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Two dimensional (2D) CsPb2Br5 have been successfully synthesized via the chemical precipitation method. Detailed structural, morphological, optical, and dielectric studies of these materials have been performed. These 2D CsPb2Br5 plates (of thickness around 200-300 nm) are ascribed to a tetragonal lattice system with I4/mcm space group. The dielectric attributes such as dielectric constant, electrical modulus, loss factor, and the DC, and AC conductivities, are observed to be varying appreciably with temperature over an extensive frequency window of 10 Hz -50 MHz. The Nyquist plots are investigated using the Maxwell–Wagner equivalent circuit model, which shows the impact of grains and grain boundaries on the overall impedance. Both the free charge conductivity and space charge increase with an increment in temperature, as revealed from the modified Cole-Cole plot. The relaxation time and relaxation mechanism of 2D CsPb2Br5 are estimated using the Kohlrausch-Williams-Watts (KWW) equation. Variation in DC conductivity and relaxation time, as a function of temperature, closely resembles Arrhenius' behavior. Value of activation energy calculated from the DC conductivity corroborates with the same derived from relaxation time. The observation of high dielectric constant and nominal dielectric loss for CsPb2Br5 perovskite offers enormous potential in energy harvesting and storage devices.

Magnetic nanostructures are often considered as highly functional materials because they exhibit unusual magnetic properties under different external conditions. We study the effect of surface pinning on the core-shell magnetic nanostuctures of different shapes and sizes considering the spininteraction to be Ising-like. We explore the hysteresis properties and find that the exchange bias, even under zero field cooled conditions, increases with increase of, the pinning density and the fraction of up-spins among the pinned ones. We explain these behavior analytically by introducing a simple model of the surface. The asymmetry in hysteresis is found to be more prominent in a inverse core-shell structure, where spin interaction in the core is antiferromagnetic and that in the shell is ferromagnetic. These studied of inverse core-shell structure are extended to different shapes, sizes, and different spin interactions, namely Ising, XY-and Heisenberg models in three dimension. We also briefly discuss the pinning effects on magnetic heterostructures. arXiv:1909.10358v1 [cond-mat.mes-hall]

The potential use of halide perovskite materials in ferroelectric and piezoelectric devices has recently been unraveled, but for widespread applications, detailed and systematic experiments are essential. We report on a...

We investigate the physicochemical interactions of gold nanorod (GNR) with single-stranded, double-stranded, and hairpin DNA structures to improve the biological compatibility as well as the therapeutic potential, including the photothermal effect of the conjugates. Studies have demonstrated that different DNA secondary structures, containing thiol group, have different patterns of physicochemical interaction. Conjugation efficiency of paired oligonucleotides are significantly higher than that of oligonucleotides with naked bases. Furthermore, hairpin-shaped DNA structures are most efficient in terms of conjugation and increased dispersion, with least interference on GNR near-infrared absorbance and photothermal effect. Our conjugation method can successfully exchange the overall coating of the GNR, attaching the maximum number of DNA molecules, thus far reported. Chemical mapping depicted uniform attachment of thiolated DNA molecules without any topological preference on the GNR surface. Hairpin DNA-coated GNR are suitable for intracellular uptake and remain dispersed in the cellular environment. Finally, we conjugated GNR with 5-fluoro-2′-deoxyuridine-containing DNA hairpin and the conjugate demonstrated significant cytotoxic activity against human cervical cancer cell line (KB). Thus, hairpin DNA structures could be utilized for optimal dispersion and photothermal effect of GNR, along with the delivery of cytotoxic nucleotides, developing the concept of multimodality approach.

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Despite of the recent advancements on memory devices, quest for the building materials having low-power consumption is still on with the ultimate focus over durability of system and reliability and...

In the present study, we report the development of poly (vinyl alcohol) (PVA) and chitosan oligosaccharide (COS)-based novel blend films. The concentration of COS was varied between 2.5–10.0 wt% within the films. The inclusion of COS added a brown hue to the films. FTIR spectroscopy revealed that the extent of intermolecular hydrogen bonding was most prominent in the film that contained 5.0 wt% of COS. The diffractograms showed that COS altered the degree of crystallinity of the films in a composition-dependent manner. As evident from the thermal analysis, COS content profoundly impacted the evaporation of water molecules from the composite films. Stress relaxation studies demonstrated that the blend films exhibited more mechanical stability as compared to the control film. The impedance profiles indicated the capacitive-dominant behavior of the prepared films. Ciprofloxacin HCl-loaded films showed excellent antimicrobial activity against Escherichia coli and Bacillus cereus. The prepared films were observed to be biocompatible. Hence, the prepared PVA/COS-based blend films may be explored for drug delivery applications.