A highly Sensitive Turn-on Fluorescent Sensor for Ba<Superscript>2+</Superscript> Based on G-Quadruplexes

A G-quadruplex-based fluorescent biosensor for highly sensitive detection of barium ion (Ba²⁺) was constructed for the first time. In the absence of Ba²⁺, the G-quadruplex-specific fluorescence ligand N-methyl mesoporphyrin IX (NMM) remained weakly fluorescent when coexisted with a single-stranded G-quadruplex sequence AGRO100. Upon addition of Ba²⁺, AGRO100 was folded into G-quadruplex structures with the aid of Ba²⁺, which bound with NMM by stacking forces and significantly enhanced its fluorescence. The maximum fluorescence intensity of NMM was increased by ca. 22-fold in response to 1 μM Ba²⁺. This simple method exhibites a good linear relationship in the range of 0–600 nM with the detection limit of 4 nM. The detection method is turn-on, fast, economic, high in signal-to-noise ratio and free of participation of toxic organic solvents, demonstrating its great potential for on-site and real-time Ba²⁺ detection.     

Highly Selective and Anions Controlled Fluorescent Sensor for Hg<Superscript>2+</Superscript> in Aqueous Environment

A highly selective PET fluorescent sensor B1 for Hg²⁺ containing a BODIPY fluorophore and a NS₂O₂ penta-chelating receptor has been synthesized and characterized. Its absorption maximum wavelength (498 nm) and emission maximum wavelength (512 nm) are both in the visible range. The fluorescence quantum yields of the B1 and Hg²⁺-bound states of BHg1 are 0.008 and 0.58 in 70% aqueous ethanol solution, respectively. The pKa of 1.97 is the lowest in metal ions PET chemo sensors reported up till now as we know. Thus, B1 can detect the Hg²⁺ in a wide pH span, which indicates that it has more potential and further practical applications for biology and toxicology. Furthermore, BHg1 also displays response to some anions such as Cl⁻(Br⁻), , SCN⁻ and CH₃COO⁻, which is attributed to the significant coordinating ability of these anions to Hg²⁺.     

Organic Material Based Fluorescent Sensor for Hg<Superscript>2+</Superscript>: a Brief Review on Recent Development

Due to the deleterious effects of mercury on human health and natural ecosystems, high reactivity, non-degradability, extreme volatility and relative water and tissue solubility, it would consider as one of the most toxic environmental pollutants among the transition metals. In the present investigation, we have tried to summarized the several organic material based fluorescent sensor including rhodamine, boron-dipyrromethene (BODIPYs), thiourea, crown-ether, coumarine, squaraines, pyrene, imidazole, triazole, anthracene, dansyl, naphthalenedimide/ naphthalene/ naphthalimide, naphthyridine, iridium (III) complexes, polymeric materials, cyclodextrin, phthalic anhydride, indole, calix [4]arene, chromenone, 1,8-naphthalimides, lysine, styrylindolium, phenothiazine, thiocarbonyl quinacridone, oxadiazole, triphenylamine–triazines, tetraphenylethene, peptidyl and semicarbazone for the trace mercury detection in the aqueous, aqueous–organic and cellular media. The present review provides a brief look over the previous development in the organic material based fluorescent sensor for mercuric ion detection. Furthermore, the ligand-metal binding stoichiometry, binding/association/dissociation constants and the detection limit by the receptors have been particularly highlighted which might be useful for the future design and development of more sensitive and robust fluorescent chemosensor/chemodosimeter for the mercuric ion detection.

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A Dansyl-Rhodamine Ratiometric Fluorescent Probe for Hg<Superscript>2+</Superscript> Based on FRET Mechanism

Based on resonance energy transfer (FRET) from dansyl to rhodamine 101, a new fluorescent probe (compound 1) containing rhodamine 101 and a dansyl unit was synthesized for detecting Hg²⁺ through ratiometric sensing in DMSO aqueous solutions. This probe shows a fast, reversible and selective response toward Hg²⁺ in a wide pH range. Hg²⁺ induced ring-opening reactions of the spirolactam rhodamine moiety of 1, leading to the formation of fluorescent derivatives that can serve as the FRET acceptors. Very large stokes shift (220 nm) was observed in this case. About 97-fold increase in fluorescence intensity ratio was observed upon its binding with Hg²⁺.     

Polyol-thermal synthesis of silver nanowires for Hg<Superscript>2+</Superscript> sensing detection

This study demonstrates a facile but effective polyol-thermal reaction method for the synthesis of silver nanowires in autoclaves (160–180 °C). By this approach, the generated silver nanowires show an average diameter of ~40 nm and length up to tens of micrometers with a high yield and potential for large-scale production. To achieve shape- and size-controlled Ag nanowires, several experimental parameters were investigated and optimized, including surface controller(s), molar ratio of surfactant(s) to silver ions, temperature, and concentration of reactants. The structure and composition of silver nanowires were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) techniques. In particular, the twinned crystal structure observed in both spherical particles and nanowires was analyzed by HRTEM technique, and the possible formation and growth mechanisms were discussed. The optical property of the as-prepared product was measured by ultraviolet–visible (UV–vis) spectroscopy. The sensing detection of metal ions (e.g., Hg²⁺) using the obtained silver nanowires in aqueous media was finally investigated.     

A Turn-on Fluorescent Chemosensor for Zn<Superscript>2+</Superscript> Based on Quinoline in Aqueous Media

A simple “off-on fluorescence type” chemosensor 1 3-((2-(dimethylamino)ethyl)amino)-N-(quinolin-8-yl)propanamide has been synthesized for Zn²⁺. The receptor 1 comprises the quinoline moiety as fluorophore and the N,N^′-dimethylethane-1,2-diamine as a binding site. 1 showed a remarkable fluorescence enhancement in the presence of Zn²⁺ in aqueous solution. Importantly, the chemosensor 1 could be used to detect and quantify Zn²⁺ in water samples. In particular, this chemosensor could clearly distinguish Zn²⁺ from Cd²⁺. The binding properties of 1 with Zn²⁺ ions were investigated by UV-vis, fluorescence, electrospray ionization mass spectroscopy and ¹H NMR titration.     

Novel Turn-on Fluorescence Probes for Al<Superscript>3+</Superscript> Based on Conjugated Pyrazole Schiff Base

One novel turn-on fluorescence probe founded on conjugated pyrazole Schiff base for detecting Al³⁺ was invented. The UV–vis and fluorescence spectrometer were employed to explore optical properties of this probe. The results got from those experiments indicated that this fluorescence probe manifested excellent sensitivity and selectivity for Al³⁺ compared with other cations examined(Ag⁺, Co²⁺, Mg²⁺, Cu²⁺, Ni²⁺, Pb²⁺,and Zn²⁺). In addition, this probe displayed a more rapid response and remained stable between pH 6 and 9 by investigating the fluorescence intensity under different response time and various pH values. Remarkably, the detection limit for Al³⁺ could lower to 1.0×10^?9M. Therefore, the probe could be potentially applied to the environment for the detection of Al³⁺, and the availability in biological range of pH that could be further studied to make this probe apply to biological systems in the future.     

A Highly Sensitive and Selective Fluorescent Chemodosimeter for Hg<Superscript>2+</Superscript> in Neutral Aqueous Solution

A fluorescent assay of Hg²⁺ in neutral aqueous solution was developed using N-[p-(dimethylamino)benzamido]-N′-phenylthiourea (1). 1’s fluorogenic chemodosimetric behaviors towards various metal ions were studied and a high sensitivity as well as selectivity was achieved for Hg²⁺. It was because of a strongly fluorescent 1,3,4-oxadiazoles which was produced by the Hg²⁺ promoted desulfurization reaction. The spectra of ESI mass and IR provided evidences for this reaction. According to fluorescence titration, a good linear relationship ranging from 1.0 × 10⁻⁷ to 2.0 × 10⁻⁵ mol l⁻¹ was obtained with the limit of detection as 3.1 × 10⁻⁸ mol l⁻¹. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

One-pot synthesis of hybrid nanospheres with multistructure for selective adsorption of Hg<Superscript>2+</Superscript>

Novel complex nanospheres with core/shell structure for selective adsorption of Hg²⁺ have been prepared by a simple one-pot method. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed the nanospheres had perpendicularly thiol-functionalized mesoporous SiO₂ hybrid shell and Fe₃O₄@SiO₂ core (Fe₃O₄@nSiO₂@mSiO₂–SH). XRD patterns of as-synthesized nanospheres confirmed the observation of the SEM and TEM. The size of the nanospheres is about 100 nm. Based on the analysis of N₂ sorption–desorption isotherm, the surface area and pore volume of the adsorbent are 861 m²/g and 0.48 cm³/g, respectively. The saturation magnetization value for Fe₃O₄@nSiO₂@mSiO₂–SH is as high as 6.87 emu g⁻¹. The nanospheres showed more accessible active sites and high dispersibility in water, exhibited excellent performance for selective Hg²⁺ adsorption, had a stable structure, and could be recycled easily with magnet.     

A New Reactive 1,8-Naphthalimide Derivative for Highly Selective and Sensitive Detection of Hg<Superscript>2+</Superscript>

A 1,8-naphthalimide derivative with a reactive aliphatic hydroxyl was designed and synthesized as a fluorescent probe. Its structure was characterized by IR, ¹H NMR, ¹³C NMR, LC-MS and HPLC. The probe showed high selectivity and sensitivity to Hg²⁺ over other metal ions such as Pb²⁺, Na⁺, K⁺, Cd²⁺, Cr³⁺, Zn²⁺, Cu²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Fe²⁺, Co²⁺, Mn²⁺ and Mg²⁺ in MeCN/H₂O (15/85, v/v). The increase in fluorescence intensity was linearly proportional to the concentration of Hg²⁺ in the range of 18–40 μM with a detection limit of 1.38 × 10^?7 mol/L. The probe could work in a pH span of 4.3–9.0 and respond to Hg²⁺ quickly with strong anti-interference ability. Job’s plot suggested a 1:2 complex of the probe and Hg²⁺.     

A Colorimetric and Fluorescent Indicator for Hg<Superscript>2+</Superscript> Detection Based on Cinnamamide Group-Containing Rhodamine Derivative

A colorimetric and fluorescent indicator based on cinnamamide group-containing rhodamine derivative was synthesized for the detection of Hg²⁺. The rhodamine B and cinnamamide were connected via ethylenediamine as a bridging molecule through a condensation reaction to obtain a colorimetric and fluorescent indicator for the detection of Hg²⁺ in H₂O-EtOH (4:1, v/v). The indicator was excellent in the selectivity of Hg²⁺ and was almost unaffected by other common ions such as Na⁺, K⁺, Mg²⁺, Fe³⁺, Cu²⁺, Zn²⁺, Cr³⁺. The Hg²⁺-containing aqueous solution turned from colorless to red within 7 min after the addition of the indicator, and had an absorption peak at 564 nm in UV-vis, which implies a significant colorimetric phenomenon. Their characteristic peaks varied with the Hg²⁺ content, and they reached a linear relationship at low concentrations. The binding stoichiometry proved to be 1:1. The lowest detection limit was 4.1?×?10^?7 mol/L, ranging from acidic to neutral.     

Coumarin Based Fluorescent Probe for Colorimetric Detection of Fe<Superscript>3+</Superscript> and Fluorescence Turn On-Off Response of Zn<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A new coumarin based Schiff-base chemosensor-(E)-7-(((8-hydroxyquinolin-2-yl)methylene) amino)-4-methyl-2H-chromen-2-one (H ₁₁ L) was synthesized and evaluated as a colorimetric sensor for Fe³⁺ and fluorescence “turn on-off” response of Zn²⁺ and Cu²⁺ using absorption and fluorescence spectroscopy. Upon treatment with Fe³⁺ and Zn²⁺, the absorption intensity as well as the fluorescence emission intensity increases drastically compared to other common alkali, alkaline earth and transition metal ions, with a distinct color change which provide naked eye detection. Formation of 1:1 metal to ligand complex has been evaluated using Benesi-Hildebrand relation, Job’s plot analyses, ¹H NMR titration as well as ESI-Mass spectral analysis. The complex solution of H ₁₁ L with Zn²⁺ ion exhibited reversibility with EDTA and regenerate free ligand for further Zn²⁺ sensing. H ₁₁ L exhibits two INHIBIT logic gates with two different chemical inputs (i) Zn²⁺ (IN1) and Cu²⁺ (IN2) and (ii) Zn²⁺ (IN1) and EDTA (IN2) and the emission as output. Again, an IMPLICATION logic gate is obtained with Cu²⁺ and EDTA as chemical inputs and emission as output mode. Both free ligand as well as metal-complexes was optimized using density functional theory to interpret spectral properties. The corresponding energy difference between HOMO-LUMO energy gap for H ₁₁ L, H₁₁L-Zn²⁺ and H₁₁L-Cu²⁺ are 2.193, 1.834 and 0.172 eV, respectively.     

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 Dual-Target Fluorescent Probe with Response-Time Dependent Selectivity for Cd<Superscript>2+</Superscript> and Cu<Superscript>2+</Superscript>

A novel fluorescent probe (NT) was developed by merging 2-hydrazinylbenzothiazole with 2-hydroxy-1-naphthaldehyde for the detection of Cd²⁺ and Cu²⁺. The probe alone is almost nonfluorescent due to the isomerization of C=N in the excited state. The addition of Cd²⁺ can cause an immediate strong green fluorescence owing to the suppression of C=N isomerization by Cd²⁺-coordination. Furthermore, NT gives a delayed turn-on fluorescence response to Cu²⁺ although it is a vigorous fluorescence quencher, which was thanks to the inhibition of the electron transfer between excited fluorophore and paramagnetic Cu²⁺ by sulfur donor. Based on fluorescence spectra and ESI-MS analysis, the binding modes between NT and Cd²⁺/Cu²⁺ were proposed.     

Neutron transition densities for the 2<Superscript> + </Superscript>-8<Superscript> + </Superscript> multiplet of states in <Superscript>90</Superscript>Zr

Neutron transition densities for the 2 ⁺ -8 ⁺ levels in ⁹⁰Zr were extracted in the process of analyzing scattering at 400 MeV. They were compared with the calculated neutron transition densities and with the experimental proton transition densities. Radial distributions of the experimental neutron and proton transition densities for each state were found to be different.Received: 9 January 2004, Revised: 4 April 2004, Published online: 14 September 2004PACS: 25.40.Ep Inelastic proton scattering - 21.10.-k Properties of nuclei; nuclear energy levels     

Synthesis and Fluorescence Properties of Eu<Superscript>3+</Superscript>, Tb<Superscript>3+</Superscript> Complexes with Schiff Base Derivatives

Novel Schiff base ligands derived from N′-benzylidene-benzohydrazide (substituted by –H, ?CH₃, ?OCH₃, ?Cl) and 2-chloro-N-phenylacetamide were synthesized. The solid complexes of rare earth (Eu, Tb) nitrate with these Schiff base ligands were synthesized and characterized by elemental analysis, EDTA titrimetric analysis, thermal analysis, infrared spectra and UV–Vis spectra analysis. The fluorescence properties of rare earth (Eu, Tb) complexes in solid were studied. Under the excitation of ultraviolet light, these complexes exhibited characteristic emission of europium and terbium ions. The results showed that the ligand favored energy transfer to the emitting energy of Eu and Tb ions. Effects of different ligands on the fluorescence intensity of rare earth (Eu, Tb) complexes had been discussed. The electrochemical properties of rare earth (Eu, Tb) complexes were also investigated.     

Synthesis and Properties of a Novel FRET-Based Ratiometric Fluorescent Sensor for Cu<Superscript>2+</Superscript>

A novel FRET-based probe LS3 was designed and synthesized. As expected, it exhibited high selectivity and sensitivity for detecting Cu²⁺ over other commonly coexistent metal ions. The detection limit was measured to be 0.0423 μM for Cu²⁺, which can meet the selective requirements for practical application. In addition, the newly synthesized compound 3a/b have potential value of further synthesizing more analogous FRET-based probes.     

Effect of Sr<Superscript>2+</Superscript> ion substitution with trivalent ions (Sc<Superscript>3+</Superscript>, In<Superscript>3+</Superscript>, La<Superscript>3+</Superscript>, Bi<Superscript>3+</Superscript>) on its ferroelectric instability in SrTiO<Subscript>3</Subscript>

The vibration frequencies of unstable ferroelectric and antiferrodistortion modes and the dependences of the energy on the ion displacement amplitude have been calculated within the generalized Gordon-Kim model for distortions along eigenvectors of these modes in the mixed compounds Sr_{1 − x} A _x Ti_{1 − x} /₄□ _x/4O₃ and Sr_{1 − y} A _2y /₃□ _y/3TiO₃ (A = Sc³⁺, In³⁺, La³⁺, Bi³⁺; □ is the vacancy). To compensate an excess positive charge, vacancies are introduced into the Ti⁴⁺ or Sr²⁺ site. Calculations have been performed in the “daverage” crystal approximation for impurity concentrations of 0.25 and 0.50. To this end, a set of 40 atomic superlattices with various orderings of heterovalent ions Sr²⁺ and impurity A ³⁺ has been considered. It has been found that each impurity type, independently of charge balance, induces ferroelectric instabilities in doped compounds. In the case of doping with In³⁺ and La³⁺ for concentration x = 0.25, the possibility of rotating the polarization vector has been shown.     

Interaction of <Superscript>3</Superscript>He<Superscript>2+</Superscript> and Ar<Superscript>6+</Superscript> ions with acetylene,ethylene, and ethane molecules

Time-of-flight mass spectroscopy methods are employed for studying processes occurring during capture of electrons by ³He²⁺ and Ar⁶⁺ multiply charged ions with energy 6z keV (z is the ion charge) from C₂H _n molecules (n = 2, 4, 6) with different multiplicities of C-C bonds. Fragmentation schemes of the molecular ions formed in such processes are established from analysis of correlations of recording times for all fragment ions. The absolute values of the cross sections of capture of an electron and capture with ionization are measured, as well as the cross sections of formation of fragment ions in these processes. The absolute values of total capture cross sections for several electrons are determined.     

High-precision mass measurements of hydrogen-like <Superscript>24</Superscript>Mg<Superscript>11+</Superscript> and <Superscript>26</Superscript>Mg<Superscript>11+</Superscript> ions in a Penning trap

For the determination of the bound-electron g factor in hydrogen-like heavy ions the mass of the ion is needed at a relative uncertainty of at least 1 ppb. With the SMILETRAP Penning trap mass spectrometer at the Manne Siegbahn Laboratory in Stockholm several mass measurements of ions with even-even nuclei at this level of precision have been performed so far, exploiting the fact that the mass precision increases linearly with the ion charge. Measurements of masses of the hydrogen-like ions of the two Mg-isotopes ²⁴Mg and ²⁶Mg are reported. The masses of the hydrogen-like ions are 23.979011054(14) u and 25.976562354(34) u, corresponding to the atomic masses 23.985041690(14) u and 25.982592986(34) u, respectively. The possibility to use these two isotopes for the first observation of an isotope effect in the bound-electron g factor in hydrogen-like heavy ions is discussed.