A Novel Method for the Assessment of Cortisol Hormone in Different Body Fluids Using A New Photo Probe Thiazole Derivative

A low cost and accurate method for the detection and analytical determination of the cortisol in pharmaceutical preparation, blood serum and urine was developed. The method was based upon the enhancement of fluorescence intensity of the band at 424 nm of the photo probe by different cortisol concentrations in acetonitrile at (pH 5.7, λ_ex?=?320 nm). The influence of the different parameters, e.g. pH, solvent, cortisol concentration and foreign ions concentrations that control the enhancement process of fluorescence intensity of the band of photo probe was critically investigated. The remarkable enhancement of the fluorescence intensity at 424 nm in acetonitrile by various concentrations of cortisol was successfully used as a photo- probe for the assessment of cortisol concentration. The calibration plot was achieved over the concentration range 8.0?×?10^?6–5.5?×?10^?9 mol L^?1 cortisol with a correlation coefficient of 0.998 and a detection limit of 4.7?×?10^?9 mol L^?1. The developed method is simple and proceeds without practical artifacts compared to the other determination methods.     

Development of an Optode for Detection of Trace Amounts of Hg2+ in Different Real Samples Based on Immobilization of Novel Tetradentate Schiff Bases Bearing Two Thiol Groups in PVC Membrane

A very sensitive and reversible optical chemical sensor based on a novel tetradentate Schiff base namely N.N^/bis(2-aminothiophenol)benzene-1,2-dicarboxaldehyde (ATBD) immobilized within a plasticized PVC film for Hg²⁺ determination is described. At optimum conditions (i.e. pH 6.0), the proposed sensor displayed a linear response to Hg²⁺ over 1.0?×?10^?10 ? 1.0?×?10^?2 mol L^?1 with a limit of detection of 7.23?×?10^?11 mol L^?1 (0.0145 μgL^?1). Moreover, the results revealed that, under batch condition, the sensor is fully reversible within a response time?~?35 s. In addition to its high stability and reproducibility, the sensor showed good selectivity towards Hg²⁺ ion with respect to common metal cations. The sensor was successfully applied for determination of Hg²⁺ ion in some real samples, including hair, urine and well water samples. The results were in good correlation with the data obtained using cold vapor atomic absorption spectrometry.     

A selective sensor for nanolevel detection of lead (II) in hazardous wastes using ionic-liquid/Schiff base/MWCNTs/nanosilica as a highly sensitive composite

An effective potentiometric sensor had been fabricated for the rapid determination of Pb²⁺ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb²⁺ carbon paste electrode for the successfully determination of Pb²⁺ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF₆, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76?±?0.10 mV decade^?1) toward Pb²⁺ ions in the range of 5?×?10^?9?C1.0?×?10^?1 mol L^?1 with a detection limit of 2.51?×?10^?9 mol L^?1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5?C8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions.     

Synthesis and Analytical Application of a Novel Fluorescent Hg2+ Probe 3′, 6′-Bis(Diethylamino)-2-((2,4-Dimethoxybenzylidene)Amino)Spiro[Isoindoline-1,9′-Xanthene]-3-Thione

A novel probe, 3′,6′ - bis(diethylamino) -2- ((2,4-dimethoxybenzylidene)amino) spiro [isoindoline-1,9′-xanthene]-3-thione (RBS), was designed and synthesized. Its structure was characterized with elemental analysis, IR spectra and ¹H NMR. The probe displayed highly selective and sensitive recognition of Hg²⁺. Reacting with mercury ions in aqueous solution, its fluorescence intensity was enhanced significantly, while its color was changed from colorless to pink. So, a new fluorescence method of detection of Hg²⁺ was proposed. Its dynamic response concentration range and detection limit for Hg²⁺ were 5.00?×?10^?9 M to 1.00?×?10^?6 M detected and 1.83?×?10^?9 M, respectively. Satisfying results were obtained when the probe was applied to detect spiked Hg²⁺ in samples.     

Simultaneous Determination of Ritodrine and Isoxsuprine Using Coupling Technique of Synchronous Fluorimetry and H-Point Standard Addition Method

Simultaneous determination of two structurally related ß₂ adrenergic receptor agonists namely, Ritodrine HCl (RTH) and Isoxsuprine HCl (ISP) was performed using coupling technique of synchronous fluorimetry and H-point standard addition method. Under optimum conditions, linear determination ranges were 1.48 – 14.80?×?10^?6 mol L^?1 and 1.54 – 15.44?×?10^?6 mol L^?1 for ISP and RTH respectively. RTH and ISP could be determined simultaneously without interference from each other when their concentration ratio varies from 5:1 to 1:5 in the mixed sample. The proposed method was applied to the determination of RTH and ISP in synthetic mixture of pharmaceutical samples, the accuracy and precision of the results were satisfactory.     

Fluorescent carbon dots: facile synthesis at room temperature and its application for Fe<Superscript>2+</Superscript> sensing

A new route for one-pot preparation of carbon dots (CDs) was developed at room temperature using PEG400 as both the carbon source and passitive agent. The new method possesses the advantages of facile, rapid, energy-saving, without any external stimulus and environment friendly. By changing the content of NaOH, the PEG400-CDs with blue-emitting, yellow-emitting, orange red-emitting and red-emitting were obtained, and the formation mechanism were carefully investigated. In addition, a sensitive fluorescence sensor were developed for Fe²⁺ detection based on PEG400-CDs since the fluorescence of PEG400-CDs could be enhanced by Fe²⁺. It was found that there is a good linear relationship between the enhanced fluorescence and Fe²⁺ concentration in the range of 0.5 to 2.0 μmol·L^?1 with the detection limit of 6.0 × 10^?8 mol·L^?1, and Fe²⁺ in water samples was also determined with high accuracy and repeatability.     

Spectroscopic Determination of Cysteine with Alizarin Red S and Copper

ABSTRACT

The interaction between metal complex Cu²⁺–ARS (Alizarin Red S) and l-cysteine was investigated via fluorescence and absorption spectroscopies. In pH 5.2 Britton–Robinson buffer, the addition of L-cysteine into Cu²⁺–ARS system resulted in a fluorescence enhancement because cysteine reduced Cu²⁺ to Cu⁺, which led to Cu²⁺–ARS decompound, and ARS was released. The result was also supported by absorption spectroscopy change. A good linear response of fluorescence intensity as a function of cysteine concentration was obtained ranging from 1.0 × 10^?6 to 4.0 × 10^?5 mol L^?1 with the detection limit as 1.08 × 10^?7 mol L^?1. The introduced method has high selectivity over other amino acids such as cystine, tyrosine, tryptophan, methionine, and glycine. It was applied to determine cysteine in protein hydrolysate of fresh pig blood with recovery of 88.4–100.2%.     

An Efficient Fluorescence “Turn-On” Chemosensor Comprising of Coumarin and Rhodamine Moieties for Al<Superscript>3+</Superscript> and Hg<Superscript>2+</Superscript>

A potent fluorescence ‘turn-on’ receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg²⁺ and Al³⁺ is synthesized by condensation of rhodamine 6G hydrazide and 4-hydroxy-3-acetylcoumarin. In presence of Al³⁺ and/or Hg²⁺ the receptor (HL) exhibits deep pink colouration and a sharp band at 528 nm is appeared in UV–vis titration. Upon gradual addition of Al³⁺ and/or Hg²⁺ to the solution of HL significant enhancement of fluorescence intensity is observed at 564 nm in MeCN:H₂O (1:5, v/v) medium. The receptor is strongly bound to Al³⁺ and/or Hg²⁺ and the association constants (K_a) are found to be 1.74?×?10⁴ and 1.04?×?10⁴ M^??1 for Al³⁺ and Hg²⁺ respectively.

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Graphical Abstract A potent fluorescence ‘turn-on’ receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg²⁺ and Al³⁺ is synthesized and characterized. In presence of Al³⁺ and/or Hg²⁺ the receptor (HL) exhibits deep pink colouration and significant enhancement of fluorescence intensity is observed at 564 nm in MeCN:H₂O (1:5, v/v) medium. The receptor is strongly bound to Al³⁺ and/or Hg²⁺ and the association constants (K_a) are found to be 1.74?×?10⁴ and 1.04?×?10⁴ M^??1 for Al³⁺ and Hg²⁺ respectively.

     

Novel Pyrazoline-Based Selective Fluorescent Sensor for Hg2+

This paper presents the preparation of a pyrazoline compound and the properties of its UV–Vis absorption and fluorescence emission. Moreover, this compound can be used to determine Hg²⁺ ion with selectivity and sensitivity in the EtOH:H₂O?=?9:1 (v/v) solution. This sensor forms a 1:1 complex with Hg²⁺ and shows a fluorescent enhancement with good tolerance of other metal ions. This sensor is very sensitive with fluorometric detection limit of 3.85?×?10^?10 M. In addition, the fluorescent probe has practical application in cells imaging.     

A calix[4]arene derivative-doped perchlorate-selective membrane electrodes with/without multi-walled carbon nanotubes

In this study, poly (vinyl chloride)(PVC) membrane electrodes with/without multi-walled carbon nanotubes (MWCNTs) based on a calix[4]arene derivative for perchlorate ion were described. The influence of membrane composition, pH, conditioning solution on the potentiometric response of the electrodes was investigated. Perchlorate-selective PVC membrane electrode exhibited a slope of 47.8 ± 0.6 mV/pClO₄ in the range of 1.0 × 10^?7–1.0 × 10^?1 mol L^?1at pH 4.0 while the coated Pt electrodes with MWCNT-OH, MWCNT-COOH and MWCNT displayed slopes of 46.1 ± 0.7 mV/pClO₄ (5.0 × 10^?6–1.0 × 10^?1 mol L^?1), 50.4 ± 1.9 mV/pClO₄ (1.0 × 10^?6–1.0 × 10^?1 mol L^?1) and 44.4 ± 0.3 mV/pClO₄ (1.0 × 10^?5–1.0 × 10^?1 mol L^?1), respectively. Other response characteristics of these electrodes such as response time, lifetime and detection limit were identified, and the selectivity coefficients towards various anions were calculated by separate solution method. Moreover, the perchlorate-selective electrodes described here were successfully used as an indicator electrode for the determination of perchlorate in real samples such as tap water, river water and human urine by direct calibration method.     

A Fluorescent Chemodosimeter for Hg2+Based on a Spirolactam Ring-Opening Strategy and its Application Towards Mercury Determination in Aqueous and Cellular Media

A novel fluorescent chemosensor rhodamine B phenyl hydrazide (RBPH) for Hg²⁺ was designed and synthesized. This probe is highly sensitive, selective, and irreversible for Hg²⁺ and exhibits fluorescent response at 580 nm. RBPH also displayed detectable color change from colorless to pink upon treatment with Hg²⁺. This property has been utilized as naked eye detection for Hg²⁺ in various industrial samples. Fluorescence microscopic experiments demonstrated that this chemosensor is cell permeable and can be used for fluorescence imaging of Hg²⁺ in cellular media. This probe can detect Hg²⁺ with good linear relationships from 1 to 100 nM with r?=?0.99983 and the limit of detection were found to be 0.019 nM with?±?0.91 % RSD at 10 nM concentrations.     

Differential pulse anodic stripping voltammetric determination of Hg2+ at poly(Eriochrome Black T)-modified carbon paste electrode

The electrochemical behavior of Hg²⁺ was investigated in poly(Eriochrome Black T)-modified carbon paste electrode (CPE) using cyclic voltammetry (CV). Poly(Eriochrome Black T) was prepared in an alkaline medium on the surface of the CPE using a solution of Eriochrome Black T with the CV technique. The electrochemical impedance study revealed a better charge transfer kinetics at the modified electrode. The effects of variation of the experimental conditions, such as the concentration of electrolytes, pH, deposition time, and the deposition potential, which maximize current efficiency were studied. The optimum response of Hg²⁺ was observed in 1.0 M KCl solution. The differential pulse anodic stripping voltammetric technique was employed successfully to detect Hg²⁺, which gave a good linear response at low concentration levels of Hg²⁺. The detection limit was found to be 2.2?×?10^?10 M (S/N?=?3), which is comparable with that achieved in multiwall carbon nanotube-modified electrode. The remarkable electroanalytical performance of the modified electrode makes it amenable to employ it successfully as an electrochemical sensor for the determination of hazardous pollutant Hg²⁺ in environmental samples.     

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.     

Fluorescence Chemosensor for Determination of Carbon Dioxide and Its Application for Biodegradation Analysis of Polymers

A novel fluorescence sensor has been developed and applied for the determination of carbon dioxide released from the biodegradation of polymer materials and for the evaluation of the biodegradability of polymers. The proposed analytical method is based on the extraordinarily quenching effect of carbonate on fluorescence signal of N,N-diphenylthiourea system. Under the optimized experimental conditions, the fluorescence quenching system performed satisfactorily in a linear detection concentration ranging from 2.00 × 10^?4 to 9.00 × 10^?3 mol L^?1 of carbonate. The detection limit is 8.33 × 10^?5 mol L^?1 for carbonate. This proposed fluorescence system for the selective sensing of carbonate has been successfully applied to determine the biodegradability of polybutylene succinate and related polymers under controlled composting environment with devices assembled in our laboratory. The results exhibited that the biodegradation rate and final biodegradation percentage of biodegradable thermoplastic poly(ester urethane) elastomers, which embodies the block copolymer of poly(butylene succinate) with poly(diethylene glycol succinate), were correlated to the amount of poly(diethylene glycol succinate). In addition, the maximum biodegradation percentage of the testing polymers has reached 45.01%. This research demonstrates the development of chemosensors for rapid, selective, and sensitive detection of carbon dioxide is important and significant for both environmental and biological science.     

Swift heavy ion provoked structural, optical and electrical properties in SnO2 thin films

SnO₂ thin films grown on glass substrates at 300 ^°C by reactive thermal evaporation and annealed at 600 ^°C were irradiated by 120 MeV Ag⁹⁺ ions. Though irradiation is known to induce lattice disorder and suppression of crystallinity, we observe grain growth at a certain fluence of irradiation. X-ray diffraction (XRD) revealed the crystalline nature of the films. The particle size estimated by Scherrer’s formula for the irradiated films was in the range 10–25 nm. The crystallite size increases with increase in fluence up to 1×10¹² ions?cm^?2, whereas after that the size starts decreasing. Atomic force microscope (AFM) results showed the surface modification of nanostructures for films irradiated with fluences of 1×10¹¹ ions?cm^?2 to 1×10¹³ ions?cm^?2. The UV–visible spectrum showed the band gap of the irradiated films in the range of 3.56 eV–3.95 eV. The resistivity decreases with fluence up to 5×10¹² ions?cm^?2 and starts increasing after that. Rutherford Backscattering (RBS) reveals the composition of the films and sputtering of ions due to irradiation at higher fluence.     

Study on the Cofluorescence Effect of Europium (III)–Yttrium (III)–Balofloxacin–Sodium Dodecyl Sulfate System and Its Analytical Application

A new fluorescence enhancement phenomenon in the europium(III)–balofloxacin–sodium dodecyl sulfate system was observed when yttrium(III) was added. Based on this, a sensitive cofluorescence assay for the estimation of balofloxacin was established. Under the optimized conditions, the enhanced fluorescence signal was linear over the concentration of balofloxacin ranging from 3.0 × 10^?9 to 7.0 × 10^?6 mol L^?1 with a correlation coefficient of 0.9993. The detection limit (3 σ) was determined as 8.3 × 10^?10 mol L^?1. The presented method was successfully applied to determination of balofloxacin in pharmaceutical preparations, human serum, and urine. The possible fluorescence enhancement mechanism was also discussed.     

Studies of some physical properties of PrFe0.7Ni0.3O3 thin films after 200 MeV Ag15+ irradiation

PrFe_0.7Ni_0.3O₃ thin films (thickness ~ 200 nm) were prepared by pulsed laser ablation technique on LaAlO₃ substrate. These films were irradiated with 200?MeV Ag¹⁵⁺ ions at various fluencies, ranging from 1 × 10¹¹ to 1 × 10¹² ions/cm². These irradiated thin films were characterized by using X-ray diffraction, dc conductivity, dc magnetization and atomic force microscopy. These films exhibit orthorhombic structure and retain it even after irradiations. The crystallite size (110–137?nm), micro strain (1.48 × 10^?2–1.75 × 10^?2 line^?2?m^?4) and dislocation density (79.7 × 10¹⁴–53.2 × 10¹⁴ line/m²) vary with ion fluencies. An enhancement in resistivity at certain fluence and then a decrease in its value (0.22175–0.21813?Ω?cm) are seen. A drastic change in observed magnetism after ion irradiation is seen. With ion irradiation, an increase in surface roughness, due to the formation of hillocks and other factors, is observed. Destruction of magnetic domains after irradiation can also be visualized with magnetic force microscopy and is in close agreement with magnetization data. The impact on various physical properties in these thin films after irradiation indicates a distortion in the lattice structure and consequently on single-particle band width caused by stress-induced defects.     

Voltammetric behaviors of an emerging pollutant benzotriazole on multiwall carbon nanotubes (MWNTs)—Nafion modified electrode in various pH mediums

The electrochemical behaviors of an emerging pollutant, benzotriazole (BTA), at multiwall carbon nanotubes and Nafion modified glassy carbon electrode (MWNTs-Nafion/GCE) were investigated systematically. The electrochemical reduction of BTA was significantly improved by MWNTs-Nafion compared to bare GCE, ascribed to the excellent adsorption capacity and electrocatalytic activity of MWNTs. BTA presented well-defined reduction peaks only at pH <3.0, suggesting the involvement of lots of protons in the reduction process. Peak potential shifted negatively and peak current decreased significantly with pH increase. BTA showed various UV–Vis absorption spectra in acidic and alkaline mediums. Cathodic peak current increased linearly with square root of sweep rate as well as with the concentration of BTA from 3.0?×?10^?6 to 1.6?×?10^?4 mol L^?1. This suggests a diffusion-controlled and irreversible electrode process. Diffusion coefficient of BTA on MWNTs-Nafion/GCE was obtained as 2.67?×?10^?2 cm² s^?1 with four orders of magnitude larger than that on GCE. MWNTs-Nafion/GCE showed a good selectivity between BTA and O₂ but poor selectivity between BTA and tolyltriazole.     

Crystal Structure and Interaction of 6-Amino Coumarin with Nitrite Ion for Its Selective Fluorescence Detection

ABSTRACT

6-Amino coumarin has been established as an efficient nitrite ion selective fluorescent sensor. The developed method shows linearity up to 1.6 × 10^?6 mol L^?1 of nitrite ion concentration. Interference from other common anions is almost negligible. The reagent shows strong binding affinity towards nitrite ion as evident from its binding constant value (5.8 × 10⁴), estimated by Stern-Volmer method. Some real samples were analyzed. Single crystal X-ray structure of the reagent is reported. Preliminary computational studies on the molecular level interaction between the reagent and nitrite ion were performed by density functional theory (DFT, B3LYP) method.     

Volume of precursor solution effect on the properties of SnO<Subscript>2</Subscript> thin films prepared by nebulized spray pyrolysis technique

Undoped SnO₂ thin films have been deposited on amorphous glass substrates with different precursor solution volume (10, 15, 20 and 25 ml) using simple and cost-effective nebulized spray pyrolysis technique. The influence of precursor solution on structural, optical, photoluminescence and electrical properties had been studied. The X-ray diffraction spectra prove the polycrystalline nature of SnO₂ with tetragonal structure. All the films show a preferred growth orientation along (110) diffraction plane. The average transmittance of SnO₂ thin films varied between 82 and 75% in the visible as well as IR region. The band gap energy decreases from 3.74 to 3.64 eV corresponding to direct transitions with the precursor solution volume had increased from 10 to 20 ml and then increased as 3.72 eV for 25 ml. SEM pictures demonstrated polyhedrons like grains. EDX confirmed the existence of Sn and O elements in all the prepared SnO₂ thin films. Photoluminescence spectra at room temperature revealed that the four emission bands in all the samples such as sharp dominant peak at 361 nm with shoulder peak at 377 nm (UV region), a broad and low intensity peak at 492 nm (blue region) and 519 nm (green region). The electrical parameters were examined by Hall effect measurements, which demonstrated that the film prepared at 20 ml precursor solution volume possess minimum resistivity 2.76?×?10^?3 Ω-cm with activation energy 0.10 eV and maximum figure of merit 1.54?×?10^?2 (Ω/sq)^?1.