Pyridinium‐Fused Pyridinone: A Novel “Turn‐on” Fluorescent Chemodosimeter for Cyanide

A new chemodosimeter based on pyridinium‐fused pyridinone iodide ( PI ) has been obtained through a “clean reaction” method. This compound can detect CN^? in aqueous solution with a high selectivity and rapid response. The detection of CN^? occurs through the nucleophilic attack of CN^? on the C?N bond, which induces the destruction of the π‐conjugation on the pyridinium ring. Support of this detection mechanism was obtained by ¹H NMR titration, HR‐MS, and DFT calculations. Upon the addition of 10 equivalents CN^? to a solution of PI in THF/H₂O (1:1, v/v), a 57‐fold enhancement in fluorescence intensity was observed at the maximum emission wavelength of 457 nm. Meanwhile, the maximum absorption wavelength was also blue‐shifted from 447 nm to 355 nm. Other common anions such as BF₄^?, PF₆^?, F^?, Cl^?, Br^?, I^?, H₂PO₄^?, ClO₄^?, CH₃COO^?, NO₂^?, N₃^?, and SCN^? had little effect on the detection of CN^?. The response time of PI for CN^? was less than 5 seconds. The detection limit was calculated to be 5.4×10^?8 M , which is lower than the maximum permission concentration in drinking water (1.9 μM ) set by the World Health Organization (WHO).     

Synthesis and characterization of poly(1,4‐bis((E)‐2‐(3‐dodecylthiophen‐2‐yl)vinyl)benzene) derivatives

New amorphous semiconducting copolymers, poly(9,9‐dialkylfluorene)‐alt‐(3‐dodecylthienyl‐divinylbenzene‐3‐dodecylthienyl) derivatives (PEFTVB and POFTVB), were designed, synthesized, and characterized. The structure of copolymers was confirmed by H NMR, IR, and elemental analysis. The copolymers showed very good solubility in organic solvents and high thermal stability with high T_g of 178–185 °C. The weight average molecular weight was found to be 107,900 with polydispersity of 3.14 for PEFTVB and 76,700 with that of 3.31 for POFTVB. UV–vis absorption studies showed the maximum absorption at 428 nm (in solution) and 435 nm (in film) for PEFTVB and at 430 nm (in solution) and 436 nm (in film) for POFTVB. Photoluminescence studies showed the emission at 498 nm (in solution) and 557 nm (in film) for PEFTVB and at 498 nm (in solution) and 536 nm (in film) for POFTVB. The solution‐processed thin‐film transistors showed the carrier mobility of 2 × 10^?4 cm² V^?1 s^?1 for PEFTVB‐based devices and 2 × 10^?5 cm² V^?1 s^?1 for POFTVB‐based devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3942–3949, 2010     

Amperometric Glucose Biosensor Based on Ultrafine Platinum Nanoparticles

Abstract

In the present paper the ultrafine and highly dispersed platinum nanoparticles (average size 3 nm) were used for the construction of a glucose biosensor in a simple method. An excellent response to glucose has been obtained with a high sensitivity (137.7 µA mM^?1 cm^?2) and fast response time (5 s). The biosensor showed a detection limit of 5 µM (at the ratio of signal to noise, S/N=3) and a linear range form 0.2 to 3.2 mM with a correlation coefficient r=0.999. The apparent Michaelis–Menten constant (k _m) and the maximum current were estimated to be 9.36 and 1.507 mA mM^?1 cm^?2, respectively. In addition, effects of pH value, applied potential and the interferents on the amperometric response of the sensor were investigated and discussed.     

对位氨基能显著提高D-A-D型化合物的双光子吸收性能

报道了具有典型D-A-D型共轭结构的反式2,5-二氰基-1,4-二(4'-甲氧基苯乙烯基)苯(MOS-CN), 2,5-二氰基-1,4-二(4'-二甲胺基苯乙烯基)苯(MAS-CN)和1,4-二(4'-甲氧基苯乙烯基)苯(MOS)的合成. 用核磁、红外和元素分析进行了表征. 测试了紫外吸收光谱、单光子荧光光谱、双光子荧光光谱、双光子吸收系数及双光子吸收截面. 在800 nm的飞秒脉冲激光激发下, 化合物MOS-CN, MAS-CN和MOS分别发出很强的绿色、黄色和蓝色上转换荧光. 化合物MOS-CN, MAS-CN和MOS的最大吸收波长、单光子发射波长、双光子诱导荧光波长、荧光量子产率、双光子吸收系数、双光子吸收截面及双光子荧光寿命各分别是393, 473, 367 nm; 470, 569, 434 nm; 475, 574, 438 nm; 0.12, 0.72, 0.21; 0.8, 5.3, 0.3 cm/GW; 270, 1790, 101 GM; 140 ps, 1.32 ns, 54 ps. MAS-CN的双光子吸收截面是MOS-CN的6.63倍, MOS-CN的双光子吸收截面是MOS的2.67倍, 表明对位氨基显著地提高了化合物的双光子吸收性能, 氰基也较大地提高了双光子吸收截面.     

Optical Determination of Glucose with Glucose Oxidase Immobilized in PVC together with Fluorescent Oxazol‐5‐One Derivatives

Abstract

Fully reversible biosensors for glucose monitoring based on solid polyvinylchloride (PVC) films where the enzyme glucose oxidase (GOx) was incorporated together with 2‐phenyl‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐1), 2‐(3,5‐dinitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐2), 2‐(4‐nitrophenyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐3) and 2‐(4‐tolyl)‐4‐[4‐(1,4,7,10‐tetraoxa‐13‐azacyclopentadecyl)benzylidene]‐5‐oxazolone (CPO‐4) derivatives have been developed. The limit of detection (LOD) values for glucose were found to be 1.47×10^?5 M, 2.01×10^?5 M, 0.89×10^?5 M, and 0.12×10^?5 M for CPO‐1, CPO‐2, CPO‐3, and CPO‐4, respectively (n=7). Sensor films were found to have excellent photostability.     

Preparation of an Electrode Modified with an Electropolymerized Film as a Mediator of NADH Oxidation and Its Application in an Ethanol/O2 Biofuel Cell

This paper reports a novel mediator for the oxidation of β‐nicotinamide adenine dinucleotide (NAD⁺/NADH), an electropolymeric film (pAPRu) of [Ru(NH₂‐phen)₃]²⁺. A pAPRu‐modified electrode was prepared via electropolymerization and exhibited catalytic activity toward the electrochemical oxidation of NADH due to the imine moieties of pAPRu. The electrochemical oxidation of ethanol was observed using an alcohol dehydrogenase (ADH)‐immobilized electrode. A compartmentless ethanol/O₂ biofuel cell composed of an ADH anode and a bilirubin oxidase cathode was constructed. The maximum current density and the maximum power density of the biofuel cell were 190 µA cm^?2 and 31 µW cm^?2 (at 0.29 V), respectively.     

Highly Efficient Orange and Warm White Phosphorescent OLEDs Based on a Host Material with a Carbazole–Fluorenyl Hybrid

A new carbazole–fluorenyl hybrid compound, 3,3′(2,7‐di(naphthaline‐2‐yl)‐9H‐fluorene‐9,9‐diyl)bis(9‐phenyl‐9H‐carbazole) (NFBC) was synthesized and characterized. The compound exhibits blue‐violet emission both in solution and in film, with peaks centered at 404 and 420 nm. In addition to the application as a blue emitter, NFBC is demonstrated to be a good host for phosphorescent dopants. By doping Ir(2‐phq)₃ in NFBC, a highly efficient orange organic light‐emitting diode (OLED) with a maximum efficiency of 32 cd A^?1 (26.5 Lm W^?1) was obtained. Unlike most phosphorescent OLEDs, the device prepared in our study shows little efficiency roll‐off at high brightness and maintains current efficiencies of 31.9 and 26.8 cd A^?1 at a luminance of 1000 and 10 000 cd m^?2, respectively. By using NFBC simultaneously as a blue fluorescence emitter and as a host for a phosphorescent dopant, a warm white OLED with a maximum efficiency of 22.9 Lm W^?1 (21.9 cd A^?1) was also obtained.     

Octa[4‐(9‐carbazolyl)phenyl]silsesquioxane‐Based Porous Material for Dyes Adsorption and Sensing of Nitroaromatic Compounds

A new fluorescent hybrid porous polymer (HPP) is synthesized by an anhydrous FeCl₃‐mediated oxidative coupling reaction of octa[4‐(9‐carbazolyl)phenyl]silsesquioxane (OCPS). The polymer possesses a surface area of 1741 m² g^?1 and hierarchical bimodal micropores (1.41 and 1.69 nm) and mesopores (2.65 nm). The material serves as an excellent adsorbent for CO₂ and dyes with high adsorption capacity for CO₂ (8.53 wt %,1.94 mmol g^?1), congo red (1715 mg g^?1) and rhodamine B (1501 mg g^?1). In addition, the presence of peripheral cabozolyl groups with extended π‐conjugation in the crosslinked framework imparts luminescent character to the polymer and offers the detection of nitroaromatic compounds.     

Photocytotoxicity of the Fluorescent Nonsteroidal Androgen Receptor Ligand TDPQ†

1,2,3,4‐tetrahydro‐2,2‐dimethyl‐6‐(trifluoromethyl)‐8‐pyridono[5,6‐g]quinoline (TDPQ), a selective nonsteroidal androgen receptor (AR) ligand, is a fluorescent compound. We characterized its spectral properties in comparison with the structural precursor carbostyril 151 (C151) and with its racemic structural isomer 4‐ethyl‐1,2,3,4‐tetrahydro‐6‐(trifluoromethyl)‐8‐pyridino[5,6‐g]quinoline (ETPQ). The absorption maximum in CH₃CN of either TDPQ or ETPQ is 400 nm whereas that of C151 is 350 nm. The fluorescence lifetimes (τ) and quantum yields (?_f) in CH₃CN are typical of fluorescent dyes: TDPQ (4.2 ns, 0.8) and ETPQ (4.6 ns, 0.76). C151 showed lower τ and ?_f of 0.2 ns and 0.02, respectively. TDPQ can function as a fluorescent label at (sub)micromolar concentrations. We detected TDPQ fluorescence in human breast tumor cells using confocal microscopy. While the fluorescence maxima of the compounds were solvent insensitive, the ?_f for ETPQ decreased in aqueous solutions regardless of the presence of albumin or DNA. The ?_f of TDPQ was less affected. The quantum yield of singlet oxygen (¹O₂) photosensitization (?_so) by TDPQ and ETPQ was about 7% in CH₃CN, sufficient to induce photocytotoxicity. TDPQ was photocytotoxic in AR‐positive MDA‐MB‐453 breast cancer cells but not in AR‐negative MDA‐MB‐231 cells. The combination of AR selectivity with photocytotoxicity makes TDPQ a promising candidate for selective targeting of AR‐positive cells during photodynamic therapy.     

Hybrid Conjugated Organic Oligomers Consisting of Oligodiacetylene and Thiophene Units: Synthesis and Optical Properties

Novel and highly soluble hybrid conjugated organic oligomers consisting of oligodiacetylene and thiophene units have been synthesized in high purity through iterative and divergent approaches based on a sequence of Sonogashira reactions. The series of thiophene‐containing oligodiacetylenes (ThODAs) and homocoupled ThODAs (HThODAs) show—both in solution and in the solid state—a strong optical absorption, which is progressively red shifted with increasing chain length. The linear correlation of the absorption maximum (λ^A_max) with the inverse of conjugation length (CL=number of double and triple bonds) shows that the effective conjugation length of this system is extended up to at least CL=20. Furthermore, absorption measurements of dropcast thin films display not only a bathochromic shift of the absorption maxima but also a higher wavelength absorption, which is attributed to increased π–π interactions. The wavelength of the maximum fluorescence emission (λ^E_max) also increases with CL, and emission is maximal for oligomers with CL=7–12 (fluorescence quantum yield Φ_F=～0.2). Both longer and shorter oligomers display marginal emission. The calculated Stokes shifts of these planar materials are relatively large (0.4 eV) for all oligomers, and likely due to excitation to the S₂ state, thus suggesting that the presence of enyne moieties dominates the ordering of the lowest excited states. The fluorescence lifetimes (τ_F) are short (τ_F,_max=?1 ns) and closely follow the tendency obtained for the fluorescence quantum yield. The anisotropy lifetimes show a near‐linear increase with CL, in line with highly rigid oligomers.     

Enzyme electrodes with substrate and co-enzyme amplification

The enzyme couples horseradish peroxidase/glucose dehydrogenase, glucose oxidase/glucose dehydrogenase, and cytochrome b₂/lactate dehydrogenase are applied in enzyme electrodes. Based on amplification by the recyclization reactions catalyzed by these two-enzyme systems, NADH, NAD⁺, glucose, lactate and pyruvate, are determined with 8–40-fold increased sensitivity compared to the unamplified reactions. Detection limits are 1.0 × 10^?6 M NADH, 1.2 × 10^?6 M NAD⁺, 8 × 10^?7 M glucose, and 3 × 10^?7 M lactate or pyruvate.     

Study of the rate of methyl loss and the structure of the product ion as a function of the lifetime of the molecular ion of pent-3-en-2-ol

The normalized unimolecular rate constant for loss of a methyl radical from pent-3-en-2-ol molecular ions with lifetimes ranging from 10^?11 to 10^?9 s was studied by field ionization kinetics (FIK). The normalized rate curve shows maxima at molecular ion lifetimes of 10^?10.5 and 10^?10.1 s. Based on results for deuterium and ¹³C-labelled pent-3-en-2-ol, the maximum at 10^?10.5 s is ascribed to loss of the methyl group at the 1-position by a direct cleavage reaction. The maximum at 10^?10.1 s is attributed to a 1,2-H shift-initiated rearrangement of the molecular ion, which leads to loss of the methyl group at the 5- and 1-positions. The time dependence of the processes in the form of the maxima on the normalized rate curve is discussed qualitatively in terms of a lower critical energy and a tighter transition state of the 1,2-H shift than those of the direct cleavage reaction. Collision-induced dissociation of the [C₄H₇O]⁺ product ions in combination with FIK provides evidence that at molecular ion lifetimes corresponding to the first maximum on the rate curve protonated crotonaldehyde is formed, whereas protonated methyl vinyl ketone and the butyryl cation are formed at times corresponding to the second maximum.     

Spectrophotometric Determination of Palladium(II) with n-Hydroxy-N,N-Diphenylbenzamidine and 1 -(2-Pyridylazo)-2-Naphthol

A spectrophotometric method to determine palladium(II) at trace levels is based on the extraction of palladium(II) as a binary complex with N-hydroxy-N,N′-diphenylbenzamidine (HDPBA) in chloroform at pH 5.0 ± 0.2. The complex shows maximum absorbance at 400 nm with molar absorptivity 6.4 × 10³ L mol^?1 cm^?1. The sensitivity of the Pd(II)-HDPBA complex was enhanced by the addition of l-(2-pyridylazo)-2-naphthol (PAN). The green coloured complex shows maximum absorbance at 620 nm with molar absorptivity 1.58 × 10⁴ L mol^?1 cm^?1. Sandell's sensitivity and the detection limit of the method are 0.0067 μg cm^?2and 0.1 μg Pd(II) mL^?1, respectively. Most common metal ions associated with palladium metal do not interfere. The effects of various analytical parameters on the extraction of the metal are discussed.     

Excited-State Dynamics of Thienoguanosine,an Isomorphic Highly Fluorescent Analogue of Guanosine

Thienoguanosine (^thG) is an isomorphic analogue of guanosine with promising potentialities as fluorescent DNA label. As a free probe in protic solvents, ^thG exists in two tautomeric forms, identified as the H1, being the only one observed in nonprotic solvents, and H3 keto–amino tautomers. We herein investigate the photophysics of ^thG in solvents of different polarity, from water to dioxane, by combining time-resolved fluorescence with PCM/TD-DFT and CASSCF calculations. Fluorescence lifetimes of 14.5–20.5 and 7–13 ns were observed for the H1 and H3 tautomers, respectively, in the tested solvents. In methanol and ethanol, an additional fluorescent decay lifetime (≈3 ns) at the blue emission side (λ≈430 nm) as well as a 0.5 ns component with negative amplitude at the red edge of the spectrum, typical of an excited-state reaction, were observed. Our computational analysis explains the solvent effects observed on the tautomeric equilibrium. The main radiative and nonradiative deactivation routes have been mapped by PCM/TD-DFT calculations in solution and CASSCF in the gas phase. The most easily accessible conical intersection, involving an out-of plane motion of the sulfur atom in the five-membered ring of ^thG, is separated by a sizeable energy barrier (≥0.4 eV) from the minimum of the spectroscopic state, which explains the large experimental fluorescence quantum yield.     

An improved laser vaporization cluster source and time-of-flight mass spectrometer

The radiative lifetimes of the 7p ² P _{3/2, 1/2} states of silver and the hyperfine structure of the 7p ² P _3/2 state have been measured using pulsed laser excitation and direct observation of the induced fluorescence light decay. In order to excite this doublet, VUV radiation at 185 nm was applied, as generated by frequency tripling and anti-Stokes Raman shifting of the output of a Nd: YAG laser pumped dye laser. The lifetimes were found to be τ=255(20) ns and τ=285(25) ns for theJ=3/2 state andJ=1/2 state, respectively. The hyperfine structure of the 7p ² P _3/2 state was measured by the quantum beat method. The magnetic dipole interaction constant for the¹⁰⁷Ag isotope was found to bea=?4.5(2) MHZ.     

The NADH Electrochemical Detection Performed at Carbon Nanofibers Modified Glassy Carbon Electrode

In this work, the capability of carbon nanofibers to be used for the design of catalytic electrochemical biosensors is demonstrated. The direct electrochemistry of NADH was studied at a glassy carbon electrode modified using carbon nanofibers. A decrease of the oxidation potential of NADH by more than 300 mV is observed in the case of the assembled carbon nanofiber‐glassy carbon electrode comparing with a bare glassy carbon electrode. The carbon nanofiber‐modified electrode exhibited a wide linear response range of 3×10^?5 to 2.1×10^?3 mol L^?1 with a correlation coefficient of 0.997 for the detection of NADH, a high specific sensitivity of 3637.65 (μA/M cm²), a low detection of limit (LOD=3σ) of 11 μM, and a fast response time (3 s). These results have confirmed the fact that the carbon nanofibers represent a promising material to assemble electrochemical sensors and biosensors.     

Electrocatalytic oxidation of the reduced nicotinamide adenine dinucleotide at carbon ionic liquid electrode modified with polythionine/multi-walled carbon nanotubes composite

A carbon ionic liquid electrode (CILE) was modified with a polythionine (PTh)/multi-walled carbon nanotubes (MWCNTs) composite and used for the detection of reduced nicotinamide adenine dinucleotide (NADH). The electrode was prepared by electrochemical polymerization of thionine on the MWCNTs in neutral medium. Cyclic voltammetry indicated that the electrode was capable of mediating the oxidation of NADH at an overpotential as low as 0.03 V. Amperometric experiments showed that a sensitive and stable response towards NADH is obtained within 5 s. The linear range for the determination of NADH is from 0.8 μmol L^?1 to 422 μmol L^?1, with a detection limit of 0.26 μmol L^?1 (S/N = 3). The wide linear range, lower detection limit and faster response towards NADH suggests that the new method potentially is useful for developing NAD⁺-dependent enzyme-based biosensors.     

Emission spectra of the radical cations of 1,3-dichlorobenzene, 1,4-dichlorobenzene and 1,3,5-trichlorobenzene in the gas phase

Emission spectra of the radical cations of 1,3-dichlorobenzene, 1,4-dichlorobenzene-h₄ (and -d₄), and 1,3,5-trichlorobenzene, excited in the gas phase by controlled electron impact, are presented. The band systems, which lie in the 500–750 nm wavelength region, are attributed to the B?(π^?1) → X?(π^?) electronic transition of the cations on the basis of photoelectron spectroscopic data. The NeI excited photoelectron spectra and the ionisation energies of chloro-,o-,m-,p-dichloro- and 1,3,5-trichlorobenzene have been obtained. The information acquired from the emission and photoelectron spectra is discussed and compiled to deduce the symmetry of the B? states. Emission, with quantum yield > 10^?5, could not be detected with electronically excited radical cations of chloro-,o-dichloro-, 1,2,4- and 1,2,3-trichloro- and tetrachloro-benzenes. This is attributed to the nature of the B? states, which arise by σ^?1 ionisation processes. The lifetimes of the zeroth and some vibrationally excited levels of the B?(π^?1) states were also measured and found to be 22 ± 2 ns for 1,3,5-trichlorobenzene cation and < 6 ns for 1,3- and 1,4-dichlorobenzene cations. The lifetimes of the latter two electronically excited cations are estimated to be two orders of magnitude shorter than 6 ns from the measurement of the relative emission intensities of the B? → B? band systems of the three title cations.     

Extraction—Spectrophotometric determination of nickel with 2-hydroxy-1-naphthaldoxime

A method for the solvent extraction—spectrophotometric determination of nickel with 2-hydroxyl-1-naphthaldoxime (HNA) has been studied. The method is based upon the formation of a nickel—HNA complex which is extracted into chloroform from an aqueous solution of pH 5.8. The nickel—HNA complex in chloroform exhibits an absorption maximum at 410 nm with molar absorptivity of 8.1 × 10³ liters mol^?1 cm^?1. Beer's law is applicable in the range from 5 to 50 μg of nickel. The mole ratio of the complex and effect of interfering ions are described.     

Controlled Electrodeposition of Au‐Copper Oxide Nanocomposite on a Renewable Carbon Ceramic Electrode for Sensitive Determination of NADH in Serum Samples

In this study, a sensitive nicotinamide adenine dinucleotide (NADH) biosensor based on Au‐Copper oxide nanocomposite modified carbon ceramic electrode (Au?CuO/CCE) was introduced. The developed NADH biosensor was prepared by controlled electrodeposition of copper and Au nanoparticles on the surface of a renewable CCE and was turned to Au?CuO/CCE by cycling the potential in alkaline media. The prepared electrode was carefully characterized with scanning electron microscopy, X‐ray diffraction, atomic force microscopy and cyclic voltammetry techniques. According to scan rate study, surface coverage (Γ) of the fabricated Au?CuO/CCE was calculated to be 1.54×10^?8 mol cm^?2 which was 3 time more than CuO/CCE. The fabricated electrode is well stable which could be reliably utilized for the determination of NADH with amperometry technique over the concentration range of 1–29 μM with sensitivity and detection limit (S/N=3) of 0.1025 μA μM^?1 and 0.09 μM respectively. The prepared biosensor was used for NADH determination in serum samples with fast response time and satisfactory analytical results.