Laser irradiation at 532 nm has been used to produce reduced graphene oxide (rGO) colloids. Photoluminescence measurements showed a well-rendered gradual shift of the emission maximum to lower wavelengths upon increasing the irradiation time, until reaching the limit value of 450 nm. It has been also found that the reduction is mainly due to the decrease of oxidized moieties, as evidenced by infrared absorption and X-ray photoelectron spectroscopy data. Moreover, the freshly reduced sheets (rGO) show a progressive hydrophobicity which leads to a different interaction with previously prepared neat SiO2 surfaces. ζ-Potential measurements in solution support these findings.