Layer-by-layer assembly of gold nanoparticles with titania nanosheets: control of plasmon resonance and photovoltaic properties

Layer-by-layer assembled multilayer films composed of gold nanoparticles (Au NPs) and titania nanosheets were constructed on a glass or ITO substrate in an arbitrary layering order. Coverage of Au NPs with 1 to 3 layers of titania nanosheets enhances their plasmon resonance-based absorption and photocurrents. Absorption can be improved further by alternate stacking of Au NPs and titania nanosheets. Plasmon resonance of the multilayer can be enhanced and redshifted by interlayer plasmon coupling via a single intervening nanosheet layer, whereas the coupling can be suppressed, if necessary, by two or more layers of nanosheets. Direction of the photocurrents can also be switched; annealed ITO/titania nanosheet/Au NP electrodes exhibit anodic photocurrents and annealed ITO/Au NP/titania nanosheet electrodes exhibit cathodic photocurrents.