40 research outputs found
Square lattice formation in a monodisperse complex plasma
We present the first observations of a square lattice formation in a
monodisperse complex plasma system - a configurational transition phenomenon
that has long been an experimental challenge in the field. The experiments are
conducted in a tabletop L-shaped Dusty Plasma Experimental (DPEx-II) device in
a DC glow discharge Argon plasma environment. By a careful control of the
vertical potential confining the charged particles as well as the strength of
the ion wake charge interactions with the dust particles we are able to steer
the system towards a crystalline phase that exhibits a square lattice
configuration. The transition occurs when the vertical confinement strength is
slightly reduced below a critical value leading to a buckling of the
monodisperse hexagonal 2D dust crystal to form a narrowly separated bilayer
state (a quasi-2D state). Some theoretical insights into the transition process
are provided through Molecular Dynamics (MD) simulations carried out for the
parameters relevant to our experiment.Comment: This manuscript contains six pages and six figure
Design and Synthesis of Fluorescent Carbon Dot Polymer and Deciphering Its Electronic Structure
Herein we report the one-pot synthesis of a fluorescent polymer-like material (pCD) by exploiting ruthenium-doped carbon dots (CDs) as building blocks. The unusual spectral profiles of pCDswith double-humped periodic excitation dependent photoluminescence (EDPL), and the regular changes in their corresponding average lifetime indicate the formation of high energy donor states and low energy aggregated states due to the overlap of molecular orbitals throughout the chemically switchable π-network of CDs on polymerization. To probe the electronic distribution of pCDs, we have investigated the occurrence of photoinduced electron transfer with a model electron acceptor, menadione using transient absorption technique, corroborated with low magnetic field, followed by identification of the transient radical ions generated through electron transfer. The experimentally obtained B_(1/2) value, a measure of the hyperfine interactions present in the system, indicates the presence of highly conjugated π-electron cloud in pCDs. The mechanism of formation of pCDs and the entire experimental findings have further been investigated through molecular modeling and computational modeling. The DFT calculations demonstrated probable electronic transitions from the surface moieties of pCDs to the tethered ligands
Electronic Structure of Ordered Double Perovskite Ba2CoWO6
Ba2CoWO6 (BCoW) has been synthesized in polycrystalline form by solid state
reaction at 1200C. Structural characterization of the compound was done through
X-ray diffraction (XRD) followed by Rietveld analysis of the XRD pattern. The
crystal structure is cubic, space group Fm-3m (No 225) with the lattice
parameter, a=8.210A. Optical band-gap of the present system has been calculated
using the UV-Vis Spectroscopy and Kubelka-Munk function, its value being 2.45
eV. A detailed study of the electronic properties has also been carried out
using the density functional theory (DFT) techniques implemented on WIEN2k.
Importance of electron-electron interaction between the Co ions leading to
half-metallic behavior, crystal and exchange splitting together with the
hybridization between O and Co, W has been investigated using the total and
partial density of states.Comment: 3 pages, 3 figures, submitted to 58th DAE-SSPS 201