Current Nanoscience - Volume 14, Issue 3, 2018

Background: Delivery rates in cutaneous applications are limited by the skin barrier and also by the physical-chemical properties of the drug in the formulation. A lipophilic drug has more affinity, and can permeate the epidermis more easily than a hydrophilic drug. The potential use of nano-sized dispersions as distribution systems for hydrophilic drugs is being investigated. Objective: To analyze the literature with regard to the development of microemulsions (ME) for transdermal delivery of hydrophilic drugs, with a view to identifying strategies to increase the permeation of these drugs. Results: One hundred and eleven articles were potentially relevant to the combination of search criteria. After excluding duplicated articles, the abstracts of 83 articles were read. Of these, 73 did not meet the inclusion criteria. To complete the review process, the whole text of 10 articles was evaluated. Conclusion: The main factors that positively influenced the permeation of hydrophilic drugs were low hydrophilic-lipophilic balance (HLB) values of the surfactant; concentrations of about 40% of surfactants and 30% of aqueous phase for the water-in-oil (W/O) systems; the addition of permeation promoters to the systems; and the association of physical methods during the application of the ME. The results offered support for the development of new topical microemulsions for hydrophilic drug delivery.

Background: Nanowelding is an attractive bottom-up fabrication technique that allows the construction, connection, and repair of nanomaterials. The effects of contact interference, crystal orientation, and material type of nanoscale welded pairs are investigated in terms of atomic trajectories, strain distribution, and the stress-strain curve. Methods: The quasi-continuum (QC) method is applied to simulate nanowelding process. The QC method is a multi-scale combined molecular dynamics approach that mixes atomistic and continuum algorithms. Results: At a small contact interference of 0-1 nm, the ultimate stress of welded pairs is independent of the magnitude of contact interference. Regarding the effect of material type, the average ultimate stress for Ni-Ni welded pairs is the highest and that for Cu-Cu welded pairs is the lowest, regardless of the contact orientation mode. The elongation of Ni-Ni welded pairs increases with increasing contact interference. Conclusion: The crystal orientation of the contact plane and material type significantly determine the welding quality. Welding on the close-packed plane of both substrates leads to the highest ultimate stress. The ultimate stress for Ni-Ni welding pairs is the highest, and that for Cu- Cu welded pairs is the lowest.

Background: In this work, the effect of a uniform magnetic field (UMF) on the natural convection heat transfer of Cu-water nanofluid in a porous half-annulus cavity is studied by finite element method, considering heat generation. The effects of four parameters (magnetic field angle (γ), Hartmann number (Ha), nanoparticles volume fraction (φ) and Rayleigh number (Ra)) on the local and average Nusselt numbers of outer wall have been investigated. Methods: Numerical Finite Element Method (FEM) based on FlexPDE commercial code was used to solve the described problems and the validation was also performed by Finite Difference Method (FDM) in previous studies. Results: It was found that by applying external magnetic field with a certain angle with respect to the geometry, the maximum local heat Nusselt number could shift to one side of outer wall and the shift is dependent on the angle of the imposed magnetic field. Conclusion: Our results also confirm that increasing the Hartmann number decreases the Nusselt number due to Lorentz force resulting from the presence of stronger magnetic field which slows down the fluid motion and in turn leads to a decreased heat transfer.

Background: Bisphenol A (BPA) is an important intermediate in the industrial manufacturing of either polycarbonate plastic or epoxy resins. Bisphenol A and its chemical derivatives are endocrine-disrupting chemicals. BPA is a potent endocrine-disrupting compound (EDC) and its toxicity is widely reported in the literature. Therefore, it is important to develop fast identification methods for the monitoring of BPA in the environment. Methods: In this work, multi-walled carbon nanotubes decorated with cobalt ferrites (CoF) nanoparticles were synthesized by a controlled co-precipitation reaction. The modified multi-walled carbon nanotubes decorated with CoF nanoparticles were applied as a magnetic solid-phase microextraction (M-SPME) sorbent for the extraction of trace levels of BPA from water samples. In detection step, the CoF/MWCNTs modified screen-printed carbon electrodes (CoF/MWCNTs/SPCEs) (named CoFsensor) were used for the electrochemical detection of BPA. The CoF/MWCNTs modified SPCEs are found to give stable and reproducibility responses to BPA and the sensor exhibited good stability. Finally, the established combined procedure was successfully applied to determine BPA in water samples. Results: In this work, the magnetic CoFe2O4/MWCNTs nanoparticles were used as the electrode modifier and sample pre-concentrator. Firstly, some important electrochemical parameters of the modified electrodes were optimized and the calibration curve of the sensor showed a good linearity in the range of 0.5-50 μM and the detection limit was 0.2 μM. Secondly, the important parameters that affect the extraction performance were optimized. Under combined conditions, the calibration graph for the determination of bisphenol A was linear in the range of 0.02-1.5 μM (4.56-342 μg/L) and the detection limit was 0.01 μM. Finally, the combined system was successfully used for the detection of bisphenol A in tap water, drinking water, mineral water with recoveries of 93-102%. Conclusion: A new determination system combined CoF-sensor with M-CoF-SPME was developed for rapid, sensitive and selective detection of traces BPA in aqueous samples. The CoF/MWCNTs exhibited high sensitivity toward BPA with a maximum adsorption capacity of 67.7 mg/g. The nanoparticles were collected using a magnet and reused at least 10 times without substantial degradation in the activity. The analytical method combined miniaturised systems both in sample preparation and in detection stage, with the major advantage of avoiding costly and bulky or unmovable instrumentation. Besides, the M-CoF-SPME-CoF-sensor combination detection system provided many benefits such as cheapness, ease of operation, good sensitivity and repeatability. The determination method developed in current study provides a new option for the determination of BPA in water sample.

Background: The potential of applying TiO2-based materials has been ascertained in both wastewater and polluted air. Boron is proven to be an effective dopant to promote the activity of TiO2 in our previous work. The density of hollow material is little larger than water so that the hollow photocatalyst can suspend in wastewater under stirring or aeration. Methods: The graphical spheres were prepared from glucose using hydrothermal method. The hollow spherical x%B-TiO2 was synthesized through a sol-gel route, using tetrabutyl titanate and tributyl borate in the precursor. The materials were characterized by X-ray diffraction, scanning electron microscope, infrared spectrum, X-ray photoelectron spectroscopy, and N2 adsorption-desorption techniques. Photocatalytic degradation of RBR X-3B dye was studied to show the activity of the x%B-TiO2 materials. Results: Anatase TiO2 phase forms in all the x%B-TiO2 samples despite the difference in boron content. An absolute Ti⁴⁺ oxidation state exists in the x%B-TiO2, which is hardly affected by the doped boron. XPS analysis proves the formation of B-Ti-O structure in anatase TiO2 lattice. BET surface area increases with rising boron doping content in the hollow spherical x%B-TiO2 samples. Photocatalytic activity of TiO2 is enhanced after doping boron. The photocatalytic efficiency on RBR X- 3B degradation reaches the maximum value when n(B)/n(Ti) is 8%. After five photocatalytic cycles, decoloration efficiency on 8%B-TiO2 is as much as 80% of the initial value. Conclusion: A continuous expansion of TiO2 crystal happens with increasing boron content. The Ti4+ oxidation state of titanium in the hollow spherical material is not changed after doping boron. BET surface area of the hollow spherical x%B-TiO2 increases with rising boron doping content. The hollow spherical 8%B-TiO2 has satisfactory performs for recycling and lifetime.

Background: Adding nanoparticles to working fluids such as compressor oil can be a solution to ameliorate the efficiency of refrigeration systems. Using the mixture of nanoparticles and oil that is called nanolubricant (or nanofluid) can augment the heat removal in refrigeration systems, however, in the same time, the pumping power will be increased as the viscosity of nanolubricants is higher than that of usual oils. Therefore, the measurement of nanolubricant viscosity is a prerequisite to estimating the pumping power in refrigeration systems. Methods: Experiments section has been divided into three sections. First, the functionalization method of MWCNTs is presented. Then, the preparation of nanolubricants is explained. Finally, the viscosity measurement approach is explained. Results: To increase the dispersibility of MWCNTs in compressor oil, functionalization of MWCNTs was done through attaching −OH and −COOH groups with the aid of 65 wt% nitric acid solution. It was observed that with increasing the viscosity of the base oil, the stability of MWCNTs based nanofluids improves. Then, the viscosity of nanofluids has been measured at a temperature range of 15°C to 50°C. It was found that at 50°C and mass concentration of 0.1%, viscosity enhances between 40 and 90%, depends on the type of base compressor oil. Conclusion: Four correlations involving plane, paraboloid, Gaussian, and Lorentzian functions were suggested for the viscosity of nanolubricants. In the near future, it is expected from the results of this study that refrigeration systems will have included their Freon based refrigerants with nanoparticles.

Background: Demands of rechargeable energy storage devices such as batteries are increasing. Potassium is cheap and abundant contrary to Li. Prussian blue and analogues PBAs are promising cathodes materials for K- ion batteries, because of facile synthesis and low cost. However, PB and close analogues (Prussian green and Prussian white) suffer from low coulombic efficiency and low cyclability owing to structure deficiency. We present here a facile synthesis dip-dry method at elevated temperature of Prussian yellow film cathode for aqueous potassium battery with Zn anode. The device exhibits a high specific capacity, coulombic efficiency and long cycling life with satisfactory charge/discharge behavior. Method: Prussian yellow(PY) film was prepared as a thin film on ITO substrate by dip dry method from a solution mixture of Fe³⁺ (0.1M) and Fe(CN)^-6 (0.1M) at (80°C). Precipitation time was fifteen minutes. Films where characterization by FTIR, TGA, XRD, EDS, SEM, CV and EIS. Batteries composed of PY cathode and zinc metal anode were tested in 0.1M KCl electrolyte. Results: Battery gave OCV 1.9V with specific capacity of 142 mAh/g at rate of (~ 3C), with satisfactorily cycling ability up to 500 cycles & reversible charge/discharge behavior. Good crystal structure of PY film was demonstrated by several characterization methods e.g., FT-IR, TGA, XRD, EDS, SEM and electrochemical techniques. All showed good crystallinity quality of prepared PY films which demonstrate cathode qualities K cathode for K charge / discharge battery. Conclusion: Prussian yellow film, one of Prussian blue close analogues prepared in a simple and very facile nonelectrical method can be used as a robust cathode with highly reversible redox reactions that enable this material to be used as a cathode in battery of potassium aqueous electrolyte with Zinc anode. Battery has a significant cycle life (~500 cycle) and satisfactory capacity of 142mAhg^-1 at rate of (~3C) with efficiency retention of 82%.

Background: In QDs-based solar cell devices, the PbS QDs layer was mainly focused to optimize. The ZnO electron acceptor layer attracts less attention whereas it shows the key roles in extracting and transporting charge carriers in heterojunction. The utilization of 1-D ZnO structures has been demonstrated to be large interface areas and good carrier pathways for efficient carrier collection. However, the influences of the morphology of metal oxide nanostructures on the photovoltaic performance of QD-based solar cells have been few in-depth reports. Objective: In this work, ZnO NRs/PbS QD based solar cells were fabricated. The influences of the ZnO NRs array structures on characteristics of ZnO NRs/PbS QD based solar cells were investigated. Method: ZnO NRs/PbS QD based solar cells were fabricated via spin coating method. XRD, SEM, UV-VIS-NIR spectrophotometer, I-V and EQE measurement systems were utilized to investigate the fabricated samples. Results: We have found optimum combinations of the linked parameters of ZnO NRs, their length of (230 ± 5) nm and density of (1.50 ± 5)x10¹⁰ # of rods.cm^-2, that exhibit maximum efficiency of ∼2.5% for the ZnO NR/PbS QDs based solar cell. Conclusion: The influences the ZnO NRs structures on the solar cell characteristics, including the absorption, external quantum efficiency, and current density-voltage curves, were investigated. There seems to be an optimum between NR length and their density for resulting in maximum efficiency. This could be due the interplay of solar flux absorption and junction area controlled by these two parameters of ZnO NR morphology.

Background: In this study, computational Artificial Neural Network (ANN) model is applied for optimisation and evaluation of silver nanoparticles (AgNPs) size in the bionanocomposite matrix. The primary purpose of this study is used a feed-forward ANN model to create a connection between the output as the size of Ag–NPs, with four inputs variables, including AgNO3 concentration, the weight percentage of starch, Bentonite amount and Gallic acid concentration. Method: Silver nanoparticles were synthesised via biogenic green reduction method. The fast Levenberg– Marquardt (LM) backpropagation algorithm applied for the training of ANN model in this research. The optimised ANN is a multilayer perceptron (MLP) which is a kind of feed forward (4- 10-1) network has an input layer with 4 nodes, hidden layers with 10 neurones, and an output layer with 1 node found a fitness function. Results: The output results of developed computational ANN model were compared to its predictive values of the size of silver nanoparticles regarding two statistical parameters, the coefficient of determination (R²) and mean square error (MSE) of data set. It observed that ANN predicted values are close to the actual values and well fitted to the data. The mean square error(MSE) is 0.03, and a regression is about 1. Conclusion: AgNO3 concentration has the most likely factor affecting the size of silver nanoparticles (Ag–NPs) and this makes possible to develop a green reduction method for the preparation of silver nanoparticles. This study confirms that employing ANN method with LM feed forward (4-10-1) network is a useful tool with cost-effective for predicting the results of analysis and modelling of the chemical reactions.

Introduction: Graphene is flat monolayer of carbon atoms (one atom thick), covalently bonded to three other atoms in tightly packed two-dimensional (2D) hexagonal single layer stable crystalline honeycomb lattice structure. In this paper, In-situ amine functionalized exfoliated graphene with multiple layers (3-6) with low defect contents and average aspect ratio upto 10 microns (average X and Y dimensions) and thickness upto 2-3 nm (average Z-direction) which have been produced with the combined effort of chemical vapor deposition (CVD) and chemical graphite exfoliation method. Methods: This paper also focuses on the effect of the reinforcement of amine functionalized multiple graphene layers (AF-MGL) on the mechanical and visco-elastic properties of epoxy composites. AFMGL/ epoxy composites (AF-MGL/EpC) were prepared with graphene fractions ranging from 0.5 to 2.0 wt%. The four different samples were prepared using an amount of graphene as 0.0, 0.5, 1.5, and 2.0. A series of tensile three point bend tests were performed on the different AFMGL/epoxy composites. Optical and scanning electron microscopy (SEM) was used to examine the micro structural features and fractured surfaces of AF-MGL/EpC. Results: Increased graphene content results in improved tensile strength and the modulus of an epoxy matrix when compared with the pure epoxy matrix. The 1.5 wt% AF-MGL/EpC showed an increase in tensile strength and modulus by 50.2 and 52.8% respectively. However, a shrink was noticed beyond 1.5 wt.% samples of AF-MGL/EpC composite. Moreover, an improvement of 28.8% in the storage modulus was also recorded when compared with epoxy composites. Conclusion: The effect of the amine functional group on the mechanical and viscoelastic properties was also explored using molecular dynamics (MD) simulations and predicted results were then compared with experimental results.