Premade Nanoparticle Films for the Synthesis of Vertically Aligned Carbon Nanotubes

Abstract

Carbon nanotubes (CNTs) offer unique properties that have the potential to address multiple issues in industry and material sciences. Although many synthesis methods have been developed, it remains difficult to control CNT characteristics. Here, with the goal of achieving such control, we report a bottom-up process for CNT synthesis in which monolayers of premade aluminum oxide (Al2O3) and iron oxide (Fe3O4) nanoparticles were anchored on a flat silicon oxide (SiO2) substrate. The nanoparticle dispersion and monolayer assembly of the oleic-acid-stabilized Al2O3 nanoparticles were achieved using 11-phosphonoundecanoic acid as a bifunctional linker, with the phosphonate group binding to the SiO2 substrate and the terminal carboxylate group binding to the nanoparticles. Subsequently, an Fe3O4 monolayer was formed over the Al2O3 layer using the same approach. The assembled Al2O3 and Fe3O4 nanoparticle monolayers acted as a catalyst support and catalyst, respectively, for the growth of vertically aligned CNTs. The CNTs were successfully synthesized using a conventional atmospheric pressure-chemical vapor deposition method with acetylene as the carbon precursor. Thus, these nanoparticle films provide a facile and inexpensive approach for producing homogenous CNTs.

Synthesis of bimetallic aluminum–iron oxide nanorice, nanocubes and nanospheres

“…S1B, ESI†), which correspond to symmetric and asymmetric COO–Al stretching. 41–44 Similarly, the two additional bands observed at 1600 cm −1 and 1531 cm −1 for iron oleate correspond to asymmetric and symmetric COO–Fe stretching. 45 The band at 1712 cm −1 in the FTIR spectra (Fig.…”

“…7C1). The peaks marked with a star (*) in 43,56,57 The effect of annealing at 1100 1C for 4 h on the bimetallic Al 2 O 3 -Fe 2 O 3 nanoparticles was also characterized using TEM (Fig. S5, ESI †).…”

“…Hexagonal FeO x nanoparticles have previously been synthesized from iron oleate precursors using 1-ocadecene and 1-hexadecene as solvents. 24,43 It has been reported that the presence of alcoholic solvents and intermediate species leads to the nucleation of crystal facets, which determines the nanoparticle shape. 23,25 In our study, the shape evolution of the bimetallic AlO x –Fe 2 O 3 nanoparticles mainly depended on the iron oleate precursor concentration and the capping agent to precursor ratio in the reaction mixture.…”

“…These phase transitions from amorphous AlO x to α-Al 2 O 3 and α-Al 2 O 3 to α-Al 2 O 3 have been addressed previously. 43,56,57…”

“…Aluminum oleate was prepared by refluxing AlCl 3 (5 g) and sodium oleate (20 g) in a mixture of hexane (70 mL), ethanol (40 mL), and H 2 O (30 mL) for 4 h at 70 1C with continuous stirring. [41][42][43] AlCl 3 was slowly dissolved in the solvent mixture to avoid a violent reaction between AlCl 3 and water, which produces HCl fumes. After the reaction, a transparent layer of aluminum oleate formed on top of the reaction mixture.…”