Tuning Intercrystalline Void-like Defects in Nanowire Clusters to TiO2 Quantum Wires with Enhanced Photocatalytic Performance

Abstract

Enthalpically driven dopant induced defects generated from the interaction of bulk titanium oxide and structure directed agents composed of charge separated ions have important consequences in directing interfacial energies in organometallic semiconductors. Such external factors imposed by the chemical environment at contrasting surfaces generated at bulk catalytic interfaces are capable of introducing lattice defects at the structural and morphological level. Here, we demonstrate that post-modification of primary defect sites of TiO2 nanowires from the bulk state in a group reactive ionic liquid (IL) environment has the potential to structurally redirect defect states altering both the order of dimensionality and electronic properties. This is demonstrated by the fabrication of surface modified quantum wires (SMoQWs) from zero-dimensional nanoclustered nanowires (NCNWs) formed under moderate temperature annealing and ambient pressure. This approach demonstrates that structural distortions that exist within crystal lattices of the NCNWs can generate new functionalities at non-equilibrium sites by modulating the mixed Ti3+/Ti4+ valence signature. The concentration of displaced oxygen molecules and their consumption have a direct impact on vacancy growth patterns, increasing the Ti3+/Ti4+ ratio at crystal sites when mediated by nitrogen rich species. Evidence shows that the growth confinement of TiO2 is locked in a one-dimensional geometrical configuration formed by a complex of caged Ti-porphyrin clusters bridged by polyphenylquinoxiline linkers formed via O–Ti–N bonding. The importance of charge carrier separation and charge mobility was demonstrated by spatial reordering of functionalized TiO2 quantum wires via dye adsorption (N719). SMoQWs demonstrate superior photocatalytic degradation properties to the NCNWs, enhancing their utility in DSSC device applications.