Morphology Control of Single Crystalline Rutile TiO₂Nanowires

Abstract

Nano-scaled metal oxides have been attractive materials for sensors, photocatalysis, and dye-sensitization for solar cells. We report the controlled synthesis and characterization of single crystalline TiO2 nanowires via a catalyst-assisted vapor-liquid-solid (VLS) and vapor-solid (VS) growth mechanism during TiO powder evaporation. Scanning electron microscope (SEM) and transmission electron microscope (TEM) studies show that as grown TiO2 materials are one-dimensional (1D) nano-structures with a single crystalline rutile phase. Also, energy-dispersive X-ray (EDX) spectroscopy indicates the presence of both Ti and O with a Ti/O atomic ratio of 1 to 2. Various morphologies of single crystalline TiO2 nano-structures are realized by controlling the growth temperature and flow rate of carrier gas. Large amount of reactant evaporated at high temperature and high flow rate is crucial to the morphology change of TiO2 nanowire.

Growing TiO2 nanowires by solid–liquid–solid mechanism including two factors (Ti and O)

“…Using Ni catalyst on Ti substrate and TiO 2 powder as source, Park et al [18] claimed that their mechanism is VLS. Baik et al also did the same experiment and argued that ''although the presence of a small catalyst particle implies a VLS growth mechanism, number of observations suggest that the mechanism differs somewhat from the VLS process as it is normally understood.…”

“…In second method (2), observing gold droplets over nanowires, Mortezaali et al [15] and Park et al [18] have determined the growth mechanism of their method as VLS (2.1). They also considered the Ti substrate as Ti vapor source.…”

“…The source could be obtained by a chemical reaction, say carbothermal reduction of titanium in the presence of carbon [11][12][13] or via Ti, or TiO powder evaporation [8][9][10][17][18][19][20][21]. In terms of existence or absence of catalyst, the growth mechanisms proposed for this method are in two groups: (1.1) vaporsolid (VS) (1.2) and vapor-liquid-solid (VLS).…”

“…There are many reports on the synthesis of TiO 2 nanowires [14][15][16][17][18][19][20][21][22][23][24][25][26][27] where have used first or second methods and all of them have common feature, namely presence of Ti layer on substrate before nanostructures growth. These processes are indicated by star symbol in Fig.…”

Fabrication of TiO2Nanowires Using Vapor-Liquid-Solid Process for the Osseointegration

“…There are previous studies of nanowire growth using Vapor-Liquid-Solid (VLS) process with metal catalyst [13][14][15][16][17][18][19][20]. Generally, it is reported that TiO2 nanowire grows at 800∼900 o C using VLS process.…”