Sudipto Dey

A highly selective and biocompatible chemosensor for sensitive detection of zinc(II)

2-Formyl-4-methyl-6-(2-benzoimidazolyliminomethyl)phenol (HL1) has been synthesized via Schiff-base condensation between 4-methyl-2,6-diformylphenol and 2-aminobenzimidazole in a 1:1 ratio in acetonitrile and characterized using elemental analysis and different spectroscopic methods. HL1 has been found to be a selective fluorescence sensor for Zn2+ ions. The emission intensity of HL1 at 528 nm in 10 mM HEPES buffer in water:methanol (1:9, v/v) (pH = 7.2) increases in the presence of Zn2+ when it is excited at 445 nm. Other metal ions can induce a slight increment or lowering of emission intensity. The spectral properties of HL1 and 2-formyl-4-methyl-6-(2-benzoimidazolylmethyliminomethyl)phenol (HL2) have been compared. It has been found that the presence of the methylene group in HL2 can have a significant effect on the absorption and fluorescence peak positions of the Schiff-base molecule and its zinc complex. Some theoretical calculations have been done to get a better view into the different spectral transitions. HL1 and HL2 have been found to be highly sensitive towards the detection of Zn2+ ions with very low LOD values. Excitation in the visible region and the effect of pH on the emission intensity of HL1 encourage us to carry out biological studies. HL1 has been used for human lung cancer cell (A549) imaging without cytotoxicity.

A quinoline based Schiff-base compound as pH sensor

A new Schiff-base compound, 1,4-bis-(quinolin-6-ylimino methyl)benzene (BQB), has been synthesized by the reaction between terephthaldehyde and 6-aminoquinoline (1 : 2 ratio) and characterized by elemental analysis and different spectroscopic methods. The Schiff-base compound, designated as BQB, undergoes protonation in acidic medium and has been designated as PBQB. PBQB shows emission intensity at 550 nm at low pH and with the increase in pH, the intensity of the peak at 550 nm decreases with simultaneous shift of the emission band to 453 nm. The intensity of the peak at 453 nm increases as pH of the medium is raised and the phenomenon is found to be reversible. Reversibility of fluorescence intensity of BQB with pH shows that the system is stable in both basic and acidic media. Absorption spectrum of the compound shows band at 380 nm with a strong shoulder at 402 nm in low pH which changes to 344 nm at higher pH region. Naked eye detection of colour change at different pH regions is possible using the probe. Position of absorption band of BQB is changed in acidic medium due to protonation of the ring nitrogen atom present in it as reflected by theoretical studies. We have applied our probe to detect the pH region of river water.

Role of inhomogeneous cation distribution in magnetic enhancement of nanosized Ni0.35Zn0.65Fe2O4: A structural, magnetic, and hyperfine study

In this paper, we report the structural, microstructural, and magnetic properties of nanosized (particle size ranging from 20 to 30 nm) Ni0.35Zn0.65Fe2O4 (MA4) system synthesized via mechanochemical route followed by annealing. The Rietveld refinement is used for the first time to precisely resolve the crystal structure of a ferrite system at nanoscale. MA4 is a cubic spinel of Fd3¯m symmetry. According to XRD and HRTEM studies, it is a well crystalline sample which possesses large microstrain. In spite of its nanometric size, MA4 has displayed some notably distinct magnetic properties like, enhancement of magnetization (64 emu g−1 at 15 K), magnetic order, magnetic ordering temperature, coercivity (1000 Oe at 15 K), magnetic anisotropy energy, and reduction of superparamagnetic relaxation compared with its counterparts synthesized by chemical route. It exhibits clear hysteresis loop (HC = 50 Oe) at 300 K and ferrimagnetic ordering below the blocking temperature (∼250 K). These improvements in magnetic pr...

Tuning magnetization, blocking temperature, cation distribution of nanosized Co0.2Zn0.8Fe2O4 by mechanical activation

The study on structural, microstructural, magnetic, and hyperfine properties of nanosized Co0.2Zn0.8Fe2O4 having particle size ∼18 nm (CZM) synthesized by high energy ball milling of Co0.2Zn0.8Fe2O4 nanoparticles of size ∼20 nm (CZ) produced by flow rate controlled coprecipitation method has revealed that the inclusion of strain induced anisotropy produced by mechanical treatment and escalation of oxygen mediated intersublattice exchange interaction of spinel ferrites by tuning cation distribution properly, can improve the magnetic quality of nanosized ferrites significantly. This upshot will be of immense help in promoting the technological application of nanostructured ferrites. The Rietveld refinement of powder x-ray diffraction pattern and the analysis of transmission electron micrographs, energy dispersive x-ray spectrum, and FTIR spectrum of the sample have confirmed that CZM is single phase cubic nanometric spinel ferrite of Fd3¯m symmetry and it possesses large microstrain within its crystal latti...

A two-pocket Schiff-base molecule as a chemosensor for Al3+

4,4′-Sulfonylbis(2-(-2-hydroxybenzylideneamino)phenol) (H4L) was synthesized by the reaction between bis-(3-amino-4-hydroxy phenyl)sulphone and salicylaldehyde (1 : 2 ratio) and has been characterized by standard methods. H4L shows a weak emission peak at 485 nm in 10 mM HEPES buffer in water : DMSO (1 : 9, v/v) (pH = 6.7) at room temperature. There is a significant enhancement in the emission intensity at 485 nm only in the presence of Al3+. Other relevant metal ions could not considerably alter its emission spectrum, indicating that H4L is a selective fluorescent probe for Al3+. H4L forms a complex with Al3+ in a 1 : 2 ratio, as is evident from Jobs analysis and mass spectral data. There is a significant increase in the quantum yield and lifetime of the probe upon complex formation with aluminum. The limit of detection has been determined and shows moderate sensitivity towards the metal ion. A pH dependent study indicated that the emission intensity of H4L increases sharply when the pH of the medium is more than 7. The emission intensity of H4L in the presence of one equivalent of Al3+ starts increasing when the pH is ∼5.0. Thus, all the spectral studies were performed at pH 6.7. Some theoretical calculations were performed to investigate the spectral transitions. H4L was used for the identification of Al3+ using sea water.

A highly sensitive non-enzymatic hydrogen peroxide and hydrazine electrochemical sensor based on 3D micro-snowflake architectures of α-Fe2O3

In the present work, well crystalline 3D micro-snowflake structured α-Fe2O3 has been successfully synthesized on a large scale via a simple hydrothermal reaction by hydrolysis of a K3Fe(CN)6 precursor. The structure, composition, purity and morphology of the synthesized α-Fe2O3 samples are examined using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and Mossbauer spectroscopy. The FESEM and TEM images reveal that the sample exhibits a micro-snowflake like shape having six-fold symmetry with symmetric branching along each arm consisting of a long central trunk and secondary branches. The 3D micro-snowflake structured α-Fe2O3 embedded ITO electrode exhibits high selectivity and sensitivity for electrochemical probing of hydrogen peroxide (H2O2) and hydrazine (N2H4) with a very low detection limit in a wide linear range. Amperometric measurements show a sensitivity of 7.16 μA mM−1 cm−2 in a wide linear range from 0.1 to 5.5 mM with the lowest detection limit of 0.01 mM (S/N = 3) towards H2O2 sensing. The sample also exhibits a sensitivity of 24.03 μA mM−1 cm−2 in the linear range between 50 μM and 1340 μM with the lowest detection limit of 5 μM towards hydrazine detection. The excellent electrochemical activity of the sample is rendered to the presence of a large number of catalytic sites in the sample due to its 3D micro-snowflake like architecture. Good reproducibility, stability and selectivity suggest its suitability for the fabrication of H2O2 and hydrazine sensors.

Crystal Structure and Conformation of 2-{(2′-Aminobenzyl)iminoethyl}- 5-methoxyphenol

Abstract The Schiff base, 2-{(2′-aminobenzyl)iminoethyl}-5-methoxyphenol, 1,2 -C6H4[NH2-2 ʹ]-CH2N=CHC6H3(OMe-5)OH (I), has been prepared by the reaction of 2 -amino-1-benzylamine and 2-hydroxy-4-methoxyacetophenone in methanol. The molecular structure has been confirmed by single crystal X-ray crystallography (triclinic, space group P 1̄, a = 7.201(2), b = 9.802(2), c = 9.993(2) Å, α = 83.09(2), β = 73.49(2), γ = 84.09(2)°, R = 0.0415 for 2611 independent reflections). The 1H and 13C NMR spectra in CDCI3 solution indicate the formation of some other minor conformations or dissociation in solution. The title compoundois not planar. Intramolecular hydrogen bonding occurs between O(1) and N(1) atoms [2.528(2) Å], the hydrogen atom essentially being bonded to the nitrogen atom. Minimum energy conformations from AMI were calculated as a function of four torsion angles. The optimized geometry of the molecular structure corresponding to the non-planar conformation is the most stable conformation in all calculations. The results strongly indicate that the minimum energy conformation is primarily determined by non-bonded hydrogen-hydrogen repulsions.

Mechanical Milling Induced Improvement In Magnetic Property Of Nanosized Ni0.35Zn0.65Fe2O4: A Hyperfine Characterization

The magnetic properties of nano‐sized Ni0.35Zn0.65Fe2O4 prepared by high‐energy ball milling have been investigated using dc magnetization. The study on relaxation dynamics of the system using Mossbauer spectroscopy is also reported. The Mossbauer spectrum at 300 K exhibits hyperfine split sextet and a superparamagnetic behaviour has been observed at 500 K. The sample has shown enhancement in magnetization, magnetic hyperfine field and anisotropy energy, which appears to be unusual according to core‐shell model. The results indicate that at 300 K the spontaneous reversal of magnetization vector owing to superparamagnetic relaxation of nanoparticles has reduced significantly due to the increase in anisotropy energy. These properties could be profitably used to conquer the inherent instability of magnetic nanoparticles.