Abstract:We report the synthesis, characterization, photophysical investigations, and cell‐uptake studies of luminescent silica nanoparticles incorporating covalently linked visible‐light‐excitable Eu3+ complexes. Visible‐light excitation was accomplished by using highly conjugated carbazole‐based β‐diketonate ligands. Covalent incorporation of the Eu3+ complexes into the silica nanoparticles was achieved by modification of the bidentate phosphine oxide 4,6‐bis(diphenylphosphoryl)‐10H‐phenoxazine (DPOXPO), which was us… Show more
“…The development of efficient visible‐light‐excitable Eu 3+ complexes (absolute emission quantum yield Q Ln L > 0.40) has been a big challenge . These complexes are good candidates for less‐harmful biomarkers and can be used in optoelectronic applications as low‐voltage driven emitting species . Even though high Q Ln L values (> 0.80) are widely reported for the UV‐excitable Eu 3+ complexes, reports quantifying the emission quantum yield of visible‐light‐excitable Eu 3+ ‐based complexes are scarce , .…”
Visible-light-excited Eu 3+ complexes have received much attention in the last years due to the rapidly increasing demand for less-harmful biomarkers and low-voltage driven emitters in optoelectronics. Nevertheless, these complexes usually exhibit poor emission quantum yields, contrarily to the ones excited in the ultraviolet spectral region. To address this challenge, a series of complexes based on trivalent lanthanide ions, [Eu(bpyO2)(2), Gd (5)} and Ln(tta) 3 (bpyO2) {Ln = Eu (3), Gd (6)}, were synthesized using 2-thenoyltrifluoroacetone (Htta) as primary ligand and 2,2′-dipyridyl N,N′-dioxide (bpyO2) as neutral donor, and characterized, with special emphasis on their crystal struc-[a] Phantom-g, CICECO -was achieved through chemical modifications of the ligand structure with an expanded π-conjugated system [40] and using either neutral tris-(Q Ln L = 0.75 at 415 nm [49] and 0.40 at 400 nm [46] ) or anionic tetrakis-Eu 3+ --diketonates (Q Ln L = 0.80 at 410 nm [40] and Q Ln L = 0.45 at 400 nm [48] ).In this work, we followed a rational design to synthesize three Eu 3+ --diketonate complexes, 1, 2 and 3, using 2-thenoyltrifluoroacetone (Htta) and 2,2′-dipyridyl N,N′-dioxide (bpyO2) as the primary and ancillary ligands, respectively. The excitation window of 3 unprecedently extends into the visible region (up to 480 nm), well-above what was reported previously for analogous visible-light-excitable Eu 3+ -based complexes (up to 440-450 nm). [40,46,48] Detailed theoretical calculations performed with both time-dependent density functional theory (TD-DFT) and LUMPAC software [51] are also presented showing an excellent accord with the experimental intensity parameters, radiative and non-radiative decay rates, and intrinsic and absolute emission quantum yields. Moreover, 3 displayed excellent colour purity, with Commission Internationale d'Éclairage (CIE) chromaticity coordinates (0.66, 0.33), and was successfully employed for the fabrication of organic light-emitting diodes (OLEDs).
Results and DiscussionScheme 1 summarizes the adopted synthesis procedure. Complexes 1-3 were characterized using ATR/FT-IR spectroscopy, mass spectrometry, and elemental analyses. In the FT-IR spectra, the stretching and bending vibrations of N-O group of bpyO2 ligand are observed in 1 (1260, 853 and 837 cm -1 ) and 3 (1255, 856 and 836 cm -1 ) ( Figure S1). The carbonyl stretching frequency of Htta has been shifted from 1645 cm -1 to 1600 and 1, 2, 3, 4, and 6 were analysed by singlecrystal XRD. The most relevant structural features of 1-3 are depicted in Figure 1 and those of 4 and 6 are given in Figure S3 and S4, respectively. Selected bond lengths and bond angles Eur.
Single-Crystal X-ray Structures
Suitable crystals of
“…The development of efficient visible‐light‐excitable Eu 3+ complexes (absolute emission quantum yield Q Ln L > 0.40) has been a big challenge . These complexes are good candidates for less‐harmful biomarkers and can be used in optoelectronic applications as low‐voltage driven emitting species . Even though high Q Ln L values (> 0.80) are widely reported for the UV‐excitable Eu 3+ complexes, reports quantifying the emission quantum yield of visible‐light‐excitable Eu 3+ ‐based complexes are scarce , .…”
Visible-light-excited Eu 3+ complexes have received much attention in the last years due to the rapidly increasing demand for less-harmful biomarkers and low-voltage driven emitters in optoelectronics. Nevertheless, these complexes usually exhibit poor emission quantum yields, contrarily to the ones excited in the ultraviolet spectral region. To address this challenge, a series of complexes based on trivalent lanthanide ions, [Eu(bpyO2)(2), Gd (5)} and Ln(tta) 3 (bpyO2) {Ln = Eu (3), Gd (6)}, were synthesized using 2-thenoyltrifluoroacetone (Htta) as primary ligand and 2,2′-dipyridyl N,N′-dioxide (bpyO2) as neutral donor, and characterized, with special emphasis on their crystal struc-[a] Phantom-g, CICECO -was achieved through chemical modifications of the ligand structure with an expanded π-conjugated system [40] and using either neutral tris-(Q Ln L = 0.75 at 415 nm [49] and 0.40 at 400 nm [46] ) or anionic tetrakis-Eu 3+ --diketonates (Q Ln L = 0.80 at 410 nm [40] and Q Ln L = 0.45 at 400 nm [48] ).In this work, we followed a rational design to synthesize three Eu 3+ --diketonate complexes, 1, 2 and 3, using 2-thenoyltrifluoroacetone (Htta) and 2,2′-dipyridyl N,N′-dioxide (bpyO2) as the primary and ancillary ligands, respectively. The excitation window of 3 unprecedently extends into the visible region (up to 480 nm), well-above what was reported previously for analogous visible-light-excitable Eu 3+ -based complexes (up to 440-450 nm). [40,46,48] Detailed theoretical calculations performed with both time-dependent density functional theory (TD-DFT) and LUMPAC software [51] are also presented showing an excellent accord with the experimental intensity parameters, radiative and non-radiative decay rates, and intrinsic and absolute emission quantum yields. Moreover, 3 displayed excellent colour purity, with Commission Internationale d'Éclairage (CIE) chromaticity coordinates (0.66, 0.33), and was successfully employed for the fabrication of organic light-emitting diodes (OLEDs).
Results and DiscussionScheme 1 summarizes the adopted synthesis procedure. Complexes 1-3 were characterized using ATR/FT-IR spectroscopy, mass spectrometry, and elemental analyses. In the FT-IR spectra, the stretching and bending vibrations of N-O group of bpyO2 ligand are observed in 1 (1260, 853 and 837 cm -1 ) and 3 (1255, 856 and 836 cm -1 ) ( Figure S1). The carbonyl stretching frequency of Htta has been shifted from 1645 cm -1 to 1600 and 1, 2, 3, 4, and 6 were analysed by singlecrystal XRD. The most relevant structural features of 1-3 are depicted in Figure 1 and those of 4 and 6 are given in Figure S3 and S4, respectively. Selected bond lengths and bond angles Eur.
Single-Crystal X-ray Structures
Suitable crystals of
“…The low cell penetrability, low molar extinction coefficient, and absorption band in the deep UV region of the electromagnetic spectrum are however limiting factors for the use of NPs in luminescence imaging [91]. Those are circumvented by functionalizing its surface with cell receptors that facilitate cell recognition and uptake, and Ln III complexes, that improve the absorption and emission of light [92][93][94][95][96][97], respectively. For example, surface functionalization of hydroxyapatite NPs (HNPs) with [Eu(dbm) 3 (H 2 O) 2 ] complexes yielded a system with low cytotoxicity and capable of luminescence imaging HeLa cells [92][93][94].…”
Section: Cell Lines Abbreviations and Ligand Structuresmentioning
confidence: 99%
“…The use of nucleic acid-base aptamers is another strategy for improving the NPs cell uptake due to its low cost, strong interaction, and specificity towards cancer cells [98]. Bioconjugation of Ln III complexes, protected by a silica shell, with the aptamer Sgc8 using glutaraldehyde or succinic anhydride and EDAC/Sulfo-NHS resulted in a system that has a strong affinity for CCRF-CEM and Jurkat cells [96,97].…”
Section: Cell Lines Abbreviations and Ligand Structuresmentioning
The use of luminescence in biological systems allows one to diagnose diseases and understand cellular processes. Molecular systems, particularly lanthanide(III) complexes, have emerged as an attractive system for application in cellular luminescence imaging due to their long emission lifetimes, high brightness, possibility of controlling the spectroscopic properties at the molecular level, and tailoring of the ligand structure that adds sensing and therapeutic capabilities. This review aims to provide a background in luminescence imaging and lanthanide spectroscopy and discuss selected examples from the recent literature on lanthanide(III) luminescent complexes in cellular luminescence imaging, published in the period 2016–2020. Finally, the challenges and future directions that are pointing for the development of compounds that are capable of executing multiple functions and the use of light in regions where tissues and cells have low absorption will be discussed.
“…Nevertheless, low sensitization efficiency and quenching limit the applications of luminescent metals [59]. In order to improve their photostability and biocompatibility, Francis et al added a substituted silyl group into the ligands for the further modifications [30]. Eu@Si-OH nanoparticles were obtained after coating silyl group modified Eu complexes with silica via reverse microemulsion method.…”
Section: Classifications Of Lsnsmentioning
confidence: 99%
“…Eu@Si-NH 2 nanoparticles exhibited good performances in bioimaging.Fig. 4The curves of fluorescence intensity changing with exposure time under 365 nm irradiation, a parent Eu complex in CHCl 3 solution, b Eu@Si-NH 2 , and c Eu@Si-OH nanoparticles in phosphate-buffered saline (PBS) buffer solution [30]…”
Luminescent materials are of worldwide interest because of their unique optical properties. Silica, which is transparent to light, is an ideal matrix for luminescent materials. Luminescent silica nanoparticles (LSNs) have broad applications because of their enhanced chemical and thermal stability. Silica spheres of various sizes could be synthesized by different methods to satisfy specific requirements. Diverse luminescent dyes have potential for different applications. Subject to many factors such as quenchers, their performance was not quite satisfying. This review thus discusses the development of LSNs including their classification, synthesis, and application. It is the highlight that how silica improves the properties of luminescent dye and what role silica plays in the system. Further, their applications in biology, display, and sensors are also described.
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