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RISS 인기검색어
- 검색키워드
- 저자 : ( Rizwan Wahab ) (검색결과 16 건)
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Rizwan Wahab,김영순,신형식 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.5
This paper presents the fabrication of pencil like zinc oxide nanorods by solution method using precursor zinc acetate di-hydrate (Zn(Ac)2.2H2O) and alkali sodium hydroxide (NaOH) at a very low refluxing temperature (75 °C) for different ageing/ refluxing (12 h, 24 h, 36 h, 48 h and 60 h) time intervals. The morphological observation was carried out by using Field Emission Scanning Electron Microscopy (FESEM). The FESEM revealed that as the aging/refluxing time increased, the size (length and diameter) of the zinc oxide nanorods also increased. Furthermore, the morphology and crystallinity of the products grown were also confirmed by Transmission Electron Microscopy (TEM), high-resolution TEM, and Selected Area Electron Diffraction (SAED) patterns, which indicated that grown pencils grew along a [0001] direction with an ideal lattice fringe distance of ~0.52 nm. The optical properties of the grown pencil-like zinc oxide nanorods were characterized by using UV-vis spectroscopy. Strong absorbance peaks were observed at ~375 nm to 378 nm,which is the characteristic peak for the wurtzite hexagonal phase of ZnO. The FTIR spectroscopic measurement showed a standard peak of zinc oxide in the range of 428 cm−1to 520 cm−1. Additionally, on the basis of chemical and morphological analysis, we have also proposed a possible growth mechanism for pencillike zinc oxide nanostructures.
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Rizwan Wahab,S. G. Ansari,김영순,M. S. Dhage,서형기,송민우,신형식 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.3
A systematic study is presented on the conversion of zinc sulfide to zinc oxide nanoparticles as a function of annealing temperature. Zinc acetate dihydrate (Zn(CH3COO)2.2H2O) and thiourea (NH2CSNH2) are used as precursors to synthesize ZnS and then ZnO. The aqueous solution of the precursor was refluxed at 90 °C for over 12 h. The synthesized complex was then annealed at 300 °C, 500 °C, 700 °C, and 900 °C in air for one hour. From elemental analyses, it was found that the as-synthesized powder is a mixture of ZnS and ZnO, which annealing later converts to the zinc oxide phase only. The morphological observations revealed spherical particles of various sizes (20 nm to 300 nm) while increasing the annealing temperatures. A drastic change in the vibration bands is noticed with annealing. Photoelectron peaks related to sulfur and carbon are observed for synthesized powder, whereas, these peaks disappeared when annealed at 500 °C. A systematic study is presented on the conversion of zinc sulfide to zinc oxide nanoparticles as a function of annealing temperature. Zinc acetate dihydrate (Zn(CH3COO)2.2H2O) and thiourea (NH2CSNH2) are used as precursors to synthesize ZnS and then ZnO. The aqueous solution of the precursor was refluxed at 90 °C for over 12 h. The synthesized complex was then annealed at 300 °C, 500 °C, 700 °C, and 900 °C in air for one hour. From elemental analyses, it was found that the as-synthesized powder is a mixture of ZnS and ZnO, which annealing later converts to the zinc oxide phase only. The morphological observations revealed spherical particles of various sizes (20 nm to 300 nm) while increasing the annealing temperatures. A drastic change in the vibration bands is noticed with annealing. Photoelectron peaks related to sulfur and carbon are observed for synthesized powder, whereas, these peaks disappeared when annealed at 500 °C.
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Rizwan Wahab,Farheen Khan 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.22 No.-
The zinc acetate di-hydrate and sodium hydroxide were used in synthesis of zinc oxide micro-flowers(ZnO-MFs) via soft chemical process and photocatalytic activity determined in presence of methylenered (MR) dye. The crystallinity and morphology of the grown nanostructures were investigated usingXRD, FESEM, and TEM. Additionally, the analytical method was also applied to observe the concentrationof ZnO-MFs affected on organic methylene red dye, which was established by statistical parameters. Theabsorption spectra of ZnO-MFs composed with nanorods and MR dye show maximum absorbance at540 nm. The optical and regression characteristics of the proposed method were evaluated by analyticaltechniques.
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Rizwan Wahab,김영순,신형식 한국물리학회 2011 Current Applied Physics Vol.11 No.3
Differently shaped zinc oxide nanostructures were synthesized at^90 ℃ by refluxing process at different refluxing times (6, 12, 18 and 24 h) via the solution method using zinc acetate dihydrate as a source material and hydrazine hydrate. Heterostructures like needle shaped nanorods, flowers composed with nanorods, pencil like zinc oxide nanorods and square shaped zinc oxide micro-particles were observed using field emission electron microscopy (FE-SEM) as functions of varying refluxing time of the solution of zinc acetate dihydrate (Zn(Ac)_2 2H_2O) and hydrazine hydrate (N_2H_4 H_2O). A high-resolution transmission electron microscopic (HR-TEM) observation supports FE-SEM observations and revealed that nanostructures grew along [0001] direction with an ideal lattice fringe distance of 0.52 nm, same as that of bulk ZnO. X-ray diffraction patterns present good crystalline properties and that the obtained powder is zinc oxide without any other impurities. The compositional study, FTIR spectroscopic measurement showed a standard peak of zinc oxide at 518 cm^-1. In addition to this, we also proposed the chemical growth mechanism of different types of grown zinc oxide nanostructures.
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Formation of ZnO Micro-Flowers Prepared via Solution Process and their Antibacterial Activity
Wahab, Rizwan,Kim, Young-Soon,Mishra, Amrita,Yun, Soon-Il,Shin, Hyung-Shik Springer 2010 NANOSCALE RESEARCH LETTERS Vol.5 No.10
<P>This paper presents the fabrication and characterization of zinc oxide micro-flowers and their antibacterial activity. The micro-flowers of zinc oxide composed of hexagonal nanorods have been prepared via solution process using precursor zinc acetate di-hydrate and sodium hydroxide in 3 h of refluxing time at ~90°C. The antibacterial activities of grown micro-flowers were investigated against four pathogenic bacteria namely <I>S. aureus, E. coli, S. typhimurium and K. pneumoniae</I> by taking five different concentrations (5–45 μg/ml) of ZnO micro-flowers (ZnO-MFs). Our investigation reveals that at lowest concentration of ZnO-MFs solution inhibiting the growth of microbial strain which was found to be 5 μg/ml for all the tested pathogens. Additionally, on the basis of morphological and chemical observations, a chemical reaction mechanism of ZnO-MFs composed of hexagonal nanorods was also proposed.</P>
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Synthesis of Zinc Oxide Nano Rods, Sheet and Flower at by the Sol-gel Method
Wahab Rizwan,Ansari S.G.,Kim Y.S.,Dar M.A.,Shin H.S. 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Synthesis of zinc oxide nanorods, sheets and flower like structure were done by the sol-gel method using zinc acetate dihydrate and sodium hydroxide at with 12 hours refluxing time nanorods, in case of as synthesized powder, with diameter of 20-60nm. Annealing at higher temperature (300 and ,) in air ambient changes the morphology to sheet and flower like structure. The standard peak of zinc oxide was observed in IR at . The UV-VIS spectroscopy of zinc oxide shows a characteristic peak at 375nm.
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Synthesis, Characterization and Effect of pH Variation on Zinc Oxide Nanostructures
Wahab, Rizwan,Kim, Young-Soon,Shin, Hyung-Shik The Japan Institute of Metals 2009 Materials Transactions Vol.50 No.8
<P>Here we present a systematic study on the morphological deviation of ZnO nanostructure (from sheets to micro-flowers) by varying pH of the solution via precipitation method. In this regard, zinc nitrate hexa-hydrate, NaOH and hydroxylamine hydrochloride (NH<SUB>2</SUB>OH·HCl) were used. The solution of all three compounds was refluxed at a very low temperature (60°C) for short time (20 min). The solution pH was calibrated from 6 to 12 by the controlled addition of NaOH and HCl. We have observed from FESEM (field emission scanning electron microscopy) that the morphology of ZnO microballs composed with thin sheets markedly varies from sheet (at pH=6) to micro-flower composed with sheets of zinc oxide (pH=10–12). Further the morphology and crystallinity were also studied by the TEM (transmission electron microscopy) and HR-TEM (High resolution transmission electron microscopy) and it’s clearly consistent with the FESEM observations. The FTIR spectroscopic measurement also confirms the compositional analysis of ZnO and it comes in the range of 475 to 424 cm<SUP>−1</SUP> which is a standard peak of ZnO. In addition to this, the amount of H<SUP>+</SUP> and OH<SUP>−</SUP> ions are found a key to control the structure of studied material and discussed in the growth mechanism.</P>
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