Sensitive Luminescent Sensor Research Articles

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.

Synthesis and characterization of lanthanide-based coordination polymers for highly selective and sensitive luminescent sensor for Pb2+ over mixed metal ions

Three novel coordination polymers, namely, {[Pr(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (I), {[Gd(TTTPC)·(H2O)2]·2Cl·NO3·4H2O}n (II) and {[Yb(TTTPC)·(H2O)2]·3Cl·NO3·0.5DMA·6H2O}n (III) were synthesized in conventional aqueous solutions with H3TTTPC ligands (H3TTTPC = 1,1′,1″-(2,4,6-trimethylbenzene-1,3,5-triyl(methylene))-tris(pyridine-4-carboxylic acid), DMA = N,N-dimethylacetamide) and characterized by infrared spectrometry and single crystal X-ray diffraction. Experimental results show that these MOFs are isomorphous and isostructural, containing the unit of cavate 14-membered cages (Pr2(OCO)4), based on which to generate a one-dimensional (1D) infinite linear metallic chain through the linkage of two COO− groups that are further interlinked reciprocally to polymerize into three-dimensional (3D) porous frameworks. Coordination polymer III shows remarkable selectivity toward Pb2+ and it can be considered as potential selective luminescent probes for Pb2+ ion. Additionally, magnetic analysis indicates coordination polymer I presents antiferromagnetism. Besides, lanthanide contraction effect exists in as-synthesized coordination polymers.

Two Lanthanide Metal-Organic Frameworks as Remarkably Selective and Sensitive Bifunctional Luminescence Sensor for Metal Ions and Small Organic Molecules.

Two lanthanide metal-organic frameworks (Ln-MOFs) with similar structures have been synthesized through objective synthesis. The two compounds are both 2-fold interpenetrating 3D frameworks. Topological analyses reveal that complexes 1 and 2 are 6-connected pcu net. In addition, both structures were embedded in uncoordinated nitrogen atoms. As the uncoordinated pyridine groups can be used as functional groups, we tested their sensing ability toward metal ions and small organic molecules. To our delight, fluorescence measurements show the two complexes can selectively and sensitively detect for Fe3+ ion and nitromethane, which suggests that the two Ln-MOFs are promising bifunctional luminescence sensor materials with sensing metal ions and small organic molecules.

A bifunctional luminescent europium–organic framework for highly selective sensing of nitrobenzene and 4-aminophenol

A bifunctional luminescent Eu-MOF can be applied as a highly selective and sensitive bifunctional luminescence sensor to detect NB and 4-AP through an energy competition mechanism with low detection limits of 5–70 ppm and 5–110 ppm, respectively.

3D Lanthanide Metal–Organic Frameworks Based on Mono-, Tri-, and Heterometallic Tetranuclear Clusters as Highly Selective and Sensitive Luminescent Sensor for Fe3+ and Cu2+ Ions

Five novel three-dimensional lanthanide metal–organic frameworks (Ln–MOFs) constructed by 4-(3′,5′-dicarboxylphenoxy) phthalic acid (H4dcppa), namely, {[Eu(Hdcppa)(H2O)2]·H2O}n (Eu-1), [Eu1.5(dcppa) (HCOO)0.5(H2O)2]n (Eu-2), {[Ln2K2(dcppa)2(H2O)6]·mH2O}n (Ln = Eu-3, Tb-4, Gd-5, m = 5 for Eu-3 and Tb-4; m = 4 for Gd-5) (HCOOH = formic acid) have been prepared by hydro(solvo)thermal method and fully characterized. Structural analyses indicated that H4dcppa ligand took four different coordination fashions in 1–5 and, thus, resulted in diversity of the targeted Ln–MOFs: Eu-1 displays the rare 3D (5,5)-connected vbk net, containing one-dimensional left- and right-handed helical chains; Eu-2 possesses a 3D (3,8)-connected tfz-d topology constructed by trinuclear paddlewheel [Eu3(CO2)6] SBUs; 3–5 are isostructural and show 3D (Ln-dcppa4–) + 2D (K-dcppa4–) → 3D (LnK-dcppa4–) structure. Eu-3, with regular 1D channels and open Lewis basic oxygen atoms on the pore surface was utilized for specific sensing and bindin...

Microporous Lanthanide Metal-Organic Frameworks with Multiple 1D Channels: Tunable Colors, White-Light Emission, and Luminescent Sensing for Iron(II) and Iron(III).

A new series of isostructural lanthanide-based metal-organic frameworks, [H3 O][HN(CH3 )3 ]2 [Ln3 L6 ] (Ln=Gd (1), Eu (2), and Tb (3); H2 L=1,3-benzenedicarboxylic acid), was prepared under solvothermal conditions. Single-crystal XRD studies reveal that these compounds are 3D microporous frameworks with 1D channels distributed in four different directions. The 1D channels contain protonated water molecules and trimethylammonium cations, which can be partially exchanged with different metal ions. Notably, these compounds do not contain any coordinated solvent molecules because the coordination sphere of the Ln3+ ion is fully occupied by chelating and bridging carboxylate oxygen atoms. Tunable colors and white-light emission can be achieved by encapsulating different molar ratios of Eu3+ and Tb3+ ions in the Gd framework through cation exchange. In addition, the Eu framework can act as a sensitive and selective luminescence sensor for both Fe2+ and Fe3+ .

Facile synthesis of a water stable 3D Eu-MOF showing high proton conductivity and its application as a sensitive luminescent sensor for Cu2+ ions

An oxalate-based multifunctional MOF material is synthesized with a quantitative yield by a simple aqueous solution reaction of cheap reactants.

Iridium-Based High-Sensitivity Oxygen Sensors and Photosensitizers with Ultralong Triplet Lifetimes.

The photophysics of a series of bichromophoric molecules featuring an intramolecular triplet energy transfer between a triscyclometalated iridium(III) complex and covalently linked organic group are studied. By systematically varying the energy gap (0.1-0.3 eV) between the donor (metal complex) and acceptor (pyrene unit), reversible triplet energy transfer processes with equilibrium constant K ranging from ca. 500 to 40 000 are established. Unique photophysical consequences of such large K values are observed. Because of the highly imbalanced forward and backward energy transfer rates, triplet excitons dominantly populate the acceptor moiety in the steady state, giving rise to ultralong luminescence lifetimes up to 1-4 ms. Because the triscyclometalated Ir and triplet pyrene groups both impart relatively small nonradiative energy loss, decent phosphorescence quantum yields (Φ = 0.1-0.6) are attained in spite of the exceptionally prolonged excited states. By virtue of such precious combination of long-lived triplet state and high Φ, these bichromophoric molecules can serve as highly sensitive luminescent sensors for detecting trace amount of O2 and as potent photosensitizers for producing singlet oxygen even under low-oxygen content conditions.

Controlled lanthanide-organic framework nanospheres as reversible and sensitive luminescent sensors for practical applications.

Two novel 3D frameworks were synthesized, and further nanosized to form nanospheres. Studies revealed that is the first MOF-based luminescent sensor for detecting cyclohexane, and this is also the first time that quick regeneration, high sensitivity, high yield, and easy nanocrystallization of MOF-based luminescent sensors have been simultaneously realized.

Sensitive luminescent paper-based sensor for the determination of gaseous hydrogen sulfide

Sampling and measurements without extraction steps.

Economically viable sensitive and selective luminescent sensor for the determination of Au(iii) in environmental samples

An economically viable luminescent sensor for Au(iii) (detection limit of 1.0 pg L−1) was described in this paper using the 2,5-dimercapto-1,3,4-thiadiazole (DMT) fluorophore.

Nanoscale metal-organic frameworks as highly sensitive luminescent sensors for Fe²⁺ in aqueous solution and living cells.

We report the exploration of fluorescent nanoscale metal-organic frameworks (nMOF-253s) for highly selective and sensitive detection of Fe(2+) ions in aqueous solution. Moreover, nMOF-253 of 50 nm is successfully applied in fluorescent bioimaging and intracellular Fe(2+) sensing in HeLa cells.

Conformal and Highly Luminescent Monolayers of Alq3 Prepared by Gas-Phase Molecular Layer Deposition

The gas-phase molecular layer deposition (MLD) of conformal and highly luminescent monolayers of tris(8-hydroxyquinolinato)aluminum (Alq3) is reported. The controlled formation of Alq3 monolayers is achieved for the first time by functionalization of the substrate with amino groups, which serve as initial docking sites for trimethyl aluminum (TMA) molecules binding datively to the amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting formation of highly luminescent Alq3 monolayers is afforded. The growth process and monolayer formation were studied and verified by in situ quartz crystal monitoring, optical emission and absorption spectroscopy, and X-ray photoelectron spectroscopy. The nature of the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces and porous structures with high surface areas, as demonstrated in this work for silica aerogels. The concept presented here paves the way to highly sensitive luminescent sensors and dye-sensitized metal oxides for future applications (e.g., in photocatalysis and solar cells).

Highly sensitive luminescent sensor for cyanide ion detection in aqueous solution based on PEG-coated ZnS nanoparticles

Using polyethylene glycol (PEG) coated ZnS nanoparticles (NPs), a novel and highly sensitive luminescent sensor for cyanide ion detection in aqueous solution has been presented. ZnS NPs have been used to develop efficient luminescence sensor which exhibits high reproducibility and stability with the lowest limit of detection of 1.29×10−6molL−1. The observed limit of detection of the fabricated sensor is ∼6 times lower than maximum value of cyanide permitted by United States Environmental Protection Agency for drinking water (7.69×10−6molL−1). The interfering studies show that the developed sensor possesses good selectivity for cyanide ion even in presence of other coexisting ions. Importantly, to the best of our knowledge, this is the first report which demonstrates the utilization of PEG- coated ZnS NPs for efficient luminescence sensor for cyanide ion detection in aqueous solution. This work demonstrates that rapidly synthesized ZnS NPs can be used to fabricate efficient luminescence sensor for cyanide ion detection.

A highly sensitive luminescent lectin sensor based on an α-d-mannose substituted Tb3+ antenna complex

Lectin-carbohydrate interactions are the basis of many biological processes and essentially they constitute the language through which intercellular communications are codified. Thus they represent powerful tools in the examination and interpretation of changes that occur on cell surfaces during both physiological and, more importantly, pathological events. The development of optical techniques that exploit the unique properties of luminescent lanthanoid metal complexes in the investigation of lectin-carbohydrate recognition can foster research in the field of ratiometric biosensing and disease detection. Here we report the synthesis of a Tb(3+)-DO3A complex (Tb⊂1) bearing an α-D-mannose residue and the related study of binding affinity with concanavalin A (Con A) labeled with rhodamine-B-isothiocyanate (RITC-Con A). Luminescence spectroscopy and dynamic studies show changes in emission spectra that can be ascribed to a luminescence resonance energy transfer (LRET) from Tb⊂1 (donor) to RITC-Con A (acceptor). The binding constant value between the two species was found to be one order of magnitude larger than those previously reported for similar types of recognition. To the best of our knowledge this is the first example of the use of a pre-organized luminescent lanthanoid complex in the study of carbohydrate-protein interactions by LRET.

A layer-structured Eu-MOF as a highly selective fluorescent probe for Fe3+ detection through a cation-exchange approach

A new series of lanthanide metal–organic frameworks, LnL (Ln = La, Y, Eu, Tb, and Gd), were prepared under hydrothermal conditions. The five compounds are all isostructural as confirmed by the analyses of single crystal and powder X-ray diffractions. The compounds exhibit layer-like structures with the [H2NMe2]+ cations being located in the interlayer channels, which can be easily replaced by a number of metal ions. Most interestingly, compound EuL performs as a rare example of a highly selective and sensitive luminescence sensor for Fe3+ ions based on total quenching of the Eu-luminescence via cation-exchange. The possible sensing mechanism was further explored in detail. Remarkably, it is the first Eu-MOF luminescent material to exhibit an excellent ability for the detection of Fe3+ ions in a biological system.

Design and evaluation of highly sensitive luminescent terbium sensor for hypochlorite in water

A novel terbium 2-methyl-benzoimidazole-5-carboxylic acid complex was prepared and incorporated into silica matrix (tetraethoxysilane) using a mild sol–gel technique. We then successfully fabricated a terbium luminescent xerogel, which maintained intense green emission even in pure water. The emission was rapidly (~1 s) quenched by ClO− (detection limit 10−5 M) but not NO3 −, CH3COO−, F−, Cl−, Br−, I−, CO3 −, and OH−. The selectivity appears to be due to the high vibrational energy of ClO− as well as its strong oxidation capability.

Development of a zinc ion-selective luminescent lanthanide chemosensor for biological applications.

Detection of chelatable zinc (Zn(2+)) in biological studies has attracted much attention recently, because chelatable Zn(2+) plays important roles in many biological systems. Lanthanide complexes (Eu(3+), Tb(3+), etc.) have excellent spectroscopic properties for biological applications, such as long luminescence lifetimes of the order of milliseconds, a large Stoke's shift of >200 nm, and high water solubility. Herein, we present the design and synthesis of a novel lanthanide sensor molecule, [Eu-7], for detecting Zn(2+). This europium (Eu(3+)) complex employs a quinolyl ligand as both a chromophore and an acceptor for Zn(2+). Upon addition of Zn(2+) to a solution of [Eu-7], the luminescence of Eu(3+) is strongly enhanced, with high selectivity for Zn(2+) over other biologically relevant metal cations. One of the important advantages of [Eu-7] is that this complex can be excited with longer excitation wavelengths (around 340 nm) as compared with previously reported Zn(2+)-sensitive luminescent lamthanide sensors, whose excitation wavelength is at too high an energy level for biological applications. The usefulness of [Eu-7] for monitoring Zn(2+) changes in living HeLa cells was confirmed. This novel Zn(2+)-selective luminescent lanthanide chemosensor [Eu-7]should be an excellent lead compound for the development of a range of novel luminescent lanthanide chemosensors for biological applications.

Luminescent pH sensing and DNA binding properties of a novel ruthenium(II) complex

A new Ru(II) complex, [Ru(bpy) 2(dhipH 3)](ClO 4) 2 (in which bpy=2,2 ′-bipyridine, dhipH 3=3,4-dihydroxy-imidado[4,5- f][1,10]-phenanthroline), was synthesized and characterized, and the pH effect on the emission spectra of the complex was studied. The interaction of the complex with calf thymus DNA was investigated by UV–visible and emission spectroscopy, and viscosity measurements. The results suggest that the complex acted as a sensitive luminescent pH sensor and a strong ct-DNA intercalator with an intrinsic binding constant of (4.0 ± 0.7) × 10 5 M −1 in buffered 50 mM NaCl.