We show that aqueous inks containing Au nanocrystals that were slightly modified with mercaptosuccinic acid (MSA, IUPAC name: sulfanylsuccinic acid) turn into conductive films after being cured in room-temperature air. Because of the highly hydrophilic nature of MSA, the nanoparticles maintain good dispersion in water. The conductive film exhibits an electrical resistivity in the order of 10(-5) Omega cm, and its temperature coefficient in the range from 290 to 20K was 7 x 10(-5)K(-1) without any post-treatments such as annealing, light irradiation, or solution-immersing processes.