Sensitization of uranium fluorescence using 2,6-pyridinedicarboxylic acid: Application for the determination of uranium in the presence of lanthanides

The 2,6-pyridinedicarboxylic acid (PDA) has been shown to efficiently sensitize and enhance the fluorescence of uranium in aqueous medium. Interestingly, this ligand stabilizes the UO₂²⁺ species, which without the ligand is known to be in a negligible concentration, in aqueous medium at pH 6. The ligand sensitized enhancement of UO₂²⁺ fluorescence by PDA, provides an analytical tool for the determination of uranium at trace levels, in aqueous medium. Furthermore, PDA is also known to enhance the fluorescence of lanthanides; consequently, the simultaneous determination of uranium and lanthanides, using PDA as a fluorescence sensitizing agent, becomes a possibility, which has been demonstrated in this work. We have shown that the use of PDA yields detection limits of 2.2×10⁻⁷ M for UO₂²⁺, 1×10⁻⁸ M for Tb³⁺ and 5×10⁻⁹ M for Eu³⁺ in the simultaneous determination of these analytes.     

Domain Wall with Strange Quark Matter in Kaluza-Klein Type Cosmological Model

In this study we have analyzed the Kaluza-Klein type Robertson Walker (RW) cosmological model by considering variable cosmological constant term Λ of the form: , and Λ∼ρ in the presence of strange quark matter with domain wall. The various physical aspects of the model are also discussed.     

Protective effect of Rubia cordifolia on reserpine-induced orofacial dyskinesia

In this study, the neuroprotective potential and in vivo antioxidant status of extract of roots and rhizomes of Rubia cordifolia L (MERC) in reserpine-induced orofacial dyskinesia was studied. Reserpine (1 mg/kg, s.c.) on day 1, 3 and 5 was used to induce orofacial dyskinesia. At the end of treatment schedule, MERC significantly inhibited reserpine-induced vacuous chewing movements, tongue protrusions, orofacial bursts, catalepsy. MERC significantly increased locomotion and rearing in open field test. MERC exhibited significant elevation in the levels of superoxide dismutase, catalase, glutathione reductase and inhibition of lipid peroxidation in forebrain region, compared with the reserpine treated group. It significantly elevated dopamine levels in the forebrain region. GCMS revealed the presence of anthraquinones, having strong antioxidant activity. It is concluded that oxidative stress might play an important role in reserpine-induced abnormal oral movements and MERC significantly protected animals against reserpine-induced orofacial dyskinesia and has great potential in treatment of neuroleptic induced orofacial dyskinesia.     

Estimation of capsaicin through scanning densitometry and evaluation of different varieties of capsicum in India

Capsicum annuum L. (family: Solanaceae) possesses therapeutic benefits for the treatment of rheumatism, neuropathy, psoriasis, flatulence and so on. In this study fruits of four different varieties of C. annuum from four different geographical regions in India were evaluated based on their total content of capsaicin. Ethanol extracts of the fruits were used. HPTLC plates were developed in a mobile phase containing benzene, ethyl acetate and methanol (75:20:5). Densitometric scanning was performed at a wavelength of 283 nm in the absorbance mode. The calibration curve was described by the equation Y=393.587+3.836*X with a correlation coefficient (r) of 0.99890. The content of capsaicin in Nagaland, Manipur, West Bengal and Shimla varieties was found to be 3.71%, 1.78%, 0.54% and 0.06%, respectively. The developed densitometric method was found to be specific, accurate and precise. A recovery study and precision showed low levels of %RSD values. The linearity range of the curve for capsaicin was found to be 300-900 ng per spot. The limit of detection and the limit of quantification values were determined to be 31 and 94 ng, respectively, proving the sensitivity of the method. Thus the method can be used to control the total content of capsaicin on an industrial scale.     

Guest-responsive reversible swelling and enhanced fluorescence in a super-absorbent, dynamic microporous polymer

A swell idea! The guest-responsive reversible swelling and fluorescence enhancement of a dynamic, microporous polymer network is presented. Guest-induced breathing of hydrophobic pores imparts multi-functional properties, such as super-absorbency, phase-selective swelling of oil from water and encapsulation of C(60) (see figure), to this soft micro-porous organic polymer.     

Fixation of carbon dioxide by macrocyclic lanthanide(III) complexes under neutral conditions producing self-assembled trimeric carbonato-bridged compounds with μ3-η2:η2:η2 bonding

A series of mononuclear lanthanide(III) complexes [Ln(LH(2))(H(2)O)(3)Cl](ClO(4))(2) (Ln = La, Nd, Sm, Eu, Gd, Tb, Lu) of the tetraiminodiphenolate macrocyclic ligand (LH(2)) in 95 : 5 (v/v) methanol-water solution fix atmospheric carbon dioxide to produce the carbonato-bridged trinuclear complexes [{Ln(LH(2))(H(2)O)Cl}(3)(μ(3)-CO(3))](ClO(4))(4)·nH(2)O. Under similar conditions, the mononuclear Y(III) complex forms the dimeric compound [{Y(LH(2))(H(2)O)Cl}(μ(2)-CO(3)){Y(LH(2))(H(2)O)(2)}](ClO(4))(3)·4H(2)O. These complexes have been characterized by their IR and NMR ((1)H, (13)C) spectra. The X-ray crystal structures have been determined for the trinuclear carbonato-bridged compounds of Nd(III), Gd(III) and Tb(III) and the dinuclear compound of Y(III). In all cases, each of the metal centers are 8-coordinate involving two imine nitrogens and two phenolate oxygens of the macrocyclic ligand (LH(2)) whose two other imines are protonated and intramolecularly hydrogen-bonded with the phenolate oxygens. The oxygen atoms of the carbonate anion in the trinuclear complexes are bonded to the metal ions in tris-bidentate μ(3)-η(2):η(2):η(2) fashion, while they are in bis-bidentate μ(2)-η(2):η(2) mode in the Y(III) complex. The magnetic properties of the Gd(III) complex have been studied over the temperature range 2 to 300 K and the magnetic susceptibility data indicate a very weak antiferromagnetic exchange interaction (J = -0.042 cm(-1)) between the Gd(III) centers (S = 7/2) in the metal triangle through the carbonate bridge. The luminescence spectral behaviors of the complexes of Sm(III), Eu(III), and Tb(III) have been studied. The ligand LH(2) acts as a sensitizer for the metal ions in an acetonitrile-toluene glassy matrix (at 77 K) and luminescence intensities of the complexes decrease in the order Eu(3+) > Sm(3+) > Tb(3+).     

Unusual room temperature CO(2) uptake in a fluoro-functionalized MOF: insight from Raman spectroscopy and theoretical studies

We herein report an unusual CO(2) adsorption behavior in a fluoro-functionalized MOF {[Zn(SiF(6))(pyz)(2)]·2MeOH}(n) (1) with a 1D channel system, which is made up of pyrazine and SiF(6)(2-) moieties. Surprisingly, desolvated 1 (1') adsorbs higher amounts of CO(2) at 298 K than at 195 K, which is in contrast to the usual trend. Combined Raman spectroscopic and theoretical studies reveal that slanted pyrazine rings in 1' with an angle of 17.2° with respect to the (200) Zn(ii)-Si plane at low temperature block the channel windows and thus reduce the uptake amount.     

Relay catalysis: combined metal catalyzed oxidation and asymmetric iminium catalysis for the synthesis of bi- and tricyclic chromenes

A catalytic asymmetric oxidative iminium-allenamine cascade allows the use of propargyl alcohols as stable substrates and yields valuable chiral bicyclic 4H-chromenes. A subsequent Michael addition-condensation domino reaction provides complex tricyclic 4H-chromenes in a highly enantioselective fashion.     

A metal-organic framework with highly polar pore surfaces: selective CO2 adsorption and guest-dependent on/off emission properties

A 3D porous Zn(II) metal-organic framework {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)(H(2)O)]·4H(2)O} (1; H(2)dht=dihydroxyterphthalate, azpy=4,4'-azobipyridine) has been synthesised by employing 2,5-dihydroxyterephthalic acid (H(4)dht), a multidentate ligand and 4,4'-azobipyridine by solvent-diffusion techniques at room temperature. The as-synthesised framework furnishes two different types of channels: one calyx-shaped along the [001] direction and another rectangle-shaped along the [101] direction occupied by guest water molecules. The dehydrated framework, {[Zn(2)(H(2)dht)(dht)(0.5)(azpy)(0.5)]} (1') provides 52.7% void volume to the total unit-cell volume. The pore surfaces of 1' are decorated with unsaturated Zn(II) sites and pendant hydroxyl groups of H(2)dht linker, thereby resulting in a highly polar pore surface. The dehydrated framework 1' shows highly selective adsorption of CO(2) over other gases, such as N(2), H(2), O(2) and Ar, at 195 K. Photoluminescence studies revealed that compound 1 exhibits green emission (λ(max)≈530 nm) on the basis of the excited-state intramolecular proton-transfer (ESIPT) process of the H(2)dht linker; no emission was observed in dehydrated solid 1'. Such guest-induced on/off emission has been correlated to the structural transformation and concomitant breaking and reforming of the OH···OCO hydrogen-bonding interaction in the H(2)dht linker in 1'/1.     

Geometry of Quark and Strange Quark Matter in Higher Dimensional General Relativity

In this paper we study quark matter and strange quark matter in higher-dimensional spherical symmetric space-times. We analyze strange quark matter for the different equations of state and obtain the space-time geometry of quark and strange quark matter. We also discuss the features of the obtained solutions in the context of higher-dimensional general theory of relativity.