UV light exposure of aqueous graphene oxide suspensions to promote their direct reduction, formation of graphene–metal nanoparticle hybrids and dye degradation

Self-propagating solar light reduction of graphite oxide in water

“…In water solutions, the self-reduction mechanism is influenced by the high temperature which increase the dissociation constant creating thus more reactive environment for the deoxygenation, i.e. dehydration of GO [40]. In this case, where UV light and no catalysts/sacrificing agent were employed, the self-photoreduction was attributed to both photothermal and photochemical reactions.…”

“…It can be noticed that two absorption maximums at ∼234 and ∼300 nm are present in the spectra of the initial GtO and the short-term irradiated (rGO-0.5 h) solutions. According to the literature [40,43], the absorption peak at 234 nm is originating from the -* transitions in small electronically conjugated domains, while the shoulder at 300 nm is attributed to n-* transitions in C O bonds. The two peaks are characteristic for the graphite oxide and with the increase of the irradiation time red shift and decrease of the peaks' intensity took place suggesting ongoing reduction process [40].…”

“…The UV-vis absorbance of the graphitic materials has been used for monitoring the reduction of GO [40,43,49]. Provided that the concentration of graphene oxide is constant, the change of the color from light yellow to black is considered as an indication for reduction of the graphene oxide.…”

“…[34]. Also, rGO have been obtained employing various types of irradiation such as microwave [35,36], far infrared [37], pulsed laser [38,39] irradiation, UV [40,41] and visible [42] light. Besides the green environmental approach, these techniques have the advantage of gradual, controllable reduction of graphene oxide films and suspensions to a desired level and, in case of light assisted reduction, masking/treating of selected areas for manufacture of flexible electronic devices.…”

High quality reduced graphene oxide flakes by fast kinetically controlled and clean indirect UV-induced radical reduction

“…Photoreduction of GO aqueous dispersions in the absence of photocatalysts, reducing agents and dispersants by intense UV irradiation (1 W cm −2 , 50 W short arc Hg bulb) has been studied. 23 After 15 h of irradiation, GO was partially reduced as evidenced from the change of the C/O ratio between 2.3 and 4.5. Irradiation of GO aqueous dispersions containing 20% methanol as a sacrificial reagent with UV or visible light leads to hydrogen generation, which was assigned to a water splitting reaction, photocatalyzed by GO as the semiconductor.…”