In-situ synthesis of gold nanoparticles in nitrogen-doped titania nanosheets via layer-by-layer assembly method

Self-assembled multilayer films of nitrogen-doped exfoliated titania nanosheets and Au nanoparticles (NP) were fabricated via layer-by-layer assembly method followed by solar irradiation treatment. Au NP were found to form by in-situ reduction and thus disperse homogeneously between nitrogen-doped titania nanosheet galleries and the composite films of disordered structure, as confirmed by transmission electron microscope and X-ray diffractometer. Ultraviolet–visible absorption spectra in the multilayer buildup process indicated that plasmon resonance of the multilayer films was enhanced and red-shifted due to the changes of surrounding medium. It is found that nearly equal amounts of nanosheets were assembled and golds were reduced in each deposition cycle. X-ray photoelectron spectroscopy observation revealed that the interaction between the two components affects the distribution of electrons of Au, which causes the negative shift of the binding energy of Au NP. Compared with pure nitrogen-doped (N-doped) titania nanosheets, the higher hydroxyl density on the surface of such multilayer films was confirmed to be beneficial to efficiently separating the photogenerated electrons and holes, and as a result enhancing their photocatalytic activities.

► Layer-by-layer assembly method and photo-reduction.
► Au nanoparticles (NP) are formed between nitrogen-doped titania nanosheets.
► Plasmon resonance of Au NP is red-shifted in nitrogen-doped titania nanosheets.
► High hydroxyl density is found on the surface of composite multilayer films.