Photochemical stability and reactivity of graphene oxide

Abstract

The photoreactivity of graphene oxide (GO) suspensions was investigated with a double aim: i) to give insights into the previously reported photo-reduction process, which allows a partial elimination of the oxygen-containing groups from the 2D graphitic structure; ii) to explore the possible use of GO as photo-activator able to promote the photo-transformation/abatement of organic molecules. To reach these goals and clarify some peculiar aspects of the photochemistry of GO till now obscure or confuse, we synthesized and characterized stable GO suspensions which were then subjected to UV-Vis irradiation for prolonged times. GO underwent partial photoreduction with the release of gaseous molecules and soluble organic species (e.g. carboxylic acid).The mechanisms of photo-reduction occurring under air or N 2 are different, as assessed by the release in solution of diverse soluble molecules. In the presence of oxygen, at long irradiation time, a complete solubilization of the graphenic structures was observed. No difference in the nature and amount of released gases (principally CO 2 and CO) was observed in the oxic or anoxic conditions.The possible use of GO as photo-activator was evaluated by using phenol as probe molecule. GO revealed a double role of photo-activator and reagent in phenol degradation, as competition was assessed between GO self-transformation/reduction and phenol degradation. At prolonged irradiation time a marked reactivity of the photoformed species was observed and the complete degradation was achieved for both organic small molecules formed from GO and the phenol added as probe molecule.

In Situ Nanoreactors: Controllable Photoluminescent Carbon‐Rich Polymer Nanodots Derived from Fatty Acid under Photoirradiation

“…The color of PCPNs changed from light yellow to dark yellow under ambient light as photoreaction time increased. This behavior corresponded to the generation of additional conjugated structures (inset in Figure d) . Under excitation at 365 nm, the emission colors of PCPNs varied from blue (450 nm), cyan (460 nm) to green (560 and 460 nm) (Figure a,e).…”

“…This behavior corresponded to the generation of additional conjugated structures (inset in Figure 5d). [42] Under excitation at 365 nm, the emission colors of PCPNs varied from blue (450 nm), cyan (460 nm) to green (560 and 460 nm) (Figure 5a www.advancedsciencenews.com www.mrc-journal.de (Figure 5c). This phenomenon is rare reported and is different from that observed in previous studies, where dual emission always requires the addition of other fluorescent groups or materials.…”

Use of graphite oxide and/or thermally reduced graphite oxide for the removal of dyes from water

“…This behavior has been already assessed on the phenol degradation [14] and could be attributed to the different band-gap of the carbonaceous materials, as the band-gap of graphene derivatives can be tuned by modifying the degree of oxidation, with a change of the optical gap from 3.5 eV down to 1 eV by increasing the C/O ratio [28]; therefore, GOx shows typical band-gap of semiconductor.…”

“…Furthermore, it is well known that the band-gap of graphene derivatives, and therefore their photosensitizer properties, can be tuned by modifying the degree of oxidation, with a change of the optical gap from 3.5 eV down to 1 eV by increasing the C/O ratio. Likewise, the ability of graphite oxide (GOx) to act as photosensitizer when dispersed in aqueous solution or dispersed in a polymeric film has been very recently proved [13,14].…”

Ultra-sensitive carbon based molecular sensors

“…Electrical conductivity can be achieved by using a combination of light and chemical or photo-chemical method 123,124 . Using UV-irradiation on GO solution with TiO 2 suspensions, a stable solution of rGO can be obtained as the interaction between TiO 2 particles and the GO sheets prevent the agglomeration of the subsequent reduced GO 125 .…”