Microwave-Enhanced Reaction Rates for Nanoparticle Synthesis

Abstract

Microwave reactor methodologies are unique in their ability to be scaled-up without suffering thermal gradient effects, providing a potentially industrially important improvement in nanocrystal synthetic methodology over convective methods. Synthesis of high-quality, near monodispersity nanoscale InGaP, InP, and CdSe have been prepared via direct microwave heating of the molecular precursors rather than convective heating of the solvent. Microwave dielectric heating not only enhances the rate of formation, it also enhances the material quality and size distributions. The reaction rates are influenced by the microwave field and by additives. The final quality of the microwave-generated materials depends on the reactant choice, the applied power, the reaction time, and temperature. CdSe nanocrystals prepared in the presence of a strong microwave absorber exhibit sharp excitonic features and a QY of 68% for microwave-grown materials. InGaP and InP are rapidly formed at 280 degrees C in minutes, yielding clean reactions and monodisperse size distributions that require no size-selective precipitation and result in the highest out of batch quantum efficiency reported to date of 15% prior to chemical etching. The use of microwave (MW) methodology is readily scalable to larger reaction volumes, allows faster reaction times, removes the need for high-temperature injection, and suggests a specific microwave effect may be present in these reactions.

Graphene based metal and metal oxide nanocomposites: synthesis, properties and their applications

“…133 Thermal annealing is usually carried out by thermal irradiation; however some unconventional heating resources have been examined for thermal reduction, such as microwave irradiation (MWI). 158,159 In this process, microwave energy is transformed into heat through a microwave absorbent. Other conventional heating methods, heat the reaction mixture uniformly and rapidly.…”

Microwave-Assisted Oxidation of Electrospun Turbostratic Carbon Nanofibers for Tailoring Energy Storage Capabilities

“…[13][14][15][16][17][18][19][20][21][22][23] The development of structural modification strategies for ECNFs as well as an understanding of structure-property relationships is desirable to guide the use of these materials. Microwave irradiation, which reduces reaction time dramatically due to the unique microwave dielectric heating mechanism, [24] has enabled efficient preparation and modification of various materials such as metal-organic frameworks, [25] graphene sheets, [26] nanoparticles, [27] and metal oxide/graphene hybrids. [28] However, to the best of our knowledge, microwave-assisted oxidation of ECNFs has not yet been documented, as noted in the comprehensive review of structure modification strategies for ECNFs by Inagaki et al [13] Common methods to control ECNF structures and properties include variation of carbonization conditions [15,20,21] and incorporation of functional ingredients such as Pd, [16] Si, [17] Sn, [18] and Pt [29] nanoparticles.…”

Microwave Preparation of Ag Nanoparticles for Chemiluminescence Enhancement

“…The resulting solution was diluted to 100 mL in a volumetric flask. In the same way, 0.020 g of K 3 [Fe(CN) 6 ] were dissolved in 5 mL of water; then, 4 mL of 3 wt % H 2 O 2 were added and the resulting mixture was also diluted to 100 mL. Synthesis of Ag NPs 25 mL of a 0.01 M AgNO 3 solution in ethyleneglycol were placed in a 150-mL beaker and 0.200 g of PVP was added slowly under magnetic stirring.…”

“…In this regard, synthesis using microwave irradiation is a good alternative to obtain Ag NPs in a short time. Microwave heating is more promising than thermal heating 3,4 since microwaves increase formation rates and homogenize Ag NPs sizes. 5 The thermal and non-thermal microwave effects on nanoparticle synthesis produce a significant heating rate acceleration and a more uniform temperature distribution, respectively.…”