Preparation, characterization and antibacterial properties of polycaprolactone/ZnO microcomposites

The micro scale zinc oxides in polycaprolactone microcomposites (PCL/ZnO-MCs) have prepared via solution casting method. The properties of the PCL/ZnO-MCs characterized by the Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric analysis (TGA), scanning electron microscope (SEM). According to the XRD patterns, the crystallinity of PCL was more pronounced after addition of ZnO microparticles (MPs), whereas the intensity of the bands was reduced by addition of ZnO-MPs. The FT-IR characteristic bands of PCL were found to shift to higher or lower wave number in PCL/ZnO-MCs due to formation of covalent bonding. TGA results exhibited that the thermal stability of the PCL/ZnO-MCs is improved with regard to that of pure PCL. The SEM images indicated that the interface adhesion between the ZnO-MPs and the PCL matrix can be enhanced by the surface modifications of ZnO-MPs by octadecylamine. TEM showed that the synthesis of PCL/ZnO-MCs was increased in interfacial interaction between ZnO and PCL matrix, which was obtained by modifying the surface of ZnO-MPs. The antibacterial activities of the PCL/ZnO-MCs films were examined against Salmonella choleraesuis as gramnegative bacterium and Bacillus Subtilis as a gram-positive bacterium by agar disc diffusion method. The antibacterial effects of the PCL/ZnO-MCs revealed that the antibacterial activity was enhanced with the enhancing of ZnO content

Preparation and characterization of poly (e-caprolactone)/TiO2 micro-composites

Based on XRD results, the study of crystallization of the PCL/TiO2MCs showed that TiO2MPs have significant influence on crystallization behaviour of poly (ε-caprolactone) in the PCL/TiO2MCs. The FTIR spectra indicated that the C=O of PCL shifted when TiO2MPs was added, indicating that some Van der Waals bonding between the alkyl groups of TiO2 and the ester group of PCL were formed. In comparison with the pure PCL, TGA data indicated an enhancement of thermal stability of PCL/TiO2MCs. SEM results confirmed the surface of TiO2MPs has sufficient compatibility with PCL through the link of the coupling agent between TiO2MPs and PCL, which can reduce the aggregation of TiO2MPs and improve dispersity. Transmission electron microscope (TEM) studies were performed to provide evidence for the micrometric dispersion of the TiO2MPs into PCL matrix on microscale

Thermal Diffusivity of Silver Metallic Nanoparticles in Clay Matrix

In this work, we have applied thermal lens (TL) technique to measure thermal diffusivity of clay suspensions containing metallic silver nanoparticles (Ag-NPs) prepared by chemical reduction method in different concentration. This study carried out with diode laser (wavelength 514 nm, power 80mW) as the excitation source and intensity stabilized He-Ne laser as a probe beam. The results show that thermal diffusivity of fluid increases when Ag-NPs concentrations increase

Photocatalytic removal of malachite green and brilliant blue dyes from its aqueous solution: a case study of factorial experimental design

In this present study, the investigation of the photocatalytic removal of malachite green and brilliant blue dyes from their aqueous solution using photocatalytic oxidation process was provided. The application of factorial experimental design for the analysis the results was the main objective in the present study. The photocatalytic removal of Malachite Green (MG) and Brilliant Blue (BB) dyes was carried out in aqueous solutions containing the dye and suspended of ZnO upon UV irradiation (high pressure mercury lamp Radium 125 W). The effect of different factors such as initial dye concentration, sample volume and treatment time was taken in account. All samples of MG and BB have been analysed at 617 and 620 nm, respectively. The linearity ranged between 5 and 50 mg/L for MG dye while it was ranged between 20 and 200 mg/L for BB dye. The linear regression, R2, was more than 0.995 for both dyes. The results revealed that factorial experimental design analysis has given a better indication to investigate the effects of factors. It was observed that the most of factors are significant for both dyes. Initial concentration and treatment time factors were the most significant factors for MG and BB dyes, respectively according to pareto chart

Photocatalytic degradation of malachite green dye by plant-mediated biosynthesized zinc oxide nanoparticles

Photocatalytic activity of ZnO-NPs was tested by degradation of Malachite Green dye under UV light irradiation. The ZnO-NPs were biosynthesized using Punica granatum (pomegranate) fruit peels extract as the stabilizing agent. Simple sol-gel method and calcination in different temperatures (400, 500, 600 and 700°C) were carried out to obtain pure ZnO-NPs with high photocatalytic properties. In the degradation studies, 20 mg ZnO-NPs were used to degrade Malachite Green dye of 10 ppm initial concentration for a total period of 50 minutes in a 100 ml reaction volume. Results obtained shown that ZnO-NPs calcined in 700°C had the highest removal efficiency at about 99% in 40 minutes. This proves that biosynthesized ZnO-NPs have a high potential to be used as a photocatalyst to degrade textile dyes in a short time for wastewater treatments

Phosphoric acid functionalized graphene oxide: a highly dispersible carbon-based nanocatalyst for the green synthesis of bio-active pyrazoles

Carbon-based catalysts are gained significant interest for improving a number of catalytic processes due to their unique set of benefits. However, a few of such catalysts are proper for synthesis of organic compounds in water. Therefore, there is a strong need for developing water-tolerant and dispersible catalysts. Here, we demonstrate a simple and efficient method for the preparation of highly dispersible phosphonic acid functionalized carbocatalyst. The applied functionalization method was flexible in controlling the functionalization level. The prepared nanocatalyst exhibited superior catalytic performance toward multicomponent synthesis of pyrano[2,3-c]pyrazole, with 80-90% yield within 15 min in water. Moreover, this water-tolerant solid acid. catalyst could be simply retrieved and after 6 successive cycles of reactions, the reaction time and yield still keeps within the same level

Green synthesis of zinc oxide-based nanomaterials for photocatalytic studies: A mini review

Due to rapid industrialization, wastewater pollution has become a serious concern that needs to be addressed effectively. Untreated contaminants abundantly discharged into the water bodies have been proven to negatively impact the environment as well as human health. For a long time, zinc oxide (ZnO) has been used to treat these environmental pollutions in a process called semiconductor photocatalysis. In the field of material science, nanosized ZnO synthesized using green route has been used by many researchers as they are usually eco-friendly and cost effective. Even though ZnO nanostructures act as an excellent photocatalyst, there are still a few drawbacks that can limit their efficiency. To overcome these problems, ZnO modifications can be done to produce ZnO-based nanomaterials. In this mini review, we present up-to-date research progress on green synthesized ZnO-based nanomaterials and discusses on the methods used to modify ZnO nanostructures to improve photocatalytic efficiency

Optical-fiber thermal-wave-cavity technique to study thermal properties of silver/clay nanofluids

Thermal properties enhancement of nanofluids have varied strongly with synthesis technique, particle size and type, concentration and agglomeration with time. This study explores the possibility of changing the thermal wave signal of Ag/clay nanofluids into a thermal diffusivity measurement at well dispersion or aggregation of nanoparticles in the base fluid. Optical-Fiber Thermal-Wave-Cavity (OF-TWC) technique was achieved by using a small amount of nanofluid (only 0.2 mL) between fiber optic tip and the Pyroelectric detector and the cavity-length scan was performed. We established the accuracy and precision of this technique by comparing the thermal diffusivity of distilled water to values reported in the literature. Assuming a linear Pyroelectric signal response, the results show that adding clay reduced the thermal diffusivity of water, while increasing the Ag concentration from 1 to 5 wt.% increased the thermal diffusivity of the Ag nanofluid from 1.524×10−3 to 1.789×10−3 cm2/s. However, in particular, nanoparticles show the tendency to form aggregates over time that correlated with the performance change of thermal properties of nanofluid. Our results confirm the high sensitivity of OF-TWC technique raises the potential to be applied to measuring the optical and thermal properties of nanofluids. Furthermore, this technique allows the extraction of information not obtained using other traditional techniques

Evaluation of parameters for subcritical water extraction of zingiber zerumbet using fractional factorial design

Zingiber zerumbet (Z. zerumbet) is recognized for decades for its usability as spice and condiment in food flavoring as well as having high medicinal properties. Up to date, there are limited literature on evaluation of the effects of multiple variables in details especially in pilot-scale subcritical water extraction (SWE) of Z. zerumbet. The aim for this study is to implement the fractional factorial design with five variables which are temperature (100-170°C), time (10-40 minutes), pressure (10-20 bar), particle size (0.89-3.56 mm) and solvent to solid ratio (20-40 ml/g) in SWE of Z. zerumbet. Analysis of variance for all responses stated that temperature, time, particle size and solvent to solid ratio are significant variables. Temperature is the most significant factor for zerumbone concentration and antioxidant activity with a p-value of <0.0001 and 0.0002, respectively. The solvent to solid ratio was the most significant factor for the yield of extraction with a p-value of 0.0002. Time and particle size were significant towards all responses, however pressure was not significant on zerumbone concentration and yield. Thus, the fractional factorial design could give a broad overview in selecting the significant variables for further optimization in SWE from the findings