Fast and efficient graphene oxide (GO) reduction by using a lab-made UV photoreactor

The graphene oxide (GO) consists of an oxidized graphene layer decorated with hydroxyl, epoxide, carbonyl and carboxylic groups. The oxygen groups in the GO structure confer to it an insulator property [1]. To enhance its conductivity, the oxygen groups must be removed by a process of reduction, recovering the sp2 domains. The most common chemical method used for GO reduction utilizes sodium borohydride or hydrazine, which are well known by their high reactivity and toxicity. In order to overcome these drawback associate to use of strong reducing agents, the photochemical reduction methods are very attractive, because they are low time consuming, produce low amounts of chemical residues and does not insert functional groups into the graphene structures [2]. In this work, an UV photoreactor was fabricated and its performance was evaluated for graphene oxide reducing. The photoreactor utilizes a 250 W high-pressure mercury lamp as source of UV radiation and four quartz tubes of 10 mL with 10-mm thickness to put the samples. Aliquots of 4 mL of 1mg L-1 GO dispersions in DI water were UV irradiated for 15, 30, 45 and 60 minutes. The irradiation of the GO dispersion leaded to darkening of the color solution (Fig. 1B) and to significant changes in its absorption spectrum (Fig.1C). The position of the band with higher intensity depends on the degree of oxidation of the GO. The results show that the irradiation time of the GO dispersion leads to a shift of the maximum band from 229 nm to 261 nm until 30 min exposure solution, due to conversion of the oxidized material to its reduced form resulting of the increase in the extent of the aromatic clusters of sp2-hybridized carbon.