Synthesis of Nanocrystalline Bismuth in Reverse Micelles

Abstract

Over the past decade, there has been a dramatic increase of interest in both the preparation and properties of nanocrystalline materials. This interest has been fueled by the unique properties that such materials possess when compared to bulk phases, 1 as well as the potential they hold for such varied applications as electronics, 2 catalysis, 3 and biological labeling. 4 The majority of the work in this field has focused on transition metal and semiconductor particles, with particular emphasis on gold 5 and II-VI compounds such as CdSe. 6 Although the formation of colloidal silicon 7 and germanium 8 nanoclusters has been studied, little work has been directed toward examining the preparation and fundamental properties of nanocrystalline main-group metals.Recent theoretical studies suggest that bismuth materials of reduced dimensions may exhibit enhanced thermoelectric properties at room temperature. 9 Quantum confinement has already been exploited to increase the thermoelectric figure of merit, ZT, for PbTe 10 quantum well superlattices and an even larger thermoelectric effect might be achieved with bismuth under such dimensionally restricted conditions. 9a The focus thus far has been on making these measurements on bismuth nanowires, 11 which possess diameters of 13-110 nm and lengths on the order of 10 µm.Despite the enormous potential of this material for thermoelectric applications, little work has been directed toward the solution synthesis of nanocrystalline bismuth clusters. To the best of our knowledge, only one report exists of such material being prepared as a stable colloid, 12 and these clusters were prepared at very low concentrations in an aqueous polymer, making the isolation of significant quantities of such material difficult. In addition, the size of the nanocrystals was determined to be 8 or 12 nm, sizes which are large when compared to the smallest diameters of noble metal nanoclusters. 5 Very recently, the synthesis of nanocrystalline bismuth using an in situ polymerization process was reported; 13 however, the resulting particles were even larger (20 nm) and were also suspended in a polymer matrix. Although this polymer coating protects the particles from oxidation, it once again makes the further manipulation and characterization of the product difficult. The focus of our effort has been the isolation of macroscopic quantities of bismuth nanocrystals with diameters below 10 nm that could be obtained in a more easily manipulated form.A variety of chemical methods have been reported in the literature for the preparation of noble metal nanoparticles, such as sonochemical reduction, 14 reduction in the presence of capping agents, 15 and reduction in inverse micelles. 16 We have recently examined a variety of reactions, in an attempt to prepare nanocrystalline bismuth clusters, 17 and have found difficulty in identifying a suitable capping agent. Traditional choices such as alkanethiols and TOPO have failed to provide proper control over both the nucleation and growth in our experiments with ...

Facile preparation of Bi nanoparticles by novel cathodic dispersion of bulk bismuth electrodes

“…3(a) and (b), respectively. Their broadened peaks [ 0 1 2 , 1 0 4 , 1 1 0 , 2 0 2 , 0 2 4 ] can be indexed to the Bi rhombohedral crystal structure, in agreement with that obtained by other methods [14,[18][19][20]. Moreover, the narrow and small diffraction peak [ 1 1 0 ] in Fig.…”

“…The former category includes vacuum melting and pressure injection [10], pulsed-laser deposition [11], flash evaporation [12], radio frequency magnetron sputtering [13] and dispersion in liquid paraffin [14]. And the latter one involves hydrothermal reduction [15], hydrothermal etching [16], ethylene glycol solvothermal reduction [17], reduction in reverse micelles/microemulsions by NaBH 4 [18,19], high-temperature reduction of organobismuth [20], electrodeposition [3,21], and so on. Besides, nano-Bi 2 O 3 was achieved by heat treatment [22,23] cal spray pyrolysis [24] of Bi(NO 3 ) 3 solution, and modified sol-gel procedure [25].…”

Shape Control of Single Crystalline Bismuth Nanostructures

“…[3][4][5] Most of the previous work has been focused on synthesis of onedimensional Bi nanowires using rigid inorganic or polymer templates. 6,7 Recently, there are a few reports on the synthesis of Bi nanoparticles by a variety of methods, such as inverse micelles, 8 radiolytic reduction in aqueous solution, 9 high temperature organic solution reduction, 10 and solution-based reduction. 11,12 However, the morphology of the Bi nanoparticles prepared by these methods are usually spherical.…”

Flame spray synthesis under a non-oxidizing atmosphere: Preparation of metallic bismuth nanoparticles and nanocrystalline bulk bismuth metal

“…The synthesis of bismuth nanoparticles by vapor flow condensation (Wegner et al, 2002) resulted in products of high purity but was characterized by a limited production rate and product loss by wall deposition. Different liquid phase chemical reduction methods were applied at high yield for the synthesis of bismuth nanoparticles (Foos et al, 2000;Fang et al, 2000Fang et al, , 2001Balan et al, 2004;Dellinger & Braun, 2004;Fu et al, 2005) but product contamination from remaining surfactants and solvent limited the accessible product purity. Similarly, bismuth nanoparticles prepared by the dispersion of liquid bismuth in an inert solvent (Zhao et al, 2004) resulted in about 9 wt% organic residue.…”