spectroscopic characterization of Eu3+-doped yttrium tantalate prepared by a new sol-gel method, which affords the orthorhombic Y3TaO7 and monoclinic YTaO4. Eu3+ doping influences the crystallization kinetics; its presence delays YTaO4 formation. Spectroscopic studies and their correlation to the structural features were the basis to understand the high quantum efficiency and no evidence of concentration quenching and clustering formation of Eu3+ ions. Inhomogeneous broadening in the emission spectra is due to Eu3+ distribution in different Y3TaO7 symmetry sites. Higher YTaO4 content increases the ratio between the D-5(0)-> F-7(2) and D-5(0)-> F-7(1) transition intensities, suggesting that Eu3+ occupies relatively lower symmetry sites as compared to Eu3+ distribution in the Y3TaO7 phase. No quenching occurs even for samples containing the largest Eu3+ concentration (up to 5.0 mol%), which strongly indicates high Eu3+ solubility within the yttrium tantalate host and absence of Eu3+ clusters. In addition to its application as structural probe, high quantum efficiency values combined with enhanced emission intensity make Eu3+-doped yttrium tantalate a suitable red luminophore.