Determination of Schottky barrier height and enhanced photoelectron generation in novel plasmonic immobilized multisegmented (Au/TiO2) nanorod arrays (NRAs) suitable for solar energy conversion applicationsElectronic supplementary information (ESI) available: Fig. S1: (a) The extinction spectra of Au NRs with various AR. (b) Linear relationships between λmax and AR for Au NRs. Fig. S2: The extinction spectra of Au and multisegmented Au/TiO2 NR with the same AR. Fig. S3: (a) Hexagonally arranged

• Main Authors: Arshad, Muhammad Shahid, Trafela, Špela, Ro man, Kristina u ek, Kova, Janez, Djinovi, Petar, Pintar, Albin
• Format: Journal Article
• Published: 19.10.2017
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c7tc02633a

For the past several years, different strategies have been developed to design and fabricate Au/TiO 2 nanostructures for solar-light-driven applications. Owing to the localized surface plasmon resonance properties of Au, Au/TiO 2 nanostructures display extraordinary features including enhanced visible light harvesting, hot electron injection, and Schottky barriers to minimize back electron transfer; these factors maximize device performance. In this report, novel free-standing immobilized TiO 2 and multisegmented Au/TiO 2 nanorod arrays (NRAs) were successfully fabricated with a template-assisted electrodeposition technique to examine several physical phenomena like the Schottky barrier height (SBH), photoelectron generation, as well as the mechanism of hot electron transfer. Pristine TiO 2 NRAs exhibit amorphous behaviour with strong absorption under UV-light; however, for Au/TiO 2 NRAs, transverse and longitudinal plasmon modes were observed under visible light, which correlates closely with our theoretical predictions. The reduced binding energy of Au 4f 7/2 and concurrent increase in the Ti 3+ -O species observed with X-ray photoelectron spectroscopy (XPS) is direct evidence for charge transfer from oxygen vacancies in TiO 2 to Au segments. XPS analysis on valence band maxima (VBM) helps us to determine an SBH of 0.23 eV at the interface between the Au and TiO 2 segments. The low value of SBH is attributed to the high density of oxygen vacancies in TiO 2 due to the amorphous structure, and is very close to the theoretical literature value. Photoelectrochemical (PEC) measurements showed 4× improved photoelectron generation in Au/TiO 2 NRAs in comparison to pristine TiO 2 NRAs. This improvement is attributed to the hot electron injection, plasmonic resonance energy transfer (PRET) and efficient charge separation and migration due to the small SBH at the interface of Au and TiO 2 . Our results concluded that novel immobilized multisegmented (Au/TiO 2 ) NRAs have great potential for solar-light-driven applications. We have determined the Schottky barrier height (0.23 eV) and efficient photoelectron generation in novel multisegmented Au/TiO 2 nanorod arrays.