Al2O3 Colloidal Nanocrystals with Strong UV Emission

A facile sol–gel procedure has been developed for the synthesis of colloidal alumina nanocrystals. For the first time, optical characterization procedures were employed to study the quantum confinement effects in optical properties of the prepared Al₂O₃ sol. Accordingly, the hyperbolic band model was used to determine the optical band gap of colloidal alumina nanocrystals. X‐Ray diffraction pattern was used to study the crystallographic phase of the dried gel. Morphological characterization was performed using scanning electron microscopy (SEM). Inductively Coupled Plasma (ICP) emission spectroscopy was used to determination purity of the Al₂O₃ powder. High‐resolution TEM showed that the diameter of colloidal nanocrystals is about 10 nm. Photoluminescence spectroscopy demonstrated that quantum yields for colloidal nanocrystals are 68% with 300 nm excitation wavelength. The experimental observations confirm that highly stable alumina sol with strong UV emission was synthesized. The mentioned optical properties have not been reported before.     

Plasticized poly(vinyl chloride) composites: Influence of different nanofillers as antimigration agents

In this study, plasticized poly(vinyl chloride) (PVC) composites with different nanofillers, including single‐walled carbon nanotubes (SWCNTs), organoclay, TiO₂, and ZnO nanoparticles, were prepared, and their effects on plasticizer migration were investigated. Scanning electron micrographs revealed the dispersion quality of the nanofillers in the polymer matrix. It had a significant influence on the performance of the nanofillers in the process of plasticizer migration. Migration and exudation tests showed that the nanofillers could efficiently hinder plasticizer migration. On the basis of these results, we concluded that carbon nanotubes were the best antimigration agent in the plasticized system. This was ascribed to the high aspect ratio of the SWCNTs and the good interactions between them and the plasticizer. Also, TiO₂ nanoparticles showed a better performance compared to the ZnO nanoparticles. This was due to the more homogeneous dispersion of the TiO₂ in the polymer matrix and the higher surface area of the particles. The differential scanning calorimetry thermograms were in good agreement with the migration tests. The lowest change in the glass‐transition temperature was observed for the composite filled with SWCNTs. This indicated that a lower amount of the plasticizer migrated from PVC. The thermogravimetric analysis curves showed that the incorporation of the nanofillers improved the thermal stability of the PVC. The results could be useful for determining the efficiency of plasticized PVC in applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42559.     

Evaluation of antimicrobial and dyeing properties of walnut (Juglans regia L.) green husk extract for cosmetics

Walnut green husk is one of the main waste products from walnut and could be used as a source of natural dyeing compounds such as juglone. The present study was conducted to evaluate the effective use of walnut green husk extract as a natural hair dye. Dyeing properties, fastness and antimicrobial behaviours of dyed hair and also a skin irritation test for natural hair dye on rat skin were examined. When the extract was mixed with ascorbic acid as a developer, ferrous sulphate as a mordant, and Aloe vera extract used as a secondary mordant and also a cosmetic ingredient, the reaction resulted in a dark‐brown colour on hair samples. The dyed hair exhibited appropriate colour strength having excellent morphology for a hair surface coated with dye molecules. In addition, the dyed hair possessed good resistance to washing and daylight fastness, without any irritant properties as shown in a rat model, although high concentrations of iron‐based mordant may be problematic for long‐term usage. This paper also suggests the use of natural mordants such as lactic and oxalic acids to avoid any probable risks. Walnut green husk extract was an appropriate natural hair dyeing agent in practice and showed maximum antimicrobial activity compared with semi‐synthetic and commercial hair dyes. The results demonstrated that walnut green husk can be used as an economical, valuable, eco‐friendly and safe source of dyeing and antimicrobial agents for cosmetic products.     

Removal of methylene blue from aqueous solution by electrophoretically deposited titania‐halloysite nanotubes coatings

Two‐component suspensions of titania and halloysite nanotubes (HNTs) were prepared in ethanol with 0.5 g/L (optimum concentration) of polyethyleneimine (PEI) and different wt% of HNTs. Kinetics of Electrophoretic deposition (EPD) decreased with increasing the HNTs content in suspensions due to their less mobility compared with titania particles. HNTs reinforced the microstructure of coatings and reduced or completely prevented from cracking during drying and heat‐treatment steps. Removal of methylene blue (MB) via adsorption by HNTs coatings was faster than its photocatalytic degradation by titania coating. Dispersion of HNTs (up to ≈30 wt%) in the matrix of titania resulted in the synergistic catalytic effect in MB removal. The synergistic effect was because of the shorter traveling distance of MB molecules adsorbed on HNTs toward the photocatalytic active site of titania particles in composite coatings. However, the synergistic effect was destroyed with increasing the HNTs content in coating. Difference between the amount of MB removed by titania and composite coatings increased at longer times (≥60 minutes). Mass transfer of MB adsorbed on HNTs toward the photocatalytic active sites of adjacent titania particles can compensate the decline in the mass transfer from solution at longer times.     

Mangrove-mediated synthesis of silver nanoparticles using native Avicennia marina plant extract from southern Iran

The development of eco-friendly and nontoxic processes for the synthesis of nanoparticles is one of the most important discussed issues in nanotechnology science. This study reports the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of leaf, stem, and root of Avicennia marina, the native and dominant mangrove plant in southern Iran. Among the different plant parts, the extract of leaves yielded the maximum synthesis of AgNPs. Synthesized AgNPs were investigated using UV–visible spectrophotometry, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and Fourier transform infrared (FTIR) spectroscopy. Absorption spectrum in 420?nm confirmed the synthesis of AgNPs. TEM images revealed that the synthesized AgNPs had the same spherical morphology with a size range between 0 and 75?nm. The distribution size histogram indicated that the most frequent particles were in the range of 10–15?nm and the mean size of nanoparticles was 17.30?nm. The results of SEM image showed nanoparticles with a size range between 15 and 43?nm. XRD pattern indicated the crystalline nature of synthesized nanoparticles. EDS results confirmed the presence of elements like silver, carbon, chlorine, nitrogen, and oxygen in the nanoparticles produced from leaf extract. Silver had the maximum percentage of formation, 51.6%. FTIR indicated the presence of different functional groups such as amines, alcohol, alkanes, phenol, alkyl halides, and aromatic loops in the synthesis process. Green biosynthesis of AgNPs using aqueous extract of native A. marina appears rapid, reliable, nontoxic, and eco-friendly.     

A comprehensive study on wastewater treatment using photo-impinging streams reactor: Continuous treatment

The degradation of phenol was investigated in a continuous flow impinging streams system. In the first step, statistical experimental designs were used to optimize the process of phenol degradation in a photo-impinging streams reactor. The more important factors affecting phenol degradation (p<0.05) were screened by a two-level Plackett-Burman design. Four of the latter parameters, namely phenol concentration, catalyst loading, pH and slurry flow rate, were selected for final process optimization, applying central composite design (CCD). The predicted data showed that the maximum removal efficiency of phenol (99%) could be obtained under the optimum operating conditions (phenol concentration=50 mg l ^?1, catalyst loading=2.1 g l ^?1, pH 6.2 and slurry flow rate=550ml min^?1). These predicted values were then verified by certain validating experiments. A good correlation was observed between the predicted data and those determined by the experimental study. This may confirm the validity of the statistical optimum strategy. Finally, continuous degradation of phenol was performed, and the results indicated a higher efficiency and an increased performance capability of the present reactor in comparison with the conventional processes.