50175 research outputs found
Sort by
pH dependent luminescence switching of tin disulfide quantum dots
No full textDesigning a molecule with pH, temperature and ion concentration sensitive luminescence properties is always fascinating. Tin disulfide (SnS2), a member of layered metal dichalcogenides (LMDs) family, is explored much for their commendable applications, however, its fluorescence property is still less explored. Present study reports a facile and eco-friendly bottom up synthesis route for fin disulfide quantum dots (SnS2-QDs). Transmission electron microscopic (TEM), and Atomic force microscopic (AFM) analysis revealed an average particle size of similar to 3.6 nm. Our reported synthesis method provide the in-situ functionalization of quantum dots (QDs) making it highly sensitive to its environment. SnS2-QDs are found to be pH sensitive and hence a detailed pH dependent luminescence study has been performed. Interestingly it was found that SnS2-QDs possess similar to 16 fold enhanced luminescence intensity in acidic condition (pH similar to 1, QY = 5.32%) rather its basic condition (pH similar to 12, QY = 1.17%). To explain this pH dependent behavior of SnS2-QDs, a mechanism has been proposed where this luminescence switching is mainly supposed due to protonation and deprotonation between -NH2 and -COOH groups. We believe present study may provide an insight for the development of pH sensor using SnS2-QDs for practical applications
Development and characterization of Al5083-CNTs/SiC composites via friction stir processing
No full textCarbon nanotubes (CNTs) and or micron-sized silicon carbide (SiC) particles were reinforced with Al5083 matrix to develop mono and hybrid composites via friction stir processing (FSP). The effect of CNTs/SiC either individually or in aggregate form, on microstructural evolution, texture, and mechanical properties of friction stir processed (FSPed) Al5083 composites were studied. EBSD and TEM analyses revealed an equiaxed recrystallized microstructure and dislocations rearranged to form high angle grain boundaries (HAGBs) upon dynamic recrystallization (DRX), respectively. The overall weak texture intensity was observed across the stir zone of FSPed samples due to the multiple passes. Incorporation of CNTs/SiC particles in Al5083 matrix resulted in the activation of Zener-Holloman mechanism and particle-stimulated nucleation (PSN) mechanism by developing randomly oriented grains. In FSPed composites, SiC particles are dispersed homogeneously with good interfacial bonding and CNTs are partially reacted with an Al5083 matrix to form in-situ Al4C3 intermetallic compound. The maximum tensile strength of 361 MPa was obtained for Al5083-CNTs/SiC hybrid composite. The fracture surface of the SiC reinforced composite revealed that the voids initiation at the matrix-particle interface regions
Borylated perylenediimide: self-assembly, photophysics and sensing application
No full textTriarylboryl appended perylenediimide (PDI-TAB) is designed and synthesized. The incorporation of triarylboranes (TABs) decreases self-aggregation and increases the solubility of PDI-TAB in common organic solvents. Fluorescence emission colors ranging from red, yellow and green are realized by judiciously modulating the concentration of PDI-TAB in solution. The morphology and dimensions of the self-assemblies formed by PDI-TAB can be controlled by changing the experimental conditions. For example, PDI-TAB forms fibers of finite length when bulk powder is dispersed in methanol; it shows flexible lengthy 1D fibers when dichloromethane solution of PDI-TAB is injected into methanol solvent. PXRD analysis indicates that the molecular organization remains the same in both cases. PDI-TAB functions as a selective fluorogenic sensor for toxic fluoride anions; the sensing mechanism is explained by using theoretical calculations
Linkage induced enhancement of fluorescence in metal-carbene bond directed metallacycles and metallacages
No full textTwo new 1,4-dihydropyrrolo3,2-b]pyrrole based aggregation induced emission (AIE)-inactive di- and tetra-imidazolium salts were employed with Ag(i) for the synthesis of a Ag-carbene bond directed metallacycle (1) and metallacage (2), respectively. Transmetalation of these complexes allowed their facile conversion to their respective Au(i)-metallacycle (3) and metallacage (4). The final assemblies exhibit linkage induced enhancement of fluorescence (LIEF). The free ligands are almost non-fluorescent (phi(F) = 3.2, 3.4) in comparison to their metal-carbene counterparts (phi(F) up to 32.0). Thus, without using any AIEgen, obtaining high emission efficiencies in complexes Ag-I-C-NHC (1, 2) via linkage is a nice approach towards turn-on fluorescence
Peculiar magnetic states in the double perovskite Nd2NiMnO6
No full textWe present magnetic measurements on Nd2NiMnO6 which exhibits a well-known insulating paramagnetic state to an insulating ferromagnetic state transition when cooled below 200 K. Beyond this basic fact, there is a great deal of diversity in the reported magnetic properties and interpretation of specific anomalies observed in the magnetic data of this compound below the Curie temperature. We address specifically two anomalies discussed in the past, namely, a spin-glass like behavior observed in some samples near 100 K and a downturn in the magnetization with a lowering of the temperature below approximately 50 K. We show for the first time that the application of an increasing magnetic field can systematically change the low-temperature behavior to make the down-turn in the magnetization into an upturn. With the help of first principle calculations and extensive simulations along with our experimental observations, we provide a microscopic understanding of all magnetic properties observed in this interesting system to point out that the glassiness around 100 K is absent in well-ordered samples and that the low-temperature magnetic anomaly below 50 K is a consequence of a ferromagnetic coupling of the Nd spin moments with the spin of the Ni-Mn ordered sublattice without giving rise to any ordering of the Nd sublattice that remains paramagnetic, contrary to earlier claims. We explain this counter-intuitive interpretation of a ferromagnetic coupling of Nd spins with Ni-Mn spin giving rise to a decrease in the total magnetic moment by noting the less than half-filled 4f occupation of Nd that ensures orbital and spin moments of Nd to be opposite to each other due to the spin-orbit coupling. Since the ground state total magnetic moment of Nd has a contribution from the orbital moment, that is larger than the spin moment, the total moment of Nd is indeed pointing in a direction opposite to the direction of spin moments of the Ni-Mn sublattice as a consequence of the ferromagnetic exchange coupling between Nd and Ni-Mn spins
Synthesis of Graphene Oxide-Fe3O4 Based Nanocomposites Using the Mechanochemical Method and in Vitro Magnetic Hyperthermia
No full textThe study presented in this work consists of two parts: The first part is the synthesis of Graphene oxide-Fe3O4 nanocomposites by a mechanochemical method which, is a mechanical process that is likely to yield extremely heterogeneous particles. The second part includes a study on the efficacy of these Graphene oxide-Fe3O4 nanocomposites to kill cancerous cells. Iron powder, ball milled along with graphene oxide in a toluene medium, underwent a controlled oxidation process. Different phases of GO-Fe3O4 nanocomposites were obtained based on the composition used for milling. As synthesized nanocomposites were characterized by x-ray diffraction (XRD), alternating magnetic field (AFM), Raman spectroscopy, and a vibrating sample magnetometer (VSM). Additionally, the magnetic properties required to obtain high SAR values (Specific Absorption Rate-Power absorbed per unit mass of the magnetic nanocomposite in the presence of an applied magnetic field) for the composite were optimized by varying the milling time. Nanocomposites milled for different extents of time have shown differential behavior for magneto thermic heating. The magnetic composites synthesized by the ball milled method were able to retain the functional groups of graphene oxide. The efficacy of the magnetic nanocomposites for killing of cancerous cells is studied in vitro using HeLa cells in the presence of an AC (Alternating Current) magnetic field. The morphology of the HeLa cells subjected to 10 min of AC magnetic field changed considerably, indicating the death of the cells
Structure-Dependent Electrical and Magnetic Properties of Iron Oxide Composites
No full textThe physical and chemical properties of polymorphs of iron oxides are utilized for electronic, energy, and biomedical applications. To design a functional material with arresting interplay at the interfaces and boundaries between polymorphs of iron oxide (Fe3O4 - magnetite with Fe2O3 - hematite), two different approaches of synthesis are adopted, namely, mechanical mixing and in situ growth. Unlike mechanically mixed composites, the in situ-synthesized composites show the development of a highly distinct non-stoichiometric, Fe21.34O32 phase at the boundary. The atomically diffused composition at boundary is found to govern the fourfold increase in conductivity. By varying the ratio of constituent iron oxide polymorphs, the dielectric constant can be tuned and is found to be highly frequency dependent with minimum loss in tan delta plot. The inherent ferromagnetism of Fe3O4 reveals to be retained in composite samples
Serine/threonine/tyrosine-interacting-like protein 1 (STYXL1), a pseudo phosphatase, promotes oncogenesis in glioma
No full textPhosphatases play an important role in cellular signaling and are often found dysregulated in cancers including glioblastoma (GBM). A comprehensive bioinformatics analysis of phosphatases (n = 403) in multiple datasets revealed their deregulation in GBM. Among the differentially regulated phosphatases (n = 186; 46.1%), majority of them were found to be regulated by microRNA (n = 94; 50.5%) followed by DNA methylation (n = 22; 11.8%) and altered copy number variation (n = 10; 5.37%). STYXLI (Serine/threonine/tyrosine-interacting-like protein 1) was found to be the second most amplified gene in GBM, upregulated, and correlated to poor prognosis. The expression of STYXL1 was also found to be higher in IDH1 mutant gliomas and G-CIMP- gliomas which are reported to be more aggressive than their corresponding counterparts. Silencing STYXLI inhibited glioma cell growth, soft agar colony formation, migration, invasion, proliferation, and xenograft tumor growth. Further, ectopic expression of STYXLI was found to promote glioma cell growth, soft agar colony formation, migration, and RasV12 induced in-vitro transformation of immortalized human astrocytes, thus confirming its oncogenic potential in GBM. In this report, we provide a comprehensive overview of deregulation of phosphatases in GBM and demonstrate for the first time, the oncogenic nature of STYXLI in GBM. This study might be useful for treatment of GBM patients with deregulated STYXLI
Effect of Sn Substitution on the Thermoelectric Properties of Synthetic Tetrahedrite
No full textThe present study reports the effect of Sn substitution on the structural and thermoelectric properties of synthetic tetrahedrite (Cu12Sb4S13) system. The samples were prepared with the intended compositions of Cu12Sb4-xSnxS13 (x = 0.25, 0.35, 0.5, 1) and sintered using spark plasma sintering. A detailed structural characterization of the samples revealed tetrahedrite phase as the main phase with Sn substituting at both Cu and Sb sites instead of only Sb site. The theoretical calculations using density functional theory revealed that Sn at Cu(1) 12d or Cu(2) 12e site moves the Fermi level (E-F) toward the band gap, whereas Sn at Sb 8c site introduces hybridized hole states near E-F. Consequently, a relatively high optimum power factor of 1.3 mW/mK(2) was achieved by the x = 0.35 sample. The Sn-substituted samples exhibited a significant decrease in the total thermal conductivity (kappa(T)) compared to the pristine composition (Cu12Sb4S13), primarily because of reduced electronic thermal conductivity. Due to an optimum power factor (1.3 mW/mK(2)) and reduced thermal conductivity (0.9 W/mK), a maximum zT of 0.96 at 673 K was achieved for x = 0.35 sample, which is nearly 40% increment compared to that of the pristine (Cu12Sb4S13) sample
Diplatinum(II) Catecholate of Photoactive Boron-Dipyrromethene for Lysosome-Targeted Photodynamic Therapy in Red Light
No full textThe binuclear platinum(II) boron-dipyrromethene (BODIPY) complex {Pt(dach)}(2)(mu-Dcrb)] (DP), where dach is 1,2-diaminocyclohexane and H(4)Dcrb is a morpholine-conjugated BODIPY-linked dicatechol bridging ligand, was prepared for lysosome organelle targeting and near-IR (NIR) light (600-720 nm) induced photocytotoxic activity. The platinum complex Pt(dach)(cat)] (CP), where H(2)cat is catechol, was synthesized and used as a control complex without bearing the BODIPY unit. The complex DP displayed a band at 660 nm (epsilon = 2.1 X 10(4) M-1 cm(-1)) in the red region of the UV visible spectrum recorded in 10% dimethyl sulfoxide/Dulbecco's Modified Eagle's Medium (DMSO/DMEM, pH 7.2). The complex DP and the BODIPY ligand displayed emission in 10% DMSO DMEM (pH 7.2) giving an lambda(em) value of 668 nm (lambda(ex) = 650 nm) with a Phi(F) value of 0.02 for DP and 0.16 for H(4)Dcrb (Phi(F), fluorescence quantum yield). Titration experiments using 1,3-diphenylisobenzofuran (DPBF) indicated that the complex DP and H(4)Dcrb on irradiation with near-IR light of 600-720 nm generated singlet oxygen (O-1(2)) as the ROS (reactive oxygen species). The complex DP showed significant lysosomal localization and remarkable apoptotic photodynamic therapy (PDT) effects, giving half-maximal inhibitory concentration values (IC50) within 0.6-3.4 mu M in HeLa cervical cancer, A549 lung cancer, and MDA-MB231 multidrug resistant cancer cells, while being essentially nontoxic in the dark and in the HPL1D immortalized lung epithelial normal cells. The acridine orange assay using A549 cells showed lysosomal membrane permeabilization by the complex DP under near-IR light (600-720 nm). This complex on near-IR light (600-720 nm) activation in A549 cells induced apoptotic cell death, as observed from an Annexin-V FITC assay