Microwave-assisted size control of CdS nanocrystallites

Abstract

The size and size-distribution of CdS nanocrystallites is controlled by the microwave-assisted reaction of cadmium acetate with thiourea in N,N-dimethylformamide (DMF). The absorption onset of the CdS nanocrystallites shifts to longer wavelength with increasing irradiation time, indicating particle size growth under prolonged irradiation. However, when the microwave irradiation of the solution is periodically interrupted and then repeated, keeping the solution at ambient temperature before each irradiation, the absorption onset remains at the same wavelength and only the optical density of the absorption band is increased, suggesting that the particle growth occurs only during the continuous irradiation and stops once the system is cooled down. Photoluminescence observed for the CdS nanocrystallites changes with the irradiation time and the repetition of the irradiation, suggesting a structural change of the nanocrystallite surface due to the consumption of excess Cd 2z .

Microwave assisted green synthesis and characterization of silver/montmorillonite heterostructures with improved antimicrobial properties

“…The rapid transfer of MW energy to thermal energy in polar solution and the penetration property of MW electromagnetic radiation through solution result in a uniform heating for the reaction solution, giving a size-controlled synthesis of nanoparticles, in a narrow range when compared to the conventional heating by thermal conduction and convection (Motshekga et al, 2011;Wada et al, 2001;Yin et al, 2004). The MW radiation heats up a material through its dielectric loss, which converts the radiation energy into thermal energy.…”

Reactive Crystallization of Lithium Carbonate Nanoparticles by Microwave Irradiation of Aqueous Solution Containing CO2 Microbubbles

“…During microwave irradiation, local hightemperature regions (hot-spots) are formed because of the vibration of polar molecules and ions, and thus, rapid and efficient internal heating is achieved. Microwave irradiation has been recently employed in the solid-phase synthesis of oxides and sulfides and fine metal powders, fabrication of superconductors and semiconductors, pyrolysis of metal-organic precursors for powder synthesis, and crystallization of inorganic compounds from solution (Wada et al, 2001;Guo et al, 2006;Heuser et al, 2007). In this study, for developing a crystallization technique that enables the control of the crystal properties of carbonates with high dissolubility by the generation of local supersaturation regions, we studied the reactive crystallization of Li 2 CO 3 using minute gas-liquid interfaces around CO 2 microbubbles activated by microwave irradiation.…”

One-pot sonochemical synthesis of CdS nanoparticles: photocatalytic and electrical properties

“…Many studies have focused on CdS because of its high photosensitivity and potential application in photoconducting cells and a variety of optoelectronic conversion devices including photodetectors and thin film solar cells [4]. A large number of synthetic methods such as solvothermal, hydrothermal [5,6] and sonochemical process [7], microwave heating [8] and solution-based chemical methods [9] provide effective routes to prepare semiconductor nanoparticles. For nanoparticles prepared by solution-based chemical methods, a capping agent, which adsorbs on to the nanoparticle surface, is generally added both to control the size of the nanoparticles and to prevent agglomeration of the synthesized particles.…”