A Pyrene-based Highly Selective Turn-on Fluorescent Sensor for Copper(II) Ion and its Application in Live Cell Imaging

A new pyrene derivative (chemosensor 1) containing a picolinohydrazide moiety exhibits high selectivity for Cu²⁺ ion detection in mixed aqueous media (CH₃OH:H₂O = 7:3). Significant fluorescence enhancement was observed with chemosensor 1 in the presence of Cu²⁺. However, the metal ions Ag⁺, Ca²⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe²⁺, Fe³⁺, Hg²⁺, K⁺, Mg²⁺, Mn²⁺, Ni²⁺, Pb²⁺, and Zn²⁺ produced only minor changes in fluorescence for the system. The apparent association constant (K _a) of Cu²⁺ binding in chemosensor 1 was found to be 2.75*10³ M⁻¹. The maximum fluorescence enhancement caused by Cu²⁺ binding in chemosensor 1 was observed over the pH range 5–8. Moreover, by means of fluorescence microscopy experiments, it is demonstrated that 1 can be used as a fluorescent probe for detecting Cu²⁺ in living cells.     

Spectroscopic properties of Nd<Superscript>3+</Superscript>:CaNb<Subscript>2</Subscript>O<Subscript>6</Subscript> crystal

The absorption spectra, fluorescence spectrum and fluorescence decay curve of Nd³⁺ ions in CaNb₂O₆ crystal were measured at room temperature. The peak absorption cross section was calculated to be 6.202×10⁻²⁰ cm² with a broad FWHM of 7 nm at 808 nm for E//a light polarization. The spectroscopic parameters of Nd³⁺ ions in CaNb₂O₆ crystal have been investigated based on Judd-Ofelt theory. The parameters of the line strengths Ω _t are Ω ₂=5.321×10⁻²⁰ cm²,Ω ₄=1.734×10⁻²⁰ cm²,Ω ₆=2.889×10⁻²⁰ cm². The radiative lifetime, the fluorescence lifetime and the quantum efficiency are 167 μs, 152 μs and 91%, respectively. The fluorescence branch ratios are calculated to be β ₁=36.03%,β ₂=52.29%,β ₃=11.15%,β ₄=0.533%. The emission cross section at 1062 nm is 9.87×10⁻²⁰ cm².     

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.     

Studies on Interaction of Norfloxacin,Cu<Superscript>2+</Superscript>, and DNA by Spectral Methods

The interactions of norfloxacin (NFA), DNA, and Cu²⁺ are studied by fluorescence and UV-spectra method. According to the experimental results, it can be concluded that NFA can form a steady binary complex with Cu²⁺. There is a linear relationship between the Fluorescence intensity of the norfloxacin–Cu²⁺–DNA system and the concentration of DNA. And when the concentration of the NFA is 1.95×10⁻⁵ mol L⁻¹, they possess a good linearity in the concentration of DNA ranged from 4.7×10⁻⁶ to 2.8×10⁻⁵ mol L⁻¹.It is a good method due to the high sensitivity and selectivity.     

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⁺.     

A New Fluorescent Chemosensor Detecting Co<Superscript>2+</Superscript> and K<Superscript>+</Superscript> in DMF Buffered Solution

A new fluorescent chemosensor 2-(2-thiophene)imidazo [4,5,f]-1,10-phenanthroline (L) was prepared and characterized. By adding univalent or divalent metal ions such as Na⁺, K⁺, Mg²⁺, Ba²⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺ and Hg²⁺ ions into the solution of L in DMF under buffered conditions with the working pH ranging from 7.0 to 8.0, we found that L could be used to detect K⁺ ratiometricly and it could also be applied to sense Co²⁺ with the phenomenon of fluorescence quenching of L. While the response behavior of L was not discernibly affected by other examined metal ions.     

Study on the Binding Behavior of Lysozyme with Cephalosporin Analogues by Fluorescence Spectroscopy

It was first found that the intrinsic fluorescence of lysozyme at 340 nm can be quenched by cephalosporin analogues through the static quenching and non-radiative energy transferring procedure. In the acetate buffer solution with pH 7.0 and 298 K, the quenching fluorescence intensity was in a good linearity over the concentration of drugs in the range of 1–100 μmol L⁻¹, 0.1–100 μmol L⁻¹, 0.5–100 μmol L⁻¹ and 0.05–100 μmol L⁻¹ for cefradine, cefuroxime, cefotaxime and ceftriaxone, respectively. The quenching ability or the binding ability of the studied drugs followed the pattern: ceftriaxone > cefotaxime > cefuroxime > cefradine, which was close to the order of their antibacterial ability. The binding parameters including the association constant and the number of binding potential point were calculated at different temperatures (288, 298 and 308 K), and thermodynamic parameters ΔH°, ΔS° and ΔG° were given. The binding mode of lysozyme with cephalosporins showed that the hydrophobic effect might play a major role. The binding distance between cephalosporin and tryptophan residue in lysozyme was obtained. The results provided the quantitative information for the binding of cephalosporin to lysozyme, and it was suggested that the drugs probably bound to the active site near Trp62 in lysozyme.     

An NBD-based Sensitive and Selective Fluorescent Sensor for Copper(II) Ion

A new 7-nitrobenz-2-oxa-1,3-diazole (NBD) derived fluorescent probe (1) exhibiting high selectivity for Cu²⁺ detection, produced significant fluorescence quenching in the presence of Cu²⁺ ion, while the metal ions Ca²⁺, Cd²⁺, Co²⁺, Fe²⁺, Hg²⁺, Mg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺ produced only minor changes in fluorescence. The apparent association constant (K _a) for Cu²⁺ binding in chemosensor 1 was found to be 1.22 × 10³ M⁻¹. The maximum fluorescence quenching activity caused by Cu²⁺ binding to 1 was observed over the pH range 6–10.     

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.     

Spectrofluorimetric Assessment of Doxycycline Hydrochloride in Pharmaceutical Tablets and Serum Sample Based on the Enhancement of the Luminescence Intensity of the Optical Sensor Sm<Superscript>3+</Superscript> Ion

A simple and sensitive spectrofluorimetric method for determination of trace amount of doxycycline hydrochloride (DC) in pharmaceutical tablets and serum samples was developed. In ammonia buffer solution of pH 8.9 the doxycycline hydrochloride can remarkably enhance the luminescence intensity of the Sm³⁺ ion in Sm³⁺- DC complex at λ_ex = 400 nm. The produced luminescence intensity of Sm³⁺- DC complex in DMSO is in proportion to the concentration of DC and used as optical sensor for its determination. The dynamic range for the determination of DC is 1 × 10⁻⁸ – 5 × 10⁻⁶ mol L⁻¹ and in case of quantum yield calculations is 7 × 10⁻⁹ – 5 × 10⁻⁶ mol L⁻¹ with detection limit of 6.5 × 10⁻¹⁰ mol L⁻¹. The enhancement mechanism of the luminescence intensity in the Sm³⁺- DC system has been also discussed. A comparison with other spectrofluorimetric methods for tetracycline derivatives in which Eu³⁺ ion is used instead of Sm³⁺ ion is also studied.     

Sensitive Determination of Norfloxacin by the Fluorescence Probe of Terbium (III)- Sodium Dodecylbenzene Sulfonate and Its Luminescence Mechanism

The fluorescence system of the norfloxacin-Tb³⁺- sodium dodecylbenzene sulfonate (SDBS) was investigated in this paper. The experiments indicated that the fluorescence intensity of the Tb³⁺-SDBS was greatly enhanced by the norfloxacin. On the basis of the above findings, a sensitive fluorimetric method for determining the norfloxacin was established. The fluorescence intensity was measured by a 1-cm quartz cell with the excitation wavelength of 290 nm and the emission wavelength of 545 nm. The enhanced fluorescence intensity of the system (Δ F) showed a good linear relationship with the concentration of norfloxacin in the range of 5.0×10⁻⁹ mol L⁻¹–2.0×10⁻⁶ mol L⁻¹, its correlation coefficient was 0.9991 and the detection limit (S/N=3) was 1.2×10⁻⁹ mol L⁻¹. The presented method was used to determine the norfloxacin in real pharmaceutical samples. The luminescence mechanism was also discussed in detail. In the fluorescence system of the norfloxacin-Tb³⁺-SDBS, the SDBS not only acted as the surfactant, but also acted as the energy donor.     

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.     

A Chemosensing Ensemble for the Detection of Cysteine Based on the Inner Filter Effect Using a Rhodamine B Spirolactam

A fluorescent chemosensing ensemble for the detection of cysteine is designed based on the fluorescence inner filter effect. The method employs the coordination of Cu²⁺ ion with salicylaldehyde rhodamine B hydrazone (I), a colorless and non-fluorescent rhodamine B spirolactam derivative to form I-Cu(II), a pink color but weakly fluorescent complex. When rhodamine B was introduced to the I-Cu(II) complex solution, the fluorescence signal of rhodamine B is dramatically decreased because of the fluorescence inner filter effect (IFE). Upon adding cysteine to the above solution, it can complex preferentially to Cu²⁺ compared to I, and the I-Cu(II) complex dissociates, which thus decreases the fluorescence IFE of the solution, and in turn leading to the fluorescence increase of the chemosensing system. Based on the above mechanism, a fluorescent chemosensing ensemble for cysteine is developed. The fluorescence increase is linearly with cysteine concentration up to 10.0 μ mol L⁻¹, with a detection limit of 1.4 × 10⁻⁷ mol L⁻¹ (3σ). The optimal conditions of the proposed method were studied and the selectivity of the proposed method was investigated in this paper.     

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.     

Selective Recognition of Cobalt (II) Ion by a New Cryptand Compound with N2O2S2 Donor Atom Possessing 2-Hydroxy-1-Naphthylidene Schiff Base Moiety

A new cryptand compound carrying 2-hydroxy-1-naphthylidene Schiff base moiety (3) was designed and synthesized by reaction of the corresponding macrobicyclic amine compound (1) and 2-hydroxy-1-naphthaldehyde (2). The influence of metal cations such as Mg²⁺, Ca²⁺, Sr²⁺, Fe²⁺,Co²⁺, Mn²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Al³⁺ and Pb²⁺ on the spectroscopic properties of the new fluoroionophore was investigated in acetonitrile-dichloromethane solution (9.5/0.5) by means of absorption and emission spectrometry. The blue shifts on the fluorescence spectrum were observed for all metal cations at 504nm. At the same time the fluorescence spectrum of the ligand showed quenching in the intensity of the signal at 504 nm for all metal cations except for Zn²⁺. Interaction of Co²⁺ with the ligand caused quenching of naphtyl fluorescence higher than 84%. The method showed good selectivity and sensitivity for Co²⁺ with respect to other metal cations with linear range and detection limit of 1.5 × 10⁻⁷ to 3.3 × 10⁻⁶M and 4.8 × 10⁻⁸M respectively.     

A Fluorescein-based Fluorogenic Probe for Fluoride Ion Based on the Fluoride-induced Cleavage of <Emphasis Type="Italic">tert</Emphasis>-butyldimethylsilyl Ether

A highly sensitive and selective fluorogenic probe for fluoride ion, fluorescein di-tert-butyldimethylsilyl ether (FTBS), was designed and synthesized. FTBS was a colorless, non-fluorescent compound and was synthesized via the one-step reaction of fluorescein with tert-butyldimethylsilyl chloride. Upon incubation with fluoride ion in DMF-water solution (7 : 3, V/V), the Si-O bond of FTBS was cleaved, causing a large increase in fluorescence intensity and thereby allowing a selective detection of fluoride ion. The fluorescence increase is linearly with fluoride concentration in the range 0.1–2.0 μmol L⁻¹ with a detection limit of 0.041 μmol L⁻¹ (3σ). The excellent selective signaling behavior of the proposed probe was found to originate from the high affinity of silicon toward fluoride ion. The method has been successfully applied to the fluoride determination in multi-trace elements injection and toothpaste samples, and the results are agreed well with those obtained by the fluoride-ion selective electrode method.     

Fluorescence Enhancement Effect for the Determination of Polychlorinated Biphenyls with Bovine Serum Albumin

A sensitive and selective method for the trace determination of 3, 3’, 4, 4’-tetrachlorobiphenyl (PCB77) by using bovine serum albumin (BSA) as a fluorescence probe was introduced. Under optimum conditions, the enhanced fluorescence intensity was proportional to the concentration of polychlorinated biphenyls in the range of 8.9 × 10⁻⁸–5.0 × 10⁻⁶ mol L⁻¹ for PCB77, and 5.0 × 10⁻⁷–5.0 × 10⁻⁶ mol L⁻¹ for 2, 2’, 5, 5’-tetrachlorbiphenyl (PCB52). The detection limits (S/N = 3) of PCB77 and PCB52 were 2.6 × 10⁻⁸ mol L⁻¹ and 2.9 × 10⁻⁷ mol L⁻¹, respectively. Furthermore, the fluorescence enhancement mechanism was discussed in detail. Results indicated that fluorescence enhancement of the system originated from the formation of BSA-PCBs complexes. In addition, PCBs were mainly bound to the tyrosine residues in BSA molecules.     

A Novel Benzimidazole-Based Chemosensor for Fluorometric Determination of Zinc Ions

A simple and novel Schiff base chemosensor (BMHM) based on benzimidazole was synthesized. In ethanol–water (1:1, v/v) medium on varying concentrations of Zn²⁺ chemosensor exhibited a strong and quick turn on fluorescence response. The Zn²⁺ recognition was based on the Chelation–enhanced fluorescence effect. The binding constant and limit of detection for BMHM-Zn²⁺ complexation were estimated to be 7.99?×?104 M^?1 and 0.148 µM, respectively. The extreme fluorescent enhancement caused by Zn²⁺ binding in chemosensor BMHM occurred at a pH range of 6–7. The practical use of chemosensor BMHM was tested by determination of Zn²⁺ in real water samples and comparing the results with the data obtained using high resolution inductively coupled plasma mass spectrometry.

     

Mid-Infrared Emission Characteristic and Energy Transfer of Ho<Superscript>3+</Superscript>-Doped Tellurite Glass Sensitized by Tm<Superscript>3+</Superscript>

We report on 2.0-μm emission characteristic and energy transfer of Ho³⁺-doped tellurite glass sensitized by Tm³⁺ upon excitation of a conventional 808 nm laser diode. The Judd-Ofelt strength parameters, spontaneous radiative transition probabilities and radiative lifetime of Ho³⁺ have been calculated from the absorption spectra by using the Judd-Ofelt theory. Significant enhancement of 2.0-μm emission of Ho³⁺ has been observed with increasing Tm³⁺ doping up to 0.7 mol%. The energy transfer coefficient of the forward Tm³⁺→Ho³⁺ is approximately 17 times larger than that of the backward Tm³⁺←Ho³⁺ energy transfer. Our result indicates that the maximum gain of 2.0-μm emission, assigned to the transition of ⁵I₇→⁵I₈ of Ho³⁺, might be achieved from the tellurite glass at the concentration of 0.5 mol% of Tm₂O₃ and 0.15 mol% of Ho₂O₃. The high gain coefficient and quantum efficiency (1.16) along with the large value of the product of the stimulated emission cross-section and the measured radiative lifetime (4.12×10⁻²⁷ m²s) of the Ho³⁺/Tm³⁺-codoped tellurite glasses might find potential applications in efficient 2.0-μm laser.