Enhanced photocatalytic performance of CuFeO2-ZnO heterostructures for methylene blue degradation under sunlight

One of the strategies to overcome the drawbacks of fast charge recombination of a photocatalyst is to develop semiconductor heterostructures. Herein, we report a two-step precipitation-hydrothermal process to create CuFeO₂-ZnO heterostructures with different weight percentages of CuFeO₂ (0.5, 1, 5, and 10%). Though X-ray diffraction detected the presence of CuFeO₂ on ZnO above 5%, Raman spectroscopy could reveal the presence of CuFeO₂ phase as low as 0.5 wt%. For all of the compositions, the bandgap of ZnO did not vary (3.15 eV) on forming heterostructures with CuFeO₂. The oxidation of methylene blue under sunlight was used to determine the photocatalytic performance of the heterostructures. In comparison to pure ZnO and CuFeO₂, CuFeO₂-ZnO heterostructures exhibited a better photocatalytic efficiency. Overall, 5 wt% CuFeO₂ on ZnO showed 100% degradation with a rate constant of 0.272?±?0.002 min^?1, which is 16 times faster than ZnO. Time-resolved photoluminescence analysis indicated a higher lifespan of charge carriers in the 5wt% CuFeO₂-ZnO heterostructure (32.3 ns) than that of CuFeO₂ (0.85 ns) and ZnO (27.6 ns). The Mott–Schottky flat band potentials of ZnO and CuFeO₂ was determined to be -0.82 and 1.17 eV, respectively, revealing the presence of Type I heterostructures. The heterostructures also showed outstanding recyclability, with a degradation rate of 97% even after four cycles. The current study shows the significance of forming p-type CuFeO₂ and n-type ZnO heterostructures for enhanced photocatalysis.

     

Live video streaming service with pay-as-you-use model on Ethereum Blockchain and InterPlanetary file system

Wireless Networks - In centralized video streaming platforms, the platform owner, rather than the content producer, controls most of the content uploaded on the centralized video...     

A survey and classification of controller placement problem in SDN

Software defined networking emerges as a promising paradigm shift that decouples the control plane from the data plane. It has the ability to centrally monitor and control the network through softwarization, ie, controller. Deploying a single controller is inefficient to handle large network traffic; thereby, making multiple controllers are a necessity of current software defined networking in wide area networks. Placing multiple controllers in an optimum way, ie, controller placement is a vibrant research problem. Controller placement problem (CPP) is of twofold: the minimum number of controllers to be placed in a network and locations of these controllers. Numerous researchers in the last 5 years (2012 to November 2017) have proposed solutions for the CPP, which is an NP‐hard problem. In general, solutions are based on objective functions and their optimum solutions considering various factors (such as propagation latency between switches and controllers, and intercontrollers) and constraints (such as the capacity of controllers and switches). To the best of our knowledge, this is the first attempt of state‐of‐the‐art review on CPP. This paper classifies the CPP, critically analyzes the existing solutions, and finds limitations and future scope existing, which will help potential researchers in this area to innovate new solutions for CPP lying on this information.     

Security Attacks in Named Data Networking: A Review and Research Directions

Journal of Computer Science and Technology - Contents such as audios, videos, and images, contribute most of the Internet traffic in the current paradigm. Secure content sharing is a tedious issue....     

Formal modeling and verification of software‐defined networks: A survey

Unlike traditional networking devices, control and management plane are decoupled from data plane in software‐defined networks (SDN). The logically centralized control and management plane facilitate dynamic orchestration of network resources, services, and policies by writing software programs. This provides much needed flexibility and programmability where networking rules and policies can be modified dynamically depending upon the application context. As the operation of network services entirely depends on a program, a small fault may induce several issues which can adversely affect the expected behavior of the network. Formal modeling and verification help in catching inconsistencies and existence of errors prior to the deployment of the programs that control the behavior of a network. In this paper, we provide a comprehensive survey of tools and techniques available in the literature for formal modeling and verification of SDN. These tools and techniques are classified based on their types, the components of SDN where they can be applied, and the design and development phase when they are utilized. In particular, their respective benefits and limitations are discussed in terms of ease of use, interfaces, and the ability to capture and verify intended network properties.     

A compact four‐element MIMO antenna for WLAN/WiMAX/satellite applications

This paper presents a four‐element wideband monopole MIMO antenna. Initially, a single‐element wideband CPW‐fed antenna is designed operating in the range of 4.30 to 6.45 GHz. Using this design, an approach towards MIMO structure is studied. A two‐element structure is designed keeping them adjacent to each other, and the isolation between the antennas is observed. After which, a four‐element structure is designed having the best orientation in order to achieve good isolation between the antenna elements. The proposed antenna configuration has four identical CPW‐fed elements. The proposed configuration has a fractional bandwidth of 40.27% and has a simulated peak gain of 5.5 dBi. This antenna is intended to be used for WLAN, WiMAX, and satellite bands of range corresponding to 4.70–6.19, 5.5–5.7, and 5–6 GHz. All the necessary antenna simulations are simulated using Ansys HFSS and verified on NI AWR Design Environment. The fabricated model of the proposed design is measured for its performance parameters and validated.     

Structural and optical absorption studies of cobalt substituted strontium ferrites,SrCo<Subscript>x</Subscript>Fe<Subscript>12−x</Subscript>O<Subscript>19</Subscript> (x = 0.1, 0.2 and 0.3)

Cobalt substituted strontium ferrites SrCo_xFe_12?xO₁₉ (x = 0.1, 0.2 and 0.3) were synthesized via sol–gel method and the dried gel obtained was annealed at 800 °C. The powder X-ray diffraction studies helped in the determination of the crystallite size that measured ≈ 12–14 nm. The optical properties of the powdered nanoparticles were determined by means of the UV–Vis absorption spectra of their dispersed solutions in liquid media. Despite these measurements, it was difficult to determine their band gap (E_g) precisely. However, the Kubelka–Munk treatment on the diffuse reflectance spectra of the powdered nanoparticles was used in order to extract their E_g unambiguously. The Co substituted strontium hexaferrites are used for optical studies. The energy band gap for all the ferrite compositions was found to be ≈ 1.46–1.78 eV. The study made on the dielectric behaviour of the substituted SrFe₁₂O₁₉ is also discussed in this paper.     

Structural,electrical and magnetic properties of Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>/MgO nanocomposite

The present paper deals with the synthesis of Mn₃O₄/MgO nanocomposite through a simple sol–gel route and their electrical and magnetic properties are discussed for electrode applications. The grain size and particle morphology of the synthesized nanocomposite are characterized using XRD and HRSEM. The elemental compositions of the synthesized samples were analyzed using EDAX spectra. The dielectric constant, dielectric loss and AC conductivity of the synthesized samples were studied in the frequency range of 100 Hz–5 MHz at different temperatures (303–573 K) using impedance spectra. The activation energy was calculated using Arrhenius plot. The vibrating sample magnetometry (VSM) study shows that the nanocomposites are found to be paramagnetic at room temperature.     

Optical and electrical smart response of chemically stabilized graphene oxide

Graphene oxide (GO) was prepared using a modified Hammer’s technique and by utilizing a sonochemical approach. The paper deals with the synthesis and the characterization of GO besides the structural, morphological, optical and electrical properties of GO. Phase formation of the prepared sample was examined with powder X-ray diffraction (XRD), the typical surface morphology was carried out by utilizing Scanning electron microscopy (SEM) and the high resolution Transmission Electron Microscopy (HR-TEM). The different functional groups were recognized by utilizing FT-IR and Raman spectroscopy. The optical properties were studied utilizing optical absorption and photoluminescence (PL) spectra. At various frequencies and temperatures the dielectric properties of the GO, such as the dielectric constant, the dielectric loss, and AC conductivity were studied. Further, the electrical behaviour of GO was analysed using I-V and C-V characteristics. These novel findings shed focus on high yield electronic material GO, which can only be realized as the field moves forward and makes more significant advances in smart opto-electronic devices.     

Growth,characterizations, and the structural elucidation of diethyl-2-(3-oxoiso-1,3-dihydrobenzofuran-1-ylidene)malonate crystalline specimen for dielectric and electronic filters,thermal, optical,mechanical, and biomedical applications using conventional experimental and theoretical practices

Journal of Materials Science: Materials in Electronics - The single crystals of diethyl-2-(3-oxoiso-1,3-dihydrobenzofuran-1-ylidene) malonate (D23DYM) were grown successfully and efficiently by the...