A simple pyridine based fluorescent chemosensor for selective detection of copper ion

A feasibly constructed novel pyridine based receptor (S) has been reported for the selective detection of copper ion over other metal ions. The metal sensing ability of receptor with diverse metal ions were studied by colorimetry, absorption and emission spectroscopic systems in CH₃CN/H₂O (7:3, v/v). This receptor reveals a drastic color converts from vapid to yellow and cyan under normal light and UV light with copper ion. Further, S-Cu²⁺ complex exhibits new UV-Visible band at 419 nm and intense fluorescence band at 494 nm upon the excitation at 388 nm. The stoichiometric binding ratio of receptor with metal ion was confirmed with Job's method and ESI-Mass also further supported the complexation. Besides, limits of detection of Cu²⁺ were calculated to be 0.25 μM. The limiting capacity of receptor with Cu²⁺ ion was additionally explored by quantum chemical calculation. Moreover, this receptor was effectively utilized for the measurement of Cu²⁺ ion in various water tests.

Surface and morphology analyses, and voltammetry studies for electrochemical determination of cerium(iii) using a graphene nanobud-modified-carbon felt electrode in acidic buffer solution (pH 4.0 ± 0.05)

Trace determination of radioactive waste, especially Ce³⁺, by electrochemical methods has rarely been attempted. Ce³⁺ is (i) a fluorescence quencher, (ii) an antiferromagnet, and (iii) a superconductor, and it has been incorporated into fast scintillators, LED phosphors, and fluorescent lamps. Although Ce³⁺ has been utilized in many industries due to its specific properties, it causes severe health problems to human beings because of its toxicity. Nanomaterials with fascinating electrical properties can play a vital role in the fabrication of a sensor device to detect the analyte of interest. In the present study, surfactant-free 1,8-diaminonaphthalene (DAN)-functionalized graphene quantum dots (DAN-GQDs) with nanobud (NB) morphology were utilized for the determination of Ce³⁺ through electrochemical studies. The working electrode, graphene nanobud (GNB)-modified-carbon felt (CF), was developed by a simple drop-coating method for the sensitive detection of Ce³⁺ in acetate buffer solution (ABS, pH 4.0 ± 0.05) at a scan rate of 50 mV s⁻¹ using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. CV and DPV studies validated the existence of distinctive peaks at approximately +0.20 and +0.93 V (vs. SCE), respectively, with a limit of detection of approximately 2.60 μM. Furthermore, electrochemical studies revealed that the GNB-modified-CF electrode was (i) stable even after fifteen cycles, (ii) reproducible, (iii) selective towards Ce³⁺, (iv) strongly pH-dependent, and (v) favored Ce³⁺ sensing only at pH 4.0 ± 0.05. Impedance spectroscopy results indicated that the GNB-modified-CF electrode was more conductive (1.38 × 10⁻⁴ S m⁻¹) and exhibited more rapid electron transfer than bare CF, which agrees with the attained Randles equivalent circuit. Microscopy (AFM, FE-SEM, and HR-TEM), spectroscopy (XPS and Raman), XRD, and energy-dispersive X-ray (EDX) analyses of the GNB-modified-CF electrode confirmed the adsorption of Ce³⁺ onto the electrode surface and the size of the electrode material. Ce³⁺ nanobuds increased from 35–40 to 50–55 nm without changing their morphology. The obtained results provide an insight into the determination of Ce³⁺ to develop an electrochemical device with low sensitivity.

GNB-modified – CF electrode was utilized to determine Ce³⁺ with LoD ca. 2.60 μM.

Spectroscopic, nonlinear optical and quantum chemical studies on Pyrrolidinium p-Hydroxybenzoate--a phase matchable organic NLO crystal

Good quality and bulk single crystals of Pyrrolidinium p-Hydroxybenzoate (PYPHB), a newly identified nonlinear optical material, were grown for the first time. It crystallizes in monoclinic system with an acentric space group Cc. The molecular structure including carbon, proton positions and functional groups has been confirmed through nuclear magnetic resonance and Fourier transform infrared spectra. Its transmission window has been observed for UV-VIS-NIR region along with its theoretical limit. The photoluminescence behavior has been observed by exciting the crystal at 310 nm. The principal refractive indices and second order NLO coefficient of PYPHB are determined by Mach-Zehnder interferometer and Maker-Fringe experiments respectively. The coherence length and phase-matchablility of PYPHB crystals are measured to explore its efficacy towards device fabrications. The dipole moment, polarizability and molecular orbital energy of an isolated PYPHB molecule have also been calculated theoretically and the results are found to corroborate the experimental values.

Reactive intermediates in oxygenation reactions with mononuclear nonheme iron catalysts

An advanced intermediate: A nonheme iron(IV) oxo complex [Fe(IV)(O)(bqen)(L)](n+) (bqen = N,N'-dimethyl-N,N'-bis(8-quinolyl)ethane-1,2-diamine, L = CH(3)CN or CF(3)SO(3)(-)) activates the C-H bonds of alkanes and alcohols by a hydrogen-atom abstraction mechanism. The catalytic oxidation of these species is proposed to occur through a nonheme iron(V) oxo species, with a high reactivity in oxidation reactions (see picture).

A highly efficient non-heme manganese complex in oxygenation reactions

A non-heme manganese(II) complex shows a high catalytic activity in the epoxidation of olefins by iodosyl benzene and in the oxidation of olefins, alcohols and alkanes by peracetic acid; a mechanism involving metal-based oxidants is proposed for the oxidation reactions.

Oxidative N-Dealkylation Reactions by Oxoiron(IV) Complexes of Nonheme and Heme Ligands

Nonheme and heme iron monooxygenases participate in oxidative N-dealkylation reactions in nature, and high-valent oxoiron(IV) species have been invoked as active oxidants that effect the oxygenation of organic substrates. The present study describes the first example of the oxidative N-dealkylation of N,N-dialkylamines by synthetic nonheme oxoiron(IV) complexes and the reactivity comparisons of nonheme and heme oxoiron(IV) complexes. Detailed mechanistic studies were performed with various N,N-dialkylaniline substrates such as para-substituted N,N-dimethylanilines, para-chloro-N-ethyl-N-methylaniline, para-chloro-N-cyclopropyl-N-isopropylaniline, and deuteriated N,N-dimethylanilines. The results of a linear free-energy correlation, inter- and intramolecular kinetic isotope effects, and product analysis studied with the mechanistic probes demonstrate that the oxidative N-dealkylation reactions by nonheme and heme oxoiron(IV) complexes occur via an electron transfer-proton transfer (ET-PT) mechanism.