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In the pursuit of lead-free perovskite materials suitable for harnessing solar energy, a recent discovery has emerged regarding Cs2TiBr6. This compound has garnered attention as a prospective candidate, exhibiting favorable optical and electrical characteristics alongside exceptional resilience when subjected to environmental strains. This study details the successful synthesis of non-hazardous metal halide nanoparticles of Cs2TiBr6via the slow cooling method. Comprehensive investigations into the structural, optical, and dielectric characteristics have been undertaken. The temperature sensitivity of various electrical properties, including the dielectric constant, loss factor, electric modulus, and AC/DC conductivity, is evident in this perovskite material. This phenomenon is observed across a frequency range of 1 to 107 Hz. Furthermore, examination of the Nyquist plot highlights the distinctive contributions of both grain and grain boundaries to the overall impedance characteristics. In the high-frequency range, it is observed that the dielectric constant exhibits an upward trend as the temperature rises. Examination of the adapted Cole-Cole plot unveils that both space charge and free charge conductivity escalate with increasing temperature, while concurrently, the relaxation time experiences a reduction with the temperature's ascent. We observed an asymmetrical pattern in the electric modulus spectra at varying temperatures using a modified Kohlrausch-Williams-Watts equation. This asymmetry is consistent with the inherent non-Debye nature of perovskite materials. Additionally, as the temperature increases, we note a shift in the imaginary component of the electric modulus spectra, transitioning from a non-Debye character towards a semi-Debye nature, though it does not achieve a strictly Debye-type response. This transformation indicates the semiconducting properties of the material. We elucidate the AC conductivity behavior in Cs2TiBr6 by employing the non-overlapping small-polaron tunneling (NSPT) mechanism as the basis. The activation energy, as determined from both the modulus spectra and DC conductivity, aligns closely, providing robust evidence for the congruence between the relaxation dynamics and the conduction mechanism. In addition to these attributes, Cs2TiBr6 exhibits a substantial dielectric constant coupled with negligible dielectric loss, thus establishing its potential suitability for energy harvesting devices.
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This study offers an extensive exploration into approaches for cultivating CsPbBr3 SCs using inverse temperature crystallization (ITC), with a specific focus on seed-induced (method (1)) and nucleation-mediated (method (2)) growth techniques. Our findings reveal that leveraging seed-assisted growth at lower temperatures yields noteworthy enhancements in the material's optical and electrical behaviors, outperforming the outcomes achieved through nucleation-driven growth. Concretely, through the employment of the space charge limited current (SCLC) technique, an evident contrast emerges in the trap-populated threshold voltage between the seed-facilitated crystal (SC1) (measuring 0.309 V) and its nucleation-facilitated counterpart (SC2) (measuring 1.513 V), consequently giving rise to discernable dissimilarities in trap density assessments. Evidence from temperature-dependent analysis of space charge limited currents substantiates these findings, revealing trap density values of 8.81 × 109 cm-3 for SC1, juxtaposed with 2.08 × 1010 cm-3 for SC2. Additionally, the SC1 displays a notably diminished trap energy level. Furthermore, the investigation underscores the affirmative influence of method (1) at lower temperatures on the optical and crystalline characteristics of the substance. This effect is evidenced by enhanced photoluminescence (PL) reactions and reduced lattice strain (Ls), as determined through X-ray diffraction (XRD) techniques. Moreover, the research establishes the substantial impact of this enhanced crystallization technique on the photodetector (PD) attributes of the crystal. This effect induces elevated levels of detectivity and responsivity for method (1).
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Lately, double perovskite materials have become well-known in the commercialization area owing to their potential use in optoelectronic applications. Here, double perovskite Cs2AgSbCl6 single crystals (SCs) with cubic crystal structure and Fm3Ìm space group were successfully synthesized via the slow cooling technique. This paper investigates the dielectric relaxation and charge transfer mechanism within Cs2AgSbCl6 using electrochemical impedance spectroscopy (EIS) in the 273-393 K temperature range under light. The dielectric response in Cs2AgSbCl6 has been explained by the space charge polarization and the ionic motion. The ε'(ω) study at different temperatures shows a remarkable frequency transition at which dε'/dT changes from a positive to a negative coefficient. Based on Stevels approach, the density of traps diminishes with the temperature increase, which improved conduction. However, this approach proves the polaronic conduction in Cs2AgSbCl6. 0.42 and 0.21 eV are the binding (Ep) and polaron hopping (WH) energy values, respectively. Contrary to free-charge carrier motion, polaron hopping was proposed as the principal conduction process since the ambient-temperature thermal energy was lower than Ep. Moreover, the analysis of M''(ω) and -Z''(ω) as a function of temperature shows the thermally-activated relaxation from the non-Debye to Debye type model in Cs2AgSbCl6. This scientific research offers an essential understanding of the dielectric relaxation behavior, which is required for improving dielectric switches. Also, this paper provides a deep insight into the conduction mechanism within double perovskite materials.
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A study of the magnetic properties of LaNi5 intermetallic compoundand and their effect on desorption reaction was carried out as a function of temperature. A Vibrating Sample Magnetometer (VSM) was used for the magnetic measurements and a Metal Hydrogen Reactor (MHR) supplied by a constant current through a coil was used for the hydrogen desorption reaction under the action of a magnetostatic field. Then, the hysteresis cycle, the first magnetization curve, the thermo-magnetization curves and the desorbed hydrogen mass were determined. The results showed that the application of a magnetic field corresponding to the magnetization at saturation Ms at a given temperature improved the hydrogen desorption reaction by the LaNi5.
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Pyrazole derivatives correspond to a family of heterocycle molecules with important pharmacological and physiological applications. At present, we perform a density functional theory (DFT) calculations and a quantitative structure-activity relationship (QSAR) evaluation on a series of 1-(4,5-dihydro-1H-pyrazol-1-yl) ethan-1-one and 4,5-dihydro-1H-pyrazole-1-carbothioamide derivatives as an epidermal growth factor receptor (EGFR) inhibitory activity. We thus propose a virtual screening protocol based on a machine-learning study. This theoretical model relates the studied compounds' biological activity to their calculated physicochemical descriptors. Moreover, the linear regression function is used to validate the model via the evaluation of Q2ext and Q2cv parameters for external and internal validations, respectively. Our QSAR model shows a good correlation between observed activities IC50 and predicted ones. Our model allows us to mitigate time-consuming problems and waste chemical and biological products in the preclinical phases.
Asunto(s)
Teoría Funcional de la Densidad , Pirazoles/farmacología , Relación Estructura-Actividad Cuantitativa , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/metabolismo , Humanos , Modelos Moleculares , Pirazoles/síntesis química , Pirazoles/químicaRESUMEN
In this work, mixed convection and entropy generation analyses in a partitioned porous cavity with double inner rotating cylinders are explored under magnetic field effects. A curved partition shape is considered with identical rotating cylinders and an inclined magnetic field, while the right vertical wall moves with a constant speed in the y-direction. Numerical simulations are performed by considering various values of Rayleigh number, Hartman number, Darcy number, inclination of the magnetic field, size of the curved partitions, and rotational speeds of the inner cylinders and their vertical locations with the cavity. Complicated flow field with multicellular structures are observed due to the complex interaction between the natural convection, moving wall, and rotational effects of inner cylinders. Improved heat-transfer performance is obtained with higher values of magnetic field inclination, higher values of permeability/porosity of the medium, and higher rotational speeds of the cylinders. Almost doubling of the average Nu number is obtained by decreasing the value of the Hartmann number from 25 to 0 or varying the magnetic field inclination from 90 to 0. When rotational effects of the cylinders are considered, average heat-transfer improvements by a factor of 5 and 5.9 are obtained for nondimensional rotational speeds of 5 and -5 in comparison with the case of motionless cylinders. An optimum length of the porous layer is achieved for which the best heat-transfer performance is achieved. As the curvature size of the partition is increased, better heat transfer of the hot wall is obtained and up to 138% enhancement is achieved. Significant increments of entropy generation are observed for left and right domains including the rotating cylinders. The magnetic field parameter also affects the entropy generation and contributions of different domains including the curved porous partition.