National Chemical Laboratory

About: National Chemical Laboratory is a facility organization based out in Pune, Maharashtra, India. It is known for research contribution in the topics: Catalysis & Nanoparticle. The organization has 8891 authors who have published 14837 publications receiving 387600 citations.

Thermal Expansion, Anharmonicity and Temperature-Dependent Raman Spectra of Single- and Few-Layer MoSe2 and WSe2

Abstract: We report the temperature-dependent Raman spectra of single- and few-layer MoSe2 and WSe2 in the range 77–700 K. We observed linear variation in the peak positions and widths of the bands arising from contributions of anharmonicity and thermal expansion. After characterization using atomic force microscopy and high-resolution transmission electron microscopy, the temperature coefficients of the Raman modes were determined. Interestingly, the temperature coefficient of the A22u mode is larger than that of the A1g mode, the latter being much smaller than the corresponding temperature coefficients of the same mode in single-layer MoS2 and of the G band of graphene. The temperature coefficients of the two modes in single-layer MoSe2 are larger than those of the same modes in single-layer WSe2. We have estimated thermal expansion coefficients and temperature dependence of the vibrational frequencies of MoS2 and MoSe2 within a quasi-harmonic approximation, with inputs from first-principles calculations based on density functional theory. We show that the contrasting temperature dependence of the Raman-active mode A1g in MoS2 and MoSe2 arises essentially from the difference in their strain–phonon coupling.

Molecular Level Control of the Capacitance of Two-Dimensional Covalent Organic Frameworks: Role of Hydrogen Bonding in Energy Storage Materials

Abstract: Two-dimensional redox-active covalent organic frameworks (COFs) are ideal materials for energy storage applications due to their high surface area, extended π conjugated structure, tunable pore size, and adjustable functionalities. Herein, we report the synthesis and supercapacitor application of two redox active COFs [TpPa-(OH)2 and TpBD-(OH)2] along with the role of their redox active functional groups for the enrichment of specific capacitance. Of these COFs, TpPa-(OH)2 exhibited the highest specific capacitance of 416 F g–1 at 0.5 A g–1 current density in three electrode configuration while the highest specific capacitance was 214 F g–1 at 0.2 A g–1 current density in two electrode configuration. Superior specific capacitance was due to emergence of excellent pseudocapacitance by virtue of precise molecular level control over redox functionalities present in the COF backbone. This COF also demonstrated 66% capacitance retention after 10 000 cycles along with 43% accessibility of the redox-active hydro...

Synthesis, Electronic Structure, DNA and Protein Binding, DNA Cleavage, and Anticancer Activity of Fluorophore-Labeled Copper(II) Complexes

Abstract: Two mononuclear fluorophore-labeled copper(II) complexes [Cu(nip)(acac)]+(2) and [Cu(nip)2]2+ (3), where fluorophore is 2-(naphthalen-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline (nip) (1) and acac is acetylacetone, have been synthesized and characterized by various techniques. The ligand 1 and complex 2 are structurally characterized by single-crystal X-ray diffraction. The coordination geometries around the copper are square planar in solid as well as solution state as evidenced by electron paramagnetic resonance (EPR) spectroscopy. The density functional calculations carried out on 1−3 have shown that electron-rich regions in the highest occupied orbital are localized on the naphthalene and partly on the phenanthroline moiety. Both complexes 2 and 3 in dimethyl sulfoxide (DMSO) exhibit near square planar structure around the metal ion in their ground state. Time-dependent density functional theory (TD-DFT) calculations reveal that Cu(II) ion in complex 2 shows tetrahedral coordination around the metal w...