H.A.M. Ali

Bio: H.A.M. Ali is an academic researcher from Ain Shams University. The author has contributed to research in topics: Dielectric & Thin film. The author has an hindex of 13, co-authored 37 publications receiving 417 citations.

Ac conductivity and dielectric properties of bulk tin phthalocyanine dichloride (SnPcCl2)

Abstract: The ac conductivity, σ ac ( ω ), has been measured for bulk tin phthalocyanine dichloride (SnPcCl 2 ) in the form of compressed pellet with evaporated ohmic Au electrodes in a temperature range 303–403 K. Ac conductivity, σ ac ( ω ), is found to vary as ω s in the frequency range 42 Hz−5×10 6 Hz. At low range of frequency, s s is found to be equal to ≈1.09 and is temperature independent. The dielectric constant, e 1 , and dialectic loss, e 2 , have been determined for bulk SnPcCl 2 . Both e 1 and e 2 decrease with the increase in frequency and increase with the increase in temperature. The Cole–Cole types have been used to determine some parameters such as; the macroscopic relaxation time ( τ o ), the molecular relaxation time ( τ ), the activation energy for relaxation ( E o ) and the distribution parameter ( α ). The temperature dependence of τ is expressed by a thermally activated process with the activation energy of 0.299 eV.

Optical and dispersion properties of thermally deposited phenol red thin films

Abstract: Thin films of phenol red are prepared using thermal evaporation technique. X-ray diffraction patterns of the powder form, as-deposited and annealed thin films are examined. The crystal structure and Miller indices of phenol red are deduced. Optical properties of phenol red thin films are investigated using spectrophotometric measurements for transmittance and reflectance as a function of wavelength in the range of 200–2500 nm. The optical constants, optical transitions, dispersion parameters and third-order nonlinear susceptibility are determined for phenol red thin films. The influence of the annealing on as-deposited films at 373 for 2 h is investigated for both of structural and optical properties.

Ionic conductivity by correlated barrier hopping in NH4I doped chitosan solid electrolyte

Abstract: Chitosan–NH 4 I and chitosan–NH 4 I–EC films have been prepared by solution cast technique. The sample containing 45 wt% ammonium iodide (NH 4 I) exhibited the highest room temperature conductivity of 3.7×10 −7 S cm −1 . The conductivity of the sample increased to 7.6×10 −6 S cm −1 when 40 wt% ethylene carbonate (EC) was added to the 55 wt% chitosan-45 wt% NH 4 I sample. The conductivity–temperature relationship is Arrhenian. From dielectric loss variation with frequency, the power law exponent was obtained. The temperature dependence of the power law exponent for chitosan–NH 4 I system follows the correlated barrier hopping (CBH) model while conduction mechanism of the plasticized system can be represented by the small polaron hopping (SPH) model.

One-Pot Conversion of Carbohydrates into Furan Derivatives via Furfural and 5-Hydroxylmethylfurfural as Intermediates

Abstract: Recently, there has been growing interest in the transformation of renewable biomass into value-added fuels and chemicals. The catalytic conversion of naturally abundant carbohydrates can generate two-important furan chemicals: 5-hydroxymethylfurfural (HMF) from C6 carbohydrates and furfural from C5 carbohydrates. Both HMF and furfural have received great interest as precursors in the synthesis of commodity chemicals and liquid fuels. In recent years, a trend has emerged to integrate sequential catalytic processes involving multistep reactions for the direct one-pot transformation of carbohydrates into the aimed fuels and chemicals. One-pot reactions have remarkably unique and environmentally friendly benefits, including the fact that isolation and purification of intermediate compounds can be avoided. Herein, the present article aims to review recent advances in the one-pot conversion of carbohydrates into furan derivatives via furfural and HMF as intermediates. Special attention will be paid to the catalytic systems, mechanistic insight, reaction pathways, and catalyst stability. It is expected that this review will guide researchers to develop effective catalytic systems for the one-pot transformation of carbohydrates into furan derivatives.

Synthesis of WO 3 and its gas sensing: a review

Abstract: As a typical n-type semiconductor, WO3 is considered to be the promising material to fabricate the gas sensor, which has a widespread utilization in the environment detecting and the safety monitoring. This review details the different structures of WO3 synthesized in recent studies, classifying them into five sections according to their dimensionality, then elucidates the research progress of the gas sensitivity towards H2, CO, H2S, NH3, NOx, O3 as well as some organic gases, based on which two models are proposed to explain the corresponding gas sensing mechanisms. Besides these, some unsolved problems and possible future directions are also discussed.

Effect of functional groups on dielectric, optical gas sensing properties of graphene oxide and reduced graphene oxide at room temperature

Abstract: Graphene oxide (GO) was synthesized from graphite through a chemical oxidation process and heat treated at 110 and 220 °C in a vacuum atmosphere. The partial reduction and sp3 to sp2 phase transition of GO was characterized by powder X-ray diffraction, Fourier-transform infrared, micro Raman, ultraviolet-visible-near infrared spectroscopy techniques. Dielectric properties of pristine GO and heat-treated GO were studied in the frequency range 102 to 106 Hz at 27 °C. Hydroxyl, carboxyl functional groups removed GO after 220 °C heat treatment, expressed higher electrical conductivity, dielectric constant and dielectric loss in the order of 10−2 S m−1, 103 and 105 respectively than the pristine GO (10−6 S m−1, 101 and 101). Pristine and heat-treated GO were coated on the partially cladding removed poly-methyl methacrylate optical fiber and used as fiber optic gas sensors. GO and heat treated GO coated fibers were responsive to detect ammonia, ethanol and methanol vapors from 0 to 500 ppm at 27 °C. Sensitivities of GO coated fiber optic sensor were calculated as −0.32, −0.26 and −0.20 counts per ppm for ammonia, ethanol and methanol vapors respectively. The effect of functional groups on dielectric and gas sensing properties of GO was investigated and reported.

Polymer-induced self-assembly of small organic molecules into ultralong microbelts with electronic conductivity.

Abstract: The principle of polymer-controlled crystallization of inorganic materials has been successfully transferred to functional aromatic organic dyes, in this instance 3,4,9,10-perylenetetracarboxylic acid potassium salt (PTCAPS), after its single-crystal structure was determined. The cationic double hydrophilic block copolymer poly(ethylene glycol)-block-branched-poly(ethyleneimine) (PEG-b-PEI) was used as the polymer additive to modify the crystallization of PTCAPS. Ultralong hierarchically structured PTCAPS microbelts with constant width and thickness of each individual belt have been fabricated. The belts are a mesocrystalline assembly of primary nanoparticles with high-energy anionic {001} faces stabilized by polymer complexation. Polarization microscopy, X-ray diffraction, optical absorption spectra, and fluorescence spectra indicate the favorable orientation of the 1D microbelts in the close-stacking direction and reveal a specific 1D superstructure fluorescence. Electrical conductivity measurements per...