A Dual-emitting Two-dimensional Nickel-based Metal-organic Framework Nanosheets: Eu3+/Ag+ Functionalization Synthesis and Ratiometric Sensing in Aqueous Solution

Using two-dimensional (2D) nickel-based metal organic framework (Ni-MOF) nanosheets as a matrix, Eu³⁺ and Ag⁺ were incorporated to synthesize Ag/Eu@Ni-MOF with double luminescence centers of Eu³⁺ ion (615 nm) and organic ligand (524 nm). And a ratiometric luminescence sensor is constructed based on Ag/Eu@Ni-MOF for sensitive detection of biothiols in aqueous solutions. The dual-emissive fluorescence properties can be tuned by changing the amounts of Ag⁺ ions doping. The results of temperature and pH effects on the fluorescence of Ag/Eu@Ni-MOF indicates that the Ag/Eu@Ni-MOF is a temperature-sensitive material and the fluorescence of Ag/Eu@Ni-MOF can keep stable over a wide pH range. Due to the binding of -SH in cysteine (Cys) and glutathione (GSH) with Ag⁺, the ligand luminescence was significantly inhibited by weakening the Ag?+?influence on the energy transfer process in the MOFs. Therefore, ratiometric fluorescent sensing of biomolecular thiols was realized based on the dual-emission Ag/Eu@Ni-MOF. More importantly, the fluorescence color change can be observed with naked eyes to realize visual detection. The ratiometric fluorescent sensor exhibits high performance for Cys and GSH detection with a wide linear range of 5-250 µM and a relatively low detection limit of 0.20 µM and 0.17 µM, respectively. Furthermore, the biothiols content in human serum was determined with satisfactory results. It proves the Ni-MOF nanosheets can be used as a stable matrix for construction luminescent MOFs for the first time, and validate the great potential of Ag/Eu@Ni-MOF as a ratiometric fluorescent probe for point-of-care testing (POCT) in disease diagnosis.

     

Selective Fluorimetric Recognition of Cesium Ion by 15-Crown-5-Anthracene

A selective fluorescent cesium optode on a chromoionophore consisting of anthracene covalently linked through an imine bond to a 15-crown-5 derivative has been reported. In the present system, 15-crown-5 derivative including anthracene was used a fluoroionophore. The fluorescence response mechanism is based on the photo-induced electron transfer (PET) from the lone pair of electrons of the nitrogen to the anthracene group and inhibition of PET system by cesium binding while increasing the fluorescence intensity. Emission intensity 15-crown-5 anthracene was measured at 500 nm with absorbance at 400 nm in CH₃CN–H₂O (1:1) media. The method shows a very good selectivity and sensitivity for cesium with respect to other cations such as K⁺, Na⁺ and Li⁺ with linear range and detection limit of 5.0 × 10⁻⁵ to 5.0 × 10⁻¹M and 3.0 × 10⁻⁶M respectively.     

Monitoring of the Proton Electrochemical Gradient in Reconstituted Vesicles: Quantitative Measurements of Both Transmembrane Potential and Intravesicular pH by Ratiometric Fluorescent Probes

Proteoliposomes carrying reconstituted yeast plasma membrane H⁺-ATPase in their lipid membrane or plasma membrane vesicles are model systems convenient for studying basic electrochemical processes involved in formation of the proton electrochemical gradient (Δμ_H ⁺) across the microbial or plant cell membrane. Δψ- and pH-sensitive fluorescent probes were used to monitor the gradients formed between inner and outer volume of the reconstituted vesicles. The Δψ-sensitive fluorescent ratiometric probe oxonol VI is suitable for quantitative measurements of inside-positive Δψ generated by the reconstituted H⁺-ATPase. Its Δψ response can be calibrated by the K⁺/valinomycin method and ratiometric mode of fluorescence measurements reduces undesirable artefacts. In situ pH-sensitive fluorescent probe pyranine was used for quantitative measurements of pH inside the proteoliposomes. Calibration of pH-sensitive fluorescence response of pyranine entrapped inside proteoliposomes was performed with several ionophores combined in order to deplete the gradients passively formed across the membrane. Presented model system offers a suitable tool for simultaneous monitoring of both components of the proton electrochemical gradient, Δψ and ΔpH. This approach should help in further understanding how their formation is interconnected on biomembranes and even how transport of other ions is combined to it.     

A Colorimetric and Ratiometric Fluorescent Chemosensor for Fluoride Based on Proton Transfer

N-Phenyl-N’-(3-quinolinyl)urea (1) has been developed as a highly selective colorimetric and ratiometric fluorescent chemosensor for fluoride ion based on a proton transfer mechanism. Evidences for the mechanism were provided by UV-vis and fluorescence titration and especially ¹H and ¹⁹F NMR experiments. The sensor gave the largest ratiometric fluorescent response reported so far (R_max/R_min = 2620) to fluoride. Taking H⁺ as the “recovering reagent”, the sensor can be reversibly “used” and “recovered” for several cycles with only a slight decay of the response ability.     

Organic Vapour Fluorescence Following Excitation into High Electronic Triplet States

Abstract

The fluorescence of anthracene vapors and its derivatives initiated by triplet-triplet excitation is observed. The quantum yield of inverce intersystem crossing of anthracene molecules is estimated (10^?2). The fluorescence initiated by triplet excitation is quenched by foreign pentane gas, thus permitting an estimation of the lifetime of highly excited triplet molecules.     

The Molecular Design of Fluorescent Sensors for Ionic Analytes

Molecular fluorescent sensors can be synthesized by covalently linking a photoactive fragment (e.g., anthracene) to a receptor subunit displaying affinity toward the envisaged substrate. The electron transfer process is the privileged signal transduction mechanism: redox active substrates (e.g., transition metals) typically release/uptake an electron to/from the proximate photoexcited fluorophore, the recognition being signaled through fluorescence quenching; redox inactive substrates (d⁰ and d¹⁰ metals, H⁺) deactivate an existing quenching relay (e.g., a tertiary nitrogen atom close to the fluorophore) and their recognition is signaled through fluorescence enhancement. An-ionic substrates can be conveniently recognized on the basis of the metal–ligand interaction: polyamine receptors containing the photophysically inactive Zn^IIion bind the carboxylate group. In the case of amino acids, , selectivity is improved when the receptor platform bears additional groups capable to interact specifically with the R substituent. If R is capable of transferring an electron to the nearby photoexcited fluorophore, the recognition is signaled through fluorescence quenching.     

A FRET Fluorescent Sensor for Ratiometric and Visual Detection of Sulfide Based on Carbon Dots and Silver Nanoclusters

In this work, the fluorescent sensor based on fluorescence resonance energy transfer (FRET) and electrostatic interaction (EI) was prepared for the ratiometric and visual detecting S^2–. The FRET fluorescent sensor consists of two fluorophores, with carbon dots (CDs) as energy donors and silver nanoclusters (Ag NCs) as acceptors. At 390 nm excitation, CDs and Ag NCs showed two well-separated peaks at 445 nm and 660 nm, separately. The existence of S^2– caused the red fluorescence at 660 nm to be quenched, whereas the blue fluorescence at 445 nm was restored, and the fluorescence color of the ratiometric sensor changed from pink to blue. It could be employed in ratiometric and visual detecting S^2–. The linear range of quantitative detection S^2– was 0.5–100 μM, and its detection limit was 0.35 μM. CDs-Ag NCs could be used for detecting S^2– in mineral water and tap water. The results showed that the FRET ratiometric fluorescent sensor exhibits good anti-interference and high selectivity for detecting S^2– in environmental water samples.

     

Fluorescence Study of the Relaxation Process in Excited Hetarylthiazole Cations

The absorption and fluorescence spectra of five cations protonated at the quinolyl nitrogen atom (IH⁺–VH⁺) and one ethylated (IEt⁺) cation were investigated. For these compounds (except VH⁺) both an anomalously large fluorescence Stokes shift (up to 238 nm) and a large short-wavelength fluorescence shift (up to 145 nm) at decreasing temperatures (down to 77 K) were observed. This is not the case for unprotonated molecules. The ground-state conjugation between quinolyl and another molecular fragment was found for II, IH⁺, IIH⁺, and IEt⁺. The relaxation process of excited cations is medium viscosity and temperature dependent. The experimental results are explained in terms of excited-state structural relaxation.     

An easily Prepared Fluorescent pH Probe Based on Dansyl

A novel fluorescent pH probe from dansyl chloride and thiosemicarbazide was easily prepared and fully characterized by ¹H NMR, ¹³C NMR, LC-MS, Infrared spectra and elemental analysis. The probe exhibited high selectivity and sensitivity to H⁺ with a pK _a value of 4.98. The fluorescence intensity at 510 nm quenched 99.5 % when the pH dropped from 10.88 to 1.98. In addition, the dansyl-based probe could respond quickly and reversibly to the pH variation and various common metal ions showed negligible interference. The recognition could be ascribed to the intramolecular charge transfer caused by the protonation of the nitrogen in the dimethylamino group.     

Perylene Diimide Appended with 8-Hydroxyquinoline for Ratiometric Detection of Cu2+ Ions and Metal Displacement Driven “Turn on” Cyanide Sensing

Perylene diimide (PDI) 3 and 4 appended with 8-hydroxyquinoline derivatives have been synthesized and their photophysical and spectroscopic properties have been experimentally determined. Moreover, PDIs 3 and 4 show ratiometric behavior to detect Cu²⁺ colorimetrically with visible color change from coral red to light pink, whereas 3 and 4 show “turn-off” behavior in fluorescence with lowest limit of detection 5?×?10^?7 M. The PDI 3 could be further utilized for ratiometric CN^? detection colorimetrically and as “turn-on” sensor for CN^? detection fluorometrically with lowest limit of detection 8?×?10^?6 M. The comparison of spectroscopic properties of PDI 1-4 highlights the importance of linking 8-hydroxyquinoline units on the PDI core at bay position for achieving Cu²⁺ recognition event into ratiometric signal.

Computational investigations into new fluorescence quenching process induced by complexation of alkali metal ion

A novel fluorescent switchable chemosensor 1 , which is composed of an anthracene‐modified calix[4]crown in the 1,3‐alternate conformation, was calculated by density functional theory and time‐dependent density functional theory method. Geometries, molecular orbitals and binding thermal energies were evaluated at the restricted hybrid Becke's three‐parameter exchange functional using 6‐31 G(d) basis set and relativistic effective core potentials. The metal–ligand and cation–π interactions were investigated acting as two main types of driving force. Our calculations clearly show that solvent effects strongly influence cation selectivity, and K⁺ selectivity is recovered when even a few waters of hydration are considered. The calculations indicate that because of the photoinduced electron transfer effect, the addition of alkali metal ions have hardly any effect on the fluorescence of ligand 1 under neutral or basic conditions. Also, the high selectivity of ligand 1 for K⁺ and Rb⁺, under acidic conditions, the complexed metal ion can result in ammonium ion deprotonation, which leads to quenching of fluorescence of 1 ?H⁺. Copyright © 2012 John Wiley & Sons, Ltd.     

A Novel Ratiometric Fluorescent Chemosensor for Cd2+

Novel ratiometric fluorescent chemosensor C7 was synthesized and characterized by UV–vis and fluorescence spectroscopy. C7 showed high sensitivity for Cd²⁺ among Na⁺, Mg²⁺, Cu²⁺, Pb²⁺, Ni²⁺, Fe³⁺, Zn²⁺, Ag⁺ Hg²⁺ and Cd²⁺ in ethanol.     

Low energy atomic collisions

The Schrödinger equation for the system H⁺-H developed in a previous paper is considered using new expansion functions for electronic states obtained from H₂ ⁺ molecular ion electronic eigenfunctions by a unitary transformation. These new functions have the advantage of remaining orthonormal at all internuclear separations and asymptotically becoming symmetrized atomic hydrogen states. Although they are eigenfunctions of the H₂ ⁺ hamiltonian only in the limit of large internuclear distance, the effect of the H₂ ⁺ hamiltonian on these functions is readily found.

Due to coupling which remains non-zero in the limit of large interproton distance, each independent formal solution of the H⁺-H equations involves more than one expansion state in this limit. These solutions may be expressed asymptotically as column vectors multiplied by incoming or outgoing spherical waves.

The formal theory of scattering as developed by Gell-Mann and Goldberger has been utilized along with the projection formalism of Feshbach to obtain the correct asymptotic form of the scattering wave function. The procedure employed involves formulating the problem in terms of two-potential scattering and requires application of renormalization techniques for treating level shifts produced by the infinite-ranged coupling. This asymptotic form may be used in imposing scattering boundary conditions on numerical solutions of coupled equations for H⁺-H scattering.

Finally, it is shown that one cannot interpret coefficients of all outgoing spherical waves as scattering amplitudes. In addition, new interference phenomena are found to result from the presence of the infinite-ranged coupling. The present formalism is shown to reduce to the usual perturbed stationary-states method in the approximation that the infinite-ranged coupling is neglected.     

Phase transformation in He+ and H+ ion irradiated type 304 stainless steel

γ (fcc)→α (bcc) phase transformation in type 304 stainless steel has been observed after irradiation of He⁺ and H⁺ ions up to fluence levels of 10¹⁷ and 10¹⁹ ions/cm², respectively. Depth selective conversion Mössbauer spectroscopy and surface-sensitive X-ray diffractometry were employed to study the effect of irradiation. It is shown that the amount of the ion induced phase is highly sensitive to the fluence, the ion species and depth from the surface. It is worth noting that H⁺ ion irradiation is rather ineffective in inducing the transformation.     

H+5团簇离子及其中性团簇产物H3和H4

报道了H⁺₅的实验结果.分析讨论了H⁺₅的 形成和分解途径.根据理论分析，以稳定的H⁺₃为核心与一个或多个氢分子结合可能形成稳定的H^{+_n氢团簇离子.另一方面，在高频离子源中, 有发生H+₃与H₂反应的条件.实 验中，从高频离子源引出的离子束被静电加速器加速，然后用9 关键词： +}₅团簇离子')" href="#">H⁺₅团簇离子 3中性团簇')" href="#">H₃中性团簇 4中性团簇')" href="#">H_{4中性团簇}     

Selective Ratiometric Fluorescence Detection of Acetate Based on a Novel Schiff Base Derivative

A ratiometric fluorescence and colorimetric probe based on 5,5′-methylene-bis-salicylaldehyde-p-nitrophenylhydrazone (1), which was characterized by ¹H NMR, mass spectrometer and elemental analysis, was prepared through Schiff base reaction. The probe exhibited visible color changes from yellow to purple upon interacting with acetate ion. Particularly, the compound showed ratiometric fluorescence response to acetate with significant blue shift about 150 nm from 410 nm to 560 nm. Thence, the probe 1 was a selective ratiometric fluorescence probe for acetate ion in DMSO solution.     

Gold‐Cluster‐Based Dual‐Emission Nanocomposite Film as Ratiometric Fluorescent Sensing Paper for Specific Metal Ion

A dual‐emission ratiometric fluorescent sensing film for metal ion detection is designed. This dual‐emission film is successfully prepared from chitosan, graphitic carbon nitride (g‐C₃N₄), and gold nanoclusters (Au NCs). Here, it is shown that the g‐C₃N₄ not only serves as the fluorescence emission source, but also enhances the mechanical and thermal stability of the film. Meanwhile, the Au NCs are adsorbed on the surface of chitosan film by the electrostatic interaction. The as‐prepared dual‐emission film can selectively detect Cu²⁺, leading to the quench of red fluorescence of Au NCs, whereas the blue fluorescence from g‐C₃N₄ persists. The ratio of the two fluorescence intensities depends on the Cu²⁺ concentration and the fluorescence color changes from orange red to yellow, cyan, and finally to blue with increasing Cu²⁺ concentration. Thus, the as‐prepared dual‐emission film can be worked as ratiometric sensing paper for Cu²⁺ detection. Furthermore, the film shows high sensitivity and selectivity, with low limit of detection (LOD) (10 ppb). It is observed that this novel gold‐cluster‐based dual‐emission ratiometric fluorescent sensing paper is an easy and convenient way for detecting metal ions. It is believed that this research work have created another avenue for the detection of metal ions in the environment.     

Electron capture and loss in the scattering of H+ from HOPG graphite

In this paper we report measurements of the positive (H⁺) and negative (H^?) ion fractions after H⁺ scattering from a highly oriented pyrolytic graphite (HOPG) surface. The experimental results show that for a fixed (large) exit angle the negative fraction is almost independent of the primary ion energy, while the positive fraction increases steadily. For a fixed incident energy, the H⁺ and H^? fractions show a complementary behavior with exit angle. A dynamical quantum mechanical calculation, based on the localized and extended features of the atom–surface interaction, allows us to understand many of the features of the experimental results.     

A Novel Hg<Superscript>2+</Superscript> Selective Ratiometric Fluorescent Chemodosimeter Based on an Intramolecular FRET Mechanism

A irreversible Hg²⁺ selective ratiometric fluorescence probe FR, a fluorescein fluorophore linked to a rhodamine B hydrazide by a thiourea spacer, was designed and synthesized. The developed probe FR exhibited great ratiometric fluorescence enhancement and remarkable yellow-magenta color change toward Hg²⁺ with excellent selectivity in aqueous acetone solution, and the ratiometric fluorescence response to Hg²⁺ was not interfered by other metal cations including Fe³⁺, Co²⁺, Ni²⁺, Cr³⁺, Zn²⁺, Pb²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Ba²⁺ and Mn²⁺. The linear range and the detection limit of this supposed ratiometric fluorescence method for Hg²⁺ were 0.0–10.0 × 10⁻⁶ and 5 × 10⁻⁸ M, respectively.     

A simple coumarin-based colorimetric and ratiometric chemosensor for acetate and a selective fluorescence turn-on probe for iodide

A novel colorimetric and ratiometric anion chemosensor bearing phenylhydrazone- coumarin moieties as recognition sites was rationally designed and synthesized. Upon addition of a series of anions to receptor R1 in 1:1 CH₃CN/H₂O, only the appearance of the solution of receptor R1 with acetate showed a color change from pale yellow to purple (bathochromic shift from 411 to 573 nm) which can be detected by the naked eye at parts per million. The probe R1 developed herein represents the rational design of a fluorescence turn-on probe for iodide, which is a notorious fluorescence quencher due to the heavy atom effect. The probe developed herein represents the fluorescence amplified probe for iodide.