Preparation of Cadmium Sulfide Nanowire Arrays in Anodic Aluminum Oxide Templates

Abstract

The ordered structures of nanomaterials have been attracting more and more attention recently due to their unusual physical properties. [1][2][3][4] There are mainly two routes to fabricate such structures. One method is preparing nanomaterials and then organizing them. 5 The two-and three-dimensional ordered structures of CdSe, 6 Ag 2 S, 7 Au, 8 Ag, 4,9 Pd, 10 and Co 11 have been fabricated through this method. The other method is the direct preparation of ordered structures from molecular or atomic precursors either physically or chemically. The solid-state methods for the fabrication of nanomaterials, such as physical and chemical vapor deposition (PVD 12 and CVD 1,13 ), molecular beam epitaxy (MBE), 14 and manipulation through scanning tunnel microscopy (STM), 15 often need harsh conditions, expensive equipment, and state-of-the-art techniques. 16 However, the solution chemistry methods can avoid the above limitations. 16 And if some ordered systems are adopted as templates in the synthesis process, the ordered structure of nanomaterials can be obtained. Braun et al. 17 reported the synthesis of semiconductor-organic superlattices based on cadmium sulfide and cadmium selenide templated by hexagonal liquid crystals. We have prepared the parallel nanowires of CdS 18 and ZnS 19 with the diameter as small as 3 nm templated, also by hexagonal liquid crystals. These kinds of template are known as "soft" ones. The "hard" templates of porous polymer membranes and anodic aluminum oxides (AAO) are widely applied in the synthesis of nanowires and nanoparticles. 20,21 The AAO template takes a great advantage of arranging cylindrical pores, of uniform diameter, in a hexagonal array. 20 This greatly benefits the fabrication of ordered nanowire arrays. The Martin group has reported the synthesis of nanoparticles, nanowires, and nanotubules of metals, semiconductors, and polymers by electrodeposition, 22 sol-gel deposition, 23 and polymerization 24 in AAO membranes. Routkevitch fabricated CdS nanowire arrays by electrochemical deposition into an AAO template. 25 In this paper, we study the synthesis of CdS nanowire arrays with a solution reaction method by injecting the reactants into the pores of the AAO membrane.Although Martin et al. 23 prepared several kinds of metal oxide nanofibrils and nanotubes through immersion of the AAO membranes into the corresponding sols and then calcination, there are few other reports about the synthesis of one-dimensional nanostructures in AAO membranes in aqueous solutions with methods other than electrodeposition. The reason usually is that the in situ formed nanoparticles hinder the dispersion of reactants into the inner part of the pores. We tried to prepare CdS nanowires in AAO with aqueous solutions of Cd 2+ and H 2 S or Na 2 S as the reactants, but only low aspect ratio nanoparticles were obtained. We adopted thioacetamide (TAA) as the precursor of H 2 S in this research. It can gradually liberate H 2 S in aqueous solution, and react with Cd 2+ slowly. It effectively eliminat...

Advances in Thermoelectric Energy Conversion Nanocomposites

“…Prior literature has suggested that the fabrication of PbS, CuS and CdS nanorods can occur either by electrodeposition or injection of reactants within the channel pores of either anodic aluminum oxide or mesoporous silica templates. Parallel nanowires of CdS and ZnS ) with the diameter as small as 3 nm templated was another example synthesized by hexagonal liquid crystals (Li et al, 1999).…”

TiO₂ Nanorods Prepared from Anodic Aluminum Oxide Template and their Applications in Dye-Sensitized Solar Cells

“…Ordered TiO 2 nanorods or nanowires are highly interesting candidates to reach this goal [5][6][7]. There have been numerous methods to grow up TiO 2 nanostructures, including sol-gel process, electrospinning, and anodization of Ti metal [7,8]. However, these methods have limitations in synthesizing highly ordered structures such as uniform TiO 2 nanorods or nanowires with precisely control of dimension and geometry.…”

“…AAO template method is suitable to prepare TiO 2 nanorods and nanowires with uniformly ordered structure [10]. By changing a hole diameter and thickness of AAO or infiltration depth of precursor into AAO, size and aspect ratio of 1-D nanomaterials can be easily controlled [8,[10][11]. The aim of this work was to control the fabrication of TiO 2 nanorods by AAO template and apply the nanorods in DSSC applications.…”

Preparation and Characterization of Ni or Co/Cu Multilayer Nanowires

“…The shape and size of nanowires synthesized by template method can be confined with the pores of the template. 5 However, these nanowires often loss their high coercivity due to demagnetization by neighbouring magnetic domains. In order to overcome this drawback, the non-magnetic layer (NM) is inserted between each ferromagnetic layer (FM), to form FM/NM/FM… periodic structure.…”