A dual functional near infrared fluorescent probe based on the bodipy fluorophores for selective detection of copper and aluminum ions

A new near infrared (NIR) fluorescent 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dye with dual functionality was synthesized and characterized. The compound 1 responds to copper ion in NIR region with high selectivity through a photo-induced electron transfer process established between the substituted benzene group in the meso position and the BODIPY core when Cu²⁺ binds with the four oxygen atoms in the structure, and results in the quenching of the fluorescence. The response range to copper ions was from 10 to 50 μM, and other metal ions including Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Pb²⁺, Fe³⁺, Ag⁺, Hg²⁺, Co²⁺, Zn²⁺, Mn²⁺, Cd²⁺, Ni²⁺ and Al³⁺ had no interference. When excited at 520 nm, a new emission peak at 568 nm of compound 1 was used to detect Al³⁺ selectively from 30 μM to 110 μM without any interference from other metal ions including copper ions.     

High sensitive optode for selective determination of Ni based on the covalently immobilized thionine in agarose membrane

A novel Ni²⁺ optode was prepared by covalent immobilization of thionine, 3,7-diamine-5-phenothiazoniom thionineacetate, in a transparent agarose membrane. Influences of various experimental parameters on Ni²⁺ sensing, including the reaction time, the solution pH and the concentration of reagents were investigated. Under the optimized conditions, a linear response was obtained for Ni²⁺ concentrations ranging from 1.00 × 10⁻¹⁰ to 1.00 × 10⁻⁷ mol l⁻¹ with an R² value of 0.9985. The detection limit (3σ) of the method for Ni²⁺ was 9.30 × 10⁻¹¹ mol l⁻¹. The influence of several potentially interfering ions such as Ag⁺, Hg²⁺, Cd²⁺, Zn²⁺, Pb²⁺, Cu²⁺, Mn²⁺, Co³⁺, Cr³⁺, Al³⁺ and Fe³⁺ on the determination of Ni²⁺ was studied and no significant interference was observed. The membrane showed a good durability and short response time with no evidence of reagent leaching. The membrane was successfully applied for the determination of Ni²⁺ in environmental water samples.     

A highly selective triphenylamine-based indolylmethane derivatives as colorimetric and turn-off fluorimetric sensor toward Cu detection by deprotonation of secondary amines

A new triphenylamine-based fluorogenic probe bearing an indolylmethane unit (R1) was developed as a fluorescent chemosensor with high selectivity toward Cu²⁺ over other cations tested. The new probe R1 only sensed Cu²⁺ among heavy and transition metal (HTM) ions in CH₃CN/H₂O (70/30, v/v) solution. The capture of Cu²⁺ by the receptor resulted in deprotonation of the secondary amine conjugated to the triphenylamine, so that the electron-donation ability of the “N” atom would be greatly enhanced; thus sensor showed a 250 nm change in the new absorption band (from 291 nm to 541 nm) and a large colorimetric response, it also exhibited the large decrease in fluorescence intensity at 378 nm and affinity to Cu²⁺ over other cations such as Hg²⁺, Fe³⁺, Pb²⁺, Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Mn²⁺ make this compound a useful chemosensor for Cu²⁺ detection in CH₃CN/H₂O (70/30, v/v) mixture. The probe R1 (c = 1.0 × 10⁻⁶ M) displayed significant fluorescence change and colorimetric change upon addition of Cu²⁺ among the metal ions examined.     

Red emitting MTiO3 (M = Ca or Sr) phosphors doped with Eu3+ or Pr3+ with some cations as co-dopants

Ca (or Sr)TiO₃:Eu³⁺, M (Li⁺ or Na⁺ or K⁺) and CaTiO₃:Pr³⁺, M (Li⁺ or Na⁺ or Ag⁺ or K⁺ or Gd³⁺ or La³⁺) powders were prepared by combustion synthesis method and the samples were further heated to ～1000 °C to improve the crystallinity. The structure and morphology of materials were examined by X-ray diffraction (XRD) and a scanning electron microscopy (SEM). The morphologies of SrTiO₃:Eu³⁺, CaTiO₃:Eu³⁺ or CaTiO₃:Pr³⁺ powders co-doped with other metal ions were very similar. Small and coagulated particles of nearly cubical shapes with small size distribution having smooth and regular surface were formed. Photo-luminescence spectra of CaTiO₃:Pr³⁺ and co-doped either with Li⁺, Na⁺, K⁺, Ag⁺, La³⁺ or Gd³⁺ ions showed red emissions at 613 nm due to the ¹D₂ → ³H₄ transition of Pr³⁺. The variation of intensity of emission peak with different co-doping follows the order: K⁺ > Ag⁺ > Na⁺ > Li⁺ > La³⁺ > Gd³⁺. The characteristic emissions of CaTiO₃:Eu³⁺ lattices had strong emission at 614 and 620 nm for ⁵D₀ → ⁷F₂ with other weak transitions observed at 580, 592, 654, 705 nm for ⁵D₀ → ⁷F_n transitions where n = 0, 1, 3, 4 respectively in all host lattices. Photoluminescence intensity in SrTiO₃:Eu³⁺ is more than CaTiO₃:Eu³⁺ lattices. A remarkable increase of photoluminescence intensity (in ⁵D₀ → ⁷F₂ transition) was observed if co-doped with Li⁺ ions in CaTiO₃:Eu³⁺ and SrTiO3:Eu³⁺.     

Synthesis of Ag2Se nanomaterial by electrodeposition and its application as cataluminescence gas sensor material for carbon tetrachloride

In this paper, we presented a carbon tetrachloride gas sensor with strong cataluminescence response based on Ag₂Se nanomaterial, which was synthesized via the electrodeposition on the surface of Al foil by directly using a non-aqueous dimethyl sulfoxide (DMSO) solution with CH₃COOAg and SeCl₄. The deposited Ag₂Se material was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Then, the prepared Ag₂Se material along with the Al foil substrate was employed to design the carbon tetrachloride gas sensor. Under the optimized conditions, the present gas sensor exhibited a broad linear range of 0.9-228 μg mL⁻¹, with a limit of detection of 0.3 μg mL⁻¹ (S/N = 3). The proposed gas sensor showed good characteristics with high selectivity, fast response and long lifetime.     

Per-6-ammonium-β-cyclodextrin/p-nitrophenol complex as a colorimetric sensor for phosphate and pyrophosphate anions in water

Using per-6-ammonium-β-cyclodextrin (per-6-NH₃⁺-β-CD) as an anion binding site and p-nitrophenol as a spectroscopic probe, a colorimetric sensor is developed for phosphate and pyrophosphate anions in water. Per-6-NH₃⁺-β-CD forms a 1:2 inclusion complex with p-nitrophenol as characterized by NOESY and ESI-MS spectra and it undergoes a distinct color change from colorless to intense yellow upon exposure to phosphate or pyrophosphate anions over other anions including perchlorate, ATP²⁻, ADP²⁻ and AMP²⁻. The seven ammonium groups of 1, bind phosphate (characterized by ESI-MS) or pyrophosphate anions specifically by electrostatic interaction. This naked eye sensing is significant for very low concentration (5 × 10⁻⁵ M) of anion with 1:2 ratio of host and guest.     

Potentiometric solid-state sensor for DO measurement in water using sub-micron Cu0.4Ru3.4O7 + RuO2 sensing electrode

The dissolved oxygen (DO) sensing electrode (SE) concept utilizing sub-micron-sized ruthenium oxide (RuO₂), doped with other nanostructured oxides, has been extended to investigate the possibility of employing copper (II) oxide (Cu₂O) as a dopant in order to improve sensor's characteristics and meet long term antifouling needs for SEs. In this work, a thin-film SE made of RuO₂ was constructed on the alumina sensor substrate, and a range of dopants and their concentrations was added to it in order to optimize SE properties. The Cu₂O-doped RuO₂ SE had shown a linear response to DO between 0.5 and 8.0 ppm at various temperatures, with two sensitivity maxima of 47.4 and 46.0 mV per decade for Cu₂O concentrations of 10 and 20 mol%, respectively. The maximum sensitivity for Cu_0.4Ru_3.4O₇ + RuO₂-SE was obtained at a dopant concentration of 10%. Selectivity measurements revealed that the presence of Ca²⁺, Mg²⁺, Li⁺, Na⁺, NO³⁻, PO₄³⁻, SO₄²⁻, F⁻, K⁺ and Cl⁻ in the solution had no significant effect on the sensor's emf. The sensor allows overcoming the problem of an insufficient selectivity of semiconductor-based water sensors. It was also found that the doping of RuO₂-SE by Cu₂O allowed it to function at full capacity in a natural outdoor water body with no obvious effects of biofouling.     

A novel biosensor for detecting toxicity in water using sulfur-oxidizing bacteria

A novel toxicity detection methodology based on sulfur-oxidizing bacteria (SOB) has been developed for the rapid and reliable detection of toxic chemicals in water. The methodology exploits the ability of SOB to oxidize sulfur particles in the presence of oxygen to produce sulfuric acid according to the following equation: S + H₂O + 1.5O₂ → SO₄²⁻ + 2H⁺, ΔG°′ = −587.1 kJ/reaction. The reaction results in an increase in electrical conductivity (EC) and a decrease in pH as SOB convert insoluble sulfur particles to sulfate and protons. The proposed technique is validated using EC and pH data. Using a synthetic stream water (EC = 0.12 mS/cm and pH 7.2), the baseline steady-state EC and pH values were ∼1.0 mS/cm and ∼2.5 over 30 days of testing when hexavalent chromium (Cr⁶⁺) was not added to the system. When Cr⁶⁺ was added to the system, the effluent EC decreased and the pH increased due to inhibition of SOB. We found that the system can detect Cr⁶⁺ at a concentration of 5 ppb which is lower than any method to date.     

A new long-lasting phosphor Zr and Eu co-doped SrMg2(PO4)2

Zr⁴⁺- and Eu³⁺-codoped SrMg₂(PO₄)₂ phosphors were prepared by conventional solid-state reaction. Under the excitation of ultraviolet light, the emission spectra of Sr_0.95Eu_0.05Mg_2−2xZr_2xP₂O₈ (x = 0.0005-0.07) are composed of a broad emission band peaking at 500 nm from Zr⁴⁺-emission and the characteristic emission lines from the ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3 and 4) transitions of Eu³⁺ ions. These phosphors show the long-lasting phosphorescence. The emission color varies from red to white with increasing Zr⁴⁺-content. The white-light emission is realized in single-phase phosphor of Sr_0.95Eu_0.05Mg_2−2xZr_2xP₂O₈ (x = 0.07) by combining the Zr⁴⁺- and Eu³⁺-emission. The duration of the persistent luminescence of Sr_0.95Eu_0.05Mg_2−2xZr_2xP₂O₈ (x = 0.07) reaches nearly 1.5 h. The time at which the long-lasting phosphorescence intensity is 50% of its original value (T_0.5) is 410 s. The afterglow decay curves and the thermoluminescence spectra were measured to discuss this long-lasting phosphorescence phenomenon. The co-doped Zr⁴⁺ ions act as both the luminescence centers and trap-creating ions.     

A new acridine derivative as a highly selective ‘off-on’ fluorescence chemosensor for Cd in aqueous media

A new acridine fluoroionophore containing two diethanolamine ligands, 4,5-bis(N,N-di (2-hydroxyethyl)iminomethyl)acridine (BHIA), was designed and synthesized based on the fluorophore-spacer-receptor format. And its fluorescent sensing behavior towards metal ions was investigated in buffered aqueous media. The presence of Cd²⁺ induces the formation of a 1:1 ligand/metal complex at neutral pH, which exhibits enhanced emission at 454 nm. The fluorescence intensity is linear with the Cd²⁺ concentration in the range of 1.0 × 10⁻⁶ to 3.0 × 10⁻⁵ M (R = 0.9967). Experimental results show a low interference response towards other metal ions. The selective switch-on fluorescence response of BHIA to Cd²⁺ makes it suitable for sensing of Cd²⁺ in aqueous solution. The detection limit is 1.3 × 10⁻⁷ M. Moreover, the results indicated that BHIA was a reversible chemosensor for Cd²⁺, which makes it attractive for sensing applications.     

Electrochemical performances of B doped and undoped diamond-like carbon (DLC) films deposited by femtosecond pulsed laser ablation for heavy metal detection using square wave anodic stripping voltammetric (SWASV) technique

Pure diamond-like carbon (DLC) thin films and boron-doped DLC thin films have been deposited on silicon substrates using femtosecond pulsed laser. The amorphous carbon materials (DLC), have been deposited at room temperature by ablating graphite targets with an amplified Ti:sapphire laser of 800 nm wavelength and a pulse duration of 150 fs in high vacuum conditions. Doping with boron has been performed by ablating alternatively graphite and boron targets.In this study, the DLC films were used as working electrodes for the electrochemical detection of trace heavy metals namely, Cd²⁺, Pb²⁺, Ni²⁺ and Hg²⁺, by using square wave anodic stripping voltammetry (SWASV) technique. Four metals were detected at −1.3 V deposition potential, and 90 s deposition time. The DLC films have been characterized by multiwavelength Raman spectrometry and high resolution scanning electron microscopy. The effect of the boron doping on the electrochemical behavior has been shown. The a-C:B 8%/Si₃N₄ electrode gives the more sensitive detection. The four metals are detected simultaneously with a detection limit of 1 μg/L or 2 μg/L and a dynamic range from 1 or 2 to 25 μg/L for every metal, as presented in third table of this article. The different sensitivities obtained are 6.2, 20.0, 1.2 and 6.6 μA/ppb or μA μg⁻¹ L for Cd²⁺, Pb²⁺, Ni²⁺ and Hg²⁺, respectively.     

CaMoO4:RE3+,Yb3+,M+ phosphor with controlled morphology and color tunable upconversion

CaMoO₄:RE³⁺,Yb³⁺ (RE = Er, Ho, Tm) phosphors were successfully synthesized by a facile hydrothermal method. XRD patterns confirmed tetragonal structure under different RE³⁺ and M⁺ ions doping conditions. Particles shapes and sizes were confirmed by SEM and TEM analyses. Particles shape and size were well tuned by control of solution pH; spherical balls consisting of nano-grains at low pH of ∼2, rice grain shapes at moderate pH of ∼6, and thin flakes at higher pH of ∼12, were observed. Fine tunability of upconversion (UC) emission color was achieved by doping multiple RE³⁺ ions within a single CaMoO₄ host. Blue, green and orange upconverted emission were observed by doping Tm³⁺, Er³⁺ and Ho³⁺ in the CaMoO₄, respectively. Further, the emission colors were well tuned by the combination of Tm, Er and Ho ions and their concentrations. CaMoO₄:Tm³⁺,Ho³⁺,Yb³⁺ exhibited perfect white emission with well tunability from cool white to warm white colors. Substitution of part of Ca ions by M⁺ (M = Li, Na, K, Rb) ions affected the crystal field symmetry around RE³⁺ ions and hence changed the transition probabilities between their f–f transition levels, consequently intensified the UC intensities. The blue (Tm³⁺), green (Er³⁺), and orange (Ho³⁺) upconversion intensities of CaMoO₄:RE³⁺,Yb³⁺,0.10 K⁺ phosphors increased by 60, 50 and 40 folds compared to the unsubstituted analogues, respectively. The K substituted CaMoO₄:RE³⁺,Yb³⁺,K⁺ phosphors exhibited intense UC emissions visible by naked eye even pumped by less than 1 mW laser power and can have potential application in displays and variety of other applications.     

Novel pyrazoline-based selective fluorescent sensor for Zn in aqueous media

This work describes the preparation of a novel pyrazoline compound and the properties of its UV-vis absorption and fluorescence emission. Moreover, this compound can be used to determine Zn²⁺ ion with high selectivity and a low detection limit in the HEPES (20 mM HEPES, pH = 7.2, 50% (v/v) CH₃CN) buffer solution. This sensor forms a 1:1 complex with Zn²⁺ and shows a fluorescent enhancement by chelation enhanced fluorescence effect with good tolerance of other metal ions. In addition, this sensor is very sensitive with fluorometric detection limit of 0.12 μM.     

Sensing of lead ions using glutathione mediated end to end assembled gold nanorod chains

This communication reports the use of glutathione mediated self assembled chains of gold nanorods as new approach for the detection of Pb²⁺ ions. We were prompted to study the influence of metal ions by considering the role of glutathione as detoxification agent in the body. Additionally the ability of glutathione to complex with metal ions like lead (Pb²⁺) and mercury (Hg²⁺) is well known. We studied the interaction of different metal ions including Pb²⁺ with the end to end assembled chains of gold nanorods. Pb²⁺ was found to disassemble the chains to dimeric structures. High resolution transmission electron microscopy and dynamic light scattering were used to study the ensemble. A proportional reduction in the size of the assembly was observed between concentration ranges of 0.1-0.025 mM of Pb²⁺. Our results indicate that analyte induced disassembly is an attractive approach to the detection of environmentally relevant components such as Pb²⁺.     

Screening iodide anion with selective fluorescent chemosensor

An iodide-sensing, colormetric and selective fluorescent sensor N²,N⁶-bis(2-(p-nitro-benzamido)ethyl)pyridine-2,6-dicarboxamide, BBPCA, was reported. The recognition properties of BBPCA toward various anions were evaluated in THF/H₂O (4/1, v/v) solution by fluorescence emission and UV-vis absorption spectra. The results showed the BBPCA can be used to detect iodide ion based on intermolecular charge transfer (ICT) and heary atom quenching mechanism. The color changes of BBPCA solution from colorless to yellow and a red-shift in the absorption and emission spectra can be observed by adding iodide ions. But it showed no significant changes on the addition of other anions such as F⁻, Cl⁻, Br⁻, HCO₃⁻, NO₃⁻, CO₃²⁻.     

White and tunable light emission of Ho3+ and Pr3+ ions co-doped phosphate glasses

The Ho³⁺ and Pr³⁺ ions co-doped phosphate glasses were prepared by melt quenching procedure with the various composition of (70-x-y)P₂O₅ + 20SiO₂ + 10CaO + xHo₂O₃ + yPr₂O₃ (x = 0.4, 0.6, 0.8, 1.0 mol%, y = 0.6, 0.8, 1.0 mol%). The structural investigation (based on X-ray diffraction analysis) confirmed amorphous character of these glass materials. The optical properties were studied. The glass samples have strong absorption at 360 nm, and the excitation light at 360 nm can excite Ho³⁺ and Pr³⁺ ions very well, causing them to produce synergistic luminescence. The glass sample 68.8P₂O₅ + 20SiO₂ + 10CaO + 0.4Ho₂O₃ + 0.8Pr₂O₃ emits strong white light under 360 nm excitation. The chromaticity coordinate values are x = 0.3378, y = 0.3472 in white light region, and it has a moderate correlated color temperature (CCT) of 5277 K. Decay time data reveals that there is energy transfer from Pr³⁺ to Ho³⁺ ions. This glass will be a good material for white light and tunable light emitting.     

Tensor and border rank of certain classes of matrices and the fast evaluation of determinant inverse matrix and eigenvalues

The tensor rankA of the linear spaceA generated by the set of linearly independent matricesA ₁, A₂, …, A_p, is the least integert for wich there existt diadsu ^(r) v ^(r)τ, τ=1,2,...,t, such that . IfA=n+k,k≪n then some computational problems concerning matricesA∈A can be solyed fast. For example the parallel inversion of almost any nonsingular matrixA∈A costs 3 logn+0(log² k) steps with max(n ²+p (n+k), k² n+nk) processors, the evaluation of the determinant ofA can be performed by a parallel algorithm in logp+logn+0 (log² k) parallel steps and by a sequential algorithm inn(1+k ²)+p (n+k)+0 (k ³) multiplications. Analogous results hold to accomplish one step of bisection method, Newton's iterations method and shifted inverse power method applied toA−λB in order to compute the (generalized) eigenvalues provided thatA, B∈A. The same results hold if tensor rank is replaced by border rank. Applications to the case of banded Toeplitz matrices are shown. Dedicated to Professor S. Faedo on his 70th birthday Part of the results of this paper has been presented at the Oberwolfach Conference on Komplexitatstheorie, November 1983     

New fluorescent probes for mercury(II) with simple structure

Based on the protection reaction between ethanethiol and aldehyde, a novel fluorescent probe (2) for Hg²⁺ ions, with the simplest structure reported so far, was designed, which displayed high sensitivity and selectivity towards Hg²⁺ and Ag⁺ over other metal ions with detectable fluorescent signals, due to distinct deprotection reaction of dithioacetal. Compound 2 was further utilized to construct the chemical reaction-based conjugated polymer probes (P2 and P4) for Hg²⁺ ions. More importantly, the effect of the molecular weight of conjugated polymers on the sensitivity of the probes towards Hg²⁺ ions was carefully studied.     

Cu chemosensing behaviour of self-organized micro-array structures of a donor-acceptor bichromophoric compound anchored onto Ag nanoisland films

This work reports on the Cu²⁺ chemosensing behaviour of self-organized micro-array structures of a novel donor-acceptor bichromophoric compound anchored onto Ag nanoisland films. The system exhibits quenching of the fluorescence in the presence of Cu²⁺ ions, with detection range extending from 2 × 10⁻⁸ M up to 3 × 10⁻⁶ M and limit of detection (LOD) of 8 × 10⁻⁹ M. The quenching of fluorescence is accompanied by a quenching of SERS signal from the metal-organic structure, which is consistent with an electron transfer between the copper cation and the organic moiety. The self-organization property of the sensing complexes into micrometric arrays offers great potential for miniaturization and future development of Cu²⁺ detection systems based on real-time observation of fluorescence or SERS quenching by fluorescence microscopy or microRaman spectroscopy.     

Ratiometric fluorescent sensors for detecting zinc ions in aqueous solution and living cells with two-photon microscopy

We report two fluorescent Zn²⁺ sensors, AD1 and AD2. In aqueous solution, upon addition of Zn²⁺, AD1 only showed the enhancement on the fluorescence intensity, while AD2, acting as a ratiometric sensor, demonstrated the variations not only on the fluorescence intensity but also on the emission wavelengths. Both sensors exhibit high sensitivity (nM level) and selectivity for Zn²⁺ over Na⁺, K⁺, Mg²⁺, and Ca²⁺ at the millimolar level. Moreover, AD2 undergoes significant increase of the TPA cross sections (δ_max) at 840 nm by the Zn²⁺-coordination induced ICT enhancement. The laser scanning confocal microscopy experiments revealed that AD2 is cell-permeable and can indeed visualize the changes of intracellular Zn²⁺ in living cells through a ratiometric approach by utilizing two-photon excitation.