Near-infrared Lanthanide Research Articles

Modulating Visible-Light Driven NIR Lanthanide Polymer Photocatalysis for Amplification Detection of Exosomal Proteins and Cancer Diagnosis.

Near-infrared (NIR) luminescent lanthanide materials hold great promise for bioanalysis, as they have anti-interference properties. The approach of efficient luminescence is sensitization through a reasonable chromophore to overcome the obstacle of the aqueous phase. The involvement of the surfactant motif is an innovative strategy to arrange the amphiphilic groups to be regularly distributed near the polymer to form a closed sensitized space. Herein, a lanthanide polymer (TCPP-PEI70K-FITC@Yb/SDBS) is designed in which the meso-tetra(4-carboxyphenyl)porphine (TCPP) ligand serves as both a sensitizer and photocatalytic switch. The surfactant sodium dodecyl benzenesulfonate (SDBS) wraps the photosensitive polymers to form a hydrophobic layer, which augments the light-harvesting ability and expedites its photocatalysis. TCPP-PEI70K-FITC@Yb/SDBS is subsequently applied as an amplified photocatalysis toolbox for universally regulating the generation of reactive oxygen species (ROS). Boosting 3,3',5,5'-tetramethylbenzidine (TMB) oxidation to produce blue products, a dual-mode biosensor is fabricated for improving the diagnosis of programmed death ligand-1-positive (PDL1) cancer exosomes. Exosomes were captured by Fe3O4 modified by the PDL1 aptamer, enabling replacement of alkaline phosphatase (ALP)-labeled multiple hybridized chains; then, the isolated ALP triggered a hydrolysis reaction to block the generation of oxTMB. Detection sensitivity improves by 1 order of magnitude through SDBS modulation, down to 104 particles/mL. The sensor performed well clinically in distinguishing cancer patients from healthy individuals, expanding physiological applications of near-infrared lanthanide luminescence.

Sensitizing visible and near-infrared lanthanide (Ln3+ = Er3+/Ho3+) luminescence within a semiconductor Sr2CeO4 host

Sensitizing visible and near-infrared lanthanide (Ln3+ = Er3+/Ho3+) luminescence within a semiconductor Sr2CeO4 host

Manganese Ion‐Sensitized Near‐Infrared Light in Cs2NaBi1−xErxCl6 Lead‐Free Double Perovskite

AbstractLead‐free double perovskites (DPs) with unique optical properties are of interest for broad applications. However, improving near‐infrared (NIR) photoluminescence (PL) in lead‐free DPs is still a challenge. Herein, in order to increase the NIR PL intensity and extend the infrared multicolor luminescence, transition metal Mn2+ is doped into Cs2NaBi1−xErxCl6 lead‐free DPs. Steady‐state and time‐resolved PL studies show that efficient energy transfer from Mn2+ to Er3+ is obtained, leading to NIR PL at ≈1.54 µm can be enhanced 11‐fold compared to Er3+ singly alloyed sample and a PL quantum yield of ≈14.2%. Moreover, the Mn2+‐mediated sensitized strategy can expand to other NIR lanthanide ions (Ho3+ at ≈0.98 µm or Nd3+ at ≈1.07 µm). The as‐synthesized Mn2+ doped Cs2NaBi1−xErxCl6 DPs exhibit robust stability against heat, ultraviolet light, and environmental oxygen/moisture. Finally, the lead‐free DPs phosphor‐converted multifunctional white light‐emitting diode device containing visible and NIR light is fabricated. This work guides constructing energy transfer pathways in DPs and opens new perspectives for the development of lanthanide‐functionalized DPs as promising materials for optoelectronic devices operating in the NIR region.

Stepwise Increase of NdIII -Based Phosphorescence by AIE-Active Sensitizer: Broadening the AIPE Family from Transition Metals to Discrete Near-Infrared Lanthanide Complexes*.

We designed two near-infrared (NIR) lanthanide complexes [(L)2 -Nd(NO3 )3 ] (L=TPE2 -BPY for 1, TPE-BPY for 2) by employing aggregation-induced emission (AIE)-active tetraphenylethylene (TPE) derivatives as sensitizers, which possessed matched energy to NdIII , prevented competitive deactivation under aggregation, even shifted the excitation window toward 600 nm by twisted intramolecular charge transfer. Furthermore, benefiting from the 4 f electron shielding effect and antenna effect, the enhanced excitation energies of the AIE-active sensitizers by structural rigidification transferred into the inert NdIII excited state through 3 LMCT, affording the first aggregation-induced phosphorescence enhancement (AIPE)-active discrete NIR-emitting lanthanide complexes. As 1 equipped with more AIE-active TPE than 2, L→Nd energy transfer efficiency in the former was higher than that in the latter under the same conditions. Consequently, the crystal of 1 exhibited one of the longest lifetimes (9.69 μs) among NdIII -based complexes containing C-H bonds.

Porpholactone Chemistry: Shining New Light on an Old Cofactor.

The emergence of porpholactone chemistry, discovered over 30 years ago, has significantly stimulated the development of biomimetic tetrapyrrole chemistry. It offers an opportunity, through modifications of non-pyrrolic building blocks, to clarify the relationship between chemical structure and excited-state properties, deciphering the structural code for the biological functions of life pigments. With intriguing photophysical properties in the red to near-infrared (NIR) regions, facile modulation of their electronic nature by fine-tuning chemical structures, and coordination ability with diverse metal ions, these novel porphyrinoids have favorable prospects in the fields of optical materials, bioimaging and therapy, and catalysis. In this Minireview, we summarize the brief history of porpholactone chemistry, and focus on the studies carried out in our group, particularly on the regioisomeric effect, NIR lanthanide luminescence, and metal catalysis. We outline the perspectives of these compounds in the construction of porpholactone-related biomedical applications and optical and energy materials, in order to inspire more interest and further advance bioinspired inorganic chemistry and lanthanide chemical biology.

Influences of reaction temperature and pH on structural diversity of visible and near-infrared lanthanide coordination compounds based on bipyridyl carboxylate and oxalate ligands

Four series lanthanide coordination compounds, [Ln(bpdc)(ox)0.5(H2O)]n·nH2O (Ln ​= ​La (1), Ce (2), Gd (3)), [Ln(bpdc)(ox)0.5(H2O)2]n (Ln ​= ​Ce (4), Pr (5), Nd (6)), [Ln2(bpdc)2(ox)(H2O)4]n·4nH2O (Ln ​= ​Nd (7), Sm (8)), [Ln2(bpdc)2(ox)(H2O)4]·H2O (Ln ​= ​Er (9), Yb (10)) (H2bpdc ​= ​2,2′-bipyridine-6,6′-dicarboxylic acid, H2ox ​= ​oxalic acid) were achieved under hydrothermal conditions by the reactions of lanthanide trichlorides with a rigid bipyridyl derivative and oxalic acid. Compounds 1–3 present a 6-connected hxl topological net with binuclear [Ln2(bpdc)2]2+ units. Compounds 4–6 display a 3-connected ths ThSi2 topological 3D framework with butterfly-like structure. Compounds 7–8 possess a ladder-shaped chain, and further linked by hydrogen bonds to form a 2D supramolecular layer. Compounds 9–10 show a binuclear molecular structure, and a 2D supramolecular layer structure is formed through hydrogen bonding interactions. Meanwhile, the reaction temperature and pH play important roles on the ultimate structures. These lanthanide compounds exhibit typical visible and near-infrared luminescence, as well as good thermal stability.

A role of copper(II) ions in the enhancement of visible and near-infrared lanthanide(III) luminescence

Most of the existing optical methods for CuII detection rely on a “turn-off” approach using visible lanthanide(III) luminescence. In this work we present an innovative molecular systems where the podands bis(2-hydrazinocarbonylphenyl) ethers of ethylene glycol (L1) and diethylene glycol (L2) have been designed, synthesised and tested with an ultimate goal to create a "turn-on" lanthanide(III)-based molecular probe for the specific detection of CuII ions based on both visible (TbIII, EuIII) and near-infrared (NdIII, YbIII) emission. Quantum yields of the characteristic LnIII emission signals increases by at least two-orders of magnitude upon addition of CuII into water/acetonitrile (9/1) solutions of LnL (L=L1, L2) complexes. A detailed investigation of ligand-centred photophysical properties of water/acetonitrile (9/1) solutions of CuL, GdL and GdCuL complexes revealed that the presence of CuII ions does not significantly affect the energy positions of the singlet (32,260cm−1) and triplet (25,640–25,970cm−1) states, but partially or fully eliminates the singlet state quenching through an electron transfer mechanism. This effect increases the probability of intersystem crossing leading to enhanced triplet-to-singlet emission ratio and to longer triplet state lifetimes. The redox activity of hydrazine moieties and their ability to reduce CuII to CuI has been indicated by a qualitative assay with neocuproine. Finally, the probe demonstrates a good selectivity towards CuII over other transition metal ions: the addition of divalent ZnII, CdII, PdII, NiII, CoII or trivalent FeIII, GaIII, InIII ion salts into solutions of TbL either does not affect emission intensity or increases it to a maximum of 2–3 times, while, under similar experimental conditions, the presence of CuII results in a 20- to 30-times lanthanide luminescence enhancement. This new strategy results in a versatile and selective optical platform for the design of efficient “turn-on” sensors for CuII ions based on visible and near-infrared LnIII luminescence.

Highly emitting near-infrared lanthanide "encapsulated sandwich" metallacrown complexes with excitation shifted toward lower energy.

Near-infrared (NIR) luminescent lanthanide complexes hold great promise for practical applications, as their optical properties have several complementary advantages over organic fluorophores and semiconductor nanoparticles. The fundamental challenge for lanthanide luminescence is their sensitization through suitable chromophores. The use of the metallacrown (MC) motif is an innovative strategy to arrange several organic sensitizers at a well-controlled distance from a lanthanide cation. Herein we report a series of lanthanide “encapsulated sandwich” MC complexes of the form Ln3+[12-MCZn(II),quinHA-4]2[24-MCZn(II),quinHA-8] (Ln3+[Zn(II)MCquinHA]) in which the MC framework is formed by the self-assembly of Zn2+ ions and tetradentate chromophoric ligands based on quinaldichydroxamic acid (quinHA). A first-generation of luminescent MCs was presented previously but was limited due to excitation wavelengths in the UV. We report here that through the design of the chromophore of the MC assembly, we have significantly shifted the absorption wavelength toward lower energy (450 nm). In addition to this near-visible inter- and/or intraligand charge transfer absorption, Ln3+[Zn(II)MCquinHA] exhibits remarkably high quantum yields, long luminescence lifetimes (CD3OD; Yb3+, QLnL = 2.88(2)%, τobs = 150.7(2) μs; Nd3+, QLnL = 1.35(1)%, τobs = 4.11(3) μs; Er3+, QLnL = 3.60(6)·10–2%, τobs = 11.40(3) μs), and excellent photostability. Quantum yields of Nd3+ and Er3+ MCs in the solid state and in deuterated solvents, upon excitation at low energy, are the highest values among NIR-emitting lanthanide complexes containing C–H bonds. The versatility of the MC strategy allows modifications in the excitation wavelength and absorptivity through the appropriate design of the ligand sensitizer, providing a highly efficient platform with tunable properties.

Lanthanide near infrared imaging in living cells with Yb 3+ nano metal organic frameworks

We have created unique near-infrared (NIR)-emitting nanoscale metal-organic frameworks (nano-MOFs) incorporating a high density of Yb(3+) lanthanide cations and sensitizers derived from phenylene. We establish here that these nano-MOFs can be incorporated into living cells for NIR imaging. Specifically, we introduce bulk and nano-Yb-phenylenevinylenedicarboxylate-3 (nano-Yb-PVDC-3), a unique MOF based on a PVDC sensitizer-ligand and Yb(3+) NIR-emitting lanthanide cations. This material has been structurally characterized, its stability in various media has been assessed, and its luminescent properties have been studied. We demonstrate that it is stable in certain specific biological media, does not photobleach, and has an IC50 of 100 μg/mL, which is sufficient to allow live cell imaging. Confocal microscopy and inductively coupled plasma measurements reveal that nano-Yb-PVDC-3 can be internalized by cells with a cytoplasmic localization. Despite its relatively low quantum yield, nano-Yb-PVDC-3 emits a sufficient number of photons per unit volume to serve as a NIR-emitting reporter for imaging living HeLa and NIH 3T3 cells. NIR microscopy allows for highly efficient discrimination between the nano-MOF emission signal and the cellular autofluorescence arising from biological material. This work represents a demonstration of the possibility of using NIR lanthanide emission for biological imaging applications in living cells with single-photon excitation.

Sensitized Near-Infrared Lanthanide Luminescence from Nd(III)- and Yb(III)-Based Cyclen−Ruthenium Coordination Conjugates

The development of novel mixed lanthanide-transition-metal (f-d) based supramolecular self-assemblies made from neodymium- and ytterbium-based tetraamide-functionalized cyclen complexes bearing a single 1,10-phenanthroline moiety coordinating to a RuII(bipy)2 (bipy = bipyridine) unit is described. Excitation of the Ru(II) metal-to-ligand charge-transfer band in water gave rise to long-wavelength sensitized emission from the Yb(III) or Nd(III) centers, observed in the near-infrared.

Calix[4]azacrowns as Novel Molecular Scaffolds for the Generation of Visible and Near-Infrared Lanthanide Luminescence

Two calix[4]azacrowns, capped with two aminopolyamide bridges, were used as ligands for the complexation of lanthanide ions [Eu(III), Tb(III), Nd(III), Er(III), La(III)]. The formation of 1:2 and 1:1 complexes was observed, and stability constants, determined by UV absorption and fluorescence spectroscopy, were found to be generally on the order of log beta(11) approximately 5-6 and log beta(12) approximately 10. The structural changes of the ligands upon La(III) complexation were probed by 1H NMR spectroscopy. The two ligands were observed to have opposite fluorescence behaviors, namely, fluorescence enhancement (via blocking of photoinduced electron transfer from amine groups) or quenching (via lanthanide-chromophore interactions) upon metal ion complexation. Long-lived lanthanide luminescence was sensitized by excitation in the pi,pi band of the aromatic moieties of the ligands. The direct involvement of the antenna triplet state was demonstrated via quenching of the ligand phosphorescence by Tb(III). Generally, Eu(III) luminescence was weak (Phi(lum) </= 0.01%) and much shorter lived (tau(lum) = 0.36 ms) than the Tb(III) emission. The latter, on the other hand, reached lifetimes of up to 2.60 ms and quantum yields as high as 12% for one of the ligands. Water/deuterium oxide exchange experiments showed the presence of only one solvent molecule in the coordination sphere of the lanthanides. However, Eu(III) luminescence was efficiently quenched by NH oscillators and the presence of a ligand-to-metal charge transfer state. Near-infrared luminescence of Nd(III) was also generated by energy-transfer sensitization.

Curcuminoid Ligands for Sensitization of Near-Infrared Lanthanide Emission

Fluorescent lanthanide complexes were synthesized using a non-phenolic analog of curcumin as the principal chromophoric chelating ligand. Sensitized, near-infrared fluorescence is observed in these complexes as a result of photo-excitation of the chromophoric ligands, population of the molecular triplet state, and transfer of energy to the emitting lanthanide ion. For the purpose of intra-molecular energy transfer, the triplet states of curcuminoid ligands are more favorably matched with the excited electronic states of neodymium and ytterbium ions than those associated with less conjugated beta-diketonate ligands. Sensitization of fluorescence through an internal redox reaction, thought to occur in other ytterbium complexes, is predicted to be less probable under the present circumstances.

Re(I) sensitised near-infrared lanthanide luminescence from a hetero-trinuclear Re2Ln array.

The trinuclear complexes Re2Ln (Ln = Nd, Yb or Er) contain two Re(I) tricarbonyl units linked to a DTPA binding site via 2,2'-bipyridyl ligands; Ln(III)-centred emission is sensitised by the Re(I) MLCT excited states.

Transition metal complexes as a new class of photosensitizers for near-infrared lanthanide luminescence

In this paper, we report the near-infrared lanthanide luminescence of neodymium(III) and ytterbium(III) sensitized by energy transfer from the triplet excited state of a transition metal complex. In the present systems, polydentate neodymium(III) and ytterbium(III) complexes have been functionalized with the transition metal complexes ruthenium-tris(bipyridine) or ferrocene as the light harvesting units. Ruthenium-tris(bipyridine) and ferrocene have suitable triplet state energies for energy transfer to neodymium(III) and ytterbium(III), and have absorption bands in the visible part of the electromagnetic spectrum. The energy transfer process in the ruthenium-tris(bipyridine) complexes could be studied in detail because the donating state of the antenna (the 3MLCT state) is luminescent.

Transition Metal Complexes as Photosensitizers for Near-Infrared Lanthanide Luminescence.

Energy transfer (ET) from ferrocene or ruthenium tris(bipyridine) functionalized light-harvesting units allows the first observation of sensitized near-infrared (NIR) lanthanide (Ln) luminescence (Lum.; see scheme, Exc.=excitation). Since the donating triplet state of the ruthenium tris(bipyridine) antenna is luminescent, the sensitization process could be studied in detail.

Transition Metal Complexes as Photosensitizers for Near-Infrared Lanthanide Luminescence

Sensibilisierte Nah-Infrarot-Lumineszenz (NIR-Lum.) wurde bei Lanthanoiden (Ln) erstmals beobachtet (siehe Schema; Exc.=Anregung). Ermöglicht wurde dies durch Energietransfer (ET) von Ferrocen- oder Tris(bipyridin)ruthenium-funktionalisierten lichtsammelnden Einheiten. Dank der Luminszenz des Triplettzustands des Ru-Donors ließ sich der Sensibilisierungsvorgang detailliert untersuchen.

Efficient visible light sensitisation of water-soluble near-infrared luminescent lanthanide complexes

Fluorexon (4′,5′-bis[N,N-bis(carboxymethyl)aminomethyl]fluorescein) forms stable, water-soluble complexes with lanthanide ions. The complexes with neodymium(III), erbium(III) and ytterbium(III) display sensitised near-infrared lanthanide luminescence upon excitation of the fluorexon with visible light. The photosensitisation efficiency is very high (0.5–1.0) as a result of lanthanide-enhanced intersystem crossing in the sensitising chromophore and rapid intracomplex energy transfer. The overall luminescence quantum yields, however, are low (2 × 10−4–5 × 10−3) due to nonradiative deactivation of the excited lanthanide ion.