Building up Graphene-Based Conductive Polymer Composite Thin Films Using Reduced Graphene Oxide Prepared by γ

In this paper, reduced graphene oxide (RGO) was prepared by means of γ-ray irradiation of graphene oxide (GO) in a water/ethanol mix solution, and we investigated the influence of reaction parameters, including ethanol concentration, absorbed dose, and dose rate during the irradiation. Due to the good dispersibility of the RGO in the mix solution, we built up flexible and conductive composite films based on the RGO and polymeric matrix through facile vacuum filtration and polymer coating. The electrical and optical properties of the obtained composite films were tested, showing good electrical conductivity with visible transmittance but strong ultraviolet absorbance

Sparse target counting and localization in sensor networks based on compressive sensing

Abstract—In this paper, we propose a novel compressive sensing (CS) based approach for sparse target counting and positioning in wireless sensor networks. While this is not the first work on applying CS to count and localize targets, it is the first to rigorously justify the validity of the problem formulation. Moreover, we propose a novel greedy matching pursuit algorithm (GMP) that complements the well-known signal recovery algorithms in CS theory and prove that GMP can accurately recover a sparse signal with a high probability. We also propose a framework for counting and positioning targets from multiple categories, a novel problem that has never been addressed before. Finally, we perform a comprehensive set of simulations whose results demonstrate the superiority of our approach over the existing CS and non-CS based techniques

Efficient Removal Of U(VI) Ions from Aqueous Solutions by Tannic Acid/Graphene Oxide Composites

Tannic acid/graphene oxide (TA/GO) composites were prepared in the present research, and their properties and sorption performance were evaluated by corresponding characterization methods and bath sorption experiments, respectively. The applications of TA/GO to remove U(VI) from aqueous solution were investigated with the maximum adsorption capacity of 87.8 mg·g−1 at low pH (pH = 3.6 ± 0.03). The sorption of U(VI) ions on TA/GO followed the Langmuir model because of the complexation of oxygen-containing functional groups on the surface of TA/GO composites and uranium ions. TA/GO manifested excellent selective adsorption toward uranium ions with other metal ions (Cs+, Sr2+, Co2+). Furthermore, TA/GO as an effective adsorbent was reused to remove a large amount of U(VI) ions from aqueous solution. Therefore, TA/GO is an ideal material to remove highly toxic U(VI) ions from wastewater

An efficient anonymous batch authentication scheme based on priority and cooperation for VANETs

Abstract Vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2R) communications have raised a series of challenges due to data security and user privacy. Vehicular ad hoc networks (VANETs) have become the target of malicious attacks. Authentication has been widely adopted in VANETs to guarantee secure communications. However, existing authentication schemes have failed to meet stringent time requirements of VANETs leading to information loss. In this paper, we propose an efficient anonymous batch authentication (EABA) scheme aiming to reduce the message loss rate of vehicles and roadside units (RSUs). In the EABA scheme, we introduce a message classification algorithm and allow receivers to authenticate messages based on the classification result so that messages with high priority will be authenticated preferentially. In addition, we propose a cooperative authentication mechanism, where RSUs and vehicles share authenticated messages to reduce the workload on RSUs when the network is saturated. The proposed method is evaluated by extensive simulations, and the results demonstrate that the EABA scheme can reduce the message loss significantly and guarantee information security

Synthesis of Few-Layer Reduced Graphene Oxide for Lithium-Ion Battery Electrode Materials

We report here a rapid and cost-effective approach to synthesize few-layer reduced graphene oxide (FL-RGO) in graphene oxide solution using EDA as a reducing agent and a cross-linker, and where the resulting FL-RGO was characterized by means of AFM, TEM, XPS, UV–vis, and XRD spectroscopies. A mechanism for forming the FL-RGO via removal of epoxide and hydroxyl groups from GO and stitching of the GO sheets by EDA in a water solution was proposed. FL-RGO was also tested as the electrolyte for a Li⁺-ion battery and showed advantages with a 346 mAh g^–1 capacity at a charge/discharge current density of 1C even after 60 cycles, which is comparable to the theoretical capacity of the graphite (372 mAh g^–1)

Fabrication of PES-based membranes with a high and stable desalination performance for membrane distillation

Polyethersulfone (PES)-based membranes with a high and stable desalination performance for vacuum membrane distillation (VMD) were fabricated by spraying a dispersion containing hydrophobic-modified PES grafted copolymers onto porous PES membranes. The copolymer (PES-g-PFMA-C-8) with different degrees of grafting (DG) was synthesized by grafting 1H,1H,2H,2H-perfluorodecyl methacrylate (FMA-C-8) onto PES by simultaneous irradiation in a homogeneous system wherein the kinetics of the radiation-induced graft polymerization was studied. The copolymers, pristine PES membrane and fabricated PES-based membranes were also characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. After spraying, the hydrophobicity of the membrane increased and its maximum pore size reduced, which enhanced its desalination stability. During an intermittent 80 h VMD desalination operation, a flux of approximately 50.5 kg m(-2) h(-1) and a stable salt rejection of 99.98% were achieved when a 3.5 wt% NaCl solution was treated at 70 degrees C under vacuum of 92 kPa by the PES-based membrane using the copolymer with a DG of 20.3%, whereas salt leakage obviously occurred since the 52nd hour of operation when the pristine PES membrane was used. These results indicate that the modified PES membrane developed in this study is a promising candidate for VMD desalination due to its comparable flux.</p

Cross-Flow Catalysis Behavior of a PVDF/SiO2@Ag Nanoparticles Composite Membrane

A blend of Polyvinylidene Fluoride (PVDF) and SiO2 microspheres in N,N-Dimethylformamide (DMF) underwent phase inversion to form a PVDF/SiO2 membrane with SiO2 microspheres in the membrane’s pores. Subsequently, the SiO2 microspheres have been used as platforms for in site Ag nanoparticles (NPs) synthesis, forming a composite membrane. Benefitting from the full exposure of Ag NPs to the reactants, the composite membrane shows high catalytic reactivity when catalyzing the reduction of p-nitrophenol under a cross-flow. The catalytic reaction follows the first-order kinetics, and the reaction rate increases with an increase in the amount of Ag NPs in the membrane, the reaction temperature, and the operating pressure. What is more, highly purified products can be produced and separated from the reactants in a timely manner by using the composite membrane

RSC Adv.

Superhydrophobic porous composite membranes are successfully prepared by using poly(vinyl acetate) functionalized multi-walled carbon nanotubes and tested for water desalination under a direct contact membrane distillation (DCMD) method. The permeate flux of the composite membranes remains greater than 20 kg m (-2) h (-1) and the salt rejection greater than 99.5% when tested with 3.5% NaCl solution at 70 degrees C. The water contact angle of the composite membranes remains greater than 150 degrees after DCMD testing for 2 hours.Superhydrophobic porous composite membranes are successfully prepared by using poly(vinyl acetate) functionalized multi-walled carbon nanotubes and tested for water desalination under a direct contact membrane distillation (DCMD) method. The permeate flux of the composite membranes remains greater than 20 kg m (-2) h (-1) and the salt rejection greater than 99.5% when tested with 3.5% NaCl solution at 70 degrees C. The water contact angle of the composite membranes remains greater than 150 degrees after DCMD testing for 2 hours

A Study on the Degree of Amidoximation of Polyacrylonitrile Fibers and Its Effect on Their Capacity to Adsorb Uranyl Ions

Amidoximation of polyacrylonitrile (PAN) fibers was studied by reacting them with hydroxylamine. The chemical structure, mechanical intensity, and morphologies of PAN and amidoximated PAN (AO-PAN) fibers were evaluated by Fourier transform infrared spectroscopy, tensile tests, dynamic mechanical analysis, and scanning electron microscopy, respectively. A higher degree of amidoximation resulted in a higher conversion ratio (CR) of the nitrile group and a higher density of the amidoxime group, while also reducing the mechanical intensity of the fibers. During amidoximation, a hydrogel layer formed on the fiber surface by bonding with H₂O molecules, increasing the diameter of the AO-PAN fibers. The layer thickness increased as the CR of the AO-PAN fibers’ nitrile group was increased. The hydrogel layer decreased the adsorption capability by hindering the diffusion of uranyl ions to the interior of the AO-PAN fibers. Therefore, a CR of about 10.8% would provide an appropriate balance between the mechanical properties and the adsorption capability