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Arshi, Nishat,Ahmed, Faheem,Kumar, Shalendra,Anwar, M.S.,Lu, Junqing,Koo, Bon Heun,Lee, Chan Gyu Elsevier 2011 Current Applied Physics Vol.11 No.1
<P><B>Abstract</B></P><P>We report a simple one step microwave irradiation method for the synthesis of gold nanoparticles using citric acid as reducing agent and cetyl trimethyl ammonium bromide (CTAB) as binding agent. The reaction was completed under two different microwave irradiation times (40 s and 70 s) for the production of two types of gold nanoparticles. The synthesized nanoparticles were characterized using UV–Vis absorption spectroscopy and transmission electron microscopy (TEM) measurements. UV–Vis study revealed the formation of gold nanoparticles with surface plasmon absorption maxima at 590 and 560 nm for 40 and 70 s irradiation time respectively. From TEM analysis, it is observed that the gold nanoparticles have spherical shape with particle size distribution in the range 1–10 nm and 1–2 nm for 40 s and 70 s irradiation time respectively. Antibacterial activity of gold nanoparticles as a function of particle concentration against gram-negative bacterium <I>Escherichia coli</I> (<I>E. coli</I>) was carried out in solid growth media. The two types of gold nanoparticles show high antibacterial activity with zone of inhibition of about 22 mm against <I>E. coli</I> (ATCC 25922 strain). Very small difference in the antibacterial activity for the two types of gold nanoparticles were observed. Though nanoparticles synthesized for 70 s irradiation time show slightly better antibacterial activity.</P> <P><B>Highlights</B></P><P>► Gold nanoparticles have been successfully synthesized using microwave irradiation technique. ► The mean diameter was ∼ 4.05 nm for 40 s and ∼1.05 nm for 70 s. ► Characteristic absorption peak was found to be 590 nm for 40 s and 560 nm for 70 s. ► The zone of inhibition for the two types of nanoparticles was almost similar (22 mm). ► Smaller size nanoparticles synthesized for 70s showed a slightly better antibacterial action.</P>
Comparative study of the Ag/PVP nanocomposites synthesized in water and in ethylene glycol
Arshi, Nishat,Ahmed, Faheem,Kumar, Shalendra,Anwar, M.S.,Koo, Bon Heun,Lee, Chan Gyu Elsevier 2011 Current Applied Physics Vol.11 No.1
<P><B>Abstract</B></P><P>We report direct synthesis of Ag/PVP nanocomposites using PVP (polyvinylpyrrolidone) as a reducing agent. Ag/PVP nanocomposites were synthesized after mixing PVP with acetone and a small amount of aqueous silver nitrate (AgNO<SUB>3</SUB>) under magnetic stirring. The Ag/PVP colloids were then dissolved in water (sample 1) and in ethylene glycol (sample 2) and stirred for 10 days. UV/vis spectra show surface plasmon band in the visible region, centered at wavelengths between 435 and 445nm, a clear consequence of the nano size of dilute Ag particles. TEM results showed that the Ag/PVP nanocomposites have particle sizes ranging from 1 to 6nm and 1 to 12nm for colloids in water and ethylene glycol respectively. Antibacterial activity of these silver nanocomposites as a function of particles concentration against gram-negative bacterium <I>Escherichia coli</I> (<I>E. coli</I>) was carried out in solid growth media. Both the nanocomposites showed good antibacterial activity and caused a growth delay of <I>E. coli</I> with zone of inhibition ∼16mm. There was very little difference between antibacterial activities of two types of silver nanocomposites, though sample 1 with smaller size showed a slightly better antibacterial action.</P> <P><B>Highlights</B></P><P>► Ag nanocomposites were synthesized in water and ethylene glycol with solution chemistry method. ► The Mean diameter was found to be 3.4 and 5.3 nm for water and in ethylene glycol. ► Characteristic absorption peak was found to be 435 and 445 nm in water and ethylene glycol. ► The zone of inhibition for the two types of nanocomposites was almost similar (16 mm). ► Nanocomposites in water with smaller size showed a slightly better antibacterial action.</P>
Nishat Arshi,Junqing Lu,이찬규,구본흔,Faheem Ahmed 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.6
In this work, the effect of deposition power on the structural, morphological, and electrical properties of e-beam evaporated tantalum films was investigated. The as-deposited tantalum films were characterized using x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive x-ray (EDX) and four-point probe resistivity measurements. The XRD patterns revealed the growth of a tetragonal crystalline structure (β-Ta), and the crystallinity of the films increased with increased deposition power. The FESEM images showed that the tantalum film morphology was smooth with fine spherical particles on the surface, and the grain size was found to increase with deposition power. The resistivity of the tantalum films decreased with increased deposition power.
NOVEL AND COST-EFFECTIVE SYNTHESIS OF SILVER NANOCRYSTALS: A GREEN SYNTHESIS
NISHAT ARSHI,FAHEEM AHMED,M. S. ANWAR,SHALENDRA KUMAR,구본흔,여준청,CHAN GYU LEE 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.4
This paper reports the study on the synthesis and characterization of silver nanocrystals by a two-step synthesis procedure. The first step is the solution-free hand grinding of silver foil and sugar at room temperature for few minutes. The second step is the thermal decomposition of silver/sugar composite to form silver nanocrystals. The as-synthesized silver nanocrystals were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet visible (UV/Vis) spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies. The XRD pattern showed a face-centered cubic structure (single phase) with high crystallinity. The lattice parameters calculated from XRD pattern were found to be a = 4.12 Å for silver nanocrystals with average grain size of ~ 19 nm. The energy dispersive analysis of X-rays (EDAX) of silver nanocrystals confirmed the presence of silver and no peak of any secondary phase was detected. FESEM and AFM studies showed that the crystals have cube-like morphology. TEM results showed that the size of silver nanocrystals was found to be ~ 22 nm. This novel synthesis route, not reported earlier, would be a promising candidate for a variety of future applications of silver nanocrystals.
Ahmed, Faheem,Arshi, Nishat,Anwar, M. S.,Alsharaeh, Edreese,Koo, Bon Heun,Azam, Ameer American Scientific Publishers 2018 Science Of Advanced Materials Vol.10 No.1
<P>In this work, mono-disperse hematite iron oxide (alpha-Fe2O3) nanoparticles with continuously tunable sizes from 2 to 11 nm by using Sb doping in alpha-Fe2O3 were synthesized by a sonication method at room temperature followed by calcination. By varying the concentration of the Sb, precise control on the size of the alpha-Fe2O3 nanoparticles could be established. The X-ray diffraction (XRD), and high resolution transmission electron microscopy (HR-TEM) studies confirmed that the prepared nanoparticles were hematite with high crystallinity. The optical measurements showed that the band gap of the Sb-doped alpha-Fe2O3 nanoparticles increased with Sb doping. Transmission electron microscopy (TEM) results showed that the alpha-Fe2O3 nanoparticles appeared as spherical dots, and the size decreased from 11 to 2 nm with Sb doping. Magnetic studies revealed that all the Sb doped samples were superparamagnetic at 300 K, and the increase in Sb doping can controllably decreased the blocking temperature from 248 K for pure alpha-Fe2O3 nanoparticles to 209 K for 5% Sb doped, respectively. The presented method might be useful for controlling the diverse size of crystalline inorganic materials for a variety of applications.</P>
Ahmed, Faheem,Arshi, Nishat,Anwar, M S,Danish, Rehan,Koo, Bon Heun American Scientific Publishers 2015 Journal of nanoscience and nanotechnology Vol.15 No.2
<P>In this work, pure and 3% TM (Co, Ni, and Cu)-doped ZnO nanostructures were prepared by microwave-hydrothermal method. The striking similarities between changes in the lattice volume, bandgap energy, morphology and saturation magnetization indicated a strong correlation between these properties. XRD, SAED and HRTEM analyses revealed that all the TM-doped ZnO nano-structures have wurtzite structure and no secondary phase was detected. FESEM and TEM results confirmed a higher aspect ratio and highly crystalline nature of nanostructures. Raman spectra revealed that no defect related mode was observed which indicated that the nanostructures have high quality and negligible defects. The value of bandgap was found to decrease with the increase in atomic number of TM dopants. RTFM was observed in all the TM-doped ZnO nanostructures and the value of Ms and Mr were decreased with TM dopants.</P>