Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nanoscale Research Letters  

The evolution of zinc oxide nanostructures grown on graphene by alcohol-assisted ultrasonic spray pyrolysis was investigated. The evolution of structures is strongly depended on pyrolysis parameters, i.e., precursor molarity, precursor flow rate, precursor injection/deposition time, and substrate temperature. Field-effect scanning electron microscope analysis, energy dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy were used to investigate the properties of the synthesized nanostructures and to provide evidence for the structural changes according to the changes in the pyrolysis parameters. The optimum parameters to achieve maximum density and well-defined hexagonally shaped nanorods were a precursor molarity of 0.2 M, an injection flow rate of 6 ml/min, an injection time of 10 min, and a substrate temperature of 250–355 °C. Based on the experimental results, the response surface methodology (RSM) was used to model and optimize the independent pyrolysis parameters using the Box-Behnken design. Here, the responses, i.e., the nanostructure density, size, and shape factor, are evaluated. All of the computations were performed using the Design-Expert software package. Analysis of variance (ANOVA) was used to evaluate the results of the model and to determine the significant values for the independent pyrolysis parameters. The evolution of zinc oxide (ZnO) structures are well explained by the developed modelling which confirms that RSM is a reliable tool for the modelling and optimization of the pyrolysis parameters and prediction of nanostructure sizes and shapes.

DOI： 10.1186/s11671-015-1163-1

Open Access

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Radiation Physics and Chemistry  

Modeling and optimization aspects of radiation induced grafting (RIG) of 4-vinylpyridine (4-VP) onto partially fluorinated polymers such as poly(ethylene-. co-tetrafluoroethene) (ETFE) and poly(vinylidene fluoride) (PVDF) films were comparatively investigated using response surface method (RSM). The effects of independent parameters: absorbed dose, monomer concentration, grafting time and reaction temperature on the response, grafting yield (GY) were correlated through two quadratic models. The results of this work confirm that RSM is a reliable tool not only for optimization of the reaction parameters and prediction of GY in RIG processes, but also for the reduction of the number of the experiments, monomer consumption and absorbed dose leading to an improvement of the overall reaction cost. © 2013 Elsevier Ltd.

DOI： 10.1016/j.radphyschem.2013.05.049

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Membrane Science  

Optimization of the reaction parameters affecting phosphoric acid (PA) doping behavior of poly(1-vinylimidazole), P(VIm), grafted poly(ethylene-co-tetrafluoroethylene) (ETFE) proton conducting membrane precursors obtained by radiation induced grafting was studied using the Taguchi method. The reaction parameters such as degree of grafting (G%) in the precursors, PA concentration, temperature and doping time were selected as independent parameters while doping level was the response. The optimum parameters for achieving the maximum doping level (7.45mmolrepeat polymer unit^-1) were: G% of 54%, PA concentration of 60%, temperature of 100°C and reaction time of 5 days. The kinetics of the acid doping reaction was also studied and the doping rate was found to be a function of reaction parameters and followed a first order reaction. The PA doping was verified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis of the membranes. The proton conductivity and thermal stability of the membranes were also evaluated. It can be concluded that the Taguchi method provides an effective tool for prediction of acid doping level and optimization of reaction parameters. The kinetics of acid doping is also suggested to be a diffusion-driven reaction following a multi-layers adsorption model. © 2013 Elsevier B.V.

DOI： 10.1016/j.memsci.2013.05.053

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：High Performance Polymers  

Composite membrane containing phosphoric acid (PA) for possible use in a fuel cell was prepared by radiation-induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetrafluoroethylene) (ETFE) films followed by protonation with PA doping. The preparation procedure involved three steps: (i) irradiation of ETFE films by an electron beam, (ii) grafting of 1-VIm onto the irradiated films under selected conditions and (iii) doping the grafted film with PA. The membrane composition, thermal properties and thermal stability were evaluated using Fourier-transformed infrared spectroscopy, thermogravimetric analysis and differential scanning calorimetry, respectively. The obtained membrane was found to have a degree of grafting of 54% and 6.6 mmol PA per poly-VIm repeating unit with ionic conductivity of 140 mS cm-1 at 120 C and ∼20% relative humidity. The overall results suggest that the membrane has a promising combination of physicochemical properties appealing for possible application in polymer electrolyte membrane fuel cell above 100 C. © The Author(s) 2012.

DOI： 10.1177/0954008312460065

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Journal of Applied Polymer Science  

The traditional method for obtaining best combination of reaction parameters for graft copolymerization of 4-vinylpyridine onto poly(vinylidene fluoride) films was modified using Box-Behnken factorial design available in the response surface method (RSM). A computer-assisted statistical simulator was used to obtain the optimum absorbed dose, monomer concentration, grafting time and reaction temperature to achieve the highest degree of grafting (G%) based a quadratic model. The validity of the developed model was confirmed by experimental data, which only deviated by a 2% from the predicted value of G% confirming the effectiveness of RSM in optimization of the reaction parameters in the present grafting system. A comparison was also made between the obtained model and that of 1-vinylimidazole/poly(ethylene-co-tetrafluoroethylene) grafting system. The chemical structure, morphology and thermal stability of the obtained graft copolymers was investigated by means of Fourier transform infrared, filed emission scanning electron microscope, and thermogravimetric analysis, respectively. © 2012 Wiley Periodicals, Inc.

DOI： 10.1002/app.37558

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Desalination  

Recently, the significant role of water management in affecting the performance and durability of proton exchange membrane fuel cell (PEMFC) has been subjective to an intensive research to understand water transport phenomena which is marked by two processes: water adsorption and water diffusion. Various mathematical models have been developed to address both processes on a different basis. This article briefly reviews various water transport models in a comparative manner to have a better understanding on the role of water hydration with respect to membrane structure and transport mechanism, in affecting the proton transport in the membranes. A discussion on the validity and reliability of the models for describing the water management is also presented. The limitations that are required to be overcome to design new materials meeting the new trends of membranes development for fuel cell are also highlighted. © 2011 Elsevier B.V.

DOI： 10.1016/j.desal.2011.06.054

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Radiation Physics and Chemistry  

Radiation induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) was investigated. The grafting parameters such as absorbed dose, monomer concentration, grafting time and temperature were optimized using response surface method (RSM). The Box-Behnken module available in the design expert software was used to investigate the effect of reaction conditions (independent parameters) varied in four levels on the degree of grafting (G%) (response parameter). The model yielded a polynomial equation that relates the linear, quadratic and interaction effects of the independent parameters to the response parameter. The analysis of variance (ANOVA) was used to evaluate the results of the model and detect the significant values for the independent parameters. The optimum parameters to achieve a maximum G% were found to be monomer concentration of 55 vol%, absorbed dose of 100 kGy, time in the range of 14-20 h and a temperature of 61. °C. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the properties of the obtained films and provide evidence for grafting. © 2011 Elsevier Ltd.

DOI： 10.1016/j.radphyschem.2011.06.014

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Materials Today Proceedings  

In recent year, there are several reports on the growth of carbon nanotube (CNT) and graphene using a natural source, namely cooking palm oil. However, the accurate geometry and composition of the palm oil molecules are rarely found in literature. In this article, a molecular model is proposed to predict the geometry and molecular structure of the cooking palm oil using density functional theory (DFT) in correlation with other quantum chemistry calculations. Such model is expected to help the researcher in the design of chemical reactions needed for the deposition carbon nanomaterials by chemical vapor deposition (CVD) or pyrolysis. The results of the computational analysis were validated and confirmed to be in good agreement with the measured Fourier transformed infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectra.

DOI： 10.1016/j.matpr.2018.12.073

Scopus

Publishing type：Research paper (scientific journal)   Publisher：Nanoscale Research Letters  

We present a synthesis of large-area single-layer graphene on copper substrate using a refined cooking palm oil, a natural single carbon source, by a home-made spray injector-assisted chemical vapor deposition system. The effects of the distance between spray nozzle and substrate, and growth temperature are studied. From Raman mapping analysis, shorter distance of 1 cm and temperature of around 950 °C lead to the growth of large-area single-layer graphene with a coverage up to 97% of the measured area size of 6400 μm². The crystallinity of the grown single layer graphene is relatively good due to high distribution percentage of FWHM values of 2D band that is below 30 cm⁻¹. However, the defect concentration is relatively high, and it suggests that a flash-cooling technique needs to be introduced.

DOI： 10.1186/s11671-019-2976-0

Open Access

Scopus

Publishing type：Research paper (scientific journal)   Publisher：Sensors and Materials  

Graphene possesses a high surface-to-volume ratio, which enables biomolecules to attach to it for bioelectronic applications. In this article, first, the classification and applications of bioelectronic devices are briefly reviewed. Then, recent work on real fabricated graphene-based bioelectronic devices as well as the analysis of their architecture and design using a computational approach to their charge transport properties are presented and discussed. A comparison to nongraphitic bioelectronic devices is also given. On the macroscale level, the design of devices is elaborated on the basis of a finite element analysis (FEA) approach, and the impact of design on the performance of the devices is discussed. On the nanoscale level, transport phenomena and their mechanisms for different design categories are elaborated on the basis of the density functional theory (DFT) and other quantum chemistry calculations. The calculated and measured charge transport properties of graphene-based bioelectronic devices are also compared with those of other available bioelectronic devices.

DOI： 10.18494/SAM.2018.1805

Open Access

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Sains Malaysiana  

The effects of the annealing temperatures and thicknesses on the shapes, sizes and arrangement of platinum (Pt) nanoparticles (NPs) on graphene and their sensing performance for hydrogen (H2) detection were investigated. It shows strong dependency of the annealing temperatures and thicknesses on the properties of NPs. It was found that the proposed technique is able to form the NPs with good size controllability and uniformity even for thick deposited layer, thus eliminating the requirement of very thin layer of below 5 nm for the direct NP synthesis by evaporation or sputtering. The transport properties of Pt NPs/graphene structure and its sensing performance on H2 at room temperature under various H2 concentration were evaluated. The results showed an acceptable sensing response, indicating an innovative approach to fabricate Pt NPs embedded graphene for gas sensing application.

DOI： 10.17576/jsm-2017-4607-15

Open Access

Scopus

Publishing type：Research paper (scientific journal)   Publisher：Jurnal Teknologi  

Proton conducting membranes obtained by radiation-induced grafting (RIG) of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) films followed by phosphoric acid (PA) doping was prepared. The effect of grafting parameters on the grafted basic moiety was studied. The level of PA doping was controlled by manipulation of reaction parameters. The obtained membranes were investigated with Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC) and DC impedance spectroscopy. The obtained membranes proved to have less-water dependent proton conductivity with a value of 140 mS/cm at 120oC and 17% RH% at acid doping level of of 6.54 mmol/repeat unit. The membranes have potential for application in high temperature polymer electrolyte membrane fuel cell (PEMFC).

Scopus

Publishing type：Research paper (scientific journal)   Publisher：Radiation Physics and Chemistry  

The radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(ethylene-co-tetrafluoroethene) (ETFE) was optimized using the Box-Behnken factorial design available in the response surface method (RSM). The optimized grafting parameters; absorbed dose, monomer concentration, grafting time and reaction temperature were varied in four levels to quantify their effect on the grafting yield (GY). The validity of the statistical model was supported by the small deviation between the predicted (GY=61%) and experimental (GY=57%) values. The optimum conditions for enhancing. GY were determined at the following values: monomer concentration of 48. vol%, absorbed dose of 64. kGy, reaction time of 4. h and temperature of 68. °C. A comparison was made between the optimization model developed for the present grafting system and that for grafting of 1-vinylimidazole (1-VIm) onto ETFE to confirm the validly and reliability of the Box-Behnken for the optimization of various radiation induced grafting reactions. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to investigate the properties of the obtained films and provide evidence for grafting. © 2011 Elsevier Ltd.

DOI： 10.1016/j.radphyschem.2011.12.019

Scopus