Journal of Interface, Thin Film and Low Dimension Systems
Volume:3 Issue: 1, Summer-Autumn 2019

Theoretically, graphene quantum dot (GQD) has proved to feature in severalimportant applications during recent decades. Generally, quantum dot, which isof nano-scale size is comparable to the size of atoms and molecules, havingdifferent properties from the bulk of the same materials. In Nano scales, theelectrical, optical, thermodynamic, and mechanical properties of samples aredirectly related to the number of atoms constituting the sample, regarding sizeand shape (type of edge, forms, and dimensions). In this paper three differentstructures of GQDs with zigzag edges (Benzene, Coronene, andCircumcoronene) have been considered and simulated using the DFT theory byapplying PBE functional in order to extract the thermal energy, electronicenergy, heat capacity, polarizability, and entropy of each structure. Themodification of each property with respect to the number of atoms in the GQDare investigated, linear and nonlinear variations of these properties with respectto the atom number are observed. Comparative study of Raman spectroscopybetween PBE and B3LYP functionals is studied for each size of the consideredGQDs. Also, revolution of the G peak in each case has been separatelyinvestigated. All calculations are done by using the Gaussian 09W softwarepackage based on 3-21G Gaussian basis sets.

Tellurium nanostructures have attracted much interest due to their interestingproperties such as gas sensing, photoconductivity, nonlinear optical response, andhigh thermoelectric or piezoelectric responses. Crystalline Tellurium nanowires weresuccessfully synthesized at 10-1 mbar, 10-2 mbar, and 10-3 mbar pressures by thin filmfabrication via evaporation of Tellurium powder and its condensation on glasssubstrates at different temperatures in a tube furnace. The morphology and size of theproducts were studied using field emission scanning electron microscopy (FESEM).The synthesized nanowires have diameters between 46 and 100 nm and lengths up toseveral micrometers. X-Ray diffractometry (XRD) was carried out to characterizecrystal structure of the products. The peaks of the diffractogram were successfullyindexed assuming the hexagonal crystal structure of Tellurium.

In this study, ZnO nanoparticles in three shapes, spherical, rod, and sheet aresynthesized by a hydrothermal method using three different surfactants, namely threeethanol amine, cetyl three methyl ammonium bromide, and sodium dodecyl sulfate. Inall cases, the chemical composition, powder identification, morphology. and particlesize of the final product are characterized by Fourier transform infrared (FTIR), X-raydiffraction (XRD), field emission scanning electronic microscopy (FESEM), EDXelemental analysis, and UV-Vis spectroscopy. The photocatalytic activity of thenanoparticles are investigated for degradation of organic pollutants (Congo red dye).The removal tests of Congo red as a water organic pollutant indicates photocatalyticactivity and absorption ability of synthesized zinc oxides. Finally, the comparison ofthe dye removal results show that the rod nanoparticle has more efficiency in thedegradation of Congo red with 97% yield over 2 hours at pH=8.

We propose a full optical method for gas sensing by few-layer MoS2 nanosheetsobtained by liquid-phase epitaxy (LPE). Our samples are fully characterized bytransmission electron microscopy (TEM), photoluminescent (PL) spectroscopy, and Xraydiffraction (XRD). Further characterization and evaluation of gas sensingapplication, had been done by implementing ultraviolet-visible spectroscopy (UV/Vis).For CO2 gas which acts as a donor to our sample (based on the evaluation method thatused in this work), we calculate the response in the visible region equal to 15% whilein longer wavelengths (near-infrared) the response clearly decreased. Our experimentsshow that using 2D transitional metal dichalcogenide (TMDC) materials for Gassensing applications may open a new horizon for using this kind of 2D material invarious types of optical sensors.

< p>Here, we study the effect of the optical intensity, external magnetic field, well numberand quantum ring thicknesses on the optical absorption of AlN/GaN constant radiusmulti-wells quantum rings. We show that when the intensity increases, the totalabsorption coefficient reduces. This fact is independent of the inner quantum ringradius Rin, magnetic field, and number of wells. The total absorption coefficientreduces monotonically when the number of wells increases. However, the system withRin=400 Å at zero magnetic field is an exception. In this system, if the number ofwells increases, the total absorption coefficient firstly decreases and then increases.By increasing Rin, the total absorption coefficient monotonically reduces. Thismonotonic decreasing behavior exists for systems with more number of wells andhigher magnetic fields. At fixed Rin and for systems with greater number of wells andhigher values Rin, the total absorption coefficient monotonically decreases when themagnetic field increases. Finally, at lower magnetic fields, the total absorptioncoefficient decreases more rapidly than in higher magnetic fields.

PbS thin films were grown on glass substrates by chemical bath deposition (CBD) using lead nitrate, thiourea and sodium hydroxide in aqueous solutions during different deposition times (30-150 min.). The microstructure and morphology of the films were investigated using X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy. The results indicate that deposition time is an important parameter in determining the dominant mechanism of deposition and consequently the characteristics of the film. The active deposition mechanism changes from cluster to ion-by-ion mechanism during the deposition reaction. Therefore, film properties such as shape, size, roughness and preferred orientation change completely.