We show that photoluminescence properties of PbS nanocrystal thin films are directly related to film morphology and nanocrystal density. In densely packed PbS nanocrystal films, low-temperature donor-to-acceptor energy transfer is mainly responsible for the photoluminescence spectra narrowing and shift toward longer wavelengths. At elevated temperatures, back energy transfer is proposed to be responsible for an unusual photoluminescence intensity temperature dependence. In thin films with a low PbS nanocrystal density, the energy transfer is suppressed, and the effect is dramatically reduced.
Studies on Mg substituted Zn-Cu ferrites with chemical formula of Zn 0.6-Cu 0.4-x Mg x Fe 2 O 4 were synthesized by solid-state reaction technique. The structural phase of all the samples is characterized by XRD, show single phased cubic spinel structure. Density of the samples increases with the increase of Mg quantity. Average grain diameter decreases with increasing Mg content. All samples show soft ferromagnetic behavior as confirmed from the M-H hysteresis loop obtained from the VSM analysis. Thesaturation magnetization decreases with increasing Mg quantity. Increasing and decreasing trend of coercivity with the increase of Mg quantityis observed, which led to the slightly hard magnetic phase. The high frequencies create more effective for the ferrite grains of advanced conductivity and minor dielectric constant for all the samples but the AC electrical resistivity and dielectric constant are initiate to be more operational at lower frequencies. The variation of resistivity, dielectric constant with the Mg concentration is completely related to the porosity and bulk density.
γ-CuBr is a I-VII wide bandgap mixed ionic-electronic semiconducting material with light emitting properties suitable for novel UV/blue light applications. Its structural and physical properties allow for vacuum deposition on a variety of substrates and herein we report on the deposition of γ-CuBr on Si and Indium Tin Oxide (ITO) coated glass substrates via vacuum evaporation with controllable film thickness from 100 nm to 500 nm. Temperature dependent Photoluminescence (PL) characteristics of these γ-CuBr films on Si (100) reveals familiar Z f and I 1 excitonic features. A Thin Film Electroluminescent Device (TFELD) using a γ-CuBr active layer was fabricated and the room temperature Electroluminescence (EL) was obtained for γ-CuBr for the first time. CuBr features relating to known excitonic (Z f , 3.1 eV) emissions were observed as well as a number of previously unknown emissions at 3.81 eV, 3.02 eV, 2.9 eV, 2.75 eV, and 2.1 eV. We speculate on the origins of these peaks and attribute them to the presence of monovalent Cu+ generated during a.c. excitation.
Currently, eco-friendly, cost-effective, and simple synthesis techniques are drawing the attention of nanoparticle researchers. The conversion of silver ions to silver nanoparticles (AgNPs) is carried out using the Adenia trilobata leaf extract, which is capable of acting as an exclusive reducing agent. AgNPs show very crucial antibacterial properties and are nontoxic for humans. The color of the solution changes from light blue to brown, ensuring the formation on nanoparticles. The biosynthesized AgNPs are incorporated into cotton fiber, and their antibacterial activity on gram negative ( E. coli) bacteria has been studied. The UV/Vis and absorption spectroscopy analysis shows a surface plasmon resonance peak at 445 nm. The x-ray diffraction measurement reveals peaks at 38.02 and 44.23, and the average particle size is 18.30 nm. Field emission scanning electron microscopy has been performed to find the size, shape, and morphology of the treated nanoparticles and the AgNP-incorporated cotton fiber. The Fourier transform infrared spectroscopy result shows the presence of functional groups of AgNPs and capping agents. The antibacterial activity on gram negative ( E. coli) bacterial strains for the both cases showed a promising result.
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