In Situ Observation of Enhanced Photoinduced Charge Separation in a Gold Nanoparticle Assembly Immobilized on TiO2

• Published in: ChemistrySelect (Weinheim) 2016-11, Vol.1 (18), p.5666-5670
• Main Authors: Harada, Hirofumi, Onoda, Akira, Moriguchi, Shiho, Hayashi, Takashi
• Format: Article
• Language: English
• Subjects: biotin−streptavidin interaction; gold nanoparticle; Kelvin force microscopy; photoinduced charge separation; titanium dioxide
• ISSN: 2365-6549; 2365-6549
• DOI: 10.1002/slct.201601383

Photoinduced charge separation on a hybrid titanium dioxide (TiO2) surface with a gold nanoparticle (AuNP) assembly immobilized via a biotin‐streptavidin interaction was visualized by Kelvin force microscopy (KFM). Biotinylated AuNP (Biot‐AuNP) with a diameter of ca. 15 nm was assembled using streptavidin (STV) and the AuNP assembly was immobilized on a TiO2 surface modified with 1‐(3‐aminopropyl)silatrane. KFM reveals that the local contact potential difference (CPD) of dispersed AuNP, which is −17 ± 4.2 mV in the dark, undergoes a negative shift of −46 ± 3.0 mV upon UV‐irradiation (λ=240‐300 nm). In contrast, the AuNP assembly on the TiO2 surface exhibits a greater negative shift of −58 ± 6.0 mV of the CPD, although the CPD value of −16 ± 5.8 mV in the dark is similar to that of the dispersed AuNP. KFM visualization demonstrates that assembly of the AuNP on the TiO2 surface contributes to efficient storage of the negative charge generated by excited electrons in TiO2 during photoinduced charge separation. Enhanced photo–induced charge separation by AuNP assembling: Gold nanoparticles assembled using biotin−streptavidin was immobilized on a TiO2 surface. In situ Kelvin force microscopy revealed that gold nanoparticle assembly exhibits more negative value in contact potential difference that corresponds with the surface potential relative to the dispersed gold nanoparticle, thereby suggesting efficient photo‐induced charge separation.