Fluorescence Of Tb3 Research Articles

Copper-doped Lanthanide Coordination Polymers as Luminescent Nanoenzyme for Ratiometric Sensing of H2O2 and Glutathione.

Design and fabrication of integrated multifunctional probes with intrinsic catalytic and detection abilities is of great importance to simplify the operation in biosensing application with high sensitivity. Herein, dual-emitting lanthanide coordination polymers (Ln-CPs) were facilely prepared by self-assembly of guanine diphosphate (GDP), terephthalic acid (TA), Tb3+ and Cu2+ designated as Tb/Cu-GDP/TA CPs. The doped Cu2+ endowed CPs with obviously enhanced peroxidase mimicking activity compared with free Cu2+. In the presence of H2O2, the probe catalyzed the oxidation of TA generating a new blue fluorescent product, while the fluorescence of Tb3+ decreased simultaneously. Therefore, a new sensitive ratiometric fluorescent sensor for H2O2 has been developed with a good linear range from 0.01 to 300μM and limit of 1.62nM. Moreover, the proposed platform could be extended to GSH ratiometric assay in the presence of H2O2, and interestingly, the detection performance could be easily adjusted by adding different concentration of H2O2. This work will facilitate the development of luminescent nanoenzymes based on Ln-CPs to construct the simple ratiomatric sensing platform.

Tb3+-nucleic acid probe-based label-free and rapid detection of mercury pollution in food

Mercury is a threatening pollutant in food, herein, we developed a Tb3+-nucleic acid probe-based label-free assay for mix-and-read, rapid detection of mercury pollution. The assay utilized the feature of light-up fluorescence of terbium ions (Tb3+) via binding with single-strand DNA. Mercury ion, Hg2+ induced thymine (T)-rich DNA strand to form a double-strand structure (T-Hg2+-T), thus leading to fluorescence reduction. Based on the principle, Hg2+ can be quantified based on the fluorescence of Tb3+, the limit of detection was 0.0689 μmol/L and the linear range was 0.16 μmol/L. Due to the specificity of T-Hg2+-T artificial base pair, the assay could distinguish Hg2+ from other metal ions. The recovery rate was ranged in 98.71 %101.34 % for detecting mercury pollution in three food samples. The assay is low-cost, separation-free and mix-to-read, thus was a competitive tool for detection of mercury pollution to ensure food safety.

A core–shell structure ratiometric fluorescent probe based on carbon dots and Tb3+ for the detection of anthrax biomarker

A novel core–shell structure ratiometric fluorescent probe was developed, which can selectively and sensitively detect 2,6-dipicolinic acid (DPA) as an anthrax biomarker. Carbon dots (CDs) was embedded into SiO2 nanoparticles, which was acted as an internal reference signal. Tb3+ with green emission was connected to the carboxyl functionalized SiO2, which was acted as a responsive signal. With the addition of DPA, the emission of CDs at 340 nm was unchanged, while the fluorescence of Tb3+ at 544 nm was enhanced by the antenna effect. In the concentration range of 0.1–2 μM, the fluorescence intensity ratio of I544/I340 showed a good linear relationship with the concentration of DPA, and the limit of detection (LOD) was 10.2 nM. In addition, the dual-emission probe showed an obvious fluorescence color change from colourless to green with increasing DPA under UV light, which enabled visual detection.

A single-stranded DNA-based and terbium (III) fluorescent probe for facile and rapid detection of mercury (II)

Hg2+, as a highly dangerous pollutant, seriously affects public health and food safety. In this work, a biosensor based on single-stranded DNA and Tb3+ fluorescent probe was constructed for facile and rapid detection of Hg2+. The detection method only needs one DNA strand, which consists of two parts: the G-rich sequence is the Tb3+ luminescent antenna ligand and the T-rich sequence is the Hg2+ recognition probe. Free mercury-specific DNA (MSD) in an aqueous solution could significantly enhance Tb3+ luminescence. Upon the addition of Hg2+, the conformation of MSD will switch from the free random coil structure to the hairpin structure. Thus, Tb3+ was released and the fluorescence of Tb3+ was decreased. After condition optimization, the change of fluorescence intensity was proportional to the logarithmic concentration of Hg2+ from 0.01 to 10 μM with a detection limit of 1.9 nM. In addition, the detection results of Hg2+ in real samples were satisfactory. The designed fluorescent probe has great advantages in simplicity and functionality and has great development potential in food safety and environmental pollution.

Rare-Earth hydroxide nanosheets based ratio fluorescence nanoprobe for dipicolinic acid detection

We demonstrate a novel ratio fluorescence nanoprobe for dipicolinic acid (DPA) as an anthrax biomarker based on layered rare-earth hydroxide (LRH). 3-Amino-benzenesulfonic acid (AS) was intercalated into layered terbium hydroxide to form composite and then delaminated into nanosheets in formamide. The monolayer nanosheets were beneficial to expose the Ln3+ luminescence centers to the environment more completely, contributing a high sensitive detection to the environment. With the increase of DPA concentration, the emission intensity of AS kept constant which worked as a stable internal reference, while the fluorescence of Tb3+ was enhanced obviously due to the antenna effect. In the 0.05–5.0 μM concentration range, the I544/I360 fluorescence ratio changed with the DPA concentration, which exhibited a good linear relationship (R2 = 0.999) and an ultralow detection limit of 3.8 nM. In addition, the probe showed high selectivity and sensitivity to the DPA detection as an anthrax biomarker, which can be applied in real tap water with good performances. This work could extend the applications of LRH nanosheets in detection and offer an extremely effective and easy technique for detecting DPA.

Polyvinylpyrrolidone Nanofibers Encapsulating an Anhydrous Preparation of Fluorescent SiO₂⁻Tb3+ Nanoparticles.

A novel anhydrous preparation of silica (SiO2)-encapsulated terbium (Tb3+) complex nanoparticles has been investigated. The SiO2-Tb3+ nanoparticles are incorporated in electrospun polyvinylpyrrolidone hybrid nanofibers. Transmission electron microscopy confirms that Tb3+ complexes are uniformly and stably encapsulated in or carried by nanosilica. The influence of pH on the fluorescence of Tb3+ complexes is discussed. The properties, composition, structure, and luminescence of the resulting SiO2–Tb3+ hybrid nanoparticles are investigated in detail. There is an increase in the fluorescence lifetime of SiO2–Tb3+ nanoparticles and SiO2–Tb3+/polyvinylpyrrolidone (PVP) hybrid nanofibers compared with the pure Tb3+ complexes. Due to the enhanced optical properties, the fluorescent hybrid nanofibers have potential applications as photonic and photoluminescent materials.

Ratiometric fluorescence sensing of Fe2+/3+ by carbon dots doped lanthanide coordination polymers

In this work, we proposed a ratiomatric fluorescent strategy for sensing Fe2+ by using the carbon dots (CDs) doped lanthanide coordination polymers (Ln-CPs). Herein, the Ln-CPs were prepared by self-assemble of adenosine monophosphate (AMP) with Tb3+ (AMP-Tb) through coordination reaction, and CDs were encapsulated during the assembly process as guest materials. A cofactor, phenanthroline (Phen), could incorporate into the CDs@AMP-Tb, and strongly sensitized the luminescence of Tb3+ through energy transfer. Therefore, the obtained CDs@AMP/Phen-Tb could emit dual fluorescence signals. One is the characteristic emission of Tb3+, which could be specifically quenched by Fe2+ due to the high affinity between Phen and Fe2+. Another is originated from CDs encapsulated in Ln-CPs, which did not change in the presence of Fe2+. Subsequently, CDs@AMP/Phen-Tb was chosen as the ratiomatric fluorescent probe for sensing Fe2+, where the fluorescence of Tb3+ was quenched serving as the reporter, while that of CDs remained constant serving as the internal control for self-calibration. In addition, with the help of a reducing agent, which can reduce Fe3+ to Fe2+ efficiently, the proposed method can also be applied in selective detection Fe3+. By taking advantage of the unique property of Ln-CPs, the proposed strategy promises flexibility for designing of a series of ratiometric fluorescent sensors and expanded in practical applications.

Ratiometric fluorescent detection of superoxide anion with polystyrene@nanoscale coordination polymers

A novel ratio fluorescence sensor for superoxide anion (O2−) detection was developed with suffocated polystyrene nanoparticles (PS-SO3H)@terbium (Tb)/guanine (G) nanoscale coordination polymers (PS-SO3H@Tb/G NCPs). The abundant sulfonyl of PS-SO3H are served as binding points for the spontaneous self-assembly of Tb3+ and G on the surface of PS-SO3H to form PS-SO3H@Tb/G NCPs sensor. The formation of PS-SO3H@Tb/G NCPs was verified by detailed characterization (i.e., scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and fluorescence emission spectroscopy). The obtained senor exhibits the characteristic fluorescence emission of Tb3+ and PS-SO3H. The fluorescence of PS-SO3H is slightly weaken as a reference and the fluorescence of Tb3+ is largely weaken in the presence of O2−, resulting in ratiometric fluorescent sensor toward the O2−. The ratio of fluorescence density linearly decreases with the increasing of O2− concentration in the range of 10.12 nM-6.0μM with a detection limit as low as 3.4nM. This ratiometric fluorescent sensor also shows good selectivity toward O2−.

An integrated logic system for time-resolved fluorescent “turn-on” detection of cysteine and histidine base on terbium (III) coordination polymer–copper (II) ensemble

Cysteine (Cys) and histidine (His) both play indispensable roles in many important biological activities. An enhanced Cys level can result in Alzheimer's and cardiovascular diseases. Likewise, His plays a significant role in the growth and repair of tissues as well as in controlling the transmission of metal elements in biological bases. Therefore, it is meaningful to detect Cys and His simultaneously. In this work, a novel terbium (III) coordination polymer–Cu (II) ensemble (Tb3+/GMP-Cu2+) was proposed. Guanosine monophosphate (GMP) can self-assemble with Tb3+ to form a supramolecular Tb3+ coordination polymer (Tb3+/GMP), which can be suited as a time-resolved probe. The fluorescence of Tb3+/GMP would be quenched upon the addition of Cu2+, and then the fluorescence of the as-prepared Tb3+/GMP-Cu2+ ensemble would be restored again in the presence of Cys or His. By incorporating N-Ethylmaleimide and Ni2+ as masking agents, Tb3+/GMP-Cu2+ was further exploited as an integrated logic system and a specific time-resolved fluorescent “turn-on” assay for simultaneously sensing His and Cys was designed. Meanwhile it can also be used in plasma samples, showing great potential to meet the need of practical application.

Lanthanide based dual-emission fluorescent probe for detection of mercury (II) in milk

It is highly desirable to develop a simple and sensitive method for Hg2+ detection because of the dangerous nature of Hg2+. In this work, we prepared a dual-emission fluorescent probe for Hg2+ detection by combining two lanthanide chelates with different emission wavelengths. Green-emitting terbium (Tb3+) chelates as reference signals were embedded into SiO2 nanoparticles and red-emitting europium (Eu3+) chelates as response units were covalently linked to the surface of silica shell. Upon the addition of Hg2+, the fluorescence of Eu3+ chelates can be selectively quenched, while the fluorescence of Tb3+ chelates remained unchanged. As a kind of Hg2+ nanosensor, the dual-emission fluorescent probe exhibited excellent selectivity to Hg2+ and high sensitivity up to 7.07nM detection limit. The Hg2+ levels in drinking water and milk samples were determined by using the dual-emission fluorescent probe with satisfied recovery. Additionally, our probe has a long enough fluorescence lifetime, which can avoid the interference from autofluorescence of the biological samples. We envision that the proposed probe could find great potential applications for ultrasensitive time-resolved fluorometric assays and biomedical imaging in the future.

Crystal structures, luminescent properties and thermal decomposition kinetics of some binuclear lanthanide complexes with 2,3-dichlorobenzoic acid anion and 2,2′-bipyridine

Some binuclear lanthanide complexes with the general formula [Ln(2,3-DClBA)3bipy]2 (Ln = Sm(1), Eu(2), Tb(3), Dy(4), and Ho(5); 2,3-DClBA = 2,3-dichlorobenzoate; bipy = 2,2′-bipyridine) were synthesized and characterized by elemental analysis, molar conductance, infrared, ultraviolet, luminescent spectroscopy, thermogravimetry, and different thermogravimetry (TG–DTG) techniques. The single crystals of the complexes have been obtained except the complex 2 and their structures have been determined by single-crystal X-ray diffraction. The four complexes are isostructural and the rare earth ions are all nine coordinated. The two rare earth ions in each complex are linked by two bridging bidentate and two chelating-bridging tridentate carboxylate groups. Under ultraviolet light excitation, the europium and terbium complexes exhibited characteristic red fluorescence of Eu3+ ion and green fluorescence of Tb3+ ion at room temperature. The non-isothermal kinetics was investigated by using the integral isoconversional non-linear (NL-INT) and the Popescu methods. The mechanism functions of the first decomposition step of the complexes 3–5 were determined. Meanwhile, the thermodynamic parameters (ΔG ≠ , ΔH ≠, and ΔS ≠) at DTG peak temperatures were also calculated.

Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

In Tris‐HCl buffer (pH=7.43), Tb3+ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb3+. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10−7∼2.5×10−5mol/L, and the detection limit is 5.5×10−9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.

No entry for TAT(44–57) into liposomes and intact MDCK cells: novel approach to study membrane permeation of cell-penetrating peptides

Cell penetrating peptides (CPPs) have been postulated to carry macromolecules across cell plasma membranes without the need of receptors, transporters, endocytosis or any energy-consuming mechanism.We developed an assay to study lipid bilayer permeation of CPPs. HIV-1 TAT peptides were conjugated to N-(4-carboxy-3-hydroxyphenyl)maleimide (SAM) and incubated with Tb3+-containing liposomes. Upon chelation of Tb3+ by an aromatic carboxylic acid, the fluorescence of Tb3+ increases many fold. The CPP TAT(44–57)-SAM and TAT(37–53)-SAM, as a negative control, were unable to enter liposomes consisting of phosphatidylcholine (PC) or a mix of PC, negatively charged lipids and cholesterol.In parallel, cell entry of fluorescein-labeled TAT peptides was studied using confocal laser scanning microscopy (CLSM). TAT(44–57)-fluorescein did not enter Madin Darby canine kidney (MDCK) cells with intact plasma membranes but accumulated at their basal side. Only cells with impaired plasma membranes, as identified by nuclear staining with ethidium homodimer-1 (EthD-1), showed accumulation of TAT(44–57).Our findings change the perspectives of the potential use of TAT peptides as carriers for intracellular targeting. SAM- and fluorescein-labeled TAT(44–57) cannot penetrate lipid bilayers and intact plasma membranes of MDCK cells, respectively.

Theory of donor fluorescence governed by discrete energy transfers between rare-earth ions in glasses

We have derived the macroscopic response theory of donor fluorescence in rare-earth glasses by calculating a statistical expectation of individual energy transfers from energy donors to energy acceptors. The distribution functions of energy acceptors were classified by their distances of the first-nearest neighbor through the fourth-nearest neighbor to donors. The role of the individual energy transfers was found to be important for the nonlinearity of the donor fluorescence. The experimental results of donor fluorescence of Tb3+ ions were well fitted both to the nonexponential decays caused by pulsed excitation and to the concentration quenching of fluorescence with a coupled parameter set of a critical transfer distance and an energy relaxation rate of the acceptor. The energy transfer depended closely on r-8 for the distance r from Tb3+ to Nd3+ ions or among Tb3+ ions in glasses. In this model the energy transfers from a donor to the first- and the second-nearest-neighbor acceptors was enough to explain the experimental results.

Temperature deactivation of excited Tb3+ in the presence of 1,2-dioxetane in acetonitrile

Quenching the fluorescence (FL) of terbium perchlorate by 2,2′-adamantane-2,2′-dioxide (1) was shown to have a chemical character and was caused by the formation of the [1...Tb3+] complex. The dependence of the lifetime (τ) of FL of Tb*3+ in acetonitrile on the temperature and concentration of1 has been studied. The temperature dependence of τ is caused by a rearrangement of the inner sphere of the aquasolvate complexes of Tb3+, which leads to the replacement of H2O with MeCN and1. The energy of replacing the H2O molecule in the inner sphere of complexes with a solvent molecule has been calculated.

Study on the Fluorescence System of Tb-ATP-Phen for the Determination of ATP

Abstract It was found that ATP could form a ternary complex with Tb3+ and Phen, which can emit the characteristic fluorescence of Tb3+. The experiment showed that the fluorescence intensity of the system was maxmium in the following conditions: pH of the solution is 7.2, the concentrations of Tb3+ and phenanthroline (Phen) are 2.0×10-5mol.L-1 and 2.0 × 10-4mol.L-1, respectively. At the optimum conditions, a linear relationship is obtained between the fluorescence intensity and ATP concentration in the range of 1.0×10-6—1.0×10-5mol.L-1. Traces of ATP in drugs (ATP disodium salt tablets) can be determined using the standard addition method. The luminescence mechanism of the system was discussed.

EFFECTS ON PRESSURE ON THE SPECTRA, LIFETIMES AND ENERGY TRANSFER OF Eu P5O14, Tb P5O14 AND Eu1-xTbxP5O14

The effect of pressure (up to 210 kbars) on the fluorescence of Tb3+ and Eu3+ ions in the mixed single crystals Tbx Eu1-x P5O14 is investigated. A strong Tb3+ → Eu3+ energy transfer is observed and the pressure dependence of this transfer is shown to be governed by diffusion-limited relaxation. Using time-resolved spectroscopy under high pressure this energy transfer is found to be faster with pressure.

Cubic Crystal-Field Energy Levels, Tb^3+: CaF_2(I)

Empirically derived cubic-field energy-level schemes of fluorescence of Tb3+ in CaF2(I) are analyzed and compared with those theoretically derived. The x values for the 5D4, 7F3, 7F4, and 7F5 states are derived to the first order for a weak cubic field, and the energies are calculated to the second order. The second-order energies when added to the theoretical first-order levels of Lea, Leask, and Wolf at the calculated x values give energy levels in agreement with the empirical schemes to within 10%, substantiating the cubic crystal-field assignment for this crystal. The ratio of fourth- to sixth-order cubic crystal-field parameters (A4〈r4〉/A6〈r6〉) is found to be −11.5.