Two Highly Sensitive and Selective Colorimetric “Off-On” Rhodamine-Based Fluorescent Chemosensor for Hg(II) in Aqueous Media

Two novel rhodamine derivatives were designed and synthesized. They were successfully characterized by HR-MS, ¹H NMR and ¹³C NMR. They were found to exhibit a reversible colorimetric response and exhibit high selectivity and sensitivity for Hg(II) ion over other commonly coexistent metal ions. Their selectivity is excellent, and the detection of Hg(II) at ppb level is possible. The colorimetric and fluorescent response to Hg(II) can be conveniently detected even by the naked eye, which provides a facile method for visual detection of Hg(II).     

Influence of Copper(II) Ions on Radicals in DOPA–Melanin

DOPA–melanin (DOPA = 3,4-dihydroxyphenyl-alanine) complexes with Cu(II) cations were studied by electron paramagnetic resonance (EPR) spectroscopy. After the addition of metal cations to the melanin polymer, the EPR spectra parameters were measured. The axial g-factor values are g _|| = 2.20 and g _^ = 2.0 5 g_{ \bot } = 2.0 5 . Since $ g_{||} > g_{ \bot } > 2 $ g_{||} > g_{ \bot } > 2 , the ground state orbital of the unpaired electron of the Cu(II) complex is | x ²  -   y ² ñ \left| {{{x}}^{ 2} } \right. \, - \, \left. {{{y}}^{ 2} } \right\rangle . Square coordination of these cations in melanin is proposed. The influence of the Cu(II) concentration in solution used during synthesis on the concentration of melanin radicals was investigated. Cu(II) cations causes the decrease in the paramagnetic center concentration in melanin. The Cu(II) EPR spectra are not saturated within the microwave power range of 0.7–70 mW used in our experiment.     

Fluorescein Based Three-channel Probe for the Selective and Sensitive Detection of CO32− Ions in an Aqueous Environment and Real Water Samples

Journal of Fluorescence - We have constructed a novel fluorescein-based fluorescent chemosensor, FL-In, functionalised with an indole moiety and capable of sensing by both the optical...     

The Spectrochemical Properties of bis-(α-Methioninephosphonato)Copper(II) in Aqueous Solution

The combined results of spectrophotometric measurements and e.s.r. spectra, as well as those obtained from potentiometric titration studies, are used to determine the structure of the individual complex species formed between copper(II) ion and 1-amino-3-methylthiopropane-phosphonic acid (α-MetP) in aqueous solution. The e.s.r. parameters are typical for CuN₂O₂ coordination geometries. The d-d absorption spectrum of [Cu(α-MetP)₂]^2-chromofore in aqueous solution has been treated by the Angular Overlap Model in C_2h, symmetry. Low-symmetry splittings of the broad asymmetric absorption band in the measured spectrum were found by Gaussian analysis. The effect of the σ-and π-bonding of bidentate ligand upon the central ion d-orbital energies is destribed in a ligand-field framework.     

Highly Selective and Sensitive Colorimetric and Fluorescent Chemosensors for Rapid Detection of Cyanide Anions in Aqueous Medium: Investigation on Supramolecular Recognition of Tweezer‑shaped Salophenes

Journal of Fluorescence - Three tweezer?shaped salophenes having catechols (1), phenols (2) and anisoles (3) units in conjunction to the dipodal Schiff bases have been applied for the optical...     

A Rhodamine-Based Off�COn Fluorescent Chemosensor for Selectively Sensing Cu(II) in Aqueous Solution

A novel chromogenic and fluorogenic chemosensor RhB-pMOSal comprising a rhodamine fluorophore and a salicylaldehyde receptor being connected by an iminohydrazine link was synthesized and fully characterized. Its sensing behavior toward various metal ions in neutral aqueous solution was investigated by absorption and fluorescence spectroscopy. RhB-pMOSal exhibited a reversible and sensitive ??turn-on?? response of absorption and fluorescence toward Cu²⁺ in aqueous acetonitrile solution. Approximate 65 and 6-fold enhancement in the absorbance at 556 nm and fluorescence intensity at 573 nm were estimated when equivalent Cu²⁺ was added to the RhB-pMOSal solution. Under the same conditions, RhB-pMOSal displayed more sensitive than a reported analogue RhB-Sal to Cu²⁺ ion. The competition experiments for Cu²⁺ mixed with common metal ions exhibited no obvious change in absorption and emission except Cr³⁺ ion that can induce the fluorescence quenching of RhB-pMOSal to some extent.     

Sensitive fluorescent chemosensor for Hg(II) in aqueous solution using 4’-dimethylaminochalcone

Journal of Fluorescence - Mercury (Hg) is an element with high toxicity, especially to the nervous system, and fluorescent pigments are used to visualize dynamic processes in living cells. A little...     

Novel Glutathione-Capped Cadmium Telluride Quantum Dots-Based Off–On Fluorescence Sensor for Highly Sensitive and Selective Monitoring of Histidine

A novel glutathione-capped cadmium telluride quantum dots-based fluorescence “off–on” sensor was designed and applied for highly sensitive and selective monitoring of histidine in aqueous solution. To provide a platform for histidine detection, manganese ion was first employed as an effective quencher to decrease the fluorescence of glutathione-capped cadmium telluride quantum dots because of the binding of manganese ion to glutathione on the surface of quantum dots and the electron transfer from the photoexcited glutathione-capped cadmium telluride quantum dots to manganese ion. Due to its high binding affinity with manganese ion, histidine can make the manganese ion to be dissociated from the surface of glutathione-capped cadmium telluride quantum dots to form more stable complex with histidine in solution, and set free the luminescent glutathione-capped cadmium telluride quantum dots, thereby recovering the fluorescence of glutathione-capped cadmium telluride quantum dots. Experimental results showed that the recovered fluorescence intensity was directly proportional to the concentration of histidine in the range of 0.006 to 465.0 µg mL^?1 with a correlation coefficient (R) of 0.9977, and the detection limit (3σ/K) was 1.82 ng mL^?1. Relevant experiments also revealed that the fluorescence sensor gives excellent selectivity for histidine over other common amino acids. To further investigate perfect analysis performance, this sensor was utilized to determine histidine in synthetic samples with satisfactory results.     

A Rhodamine-Based “Off-On” Colorimetric and Fluorescent Chemosensor for Cu(II) in Aqueous and Non-aqueous Media

A new rhodamine derivative (RhB-NSal) bearing an electron-withdrawing group –NO₂ at the 5-position of 2-hydroxyphenyl moiety was synthesized and its sensing behaviors for Cu²⁺ in acetonitrile and aqueous acetate-buffer/acetonitrile (2/3, v/v, pH 4.8) media were investigated. In each medium, significant absorption and fluorescence enhancements accompanied by an instant color change from colorless to pink were observed for RhB-NSal upon addition of Cu²⁺. RhB-NSal binds with Cu²⁺ forming a 1:1 stoichiometric complex with an association constant of 6.72 (±0.03) × 10⁴ M^?1 and 4.23 (±0.03) × 10⁴ M^?1, respectively. RhB-NSal displayed high selectivity for Cu²⁺ over possibly competitive metal ions except that Fe³⁺ and Bi³⁺ ion can respectively bring about a little interference in absorption and fluorescence with its sensing for Cu²⁺. In dry acetonitrile, pronounced enhancements in the absorbance and emission of RhB-NSal were induced by Cu²⁺, with a detection limit of 0.49 μM, exhibiting higher sensitivity than that of a known analogue bearing no substituent on its phenol ring, RhB-Sal. In aqueous solution, RhB-NSal displayed likewise a high selectivity but a lower sensitivity for Cu²⁺ than that in acetonitrile, with a detection limit of 14.98 μM, still more sensitive than RhB-Sal in absorption. By virtue of these properties, RhB-NSal could be used as an “Off-On” fluorescent and colorimetric chemosensor for Cu²⁺ in acetonitrile medium, and be developed to be a promising candidate of “Off-On” eye-naked chemosensor for Cu²⁺ in a weakly acidic aqueous medium.     

Highly selective fluorescent chemosensor for detecting Hg(II) in water based on pyrene functionalized core–shell structured mesoporous silica

Novel pyrene functionalized mesoporous core–shell structured silica (denoted as SiO₂@mSiO₂/Py-Si) was designed and synthesized as a highly selective fluorescent chemosensor for detecting Hg²⁺ in water. The core–shell structured silica was prepared by a simple sol–gel process through coating SiO₂ nanospheres with a layer of ordered mesoporous silica. The surface of outer mesoporous silica shell was then further functionalized by the fluorescent chromophore alkoxysilane modified pyrene (Py-Si). XRD data confirmed that the hexagonal ordered mesoporous structure was preserved after functionalization. The chemosensing material successfully exhibited a remarkable “turn on” response toward Hg²⁺ over miscellaneous metal ions. A good linear response towards Hg²⁺ in the concentration range of 10^?8–10^?4 M was constructed with R²=0.9913. Most importantly, a satisfactory detection limit of 3.4×10^?9 g mL^?1 (down to ppb level) was obtained, which is 100 times lower than our previous report of covalently grafted Py-OH to the bulk mesoporous silica SBA-15. These results indicated that SiO₂@mSiO₂/Py-Si can be used as a highly selective and sensitive fluorescence sensor for Hg²⁺.     

Development of tBu-phenyl Acetamide Appended Thiacalix[4]arene as “Turn-ON” Fluorescent Probe for Selective Recognition of Hg(II) Ions

Journal of Fluorescence - Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix[4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour...     

IR Absorption Anisotropy of Films of Copper Phthalocyanine and Composites Based on It in the Region of γ-(CH) Oscillations

By the IR spectrophotometric method, metastable vacuum-deposited films of copper phthalocyanine and composites based on it have been investigated. For copper phthalocyanine films, an intense absorption band in the region of 729 cm^–1, which appears at oblique incidence of linearly polarized radiation with oscillations lying in the incidence plane, has been established. Its origin is associated with the features of the supermolecular architecture of polycrystalline films particular, with the character of packing of copper phthalocyanine microcrystallites.     

Wavelength–Ratiometric Probes for the Selective Detection of Fluoride Based on the 6-Aminoquinolinium Nucleus and Boronic Acid Moiety

Herein we report a set of new water-soluble fluorescent probes (N-boronobenzyl-6-aminoquinolinium bromides, BAQBAs) sensitive to aqueous fluoride. These probes shows spectral shifts and intensity changes in the presence of fluoride, in a wavelength ratiometric and colorimetric manner, enabling the detection of fluoride concentrations at visible wavelengths, in the concentration range approximately 1-300 mM. Although the sensing mechanism is different for fluoride as compared to the other halides, we have tested the utility of these probes towards the other halides, and the results reveal that the BAQBAs are in fact potential candidates towards the sensing of the all the halides, but in different concentration ranges. As the probes are based on the boronic acid moiety, which is a well-known fluoride and sugar chelator group, we have investigated the response of sugars (such as glucose and fructose, which are present in biological fluids and foodstuffs) as interferences in fluoride detection using these probes. Interestingly, the BAQBAs show a suppressed sugar response potentially allowing for the predominant fluoride sensitivity. In addition to physiological sugars, we also have assessed the response of aqueous halides as potential interferents, or indeed analytes to be sensed, and show that the new boronic acid containing probes respond well to aqueous fluoride in the presence of a high background of other species, such as in a biological cocktail of 50 mM Glucose, 50 mM aqueous Chloride and 5 mM Fructose.     

The Application of Infrared Spectra to Structural Problems in Copper(II) Complexes of 2,2′-Bipyridine

The infrared spectra of the complexes [Cu(bipy)₃] (C10₄)^2′ [Cu(bipy)₂] (C10₄)₂, [Cu(bipy)₂I]I, [cu(bipy)₂I] C10₄ and [Cu(bipy)(C10₄)₂] (bipy - 2,2′-bipyridine) are discussed in relation to their known or probable structures. Evidence for tetragonal distortion of [Cu(bipy)₃]₂₊ but not [Cu(phen)₃]₂₊ (phen = 1, 10-phenanthroline) is adduced.     

The High Sensitive and Selective “Off-On” Fluorescent Zn2+ Sensor Based on the Bis(2,4,7,8,9-pentamethyldipyrrolylmethene-3-yl)methane

A fluorescent chemosensor based on the 3,3′-bis(dipyrrin) bearing two chromophoric dipyrrin units was synthesized, which showed a strongly enhanced fluorescent intensity in the presence of Zn²⁺ ions and a high selectivity toward Zn²⁺ ions over a wide range of tested metal ions in organic solvents.     

The Historical Roots of ‘‘Foundations of Quantum Physics’’ as a Field of Research (1950–1970)

The rising interest, in the late 20th century, in the foundations of quantum physics, a subject in which Franco Selleri has excelled, has suggested the fair question: how did it become so? The current answer says that experiments have allowed to bring into the laboratories some previous gedanken experiments, beginning with those about EPR and related to Bells inequalities. I want to explore an alternative view, by which there would have been, before Bells inequalities experimental tests, a change in the views shared by physicists concerning the intellectual status of that issue. I will take three cases which will serve as the threads of our story: the connections between Bohms causal interpretation and Bells inequalities; Wigners ideas on the measurement problem; and finally Everetts relative states formulation. In the end, I will discuss how those threads were gathered together by creating foundations of quantum physics as a field of research.     

Introducing ‘Simple Variable Selection (SVS) Approach’ for Improving the Quantitative Accuracy of Chemometric Assisted Fluorimetric Estimations of Dilute Aqueous Mixtures

Excitation emission matrix fluorescence (EEMF) spectroscopy is a multiparametric fluorescence technique where the fluorescence intensity of a fluorophore is a function of excitation wavelength, emission wavelength and its concentration. The manual analysis of large volume of highly correlated EEMF data sets towards developing a calibration model for quantifying each fluorophores present in multifluorophoric mixtures is a difficult and time-consuming task. Over the years, Partial least square (PLS) algorithm has found its application towards providing swift and efficient analyses of large volumes of highly correlated spectral data sets. The PLS assisted EEMF spectroscopy has been successfully used towards quantifying the fluorophores in multifluorophoric mixtures without involving any pre-separation. However, the accuracy and robustness of developed calibration model can be significantly improved provided PLS analysis is carried out on the analytically relevant EEMF spectral variables. In the present work, a variable selection method baptized as simple variable selection (SVS) approach is introduced that provides a simple and computationally economical means of identifying the useful spectral variables for subsequent PLS analysis. The proposed SVS approach is successfully validated by analyzing the complex EEMF data sets of multifluorophoric mixtures of consisting of multifluorophoric mixtures of biological relevance. The proposed approach is found to provide a simple, swift and efficient means for developing a robust PLS assisted EEMF spectroscopy based calibration model for simultaneous quantification of various fluorophores present in multifluorophoric mixtures.     

Determination of Ofloxacin using a Highly Selective Photo Probe Based on the Enhancement of the Luminescence Intensity of Eu3+—Ofloxacin Complex in Pharmaceutical and Serum Samples

A rapid, simple and sensitive spectrofluorimetric method for determination of trace amount of ofloxacin was developed. At pH 5.1 the ofloxacin enhances the luminescence intensity of the Eu³⁺ ion in Eu³⁺- ofloxacin complex at λ_ex = 365 nm. The produced luminescence intensity of Eu³⁺-ofloxacin complex was in proportional to the concentration of ofloxacin. The working range for the determination of ofloxacin was 5.0 × 10^-9–5.0 × 10^-6 mol L^-1 with lower detection limit (LOD) and quantitative detection limit (QDL) of 3 × 10^-9 and 9 × 10^-9 mol L^-1, respectively. The enhancement mechanism of the luminescence intensity in the Eu³⁺-ofloxacin system has been also explained. The method revealed good selectivity for ofloxacin in the presence of coexisting substances and used successfully for the assay of ofloxacin in pharmaceutical preparations and serum. A comparison with other standard methods was also discussed.     

Semiempirical assignment of the electron transitions in manganese(II)-doped II–VI compounds

The electron transitions in manganese(II)-doped II–VI compounds have been assigned by the Angular Overlap Model (AOM). The extracted AOM and electron repulsion parameters are applied to assess the covalency of the respective manganese-ligand bonds. A comparison with Crystal Field Theory (CFT) is made in order to demonstrate the advantages offered by the AOM. The Dq values for Mn(II) in CdS and CdSe were found by interpolation from the Dq vs R⁻⁵_ml relation.