Graphene
represents an attractive two-dimensional carbon-based
nanomaterial that holds great promise for applications such as electronics,
batteries, sensors, and composite materials. Recent work has demonstrated
that carbon-based nanomaterials are degradable/biodegradable, but
little work has been expended to identify products formed during the
degradation process. As these products may have toxicological implications
that could leach into the environment or the human body, insight into
the mechanism and structural elucidation remain important as carbon-based
nanomaterials become commercialized. We provide insight into a potential
mechanism of graphene oxide degradation via the photo-Fenton reaction.
We have determined that after 1 day of treatment intermediate oxidation
products (with MW 150–1000 Da) were generated. Upon longer
reaction times (i.e., days 2 and 3), these products were no longer
present in high abundance, and the system was dominated by graphene
quantum dots (GQDs). On the basis of FTIR, MS, and NMR data, potential
structures for these oxidation products, which consist of oxidized
polycyclic aromatic hydrocarbons, are proposed.
Summary
Dispersing metal nanoclusters on the oxide supports is attracting close attention in heterogeneous catalysis, but great challenges still lie in controlling the size and dispersion of nanoclusters due to the inevitable agglomeration. Here, we propose a sequential photochemical deposition strategy named “first store, and then release” to uniformly fabricate the size-controlling noble metal nanoclusters on semiconductor oxides. Using the typical semiconductor TiO
2
, the photoexcited electrons can be first stored as reduced species (e.g. Ti
3+
) under irradiation and the Ti
3+
species can optimize both the nucleation and growth processes in dark reaction, resulting in a uniform dispersing of various noble metals (Au, Pt, Ag etc.) with size diameters of ∼1 nm. The nanoclusters catalysts exhibited superior performance in catalytic oxidation of HCHO compared with that of nanoparticles. This work brings a new and useful strategy to construct size-controlling noble metals on the oxide supports for heterogeneous catalysis and the related fields.
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