Photoreduction of graphene oxide with polyoxometalate clusters and its enhanced saturable absorption

• Graphene oxide has been successfully photoreduced by polyoxometalates.
• The influence of the energy level of polyoxometalates on their photoreduction capabilities has been elucidated.
• The saturable absorption of the reduced graphene oxide has been studied by Z-scan method.

We investigated the photocatalytic abilities of three Keggin-type polyoxometalate (POM) clusters, H3PW12O40 (PW), H4SiW12O40 (SiW), and H3PMo12O40 (PMo) to reduce graphene oxide (GO) under UV-irradiation in water. UV–vis absorption and X-ray photoelectron spectroscopy were performed and show that PW and SiW can photoreduce GO effectively, in contrast to PMo. We conclude that the LUMO levels of POMs should be located energetically above the work function of GO to enable electron transfer from POM to GO. We also investigated the saturable absorption of GO and reduced GO by means of z-scan experiments at 532 nm. The POM-assisted photoreduction of GO can greatly enhance the saturable absorber properties of GO, which appears useful for modelocking in ultrafast laser systems.

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