Graphene oxide (GO) dispersed nanofluids were first explored to be used as working fluids for direct absorption solar collectors. The stability, optical absorption property, thermal-physical property and photo-thermal conversion performance of the GO/water nanofluids with different mass fractions of GO were symmetrically investigated. The sedimentation experiment and Zeta potential (1) analysis showed that the GO/water nanofluids not only possess excellent. long-term stability but also keep stable at elevated temperatures. A remarkable enhancement in optical absorption property was observed for the GO/water nanofluids due to the dispersion of GO into water. The GO/water nanofluids exhibited an obvious improvement in thermal conductivity as compared with water. The photo-thermal conversion performance of the GO/water nanofluids were higher than that of water, and the highest efficiency was achieved by the one containing 0.02% of GO, which was 97.45% at 30 degrees C and 48.92% at 80 degrees C. The GO/water nanofluids with excellent dispersion stability, good optical absorption property and photo thermal performance show great promise for use as the working fluids in low temperature direct absorption solar collectors. (C) 2017 Elsevier Ltd. All rights reserved.