Silver nanoparticles within a host polymer of chitosan were synthesized by using in situ method. Ultraviolet-visible spectroscopy was then carried out for the prepared chitosan : silver triflate (CS : AgTf) samples, showing a surface plasmonic resonance (SPR) peak at 420 nm. To prepare polymer composites with reduced energy band gap, different amounts of alumina nanoparticles were incorporated into the CS : AgTf solution. In the present work, the results showed that the reduced silver nanoparticles and their adsorption on wide band gap alumina (Al 2 O 3 ) particles are an excellent approach for the preparation of polymer composites with small optical band gaps. The optical dielectric loss parameter has been used to determine the band gap experimentally. The physics behind the optical dielectric loss were interpreted from the viewpoint of quantum mechanics. From the quantum-mechanics viewpoint, optical dielectric loss was also found to be a complex equation and required lengthy numerical computation. From the TEM investigation, the adsorption of silver nanoparticles on alumina has been observed. The optical micrograph images showed white spots (silver specks) with different sizes on the surface of the films. The second semicircle in impedance Cole-Cole plots was found and attributed to the silver particles.
The PEO-based polymer nanocomposites were prepared by solution cast method. Green approaches were used for synthesis of carbon nanodots (CNDs) and silver nanoparticles (Ag NPs). It was found that the crystallite size of spherulites of PEO was greatly scarified upon incorporation of CNDs and Ag NPs. In the present work, in opposition to other studies, broadening of surface plasmon resonance (SPR) peak of metallic Ag NPs in PEO-based polymer composites was observed rather than peak tuning. Various techniques, such as powder X-ray diffraction (XRD), SEM, UV–Vis spectroscopy, and photoluminescence (PL), were used to characterize the structural, morphological, and optical properties of the samples. Increase of amorphous phase for the PEO doped with CND particles was shown from the results of XRD analyses. Upon the addition of suspended Ag NPs to the PEO:CNDs composites, significant change of XRD peak position was seen. A field-emission scanning electron microscope (FESEM) was used to investigate the surface morphology of the samples. In the SEM, a significant change in the crystalline structure was seen. The size of PEO spherulites in the PEO nanocomposite samples became smaller and the percentage of amorphous portion became larger, owing to the distribution of CNDs and Ag NPs. The UV–Vis absorption spectra of the PEO-based polymer were found to improve and shift to higher wavelengths upon incorporation of CNDs and Ag NPs into the PEO matrix. The SPR peak broadening in the UV–Vis spectra was observed in the PEO:CNDs composites due to the Ag NPs. The absorption edge value of PEO was found to shift toward lower photon energy as the CNDs and Ag NPs are introduced. The photoluminescence (PL) spectra were also observed for the PEO:CNDs and PEO:CNDs:Ag samples and found to be more intense in the PEO:CNDs system than in the PEO:CNDs:Ag system. Lastly, the optical band gap of the samples was further studied in detail using of Tauc’s model and optical dielectric loss parameter. The types of electron transition were specified.
Modified Callaway's theory was used to calculate lattice thermal conductivity (LTC) of Germanium nanowires. Results are compared to those of experimental values of the temperature dependence of LTC for nanowire diameters of 62, 19, and 15nm. In this calculation, both longitudinal and transverse modes are taken into account. Scattering of phonons is assumed to be by nanowire boundaries, imperfections, dislocations, electrons, and other phonons via both normal and Umklapp processes. Effect of parameters, phonon confinement and imperfections in limiting thermal conductivity for the nanowires under considerations are investigated. The suppression in thermal conductivity of these nanowires is arise from electron-phonon scattering and phonon-boundary scattering at low temperatures, while at high temperatures is due to imperfections and intrinsic properties.
The film casting method is implemented to synthesize a series of films consisting of polyvinyl alcohol (PVA) films and 4 wt%, 8 wt%, and 12 wt% lead sulfide (PbS) nanoparticles (NPs). X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Ultraviolet-visible (UV-vis) spectroscopy were used to ensure the impact of PbS loading on PVA properties, particularly optical ones. The FTIR results show a decrease in the intensity for all the bands and the XRD results show different features for the composites from that of the pure PVA. The optical properties, including optical transmission, surface reflection, and absorption, were investigated. Additionally, the significant optical parameters, for instance, the dielectric nature and refractive index of the films, were analyzed. The findings have shown that PbS NPs in the PVA films decrease UV and visible transmission through polymer composites and increase their ability to reflect the incident light. Tauc’s equation is applied to determine the optical bandgap energy (Eg) and verify whether it is direct or indirect. Using the relation between photon energy and optical dielectric loss, the Eg was measured and the type of electron transition was measured, which eases the exponent value (𝜸) specification from Tauc’s method. The Eg decreases from 6.3 eV to 5.25 eV when PbS NPs are added. The refractive index is improved from 1.27 to 2.16 for the polymer nanocomposite (NCPs) film with optimum PbS NPs. Then, the Wemple–DiDomenico model corresponding to a single oscillator is applied to the dispersive medium to determine the refractive index dispersion. Both the dispersive energy (Ed) and single-oscillator energy (Eo) are evaluated accurately. Moreover, the variation of both real and imaginary parts of the dielectric constant of polymer films were studied. Finally the optical parameters such as charge density, dielectric constant at high frequencies, optical mobility (µ), angular frequency (ωp), optical resistivity (ρ), and relaxation time (τ) of electrons are shown quantitatively. The ωp of the electron is increased from 1.06 × 1029 to 81.5 × 1029 Hz when the PbS NPs is added. The µ of the electrons is also increased from 4.85 to 6.22 cm2/(V·s) by adding the PbS NP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.