Alam Abedini

Abstract: ZnS and CdS nanoparticles were prepared by a simple microwave irradiation method under mild conditions. The obtained nanoparticles were characterized by XRD, TEM and EDX. The results indicated that high purity of nanosized ZnS and CdS was successfully obtained with cubic and hexagonal crystalline structures, respectively. The band gap energies of ZnS and CdS nanoparticles were estimated using UV-visible absorption spectra to be about 4.22 and 2.64 eV, respectively. Photocatalytic degradation of methylene blue was carried out using physical mixtures of ZnS and CdS nanoparticles under a 500-W halogen lamp of visible light irradiation. The residual concentration of methylene blue solution was monitored using UV-visible absorption spectrometry. From the study of the variation in composition of ZnS:CdS, a composition of 1:4 (by weight) was found to be very efficient for degradation of methylene blue. In this case the degradation efficiency of the photocatalyst nanoparticles aft...

Colloidal Fe3O4 nanoparticles were synthesized using a gamma-radiolysis method in an aqueous solution containing iron chloride in presence of polyvinyl alcohol and isopropanol as colloidal stabilizer and hydroxyl radical scavenger, respectively. Gamma irradiation was carried out in a 60Co gamma source chamber at different absorbed doses. Increasing the radiation dose above a certain critical dose (100 kGy) leads to particle agglomeration enhancement, and this can influence the structure and crystallinity, and consequently the magnetic properties of the resultant particles. The optimal condition for formation of Fe3O4 nanoparticles with a uniform and narrow size distribution occurred at a dose of 100 kGy, as confirmed by X-ray diffractometry and transmission electron microscopy. A vibrating sample magnetometry study showed that, when radiation dose increased, the saturation and remanence magnetization decreased, whereas the coercivity and the remanence ratio increased. This magnetic ...

The last two decades have seen remarkable progress in nanoscience and nanotechnology particularly in the synthesis of metal nanomaterials, aiming at finding better materials that have desired physical and chemical properties from enhancement of the surface and quantum confinement effects. Intermetallic aluminides such as Al-Ni and Al-Cu bimetallic nanoparticles have attractive properties for examples low densities, high strength and stiffness at elevated temperatures, strong resistances to mechanical, corrosion, acids and alkalis, and outstanding catalytic activity. They are of significant for wide potential applications in pigments, catalysts, and absorbents for Al-Cu bimetallic nanoparticles and in turbine blades, automobile engines, aircraft,electricity generation, and anode electrode materials for Al-Ni bimetallic nanoparticles. Such impressive characteristics and applications of Al-Ni and Al-Cu bimetallic nanoparticles have led us to research their functional systems with the o...

In this paper, the effect of channel width variation on performance of double lateral gate junctionless transistors in the depletion and accumulation regimes is investigated. The characteristics of the device with various channel widths is comprehensively examined through analysis of on and off state current, threshold voltage (V th), transconductance (g m) and drain conductance (g D) variation in each operating regime. The carriers’ density distribution, electric field components and mobility are investigated through 3-D numerical simulations of the device to illustrate the variation of output characteristics. The results show that as the width decreases, the off-current (IOFF) decreases significantly as a result of better electrostatic control of the lateral gates over the channel. The on-current (ION) is also decreased mainly due to the doping-dependent mobility degradation.It is also indicated that between the flat-band and fully depleted (pinch off) variation of the majority carriers is the main parameter that modifies the characteristics of the device, while the mobility variation is recognized as the basic factor in the accumulation regime.

There is increasing interest in tuning the physical properties of semiconductor nanostructures using metal nanoparticles. In this work, ZnO nanosphere covered with Ag nanoparticles were synthesized using gamma–radiation-assisted method. The amount of deposited Ag nanoparticles is controlled by changing irradiation dose in the range of 30–100 kGy in order to tune the semiconductor–metal interaction. The successful deposition of Ag on the ZnO nanoparticles is examined by analyzing the morphology, microstructure, optical, and magnetic properties of ZnO/Ag nanoparticles through field emission scanning electron (FESEM), microscopy X-ray diffraction spectra, UV-visible absorption, photoluminescence measurement, and vibrating sample magnetometer. FESEM and elemental mapping results confirmed that Ag nanoparticles have been concentrated at the surface of spherical ZnO particles. Moreover, formation of pure metallic Ag nanoparticles has been confirmed by XRD analysis. UV-visible absorption spectra of obtained ZnO/Ag showed two combined peaks, a weak peak at the shoulder around 360 nm corresponds to ZnO and a sharp absorption at 420 nm refers to spherical Ag nanoparticles. Obtained results from photoluminescence revealed that the near-band-edge emission and defect-related visible emission bands of ZnO could be enhanced dramatically at the same time by deposition of Ag nanoparticles, which was ascribed to localized surface plasmon–exciton coupling and surface plasmon scattering. Controlling the semiconductor and metal coupling effect is interesting because of its application in highly efficient optoelectronic devices and biosensor.

Hydrous Fe/Ni-based oxide components nanoparticles in core/shell structure were successfully synthesized by radiolytic reduction method. Structural analysis confirmed the formation of double-layered nanoparticles with iron oxide core, which are more easily reducible by gamma radiation rather than Ni ions, and (Fe, Ni)OOH shell at lower irradiation dose. At high irradiation doses, the formation of triple-layered nanoparticles with the core of iron oxide and the outer shell of nickel/nickel oxide and middle layer made of hydroxide of both kinds of metals were observed. The modification of core, shell and middle layer effectively influence on final structure which consequently affect on the magnetic and mechanical properties of the final products. By increasing radiation dose, the phase transition between super-paramagnetic to ferromagnetic has been observed. Moreover, the stiffness value increased by irradiation dose increasing. The phase transition can be explained by variation of Ni content at the surface of iron oxide core, while the increase in the stiffness of the final product is mainly due to the increasing in Ni content of final products.

This paper focuses on the recent advances on radiolysis-assisted shape-controlled synthesis of noble metal nanostructures. The techniques and protocols for producing desirable shapes of noble metal nanoparticles are discussed through introducing the critical parameters which can influence the nucleation and growth mechanisms. Nucleation rate plays a vital role on the crystallinity of seeds while growth rate of different seeds' facets determines the final shape of resultant nanoparticles. Nucleation and growth rate both can be altered with factors such as absorbed dose, capping agents, and experimental environment condition to control the final shape. Remarkable physical and chemical properties of synthesized noble metal nanoparticles by controlled morphology have been systematically evaluated to fully explore their applications.

ABSTRACT In this work, luminescent triangular silver nanoparticles were synthesized by radiolytic reduction method. The results showed that by variation of irradiation dose, morphology of silver nanoparticles can be converted from spherical to triangular. These shape variations mainly arise from competition between adsorption rate of polymer chains on (111) facets and reduction rate of the Ag+ ions along (110) facets during increasing dose. Furthermore, the dramatically enhanced photoluminescence spectra were observed from triangular Ag nanoparticles. This unusual behavior can be explained by excitation of dipolar and quadrupolar resonance in triangular nanoparticles which increase the electric fields at the surface.

ABSTRACT Cu – Al bimetallic nanoparticles were synthesized by gamma irradiation technique in aqueous solutions containing metal chlorides as precursors, polyvinyl alcohol (PVA) as a capping agent, isopropanol as a radical scavenger, and distilled water as a solvent. The Cu – Al bimetallic nanoparticles were characterized by transmission electron microscopy (TEM), UV-visible absorption spectrometry, powder X-ray diffractometer (XRD), and Energy-dispersive X-ray spectroscopy (EDX). The TEM, XRD, EDX, and absorption analyses confirmed the formation of core-shell structure of Cu – Al bimetallic nanoparticles at lower Cu2+/Al3+ mole ratio, and the formation of Cu – Al alloy nanoparticles at higher Cu2+/Al3+ mole ratio. The TEM analysis for particle size and size distribution revealed that the average particle size of Cu – Al bimetallic nanoparticles decreased with the increase of absorbed dose. It may be explained due to the competition between nucleation and aggregation processes in the formation of metallic nanoparticles under irradiation.

ABSTRACT Hollow Fe x Ni(1−x)OOH nanospheres with average diameter and shell thickness of about 15 and 5 nm were successfully synthesized for the first time through the radiation induced self-template method. The fast outward diffusion of Fe(III) ions due to Kirkendall effect between the core (FeOOH) and the shell (Fe x Ni(1−x)OOH) is the main reason for appearing the hollow nanoparticles. The results showed that a passive layer of Fe(III) species was formed at core and shell interface and Ni(II) ions play an important role in hollowing process of nanoparticles.

This review presents an introduction to the synthesis of metallic nanoparticles by radiation-induced method, especially gamma irradiation. This method offers some benefits over the conventional methods because it provides fully reduced and highly pure nanoparticles free from by-products or chemical reducing agents, and is capable of controlling the particle size and structure. The nucleation and growth mechanism of metallic nanoparticles are also discussed. The competition between nucleation and growth process in the formation of nanoparticles can determine the size of nanoparticles which is influenced by certain parameters such as the choice of solvents and stabilizer, the precursor to stabilizer ratio, pH during synthesis, and absorbed dose.