Luminescent α-diimine complexes of ruthenium(II) containing scorpionate ligands

We describe the synthesis, characterization, and reactivity of several Ru(II) complexes of the type cis-L₂Ru(Z)ⁿ⁺, where L is an α-diimine [e.g. 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)] ligand and Z is a bis-coordinated scorpionate ligand such as tris-(1-pyrazolyl)methane (HC(pz)₃, PZ=1-pyrazolyl; n=2) or tetrakis-(1-pyrazolyl)borate anion (B(pz)₄ ⁻; n=1). The complexes each exhibit strong visible absorption assigned as a π*(L)←dπ(Ru) metal-to-ligand charge-transfer (MLCT) transition characteristic of the cis-L₂Ru²⁺ kernel. A corresponding MLCT excited state emission is observed in room temperature CH₃CN solution, although emission energies, lifetimes, and quantum yields are reduced relative to Ru(bpy)₃ ²⁺. Electronic spectra and cyclic voltammetry measurements indicate that the relative π-acceptor abilities of the coordinated Z are: Z=(1H-pyrazolyl)₂(pz)₂B(pz)₂<(pyridine)₂<(pz)₂CH(pz). Uncoordinated pz groups of cis-(bpy)₂Ru(pz)₂B(pz)₂ ⁺ can be reacted to form a sterically hindered, localized-valence (K_com33 l mol⁻¹) cis,cis-(bpy)₂Ru^II(pz)₂B(pz)₂Ru^II(bpy)₂ ³⁺ dimer. The dimer properties are interpreted by comparison to the known cis-(bpy)₂Ru^II(pz)₂Ru^II(bpy)₂ ²⁺ analog. The dimer is photoreactive and undergoes an asymmetrical photocleavage in CH₃CN (yielding cis-(bpy)₂Ru^III(pz)₂B(pz)₂ ²⁺ and cis-(bpy)₂Ru^II(CH₃CN)₂ ²⁺), similar to the corresponding thermal reaction observed for the mixed-valence cis-(bpy)₂Ru^II(pz)₂Ru^III(bpy)₂ ³⁺ system.     

Upconversion luminescence resonance energy transfer-based aptasensor for the sensitive detection of oxytetracycline

In this work, a biosensor based on luminescence resonance energy transfer (LRET) from NaYF₄:Yb,Tm upconversion nanoparticles (UCNPs) to SYBR Green I has been developed. The aptamers are covalently linked to UCNPs and hybridized with their complementary strands. The subsequent addition of SYBR Green allows SYBR Green I to insert into the formed double-stranded DNA (dsDNA) duplex and brings the energy donor and acceptor into close proximity, leading to the fluorescence of UCNPs transferred to SYBR Green I. When excited at 980 nm, the UCNPs emit luminescence at 477 nm, and this energy is transferred to SYBR Green I, which emits luminescence at 530 nm. In the presence of oxytetracycline (OTC), the aptamers prefer to bind to its corresponding analyte and dehybridize with the complementary DNA. This dehybridization leads to the liberation of SYBR Green I, which distances SYBR Green I from the UCNPs and recovers the UCNPs' luminescence. Under optimal conditions, a linear calibration is obtained between the ratio of I₅₃₀ to I₄₇₇ nm (I₅₃₀/I₄₇₇) and the OTC concentration, which ranges from 0.1 to 10 ng/ml with a limit of detection (LOD) of 0.054 ng/ml.     

Characterization of passive dosimeters in proton pencil beam scanning – A EURADOS intercomparison for mailed dosimetry audits in proton therapy centres

The lack of mailed dosimetry audits of proton therapy centres in Europe has encouraged researchers of EURADOS Working Group 9 (WG9) to compare response of several existing passive detector systems in therapeutic pencil beam scanning.Alanine Electron Paramagnetic Resonance dosimetry systems from 3 different institutes (ISS, Italy; UH, Belgium and IFJ PAN, Poland), ^natLiF:Mg, Ti (MTS-N) and ^natLiF:Mg, Cu, P (MCP-N) thermoluminescent dosimeters (TLDs), GD-352M radiophotoluminescent glass dosimeters (RPLGDs) and Al₂O₃:C optically stimulated dosimeters (OSLDs) were evaluate. Dosimeter repeatability, batch reproducibility and response in therapeutic Pencil Beam Scanning were verified for implementation as mail auditing system.Alanine detectors demonstrated the lowest linear energy transfer (LET) dependence with an agreement between measured and treatment planning system (TPS) dose below 1%. The OSLDs measured on average a 6.3% lower dose compared to TPS calculation, with no significant difference between varying modulations and ranges. Both GD-352M and MCP-N measured a lower dose than the TPS and luminescent response was dependent on the LET of the therapeutic proton beam. Thermoluminescent response of MTS-N was also found to be dependent on the LET and a higher dose than TPS was measured with the most pronounced increase of 11%.As alanine detectors are characterized by the lowest energy dependence for different parameters of therapeutic pencil beam scanning they are suitable candidates for mail auditing in proton therapy. The response of luminescence detector systems have shown promises even though more careful calibration and corrections are needed for its implementation as part of a mailed dosimetry audit system.     

Ecomorphological adaptations to bioluminescence in Porichthys notatus

Synopsis The midshipman fish, Porichthys notatus, is a visually active nocturnal predator. It must acquire exogenous sources of luciferin to remain luminescent and feeds on a variety of luminescent prey. Its ecomorphological adaptations for nocturnal predation were examined by observing predation on zooplankton illuminated by dinoflagellates. Its visual sensitivity is well adapted for detection of its own luminescence and its prey's luminescence. P. notatus can detect the luminescence of dinoflagellates and use this indirect light to increase predation on nonluminescent prey. Flash frequency and duration modulated predation rates. The interval between flash onset and strike initiation regulated strike success. High prey concentration decreased predation success due to increased optical and mechanosensory noise. Other ecomorphological adaptations of this predator to its special photic environment include a pigmented digestive tract, duplex retina with the capacity to discriminate emission spectra, contractible pupil, and the potential to counter illuminate. These morphological adaptations combined with an ambush predator style allow effective predation while minimizing exposure risk.     

Multiplexed immunoassays for proteins using magnetic luminescent nanoparticles for internal calibration

Suspension arrays present a promising tool for multiplexed assays in large-scale screening applications. A simple and robust platform for quantitative multiprotein immunoanalysis has been developed with the use of magnetic Co:Nd:Fe(2)O(3)/luminescent Eu:Gd(2)O(3) core/shell nanoparticles (MLNPs) as a carrier. The magnetic properties of the MLNPs allow their manipulation by an external magnetic field in the separation and washing steps in the immunoassay. Their optical properties enable the internal calibration of the detection system. The multiplexed sandwich immunoassay involves dual binding events on the surface of the MLNPs functionalized with the capture antibodies. Secondary antibodies labeled with conventional organic dyes (Alexa Fluor) are used as reporters. The amount of the bound secondary antibody is directly proportional to the concentration of the analyte in the sample. In our approach, the fluorescence intensity of the reporter dye is related to the luminescence signal of the MLNPs. In this way, the intrinsic luminescence of the MLNPs serves as an internal standard in the quantitative immunoassay. The concept is demonstrated for a simultaneous immunoassay for three model proteins (human, rabbit, and mouse IgGs). The method uses a standard bench plate reader. It can be applied to disease diagnostics and to the detection of biological threats.     

Photophysical properties of a new, stable corrole-porphyrin dyad

The synthesis of a new stable corrole-porphyrin dyad, made up of a free-base corrole and a free-base porphyrin connected by an amide linker is presented and the characterization of the photoinduced processes taking place in the array is described. The dyad was synthesized from meso-substituted trans-A₂B-corrole bearing acid chloride functionality and meso-substituted A₃B-porphyrin possessing one free NH₂ group. The structure of the dyad was carefully designed and optimized to ensure stability of the molecule. The preparation of the amine component was achieved via phthalimide protection strategy which occurred to be more efficient than the traditional nitro group reduction. Results obtained from time resolved and steady state spectroscopy experiments indicate the existence of an equilibrium between the two lowest singlet excited states of the dyad, one localized on the corrole and the other on the porphyrin unit, which are nearly iso-energetic (ΔG = −0.01 eV). Independently of the excited component, energy transfer occurs in both directions (very likely with a Förster mechanism) and an equilibrium with K_eq close to 1 is rapidly set with back and forward rates of the order of 10⁹ s⁻¹. Both states decay with a common lifetime (6.2 ns) that is longer compared to the corrole model (3.9 ns) and shorter with respect to the porphyrin reference (9.9 ns). The longer lived excited state localized on porphyrin acts as a reservoir for the excited state localized on corrole. At 77 K the equilibration does not take place during the lifetime of the excited states, and the decay of the two species occurs independently.     

Exploring a series of monoethynylfluorenes as alkynylating reagents for mercuric ion: Synthesis, spectroscopy, photophysics and potential use in mercury speciation

New luminescent mononuclear mercury(II) mono- and dialkynylated complexes containing substituted fluorene and fluorenone units [R-CC-HgCH₃] and [R-CC-Hg-CC-R] (R = 9,9-dialkylfluorene-2-yl and fluoren-9-one-2-yl; alkyl = H, ethyl, hexyl, octyl, hexadecyl) were prepared in good yields by mercuration of terminal acetylene R-CCH with CH₃HgCl and HgCl₂ at room temperature via the dehydrohalogenation reaction. The structures of these organomercurial compounds were characterized by IR and NMR spectroscopies, elemental analysis and FAB mass spectrometry. Their optical and photoluminescence spectra were also studied. The structural features of one complex was elucidated by X-ray crystallography in which there is an indication of weak mercuriophicity among the molecules in the solid state. A new protocol is developed for derivatization of inorganic mercury(II) ion into dialkynyl mercury(II) compounds followed by the ready extraction into dichloromethane, which can be analyzed by HPLC technique using UV detection. These results have important implications in the development of analytical procedures for the determination of mercuric ion in aqueous solutions.     

Synthesis, characterization and luminescence property of heterobimetallic trinuclear Mo(W)-Ag-S clusters containing 1,2-bis(diphenylphosphino)-1,2-dicarba-closo-dodecaborane

Reactions of (NH₄)₂MS₄ or (NH₄)₂MOS₃ (M = Mo, W) with AgSCN and closo carborane diphosphine ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ (L) in CH₂Cl₂ yielded four heterobimetallic trinuclear Mo(W)-Ag-S clusters: [Ag₂MoS₄L₂] (1), [Ag₂WS₄L₂] (2), [Ag₂MoOS₃L₂] (3) and [Ag₂WS₄L₂] (4), respectively. All the new clusters have been characterized by elemental analysis, FT-IR, UV-Vis, ¹H and ¹³C NMR spectroscopy and their molecular structures (except for 3) were further confirmed by single-crystal X-ray diffraction. X-ray crystal structure analysis showed that the closo carborane diphosphine ligand was coordinated bidentately to Ag(I) atom through its two phosphorus atoms, resulting in a stable five-member chelating ring between the diphosphine ligand and the metal. The coordination sphere of the central M atom, as well as all the Ag atoms, was tetrahedron. The skeletons of these clusters could be classified into two types: with (NH₄)₂MS₄, the three metal atoms (two Ag atoms and one M atom) are in a linear conformation, while with (NH₄)₂MOS₃, the conformation of the heterobimetallic trinuclear cluster is butterfly shaped. The luminescence properties of the clusters were investigated in CH₂Cl₂ solution at room temperature and for the first time the butterfly-shaped Ag-W-S cluster containing the Ag₂WS₄ core has been proved to show luminescence property.     

Time-resolved fluorescence-based assay for rapid detection of Escherichia coli

Fast and simple detection of pathogens is of utmost importance in health care and the food industry. In this article, a novel technology for the detection of pathogenic bacteria is presented. The technology uses lytic-specific bacteriophages and a nonspecific interaction of cellular components with a luminescent lanthanide chelate. As a proof of principle, Escherichia coli-specific T4 bacteriophage was used to infect the bacteria, and the cell lysis was detected. In the absence of E. coli, luminescent Eu³⁺–chelate complex cannot be formed and low time-resolved luminescence signal is monitored. In the presence of E. coli, increased luminescence signal is observed as the cellular contents are leached to the surrounding medium. The luminescence signal is observed as a function of the number of bacteria in the sample. The homogeneous assay can detect living E. coli in bacterial cultures and simulated urine samples within 25 min with a detection limit of 1000 or 10,000 bacterial cells/ml in buffer or urine, respectively. The detection limit is at the clinically relevant level, which indicates that the method could also be applicable to clinical settings for fast detection of urine bacteria.     

Dimethylsulfoxide gold-thallium complexes. Effects of the metal-metal interactions in the luminescence

The heteropolynuclear complexes [AuTl(C₆X₅)₂]_n (X = F, Cl) react with dimethylsulfoxide (DMSO) in different molar ratios leading to products of stoichiometry [Tl₂{Au(C₆F₅)₂}₂{μ-DMSO}₃]_n (1), and [Tl₂{Au(C₆Cl₅)₂}₂{μ-DMSO}₂]_n (2). These complexes have been structurally characterized and can be viewed as extended linear chains built with Tl-Au-Tl units in which the thallium atoms are bridged by the oxygen atoms of DMSO ligands. Additional [Au(C₆X₅)₂]⁻ fragments interact with one or two thallium centres, respectively, giving rise to two different types of metal-metal interactions in each molecule. Both of them show a strong luminescence in solid state and complex 2 also in solution. The thallium-thallium interaction in this complex is considered to be the responsible of its luminescence, which remains in solution.