Study of Enhanced Chemiluminescence of Diperiodatocuprate (III) on 1,10-Phenanthroline/Hydrogen Peroxide/Cetyltrimethylammonium Bromide System

In the paper, a chemiluminescence (CL) system was developed based on the catalytical effect of diperiodatocuprate (III) (DPC) on the 1,10-phenanthroline (phen)/hydrogen peroxide (H₂O₂) in the presence of cetyltrimethylammonium bromide (CTAB). The effects of experimental conditions were investigated. Meanwhile the increase of CL intensity of the DPC/phen/H₂O₂/CTAB system is proportional to the concentration of phen in the range of low concentration. The linear range of the calibration curve is 5.0 × 10⁻⁹–1.0 × 10⁻⁶ mol L⁻¹, and the corresponding detection limit is 1.9 × 10⁻⁹ mol L⁻¹. The effects of phenolic compounds (PCs) on the system were investigated. Hydroquinone was used as an example to investigate the application of the CL system to the determination of PCs. The quenched CL intensity is linearly related to the logarithm of concentration of hydroquinone. The linear range of the calibration curve is 2.5 × 10⁻⁹–1.0 × 10⁻⁵ g mL⁻¹, and the corresponding detection limit is 1.8 × 10⁻⁹ g mL⁻¹. This phen and hydroquinone can be synchronously determined. The method was applied to the determination of hydroquinone in water samples and the recoveries were from 92% to 106%.     

Interaction of a New Fluorescent Probe with DNA and its Use in Determination of DNA

In this paper we reported a metal complex 1-Zn (2,5-di-[2-(3,5-bis(2-pyridylmethyl)amine-4-hydroxy-phenyl)-ethylene]-pyrazine-Zn) as a fluorescent probe sensing DNA. The result of the competitive experiment of the probe with ethidium bromide (EB) to bind DNA, absorption spectral change and polarization change in the presence and absence of DNA revealed that interaction between the probe and DNA was via intercalation. Ionic strength experiment showed the existence of electrostatic interaction as well. Scatchard plots also confirmed the combined binding modes. The fluorescence enhancement of the probe was ascribed to highly hydrophobic environment when it bound the macromolecules such as DNA, RNA or denatured DNA. The binding constant between the probe and DNA was estimated as 3.13 × 10⁷ mol⁻¹ L. The emission intensity increase was proportional to the concentration of DNA. Based on this, the probe was used to determine the concentration of calf thymus DNA (ct-DNA). The corresponding linear response ranged from 2.50 × 10⁻⁷ to 4.75 × 10⁻⁶ mol L⁻¹, and detection limit was 1.93 × 10⁻⁸ mol L⁻¹ for ct-DNA.     

Impedance spectroscopy studies of poly (methyl methacrylate)-lithium salts polymer electrolyte systems

In the present work, five systems of samples have been prepared by the solution casting technique. These are the plasticized poly(methyl methacrylate) (PMMA-EC) system, the LiCF₃SO₃ salted-poly(methyl methacrylate) (PMMA-LiCF₃SO₃) system, the LiBF₄ salted-poly(methyl methacrylate) (PMMA-LiBF₄) system, the LiCF₃SO₃ salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiCF₃SO₃) system, and the LiBF₄ salted-poly(methyl methacrylate) containing a fixed amount of plasticizer ([PMMA-EC]-LiBF₄) system. The conductivities of the films from each system are characterized by impedance spectroscopy. The room temperature conductivity in the pure PMMA sample and (PMMA-EC) system is 8.57 × 10⁻¹³ and 2.71 × 10⁻¹¹ S cm⁻¹, respectively. The room conductivity for the highest conducting sample in the (PMMA-LiCF₃SO₃), (PMMA-LiBF₄), ([PMMA-EC]-LiCF₃SO₃), and ([PMMA-EC]-LiBF₄) systems is 3.97 × 10⁻⁶, 3.66 × 10⁻⁷, 3.40 × 10⁻⁵, and 4.07 × 10⁻⁷ S cm⁻¹, respectively. The increase in conductivity is due to the increase in number of mobile ions, and decrease in conductivity is attributed to ion association. The increase and decrease in the number of ions can be implied from the dielectric constant, ɛ_r-frequency plots. The conductivity–temperature studies are carried out in the temperature range between 303 and 373 K. The results show that the conductivity is increased when the temperature is increased and obeys Arrhenius rule. The plots of loss tangent against temperature at a fixed frequency have showed a peak at 333 K for the ([PMMA-EC]-LiBF₄) system and a peak at 363 K for the ([PMM-EC]-LiCF₃SO₃) system. This peak could be attributed to β-relaxation, as the measurements were not carried out up to glass transition temperature, T _g. It may be inferred that the plasticizer EC has dissociated more LiCF₃SO₃ than LiBF₄ and shifted the loss tangent peak to a higher temperature. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4]

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn⁴⁺ to form the complex [Sn(XO)₆]⁴⁺. [Sn(XO)₆]⁴⁺ can interact with Fin⁻ (fluorescein anion) to form the ion associate [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg²⁺ can catalyze H₂O₂ oxidizing the ion association complex [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which causes the RTP to quench. The ΔIp value is directly proportional to the concentration of Hg²⁺ in the range of 0.016–1.6 fg spot⁻¹ (corresponding concentration: 0.040–4.0 pg ml⁻¹, 0.40 μl spot⁻¹), and the regression equation of working cure is ΔIp=10.03+83.15 m Hg²⁺ (fg spot⁻¹), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot⁻¹(corresponding concentration: 9.0×10^–15 g ml⁻¹, the sample volume: 0.4 μl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H₂O₂ oxidizing the ion association complex ([Sn(XO)₆]⁴⁺·[(Fin)₄]⁻) SS-RTP quenching method to determine trace mercury is also discussed.     

Solid polymeric electrolyte of PVC–ENR–LiClO<Subscript>4</Subscript>

The ionic conductivity of PVC–ENR–LiClO₄ (PVC, polyvinyl chloride; ENR, epoxidized natural rubber) as a function of LiClO₄ concentration, ENR concentration, temperature, and radiation dose of electron beam cross-linking has been studied. The electrolyte samples were prepared by solution casting technique. Their ionic conductivities were measured using the impedance spectroscopy technique. It was observed that the relationship between the concentration of salt, as well as temperature, and conductivity were linear. The electrolyte conductivity increases with ENR concentration. This relationship was discussed using the number of charge carrier theory. The conductivity–temperature behaviour of the electrolyte is Arrhenian. The conductivity also varies with the radiation dose of the electron beam cross-linking. The highest room temperature conductivity of the electrolyte of 8.5 × 10⁻⁷ S/cm was obtained at 30% by weight of LiClO₄. The activation energy, E _a and pre-exponential factor, σ _o, are 1.4 × 10⁻² eV and 1.5 × 10⁻¹¹ S/cm, 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 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.     

The Sensitive Determination of Nucleic Acids Using Fluorescence Enhancement of Eu<Superscript>3+</Superscript>-BenzoylacetoneCetyltrimethylammonium Bromide-Nucleic Acid System

A new quantitative method for micro amounts of nucleic acids in aqueous solution is proposed using Eu³⁺-benzoylacetone (BA) complex as fluorescent probe in the presence of cetyltrimethyl-ammonium bromide (CTMAB). Under the optimum condition, the ratio of the fluorescence intensities with and without nucleic acids is proportional to the concentration of nucleic acid in the range of 1.0 × 10⁻⁹ to 5.0 × 10⁻⁶ g/mL for herring sperm DNA (hsDNA), 3.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for calf thymus DNA(ctDNA) and 8.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for yeast RNA (yRNA), and their detection limits are 0.33, 0.21 and 0.99 ng/mL, respectively. Actual sample (DNA of Arabidopsis thaliana) was determined satisfactorily. In addition, the interaction mechanism is also investigated.     

Ni-MH battery based on plasticized alkaline solid polymer electrolytes

Solid-state nickel metal hydride cells were fabricated using plasticized alkaline solid polymer electrolytes (ASPE) prepared from polyvinyl alcohol (PVA), potassium hydroxide (KOH), alumina (α-Al₂O₃), and propylene carbonate (PC). The ASPE film with PVA/KOH/α-Al₂O₃/PC/H₂O weight ratio of 1.00:0.67:0.09:2.64:1.32 and conductivity of (6.6 ± 1.7) × 10⁻⁴ S cm⁻¹ was used in fabrication of the electrochemical cells. To investigate the electrochemical properties of the plasticized ASPE, cells with the configuration Mg₂Ni/plasticized ASPE/Ni(OH)₂ were fabricated. At the eighth cycle with a current drain of 0.1 mA and plateau voltage of ∼1.1 V, the discharge lasted for 14 h before the cell was considered to have failed. The failure mode of the cell was due to the formation of thin Mg(OH)₂ insulating layers.     

ZrO<Subscript>2</Subscript>/DNA-derivated polyion hybrid complex membrane for the determination of hydrogen peroxide in milk

An efficient biosensing substrate based on ZrO₂/DNA-derivated polyion complex (PIC) membrane has been developed for the determination of hydrogen peroxide (H₂O₂) in this study. To fabricate such a PIC membrane, ZrO₂ nanoparticles were initially electrodeposited on the bare gold electrode (ZrO₂/Au), and deoxyribonucleic acid (DNA)-doped hemoglobin mixture was then assembled onto the ZrO₂/Au surface. The double-strand DNA provided a biocompatible microenvironment for the immobilization of biomolecules, greatly amplified the surface coverage of biomolecules on the electrode surface, and improved the sensitivity of the biosensor. The fabricated procedure of the proposed biosensor was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy. The performance and factors influencing the performance of the biosensor were also evaluated. Under optimal conditions, the developed biosensor exhibited a well-defined electrochemical behavior toward the reduction of H₂O₂ ranging from 1.1 μM to 2.3 mM with a detection limit of 0.5 μM (S/N = 3). The biosensor was applied to the determination of H₂O₂ in milk with satisfactory results. It is important to note that the PIC membrane provided an alternative substrate for the immobilization of other proteins.     

Structural,thermal and ion transport studies on nanocomposite polymer electrolyte-{(PEO + SiO<Subscript>2</Subscript>):NH<Subscript>4</Subscript>SCN} system

Development and characterisation of polyethylene oxide (PEO)-based nanocomposite polymer electrolytes comprising of (PEO-SiO₂): NH₄SCN is reported. For synthesis of the said electrolyte, polyethylene oxide has been taken as polymer host and NH₄SCN as an ionic charge supplier. Sol–gel-derived silica powder of nano dimension has been used as ceramic filler for development of nanocomposite electrolytes. The maximum conductivity of electrolyte ∼2.0 × 10⁻⁶ S/cm is observed for samples containing 30 wt.% silica. The temperature dependence of conductivity seems to follow an Arrhenius-type, thermally activated process over a limited temperature range.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Hydroxypropyl-β-Cyclodextrin Enhanced Determination for the Vitamin B<Subscript>12</Subscript> by Fluorescence Quenching Method

A novel fluorescence quenching method for the determination of Vitamin B₁₂(VB₁₂) had been developed. It was based on that the fluorescence intensity of erythrosine sodium(ES) could be enhanced by Hydroxypropyl-β-cyclodextrin(HP-β-CD) due to the formation of inclusion complex (HP-β-CD-ES), while the fluorescence intensity of HP-β-CD-ES was diminished after adding VB₁₂ into the system, and there was a linear relationship between the fluorescence quenching value of the system (ΔF) and the concentration of VB₁₂(c). The mechanism of the determination of VB₁₂was discussed. The results showed that under the optimal conditions, the linear range of calibration curve for the determination of VB₁₂ was 0.0∼2.1 × 10⁻⁵ mol/L, and the detection limit was 1.8×10⁻⁷ mol/ L. It could be satisfactorily applied to the determination of VB₁₂ in injections.     

Synthesis and characterization of electron beam evaporated LiCoO<Subscript>2</Subscript> thin films

LiCoO₂ thin films were prepared by electron beam evaporation technique using LiCoO₂ target with Li/Co ratio 1.1 in an oxygen partial pressure of 5 × 10⁻⁴ mbar. The films prepared at substrate temperature T _s < 573 K were amorphous in nature, and the films prepared at T _s > 573 K exhibited well defined (104), (101), and (003) peaks among which the (104) orientation predominates. The X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma (ICP) data revealed that the films prepared in the substrate temperature range 673–773 K are nearly stoichiometric. The grain size increases with an increase of substrate temperature. The Co–e_g absorption bands, are empty and their peak position lies at around 1.7 eV above the top to the Co–t_2g bands. The fundamental absorption edge was observed at 2.32 eV. The films annealed at 1,023 K in a controlled oxygen environment exhibit (104) out plane texture with large grains. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

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.     

Spectrofluorimetric Assessment of Chlorzoxazone and Ibuprofen in Pharmaceutical Formulations by using Eu-Tetracycline HCl Optical Sensor Doped in Sol–Gel Matrix

A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ_ex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10⁻⁹–1 × 10⁻⁴ and 1 × 10⁻⁸–7 × 10⁻⁵ mol L⁻¹, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10⁻¹⁰ , 9.6 × 10⁻¹⁰ and 5.6 × 10⁻¹⁰, 1.7 × 10⁻⁹ mol L⁻¹, respectively.     

Structure,thermal properties,conductivity and electrochemical stability of di-urethanesil hybrids doped with LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

Variable chain length di-urethane cross-linked poly(oxyethylene) (POE)/siloxane hybrid networks were prepared by application of a sol-gel strategy. These materials, designated as di-urethanesils (represented as d-Ut(Y′), where Y′ indicates the average molecular weight of the polymer segment), were doped with lithium triflate (LiCF₃SO₃). The two host hybrid matrices used, d-Ut(300) and d-Ut(600), incorporate POE chains with approximately 6 and 13 (OCH₂CH₂) repeat units, respectively. All the samples studied, with compositions ∞ > n ≥ 1 (where n is the molar ratio of (OCH₂CH₂) repeat units per Li⁺), are entirely amorphous. The di-urethanesils are thermally stable up to at least 200 °C. At room temperature the conductivity maxima of the d-Ut(300)- and d-Ut(600)-based di-urethanesil families are located at n = 1 (approximately 2.0 × 10⁻⁶ and 7.4 × 10⁻⁵ Scm⁻¹, respectively). At about 100 °C, both these samples also exhibit the highest conductivity of the two electrolyte systems (approximately 1.6 × 10⁻⁴ and 1.0 × 10⁻³ Scm⁻¹, respectively). The d-Ut(600)-based xerogel with n = 1 displays excellent redox stability.     

Fluorescence Enhancement of the Silver Nanoparticales – Curcumin - Cetyltrimethylammonium Bromide-nucleic Acids System and its Analytical Application

It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU) - cetyltrimethylammonium bromide (CTAB) – nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for fish sperm DNA (fsDNA), 2.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for calf thymus DNA (ctDNA), 1.0 × 10⁻⁸–1.0 × 10⁻⁶ g mL⁻¹ for yeast RNA (yRNA), and their detection limits (S/N = 3) are 8.0 ng mL⁻¹, 10.5 ng mL⁻¹ and 5.8 ng mL⁻¹, respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The interaction mechanism is also studied.     

Highly improved electroluminescence from double-layer devices based on a carbazole-functionalized europium<Superscript>3+</Superscript> complex

A novel europium complex Eu(TTA)₃(CPPO)₂ (1) (TTA=thenoyltrifluoroacetone, CPPO=9-[4-(diphenyl-phosphinoyl)-phenyl]-9H-carbazole) based on the phosphine oxide ligand with bipolar structure was used to fabricate double-layer devices. The strong hole injection and transport ability of 1 was proved. The luminance of 414 cd m⁻² was achieved with the device configuration ITO/Eu(TTA)₃(CPPO)₂(40 nm)/BCP (30 nm)/Mg:Ag (BCP = 2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline), which is favorable among double-layer organic light emitting devices based on small molecular Eu³⁺ complexes. The maximum current efficiency of 2.44 cd A⁻¹ and external quantum efficiency of 1.55% demonstrate the potential application of 1 as a promising candidate for high-efficiency, simple-structure and pure red-emitting devices.