Simultaneous Phase- and Size-Controlled Synthesis of TiO₂ Nanorods via Non-Hydrolytic Sol−Gel Reaction of Syringe Pump Delivered Precursors

Abstract

The simultaneous phase- and size-controlled synthesis of TiO(2) nanorods was achieved via the non-hydrolytic sol-gel reaction of continuously delivered two titanium precursors using two separate syringe pumps. As the injection rate was decreased, the length of the TiO(2) nanorods was increased and their crystalline phase was simultaneously transformed from anatase to rutile. When the reaction was performed by injecting titanium precursors contained in two separate syringes into a hot oleylamine surfactant solution with an injection rate of 30 mL/h, anatase TiO(2) nanorods with dimensions of 6 nm (thickness) x 50 nm (length) were produced. When the injection rate was decreased to 2.5 mL/h, star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 200 nm and a small fraction of rod-shaped anatase TiO(2) nanorods with dimensions of 9 nm x 100 nm were synthesized. Pure star-shaped rutile TiO(2) nanorods with dimensions of 25 nm x 450 nm were synthesized when the injection rate was further decreased to 1.25 mL/h. The simultaneous phase transformation and length elongation of the TiO(2) nanorods were achieved. Under optimized reaction conditions, as much as 3.5 g of TiO(2) nanorods were produced. The TiO(2) nanorods were used to produce dye-sensitized solar cells, and the photoconversion efficiency of the mixture composed of star-shaped rutile TiO(2) nanorods and a small fraction of anatase nanorods were comparable to that of Degussa P-25.

Green sol–gel route for selective growth of 1D rutile N–TiO2: a highly active photocatalyst for H2 generation and environmental remediation under natural sunlight

“…64 The size and shape of a nanomaterial can be controlled by the kind of surfactant used and improved by its quantity. Various methods have been reported for synthesis of TiO 2 nanorods e.g., sol-gel, 65 hydrothermal, 66 template assisted synthesis, 51 and a magnetron sputtering method. 32 Different surface ligands, which bind selectively to a respective plane, can control nanorod formation.…”

Effect of Au nano-particles on TiO2 nanorod electrode in dye-sensitized solar cells

“…The crystal structure of TiO 2 also plays a factor in efficiency of DSSCs [24][25][26][27]. The difference between the conduction band levels of anatase and rutile forms, however due to the low difference between the conduction band levels of anatase and rutile, the higher diffusion coefficient of anatase play more important role for the efficient electron transport in anatase [28] and therefore, favors the use of pure anatase for DSSC applications [24].…”

“…The difference between the conduction band levels of anatase and rutile forms, however due to the low difference between the conduction band levels of anatase and rutile, the higher diffusion coefficient of anatase play more important role for the efficient electron transport in anatase [28] and therefore, favors the use of pure anatase for DSSC applications [24]. There are reports, however, that synergistic use of rutile and anatase polymorphs of TiO 2 nanoparticles could increase DSSC efficiency [24,25,27]. Such an effect is also observed in photocatalytic activity of anatase TiO 2 nano crystals, which significantly increases upon mixing with a portion of lesser active rutile nano crystals [29,30].…”

TiO 2 nanorod-based photoelectrodes for dye solar cells with tunable morphological features

“…[20,21] However, modest PCE values have been reported 5 to date, mainly because of the reduced internal surface area offered by photoanodes which employ nanorods or nanowires with a mean size larger than 100 nm [12,22,23] and/or the severe degradation of the original structural morphological features of the selected anisotropic TiO2 nanocrystals upon sintering. [11,15,16] Hence, the real challenge is to design and fabricate a nanostructured photoanode which simultaneously 10 has a large surface area to absorb more dye molecules, efficient light scattering ability and fast electron transport (as represented in the sketch shown in Figure 1). …”