Luminescence In Aqueous Solution Research Articles

Red Room-Temperature Phosphorescence Supramolecular Assemblies Based on Cucurbit[7]uril: Reversible Temperature Stimulation Response and Cell-Specific Silver Ion Imaging.

Solid-state materials with efficient room-temperature phosphorescence (RTP) emission have been widely used in materials science, and organic RTP-emitting systems with heavy-metal doping in aqueous solutions have attracted much attention in recent years. A novel supramolecular interaction was induced by host-guest assembly using cucurbit[7]uril (Q[7]) as the host and brominated naphthalimide phosphor as the guest. This interaction was further enhanced through synergistic chelation stimulated by analytical silver ion complexation. This approach facilitated the system's structural rigidity, intersystem crossing, and oxygen shielding. We achieved deep red phosphorescence emission in aqueous solution and ambient conditions along with quantitative determination of silver ions. The new complex exhibited good reversible thermoresponsive behavior and was successfully applied for the first time to target phosphorescence imaging of silver ions in the mitochondria of A549 cancer cells. These results are beneficial for constructing novel RTP systems with stimulus-responsive luminescence in aqueous solution, contributing to future research in bioimaging, detection, optical sensors, and thermometry materials.

Lanthanide Metal-Organic Framework Isomers with Novel Water-Boosting Lanthanide Luminescence Behaviors.

Lanthanide metal-organic frameworks (Ln-MOFs) with exceptional optical performance and structural diversity offer a unique platform for the development of luminescent materials. However, Ln-MOFs often suffer from luminescence quenching by high-vibrating oscillators, especially in aqueous solution. Thus, multiple strategies have been adopted to improve the luminescence of Ln3+. Anomalous research about water-induced lanthanide luminescence enhancement of Ln-MOFs is in the primary stage. Here, two Eu-based metal-organic framework (Eu-MOF) isomers named QXBA-Eu-1 and QXBA-Eu-2 were constructed by using the same ligand under different solvent thermal conditions, which exhibited distinctive water- and methanol-boosting emission behaviors. As for QXBA-Eu-1, water and methanol molecules replaced the free N,N-dimethylacetamide (DMA) molecules in the framework, repressed the rotation or libration suppression of the QXBA linker, and formed hydrogen bonds with the coordinated water molecules, which suppressed the O-H high-energy vibrations, reduced nonradiative transitions, stabilized the T1 state, and facilitated the intersystem crossing (ISC) process. For QXBA-Eu-2, water molecules tended to replace the coordinated DMA ligands, which altered the S1 and T1 energy levels of the ligand and facilitated the ligand-to-metal energy transfer (LMET) process and strengthened the luminescence of Eu3+. Importantly, free solvent molecules and the hydroxylation of Eu3+ centers also restrained the rotation or libration of the QXBA linker, by which the nonradiative transition was further inhibited and the lanthanide luminescence enhanced. Thus, this work not only opened an unprecedented path to enhance lanthanide luminescence in aqueous solution but also expanded its application scope.

Photoluminescent terbium-metal-organic framework and its trace bismuth-ion sensing performance

A new Tb-MOF [Tb(BDC)TDC] based on terephthalic acid (H2BDC) and thiophene-2,5-dicarboxylic acid (H2TDC) was synthesized successfully by solvothermal method. The crystal structure, morphology, thermal stability and photoluminescence properties were characterized in detail. Under the excitation of 310 ​nm, Tb-MOF presents bright green luminescence in aqueous solution. Bismuth-ion (Bi3+) can quickly and specifically quench the luminescence of Tb-MOF, and the response time is only 9 ​s. The quenching mechanism is that Tb3+ in the metal center of Tb-MOF is replaced by Bi3+, resulting in luminescence quenching and realizing the Bi3+ detection. The quenching constant (Ksv) and the detection limit for Bi3+ are 0.024 ​μM−1 and 4.98 ​μM, respectively. The synthesized Tb-MOF can be used as the sensor for trace Bi3+ detection in the aqueous solution.

Photophysical Properties and DNA Binding of Two Intercalating Osmium Polypyridyl Complexes Showing Light-Switch Effects.

The synthesis and photophysical characterization of two osmium(II) polypyridyl complexes, [Os(TAP)2dppz]2+ (1) and [Os(TAP)2dppp2]2+ (2) containing dppz (dipyrido[3,2-a:2′,3′-c]phenazine) and dppp2 (pyrido[2′,3′:5,6]pyrazino[2,3-f][1,10]phenanthroline) intercalating ligands and TAP (1,4,5,8-tetraazaphenanthrene) ancillary ligands, are reported. The complexes exhibit complex electrochemistry with five distinct reductive redox couples, the first of which is assigned to a TAP-based process. The complexes emit in the near-IR (1 at 761 nm and 2 at 740 nm) with lifetimes of >35 ns with a low quantum yield of luminescence in aqueous solution (∼0.25%). The Δ and Λ enantiomers of 1 and 2 are found to bind to natural DNA and with AT and GC oligodeoxynucleotides with high affinities. In the presence of natural DNA, the visible absorption spectra are found to display significant hypochromic shifts, which is strongly evident for the ligand-centered π–π* dppp2 transition at 355 nm, which undergoes 46% hypochromism. The emission of both complexes increases upon DNA binding, which is observed to be sensitive to the Δ or Λ enantiomer and the DNA composition. A striking result is the sensitivity of Λ-2 to the presence of AT DNA, where a 6-fold enhancement of luminescence is observed and reflects the nature of the binding for the enantiomer and the protection from solution. Thermal denaturation studies show that both complexes are found to stabilize natural DNA. Finally, cellular studies show that the complexes are internalized by cultured mammalian cells and localize in the nucleus.

Temperature-sensitive emission of dialkylaminostyrylhetarene dyes and their incorporation into phospholipid aggregates: Applicability for thermal sensing and cellular uptake behavior

A series of dialkylaminostyrylhetarene dyes constructed from electron-rich and electron-deficient moieties of various structures connected via vinylene π-bridges are introduced as temperature-sensitive luminophores. The temperature dependent emission of the dyes in the acidified dichloromethane solutions derives from temperature-induced shift of the equilibrium between neutral and protonated forms of the dyes. The heating-induced blue shift and intensification of emission of neutral form of the dyes make them a promising basis for development of nanoparticles exhibiting temperature-sensitivity in aqueous solutions at pH typical of biological liquids. Hydrophobicity-driven incorporation of the water insoluble dyes into L-α-phosphatidylcholine(PC)-based bilayers allows to obtain water dispersible dye-PC aggregates, and to follow their emission in the aqueous solutions. Structure of the dyes has strong impact on the efficacy of the dyes incorporation into the PC-based bilayers, temperature sensitivity of emission of the dye-PC aggregates and its reversibility under the heating/cooling cycles. This enables structural optimization of the dyes in order to obtain the dye-PC species demonstrating maximal temperature dependence and reversibility of their luminescence in aqueous solutions. The selected leader exhibits low cytotoxicity exemplified for M−HeLa and Chang Liver cell lines, while the efficient cell internalization of the dye, manifested in the staining of the cell cytoplasm, opens further opportunities for biosensing applications.

Lanthanide metal-organic framework as a paper strip sensor for visual detection of sulfonamide with smartphone-based point-of-care platform

Antibiotic residues in aquatic environments have attracted wide attention. Considering the impacts on the ecosystem and human health, it is urgent to develop a rapid method for detecting antibiotic residues in the environment. In this work, a nanoscale lanthanide metal-organic framework Eu(TATB) with a stable red luminescence in aqueous solution is synthesized by the microemulsion method. Sulfamethazine (SMZ) is frequently most used in veterinary medicine as one of sulfonamides. Eu(TATB) can be used for sensitively and rapidly specific recognition of SMZ with low detection limit (0.67 μM) and eminent recyclability. In addition, a paper-based visual system for point-of-care (POC) monitoring SMZ is devised by both using filter paper embedded with Eu(TATB) and our developed portable smartphone-involved imaging cassette. The naked eyes can observe that the red luminescence of the paper sensor gradually fades away at the presence of SMZ. This provides a reliable and effective method for on-site detection of sulfonamide antibiotics in the field of environmental monitoring.

A Single Crystal Hybrid Ligand Framework of Copper(II) with Stable Intrinsic Blue-Light Luminescence in Aqueous Solution.

Single-crystal solid–liquid dual-phase hybrid organic–inorganic ligand frameworks with reversible sensing response facilitated by external stimuli have received significant attention in recent years. This report presents a significant leap in designing electronic structures that display reversible dual-phase photoluminescence properties from single-crystal hybrid ligand frameworks. Three-dimensional Cu(C3N2H4)4Cl2 complex frameworks were formed through the intermolecular hydrogen bonding and π⋯π stacking supramolecular interactions. The absorption band peaks at 627 nm were assigned to d–d transition showing 10Dq = 15,949 cm−1 and crystal field stabilization energy (CFSE) = 0.6 × 10Dq = 114.4 kJmol−1, while the ligand-to-metal charge transfer (LMCT) of complexes was displayed at 292 nm. The intense luminescence band results from LMCT present at 397 nm. Considering its structure, air stability, framework forming and stable luminescence in aqueous solution, the Cu(C3N2H4)4Cl2 complex shows potential for luminescence Cu-based sensors using emission intensity to detect heavy metal ion species.

Tunable and white luminescence from mixed lanthanide with aza-macrocycles through multistimuli responses

In this work, two aza-macrocycles (1 and 2) were designedly synthesized as hosts for sensitizing lanthanide luminescence in aqueous solution to explore new light emitting material. It is expected that macrocycle molecules can encapsulate lanthanide centers into their cavity to form new lanthanide fluorescent materials based on their excellent host–guest binding abilities. In addition, macrocycle molecules are blue emitters, so it will be possible to construct white light-emitting and color-tunable materials through the doping of both Tb3+ ions and Eu3+ ions into aza-macrocycle hosts with an appropriate molar ratio. All of experimental results verify that aza-macrocycle based lanthanide materials realized tunable luminescence and white light emissions through changing relative concentration (Tb/Eu = 1:0, 1:1, 1:2, 1:4, 1:6, 1:8, 0:1) of the constituent Ln3+ ions and the excitation wavelength from 351 nm to 395 nm. As far as we know, it is very rare that the color-tunable and white-light emission can be controlled by two types of strategies and on the basis of macrocycle hosts.

Transition-metal-based (Zn2+ and Cd2+) metal-organic frameworks as fluorescence “turn-off” sensors for highly sensitive and selective detection of hydrogen sulfide

Two new coordination polymers of [Zn(L)(4,4′-bpy)0.5].(H2O)0.25(1) and [Cd4(L)4(4,4′-bpy)2].(H2O)(2) have been solvothermally synthesized from semi-rigid ligand H2L (H2L=4,4′-dicarboxy-4″-nitrotriphenylamine) and auxiliary ligand 4,4′-bpy (4,4′-bpy=4,4′-bipyridine), which have been fully characterized by single-crystal X-ray diffraction, PXRD, IR and elemental analysis. Compound 1 is composed of interdigitated 2-D square-grid layers which are assembled from 1-D beaded chain pillared by 4,4′-bpy, whereas compound 2 comprises two interpenetrated 3-Dpcu nets which are constructed by 4,4′-bpy pillared 2-D square-grid layers. Compound 1–2 display both thermal stability and hydrolytic robustness. What is the most interesting finding is that both compounds exhibit strong luminescence in aqueous solution, and each of them can serve as a highly sensitive and selective fluorescence “turn-off” sensor for aqueous detection of hydrogen sulfide.

Transition-metal-based (Co2+, Ni2+ and Cd2+) coordination polymers constructed by a polytopic ligand integrating both flexible aliphatic and rigid aromatic carboxylate groups: Aqueous detection of nitroaromatics

Three transition-metal-based coordination polymers (1: Co2+; 2: Ni2+ and 3: Cd2+) have been solvothermally synthesized from a newly designed polytopic ligand of 4-(carboxymethoxy)-[1,1′-biphenyl]-3,4′-dicarboxylic acid (H3Lws) that integrates both flexible aliphatic and rigid aromatic carboxylate groups. In 1, each H3Lws ligand connects two Co2+ ions in the partially deprotonated form of HLws2−, whereas the H3Lws ligands in 2 and 3 are fully deprotonated (Lws3−), each linking three Ni2+ ions and seven Cd2+ ions, respectively. Compound 1 shows a one-dimensional chain structure, and compound 2 is composed of a two-dimensional waved sheet based on Ni4(μ3-OH)2(μ2-O)4 cluster. Compound 3 has a three-dimensional network structure that is constructed of two-dimensional Cd/O-based layers pillared by Lws3− spacers. Compounds 1–3 exhibit both thermal stability (>340°C) and hydrolytic robustness even under the heating condition. In particular, compound 3 displays the strongest luminescence in aqueous solution, which is almost 2.5-fold greater than that in organic solvents. More importantly, it is proved that compound 3 can serve as a highly sensitive luminescent sensor for aqueous detection of those nitro phenolic aromatics.

Water-Soluble and Highly Luminescent Europium(III) Complexes with Favorable Photostability and Sensitive pH Response Behavior.

Two highly luminescent and water-soluble Eu(III) complexes, Eu1 and Eu2, based on novel carboxyl-functionalized 1,5-naphthyridine derivatives 8-hydroxy-1,5-naphthyridine-2-carboxylic acid (H2L1) and 7-cyano-8-hydroxy-1,5-naphthyridine-2-carboxylic acid (H2L2), respectively, are designed and synthesized. The crystal structure of Eu2 indicates that the central Eu(III) ion is nine-coordinated by three tridentate ligands (O^N^O). Both Eu1 and Eu2 show strong luminescence in aqueous solution with quantum yields (lifetimes) of 28% (1.1 ms) and 14% (0.76 ms), respectively. The chelates display unique UV-light stability in solution and remain highly emissive after 100 min of strong UV irradiation (∼300 W·m-2 at 345 nm). Moreover, they exhibit reversible luminescence intensity changes with varied pH values, and the response mechanism is investigated. "Turn-on" of the Eu(III) emission upon increasing pH is realized by ligand structure change from keto to enol anion form, resulting in red-shifted absorption band and suppressed quenching from solvents and N-H vibration upon deprotonating. The results show that these novel Eu(III) complexes are quite intriguing for potential application as bioimaging agents and pH probes.

Preparation of water soluble and biocompatible AIE-active fluorescent organic nanoparticles via multicomponent reaction and their biological imaging capability

Fluorescent organic nanoparticles (FONs) with aggregation-induced emission (AIE) features have been extensively investigated for bio-imaging applications because of their unique AIE properties, biocompatibility, and well designability. In this work, AIE-active FONs have been fabricated via a “one pot” mercaptoacetic acid locking imine (MALI) reaction, in which aldehyde groups containing AIE-active dye (named as CHO-An-CHO) was covalently conjugated with NH2-terminated polymers (PEG-PABA) to form amphiphilic luminescent polymers using mercaptoacetic acid (MTA) as the “lock” molecule. These final polymers (denoted as PEG-PABA-An-CHO) possessed amphiphilic properties and could self-assemble into PEG-PABA-An-CHO FONs with excellent water dispersibility. Furthermore, thus PEG-PABA-An-CHO FONs displayed enhanced luminescence in aqueous solution due to the aggregation of AIE feature of CHO-An-CHO. More importantly, thus final PEG-PABA-An-CHO FONs exhibited desirable biocompatibility and fluorescent imaging performance. As compared with traditional stepwise methods that are laborious, time-consuming and involve separation and purification of intermediate products, thus “one pot” strategy relied on MALI reaction showed distinct advantages, including simplicity, high efficiency, universality and atom-economy. Thanks to the good applicability of MCR-MALI reaction towards different substrates, this “one pot” strategy should be a useful tool for preparing sophisticated and multifunctional AIE-active materials for different applications potential.

Multistimuli‐responsive White Luminescent Fluids Using Hybrid Lanthanide Metal–Coordinate Complex Probes

Intense white luminescence in aqueous solution is achieved via coordination of mixed lanthanide ions with non-substituted 2,2′:6′,2″-terpyridine. Chromic properties of the lanthanide hybrid molecular solutions are highly responsive to stimuli, such as changes in solvent composition, pH, temperature, anion binding, and mechanical force due to the dynamic Ln(III) coordination bonds. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Pt2Ag acetylide-doped silica nanoparticles: enabling luminescence of Pt2Ag complexes in water and sensors for highly sensitive detection of cyanide anions.

Two novel luminescent hetero-trinuclear complexes [Pt2Ag(μ-dpppy)2(C≡CC6H4R-4)4](ClO4) (R = H, 1; R = CH3, 2; dpppy = 2,6-bis(diphenylphosphino)pyridine) were synthesized by the self-assembly reaction between [Pt(C[triple bond, length as m-dash]CC6H4R-4)4](2-) and [Ag2(μ-dpppy)3](2+) and characterized by elemental analyses, electrospray ionization mass spectrometry, and (1)H NMR and (31)P{(1)H} NMR spectroscopy and by X-ray crystallography for complex 2. Two Pt2Ag complexes show strong luminescence in the solid state, but exhibit weak emission in CH2Cl2 solution and in acetonitrile-water (1 : 1, v : v) solution at room temperature. To overcome the limitations of low water solubility and weak emission in solutions, a new kind of luminescent Pt2Ag@SiO2 nanoparticles was prepared by incorporating the new Pt2Ag acetylides into monodisperse silica nanoparticles. It is noted that Pt2Ag@SiO2 nanoparticles exhibit strong luminescence in aqueous solution, and cyanide anions tend to decrease their luminescence intensity in NaHCO3-NaOH buffer solution. Based on this, a novel nanosensor for highly sensitive detection of cyanide anions was developed in the range of 0.1-10.0 μM.

Photoluminescent ZnO Quantum Dots Coated by Polymethacrylamide and Their Application in Cell Imaging

ZnO@polymer core-shell nanoparticles with stable luminescence in aqueous solutions and tunable emission were synthesized by sol-gel method,studied in cytotoxicity tests towards HeLa cells and measured by laser confocal scanning microscope.The shell of such luminescent probes is a copolymer connected the ZnO core through coordination bonds,which contains an external hydrophilic layer of polymethacrylamide and an internal hydrophobic layer of polymethacrylate.Such design protected the ZnO cores from decomposition by aqueous solutions on one hand,and assured the highly dispersity and long-term stability in water on the other hand.Cytotoxicity measurements proved this material is biocompatible and suitable for biological labels.The results of the laser confocal imaging showed these nanoparticles could penetrate the membranes of HeLa cells and exhibited stable fluorescence in the cytoplasm.

4,4′-Bis(trifluoromethyl)-2,2′-bipyridine – a multipurpose ligand scaffold for lanthanoid-based luminescence/19F NMR probes

The tetradentate ligand 4,4'-bis(trifluoromethyl)-2,2'-bipyridine-6,6'-dicarboxylic acid (H(2)1) and three corresponding anionic rare earth complexes [RE(1)2](-) (RE = Y, Tb, Dy) were synthesized. The terbium and dysprosium complexes show lanthanoid-centered luminescence in aqueous solution, as well as paramagnetically enhanced longitudinal magnetic relaxation of the (19)F nuclei.

Changes in the spontaneous luminescence of aqueous solutions under exposure to radio frequency electromagnetic radiation

This work investigates the structural-dynamic properties of water solutions of NaCl and doxorubicin by the method of spontaneous luminescence. It is shown, that the external electromagnetic field of radiofrequency-range causes an increase of the size of water clusters (molecular cell). At the same time, if the electromagnetic field is distributed relatively non-homogeneously in the space, an increase in the size of molecular cell is accompanied by a decrease in stationarity of the system's dynamic properties

Synthesis, characterization and DNA-binding and DNA-photocleavage studies of two Ru(II) complexes containing two main ligands and one ancillary ligand

DNA-binding and DNA-photocleavage properties of two Ru(II) complexes, [Ru(L 1)(dppz) 2](PF 6) 4 ( 1) and [Ru(L 2)(dppz) 2](PF 6) 4 ( 2) (L 1 = 5,5′-di(1-(triethylammonio)methyl)-2,2′-dipyridyl cation; L 2 = 5,5′-di(1-(tributylammonio)methyl)-2,2′-dipyridyl cation; dppz = dipyrido[3,2-a:2′,3′-c]phenazine, have been investigated. Experimental results show that the DNA-binding affinity of complex 1 is greater than that of 2, both complexes emit luminescence in aqueous solution, either alone or in the presence of DNA, complex 1 can bind to DNA in an intercalative mode while 2 most likely interacts with DNA in a partial intercalation fashion, and complex 2 serves as a better candidate for enantioselective binding to CT-DNA compared with 1. Moreover, complex 1 reveals higher efficient DNA cleavage activity than 2, during which supercoiled DNA is converted to nicked DNA with both complexes. Theoretical calculations for the two complexes have been carried out applying the density functional theory (DFT) method at the level of the B3LYP/LanL2DZ basis set. The calculated results can reasonably explain the obtained experimental trends in the DNA-binding affinities and binding constants ( K b) of these complexes.

Poly(arginine)-Selective Coprecipitation Properties of Self-Assembling Apoferritin and Its Tb3+Complex: A New Luminescent Biotool for Sensing of Poly(arginine) and Its Protein Conjugates

The apoferritin protein and apoferritin-Tb(3+) complex were demonstrated to form oligomeric and polymeric self-assemblies in neutral aqueous solutions, based on characterization by using luminescence and UV/Vis spectroscopy, dynamic light scattering, and transmission electron microscopy. Addition of a 20-mer or higher poly(arginine) to the solution resulted in coprecipitation through nanoscale interactions, while biological proteins and other poly(amino acids) rarely yielded precipitates under the conditions employed. The apoferritin-Tb(3+) complex assembly exhibited a particularly long-lived green luminescence in aqueous solution, and its poly(arginine)-selective precipitation behavior was followed by monitoring the changes in luminescence. The poly(arginine)-tagged albumin precipitated selectively and quantitatively, so that the apoferritin-Tb(3+) complex can function as a new luminescent biotool for the sensing of poly(arginine) and its protein conjugates.

Synthesis of 8-hydroxyquinoline functionalised DO3A ligand and Eu(III) and Er(III) complexes: Luminescence properties

The synthesis of a new DO3A-based macrocyclic ligand bearing a 8-hydroxyquinoline residue together with the preparation of its Eu 3+ and Er 3+ neutral complexes are described. In a previous report [F. Rizzo, A. Papagni, F. Meinardi, R. Tubino, M. Ottonelli, G.F. Musso, G. Dellepiane, Synth. Met. 147 (2004) 143], we have shown that lanthanide complexes display very high stability combined with a good luminescence in aqueous solution under UV radiation, which indicate an energy transfer process from the excited 8-hydroxyquinoline moiety to the metal. In this work, we correlate the ability to transfer the energy from the sensitizer to lanthanide ion with pH behaviour of the antenna. Furthermore, the variation of pH in Eu 3+ complex supports the hypothesis of presence of charge-transfer transitions. The good solubility and sensitized emission in different solvents (organic and water) are very important aspects for their technologic applications as luminescent probes or NIR-emitting devices.