Controlling surface statistical properties using bias voltage: Atomic force microscopy and stochastic analysis

The effect of bias voltages on the statistical properties of rough surfaces has been studied using atomic force microscopy technique and its stochastic analysis. We have characterized the complexity of the height fluctuation of a rough surface by the stochastic parameters such as roughness exponent, level crossing, and drift and diffusion coefficients as a function of the applied bias voltage. It is shown that these statistical as well as microstructural parameters can also explain the macroscopic property of a surface. Furthermore, the tip convolution effect on the stochastic parameters has been examined.Comment: 8 pages, 11 figures

Markov Properties of Electrical Discharge Current Fluctuations in Plasma

Using the Markovian method, we study the stochastic nature of electrical discharge current fluctuations in the Helium plasma. Sinusoidal trends are extracted from the data set by the Fourier-Detrended Fluctuation analysis and consequently cleaned data is retrieved. We determine the Markov time scale of the detrended data set by using likelihood analysis. We also estimate the Kramers-Moyal's coefficients of the discharge current fluctuations and derive the corresponding Fokker-Planck equation. In addition, the obtained Langevin equation enables us to reconstruct discharge time series with similar statistical properties compared with the observed in the experiment. We also provide an exact decomposition of temporal correlation function by using Kramers-Moyal's coefficients. We show that for the stationary time series, the two point temporal correlation function has an exponential decaying behavior with a characteristic correlation time scale. Our results confirm that, there is no definite relation between correlation and Markov time scales. However both of them behave as monotonic increasing function of discharge current intensity. Finally to complete our analysis, the multifractal behavior of reconstructed time series using its Keramers-Moyal's coefficients and original data set are investigated. Extended self similarity analysis demonstrates that fluctuations in our experimental setup deviates from Kolmogorov (K41) theory for fully developed turbulence regime.Comment: 25 pages, 9 figures and 4 tables. V3: Added comments, references, figures and major correction

Photocatalytic upgrading α-Fe2O3 nanoparticles by incorporating MoS2/rGO nanosheets

α -Fe _2 O _3 /MoS _2 /rGO nanocomposites was prepared by a two-step hydrothermal method and characterized by XRD, FESEM, EDS, FTIR, and UV–vis absorption spectroscopy. The results confirmed the formation of α -Fe _2 O _3 /MoS _2 -rGO (10 wt%) nanocomposites were composed of hematite nanoparticles with particle size of 30 nm and MoS _2 /rGO composite nanosheets with maximum sheet thickness of ∼ 10 nm. Upon addition of MoS _2 -rGO (8.0 wt%) nanosheets, the band gap of α -Fe _2 O _3 nanoparticles decreased from 2.3 to 1.7 eV that was accompanied by light absorption enhancement. Owing to synergetic effect between rGO and MoS _2 nanosheets leading to suppression of charge carrier recombination, prolongation of charge carrier lifetime, improvement of the interfacial charge transfer and increase in the number of active sites in α -Fe _2 O _3 nanoparticles, as-synthesized α -Fe _2 O _3 /MoS _2 -rGO (10 wt%) nanocomposites nanocomposite showed highly enhanced photocatalytic performance for Rh B degradation under light irradiation so that complete degradation of Rh B organic dye was achieved within 30 min

Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder

Kamyar Shameli,1,2 Mansor Bin Ahmad,1 Ali Zamanian,2 Parvanh Sangpour,2 Parvaneh Shabanzadeh,3 Yadollah Abdollahi,4 Mohsen Zargar51Department of Chemistry, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; 2Materials and Energy Research Center, Karaj, Iran; 3Department of Mathematics, 4Advanced Materials and Nanotechnology Laboratory, Universiti Putra Malaysia, Serdang, Selangor, Malaysia; 5Department of Biology, Islamic Azad University, Qom, IranAbstract: Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries.Keywords: silver nanoparticles, Curcuma longa, biosynthesis, green synthesis, transmission electron microscop

Tunable bandgap and spin-orbit coupling by composition control of MoS2 and MoOx (x=2 and 3) thin film compounds

We report on the MoS2 and MoOx (x = 2 and 3) composite thin layers, electrodeposited, onto a Florine doped Tin Oxide (FTO) substrate. Our results show a change in relative content of these compounds in different thicknesses ranging from ∼20 to 540 nm. This change in the relative content at different thicknesses leads to a change in optical and electrical properties including bandgap and the type of semiconductivity. A sharp transition from p to n-type of semiconductivity is observed by scanning tunneling spectroscopy measurements. We find that the spin-orbit interaction of Mo 3d electrons in the MoS2 and MoO3 enhances by significant reduction of the MoO3 content in thicker layers

Tunable bandgap and spin-orbit coupling by composition control of MoS2 and MoOx (x=2 and 3) thin film compounds

We report on the MoS2 and MoOx (x = 2 and 3) composite thin layers, electrodeposited, onto a Florine doped Tin Oxide (FTO) substrate. Our results show a change in relative content of these compounds in different thicknesses ranging from ∼20 to 540 nm. This change in the relative content at different thicknesses leads to a change in optical and electrical properties including bandgap and the type of semiconductivity. A sharp transition from p to n-type of semiconductivity is observed by scanning tunneling spectroscopy measurements. We find that the spin-orbit interaction of Mo 3d electrons in the MoS2 and MoO3 enhances by significant reduction of the MoO3 content in thicker layers