Next Article in Journal
High-Pressure Monosulfide Solid Solution FexNi1−xS Phases: X-Ray Diffraction Analysis and Raman Spectroscopy
Previous Article in Journal
Nanoporous Copper Films: How to Grow Porous Films by Magnetron Sputter Deposition
Previous Article in Special Issue
A Novel Synthesis Method of Dumbbell-like (Gd1−xTbx)2O(CO3)2·H2O Phosphor for Latent Fingerprint
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Crystals
Volume 14
Issue 11
10.3390/cryst14110966
crystals-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions

by
Anna S. Petrova
1,
Oleg S. Butorlin
1,
Yulia N. Toikka
1,
Ilya E. Kolesnikov
1,
Sergey N. Orlov
1,2,
Mikhail N. Ryazantsev
1,3,
Nikita A. Bogachev
1,
Mikhail Yu. Skripkin
1 and
Andrey S. Mereshchenko
1,*
1
Saint Petersburg State University, 7/9 Universitetskaya emb., Saint Petersburg 199034, Russia
2
Institute of Nuclear Industry, Peter the Great St. Petersburg Polytechnic University (SPbSU), 29, Polytechnicheskaya Street, Saint Petersburg 195251, Russia
3
Nanotechnology Research and Education Centre RAS, Saint Petersburg Academic University, ul. Khlopina 8/3, Saint Petersburg 194021, Russia
*
Author to whom correspondence should be addressed.
Crystals 2024, 14(11), 966; https://doi.org/10.3390/cryst14110966
Submission received: 16 October 2024 / Revised: 29 October 2024 / Accepted: 5 November 2024 / Published: 8 November 2024
(This article belongs to the Special Issue Synthesis and Crystal Structure of Rare-Earth Metal Compounds)
Browse Figures
Versions Notes

Abstract

:
The structural features and luminescent properties of heterometallic Tb–Gd, Tb–La, and Tb–Y terephthalate metal–organic frameworks, namely (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Gd, La, Y), were studied in detail in a wide concentration range (x = 0.001–1). The crystalline phase of synthesized compounds corresponds to Ln2(1,4-bdc)3·4H2O. The lifetime of 5D4 decreased with increased Tb3+ concentration, but PLQY depends non-linearly on the Tb3+ concentration. The 50% substitution of Tb3+ for Y3+, Gd3+, or La3+ ions result in the significant enhancement of photoluminescence quantum yield, up to 1.6 times. The morphology, thermal stability, and vibrational structure of the selected homo- and bi-metallic materials is reported as well.

1. Introduction

Metal–organic frameworks (MOFs) are porous materials consisting of networks of metal ions or clusters connected to each other with organic ligands with several donor atoms. These materials have received much attention in the last two decades due to their pronounced crystallinity, porosity, high stability, and diversity in structures and topologies. Rare earth element (REE)-based MOFs are of particular relevance, since their luminescent properties strongly depend on the type of lanthanide ion. The development of REE-based MOFs that exhibit strong luminescent properties is a relevant and promising area of research. These REE-MOFs can be used in LEDs, luminescent sensors, contrast agents for imaging, catalysts, and analytical tools to detect harmful substances in food, drinking water, and the environment [1,2,3,4,5,6,7,8,9]. Compounds based on europium and terbium are particularly popular due to their bright red and green light emission, respectively. Thus, OLEDs based on metal–organic terbium compounds were recently reported in numerous works [10,11,12,13]. In addition, heavy metal ions efficiently quench the photoluminescence of Tb3+ compounds, such as mercury, bismuth, and chromium, as well by organic substances such as gossypol, acetone, sulfamerazine, and other molecules [14,15,16,17,18], which indicates Tb3+ compounds as promising materials for the development of luminescent turn-off sensors for the abovementioned compounds.
The direct photoexcitation of lanthanide ions is inefficient because 4f–4f transitions are not allowed according to Laporte’s rule. This challenge can be overcome by employing energy transfer from an electronically excited ligand to one of the atomic level of the lanthanide ion (“antenna effect”) [19,20,21]. The “antenna” organic ligands usually possess high UV extinction coefficients, strongly coordinate with REE ions, and efficiently transfer energy to REE ions. Accordingly, aromatic carboxylates, such as 1,4-benzenedicarboxylate (terephthalate, 1,4-bdc) and their various derivatives, have become the most frequently used ligands [22,23,24,25].
The presence of both luminescent and non-luminescent ions of rare earth elements in REE-MOFs can have a substantial impact on the structural and optical properties of these compounds. The doping effect on the structure of heterometallic REE–metal–organic frameworks (MOFs) has been explored in multiple studies. Usually, the crystalline structure is not alternated when a small fraction of one lanthanide is substituted for another one in the same oxidation state. The significant doping amount by another lanthanide ion, however, can result in crystalline phase change. Thus, Jarley Nascimento et al. demonstrated [26] that the compounds Gd1−xEux(1,4-bdc)3(dmf)2(H2O)n (dmf—dimethylformamide; x = 0.01, 0.03, 0.05, 0.07, 0.09) are isostructural, with [Eu2(1,4-bdc)3(dmf)2(H2O)] at the Eu3+ content between 1 and 7 at.%. Meanwhile, at the Eu3+ concentration of 9 at.%, the obtained material possessed a structure of [Eu2(1,4-bdc)3(dmf)2(H2O)2]. In our previous works, we observed the crystalline phase alternation in (EuxLu1−x)2(1,4-bdc)3‧nH2O and (TbxLu1−x)2(1,4-bdc)3‧nH2O MOFs [27,28,29,30]. Substitution of up to 90% of Eu3+ or Tb3+ by Lu3+ ions does not affect the crystalline phase of the resulting compounds, Ln2(1,4-bdc)3·4H2O, which is isostructural to europium and terbium terephthalates, namely Eu2bdc3·4H2O and Tb2bdc3·4H2O, correspondingly. At a lutetium content of more than 98%, the synthesized compounds possessed a Ln2(1,4-bdc)3, Ln2(1,4-bdc)3·10H2O, or Ln2(1,4-bdc)3·2.5H2O crystalline phase depending on the concentration of the initial reagents. We observed that the particle morphology and optical properties, such as fine structure of emission spectra, photoluminescence quantum yields (PLQY), and lifetime values, are more significantly affected by the crystalline phase than by the concentration of the luminescent lanthanide ion (Eu3+ or Tb3+). In spite of the fact that the alternation of the crystalline phase significantly affects the photoluminescence of REE-MOFs, the optical properties of heterometallic MOFs also depend on the concentration of the luminescent ion within one crystalline phase in cases of isomorphic substitution of the luminescent REE ion to the optically inactive one. However, only a few studies have studied such concentration dependences. In our previous work, for (EuxM1−x)2(1,4-bdc)3∙4H2O (M = Gd, La, Y) MOFs, we demonstrated that, at larger Eu3+ concentrations, for the Eu–Y and Eu–La series, PLQY remains the same (about 9–11%), whereas in the Eu–Gd series, it reaches a maximum of 15% at the Eu3+ content of 10 at.% and then slightly decreases, reaching 10% in homometallic europium(III) terephthalate [31]. Utochnikova et al. previously reported the Gd3+ and Y3+ doping effect on the optical properties of heterometallic solid solutions of (TbxY1−x)2(1,4-bdc)3(H2O)4 and EuxGd1−x(dbm)3(phen) (dbm—dibenzoylmethanate, phen—o-phenantroline) MOFs [24]. A steep increase in quantum yield was observed at the low concentration regions of Eu3+ or Tb3+ ions. For the abovementioned heterometallic coordination polymers, when the concentration of luminescent ions (Tb3+ or Eu3+) exceeded 20%, the quantum yield remains the same; meanwhile, the excited state lifetime decreases with increasing concentrations of the luminescent ion [32]. However, the structural features were not studied in detail in the mentioned study [32], and the authors studied the doping effect only by one REE, namely Y3+ in cases of Tb3+-based terephthalates. Bimetallic terephthalates of equimolar compositions are reported by Tarek Alammar et al. [33]. The authors studied the several heterometallic terephthalates, namely (Ln0.5Gd0.5)2(1,4-bdc)3·4H2O (M = Eu, Tb, Sm). Despite their detailed analysis of the optical properties of these compounds, this work considered the dilution of only one non-luminescent ion (gadolinium) and only in one concentration. In the article by Victor Haquin et al. [34], the researchers investigated the systems (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, La, Gd) for their fluorescent and structural properties. However, in their work, more attention was paid to tri-metallic systems and systems containing Eu3+ and Tb3+, and bimetallic systems with luminescent and non-luminescent ions were viewed fluently. The authors give a large series of synthesized compounds of the series (TbxGd1−x)2(1,4-bdc)3·4H2O (x = 0.05–100), the details of their optical properties on selected samples, and luminescence spectra for all. At the same time, the series containing Y and La has received much less attention; for lanthanum (III)’s intensity of luminescence, there is no information for yttrium (III). In our work, we not only expanded the range of concentrations towards their reduction (x = 0.001–0.04), but also studied in detail the structural features, morphology, vibration structure, thermal stability, fine structure of the emission bands, excited state kinetics, and photoluminescence quantum yields. It is worth noting that our measurement results differ from those presented in the previous work, and the goal of our work is to carefully demonstrate the dependence of the above properties of the terephthalate of the terbium (III) on the degree and nature of substitution by ions of optically inactive rare earth elements.
Thus, in the current work, we studied in detail the doping effect of the various non-luminescent ions (Y3+, Gd3+, and La3+) both on the structure and on the luminescent properties of Tb3+-based heterometallic terephthalates (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Gd, La, Y; x = 0.001–1) in a wide concentration range, and, contrary to previous work [32], demonstrated that 50% substitution of Tb3+ for Y3+, Gd3+, or La3+ ions results in the significant enhancement of photoluminescence quantum yields, up to 1.6 times. Also, morphology, thermal stability, and vibrational structure of the selected homo- and bi-metallic materials is reported.

2. Materials and Methods

Terbium (III) chloride hexahydrate, yttrium (III) chloride hexahydrate, gadolinium (III) chloride hexahydrate, and lanthanum (III) chloride hexahydrate were purchased from Chemcraft (Kaliningrad, Russia). 1,4-benzenedicarboxylic (terephtalic, H2(1,4-bdc)) acid (>98%), sodium hydroxide (>99%), nickel (II) chloride hexahydrate (>99%), and EDTA disodium salt (0.1 M aqueous solution), and murexide were purchased from Sigma-Aldrich Chemie GmbH (Taufkirchen, Germany) and used without additional purification.
The heterometallic terephthalate compounds with a general formula of (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, Gd, La) were prepared by mixing 0.2 M TbCl3 and 0.2 M MCl3 (M = Y, La, or Gd) with 2 mL of 0.3 M Na2(1,4-bdc) aqueous solution. The TbCl3 and MCl3 solutions were mixed in stoichiometric amounts, and the total volume of the solutions was 1 mL. The resulting white precipitates were separated from the mixture using centrifugation at 4000× g and washed three times with deionized water. The samples were then dried at 60 °C. The Tb3+/M3+ (M = Y, Gd, La) ratios in the heterometallic terephthalates were confirmed using energy-dispersive X-ray spectroscopy (EDX) (EDX spectrometer EDX-800P, Shimadzu, Japan). The Tb/M (M = Y, Gd, La) ratios obtained from EDX were consistent with the expected ratios of Tb3+/M3+ (M = Y, Gd, La) taken for the synthesis for Tb3+ content within 1 at.% accuracy. X-ray powder diffraction (XRD) measurements were performed with a D2 Phaser (Bruker, Billerica, MA, USA) X-ray diffractometer using Cu Kα radiation (λ = 1.54056 Å). SEM images were obtained using a scanning electron microscope Zeiss Merlin. Thermogravimetry curves were obtained using a TG 209 F1 Libra thermo-microbalance (Netzsch, Hanau, Germany). The measurement of FTIR spectra was carried out using the IRAffinity-1 spectrometer (Shimadzu, Kyoto, Japan). To carry out photoluminescence studies, the synthesized samples (20 mg) and potassium bromide (300 mg) were pressed into pellets (diameter 13 mm). The photoluminescence data were obtained with a Fluoromax-4 fluorescence spectrometer (Horiba Jobin Yvon, Kyoto, Japan) in perpendicular geometry. Lifetime measurements were performed with the same spectrometer using a pulsed Xe lamp (pulse duration: 3 µs) in a timescale of 50 µs–10 ms. The absolute values of the photoluminescence quantum yields were recorded using a Fluorolog-3 Quantaphi-2 (Horiba Scientific, Kyoto, Japan) device using an integration sphere. All measurements were performed at 25 °C.

3. Results

3.1. Structure and Morphology

The powder X-ray diffraction (PXRD) patterns of the synthesized compounds (TbxM1−x)2(1,4-bdc)3·nH2O (M = Y, La, Gd) are shown in Figure 1a (main text) and Figure S1 (Supplementary Materials). The analysis of XRD patterns demonstrates that all synthesized compounds possess the Ln2(1,4-bdc)3·4H2O crystalline phase (Ln = Ce–Yb) [35]. In this structure, the lanthanide ions have coordination number six and are connected to oxygen atoms of two water molecules and six different terephthalate ions. The polyhedron of these oxygen atoms forms a distorted square antiprism around a metal ion.
The unit cell parameters of synthesized compounds were refined, and the unit cell volumes were calculated at different Tb3+ concentrations from 0 to 100 at.%. Unit cell parameters of the samples were refined using the Pawley method from the PXRD data (Table S1, Supplementary Materials) [36]. The unit cell volumes were calculated from unit cell parameters. We have found that Vegard’s law is obeyed in the studied systems because unit cell volumes linearly depend on the Tb3+ content (Figure 1b) [37]. Therefore, the (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, La, Gd) terephthalates can be considered as solid solutions in a whole concentration range. For the (TbxLa1−x)2(1,4-bdc)3‧4H2O, the increase in La3+ content results in the unit cell volume elevation due to a larger ionic radius of La3+ ions (1.160 Å, the coordination number is eight) than the ionic radius of Tb3+ ions (1.040 Å) [38]. The ionic radius of the Gd3+ (1.053 Å) and Tb3+ ions are close to each other, which leads to close values of unit cell parameters among (TbxGd1−x)2(1,4-bdc)3‧4H2O series. In the (TbxM1−x)2(1,4-bdc)3‧4H2O series, the substitution of larger Tb3+ by smaller Y3+ (0.977 Å) ions results in a decrease in unit cell volume.
The particle morphology and the porosity of the selected synthesized materials such as (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Gd, La, Y) were revealed using scanning electron microscopy (SEM). The pore and nanoparticle sizes were estimated from the SEM images. SmartTiffV2 software (V02.00) allows for distance estimations on .tif images obtained as scanning electron microscopy output files on the instrument. The SEM images (Figure 2) clearly demonstrate that the resulting compounds consist of large particles sized between 5 and 20 µm. The obtained material has a porous structure with pore size of 10–200 nm. One can observe that large particles consist of aggregated spindle-shaped or filiform nanoparticles.

3.2. Vibrational Spectroscopy

The IR spectra of the selected homometallic M2(1,4-bdc)3·4H2O (M = Y, Gd, La, Tb) and heterometallic (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Y, Gd, La) terephthalates (Figure 3) were measured in order to follow the doping effect on the vibrational structure of the ligand. The broad band peaking at about 3500 cm−1 corresponds to the O–H stretching vibrations of lanthanide-coordinated water molecules. The 1270–1470 and 1470–1800 cm−1 narrow bands correspond to the C–O symmetric and asymmetric stretching vibrations of the carboxyl group in the terephthalate ion, respectively. The results obtained are consistent with the literature data on rare earth terephthalates [39,40]. All of the studied compounds have almost identical IR spectra that agree with PXRD data, which demonstrates that all of the synthesized compounds have the same crystalline phase, namely Ln2(1,4-bdc)3‧4H2O.

3.3. Thermogravimetric Analysis

Thermogravimetric analysis (TGA) curves measured in the temperature range of 35–200 °C the selected homometallic M2(1,4-bdc)3·4H2O (M = Y, Gd, La, Tb) and heterometallic (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Y, Gd, La) terephthalates are shown in Figure 4. For all of the studied samples, a weight loss of 8.0–9.3% was recorded ranging between 100 °C and 160 °C. As indicated earlier [41], the weight loss at such temperatures corresponds to the dehydration process of the compounds according to the following equation:
M2(1,4-bdc)3·4H2O = M2(1,4-bdc)3 + 4H2O or
(Tb0.5M0.5)2(1,4-bdc)3·4H2O = (Tb0.5M0.5)2(1,4-bdc)3 + 4H2O
The mass loss of 8.0–9.3% corresponds to the elimination of 3.8–4.2 water molecules from the initial terephthalates. These data are consistent with the results of the PXRD, which showed that all of the studied materials crystallize in the Ln2(1,4-bdc)3 4H2O phase. The temperature of the dehydration (Tdeh.) of M2(1,4-bdc)3·4H2O (M = Y, Gd, La, Tb) and (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Y, Gd, La) is presented in Table 1. As we can see, Tdeh. increases with increases in the ionic radius and, respectively, the unit cell of the compounds. We also observe that the dehydration temperatures of heterometallic terephthalates are in the range between the temperatures of monometallic terephthalates. A correlation exists between the dehydration temperatures and the unit cell volume of the samples. As the unit cell volume decreases, the free volume available for the four water molecules also decreases or disappears. Considering the volume of a single water molecule to be approximately 6 Å3 (24 Å3 for four molecules), we observe a volume change of about 39 Å3 when moving from lanthanum to yttrium, exceeding the volume required by the water molecules. This suggests that the surrounding molecules exert additional pressure on the water molecules. Under this pressure, water molecules are more likely to leave the system, resulting in a lower dehydration temperature for materials with smaller unit cell volumes compared to those with larger unit cell volumes.

3.4. Luminescent Properties

The emission spectra of the synthesized compounds are shown in Figure 5 (main text) and Figure S2 (Supplementary Materials). All emission spectra exhibit similar bands corresponding to the 5D4–7FJ (J = 3–6) f-f transitions of the Tb3+ ion: 5D4–7F3 (623 nm), 5D4–7F4 (584 nm), 5D4–7F5 (546 nm), and 5D4–7F6 (487 nm). The presence of characteristic Tb3+ bands in the emission spectra upon 320 nm excitation into the absorption band of terephthalate ion indicates the presence of an antenna effect. The initially populated singlet Sn state of the terephthalate ion undergoes a rapid internal conversion to the lowest-energy singlet S1 state. The S1 state effectively relaxes into the triplet T1 state by intersystem crossing due to the presence of heavy lanthanide ion (heavy atom effect). The T1 state of the terephthalate ion the 5D4 energy level of the Tb3+ ion have close energies, resulting in an efficient energy transfer from the electronically excited terephthalate ion to the 5D4 level of the Tb3+ ion [32,42]. The 5D4 level Tb3+ ion then undergoes radiative transition to the underlying 7FJ energy levels (J = 6, 5, 4, 3), which correspond to the narrow bands in the emission spectra of the studied compounds.
It is well known that the fine structure of the band splitting in the luminescence spectrum depends strongly on the local symmetry group of the luminescent lanthanide (III) ion. Thus, for europium ions, Binnemans reviews in detail the effect of local symmetry on the fine structure of the spectra [43]. The study of the symmetry of Tb3+ ions is conveniently interpreted through the study of the local symmetry of Eu3+ ions, the spectra of which contain convenient markers of the band structure [43], allowing us to draw a conclusion about the symmetry group. Due to the close ionic radii, equality of charges, and close electron shells in the structure, we can say that when europium (III) ions are replaced by terbium (III) ions, there is no change in the local symmetry. As we have already shown, terephthalates are solid solutions where Vegard’s law is fulfilled, and the isostructural substitution of some lanthanide ions for others leads only to a monotonic change in the unit cell parameters. Our previous studies have shown that Eu2(1,4-bdc)3‧4H2O exhibits a 5D0-7F0 transition [31], which, according to the Judd–Ofelt theory, is hidden and occurs only for coordination sites with Cn, Cnv, and Cs symmetry [41,43]. In the work by Daiguebonne et al., the authors report that lanthanide (III) ions had pseudo-C4 symmetry in Ln2(1,4-bdc3‧4H2O (Ln = Tb, Eu) [41]. Therefore, we propose that a similar fine structure of emission bands indicates the identical pseudo-C4 symmetry of metal ions in all of the studied materials, namely (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Y, La, Gd).
The fine structure of the emission spectra for the Y-, Gd-, and La-doped terephthalates is identical to that of the emission spectrum of unsubstituted terbium terephthalate, implying the same coordination environment of Tb3+ in the studied heterometallic compounds. This conclusion is in agreement with the PXRD data, which demonstrate isomorphic substitution of terbium by yttrium, gadolinium, and lanthanum ions among the studied series, (TbxM1−x)2(1,4-bdc)3‧4H2O (M = Y, La, Gd). However, the concentration dependence of the integrated intensity of emission spectra (Table 2, main text, and Figure S3, Supplementary Materials) is non-monotonous as a result of non-monotonous photoluminescence quantum yield (PLQY) concentration dependence (Table 3). The photoluminescence decay curves of the (TbxM1−x)2(1,4-bdc)3‧4H2O phosphors monitored at 546 nm (5D4–7F5 transition) are presented in Figure 6 (λex. = 320 nm). The photoluminescence decay curves were fitted by single exponential functions:
I ( t ) = I 0 · e − t τ   ,
where τ is the observed 5D4 lifetime. We have found that the lifetime of the 5D4 excited state decreases from 1.1 to 0.7 ms as the Tb3+ concentration increases (Table 3), which is consistent with our previous studies of Tb–Lu [28]. Lifetime depression is associated with the higher probability of energy transfer between close-located Tb3+ ions, as well as with the quenching of impurities at higher terbium content. The PLQYs of these compounds had maxima at about 50 at.% of Tb3+, where the average PLQY is 63% (Table 2). The emission intensity and PLQY of REE-containing phosphors non-monotonously depend on the Tb3+ content, which is caused by the two competitive effects [44,45,46,47]. The number of luminescent sites increases as the Tb3+ content rises, which results in radiative emission probability elevation and, as a result, rises in emission intensity and PLQY. At the same time, the growth in Tb3+ concentration results in the distance shortage between the Tb3+ ions, leading to emission quenching [28]. As a result of this effect, the PLQY values of pure terbium terephthalate (100 at.% of Tb3+) are lower than that of the MOFs, containing 50 at.% of Tb3+.

4. Conclusions

In the current study, the structure and luminescent properties of heterometallic terbium-based terephthalate “antenna” MOFs, namely (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Gd, La, Y; x = 0.001–1), were studied in detail in a wide concentration range. The particle morphology, thermal stability, and vibrational structure of the selected homo- and bi-metallic materials are reported as well. All of the compounds studied are isomorphic to each other and correspond to the crystal structure of Ln2(1,4-bdc)3·4H2O (Ln = Ce–Yb) [35]. The unit cell parameters of the synthesized compounds were refined using the Pawley method. The unit cell volumes linearly depend on the Tb3+ concentration. The substitution of Tb3+ ions with La3+ ions, which have a larger radius, leads to an increase in the unit cell parameters in the compounds (TbxLa1−x)2(1,4-bdc)3 4H2O, whereas replacement of Tb3+ with Y3+ ions with smaller radii leads to a decrease in the unit cell volumes in the series (TbxM1−x)2(1,4-bdc)3 4H2O; for compounds of the series (TbxGd1−x)2(1,4-bdc)3 4H2O, the unit cell parameters remain virtually unchanged in the series due to the close values and radii of Tb3+ and Gd3+. Thus, Vegard’s law is obeyed [37], indicating that the synthesized compounds are solid solutions in a whole concentration range. Using Scanning Electron Microscopy, we revealed that synthesized compounds consist of large particles with an average size of between 5 and 20 µm. The obtained materials have a porous structure (10–200 nm pore size) and consist of aggregated nanoparticles. The IR spectra contains the characteristic bands of the lanthanide-coordinated water molecules and the carboxyl group in the terephthalate ions. The almost identical shape of the IR spectra indicates the similar structure of the synthesized terephthalates. All of the compounds are thermally stable up to 120 °C. Further heating results in dehydration of the compounds, resulting in the formation of anhydrous terephthalates. All of the reported MOFs demonstrate the antenna effect. Their emission spectra consist of narrow bands corresponding to 5D4–7FJ (J = 3–6) transitions in the Tb3+ ion upon 320 nm excitation into a singlet-excited state of the terephthalate ion. The fine structure of the emission spectra for the Tb–Gd, Tb–Y, and Tb–La compound series is identical to that of the unsubstituted Tb2(1,4-bdc)3∙4H2O emission spectra due to the same local symmetry of Tb3+. This is also confirmed by the identity of the crystalline phase in all of the compounds. Photoluminescence decay and PLQY mostly depend on the dopant concentration, but not on the type of doping ion. The 5D4 excited-state lifetime decreases from 1.1 to 0.7 ms as the Tb3+ concentration increases due to concentration quenching. Maximum PLQYs are observed for 50%-substituted solid solutions (TbM(1,4-bdc)3∙4H2O (M = Gd, La, Y); PLQY = 63, 66, and 60% for Gd, La, Y), exceeding the PLQY of unsubstituted terbium terephthalate (Tb2(1,4-bdc)3∙4H2O; PLQY = 46%). Therefore, we have demonstrated, contrary to previous work [24], that the 50% substitution of Tb3+ for Y3+, Gd3+, and La3+ ions results in a significant enhancement of the photoluminescence quantum yield, up to 1.6 times.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/cryst14110966/s1, Figure S1: The powder X-ray diffraction (PXRD) patterns of the synthesized compounds series: (a) (TbxGd1−x)2(1,4-bdc)3·nH2O (x = 0.001–1) including the Gd2(1,4-bdc)3·nH2O, (b) (TbxLa1−x)2(1,4-bdc)3·nH2O (x = 0.001–1) including the La2(1,4-bdc)3·nH2O, (c) (TbxY1−x)2(1,4-bdc)3·nH2O (x = 0.001–1) including the Y2(1,4-bdc)3·nH2O. The positions and relative intensities of diffraction maxima of Tb2(1,4-bdc)3·4H2O taken from ref. [34] are shown as bars, Figure S2: The normalized emission spectra of (a) (TbxGd1−x)2(1,4-bdc)3·4H2O, (b) (TbxY1−x)2(1,4-bdc)3·4H2O, (c) (TbxLa1−x)2(1,4-bdc)3·4H2O at a wide concentration range of Tb3+ (x = 0.001–1; given in legend) upon 320 nm excitation. The artefact maxima peaked at 615 nm (marked as *) correspond to the Eu3+ present as impurities in the gadolinium nitrate used for the synthesis, Figure S3: The superimposed emission spectra of (a) (TbxGd1−x)2(1,4-bdc)3·4H2O, (b) (TbxLa1−x)2(1,4-bdc)3·4H2O, and (c) (TbxY1−x)2(1.4-bdc)3·4H2O at a wide concentration range of Tb3+ (x = 0.001–1; given in legend) upon 320 nm excitation, Table S1: Unit cell parameters of the (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, La, Gd; x = 0.04–1). Table S2: Tb3+ atomic fractions (at.%) in the synthesized compounds, namely, (TbxM1−x)2(1,4-bdc)3·4H2O. Measured data were obtained from EDX.

Author Contributions

Conceptualization, A.S.M., A.S.P., and O.S.B.; methodology, A.S.M., Y.N.T., A.S.P., and O.S.B.; validation, M.N.R. and I.E.K.; formal analysis, A.S.M., A.S.P., and O.S.B.; investigation, A.S.M., A.S.P., S.N.O., and O.S.B.; resources, A.S.M., M.Y.S., and N.A.B.; data curation, A.S.M., A.S.P., and O.S.B.; writing—original draft preparation, A.S.M., N.A.B., A.S.P., and O.S.B.; writing—review and editing, M.Y.S., Y.N.T., I.E.K., N.A.B., A.S.P., O.S.B., and A.S.M.; visualization, A.S.M., A.S.P., and O.S.B.; supervision, A.S.M.; project administration, A.S.M.; funding acquisition, A.S.M. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Russian Science Foundation under grant No. 22-73-10040 (https://rscf.ru/en/project/22-73-10040/, accessed on 16 October 2024).

Data Availability Statement

The original contributions presented in the study are included in the article (and Supplementary Materials), further inquiries can be directed to the corresponding authors.

Acknowledgments

The measurements were performed in the Research Park of Saint Petersburg State University (Magnetic Resonance Research Centre, Chemical Analysis and Materials Research Centre, Cryogenic Department, Interdisciplinary Resource Centre for Nanotechnology, Centre for X-ray Diffraction Studies, Centre for Optical and Laser Materials Research, Thermogravimetric and Calorimetric Research Centre, and Centre for Innovative Technologies of Composite Nanomaterials). This article was published in commemoration of the 300th anniversary of Saint Petersburg State University’s founding.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Cui, Y.; Chen, B.; Qian, G. Lanthanide Metal–Organic Frameworks for Luminescent Sensing and Light-Emitting Applications. Coord. Chem. Rev. 2014, 273–274, 76–86. [Google Scholar] [CrossRef]
  2. Chen, B.; Wang, L.; Xiao, Y.; Fronczek, F.R.; Xue, M.; Cui, Y.; Qian, G. A Luminescent Metal–Organic Framework with Lewis Basic Pyridyl Sites for the Sensing of Metal Ions. Angew. Chem. Int. Ed. 2009, 48, 500–503. [Google Scholar] [CrossRef] [PubMed]
  3. Pellé, F.; Aschehoug, P.; Surblé, S.; Millange, F.; Serre, C.; Férey, G. Interactions between Eu3+ Ions in Inorganic-Organic Hybrid Materials. J. Solid State Chem. 2010, 183, 795–802. [Google Scholar] [CrossRef]
  4. Lee, J.; Farha, O.K.; Roberts, J.; Scheidt, K.A.; Nguyen, S.T.; Hupp, J.T. Metal–Organic Framework Materials as Catalysts. Chem. Soc. Rev. 2009, 38, 1450–1459. [Google Scholar] [CrossRef]
  5. Massi, M.; Ogden, M.I. Luminescent Lanthanoid Calixarene Complexes and Materials. Materials 2017, 10, 1369. [Google Scholar] [CrossRef]
  6. Liu, D.; Lu, K.; Poon, C.; Lin, W. Metal–Organic Frameworks as Sensory Materials and Imaging Agents. Inorg. Chem. 2014, 53, 1916–1924. [Google Scholar] [CrossRef]
  7. Zhou, X.; Wang, H.; Jiang, S.; Xiang, G.; Tang, X.; Luo, X.; Li, L.; Zhou, X. Multifunctional Luminescent Material Eu(III) and Tb(III) Complexes with Pyridine-3,5-Dicarboxylic Acid Linker: Crystal Structures, Tunable Emission, Energy Transfer, and Temperature Sensing. Inorg. Chem. 2019, 58, 3780–3788. [Google Scholar] [CrossRef]
  8. Shurygin, A.V.; Vovna, V.I.; Korochentsev, V.V.; Mirochnik, A.G.; Kalinovskaya, I.V.; Sergienko, V.I. Optical Properties and Electronic Structure of Eu(III) Complexes with HMPA and TPPO. Spectrochim. Acta Part A Mol. Biomol. Spectrosc. 2021, 250, 119397. [Google Scholar] [CrossRef]
  9. Khudoleeva, V.; Tcelykh, L.; Kovalenko, A.; Kalyakina, A.; Goloveshkin, A.; Lepnev, L.; Utochnikova, V. Terbium-Europium Fluorides Surface Modified with Benzoate and Terephthalate Anions for Temperature Sensing: Does Sensitivity Depend on the Ligand? J. Lumin. 2018, 201, 500–508. [Google Scholar] [CrossRef]
  10. Aslandukov, A.N.; Utochnikova, V.V.; Goriachiy, D.O.; Vashchenko, A.A.; Tsymbarenko, D.M.; Hoffmann, M.; Pietraszkiewicz, M.; Kuzmina, N.P. The Development of a New Approach toward Lanthanide-Based OLED Fabrication: New Host Materials for Tb-Based Emitters. Dalt. Trans. 2018, 47, 16350–16357. [Google Scholar] [CrossRef]
  11. Kozlov, M.I.; Aslandukov, A.N.; Vashchenko, A.A.; Medvedko, A.V.; Aleksandrov, A.E.; Grzibovskis, R.; Goloveshkin, A.S.; Lepnev, L.S.; Tameev, A.R.; Vembris, A.; et al. On the Development of a New Approach to the Design of Lanthanide-Based Materials for Solution-Processed OLEDs. Dalt. Trans. 2019, 48, 17298–17309. [Google Scholar] [CrossRef] [PubMed]
  12. Girotto, E.; Pereira, A.; Arantes, C.; Cremona, M.; Bortoluzzi, A.J.; Salla, C.A.M.; Bechtold, I.H.; Gallardo, H. Efficient Terbium Complex Based on a Novel Pyrazolone Derivative Ligand Used in Solution-Processed OLEDs. J. Lumin. 2019, 208, 57–62. [Google Scholar] [CrossRef]
  13. Sravani, V.V.; Gupta, S.K.; Sreenivasulu, B.; Gangopadhyay, P.; Rao, C.V.S.B.; Suresh, A.; Sivaraman, N. Bright Green Emitting Terbium-MOF with High Quantum Yield Achieved through Post Synthetic Modifications. Opt. Mater. 2022, 133, 112944. [Google Scholar] [CrossRef]
  14. Özgür, E.; Patra, H.K.; Turner, A.P.F.; Denizli, A.; Uzun, L. Lanthanide [Terbium(III)]-Doped Molecularly Imprinted Nanoarchitectures for the Fluorimetric Detection of Melatonin. Ind. Eng. Chem. Res. 2020, 59, 16068–16076. [Google Scholar] [CrossRef]
  15. Zhang, Z.; Zhang, L.; Han, P.; Liu, Q. A Luminescent Probe Based on Terbium-Based Metal–Organic Frameworks for Organophosphorus Pesticides Detection. Microchim. Acta 2022, 189, 438. [Google Scholar] [CrossRef]
  16. Yang, M.; Shi, J.; Luo, T.; Yang, X. Luminescence Detection of Cr3+, Bi3+, and Acetone in Aqueous Solution by Core-Shell Tb-MOF. Curr. Anal. Chem. 2025, 21, 57–67. [Google Scholar] [CrossRef]
  17. Wang, X.; Cong, Q.; Feng, C.; Sun, Z.; Cai, Z.; Fan, C.; Pei, L. Terbium Vanadate Nanowires-Based Electrochemical Sensors for Mercury Ions. Appl. Biochem. Biotechnol. 2024. [Google Scholar] [CrossRef]
  18. Yue, X.; Fu, L.; Li, Y.; Xu, S.; Lin, X.; Bai, Y. Lanthanide Bimetallic MOF-Based Fluorescent Sensor for Sensitive and Visual Detection of Sulfamerazine and Malachite. Food Chem. 2023, 410, 135390. [Google Scholar] [CrossRef]
  19. Yin, H.Q.; Wang, X.Y.; Yin, X.B. Rotation Restricted Emission and Antenna Effect in Single Metal–Organic Frameworks. J. Am. Chem. Soc. 2019, 141, 15166–15173. [Google Scholar] [CrossRef]
  20. Cao, W.; Tang, Y.; Cui, Y.; Qian, G. Energy Transfer in Metal–Organic Frameworks and Its Applications. Small Struct. 2020, 1, 2000019. [Google Scholar] [CrossRef]
  21. Alpha, B.; Ballardini, R.; Balzani, V.; Lehn, J.-M.; Perathoner, S.; Sabbatini, N. Antenna Effect in Luminescent Lanthanide Cryptates: A Photophysical Study. Photochem. Photobiol. 1990, 52, 299–306. [Google Scholar] [CrossRef]
  22. Kolesnik, S.S.; Nosov, V.G.; Kolesnikov, I.E.; Khairullina, E.M.; Tumkin, I.I.; Vidyakina, A.A.; Sysoeva, A.A.; Ryazantsev, M.N.; Panov, M.S.; Khripun, V.D.; et al. Ultrasound-Assisted Synthesis of Luminescent Micro-and Nanocrystalline Eu-Based Mofs as Luminescent Probes for Heavy Metal Ions. Nanomaterials 2021, 11, 2448. [Google Scholar] [CrossRef] [PubMed]
  23. Orlova, A.V.; Kozhevnikova, V.Y.; Lepnev, L.S.; Goloveshkin, A.S.; Le-Deigen, I.M.; Utochnikova, V.V. NIR Emitting Terephthalates (SmxDyyGd1−x-y)2(Tph)3(H2O)4 for Luminescence Thermometry in the Physiological Range. J. Rare Earths 2020, 38, 492–497. [Google Scholar] [CrossRef]
  24. Utochnikova, V.V.; Kuzmina, N.P. Photoluminescence of Lanthanide Aromatic Carboxylates. Russ. J. Coord. Chem. Khimiya 2016, 42, 679–694. [Google Scholar] [CrossRef]
  25. Wang, P.; Li, Z.F.; Song, L.P.; Wang, C.X.; Chen, Y. Catena-Poly[[[μ-Benzene-1,4-Dicarboxylato-Bis[Tetraaqualutetium(III)]] -Di-μ-Benzene-1,4-Dicarboxylato] Dihydrate]. Acta Crystallogr. Sect. E Struct. Rep. Online 2006, 62, 253–255. [Google Scholar] [CrossRef]
  26. Do Nascimento, J.F.S.; De Araújo, A.M.U.; Kulesza, J.; De Farias Monteiro, A.F.; Júnior, S.A.; Barros, B.S. Solid-State Tunable Photoluminescence in Gadolinium-Organic Frameworks: Effects of the Eu3+ Content and Co-Doping with Tb3+. New J. Chem. 2018, 42, 5514–5522. [Google Scholar] [CrossRef]
  27. Nosov, V.G.; Kupryakov, A.S.; Kolesnikov, I.E.; Vidyakina, A.A.; Tumkin, I.I.; Kolesnik, S.S.; Ryazantsev, M.N.; Bogachev, N.A.; Skripkin, M.Y.; Mereshchenko, A.S. Heterometallic Europium(III)–Lutetium(III) Terephthalates as Bright Luminescent Antenna MOFs. Molecules 2022, 27, 5763. [Google Scholar] [CrossRef]
  28. Nosov, V.G.; Toikka, Y.N.; Petrova, A.S.; Butorlin, O.S.; Kolesnikov, I.E.; Orlov, S.N.; Ryazantsev, M.N.; Kolesnik, S.S.; Bogachev, N.A.; Skripkin, M.Y.; et al. Brightly Luminescent (TbxLu1−x)2bdc3·nH2O MOFs: Effect of Synthesis Conditions on Structure and Luminescent Properties. Molecules 2023, 28, 2378. [Google Scholar] [CrossRef]
  29. Kolesnik, S.S.; Bogachev, N.A.; Kolesnikov, I.E.; Orlov, S.N.; Ryazantsev, M.N.; González, G.; Skripkin, M.Y.; Mereshchenko, A.S. Microcrystalline Luminescent (Eu1−xLnx)2bdc3·nH2O (Ln = La, Gd, Lu) Antenna MOFs: Effect of Dopant Content on Structure, Particle Morphology, and Luminescent Properties. Molecules 2024, 29, 532. [Google Scholar] [CrossRef]
  30. Toikka, Y.N.; Badikov, A.R.; Bogachev, N.A.; Kolesnikov, I.E.; Skripkin, M.Y.; Orlov, S.N.; Mereshchenko, A.S. Luminescent Properties and Thermal Stability of (Lu0.98Eu0.02)2bdc3·10H2O Metal–Organic Frameworks. Mendeleev Commun. 2024, 34, 634–636. [Google Scholar] [CrossRef]
  31. Butorlin, O.S.; Petrova, A.S.; Toikka, Y.N.; Kolesnikov, I.E.; Orlov, S.N.; Ryazantsev, M.N.; Bogachev, N.A.; Skripkin, M.Y.; Mereshchenko, A.S. The Structure and Optical Properties of Luminescent Europium Terephthalate Antenna Metal–Organic Frameworks Doped by Yttrium, Gadolinium, and Lanthanum Ions. Molecules 2024, 29, 3558. [Google Scholar] [CrossRef] [PubMed]
  32. Utochnikova, V.V.; Grishko, A.Y.; Koshelev, D.S.; Averin, A.A.; Lepnev, L.S.; Kuzmina, N.P. Lanthanide Heterometallic Terephthalates: Concentration Quenching and the Principles of the “Multiphotonic Emission”. Opt. Mater. 2017, 74, 201–208. [Google Scholar] [CrossRef]
  33. Alammar, T.; Hlova, I.Z.; Gupta, S.; Biswas, A.; Ma, T.; Zhou, L.; Balema, V.; Pecharsky, V.K.; Mudring, A.V. Mechanochemical Synthesis, Luminescent and Magnetic Properties of Lanthanide Benzene-1,4-Dicarboxylate Coordination Polymers (Ln0.5Gd0.5)2 (1,4-BDC)3(H2O)4; Ln = Sm, Eu, Tb. New J. Chem. 2020, 44, 1054–1062. [Google Scholar] [CrossRef]
  34. Haquin, V.; Etienne, M.; Daiguebonne, C.; Freslon, S.; Calvez, G.; Bernot, K.; Le Pollès, L.; Ashbrook, S.E.; Mitchell, M.R.; Bünzli, J.C.; et al. Color and Brightness Tuning in Heteronuclear Lanthanide Terephthalate Coordination Polymers. Eur. J. Inorg. Chem. 2013, 2013, 3464–3476. [Google Scholar] [CrossRef]
  35. Reineke, T.M.; Eddaoudi, M.; Fehr, M.; Kelley, D.; Yaghi, O.M. From Condensed Lanthanide Coordination Solids to Microporous Frameworks Having Accessible Metal Sites. J. Am. Chem. Soc. 1999, 121, 1651–1657. [Google Scholar] [CrossRef]
  36. Pawley, G.S. Unit-cell refinement from powder diffraction scans. J. Appl. Crystallogr. 1981, 14, 357–361. [Google Scholar] [CrossRef]
  37. Denton, A.R.; Ashcroft, N.W. Vegard’s Law. Phys. Rev. A 1991, 43, 3161–3164. [Google Scholar] [CrossRef]
  38. Shannon, R.D. Revised Effective Ionic Radii and Systematic Studies of Interatomic Distances in Halides and Chalcogenides. Acta Crystallogr. 1976, A32, 751–767. [Google Scholar] [CrossRef]
  39. Costa, B.A.; Nunes, W.D.G.; Bembo, L.H.; Siqueira, A.B.; Caires, F.; Leles, M.I.G.; Ionashiro, E.Y. Study of Thermoanalytical Behavior of Heavier Lanthanides Terephthalates in Air Atmosphere. J. Therm. Anal. Calorim. 2018, 134, 1205–1210. [Google Scholar] [CrossRef]
  40. Nunes, W.D.G.; Teixeira, J.A.; do Nascimento, A.L.C.S.; Caires, F.J.; Ionashiro, E.Y.; Ionashiro, M. A Comparative Study on Thermal Behavior of Solid-State Light Trivalent Lanthanide Isonicotinates in Dynamic Dry Air and Nitrogen Atmospheres. J. Therm. Anal. Calorim. 2016, 125, 397–405. [Google Scholar] [CrossRef]
  41. Daiguebonne, C.; Kerbellec, N.; Guillou, O.; Bünzli, J.C.; Gumy, F.; Catala, L.; Mallah, T.; Audebrand, N.; Gérault, Y.; Bernot, K.; et al. Structural and Luminescent Properties of Micro- and Nanosized Particles of Lanthanide Terephthalate Coordination Polymers. Inorg. Chem. 2008, 47, 3700–3708. [Google Scholar] [CrossRef]
  42. Latva, M.; Takalob, H.; Mukkala, V.M.; Matachescu, C.; Rodríguez-Ubis, J.C.; Kankare, J. Correlation between the Lowest Triplet State Energy Level of the Ligand and Lanthanide(III) Luminescence Quantum Yield. J. Lumin. 1997, 75, 149–169. [Google Scholar] [CrossRef]
  43. Binnemans, K. Interpretation of Europium(III) Spectra. Coord. Chem. Rev. 2015, 295, 1–45. [Google Scholar] [CrossRef]
  44. Holsa, J.; Leskela, M.; Niinisto, L. Concentration quenching of Tb3+ luminescence in laobr and Gd202S phosphors. Mat. Res. Bull. 1979, 14, 1403–1409. [Google Scholar] [CrossRef]
  45. Zhang, W.; Kou, H.; Ge, L.; Zhang, Y.; Lin, L.; Li, W. Effects of Doping Ions on the Luminescence Performance of Terbium Doped Gadolinium Polysulfide Phosphor. J. Phys. Conf. Ser. 2020, 1549, 032064. [Google Scholar] [CrossRef]
  46. Kolesnikov, I.E.; Mamonova, D.V.; Lähderanta, E.; Kurochkin, A.V.; Mikhailov, M.D. The Impact of Doping Concentration on Structure and Photoluminescence of Lu2O3:Eu3+ Nanocrystals. J. Lumin. 2017, 187, 26–32. [Google Scholar] [CrossRef]
  47. Kolesnikov, I.E.; Kalinichev, A.A.; Kurochkin, M.A.; Golyeva, E.V.; Terentyeva, A.S.; Kolesnikov, E.Y.; Lähderanta, E. Structural, Luminescence and Thermometric Properties of Nanocrystalline YVO4:Dy3+ Temperature and Concentration Series. Sci. Rep. 2019, 9, 2043. [Google Scholar] [CrossRef]
Crystals 14 00966 g001
Figure 1. The PXRD patterns of selected (TbxM1−x)2(1,4-bdc)3‧4H2O (M = Y, La, Gd; x = 0, 0.01, 0.1, 1) and the simulated XRD pattern of Tb2(1,4-bdc)3‧4H2O single-crystal structure were taken from ref. [35] (a) and unit cell volume (Vu.c.) concentration dependence refined for (TbxM1−x)2(1,4-bdc)3·4H2O (M = Gd, La, Y) (b).
Figure 1. The PXRD patterns of selected (TbxM1−x)2(1,4-bdc)3‧4H2O (M = Y, La, Gd; x = 0, 0.01, 0.1, 1) and the simulated XRD pattern of Tb2(1,4-bdc)3‧4H2O single-crystal structure were taken from ref. [35] (a) and unit cell volume (Vu.c.) concentration dependence refined for (TbxM1−x)2(1,4-bdc)3·4H2O (M = Gd, La, Y) (b).
Crystals 14 00966 g001
Crystals 14 00966 g002
Figure 2. SEM images of (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Gd, La, Y).
Figure 2. SEM images of (Tb0.5M0.5)2(1,4-bdc)3·4H2O (M = Gd, La, Y).
Crystals 14 00966 g002
Crystals 14 00966 g003
Figure 3. IR spectra of (Tb0.5M0.5)2(1,4-bdc)3‧4H2O and M2(1,4-bdc)3‧4H2O (M = Y, Gd, La, Tb).
Figure 3. IR spectra of (Tb0.5M0.5)2(1,4-bdc)3‧4H2O and M2(1,4-bdc)3‧4H2O (M = Y, Gd, La, Tb).
Crystals 14 00966 g003
Crystals 14 00966 g004
Figure 4. TGA curves of selected heterometallic (Tb0.5M0.5)2(1,4-bdc)3‧4H2O (M = Gd, La, Y) and homometallic M2(1,4-bdc)3‧4H2O (M = Tb, Gd, La, Y) terephthalates measured in the temperature range of 35–200 °C.
Figure 4. TGA curves of selected heterometallic (Tb0.5M0.5)2(1,4-bdc)3‧4H2O (M = Gd, La, Y) and homometallic M2(1,4-bdc)3‧4H2O (M = Tb, Gd, La, Y) terephthalates measured in the temperature range of 35–200 °C.
Crystals 14 00966 g004
Crystals 14 00966 g005
Figure 5. The normalized emission spectra of (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Y, La, Gd) at the selected Tb3+ concentrations (given in legend) upon 320 nm excitation. The artefact maxima peaking at 615 nm (marked as *) correspond to the Eu3+ present as impurities in the gadolinium nitrate used for the synthesis.
Figure 5. The normalized emission spectra of (TbxM1−x)2(1,4-bdc)3∙4H2O (M = Y, La, Gd) at the selected Tb3+ concentrations (given in legend) upon 320 nm excitation. The artefact maxima peaking at 615 nm (marked as *) correspond to the Eu3+ present as impurities in the gadolinium nitrate used for the synthesis.
Crystals 14 00966 g005
Crystals 14 00966 g006
Figure 6. The photoluminescence decay curves of (a) (TbxGd1−x)2(1.4-bdc)3‧4H2O, (b) (TbxY1−x)2(1.4-bdc)3‧4H2O, and (c) (TbxLa1−x)2(1.4-bdc)3‧4H2O at the selected concentrations of Tb3+ (x = 0.001, 0.01, 0.1, 0.5, 0.9, 1; given in legend) upon 320 nm excitation. Y-axis is logarithmic normalized intensity of luminescence.
Figure 6. The photoluminescence decay curves of (a) (TbxGd1−x)2(1.4-bdc)3‧4H2O, (b) (TbxY1−x)2(1.4-bdc)3‧4H2O, and (c) (TbxLa1−x)2(1.4-bdc)3‧4H2O at the selected concentrations of Tb3+ (x = 0.001, 0.01, 0.1, 0.5, 0.9, 1; given in legend) upon 320 nm excitation. Y-axis is logarithmic normalized intensity of luminescence.
Crystals 14 00966 g006
Table 1. Temperatures of the dehydration for selected heterometallic (Tb0.5M0.5)2(1,4-bdc)3‧4H2O (M = Gd, La, Y) and homometallic M2(1,4-bdc)3‧4H2O (M = Tb, Gd, La, Y) terephthalates.
Table 1. Temperatures of the dehydration for selected heterometallic (Tb0.5M0.5)2(1,4-bdc)3‧4H2O (M = Gd, La, Y) and homometallic M2(1,4-bdc)3‧4H2O (M = Tb, Gd, La, Y) terephthalates.
CompoundTdeh., °C
Y2(1,4-bdc)3·4H2O104.8
Tb2(1,4-bdc)3·4H2O120.1
Gd2(1,4-bdc)3·4H2O142.5
La2(1,4-bdc)3·4H2O158.9
TbY(1,4-bdc)3·4H2O108.3
TbGd(1,4-bdc)3·4H2O126.3
TbLa(1,4-bdc)3·4H2O132.6
Table 2. The value of the integrated intensity (S) of the luminescence spectra of (TbxM1−x)2(1,4-bdc)3‧4H2O (M = Y, La, Gd).
Table 2. The value of the integrated intensity (S) of the luminescence spectra of (TbxM1−x)2(1,4-bdc)3‧4H2O (M = Y, La, Gd).
χ(Tb3+), at.%S × 107, a.u.
M = GdM = LaM = Y
0.13.994.012.50
0.24.693.324.16
0.49.166.176.84
0.610.029.468.51
0.89.8710.921.01
115.2610.067.96
213.2615.9715.56
410.4022.5835.00
642.0224.2143.95
858.7930.0044.57
1036.8731.4064.56
2056.6233.1046.84
3032.0522.6452.51
4050.3320.8743.18
5069.9131.3147.53
6050.3838.7842.33
7057.4938.9642.80
8060.4538.2948.83
9035.2327.2234.12
10038.1823.5236.10
Table 3. The observed 5D4 lifetime and PLQYs of (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, La, Gd).
Table 3. The observed 5D4 lifetime and PLQYs of (TbxM1−x)2(1,4-bdc)3·4H2O (M = Y, La, Gd).
Compoundχ(Tb3+), at.%τ, msPLQY, %
Tb2(1,4-bdc)3·4H2O1000.68 ± 0.0146 ± 1
(TbxY1−x)2(1,4-bdc)3·4H2O11.10 ± 0.0127 ± 1
101.01 ± 0.0157 ± 1
500.93 ± 0.0160 ± 1
900.74 ± 0.0148 ± 1
(TbxLa1−x)2(1,4-bdc)3·4H2O11.02 ± 0.0124 ± 1
100.99 ± 0.0155 ± 1
500.95 ± 0.0166 ± 1
900.78 ± 0.0249 ± 1
(TbxGd1−x)2(1,4-bdc)3·4H2O11.05 ± 0.0123 ± 1
101.00 ± 0.0147 ± 1
500.93 ± 0.0163 ± 1
900.75 ± 0.0152 ± 1
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Petrova, A.S.; Butorlin, O.S.; Toikka, Y.N.; Kolesnikov, I.E.; Orlov, S.N.; Ryazantsev, M.N.; Bogachev, N.A.; Skripkin, M.Y.; Mereshchenko, A.S. The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions. Crystals 2024, 14, 966. https://doi.org/10.3390/cryst14110966

AMA Style

Petrova AS, Butorlin OS, Toikka YN, Kolesnikov IE, Orlov SN, Ryazantsev MN, Bogachev NA, Skripkin MY, Mereshchenko AS. The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions. Crystals. 2024; 14(11):966. https://doi.org/10.3390/cryst14110966

Chicago/Turabian Style

Petrova, Anna S., Oleg S. Butorlin, Yulia N. Toikka, Ilya E. Kolesnikov, Sergey N. Orlov, Mikhail N. Ryazantsev, Nikita A. Bogachev, Mikhail Yu. Skripkin, and Andrey S. Mereshchenko. 2024. "The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions" Crystals 14, no. 11: 966. https://doi.org/10.3390/cryst14110966

APA Style

Petrova, A. S., Butorlin, O. S., Toikka, Y. N., Kolesnikov, I. E., Orlov, S. N., Ryazantsev, M. N., Bogachev, N. A., Skripkin, M. Y., & Mereshchenko, A. S. (2024). The Structure and Optical Properties of Luminescent Terbium Terephthalate Metal–Organic Frameworks Doped with Yttrium, Gadolinium, and Lanthanum Ions. Crystals, 14(11), 966. https://doi.org/10.3390/cryst14110966

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop