Spectroscopic studies of Eu doped calibo glass: Effect of the addition of barium carbonate, energy transfer in the presence of Sm

Optical properties of Eu³⁺ doped calibo glass has been studied in presence and absence of BaO and their dependence on BaO concentration explored. It is found that the fluorescence intensity increases and approaches maximum for 10% of BaO content but get quenched for higher concentrations. The energy transfer between two asimilar rare earth ions (Sm³⁺:Eu³⁺) doped in calibo glass has been verified on the basis of changes in fluorescence yield.     

SHI induced silicide formation and surface morphology at Co/Si system

Ion beam mixing is a useful technique to produce modifications at the surface and interface of the solid material. In the present work, ion beam induced modifications at Co/Si interface using 120 MeV Au-ion irradiation has been studied at ion fluences in the range of 10¹² to 10¹⁴ ions/cm² by secondary ion mass spectroscopy (SIMS) technique and calculated mixing efficiency at the interface. Silicide formation has been discussed on the basis of swift heavy ion (SHI) irradiation induced effects. Surface morphology and roughness of irradiated system with fluence 5 × 10¹³ and 1 × 10¹⁴ ions/cm² is studied by scanning tunneling microscopy (STM). Roughness of the surface shows marks of melting process and confirms the appearance of some pinholes in the reacted Co/Si system. Comparative study was also undertaken on annealed sample at 300 °C and then irradiated at a dose 1 × 10¹⁴ ions/cm².     

Screen conformal lightlike submanifolds of semi-Riemannian manifolds

Since the induced objects on a lightlike submanifold depend on its screen distribution which, in general, is not unique and hence we can not use the classical submanifold theory on a lightlike submanifold in the usual way. Therefore, in present paper, we study screen conformal lightlike submanifolds of a semi-Riemannian manifold, which are essential for the existence of unique screen distribution. We obtain a characterization theorem for the existence of screen conformal lightlike submanifolds of a semi-Riemannian manifold. We prove that if the differential operator D^s is a metric Otsuki connection on transversal lightlike bundle for a screen conformal lightlike submanifold then semi-Riemannian manifold is a semi-Euclidean space. We also obtain some characterization theorems for a screen conformal totally umbilical lightlike submanifold of a semi-Riemannian space form. Further, we obtain a necessary and sufficient condition for a screen conformal lightlike submanifold of constant curvature to be a semi-Euclidean space. Finally, we prove that for an irrotational screen conformal lightlike submanifold of a semi-Riemannian space form, the induced Ricci tensor is symmetric and the null sectional curvature vanishes.     

Deep eutectic solvent-mediated expedient multicomponent synthesis of oxazine scaffolds

A simple, efficient, and eco-friendly protocol for the synthesis of 1,3-oxazine derivatives, viz. 7-aryl-7,8-dihydro-6H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-e][1,3]oxazines and 3-aryl-3,4-dihydro-2H- naphtho[2,3-e][1,3]oxazine-5,10-diones, involving one-pot multicomponent condensation reaction of various amines and formaldehyde with sesamol/2-hydroxy-1,4-naphthoquinone, respectively, catalyzed by a choline chloride–oxalic acid deep eutectic solvent has been developed. The method offers several advantages, including mild reaction conditions, simple operating procedure, recyclable and biodegradable catalyst, short reaction times, and excellent yields of the target products.

     

Liquid crystalline side chain polymer with a poly (Geraniol-co-MMA) backbone and phenylbenzoate mesogenic group: synthesis and characterization

A new side chain liquid crystalline polymers have been synthesized and characterized in which [geraniol-co-MMA] polymer are used as a backbone linked via polymethylene spacer to phenyl benzoate mesogenic group. The polymer exhibits enantiotropic liquid crystallinity with nematic phase and does not exhibit side chain crystallization .A clear difference between the nature of the mesophase is evidenced between [Geraniol-co-MMA] main chain and methacrylate polymers .The LC polymer exhibit glass transition at 40 °C. In a comparative analysis, we discuss the relevance of polymer backbone in the synthesis of side chain liquid crystalline polymers.     

Synthetization and Functionalization of Natural,Polymer, and Quantum-Based Carbon Nanodots and Their Application in Biomedicine

Carbon nanodots (CNDs) are a developing branch of nanomaterials and nanoscience. This has generated much more interest in the field and class of biomedicine science by way of unique particular properties, such as high stability, great photoluminescence, easy green synthesis, and simple surface modification. Numerous applications, such as bioimaging, biosensing, and treatment, have made use of CNDs. This review describes the most recent developments in CND research and talks about major changes in the understanding of CNDs and their prospects as biomedical tools. The importance of this work lies in the ability of CNDs to overcome many of the limitations associated with traditional materials used in biomedicine, such as toxicity, poor biocompatibility, and limited functionality. Furthermore, the use of CNDs as drug carriers, imaging agents, and sensors has shown great potential in improving the diagnosis and treatment of various diseases. The novelty of this work lies in the diversity of approaches used in the synthesis and functionalization of CNDs, and the unique properties of CNDs that make them versatile tools for biomedicine. In particular, the ability to tune the size, shape, and surface chemistry of CNDs allows for the creation of tailored materials with specific biomedical applications. The review also discusses the challenges and future prospects of CNDs in biomedicine, including the need for standardization and optimization of CND synthesis, functionalization, and characterization protocols.     

Study of intermixing and Zr-silicide formation using swift heavy ion irradiation

Swift heavy ion (SHI) beam induced irradiation is an established technique for investigating structural modifications in thin films depending on the S _e sensitivity of material. Intermixing due to 120 MeV Au ion irradiation at different fluences from 10¹² to 10¹⁴ ions/cm² has been reported as a function of ion fluence in a-Si/Zr/a-Si thin films on Si substrate. The samples are characterized before (pristine) and after irradiation using Grazing Incident X-ray Diffraction (GIXRD) and Rutherford Backscattering Spectroscopy (RBS), which confirm the formation of ZrSi at thin film interface. It is suggested that mixing is mainly due to electronic energy loss since the energy transferred from high energy ions seems to create a transient molten zone along the ion track. It is found that the interface mixing increases linearly with the increase in ion fluence. The mixing effect explained in the framework of Thermal spike model. The irradiation effect on the surface roughness of the system is measured using Atomic Force Microscopy (AFM) technique. The current conduction mechanism and Schottky barrier height are also calculated by taking I–V curves across the Metal/Si junction.     

Microwave assisted,Ca(II)-catalyzed Ritter reaction for the green synthesis of amides

An efficient solvent-free synthesis of amides by Ca(II) catalyzed Ritter reaction has been reported under microwave irradiation. This green protocol tolerates the substrate diversity and delivers the high yielding amides with minimal loading of inexpensive and more abundant Ca(II) catalyst.     

N-Heterocyclic Carbene-Catalyzed Formal [6+2] Annulation Reaction via Cross-Conjugated Aza-Trienolate Intermediates

The diverse reactivity of N-heterocyclic carbenes (NHCs) in organocatalysis is due to the possibility of different modes of action. Although NHC-bound enolates and dienolates are known, the related NHC-bound cross-conjugated aza-trienolates remain elusive. Herein, we demonstrate the NHC-catalyzed formal [6+2] annulation of nitrogen-containing heterocyclic aldehydes with α,α,α-trifluoroacetophenones leading to the formation of versatile pyrrolooxazolones (29 examples). The catalytically generated cross-conjugated aza-trienolates (aza-fulvene type) underwent smooth [6+2] annulation with electrophilic ketones to afford the product in moderate to good yields under mild conditions. Preliminary DFT studies on the mechanism are also provided.     

An efficient solvent-tuning approach for the rapid synthesis of thiazolidinone derivatives and the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates

Green synthetic approach has been developed for the rapid generation of thiazolidinone derivatives as crystallized products under catalyst-free conditions in water by polarity adjustment with ethyl lactate as a co-solvent in excellent yields. Additionally, interesting findings on the selective synthesis of 2-amino-4H-1,3-thiazin-4-one and dimethyl 3,3′-thiodiacrylates have been reported.