Hany Hamdy

Nanostructured ZnO thin films for self-cleaning applications

Controlling the properties of nanostructured zinc oxide (ZnO) is an interesting way to broaden its multifunctionality. ZnO nanostructured films were grown on glass substrates under different conditions by a simple two-step wet chemical method. A low-cost successive ionic layer adsorption and reaction (SILAR) method was used to grow ZnO seed layers at 80 °C. Then, different hierarchical based ZnO nanostructured thin films were deposited onto the ZnO seed layers by chemical bath deposition (CBD). The influence of deposition time (tD) and pH on the surface morphology, wettability behavior, structural and optical properties of the ZnO nanostructured films were systematically investigated. The structural, morphological, optical and wetting properties were studied by X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), UV-Vis spectrophotometer, and water contact angle (WCA) measurement, respectively. The surface morphology revealed a complex and orientated hierarchical based ZnO nanostructured films with diverse shapes from hexagonal nanorods to hexagonal nanoplates and even much more complex plates/rods and flower-like shapes by changing deposition time and pH of the precursor. XRD results confirm the synthesis of nanostructured ZnO of the hexagonal structure with a preferential orientation along the (002) lattice plane. The average crystallite size, D, is altered between 41.41 to 68.43 nm dependent on the morphology of the ZnO film and pH of the precursor. At pH 6.5, the films are hydrophilic for 10 h ≤ tD ≤ 6 h and hydrophobic for 6 h < tD < 10 h. The wetting properties of the films were enhanced by increasing or decreasing pH around 6.5. Morphology and thickness of the ZnO nanostructure could efficiently control the transmittance, absorbance, optical band gap, and the extinction coefficient of the films. The optical band gap is blue shifted from 2.45 to 3.62 eV@pH 6.5 as the deposition time increased from 2 to 8 h and blue shifted from 2.72 to 3.62 eV@8 h as the pH value increased from 5.5 to 6.5. The existence of stable hydrophobic zinc oxide nanostructured films at room temperature at a large-scale and with band gaps around 3.62 eV supports their use in self-cleaning and gas sensing applications.

Tunability and Sensing Properties of Plasmonic/1D Photonic Crystal

Gold/one-dimensional photonic crystal (Au/1D-PC) is fabricated and applied for sensitive sensing of glucose and different chemical molecules of various refractive indices. The Au layer thickness is optimized to produce surface plasmon resonance (SPR) at the right edge of the photonic band gap (PBG). As the Au deposition time increased to 60 sec, the PBG width is increased from 46 to 86 nm in correlation with the behavior of the SPR. The selectivity of the optimized Au/1D-PC sensor is tested upon the increase of the environmental refractive index of the detected molecules. The resonance wavelength and the PBG edges increased linearly and the transmitted intensity increased nonlinearly as the environment refractive index increased. The SPR splits to two modes during the detection of chloroform molecules based on the localized capacitive coupling of Au particles. Also, this structure shows high sensitivity at different glucose concentrations. The PBG and SPR are shifted to longer wavelengths, and PBG width is decreased linearly with a rate of 16.04 Å/(μg/mm3) as the glucose concentration increased. The proposed structure merits; operation at room temperature, compact size, and easy fabrication; suggest that the proposed structure can be efficiently used for the biomedical and chemical application.

Self- Agglomeration of Tin Nanoparticle Array on Porous Anodic Alumina Membranes: Fabrication and Characterization

In this paper, a facile method to fabricate two-dimensional (2D) Sn nanoparticles is demonstrated. Sn nanoparticles are deposited on porous anodic alumina membrane (PAA) by using ther- mal vapor deposition (TVD) technique. A set of PAA membranes fabricated under the same conditions was coated with Sn for different periods of time. SEM images showed the formation of hexagonal nanoar- rays of Sn around each nanopore following a selective agglomeration growth mechanism on the active dots of the PAA surface. As the deposition time increased from 1 to 3 min, the agglomerated particles height increased from 20 to 75 nm. Moreover, Sn was thermally deposited for 2 min onto PAA substrates of different pore diameters. As the pore diameter increases, the formed Sn particles diameter decreases and their density distribution around each pore is improved, which may be attributed to the dimensions of the active area of the PAA surface. According to reflection spectra, it was found that the oscillation strength of the samples increased as the deposition time increased to 2 min. For the time greater than 2 min, the oscillation strength decreased due to the scattering of light, particularly in the short wavelength region, that caused by the increase of sample roughness.

Quercetin and low level laser therapy promote wound healing process in diabetic rats via structural reorganization and modulatory effects on inflammation and oxidative stress

This study aimed to evaluate the effect of quercetin and the photo-stimulatory effect of low energy 632.8 nm laser irradiation on excisional wound healing in non-diabetic and diabetic rats. Streptozotocin (45 mg/kg body weight) was intraperitoneally applied for diabetes induction. A full-thickness skin wound (2 × 2 cm2) was aseptically created with a scalpel in non-diabetic and diabetic rats on the shaved back of the animals. The wounded non-diabetic and diabetic rats were treated every other day with quercetin by oral gavage at dose 25 mg/kg body weight and/or with low level laser therapy (LLLT) for 14 days. The wound closure percent calculated during the course of the experiment at days 1, 7 and 14 was remarkably increased as a result of treatment of non-diabetic and diabetic wounded rats with quercetin and LLLT; the treatment with both was the most potent. The elevated blood glucose and the lowered serum insulin levels were significantly improved in diabetic wounded rats treated with quercetin and LLLT as compared to the diabetic wounded control. The histological findings indicated that the wounded skin showed a marked increase in collagen fibers which become well oriented in sub-epidermal tissue, intact epidermis and presence of hyperplasia covering well-developed granulation tissue in the wounded rats treated with quercetin and LLLT as compared to the corresponding wounded control. The elevated levels of serum pro-inflammatory cytokines, IL-1β and TNF-α, as well as PGE-2 and LTB-4 were decreased in non-diabetic and diabetic wounded rats with quercetin and LLLT while the lowered level of serum anti-inflammatory cytokine, IL-10, was increased. The augmented oxidative stress represented by increased serum lipid peroxides level was decreased and the serum level of non-enzymatic anti-oxidant glutathione was increased as a result of treatment with quercetin and LLLT. Thus, it can be suggested that the improvements in glycemic state, cytokines involved in inflammation and antioxidant defense system as well as structural reorganization after treatment with quercetin and LLLT may play pivotal roles in promoting the wound healing process. The study also concluded that the treatment with quercetin in association with LLLT was better in improving wound healing in non-diabetic and diabetic rats than the use of either of each.

Studying the variation of eddy diffusivity on the behavior of advection-diffusion equation

Abstract In this work, the advection-diffusion equation was solved in two dimensions to calculate the normalized crosswind integrated concentration by Laplace technique. Considering that the wind speed is constant and we have two models of the vertical eddy diffusivity, one depends on downwind distance and the other model depends on vertical distance. A comparison between our proposed two models, Gaussian, previous work and observed data measured at Copenhagen, Denmark, have been carried out. One finds that there is a good agreement between predicted (2) model and the observed concentrations than predicted (1), Gaussian and previous work. From the statistical technique, one finds that all models are inside a factor of two with observed data. Regarding to Normalized mean square error (NMSE) and Fraction Bais (FB), proposed model (2) is performance well with observed data than the predicted (1), Gaussian and previous work in unstable condition.

Theoretical Solution of the Diffusion Equation in Unstable Case

The diffusion equation is solved in two dimensions to obtain the concentration by using separation of variables under the variation of eddy diffusivity which depend on the vertical height in unstable case. Comparing between the predicted and the observed concentrations data of Sulfur hexafluoride (SF6) taken on the Copenhagen in Denmark is done. The statistical method is used to know the best model. One finds that there is agreement between the present, Laplace and separation predicted normalized crosswind integrated concentrations with the observed normalized crosswind integrated concentrations than the predicted Gaussian model.

Fabrication and characterization of nanostructured Mg-doped CdS/AAO nanoporous membrane for sensing applications

In this study, Mg-doped CdS nanostructure was deposited onto anodic aluminum oxide (AAO) membrane substrate using sol-gel spin coating method. The AAO membrane was prepared by a two-step anodization process combined with pore widening process. The morphology, chemical composition, and structure of the spin- coated CdS nanostructure have been studied. The morphology of the fabricated AAO membrane and the deposited Mg-doped CdS nanostructure was investigated using scanning electron microscopy (SEM). The SEM of AAO illustrates a typical hexagonal and smooth nanoporous alumina membrane with interpore distance of ~ 100 nm, the pore diameter of ~ 60 nm. SEM of Mgdoped CdS shows porous nanostructured film of CdS nanoparticles. This film well adherents and covers the AAO substrate. The energy dispersive X-ray (EDX) pattern exhibits the signals of Al, O from AAO membrane and Mg, Cd, and S from the deposited CdS. This indicates the high purity of the fabricated membrane and the deposited Mg-doped CdS nanostructure. Using X-ray diffraction (XRD) pattern, Scherrer equation was used to calculate the average crystallite size. Additionally, the texture coefficients and density of dislocations were calculated. The fabricated CdS/AAO was applied to detect glucose of different concentrations. The proposed method has some advantages such as simple technology, low cost of processing, and high throughput. All of these factors facilitate the use of the prepared films in sensing applications.

Synthesis of nanoporous chromium film by DC electrodeposition on aluminum substrate

Porous Anodic Alumina (PAA) is widely employed as a template for fabrication of nanostructures due to its ability to generate self-organized, well-ordered pore structures. A new technique has been developed to deposit porous Chromium (Cr) film on Al substrate by DC electrodeposition. The chemical composition and morphological characteristics of fabricated PAA membrane and Cr film were investigated by scanning electron microscopy (SEM), and energy-dispersive x-ray spectroscopy (EDX). In addition, the growth mechanism of the fabricated nanoporous Cr film was discussed. Keywords: Nanoporous Cr film; PAA membrane; DC electrochemical deposition; Growth mechanism

Morphological Studies of ZnO Nanostructures Deposited on Nanoporous Anodic Alumina Membrane by Rapid Dip Coating Technique

Inthiswork,differentmorphologiesofzincoxide(ZnO)nanostructureshavebeenfabricatedbya simpleandrapid dip coating method.Inthis method ZnO nanostructuresare deposited from sol-gel of zinc acetateusing dip coating onto Porous Anodic Alumina Membrane (PAAM).Afterthermalannealinginoxygenat600°Cfor30 min,the ZnO nanoparticles are uniformly agglomerated into, almost, 1D nanorods array. When the starting precursor is zinc nitrate and the annealing was carried out for 10 h at the same conditions, the ZnO nanoparticles are uniformly agglomerated into, almost, nanoseeds (nanocolloidal particles).