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We herein disclose a dual synthetic approach involving electrochemical and mechanochemical strategies for diversely functionalized 3-nitro-2-aryl-immidazo[1,2-a]pyridines. Both methods offer a practical and straightforward alternative route for accessing this important class of biologically promising nitrogen-containing heterocycles. Significant advantages of the newly developed methods include mild and energy-efficient reaction conditions, avoidance of transition metal catalysts, external heating and additional oxidants, shorter reaction times, good to excellent yields, broad substrate scope, gram-scale applicability, operational simplicity, and eco-friendliness. Furthermore, a synthetic application was extended by successfully reducing synthesized 3-nitro-2-aryl-immidazo[1,2-a]pyridines to their corresponding amino derivatives.

The doping of carbon quantum dots with nitrogen gives a promising role to improve fluorescence performance. In the present study, nitrogen-doped carbon quantum dots (NCQDs) were synthesized through a facile and economically cheap hydrothermal method from Nerium OleanderL. petals as carbon source and ethylenediamine as nitrogen source. The quantum yield of NCQDs was found to be 3.5%. Here we have studied FRET between NCQDs and Rhodamine 6G (Rh6G) dye. The lifetime of NCQDs decreases from 2.70 to 1.90 ns on addition of Rh6G. The lifetime of acceptor increases from 5.2 ns (in the absence of donor) to 5.5 ns in the presence of donor. FRET process was hindered in the presence of Co2+only and deactivated the excitation energy of Rh6G. As a consequence, the fluorescence quenching rates increase. So, the FRET between NCQDs and Rh6G allowed enhancing the selectivity and sensitivity of detection of Co2+ion with limit of detection of 6.45 nM. The method was successfully applied for the detection of Co2+ions in real water.

Background: Understanding the interaction between different organic dyes and carbon quantum dots helps us to understand several photo physical processes like electron transfer, energy transfer, molecular sensing, drug delivery and dye degradation processes etc. Objective: The primary objective of this study is to whether the carbon quantum dots can act as an electron donor and can participate in the different photo physical processes. Methods: In this work, Carbon Quantum Dots (CQDLs) are synthesized in most economical and simple carbonization method where petals of Nelumbo nucifera L. are used as a carbon precursor. The synthesized CQDLs were characterized by using experimental techniques like UV−Vis absorption, FT-IR, Transmission Electron Microscopy (TEM), steadystate and time-resolved fluorescence spectroscopy. Results: The spectral analysis shows that the so synthesized CQDLs are spherical in shape and its diameter is around 4.2 nm. It shows the fluorescence emission maximum at 495 nm with a quantum yield of 4%. In this work the interaction between Carbon Quantum Dots (CQDLs) and an organic dye Malachite Green (MG) is studied using fluorescence spectroscopic technique under ambient pH condition (At pH 7). The quenching mechanism of CQDLs with MG was investigated using Stern-Volmer equation and time-resolved fluorescence lifetime studies. The results show that the dominant process of fluorescence quenching is attributed to Forster Resonance Energy Transfer (FRET) having a donor acceptor distance of 53 Å where CQDLs act as a donor and MG acts as an acceptor. Conclusion: This work has a consequence that CQDLs can be used as a donor species for different photo physical processes such as photovoltaic cell, dye sensitized solar cell, and also for antioxidant activity study.

Abstract: The unusual occurrence of ω phase (a three atom simple hexagonal structure) prior to β (bcc) phase under high pressure in group IV transition metals Ti, Zr and Hf has been analyzed through first principles electronic band structure calculations. The analysis of band structure of ω and β phases in the w stability regime suggest that the opening of band gap at the Fermi level in ω phase lowers the total energy of this phase relative to β, and stabilizes the ω phase. Additionally, the extension of band gap near Fermi level is largest in Ti followed by Hf and then Zr suggesting that ω phase is most stable in Ti and least in Zr, in line with the experimental observations. Further, the density of states of ∼ 0.33, 0.4 and 0.5, respectively at Fermi energy for ω phase relative to β phase in Ti, Hf and Zr indicates that the lowering in energy for ω is highest in Ti and lowest in Zr.