Abstract
Titanium dioxide (TiO2) is a key component of diverse optical and electronic applications that exploit its exceptional material properties. In particular, the use of TiO2 in its single-crystalline phase can offer substantial advantages over its amorphous and polycrystalline phases for existing and yet-to-be-developed applications. However, the implementation of single-crystal TiO2 has been hampered by challenges in its fabrication and subsequent surface functionalization. Here, we introduce a novel top-down approach that allows for batch fabrication of uniform high-aspect-ratio single-crystal TiO2 nanostructures with targeted sidewall profiles. We complement our fabrication approach with a functionalization strategy that achieves dense, uniform, and area-selective coating with a variety of biomolecules. This allows us to fabricate single-crystal rutile TiO2 nanocylinders tethered with individual DNA molecules for use as force- and torque-transducers in an optical torque wrench. These developments provide the means for increased exploitation of the superior material properties of single-crystal TiO2 at the nanoscale.
Highlights
Micro- and nanostructures based on titanium dioxide (TiO2) have been utilized in numerous applications that exploit the unique properties of this material (Fig. S1†)
We focus our efforts on the rutile polymorph of single-crystal TiO2 (100), in order to harness its exceptionally large optical birefringence and precisely oriented optic axis for effective torque transfer (ESI Methods†) in an optical torque wrench (OTW).[20]
We found that non-coated TiO2 nanocylinders aggregate substantially over time in deionized (DI) water, in contrast to what occurs in physiological phosphate buffered saline (PBS) solution at a similar pH (7.4)
Summary
Micro- and nanostructures based on titanium dioxide (TiO2) have been utilized in numerous applications that exploit the unique properties of this material (Fig. S1†). The higher carrier mobility of single-crystal TiO2 renders it a promising material for transistors and (bio)sensors[14] and may enhance the efficiency of dye-sensitized solar cells.[15] optical waveguides and photonic crystals composed of single-crystal TiO2 16,17 are expected, due to their highly ordered atomic structures, to exhibit improved light transmission and nonlinear responses.[18,19] Lastly, the single-crystal rutile polymorph of TiO2 has an exceptionally large optical birefringence, which makes it an excellent candidate for incorporation into torque transducers for e.g. singlemolecule spectroscopy.[20]
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