15 research outputs found
PREVENTIVE EFFECT OF CYCAS REVOLUTA IN 1,2-DIMETHYLHYDRAZINE-INDUCED COLON CANCER IN WISTAR RAT MODEL
 Objective: The aim of this study was to evaluate the colon cancer protective activity of Cycas revoluta (Cycadaceae).Methods: Methanolic extracts of C. revoluta (MECR) were assessed for total polyphenols and total flavonoids content. For the in vivo study, animals were divided into five groups (n=6). Group I serves as control which received 0.25% carboxymethyl cellulose solution. Groups II-V were treated with 1,2-dimethylhydrazine (DMH) which was given at the dose of 20 mg/kg b.w., s.c. once a week for 4 consecutive weeks. Aqueous suspension of MECR at a dose of 200 mg/kg/day and 400 mg/kg was administered orally to the animals in Groups III-IV every day for 16 weeks. Group V received 5-fluorouracil (5-FU) as a standard drug at a dose of 10 mg/kg b.w., per day s.c. for 16 weeks. After that, animals are sacrificed and colons are taken separately to evaluate biochemical parameters and morphological and histopathological changes.Results: MECR contains total polyphenols (6.3±0.09 mg of gallic acid equivalent /g) and total flavonoids (4.6±0.06 mg of rutin equivalent/g). The in vivo study revealed that superoxide dismutase (SOD), catalase, and reduced glutathione (GSH) activity were decreased in DMH Group. All these parameters were restored significantly (p<0.05) toward the near normal value on supplementation with MECR (200 and 400 mg/kg b.w.) to DMH-treated rats (Groups III and IV). In Group V, the synthetic standard drug 5-FU (10 mg/kg b.w.) also increases the activities of SOD, CAT, and GSH significantly (p<0.05) more in DMH-treated rats.Conclusions: It can be concluded that MECR protects rat from DMH-induced colon cancer
Centrosymmetric-noncentrosymmetric Structural Phase Transition in Quasi one-dimensional compound, (TaSe)I
(TaSe)I, a compound belonging to the family of quasi-one-dimensional
transition-metal tetrachalcogenides, has drawn significant attention due to a
recent report on possible coexistence of two antagonistic phenomena,
superconductivity and magnetism below 2.5~K (Bera et. al, arXiv:2111.14525).
Here, we report a structural phase transition of the trimerized phase at
temperature, ~145~K using Raman scattering, specific heat, and
electrical transport measurements. The temperature-dependent single-crystal
X-ray diffraction experiments establish the phase transition from a
high-temperature centrosymmetric to a low-temperature non-centrosymmetric
structure, belonging to the same tetragonal crystal family. The first-principle
calculation finds the aforementioned inversion symmetry-breaking structural
transition to be driven by the hybridization energy gain due to the off-centric
movement of the Ta atoms, which wins over the elastic energy loss.Comment: 11 pages, 5 figures, Under review as a regular articl
Enhanced coercivity and emergence of spin cluster glass state in 2D ferromagnetic material Fe3GeTe2
Two-dimensional (2D) van der Waals (vdW) magnetic materials with high
coercivity and high are desired for spintronics and memory storage
applications. FeGeTe (F3GT) is one such 2D vdW ferromagnet with a
reasonably high , but with a very low coercive field,
(100~Oe). Some of the common techniques of enhancing are
by introducing pinning centers, defects, stress, doping, etc. They involve the
risk of undesirable alteration of other important magnetic properties. Here we
propose a very easy, robust, and highly effective method of phase engineering
by altering the sample growth conditions to greatly enhance the intrinsic
coercivity (7-10 times) of the sample, without compromising its fundamental
magnetic properties (210K). The phase-engineered sample
(F3GT-2) comprises of parent F3GT phase with a small percentage of randomly
embedded clusters of a coplanar FeTe (FT) phase. The FT phase serves as both
mosaic pinning centers between grains of F3GT above its antiferromagnetic
transition temperature (70~K) and also as anti-phase domains
below . As a result, the grain boundary disorder and metastable
nature are greatly augmented, leading to highly enhanced coercivity, cluster
spin glass, and meta-magnetic behavior. The enhanced coercivity (1~kOe)
makes F3GT-2 much more useful for memory storage applications and is likely to
elucidate a new route to tune useful magnetic properties. Moreover, this method
is much more convenient than hetero-structure and other cumbersome techniques.Comment: 12 pages, 11 figure
Raman signatures of lattice dynamics across inversion symmetry breaking phase transition in quasi-1D compound, (TaSe)I
Structural phase transition can occur due to complex mechanisms other than
simple dynamical instability, especially when the parent and daughter structure
is of low dimension. This article reports such an inversion symmetry-breaking
structural phase transition in a quasi-1D compound (TaSe)I at T
141~K studied by Raman spectroscopy. Our investigation of collective lattice
dynamics reveals three additional Raman active modes in the low-temperature
non-centrosymmetric structure. Two vibrational modes become Raman active due to
the absence of an inversion center, while the third mode is a soft phonon mode
resulting from the vibration of Ta atoms along the \{-Ta-Ta-\} chains.
Furthermore, the most intense Raman mode display Fano-shaped asymmetry,
inferred as the signature of strong electron-phonon coupling. The group theory
and symmetry analysis of Raman spectra confirm the displacive-first-order
nature of the structural transition. Therefore, our results establish
(TaSeI as a model system with broken inversion symmetry and strong
electron-phonon coupling in the quasi-1D regime.Comment: Main text - 6 figures, 11 pages, supplementary - 10 figures, 13 page
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
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
Review of recent progress on THz spectroscopy of quantum materials: superconductors, magnetic and topological materials
Recently, the THz spectroscopy has been efficiently used to investigate varieties of quantum materials, including superconductors, novel magnetic, and topological materials. These materials often exhibit strong correlation and competing interactions between various degrees of freedom, including charge, spins, orbital, and lattice dynamics, which lead to many exotic phenomena and novel phase transitions whose cause–effect correlations are challenging to determine. Whereas probing the ground state’s excitations can unravel the underlying mechanism of these complex phenomena. The characteristic energy scales of different elementary excitations and collective modes in many of these materials are in the THz frequency range. Therefore, THz spectroscopy has become a very effective probe and directly revealed many exciting physics. Many novel phenomena, including exotic quasiparticle excitations in magnetic systems, topological magneto-electric effect, and topological quantum phase transition in three-dimensional topological insulators, are studied with unprecedented success. Here, we review some recent research reports on many-body quantum materials, including superconductors, novel magnetic, and topological materials probed by few popular THz-spectroscopy techniques. We will also briefly discuss the prospects of using THz spectroscopy for observing some exotic quantum phenomena that are still elusive or under investigation
Ultrafast Carrier Dynamics of Photo-Induced Cu-Doped CdSe Nanocrystals
The
understanding of ultrafast carrier relaxation process in doped
semiconductor quantum dots (QDs) is very important for their potential
applications in light-emitting diodes, optoelectronics. Here, we have
studied the change in electronic properties of Cu-doped CdSe QDs upon
light illumination. The light-induced effect leads to the enhancement
of the band edge decay time and reduces the decay time of the dopant
emission due to photocorrosion of Cu-doped CdSe QDs. The bleaching
recovery kinetics and the hot electron cooling dynamics have been
studied by using femtosecond transient absorption spectroscopy. It
is observed that the electron cooling process of doped CdSe QDs is
dependent on the dopant concentration and the cooling kinetics of
doped CdSe QDs are found to be slower than undoped QDs. After light
irradiation, the cooling processes of hot electron and recovery process
in doped systems are modified
Characterization of enhanced antibacterial effects of novel silver nanoparticles
In the present study, we report the preparation of silver nanoparticles in the range of 10–15 nm with increased stability and enhanced anti-bacterial potency. The morphology of the nanoparticles was characterized by transmission electron microscopy. The antibacterial effect of silver nanoparticles used in this study was found to be far more potent than that described in the earlier reports. This effect was dose dependent and was more pronounced against gram-negative bacteria than gram-positive organisms. Although bacterial cell lysis could be one of the reasons for the observed antibacterial property, nanoparticles also modulated the phosphotyrosine profile of putative bacterial peptides, which could thus affect bacterial signal transduction and inhibit the growth of the organisms