فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 35 (زمستان 1399)

In this research, electrochemical sensor based on the polyzincon-modified glassy carbon electrode was fabricated to detect the dopamine. For this purpose, the glassy carbon electrode was modified by using cyclic voltammetry between -1 and 2.2 V and scan rate of 0.07 V/s for 6 cycles in a phosphate buffer (0.1 M) at pH 7 containing 0.1 mM zincon. Investigation on electrocatalytic activity and the electrochemical active surface showed that the surface area has increased for the modified electrode as compared to the glassy carbon electrode. The electrochemical impedance spectroscopy indicated the enhanced electron transfer between the electrode and redox probe for the polyzincon modified electrode. Based on the results, the anodic and cathodic peak currents increased with the scan rates and linear relation between peak current and scan rate and its square root indicated a dual character containing diffusion and adsorption-controlled processes on the surface. Detection of dopamine on surface of the modified electrode by differential pulse voltammetry method showed two linear range of 0.2-1 μM and the range of 1-100 μM with a limit of detection of 0.06 μM. Also, relative standard deviation for 5 replicates measurements in 20 μM dopamine solution was calculated as 4.5%. The designed sensor has advantages such as simplicity, low cost, high accuracy and sensitivity, and a suitable limit of detection that is able to compete with the latest electrodes in dopamine detection.

In this research, the sonophotocatalytic (SPC) technique was investigated as one of the advanced oxidation processes (AOPs) methods for the degradation and purification of toxic, resistant, and non-degradable rhodamine B (RhB) pollutant in the aqueous phase. For this purpose, the effect of simultaneous, and separate use of ultraviolet (UV) and ultrasonic (US) radiation for the chemical degradation of dye pollutant, has been investigated. First, ZnO/GO nanocomposite was synthesized and characterized via the sol-gel method. The morphology, structure, and size of the synthesized particles were determined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Absorption spectra of catalyst and dye contamination were investigated using a UV-Vis spectrophotometer. The sonophotocatalytic process showed higher degradation and quality compared to the separate photocatalytic and sonocatalytic methods. The ZnO/GO catalyst showed 98% degradation after UV and US radiation simultaneously, while photocatalytic and sonocatalytic methods showed 68 and 85% degradation, respectively, during the same period. According to the experimental results, the kinetics degradation of ZnO/GO nanocomposite was investigated and it well followed the first-order kinetic equation.

Environmental pollution is one of the issues facing scientists in recent years. With the advancement of various technologies, new achievements have been made in various fields, including industrial wastewater treatment. Nanomaterials have a key role in the identification and removal of pollutants. One of the best ways to control pollution is to use magnetic metal-organic framework (MMOF) composites, which is a combination of metal-organic framework and magnetic nanoparticles. These magnetic composites, as adsorbents, have both the properties of a metal organic framework and the property of magnetic separation, which makes these composites have high absorption capacity, easy separation, fast absorption with reusability. These properties has high potential for identification and removal of contaminants from the aqueous environment. In this review paper, several ways to synthesis MMOF composites based on their composition are introduced. Furthermore, the analysis of physical and chemical properties as well as the applications of these compounds for detection and removal of environmental pollutants have been discussed.

Investigation of rheological parameters on the protective performance of an epoxy coating through wet and dry cycles has been studied using creep-recovery modeling. For this purpose, an epoxy resin was cured with four types of hardeners (Polyamine-based, Polyamidoamine-based, Polyether polyamine-based, and Cycloaliphatic Polyamine-based hardener) to achieve various adhesion behaviors and viscoelastic properties. The storage modulus, viscoelastic creep-recovery, permeability, electrochemical parameters, and glass transition temperature were determined. Samples were exposed to humidity chamber and adhesion was measured at wet and dry conditions over time. After drying, adhesion loss and recovery were evaluated by the pull-off test. The electrochemical behavior of coatings was studied by electrochemical impedance spectroscopy (EIS). It was found that the higher the elastic module, the more the adhesion loss. Recovery of adhesion after wet and dry cycles correlated with the reversible element of creep and recovery data. After that, creep recovery data were modeled and for the first time, two rheological parameters (viscose ratio and the elastic ratio of the viscoelastic behavior) were defined for predicting adhesion durability. A coating with a higher viscose property in creep recovery behavior shows week adhesion recovery . It may referred to irreversible strain in a coating that cannot be recovered after the elimination of stress. Additionally, it was found that a sample with excellent initial protective properties, higher elastic modulus, and low initial water permeability may quickly fail because of the adhesion failure after wet cycles.

In this study, the influence of the ZnO seed layer on the growth of CdS nanostructures using chemical bath deposition method was studied. Applied ZnO seed layer led to change the surface morphology of deposited CdS on glass substrate from particle shape to nanosheet. The results indicated an improvement in the homogeneity and uniformity of the grown CdS nanostructures on ZnO seed layer, which can be due to the low lattice mismatch between ZnO and CdS structures. This change led to variation in crystal structure from cubic to hexagonal. The UV-Vis spectroscopy illustrated the higher absorption coefficient for CdS nanosheet related to CdS particle shape due to the high specific surface area. The calculated band gap of this sample by Tuac plot showed the value of 2.62 eV, which was increased compared to the cadmium sulfide with the bulk structure, which is due to the improved crystal quality of nanosheets. The results showed improved optoelectrical properties of optical detectors based on cadmium sulfide nanoparticles compared to the other samples.

Hypothesis: 

The basis of damping in polymers is the absorption of mechanical energy in the form of heat. When a polymer is exposed to vibration at the right temperature and frequency, the molecular vibrational energy is converted to heat and a dissipation peak appears within its glass transition region. Synthesis of core / shell latex particles with a specific morphology and using interpenetrating polymer networks in the core and shell sections is one of the best ways to expand the damping range. The aim of this study is to synthesize and investigate the dynamic-mechanical properties of interpenetrating polymer networks with core / shell morphology.

For this purpose, poly (styrene-methyl methacrylate-butyl acrylate) multilayer core/shell particles were fabricated by semi-continuous emulsion polymerization The formation of the structures was examined by FTIR . The arrangement of the layers was designed by varying the weight ratio of the monomers in each layer so that the glass transition temperature gradually decreased from the core to the shell and investigation of the particle size by DLS confirmed the uniform distribution in the nano scale. The amount of cross linker, reduction of reaction temperature and the weight ratio of the layers on the dynamic-mechanical properties were investigated.

The results showed that the three-layer core/shell particles at 75ºC with the optimal amount of crosslinking agent and weight ratio of 1:2:3 provide the widest effective damping range from -26ºC to 147ºC.

In this paper, a simple hydrothermal method is employed to synthesize BiSI/BiOI/CNT nanocomposite to improve the photocatalytic activity of BiSI/BiOI for the first time. The properties of the prepared samples were studied using X-ray diffraction analysis (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrometry (EDS), UV–vis diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), nitrogen adsorption-desorption isotherm (BET), and photoluminescence spectroscopy (PL). The loading amount of CNT had a significant influence on the photoactivity of the BiSI/BiOI/CNT composite. In this study, several BiSI/BiOI/CNT nanocomposite samples with various mass ratios of CNT were made-up for further investigation to scrutinize the influence of CNT content on the photocatalytic activity of the nanocomposite. Photocatalysis measurements revealed that 2% Wt of CNT possesses the highest photocatalytic activity in the visible light irradiation with 93.1% photodegradation of malachite green (MG) as a test dye in 240 min with the rate constant of 0.01 min-1. The enhanced photocatalytic performance can be due to the large surface area, excellent conductivity performance and high absorption ability in the visible light region. The synergistic effect of the factors mentioned above makes BiSI/BiOI/CNT nanocomposite a high-performance photocatalyst under visible light irradiation.