Parimal Paul

One pot synthesis of water-dispersible dehydroascorbic acid coated Fe3O4 nanoparticles under atmospheric air: Blood cell compatibility and enhanced magnetic resonance imaging

Water dispersible and biologically important molecule dehydroascorbic acid (DHA, capable to cross the blood brain barrier) coated Fe3O4 superparamagnetic nanoparticles having an average size of ∼6 nm were synthesized through one pot aqueous coprecipitation method under atmospheric air. An antioxidant ascorbic acid (AA) used in the synthesis oxidized itself to dehydroascorbic acid (DHA) to consume dissolved or available oxygen in reaction mixture which died away the oxidative impact of atmospheric air and formed DHA encapsulated the Fe3O4 nanoparticles which stabilized the Fe3O4 nanoparticles and significantly enhanced their colloidal solubility in water. Fe3O4 phase, superparamagnetic property, DHA coating and stable colloidal solubility in water were confirmed by means of XPS, VSM, IR and zeta potential analysis respectively. T1, T2 and T2(∗) weighted magnetic resonance imaging (MRI) and corresponding relaxivity (r1=0.416, r2=50.28 and r2(∗)=123.65 mM(-1) and r2/r1=120.86, r2(∗)r1=297.23) of colloidally dispersed DHA-coated nanoparticle water phantom revealed a strong contrast enhancement in T2 and T2(∗) weighted images. The compatibility of DHA-coated Fe3O4 nanoparticles toward human blood cells was examined by means of cell counting and cell morphological analysis with the use of optical microscope and scanning electron microscope imaging.

Cation-induced fluorescent excimer emission in calix[4]arene-chemosensors bearing quinoline as a fluorogenic unit: experimental, molecular modeling and crystallographic studies

A number of calix[4]arene-based fluorescent chemosensors containing amide as a binding site and quinoline as a fluorogenic unit have been synthesised and characterized by a single crystal X-ray diffraction study. These compounds have been designed with variations in conformation and steric crowding in the calix moiety to investigate its effect on ion selectivity and thereby on excimer emission. The ion-binding property of these fluoroionophores has been investigated with a large number of cations and anions and the ion-recognition event was monitored by luminescence, UV-Vis and 1H NMR (for anions) spectral changes. Out of a large number of cations, Hg2+, Pb2+, Fe3+ and Cu2+ exhibited strong complexation with all of the ionophores, as evident from luminescence and UV-vis spectroscopy. In the case of anions, F− and HSO4− exhibited strong complexation with two of the ionophores, as shown by fluorescence and NMR spectroscopy. Interestingly, complexation with metal ions resulted in a new band at lower energy due to excimer emission, which was not observed for anions. The binding constants for all of the three fluoroionophores with strongly interacting ions have been determined from fluorescence, UV-vis and NMR titration data. The DFT calculations for all of the three compounds were performed and the results show that the modulation of frontier molecular orbital energies upon complexation of metal ions causes the fluorescent excimer emission.

Enhanced photocatalytic performance of morphologically tuned Bi2S3 NPs in the degradation of organic pollutants under visible light irradiation

Here in, morphologically tuned Bi2S3 NPs were successfully synthesized from a single-source precursor complex [Bi(ACDA)3] [HACDA=2-aminocyclopentene-1-dithiocarboxylic acid] by decomposing in various solvents using a simple solvothermal method. The as-obtained products were characterized by XRD, TEM, UV-vis spectroscopy and BET surface area measurements. Structural analyses revealed that the as-prepared Bi2S3 NPs can be tuned to different morphologies by varying various solvents and surfactants. The interplay of factors that influenced the size and morphology of the nanomaterials has been studied. Moreover, mastery over the morphology of nanoparticles enables control of their properties and enhancement of their usefulness for a given application. These materials emerged as a highly active visible light-driven photocatalyst towards degradation of methylene blue dye and the efficiencies are dependent on size and surface area of the NPs. In addition, photocatalytic degradation of highly toxic dichlorodiphenyltrichloroethane was studied using synthesized Bi2S3 NPs as catalyst and the rate of degradation has been found to be much better compared to that exhibited by commercial WO3. We believe that this new synthesis approach can be extended to the synthesis of other metal sulfide nanostructures and open new opportunities for device applications.

Enhanced photocatalytic activity of Eu-doped Bi2S3 nanoflowers for degradation of organic pollutants under visible light illumination

Europium (Eu)-doped Bi2S3 nanoparticles (NPs) with different Eu contents were successfully synthesized by solvothermal decomposition of the precursor complexes Bi(ACDA)3 and [Eu(ACDA)3·H2O] [ACDA = 2-aminocyclopentene-1-dithiocarboxylic acid] in ethylenediamine (EN). The precursors were characterized by usual techniques such as UV-vis and FT-IR spectroscopy, and CHN and TGA analyses. The prepared nanomaterials were characterized by XRD, EDX, SEM and TEM analyses. The XRD results demonstrate that the particles were highly crystallized. The TEM images ascertain the NPs to be of flower-like structure consisting of ultrathin nanoplates with an average diameter of 9–10 nm. Photocatalytic efficiency of the Eu-doped Bi2S3 NPs was evaluated by monitoring the degradation of methylene blue (MB) in aqueous solution under visible light. It was observed that the rate of photocatalytic degradation of MB increases with an increase in the amount of the dopant ion. In addition, the photocatalytic degradation of various toxic organic pollutants such as phenol, p-cresol, 4-chlorophenol, 4-tert-butylphenol, 2,5-dimethylphenol and 2,6-di-tert-butyl-p-cresol was carried out with doped NPs in visible light. Under identical conditions, the degradation rate of 4-chlorophenol is higher than the corresponding phenol, p-cresol and 4-tert-butylphenol. Finally, the mechanism of the degradation pathway for phenol and the substituted phenols is discussed.

A novel amperometric biosensor for hydrogen peroxide and glucose based on cuprous sulfide nanoplates

A facile, greener and template free route has been developed to produce cuprous sulfide (Cu2S) nanoplates (NPs) with average diameters of 70-150 nm, via one step solvothermal decomposition of a single-source precursor (SSP) Cu(ACDC)2 [ACDC = 2-aminocyclopentene-1-dithiocarboxylate] in the presence of ethylenediamine (EN) and triethylenetetramine (TETA) as structure orienting agents. The precursor complex and nanomaterials were thoroughly characterized by several common techniques and measurements, which give the composition and characteristics of the materials. Amperometric biosensors for hydrogen peroxide (H2O2) and glucose have been constructed by immobilizing the synthesized Cu2S NPs in glutaraldehyde on a glassy carbon (GC) electrode using a direct drop-coating method. The proposed sensor has displayed faster response, high and reproducible sensitivity (64.27 μA mM-1) with linear range of 10 μM to 3.75 mM, towards the electrochemical biosensing of H2O2 at -0.35 V (vs. Ag/AgCl). The sensor also showed high and reproducible sensitivity (61.67 μA mM-1) towards glucose determination with linear range of 10 μM to 3.1 mM. The anti-inference ability of electroactive molecules and favorable stability are some of the advantages of the proposed sensor. Finally, using the sensor we have determined the glucose concentration in a human blood serum sample. The results strongly demonstrate the usefulness of Cu2S NPs for biosensor design and other biological applications.

Colorimetric detection of Cu2+ and Pb2+ ions using calix[4]arene functionalized gold nanoparticles

Abstract.Calixarene functionalized gold nanoparticles (CFAuNPs) have been prepared and characterized by spectroscopic and microscopic (TEM) techniques. To use this material as potential colorimetric sensor, the binding property of this new material has been investigated with a large number of metal ions. It exhibited sharp colour change from dark brown to green and blue, detectable by naked-eye, in the presence of Cu2+ and Pb2+ ions, respectively. It has also triggered substantial change in surface plasmon resonance (SPR) band of the functionalized gold nanoparticles, which in case of Pb(II) is due to the inter particle plasmon coupling arising from the metal-induced aggregation of the nanoparticles and for Cu(II), it is because of the formation of AuCu alloy due to anti-galvanic exchange. The size and aggregation of the nanoparticles are confirmed from HRTEM images, elemental analysis and the line profiling for both the metal ions have been done by STEM-EDX analysis. Graphical AbstractCalixarene functionalized gold nanoparticles have been prepared, which detect Cu2+ and Pb2+ ions with visible colour change. For Pb(II), the colour change is due to metal-induced aggregation of the nanoparticles and for Cu(II), it is due to formation of Au–Cu alloy.

Synthesis and reactions of cyclopalladated compounds derived from N,N′-dialkylbenzene-1,3-dicarbaldimines [alkyl = ethyl (H2L1), butyl or octyl] and N,N′-dibenzylbenzene-1,3-dicarbaldimine. Crystal structure of [Pd2L1(py)4][ClO4]2(py = pyridine)

The reactions of N,N′-dialkylbenzene-1,3-dicarbaldimines (alkyl = Et, H2L1; Bu, H2L2 or C8H17, H2L3) and N,N′-dibenzylbenzene-1,3-dicarbaldimine (H2L4) with Pd(O2CMe)2 have been studied. In all cases tetra-µ-acetato cyclopalladated compounds, [Pd4L2(O2CMe)4], were obtained in which metallation had occurred at the 4,6 positions of the benzene ring. The µ-chloro analogues, [Pd4L2Cl4], can be obtained either by reaction of the Schiff bases with Li2[PdCl4] or by metathesis of the acetato complexes. Bridge-splitting reactions of [Pd4L2Cl4] with pyridine(py), 4-methylpyridine, pyrazole, 3,5-dimethylpyrazole, amines, and a number of monoprotic bidentate chelating ligands, viz. acetylacetone, dibenzoylmethane and its monothio analogue, ethylacetoacetate, salicylaldehyde, N-methylsalicyiideneimine and sodium N,N′-dipropyldithiocarbamate have also been investigated. The products have been characterized by 1H 13C NMR spectroscopy. The X-ray crystal structure of [Pd2L1(py)4][ClO4]2 has been determined which crystallizes in the triclinic space group P with a= 10.889(1), b= 16.981(2), c= 10.227(1)A, α= 92.99(1), β= 93.14(1), γ= 73.65(1)° and Z= 2; refinement led to R= 0.059 and R′= 0.062 using 3620 unique reflections with I > 3σ(I).

Calixarenes: Versatile molecules as molecular sensors for ion recognition study

AbstractThis article presents a brief account on designing of calixarene-based molecular sensor for recognition of various metal ions and anions and also different analytical techniques to monitor the recognition event. This review focuses only on calix[4]arene derivatives, in which mainly the lower rim is modified incorporating either crown moiety to make calix–crown hybrid ionophore to encapsulate metal ions or some fluoregenic inorganic and organic moieties to use it as signalling unit. In order to investigate effect of conformation of the calixarene unit and steric crowding on ion selectivity, designing of these molecules have been made using both the cone and 1,3-alternate conformations of the calixarene unit and also incorporating bulky ter-butyl group in few cases to impose controlled steric crowding. Among various ions, here focuses are mainly on biologically and commercially important alkali metal ion such as K + , toxic metal ions such as Hg2 + , Pb2 + , Cd2 + , important transition metal ion such as Cu2 +  and toxic anion like F − . The techniques used to monitor the recognition event and also to determine binding constants with strongly interacting ions are fluorescence, UV-vis and 1H NMR spectroscopy. Most of the ionophores reported in this review have been characterized crystallographically, however no structural information (except one case) are incorporated in this article, as it will occupy space without significant enhancement of chemistry part. Different factors such as size of the ionophore cavity, size of metal ion, coordination sites/donor atoms, steric crowding and solvents, which determine selectivity have been discussed. Response of ion recognition process to different analytical techniques is another interesting factor discussed in this article. Graphical AbstractIon-recognition property of a large variety of calix[4]arenes incorporating crown moiety to make hybrid ionophore, substituents to impose steric crowding and fluoregenic moieties as signalling unit has been reported. This report demonstrates how factors such as sizes of the ionophore and metal ions, donor atoms, steric crowding and solvents, influence ion-selectivity.

Colorimetric and fluorogenic recognition of Hg2+ and Cr3+ in acetonitrile and their test paper recognition in aqueous media with the aid of rhodamine based sensors.

Two new rhodamine derivatives (L1 and L2) were synthesized, characterized and their ion recognition property has been investigated. Both of the ionophores exhibit colorimetric and fluorogenic response for Hg2+ and Cr3+ ions among large number of alkali, alkaline earth and transition metal ions tested in acetonitrile. Detail studies on determination of binding constant, binding mode, reversibility of binding, lower detection limit have been carried out. Detection of metal ions in aqueous media has also been demonstrated by preparation of simple, convenient and disposable test paper sensors with two approaches viz. filter paper and membrane filter loaded with these ionophores. Both of these methods responded sharply to both the metal ions (Hg2+ and Cr3+) in aqueous solution, detectable by bared-eye. For better sensing at low concentration of metal ions, reprecipitation followed by filtration enrichment of ligands on membrane filter was employed.

Effect of steric crowding on ion selectivity for calix-crown hybrid ionophores: experimental, molecular modeling and crystallographic studies

A number of calix[4]arene-azacrowns with variation in ring size and substituents at the upper and lower rims have been synthesized to investigate the effect of steric crowding towards ion selectivity. The structural elucidation of these ionophores has been carried out mainly by 1H NMR and ES-MS in solution and by single crystal X-ray study in the solid state. Interaction of these ionophores with a large number of cations has been investigated by NMR studies. The ionophore with tert-butyl at the upper rim (3) exhibits selectivity towards Na+ only whereas an ionophore of the same size but without tert-butyl at the upper rim (1) shows selectivity towards both Na+ and K+. An ionophore of the same size but with three tosyl substituents at the lower rim (4) exhibits no complexation with any cation. The ionophore with the larger crown ring and without tert-butyl at the upper rim (2) exhibits complexation with K+, Rb+, Ba2+ and weak interaction with Na+. Binding constants with these metal ions have been determined by NMR titration. Molecular modeling studies performed by a molecular mechanics force field (MMFF94) using the Monte Carlo search method and DFT calculations predicted the observed higher selectivity for sterically crowded receptor.