Pyrene-Hydrazone-π···Hole Coupled Turn-on Fluorescent and Naked- Eye Colorimetric Sensor for Cyanide: Role of Homogeneous π-Hole Dispersion in Anion Selectivity

A pyrene based probe associated with π···hole – hydrazone as one of the recognizing elements is synthesized and its turn in to a selective colorimetric and turn-on fluorescent sensor, (L³) for cyanide anion. This chemo sensor show high selectivity towards cyanide anion through photo electron transfer (PET) mechanism. The binding strength and sensitivity of the chemo sensor L³ towards cyanide are found to be 2.0 X 10⁴, and 4.44 x 10^-4 respectively. We have compared this high selectivity of the receptor towards cyanide, with our previously reported receptors L¹ and L². The detailed UV-Vis, Emission, ¹H-NMR, IR spectroscopic and Molecular Electrostatic Potential (MEP) studies reveals that the homogeneous π···hole dispersion in the aromatic ring governing the selectivity of the receptor towards cyanide anion. Such a positive π···hole homogeneous dispersion is missing in the case of sensor L², instead we have polarized π···hole dispersion towards 2^nd and 4^th position of di-nitrophenyl chromophoric unit in L².

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Resonantly enhanced off-specular X-ray scattering from polymer/polymer interfaces<Superscript>⋆</Superscript>

We have used measurements of the absolute intensity of diffuse X-ray scattering to extract the interfacial tension of a buried polymer/polymer interface. Diffuse scattering was excited by an X-ray standing wave whose phase was adjusted to have a high intensity at the polymer/polymer interface and simultaneously a node at the polymer/air interface. This method permits the capillary-wave-induced roughness of the interface, and hence the interfacial tension, to be measured independently of the polymer/polymer interdiffusion.     

Insect growth regulatory activity of carvacrol-based 1,3,4-thiadiazoles and 1,3,4-oxadiazoles

Abstract 

In designing of novel insect growth regulators (IGRs), biologically occurring carvacrol has been structurally modified to thiadiazole and oxadiazole moieties. Two series of carvacrol analogs containing 1,3,4-thiadiazole (VIIIa–e) and 1,3,4-oxadiazole (IXa–e) derivatives are designed and synthesized. Their structures are confirmed by FT-IR, \(^{1}\text {H}\) NMR, \(^{13}\)C NMR and LC-MS. IGR activity is tested against Spodoptera litura. Several analogs displayed IGR activity against this insect pest. Compounds VIIIe and IXe displayed relatively good IGR activity with \(\text {GI}_{50 }\)values 117.43 and 108.83 ppm against Spodoptera litura, respectively.

Graphical Abstract

Synthesis, characterization and evaluation of carvacrol-based 1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives as potent insect growth regulators (IGRs).

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Absence of morphotropic phase boundary effects in BiFeO<Subscript>3</Subscript>–PbTiO<Subscript>3</Subscript> thin films grown via a chemical multilayer deposition method

We report an unusual behavior observed in (BiFeO₃)_1−x –(PbTiO₃) _x (BF–xPT) thin films prepared using a multilayer chemical solution deposition method. Films of different compositions were grown by depositing several bilayers of BF and PT precursors of varying BF and PT layer thicknesses followed by heat treatment in air. X-ray diffraction showed that samples of all compositions show mixing of two compounds resulting in a single-phase mixture, also confirmed by transmission electron microscopy. In contrast to bulk compositions, samples show a monoclinic (M_A-type) structure suggesting disappearance of the morphotropic phase boundary (MPB) at x=0.30 as observed in the bulk. This is accompanied by the lack of any enhancement of the remanent polarization at the MPB, as shown by the ferroelectric measurements. Magnetic measurements showed an increase in the magnetization of the samples with increasing BF content. Significant magnetization in the samples indicates melting of spin spirals in the BF–xPT films, arising from a random distribution of iron atoms. Absence of Fe²⁺ ions was corroborated by X-ray photoelectron spectroscopy measurements. The results illustrate that thin film processing methodology significantly changes the structural evolution, in contrast to predictions from the equilibrium phase diagram, besides modifying the functional characteristics of the BP-xPT system dramatically.     

Growth,optical, mechanical and electrical studies of nonlinear optical crystal: l-Valinium oxalate

l-Valinium oxalate (LVO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV–vis–NIR spectrum. The microhardness studies reveal the mechanical strength of the grown crystal. The dielectric constant, dielectric loss and AC conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.     

Structural, magnetic, magnetocaloric and magnetotransport properties in Ge doped Ni-Mn-Sb Heusler alloys

The effect of Ge substitution on the magnetic, magnetocaloric and transport properties of Ni₄₅Co₅Mn₃₈Sb_12−xGe_x (x=0-3) has been investigated. The decrease in the exchange interaction brought by Ge substitution can be seen from the reduction in the magnetization of austenite phase and the increase in the martensitic transition temperature. The magnetocaloric effect and the magnetoresistance values are found to be quite sensitive to small changes in Sb/Ge ratio. Taking into account various properties, the present series seems to be a promising multifunctional system.     

Thickness induced structural changes in polystyrene films

Changes to the structure of polystyrene melt films as measured through the spectrum of density fluctuations have been observed as a function of film thickness down to the polymer radius of gyration (Rg). Films thicker than 4Rg show bulklike density fluctuations. Thinner films exhibit a peak in S(q) near q=0 which grows with decreasing thickness. This peak is attributed to a decreased interpenetration of chains resulting in an enhanced compressibility. Measurements were made using small angle x-ray scattering in a standing wave geometry designed to enhance scattering from the interior of the film compared to interface scattering.     

Large force fluctuations in a flowing granular medium

We study fluctuations in the force at the boundary of a 2D granular flow. The forces are mainly impulsive at all flow rates. The probability distribution of impulses decays exponentially at large impulses, as do the forces in a static granular medium. At small impulses, the distribution evolves continuously with flow rate with no indication of the transition from collisional flow to intermittently jamming flows. However, the distribution of the time interval between collisions tends to a power law, P(tau) - tau(-3/2), showing a clear dynamical signature of the approach to jamming.     

Electronic structure and optical properties of the HoCoSi and ErNiSi compounds

The electronic structure and the optical properties of the HoCoSi and ErNiSi compounds are studied. Spin-polarized band calculations are performed in the local electron density approximation corrected for the strong electron–electron interactions in the 4f shell of a rare-earth ion (LSDA + U method [11]). The optical constants are measured by ellipsometry in a wide wavelength range, and the frequency dependences of a number of spectral parameters are determined. The calculated densities of states are used to interpret the structural features of the interband optical conductivities of the intermetallic compounds.