Halide Ion Mixing across Colloidal 2D Ruddlesden-Popper Perovskites: Implication of Spacer Ligand on Mixing Kinetics.

Halide ion exchange seen in metal halide perovskites provide a substantial opportunity to control their halide composition and corresponding optoelectronic properties. Halide ion mixing across colloidal 3D perovskite nanocrystals have been extensively studied while the mixing within colloidal 2D counterparts remain underexplored. In this study, the halide ion exchange kinetics across colloidally stable 2D Ruddlesden-Popper layered bromide (Br) and iodide (I) perovskites using two different spacer ligands such as aromatic phenethylammonium (PEA) versus linear butyammonium (BA) is demonstrated. The halide exchange kinetic rate constant (k), as determined by tracking time-dependent absorbance changes, indicates that Br/I halide mixing in 2D PEA-based perovskites (2.7 × 10-3 min-1 ) occurs at an order of magnitude slower than in 2D BA-based perovskites (3.3 × 10-2 min-1 ). Concentration (≈1 mM to 100 mM) and temperature-dependent (50 to 80 °C) kinetic studies further allow for the determination of activation barrier for halide ion mixing across the 2D layered perovskites with 75.2 ± 4.4 kJ mol-1 (2D PEA) and 57.8 ± 7.8 kJ mol-1 (2D BA), respectively. The activation energy reveals that the type of spacer cations plays a crucial role in controlling the halide ion mobility and halide stability due mainly to the internal ligand chemical interaction within 2D structures.

Novel tumor localization model and prediction of ablation zone using an intertwined helical antenna for the treatment of hepatocellular carcinoma.

Hepatocellular carcinoma has been the leading cause of death in recent centuries and with the advent of newer technologies, several thermal and cryo-ablation techniques have been introduced in the recent past. In this regard, microwave ablation has developed into a promising method for thermal ablation technique. However, due to clinical obligations, in-vivo analysis is not feasible and ex-vivo analysis is inaccurate due to changes in the electrical and thermal properties of the tissue. Therefore, in this study, temperature-dependent permittivity, electrical conductivity, and thermal conductivity along with phase change effect due to temperature reaching above 100°C are incorporated using finite element method model. Further, using an intertwined normal mode helical antenna ablation probe, a change in resonant frequency (Δf) and reflection coefficient (ΔS11 ) from the actual value (antenna parameter in the air at 5 GHz) is modeled using second-order polynomial curve fitting to predict the surrounding permittivity in the range of 30-70. A maximum deviation of 0.8 value in permittivity from the actual value is observed. However, to obtain a generalized methodology, XG Boost and CAT Boost algorithms are used. Further, since ablation diameter plays a crucial role in achieving optimal tumor ablation, an artificial neural network (ANN) algorithm with three different optimizers is incorporated to predict ablation diameter using five critical parameters. Such an ANN algorithm which can predict the transversal and axial ablation zone may provide optimal ablation outcomes.

Graphene-Induced Room Temperature Ferromagnetism in Cobalt Nanoparticles Decorated Graphene Nanohybrid.

Control over the magnetic interactions in magnetic nanoparticles (MNPs) is a crucial issue to the future development of nanometer-sized integrated "spintronic" applications. Here, we have developed a nanohybrid structure to achieve room temperature ferromagnetism, via a facile, effective, and reproducible solvothermal synthesis method. The plan has been put onto cobalt (Co) NPs, where the growth of Co NPs on the surface of reduced graphene oxide (rGO) nanosheets switches the magnetic interactions from superparamagnetic to ferromagnetic at room temperature. Switching-on ferromagnetism in this nanohybrid may be due to the hybridization between unsaturated 2pz orbitals of graphene and 3d orbitals of Co, which promotes ferromagnetic long-range ordering. The ferromagnetic behavior of Co-rGO nanohybrid makes it excellent material in the field of spintronics, catalysis, and magnetic resonance imaging.

Molybdenum Disulfide-Wrapped Carbon Nanotube-Reduced Graphene Oxide (CNT/MoS2-rGO) Nanohybrids for Excellent and Fast Removal of Electromagnetic Interference Pollution.

Electromagnetic interference (EMI) pollution has now become a subject of great concern with the rapid development of delicate electronic equipment in commercial, civil, and military operations. There has been a surge in pursuit of light-weight, adaptable, effective, and efficient EMI screening materials in recent years. The present article addresses a simple and sensitive approach to synthesize a core/shell carbon nanotube/MoS2 heterostructure supported on reduced graphene oxide (CNT/MoS2-rGO nanohybrid) as an efficient electromagnetic shielding material. The structural and morphological characteristics were accessed through X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy, augmenting successful formation of the CNT/MoS2-rGO nanohybrid. The shielding performance of the as-synthesized samples has been accessed in a wide frequency range of 8-12 GHz. A CNT/MoS2-rGO nanohybrid demonstrates a better EMI shielding performance in comparison to MoS2 nanosheets and MoS2-rGO nanohybrid individually. The CNT/MoS2-rGO nanohybrid having a thickness ∼1 mm shows excellent total shielding effectiveness (SET) as high as 40 dB, whereas MoS2 and MoS2-rGO hybrid lags far, with the average value of SET as 7 and 28 dB, respectively. It also demonstrates that the nanohybrid CNT/MoS2-rGO shields the EM radiation by means of absorption through several functional defects and multiple interfaces present in the heterostructure. Herein, we envision that our results provide a simple and innovative approach to synthesize the light-weight CNT/MoS2-rGO nanohybrid having flexibility and high shielding efficiency and widen its practical applications in stealth technology.

CdSe- Reduced graphene oxide nanocomposite toxicity alleviation via V2O5 shell formation over CdSe core: in vivo and in vitro studies.

The present article demonstrates the synthesis of the nanocomposite of reduced graphene oxide (rGO) with CdSe and CdSe/V2O5 core/shell quantum dots by a two-step facile synthesis approach and subsequently studies their relative biocompatibility in different cells. Various characterization techniques have been applied including transmission electron microscopy (TEM), an x-ray diffractometer (XRD) and Raman spectroscopy to confirm the successful formation of CdSe-rGO and CdSe/V2O5-rGO nanocomposites. The average sizes of CdSe and CdSe/V2O5 QDs have found to be ∼3 and 5.5 nm, respectively with a good dispersion over the surface of rGO nanosheets. A crystal phase change has occurred during the formation of the V2O5 shell over the surface of CdSe QDs and confirmed through XRD. Raman spectroscopy has shown some useful insight of the surface state of CdSe and consequent changes in the surface with V2O5 shell growth. Further, MTT and cell growth assays have been performed to analyze their biocompatibility in A549 and Hela cells with various concentrations of as-synthesized materials. Our results demonstrate the toxicity of CdSe-rGO nanocomposite to be substantially reduced by the growth of the V2O5 shell. The in vivo studies in Drosophila show a remarkable decrease in the reactive oxygen species (ROS) and apoptosis levels for a CdSe/V2O5-rGO composite as compared to a CdSe-rGO nanocomposite, which paves a promising pathway for the CdSe/V2O5-rGO nanocomposite to be used as an efficient biocompatible material.

Investigation of Photophysical Properties of Ternary Zn-Ga-S Quantum Dots: Band Gap versus Sub-Band-Gap Excitations and Emissions.

Highly luminescent ternary Zn-Ga-S quantum dots (QDs) were synthesized via a noninjection method by varying Zn/Ga ratios. X-ray diffraction and Raman investigations demonstrate composition-dependent changes with multiple phases including ZnGa2S4, ZnS, and Ga2S3 in all samples. Two distinct excitation pathways were identified from absorption and photoluminescence excitation spectra; among them, one is due to the band-gap transition appearing at around 375 and 395 nm, whereas another one observed nearby 505 nm originates from sub-band-gap defect states. Photoluminescence (PL) spectra of these QDs depict multiple emission noticeable at around 410, 435, 461, and 477 nm arising from crystallographic point defects formed within the band gap. The origin of these defects including zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), sulfur vacancies (VS), and gallium vacancies (VGa) has been discussed in detail by proposing an energy-level diagram. Further, the time-dependent PL decay curve strongly suggests that the tail emission (appear around 477 nm) in these ternary QDs arises due to donor-acceptor pair recombination. This study enables us to understand the PL mechanism in new series of Zn-Ga-S ternary QDs and can be useful for the future utilization of these QDs in photovoltaic and display devices.

CdSe/V2O5 core/shell quantum dots decorated reduced graphene oxide nanocomposite for high-performance electromagnetic interference shielding application.

The present work reports nanocomposite of CdSe/V2O5 core-shell quantum dots with reduced graphene oxide (rGO-V-CdSe), as an efficient lightweight electromagnetic wave shielding material, synthesized by a simplistic solvothermal approach. The as-synthesized nanocomposite was analyzed for its structural, compositional and morphological features by x-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy and x-ray photoelectron spectroscopy (XPS). The measurement of complex permittivity/permeability and total shielding efficiency of the as-synthesized samples has been done in a wide frequency range of 8-12 GHz (X-band). Compared to rGO and rGO-CdSe, rGO-V-CdSe nanocomposite exhibits significantly enhanced EMI shielding properties in terms of both dielectric loss and total shielding SE T . The high value of real permittivity (average ε'∼70) and the overall shielding effectiveness up to ∼38 dB have been recorded for rGO-V-CdSe nanocomposite. The studies also infer that the absorption contributes more in total shielding than reflection. The high value of dielectric loss and shielding effectiveness could also be attributed to the presence of various defects leading to dipolar and interfacial polarizations. The excellent EMI shielding properties of the nanocomposite in GHz frequency range (X-band) pave an intuitive way for fabricating a versatile EMI shielding nanocomposite material for applications.

Ultrafast charge carrier dynamics in CdSe/V2O5 core/shell quantum dots.

Ultrafast transient absorption (TA) spectroscopy has been carried out to study the charge carrier dynamics of CdSe core and CdSe/V2O5 core/shell quantum dots (QDs). A significant redshift accompanied by broadening in the first excitonic peak was observed in the UV-Vis absorption spectra of the core/shell QDs as the shell thickness increases. This interesting observation is related to a quasi-type-II alignment characterized by the spatial separation of an electron into the core/shell and a hole into the core. The observed optical excitonic spectra have further been used to study the energetics of CdSe and charge separated states with the concept of Marcus theory and confirmed that electron transfer takes place in the Marcus inverted region (). Moreover, the growth kinetics of the CdSe core and CdSe/V2O5 core/shell QDs, studied with TA spectroscopy, exhibits slow electron cooling in core/shell QDs because of the de-coupling of the electronic wave functions with their hole counterpart. These exciting properties reveal a new paradigm shift from CdSe QDs to CdSe/V2O5 core/shell QDs for highly suitable applications in photovoltaics (PV) and optoelectronic devices.