H. N.m Ekramul Mahmud | University of Malaya, Malaysia (original) (raw)

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Papers by H. N.m Ekramul Mahmud

Turkish Journal of Chemistry

Introduction Large particle size of gold appears to be a poor catalytic material compared to pall... more Introduction Large particle size of gold appears to be a poor catalytic material compared to palladium, platinum, or ruthenium. Nanoscale gold catalyst is widely regarded as the best green catalytic material for various processes and applications such as selective oxidation of alcohols [1], hydrogenation of nitro compounds [2], laser ignition [3], cosmetic [4], photocatalysis [5,6], and glycosylation of carbohydrate [7]. Catalytic Au nanoparticles (NPs) have great prospects in environmentally friendly and green sustainable chemical processes because of their high activity at room temperature and possessing high oxygen storage capacity, which is suitable for oxidation reaction [8]. Zinc oxide (ZnO) was used as a support material, as this metal has been widely applied in various organic reactions, especially in photocatalytic [9] and oxidation reactions [10,11]. ZnO is a cheap material with excellent surface properties, which increases the catalytic activity. The preparation of gold on ZnO support via the deposition-precipitation method produced gold NPs with a narrow particle size distribution of less than 5 nm [12]. The main products reported for the oxidation of ethylbenzene are acetophenone, 1-phenylethanol and benzaldehyde, and the precursors in pharmaceutical products such as hydrogels, hydrazones, and benzalacetophenones (chalcones) [13]. The catalytic oxidation of ethylbenzene to acetophenone (ACP) has drawn much attention for the past few years, as it is used as a fragrance in soaps, perfumes and cosmetics; as a flavouring agent in foods; as a solvent for plastics and resins; and in the synthesis of pharmaceutical drugs [14]. At present, the industrial production involves high temperature thermal autoxidation in the absence of a heterogeneous catalyst. The oxidation process requires potassium permanganate and potassium dichromate, which produce toxic, dangerous, and hazardous by-products [15]. Oxidants such as tert-butyl hydroperoxide (TBHP), hydrogen peroxide, N-hydroxyphthalimide, iodoxybenzoic acid (IBX), and oxygen could successfully convert alkyl benzene into the desired products [16-1 8]. It is well known that gold supported metal oxides are very active oxidants for CO oxidation [19]. However, no effort has been made for the oxidation of ethylbenzene on Au NPs supported on ZnO. Thus, the main challenge is to achieve a higher conversion of ethylbenzene oxidation, since it is difficult to activate the ethyl carbon for the oxidation reaction. Most of the ethylbenzene oxidation with heterogeneous catalysts demonstrates a lower conversion [13,20,21]. Other catalysts such as zeolite Beta containing ultra-small CoO particles and MnFeSi composite also demonstrated low conversions for the oxidation of ethylbenzene,

The preparation of conducting polymer composite films in aqueous medium using pyrrole monomer, p-... more The preparation of conducting polymer composite films in aqueous medium using pyrrole monomer, p-toluene sulfonate electrolyte and an insulating polymer over indium-tin oxide electrode has been studied. The free standing, flexible and conductive polymer composite films were prepared by potentiostatic method. Poly(vinyl alcohol) and carboxymethylcellulose were used as insulating polymers to make composite films with polypyrrole conducting polymer. The prepared composite films were characterized by Fourier Transform infrared spectroscopy (FT-IR), UV-spectroscopy, scanning electron microscopy (SEM) and measuring the conductivity. It was found that the conductivity increased with the increase in insulating polymer concentration. The morphology of the polymer composites were found different with the different process conditions. The FT-IR results suggest the successful formation of the composite of polypyrrole and the insulating material.

2020 IEEE 8th Conference on Systems, Process and Control (ICSPC), 2020

This paper presents the study of electrical properties comparison between Iron oxide-polypyrrole ... more This paper presents the study of electrical properties comparison between Iron oxide-polypyrrole and Titanium dioxide-polypyrrole nanocomposite model. The study was conducted through a simulation and calculation approach. The results showed that titanium dioxide had a better electrical resistivity and faster time response in comparison to Iron oxide. The Titanium dioxide-polypyrrole nanocomposite showed the good potential to be adopted for the development of a fast response Molecularly Imprinted Polymer (MIP) based DNA biosensor for halal detection.

Journal of Vinyl and Additive Technology

Polypyrrole-poly(viny1 alcohol) (PPy-PVA) and polypyrrole-carboxymethyl cellulose (PPy-CMC) condu... more Polypyrrole-poly(viny1 alcohol) (PPy-PVA) and polypyrrole-carboxymethyl cellulose (PPy-CMC) conducting polymer composite films were electrochemically prepared on Indium Tin Oxide (ITO) glass electrode from an aqueous solution containing pyrrole monomer, p-toluene sulfonate dopant and poly(viny1 alcohol)/carboxymethyl cellulose insulating polymer. The PPy-PVA and PPy- CMC composite films prepared from different process conditions were characterized by Fourier Transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, optical microscopy, dynamic mechanical analysis (DMA), and conductivity measurement. The highest conductivity of 64 Slcm measured at room temperature was shown by PPy-PVA composite film prepared fiom 0.2 M pyrrole, 0.1 M p-toluene sulfonate and 12 x lo4 M PVA at 1.2 volt (vsSCE) among all the PPY-PVA composite films produced. The PPy-CMC composite film prepared from 0.3 M pyrrole, 0.1 M p-toluene sulfonate and 0.03 M CMC at 1.2 volt (vs SCE) showed the highest conductivity of 38 Slcm among all the PPy-CMC composite films produced. The FT-IR study of PPy-PVA and PPy- CMC composite films shows the evidence of the incorporation of PVA and CMC in PPy structure forming PPy-PVA and PPy-CMC composite films, respectively. The conductivity data of PPy-PVA shows that with the increase in PVA concentration in the pyrrole solution, the conductivity of the prepared PPy-PVA film is increasing up to certain level due to the increase in conjugation length and later it is decreasing with further increase in PVA concentration, which is again linked with the conjugation length decrease. This is supported by the FT-IR band intensity of Ic=c/Ic-N. The FT-IR study of PPy-CMC composite films shows that with the increase in CMC concentration from 0.005 M to 0.01 M, the conductivity first decreased and later with further increase in CMC concentration the conductivity showed an increasing trend and finally at 0.04 M CMC, the conductivity dropped. The DMA results of PPy-PVA and PPy-CMC composite films show the enhanced mechanical properties of both the composite films over PPy films without PVA or CMC. The storage moduli of both the composite films were found much higher than the PPy film prepared without PVA or CMC indicating that PPy-PVA and PPy-CMC composite films are much stiffer than PPy films. The gradual decrease of storage moduli of both the composite films with the increase in temperature ranging from 25 "C to 250 "C suggests that the composite films have got flexibility in their chains and thus the chains are soft. On the other hand, the storage modulus of PPy film only without PVA or CMC shows no decreasing tendency with the increase in temperature ranging from 25 "C to 250 "C indicating that the PPy film is very hard and have got no flexibility in its backbone chain. The XRD results of both PPy-CMC and PPy-PVA composite films show that the films are amorphous and have got very little order. The optical micrographs of PPy-CMC and PPy-PVA show the globular surface morphology. The changes in globular surface morphology with the change in process condition of the film preparation indicates that the process parameters used to prepare the composite films have got a good influence over the surface morphology. The intense polymerization reaction has been evidenced from the surface morphology of the films. The results of electromagnetic interference (EMI) shielding effectiveness in the microwave range of 8-12 GHz show that the highest shielding effectiveness of 45.67 dB measured in the microwave range of 8-12 GHz corresponds to the total attenuation of 99.4 % of microwave energy has been exhibited by the Pe-PVA composite film prepared from 0.2 M pyrrole, 0.1 M p-toluene sulfonate and 12 x 10" M PVA at 1.2 volt (vs SCE) among all the PPy-PVA composite films prepared. The highest shielding effectiveness of 35.7 dB measured in the microwave range corresponds to the total attenuation of 98.32 % of microwave energy has been exhibited by the PPy-CMC composite film prepared fiom 0.3 M pyrrole, 0.1 M p-toluene sulfonate and 0.03 M CMC at 1.2 volt (vs SCE) among all the PPy-CMC composite films prepared. Thus, the promise of finding any electromagnetic interference (EMI) shielding applications in the microwave frequency range lies in PPy-PVA and PPy-CMC conducting polymer composite films.

Energies, 2013

The need for clean, inexpensive and renewable energy has increasingly turned research attention t... more The need for clean, inexpensive and renewable energy has increasingly turned research attention towards polymer photovoltaic cells. However, the performance efficiency of these devices is still low in comparison with silicon-based devices. The recent introduction of new materials and processing techniques has resulted in a remarkable increase in power-conversion efficiency, with a value above 10%. Controlling the interpenetrating network morphology is a key factor in obtaining devices with improved performance. This review focuses on the influence of controlled nanoscale morphology on the overall performance of bulk-heterojunction (BHJ) photovoltaic cells. Strategies such as the use of solvents, solvent annealing, polymer nanowires (NWs), and donor-acceptor (D-A) blend ratios employed to control the active-layer morphologies are all discussed.

ABSTRACT: An effort has been made to produce polypyrrole-carboxymethylcelllulose (PPY-CMC) conduc... more ABSTRACT: An effort has been made to produce polypyrrole-carboxymethylcelllulose (PPY-CMC) conducting polymer composite film on Indium Tin Oxide (ITO) glass electrode from an aqueous solution containing pyrrole monomer, p-toluenesulfonate electrolyte and carboxymethylcellulose (CMC) insulating polymer. The conductivity of the prepared composite film was found to increase with the increase in CMC concentration in pyrrole solution. The optical microscopic study showed the influence of CMC concentration in the pyrrole solution on the morphological changes of the prepared film. The dynamic mechanical analysis (DMA) on the prepared PPY-CMC film revealed the higher plastic property of the PPY-CMC composite film due to the addition of CMC in the polypyrrole structure. The electromagnetic interference (EMI) shielding effectiveness of PPY-CMC film in the frequency range of 8-12 GHz showed a high shielding effectiveness above 41 db, which supported its probable use in various electromagnetic ...

Http Dx Doi Org 10 1080 10601320903399834, Dec 1, 2009

RSC Adv., 2016

Dioxin-like compounds (DLCs) are considered as persistent bioaccumulative toxicants with a number... more Dioxin-like compounds (DLCs) are considered as persistent bioaccumulative toxicants with a number of continuing issues in the fields of ecotoxicology and bioassay.

Sensors and Materials

A novel potentiometric anion-selective self-plasticizing polymeric membrane based on 5,10,15,20-t... more A novel potentiometric anion-selective self-plasticizing polymeric membrane based on 5,10,15,20-tetrakis-(4-methoxyphenyl)-21H,23H-porphyrin cobalt(II) (CoTMeOPP)-silvernanoparticle-modified glassy carbon electrode (GCE) was examined for use in the detection of thiocyanate anions. The membrane was characterized by X-ray diffraction (XRD) analysis, field-emission electron microscopy, UV-visible diffused ref lectance spectroscopy, and fluorescence spectroscopy. The prepared ion-selective sensor exhibited a positive Nernstian response and deviated from the classical Hofmeister selective pattern with a significantly sensitive and enhanced response towards the thiocyanate anion. It exhibited a rapid response of 3 s with a low detection limit of 9.55 × 10 −8 M within the concentration range from 1 × 10 −1 to 1 × 10 −7 M. The sensor also showed a high selectivity for the thiocyanate anion over a variety of anions. The influence of the additives was studied and this sensor was successfully applied to the potentiometric titration of silver nitrate and the direct determination of the amount of thiocyanate anions in a wide array of samples of river water, ex-mine lake sediment, human saliva, and fish.

Turkish Journal of Chemistry

2020 IEEE 8th Conference on Systems, Process and Control (ICSPC), 2020

Journal of Vinyl and Additive Technology

Energies, 2013

Http Dx Doi Org 10 1080 10601320903399834, Dec 1, 2009

RSC Adv., 2016

Sensors and Materials

Energies

The need for clean, inexpensive and renewable energy has increasingly turned research attention t... more The need for clean, inexpensive and renewable energy has increasingly turned research attention towards polymer photovoltaic cells. However, the performance efficiency of these devices is still low in comparison with silicon-based devices. The recent introduction of new materials and processing techniques has resulted in a remarkable increase in power-conversion efficiency, with a value above 10%. Controlling the interpenetrating network morphology is a key factor in obtaining devices with improved performance. This review focuses on the influence of controlled nanoscale morphology on the overall performance of bulk-heterojunction (BHJ) photovoltaic cells. Strategies such as the use of solvents, solvent annealing, polymer nanowires (NWs), and donor–acceptor (D–A) blend ratios employed to control the active-layer morphologies are all discussed.