Physical,structural and topographical aspects of Zn1−xCoxSe thin films

In the present study, Zn_1−xCo_xSe (0≤x≤0.275) thin films were synthesized via a chemical route and characterized through the physical, compositional, structural and morphological properties. The change in colour appearance from ash-grey to charcoal-black suggested integration of Co²⁺ into ZnSe host lattice. Similar conclusions on the colour appearance were drawn from colorimetric studies. The hydrophobic nature of the as-obtained sample surface was revealed in wettability measurements. Zn²⁺, Co²⁺ and Se^2- states of constituents in the thin films were found in the elemental analysis. Formation of ternary alloy was confirmed by shift in (111) X-ray diffraction peak. The surface topography was analysed by an atomic force microscopy (AFM). A variety of AFM parameters were determined to study the effect of Co²⁺ addition onto the surface topography. Magnetic mapping of the surface topography concluded the existence of magnetic domains of irregular sizes and shapes.     

A modified lateral flow immunoassay for the detection of trace aflatoxin M1 based on immunomagnetic nanobeads with different antibody concentrations

A modified lateral flow immunoassay (two-step assay) was developed to detect trace aflatoxin M1 (AFM1) in raw milk. In contrast to conventional LFIA, two kinds of immunomagnetic nanobeads (IMNBs) were used. One IMNB with high antibody concentration was used to capture AFM1 in the test sample, whereas the other IMNB with low antibody concentration was used to elucidate the results of the test. Critical factors, such as antibody concentration of IMNBs and size of IMNBs, were investigated. The two-step assay exhibited an ideal sensitivity to screen trace AFM1 in milk samples without extra sample pretreatment. The cutoff value of the naked eye was 0.02 μg/L and satisfied the European Union's maximum limit of AFM1 in raw milk, heat-treated milk, and milk used to manufacture milk-based products and even in baby foods. With the same antibody, sensitivity was enhanced approximately 25 and 50 times when compared with conventional IMNB-based LFIA and gold-based LFIA, respectively. Corresponding results of 13 raw milk samples were obtained between this two-step assay and referenced enzyme-linked immunosorbent assay.     

Preparation and properties of modified graphene oxide incorporated waterborne polyurethane acrylate

In this study, a new modifier (KPG) was prepared by modifying graphene oxide with γ‐glycidoxypropyl trimethoxysilane (KH560) and polydimethylsiloxane (PDMS). KPG was in turn added to aqueous urethane acrylate for the fabrication of waterborne polyurethane polyacrylate emulsion modified with KH560‐PDMS composite (KPG/WPUA). Textural characterizations of the KPG/WPUA coating were achieved via Fourier transform infrared, SEM, TGA and AFM techniques, which revealed that the KPG/WPUA film possessed a smooth surface. The synthesized KPG/WPUA films were tested for mechanical properties, hydrophobicity and acid/water corrosion performance which suggested their highly hydrophobic surface. KPG/WPUA with 0.1% KPG showed a contact angle of 118.35°, 30.35° higher than that of pristine WPUA. The KPG/WPUA film exhibited higher thermal stability, i.e. a 5% weight loss temperature of 305 °C, which was 30 °C higher than that of pristine WPUA film. The Young's modulus and elongation at break of the KPG/WPUA film were 34.1 MPa and 74.88% respectively, which were higher than that of WPUA film. Furthermore, KPG/WPUA films exhibited greater resistance (without obvious blistering and the white spotting phenomenon) to H₂O₂, HCl and water corrosion than pristine WPUA. The superior performance of KPG/WPUA films was attributed to the network chain structure formed upon the introduction of KPG into WPUA. The outstanding performance of KPG/WPUA films in terms of mechanical properties, thermal stability and high resistance to acidic and water corrosion makes them interesting alternative contenders for target applications. © 2019 Society of Chemical Industry     

The effect of surface roughness on the vibration behavior of AFM piezoelectric MC in the vicinity of sample surface in air environment based on MCS theory

Recent developments in the field of piezoelectric materials have led to the increasing use of piezoelectric materials in a variety of Atomic Force Microscopy (AFM). Utilizing piezoelectric layer as a sensor and actuator not only reduces the size of microscope but also enhances the quality of surface topography in Micro and Nano scales. In the current study, the effect of surface roughnesson the vibration behavior of AFM piezoelectric micro cantilever (MC) has been investigated in Micro and Nano scales according to the types of the surface roughness. Furthermore, the micro cantilever modelling has been schemed based on the Modified Couple Stress (MCS) theoryin order to model the vibration amplitude of AFM piezoelectric MC that precisely indicates the measured surface roughness. Besides, according to the various modelling of surface roughness, the effect of roughness radius on the minimum and maximum amplitude of Piezoelectric MC has been studied based on the geometry of roughness in air environment. In this environment, the effect of environmental forces including van der Waals, Capillary and contact forces on the vibration amplitude of MC forms the basis of surface topography which has, also, been studied in this article. Moreover, the present study intends to investigate the effect of surface roughness on the vibrating amplitude of MC in both the Tapping and Non-Contact Modes.     

Investigation of the effect of ZnO nanoparticles on the thermomechanical and microbial properties of hyperbranched polyurethane‐urea hybrid composites

Hybrid coatings of hyperbranched polyurethane‐urea (HBPUU) containing ZnO nanoparticles were prepared by mixing the hyperbranched polyurethane with the nanoparticles. The films were stored at room temperature and laboratory humidity conditions for one week to yield completely cured hybrid films. The ZnO nanoparticles were found to be well dispersed in the polymer up to 3 wt%. The structure–property relationship of various HBPUU–ZnO hybrid coatings was analysed using a Fourier transform infrared peak deconvolution technique with a Gaussian curve‐fitting procedure, while their viscoelastic, thermomechanical and surface morphology were studied using X‐ray diffraction, dynamic mechanical thermal analysis, thermogravimetric analysis, a universal testing machine, scanning electron microscopy, atomic force microscopy and contact angle instruments. The thermal stability and mechanical properties of the hybrid composite films improved with increasing ZnO content, which was believed to be due to thermal insulation in the presence of nanoparticles. Water contact angle data suggested that the hydrophobic character of the hybrid composites increased with increasing nanoparticle concentration. The antimicrobial property of the HBPUU–ZnO hybrid coatings was studied using the disc diffusion method. HBPUU–ZnO hybrid coatings showed good antimicrobial properties compared to HBPUU. Copyright © 2012 Society of Chemical Industry     

Investigation of a single pit/defect evolution during the corrosion process

The investigation of a single pit/defect evolution due to localized corrosion that is commonly observed in a wide range of aluminum alloys is reported. Electrochemical experiments, microscopy and computations were used to predict stresses around a single pit/defect. It was observed that the pit/defect profile changing its shape from slightly conical to more hemispherical shape with increasing corrosion time. Also, stress distribution and levels vary non-linearly around a single pit/defect. The results also indicate that the evolution of these pits/defects may lead to nucleation of a crack over time, which can be predicted from these stresses.     

Preparation of photo curable highly hydrophobic coatings using a modified castor oil derivative as a sol-gel component

Modification and use of natural products have gained a lot of interest in recent years due to their environmental friendliness and their availability from different sources. In this study castor oil based photo curable highly hydrophobic coatings were prepared and characterized. Castor oil (CO) was first modified with 3-isocyanato propyl triethoxy silane and then it was hydrolyzed prior to the coating preparation. The resulting precursor was mixed with norbornyl acrylate, hexane diol diacrylate and hydrophobic coatings were prepared with the aid of fluorinated and nonfluorinated alkoxy silane coupling agents. The addition of fluorine showed a significant impact on the properties of the coatings. As the fluorine content was increased in the formulations, flame retardancy and the contact angle values of the coatings increased. The highest amount of fluorine containing coating showed a contact angle of 119°. Then with the addition of nonfluorinated alkoxysilane compounds, a contact angle of 130° was reached. Also the effect of post-cure temperature on contact angle values was investigated.     

CuBr2‐induced charge screening on photoactive nanocolloidal polypyrrole:poly(styrene sulfonate) composite multilayer thin‐film counter electrodes for high‐efficiency dye‐sensitized solar cells

Nanocolloidal polypyrrole (PPy):poly(styrene sulfonate) (PSS) particles were synthesized by chemical oxidative polymerization using 15 wt% of PSS. The highly processable polymer composite (PPy:PSS) was spin‐coated at 4000 rpm on fluorine‐doped tin oxide glass and subsequently employed as a counter electrode (CE) for dye‐sensitized solar cells (DSCs). PPy:PSS multilayer (one, three, five) CEs were treated with CuBr₂ salt, which enhances the efficiency of the DSCs. Optical studies reveal that a bulkier counterion hinders interchain interactions of PPy which on salt treatment shows a moderate redshift in absorption maxima. Salt‐treated PPy:PSS films exhibit lower charge transfer resistance, higher surface roughness and better catalytic performance for the reduction of I₃^?, when compared with untreated films. The improved catalytic performance of salt‐treated PPy:PSS multilayer films is attributed to charge screening and conformational change of PPy, along with the removal of excess PSS. Under standard AM 1.5 sunlight illumination, salt treatment is shown to boost the efficiency of multilayer PPy:PSS composite film‐based DSCs, leading to enhanced power conversion efficiency of 6.18, 6.33 and 6.37% for one, three and five layers, respectively. These values are significantly higher (ca 50%) than those for corresponding devices without CuBr₂ salt treatment (3.48, 2.90 and 2.01%, respectively). © 2016 Society of Chemical Industry