A New Azo-Schiff Base Dual-mode Chemosensor: Colorimetric Detection of Cobalt Ions and Fluorometric Detection of Aluminum Ions in Aqueous Ethanol Solution.

A new Azo-Schiff base ligand (H2L) was designed and synthesized as a cation chemosensor. The chemosensor H2L as dual chemosensor showed selective fluorescence recognition of Al3+ with a noticeable fluorescence enhancement and colorimetric detection of Co2 + in aqueous ethanol solution. The H2L exhibits a linear response toward Al3+ ions in the concentration range of 1.91 × 10-8 M to 4.8 × 10-6 M with a limit of detection of 1.91 × 10-8 M. The sensing mechanism of sensor H2L toward Al3+ was investigated by 1H NMR and IR spectroscopies. Fluorescence switch based on the control of EDTA and Al3+ proved H2L could act as a reversible chemosensor. The molecular structure of [NiL] complex has been determined by X-ray crystallography.

Bifunctional impedimetric sensors based on azodicarboxamide supported on modified graphene nanosheets.

Herein, gold-coated graphene oxide nanosheets hybrid material (GO/AuNPs) with exceptional physical and chemical properties has been utilized as a novel platform for electrode modification. The synthetic method of GO/AuNPs involves anon-covalent functionalization of exfoliated GO with AuNPs based on the reduction of the Au(III) complex by sodium citrate. The prepared GO/AuNPs hybrid exhibits the dispersion of high density AuNPs which were densely decorated on the large surface area of GO. The GO/AuNPs modified glassy carbon (GC) electrode was employed as a sensing platform to immobilize azodicarboxamide (ACA). The morphology, structure and electrochemical performance of the sensor were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the modified electrode has a notable bifunctional catalytic activity. Electrocatalytic oxidations of cysteine and electrocatalytic reduction of iodate at the surface of modified electrode were investigated with different technique.

A label-free aptasensor based on polyethyleneimine wrapped carbon nanotubes in situ formed gold nanoparticles as signal probe for highly sensitive detection of dopamine.

Herein, a highly sensitive and selective aptamer biosensor for quantitative detection of a model target, dopamine (DA), was developed by using a gold (Au) electrode modified with highly dispersed gold nanoparticles (AuNPs) and acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI). Amine-terminated12-mercaptureprobe (ssDNA1) as a capture probe and specific DA-aptamer (ssDNA2) as a detection probe was immobilized on the surface of a modified electrode via the formation of covalent amide bond and hybridization, respectively. Methylene blue (MB) was used as the redox probe, which was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced the MB from the electrode surface, rendering a lowered electrochemical signal attributed to decreased amount of adsorbed MB. The developed electrochemical DA aptasensor showed a good linear response to DA from 5 to 300nM with detection limit of 2.1nM. The biosensor also exhibited satisfactory selectivity and could be successfully used to detect DA in blood serum sample.

Synthesis, characterization and electrochemical study of synthesis of a new Schiff base (H2cddi(t)butsalen) ligand and their two asymmetric Schiff base complexes of Ni(II) and Cu(II) with NN'OS coordination spheres.

A novel Schiff base (H(2)cddi(t)butsalen) ligand was prepared via condensation of Methyl-2-{N-(2'-aminoethane)}-amino-1-cyclopentenedithiocarboxylate(Hcden) and 3,5-di-tert-butyl-2-hydroxybenzaldehyde. The ligand and Ni(II) and Cu(II) complexes were characterized based on elemental analysis, IR, (1)H NMR, (13)C NMR, UV-Vis spectrometry and cyclic voltammetry. The structure of copper{methyl-2-{N-[2-(3,5-di-tert-butyl-2-hydroxyphenyl)methylidynenitrilo]ethyl}amino-1-cyclopentedithiocarboxylate has been determined by X-ray crystallography. The X-ray results confirm that the geometry of the complex is slightly distorted square-planar structure. The copper(II) ion coordinates to two nitrogen atoms from the imine moiety of the ligand, a sulfur atom the methyl dithiocarboxylate moiety and phenolic oxygen atom.

[(Z)-1-({3-[(3-Amino-prop-yl)(2-nitro-benz-yl)amino]-prop-yl}imino-meth-yl)naphthalen-2-olato]copper(II) perchlorate.

In the title compound, [Cu(C(24)H(27)N(4)O(3))]ClO(4), the Cu(II) atom has a distorted square-planar coordination geometry and is surrounded by an N(3)O donor set composed of a secondary amine N, a primary amine H, an imino N and a naphthalen-2-olate O atom. An intra-molecular N-H⋯O hydrogen bond occurs. In the crystal, mol-ecules are held together by inter-molecular N-H⋯O hydrogen bonds, leading to the formation of a three-dimensional network.

1-[((E)-{2-[(2-Nitro-benz-yl)(2-{[(E)-(2-oxidonaphthalen-1-yl)methyl-idene]aza-nium-yl}eth-yl)amino]-eth-yl}aza-niumyl-idene)meth-yl]naphthalen-2-olate monohydrate.

The title Schiff base compound, C(33)H(30)N(4)O(4)·H(2)O, adopts an E configuration with respect to each C=N double bond. In the mol-ecule, there are naphthoxide anions and the protonated imino N atoms. Intra-molecular N-H⋯O hydrogen bonds lead to the formation of approximately planar (maximum deviation 0.029 Šfor H atom) six-membered rings.. In the crystal, mol-ecules are linked by O-H⋯O and N-H⋯O hydrogen bonds as well as C-H⋯O contacts, leading to the formation of a three-dimensional network.

Methyl 2-{2-[(E)-(2-hy-droxy-3-meth-oxy-benzyl-idene)amino]-ethyl-amino}-cyclo-pentene-1-carbodithio-ate.

In the title Schiff base compound, C(17)H(22)N(2)O(2)S(2), which adopts an E configuration with respect to the imine C=N double bond, the C=N and N-C bond distances are 1.2789 (16) and 1.4546 (16) Å, respectively. In the mol-ecule there are intra-molecular O-H⋯N and N-H⋯S hydrogen bonds, and the CH=N-C substituent is almost coplanar with the benzene ring [C-N-C-C torsion angle = -178.80 (11)°]. The crystal packing is stabilized by inter-molecular C-H⋯O and C-H⋯π inter-actions involving the aromatic ring.