Estimation of <Superscript>235</Superscript>U concentration in some depleted uranium samples by high resolution gamma-ray spectrometry using 185 keV and 1001 keV gamma-energies of <Superscript>235</Superscript>U and <Superscript>234m</Superscript>Pa

The migration of ²³⁷Np in an undisturbed Chinese loess column was investigated by direct γ-ray method. The column was taken from a field test site and installed in a laboratory simulation hall. Radionuclide ²³⁷Np in the form of neptunium nitrate, mixed with quartz, was introduced into the column and covered with loess. Artificial rainfall was applied to the column for about 3 years and, the counting rates of ²³⁷Np in the column from 56 to 616 days at different vertical positions were detected with a γ-ray detection system. Based on the counting rates of ²³⁷Np in the simulation column at different vertical positions and the distance from the source layer, the relationship of the mass center of ²³⁷Np in the column at different experimental periods to the experimental time was established, C _m = 0.36 log(t)-2.75. Here C _m is the mass center of ²³⁷Np in the column, cm, and t is the experimental time in days. Based on this relationship, the mass center of ²³⁷Np for the 1,073-day experiment was predicted and compared to that obtained with the final destructive method. The good agreement between the prediction and the experimental values indicates that the direct γ-ray method could be used to predict the migration of strongly adsorbed radionuclides such as ²³⁷Np in environmental media with the help of laboratory simulation columns.     

Convenient method for epoxidation of alkenes using aqueous hydrogen peroxide

[reaction: see text] The complex [Ru(tpy)(pydic)] (1a) is an active catalyst for epoxidation of alkenes by aqueous 30% hydrogen peroxide in tertiary alcohols. The protocol is simple to operate and gives the corresponding epoxides in good to excellent yields. Chiral enantiopure [Ru(tpy)(pydic)] complexes have been synthesized and successfully applied in this procedure.     

Determination of 231Pa in Monazite and Other Streams of the Thorium Production Cycle

Monazite (chief source of thorium) which is available in plenty in the beach sands of Kerala, India, contains uranium in the range of 0.25% to 0.35%. An attempt has been made to estimate ²³¹Pa in monazite and the corresponding process stream samples of the thorium production cycle. This paper reports the ²³¹Pa activity in these samples, after coprecipitation of ²³¹Pa on MnO₂ carrier and estimation by -ray spectrometry. The estimation shows about 1000 Bq/kg of ²³¹Pa in monazite. This is the first reported estimate of ²³¹Pa in monazite.     

Photoproduction of iodine with nanoparticulate semiconductors and insulators

The crystal structures of different forms of TiO2 and those of BaTiO3, ZnO, SnO2, WO3, CuO, Fe2O3, Fe3O4, ZrO2 and Al2O3 nanoparticles have been deduced by powder X-ray diffraction. Their optical edges have been obtained by UV-visible diffuse reflectance spectra. The photocatalytic activities of these oxides and also those of SiO2 and SiO2 porous to oxidize iodide ion have been determined and compared. The relationships between the photocatalytic activities of the studied oxides and the illumination time, wavelength of illumination, concentration of iodide ion, airflow rate, photon flux, pH, etc., have been obtained. Use of acetonitrile as medium favors the photogeneration of iodine.     

Carbon nanoparticles as chromophores for photon harvesting and photoconversion

Carbon nanomaterials have generated a tremendous amount of attention in the scientific community. While most of the research and development efforts have been on fullerenes, carbon nanotubes, and graphene sheets, carbon nanoparticles (which are often considered as impurities or unwanted complications in the other carbon nanomaterials) have recently emerged as a unique class of highly fluorescent nano-dots. However, little or no attention has been paid to potential uses of carbon nanoparticles as chromophores in photochemical reactions or for photon harvesting and photoconversion in general. In the study reported herein we demonstrate the chromophore-equivalent functions of aqueous-suspended small carbon nanoparticles in harvesting visible photons for the reductive coating of the nanoparticles with silver and gold and, as a result, the preparation of unique carbon-noble-metal core-shell nanostructures.     

Concise synthesis of 5-methyl-, 5-formyl,and 5-carboxy analogues of 2′-deoxycytidine-5′-triphosphate

We describe a concise and efficient synthesis of 5-methyl-, 5-formyl-, and 5-carboxy-analogues of 2′-deoxycytidine-5′-triphosphate which are well known for their various biological applications. A protection-free one-pot synthesis was used to convert 5-methyl-2′-deoxycytidine into 5-methyl-2′-deoxycytidine-5′-triphosphate in high yield. 5-Formyl-2′-deoxycytidine-5′-triphosphate was obtained upon photosensitized oxidation (UV-A irradiation, λ ∼365 nm) of an aerated aqueous solution of 5-methyl-2′-deoxycytidine-5′-triphosphate with the use of menadione as the photosensitizer. 5-Formyl-2′-deoxycytidine-5′-triphosphate was converted into 5-carboxy-2′-deoxycytidine-5′-triphosphate by using biphasic TEMPO/BAIB oxidation method in high yield.     

Efficient Synthesis of New Peptidyl Chloromethyl Ketones for the Application of Proteinase K Inhibitors

The synthesis of a new series of peptidyl chloromethyl ketones such as MeOSuc-Ala-Ala-Pro-Ile-CH₂Cl (AAPI) and MeOSuc-Ala-Ala-Ala-Pro-Ile-CH₂Cl (AAAPI) is described.     

Recognition of polycyclic aromatic hydrocarbons and their derivatives by the 1,3-dinaphthalimide conjugate of calix[4]arene: emission, absorption, crystal structures, and computational studies

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants as well as well-known carcinogens. Therefore, it is important to develop an effective receptor for the detection and quantification of such molecules in solution. In view of this, a 1,3-dinaphthalimide derivative of calix[4]arene (L) has been synthesized and characterized, and the structure has been established by single crystal XRD. In the crystal lattice, intermolecular arm-to-arm π···π overlap dominates and thus L becomes a promising receptor for providing interactions with the aromatic species in solution, which can be monitored by following the changes that occur in its fluorescence and absorption spectra. On the basis of the solution studies carried out with about 17 derivatives of the aromatic guest molecular systems, it may be concluded that the changes that occur in the fluorescence intensity seem to be proportional to the number of aromatic rings present and thus proportional to the extent of π···π interaction present between the naphthalimide moieties and the aromatic portion of the guest molecule. Though the nonaromatic portion of the guest species affects the fluorescence quenching, the trend is still based on the number of rings present in these. Four guest aldehydes are bound to L with K(ass) of 2000-6000 M(-1) and their minimum detection limit is in the range of 8-35 μM. The crystal structure of a naphthaldehyde complex, L.2b, exhibits intermolecular arm-to-arm as well as arm-to-naphthaldehyde π···π interactions. Molecular dynamics studies of L carried out in the presence of aromatic aldehydes under vacuum as well as in acetonitrile resulted in exhibiting interactions observed in the solid state and hence the changes observed in the fluorescence and absorption spectra are attributable for such interactions. Complex formation has also been delineated through ESI MS studies. Thus L is a promising receptor that can recognize PAHs by providing spectral changes proportional to the aromatic conjugation of the guest and the extent of aromatic π···π interactions present between L and the guest.     

Advances in Biginelli reaction: A comprehensive review

The Biginelli reaction, a conventional three-component reaction provides 3,4-dihydropyrimidin-2(1H)-ones/thiones via one-pot acid catalyzed cyclocondensation of an aldehyde, a β-keto ester, and urea or thiourea. Dihydropyrimidones are well-known scaffolds having a wide range of pharmacological activities. So far classical Biginelli reaction has witnessed several modification and studies are still continuing in this field to develop greener and efficient methodologies. In this review, we summarize the recent advances in Biginelli reaction covering literature from 2020 to 2023.     

Lithium-enriched polypyrrole as a prospective cathode material for Li-ion cells

Lithium substitution in polypyrrole can be accomplished by a variety of approaches and the present work introduces one of the cost-effective techniques using a relatively less expensive lithium salt, n-butyllithium in hexanes (n-BuLi), as the dopant. Chemical oxidative polymerization method is employed to synthesize polypyrrole (PPy) using anhydrous ferric chloride as the oxidant and it is dedoped using NH₄OH solution in the fully reduced state. The dedoped polypyrrole is treated with n-butyllithium in hexanes (n-BuLi) in an argon-filled glove box to get the lithiated form of polypyrrole (PPyL) and the concentration of n-BuLi is varied to improve metalation. The lithiated PPy is characterized by FTIR spectroscopy, XRD, FESEM, and TEM techniques to understand the structural and the morphological details. The lithium content in the lithiated samples is estimated using ICP-AES analysis. The thermal studies using the TGA technique show that the lithiated polypyrrole has good thermal stability. Coin cells are assembled in the argon-filled glove box using Li-substituted polypyrrole as the cathode, lithium metal foil as the anode, and lithium hexafluorophosphate (LiPF₆) as the electrolyte. The assembled cells are electrochemically characterized using cyclic voltammetry and charge–discharge cycling techniques and it is seen that the Li-substituted polypyrrole-based Li-ion cells are electrochemically active.