Fe3O4-chitosan nanocomposite as a magnetic biosorbent for removal of nickel and cobalt heavy metals from polluted water.

Recently, natural polymers like chitosan have gained attention as promising adsorbents for water treatment. By combining chitosan with magnetic nanoparticles, their adsorption capabilities can be enhanced. In this study, chitosan-magnetite nanocomposite (CMNC) was synthesized via coprecipitation method to remove nickel and cobalt from aqueous solutions. The physicochemical properties of the synthesized CMNC were investigated by various techniques, including FESEM, TEM, XPS, FTIR, XRD, and VSM. The electron microscopy results confirmed the uniform dispersion of magnetite nanoparticles within CMNC nanocomposites, while VSM confirmed their significant magnetic properties. The adsorption experiments showed that at optimal conditions (pH = 6, contact time = 2 h, adsorbent dosage = 2 g/l), CMNC has high adsorption capacities of 30.03 mg/g for Ni2+ and 53.19 mg/g for Co2+. Furthermore, the adsorption data fitted best with the Langmuir isotherm, show that the active sites on CMNC are energetically homogenous. According to kinetic analysis, the experimental data were in good agreement with both pseudo-second-order and intra-particle diffusion models, which suggest that chemical sorption, along with mass transfer steps, influence the overall adsorption process. Finally, investigating the thermodynamic parameters (∆Gads, ∆Hads, ∆Sads) showed that the adsorption process on CMNC was endothermic and spontaneous, with stronger interactions observed between CMNC and Co2+ compared to Ni2+.

Optoelectronic Memory Capacitor Based on Manipulation of Ferroelectric Properties.

Here, we report on the fabrication of an optoelectronic memcapacitor (memory capacitor) by manipulation of ferroelectric properties through the ferroelectric-semiconductor interface based on a ZnO/PZT (Pb1.1(Zr0.52Ti0.48)O3) capacitor. A ZnO layer was deposited on PZT by the chemical vapor deposition method to achieve the memcapacitive effect. The capacitance-voltage and time-dependent capacitance characteristics of the Al/ZnO/PZT/Al memcapacitor were used as the main outcome measurement. In an asymmetric PZT structure with a ZnO layer, two stable states in the capacitance were obtained, which can be written by either optical or electrical pulses. In addition, the illuminated capacitive characters of the device showed a photovoltaic effect that is sensitive to wavelengths and can be used for nondestructive readout. Thus, this work proposes a low-cost structure solid-state memcapacitor exhibiting the promising potential for memory and computation applications with the ability to program and readout by electrical or optical signals.

Numerical investigation of the effect of substrate surface roughness on the performance of zigzag graphene nanoribbon field effect transistors symmetrically doped with BN.

The performance of field effect transistors comprised of a zigzag graphene nanoribbon that is symmetrically doped with boron nitride (BN) as a channel material, is numerically studied for the first time. The device merit for digital applications is investigated in terms of the on-, the off- and the on/off-current ratio. Due to the strong effect of the substrate roughness on the performance of graphene devices, three common substrate materials (SiO2, BN and mica) are examined. Rough surfaces are generated by means of a Gaussian auto-correlation function. Electronic transport simulations are performed in the framework of tight-binding Hamiltonian and non-equilibrium Green's function (NEGF) formalisms. The results show that with an appropriate selection of the substrate material, the proposed devices can meet the on/off-current ratio required for future digital electronics.